The Peter Attia Drive - #114 - Eileen White, Ph.D.： Autophagy, fasting, and promising new cancer therapies

00:00:00.000 Hey everyone, welcome to the drive podcast. I'm your host, Peter Atiyah. This podcast,

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00:00:41.720 head over to peteratiyahmd.com forward slash subscribe. Now, without further delay,

00:00:47.740 here's today's episode. I guess this week is professor Eileen White. Eileen is the deputy

00:00:54.840 director and chief scientific officer, along with the associate director for basic research.

00:00:58.880 And the co-leader of the cancer metabolism and growth research program at Rutgers University

00:01:04.220 Cancer Institute in New Jersey. She received her bachelor's degree from RPI and her PhD from SUNY

00:01:10.200 and Stony Brook and did her postdoc with Bruce Stillman at Cold Spring Harbor Laboratory. Eileen's

00:01:15.300 early work focused on apoptosis, but it was doing some of the work there that she stumbled upon

00:01:21.020 autophagy. And that is the focus of our discussion today. Now, if you're even remotely familiar with this

00:01:27.320 podcast, you'll certainly know that the concept of autophagy has come up on so many previous

00:01:32.060 episodes. It is a fundamental pillar of health and maintenance of health. We talk a lot about it in

00:01:39.160 the context of fasting in particular. I have wanted to sit down with Eileen for a really long time,

00:01:45.120 and I don't think this conversation disappoints, although we certainly could have gone longer.

00:01:49.300 In this discussion, we talk about Eileen's career and how it morphed from studying apoptosis into

00:01:56.260 autophagy. We go into describing the regulation of autophagy, both metabolically and otherwise.

00:02:03.640 And then we spend a lot of time talking about the role autophagy plays in both the prevention of

00:02:09.420 disease and also the treatment of disease. And I think this is where it gets really interesting,

00:02:14.400 especially around cancer. And I think that that's potentially one of the most confusing

00:02:18.380 aspects of the entire discussion on autophagy. And that's actually one of the reasons I really

00:02:23.180 wanted to talk to Eileen was to better understand something that at the surface seems confusing to

00:02:29.440 me, which is that autophagy seems to very clearly protect a person or an organism from getting cancer.

00:02:37.420 Yet once someone has cancer, it appears that autophagy may disproportionately benefit the cancer

00:02:43.880 cell versus the non-cancer cell. So we tease this idea apart along with talking

00:02:48.340 about the amazing work that her lab has done to demonstrate the importance of autophagy in

00:02:53.980 preventing Alzheimer's disease and neurodegeneration, along with the benefits of metabolic health.

00:02:58.940 And of course, we do talk about the age old question that many of you have heard me

00:03:02.520 go on and on about, which is how do we delineate and understand the dosing and frequency of fasting as

00:03:10.100 a tool? In other words, when I talk about doing a fast of three days every month versus seven days,

00:03:15.060 a quarter versus five days, a quarter, how could we possibly get a handle on what the ideal strategy

00:03:21.180 is? And so we talk a lot about that as well. And I'm actually quite hopeful that from this

00:03:25.580 discussion comes some research that can shed light on that. So without further delay, I hope you enjoy

00:03:31.820 my discussion on autophagy with Eileen White.

00:03:41.040 Eileen, thank you so much for extending your trip in San Diego for a day to come and make time to talk

00:03:46.880 with me about this stuff today. Oh, it's my pleasure. I'm looking forward to it.

00:03:50.560 I don't know if you remember this, by the way, but David Sabatini introduced us a few years ago. Do you remember?

00:03:55.560 I do. I still have my notes from that phone call five years ago. I took about 20, maybe not 20,

00:04:02.440 that's an exaggeration, maybe 10 pages of notes in my journal and probably have gone back to those

00:04:08.380 a dozen times in the last five or six years. So I always appreciate it when people just pick up the

00:04:14.060 phone and talk to total strangers for no reason. So that's greatly appreciated.

00:04:17.780 Well, you were excited about the science. And so nerds like me like to talk about science.

00:04:24.080 Well, let's actually start from there. Tell me where your interest in science came from.

00:04:29.160 Was it something that was always in you from a young age? Were you just naturally curious?

00:04:33.300 Yeah, I've been asked that question many times before. I come from a family where there was an

00:04:39.560 interest in science. My mother was a elementary school teacher and my father was a lawyer, but he

00:04:47.340 always wanted to be in science. And all of our discussions were related a lot to new scientific

00:04:58.000 discovery. So from an early age, I was introduced to science, which was probably unusual.

00:05:04.420 And I then went to college and majored in science and biology and continued from there. And I decided

00:05:14.300 when I was an undergraduate, I wanted to get a PhD in biology. And I was very fortunate to

00:05:21.100 go into graduate school in the department led by Dr. Arnie Levine, who discovered P53. And that was an

00:05:31.100 inspirational experience because he has got scientific insight that's absolutely incredible.

00:05:37.360 And then I went on to Quiltspring Harbor Lab, where I was a postdoc with Bruce Stillman.

00:05:43.760 And again, another incredible scientist, and it was an incredible scientific environment.

00:05:49.980 There were a whole cadre of investigators there that were making major contributions in the field of

00:05:58.260 cancer at the time. And it was just a very thrilling experience to be in an environment where

00:06:04.040 once a week, there was some fabulous discovery and everyone was excited about it. There were even,

00:06:10.400 I think, two Nobel Prizes awarded while I was there. And I joined the faculty at Cold Spring Harbor

00:06:16.120 after that. And then I moved on to Rutgers. And I had the fortunate experience of building a cancer

00:06:23.880 center. So when I went to Rutgers to be on the faculty, there was no cancer center. But shortly after I

00:06:30.660 arrived, they hired a cancer center director, Bill Height from Yale. And I joined him to help build what's

00:06:39.960 now the Rutgers Cancer Center or the Rutgers Cancer Institute, which went from nothing to now there are

00:06:47.500 multiple buildings, there are 11 hospitals in our health system. We have 240 something members of the

00:06:57.700 Rutgers Cancer Institute. And we have, we're a consortium cancer center with Princeton University.

00:07:03.440 And so it was very thrilling for me to not only have maintain my scientific interest by running a

00:07:10.740 research lab, but also help expand and grow something from nothing, where now we're treating large numbers of

00:07:20.000 patients in standard of care and clinical trials and making large discoveries and moving cancer

00:07:28.460 treatment, advancing cancer treatment as fast as we can.

00:07:32.780 And how many years have you been at Rutgers?

00:07:34.420 I joined there in 1990. So I've been there for a long time, but I moved about 12 years ago. I moved from

00:07:41.280 one research building to be physically in the cancer center where I could be more directly helpful.

00:07:49.260 So where in your journey did autophagy pique your curiosity?

00:07:56.040 It was purely serendipity. So this goes back to when I was a postdoc with Bruce Stillman at Cold

00:08:02.900 Spring Harbor. I was given an oncogene to study. That time they had just sequenced the adenovirus genome.

00:08:10.800 They knew what genes caused cancer in the virus. I was given one of those genes and said,

00:08:18.080 figure out what it does. And that was a dream project for a postdoc. And what I found was that

00:08:23.940 this gene was a viral homologue of BCL2. BCL2 is a gene, it's a human oncogene, and it functions by

00:08:33.660 blocking apoptosis or programmed cell death. And so that was transformative to me and took other people

00:08:41.660 a while to realize the importance of that, that one novel function of cancer is to evade cell death.

00:08:51.120 That field grew. We and others contributed cloning the other genes that regulated apoptosis. We figured

00:08:59.680 out how it all, the mechanism by which it worked. And the pharmaceutical industry started developing

00:09:06.580 inhibitors of BCL2 to promote apoptosis and cancer. And that was the ultimate goal, was to make tumor

00:09:15.140 cells die and have a drug that will do that. And once that happened, the field of apoptosis, I think,

00:09:22.940 sort of, we accomplished what we wanted to accomplish. We understood everything. And that led to the

00:09:30.480 development of the first of many drugs that were in clinical trials. And in fact, my lab is still

00:09:36.980 involved with taking those drugs and putting them in patients and optimizing their use in solid tumors.

00:09:44.280 So while the field of apoptosis matured to the point where things were being translated,

00:09:54.280 we made a serendipitous discovery. We had engineered tumor cells to

00:10:00.200 be unable to undergo apoptosis. They were refractory to being able to commit suicide.

00:10:08.960 Can we pause for a second there, Eileen? And just let's explain to folks exactly how apoptosis works,

00:10:13.460 because shortly we're going to obviously contrast this with autophagy. They have common threads,

00:10:18.300 but they're different. So let's go down the path of what does it take to get a cell to undergo

00:10:24.100 programmed suicide? So there's a family of proteins called the BCL2 family. They come in different

00:10:31.440 flavors. There are the BCL2-like proteins, which inhibit apoptosis, so they keep tumor cells alive.

00:10:40.100 And BCL2 is a prototypical member of that family and is upregulated and amplified and translocated in

00:10:49.860 many cancers to do exactly that. And are antagonizers of BCL2 and its related proteins. These are called the

00:11:00.620 BH3-only proteins. And they are often activated to inhibit BCL2 to trigger apoptosis. And then there's

00:11:11.860 the core apoptotic machinery that triggers apoptosis. And this is backs and back. They reside in the

00:11:19.940 mitochondrial membrane. And when they're triggered to undergo apoptosis, they oligomerize and poke holes

00:11:28.840 in the mitochondrial outer membrane that releases proteins that activate proteases to grade the cell.

00:11:36.800 And BCL2 and BCLXL, all the anti-apoptotic proteins are involved in antagonizing this process.

00:11:45.480 And what are some of the things that would have to be going wrong in a cell for it to go down that

00:11:50.580 suicidal pathway? So for example, mitochondrial injury that is irreversible, genetic mutation that is

00:11:58.900 unfixable. Like what are the suite of things that basically take a cell down the path of,

00:12:04.960 I can't fix this and being around here and replicating is going to be dangerous to the host. I got to

00:12:10.680 take myself out of the game. Right. So mitochondrial damage can certainly trigger apoptosis. But probably

00:12:18.180 the best way to explain it is by using the example of P53. So P53 is a tumor suppressor and a

00:12:26.960 transcription factor. And some of the transcriptional targets of P53 are proteins like PUMA and NOXA,

00:12:36.460 which are these antagonizers of BCL2 and activators of backs and back. P53 is a tumor suppressor.

00:12:45.360 One of the functions is to promote apoptosis to prevent an emerging cancer cell from progressing.

00:12:53.400 One mechanism by which P53 does that is by turning on the transcription of PUMA and NOXA,

00:13:02.120 and then that will antagonize BCL2 and initiate apoptosis. So then the question becomes what

00:13:09.600 activates P53 to do that? And that could be a long list of things from DNA damage, from oxidative stress,

00:13:17.820 and so forth. So you could think of something bad happens to an emerging cancer cell, and then

00:13:24.820 P53 gets activated. And one of the tumor suppression functions of P53 is to turn on these promoters of

00:13:34.820 apoptosis that antagonize BCL2. Now, loss of function in P53 probably accounts for half of all cancers,

00:13:42.040 correct? Right. And I assume that you have to lose both copies of it, or is losing one copy sufficient?

00:13:48.940 Well, what happens in most of the time is not deletion of P53, but rather a point mutation.

00:13:57.240 That reduces function. It's more of a dominant negative. So in fact, there's even evidence that

00:14:02.640 there's a gain of function. So there are hotspot mutations in P53 that are very common in cancer,

00:14:09.900 and P53 functions as a heterodimer. And what these mutant P53s do is that they end up entering into a 0.66

00:14:20.580 dimer with wild-type subunits, and that interferes with the function of the complex. So yes, in that

00:14:27.280 respect, it can be a loss of function of the P53 heterodimer, but there's evidence that it not only

00:14:36.220 causes a loss of function, but it actually may do other things as well that are cancer-promoting.

00:14:42.300 That's just a great example of the nuance of evolution, right? I mean, in med school,

00:14:45.440 the classic teaching, you know, 100 years ago for me was P53, loss of function, oncogene,

00:14:51.040 gain of function, black and white. Of course, it's never black and white.

00:14:54.060 Right. So what is the wreckage of apoptosis? So when a cell undergoes apoptosis to everything

00:15:03.220 outside the cell, inclusive of the immune system, what becomes visible? In other words,

00:15:09.220 does an apoptotic cell, once it dies, elicit any immune response? Or does the process of

00:15:15.220 apoptosis yield sort of an inert body of cellular matter that just goes away?

00:15:20.240 I'm not so sure I'm the best person to answer that question. I think the whole idea initially was

00:15:26.880 during the process of apoptosis, you would get protein degradation and packaging of pieces of

00:15:34.540 the dead cells into these apoptotic bodies. And then that would reduce inflammation. And then there's

00:15:41.920 evidence that macrophages can then go and take up these apoptotic bodies. And that may facilitate

00:15:49.280 antigen presentation and so forth. So it's possible, for example, that if you have a cell

00:15:56.760 that has become cancerous, either through a gain of function, loss of function, but whatever,

00:16:01.100 there's some mutation that now renders this cell to go down a pathway of cancer.

00:16:06.060 Fortunately, it undergoes the apoptotic transition. The macrophages take it. Is it likely that you get an

00:16:13.860 immune response to that that is protective in the long run against similar mutations? Because

00:16:18.940 I mean, even though the macrophage is part of the innate immune system, does that ever translate to

00:16:22.780 the adaptive immune system such that you gain some long-term immunity from that specific type of

00:16:27.660 mutation? Yes. I think something like that occurs. And I'm just thinking I'm the wrong person to answer

00:16:33.640 that question. I could give you the better names of people that can do a better job. But I think the best

00:16:39.740 way to compare it is to contrast it with necrotic cell death. So in apoptosis, you have proteolytic

00:16:47.520 degradation and of a cell and packaging it into these bodies. And you say, well, does that limit

00:16:56.700 inflammation? Well, the way to explain how it does is to compare it to a different form of cell death,

00:17:02.760 like necrosis. So necrosis is cells, lice, and that is very pro-inflammatory. You have nucleic acids

00:17:12.380 released. You have essentially everything is released. Including mitochondrial content, which

00:17:17.820 is probably the most immunogenic given its bacterial origin of the DNA. Absolutely. And so

00:17:23.360 apoptosis, what I'm hearing you say is apoptosis is much cleaner than necrosis. Absolutely.

00:17:28.200 So now let's talk about autophagy. Let's contrast autophagy with apoptosis.

00:17:34.100 That's right. Well, before we get to that, I should go back to your original question of like,

00:17:37.960 how did we start working on autophagy? And this sort of bridges us to what you just mentioned. So

00:17:44.480 when we disable apoptosis in a cancer cell, it can't commit suicide. And we're doing that all the

00:17:52.080 time. And we could show that then the tumor cells become more tumorigenic. But what we

00:17:57.940 didn't expect was the extraordinary propensity for survival. We could leave the cells out and

00:18:07.820 put them in buffer. They wouldn't die under extraordinary circumstances that we couldn't

00:18:15.940 explain. So why would a cell that just couldn't commit suicide survive in buffer with no nutrients

00:18:23.840 at all? And just for context, this is the mid 80s, late 80s?

00:18:28.640 This is the mid 80s. No, it was probably later than that. It was probably early 1990s. And so

00:18:37.020 it was a conundrum. I mean, just because a cell can't commit suicide doesn't explain how it can

00:18:42.540 be a cancer cell can just sit in buffer and be fine. And we puzzled over this, like, how can this be?

00:18:50.380 And then we discovered that what these cells had done was turned on autophagy. And we're using that

00:18:58.700 for survival. Before you go down that path, help me understand something. What did you observe about

00:19:04.600 those cells that were sitting there in the absence of nutrients surviving? Did you notice any metabolic

00:19:09.680 changes that were unusual? Like, what was your clue that they were able to usurp the environment they

00:19:18.520 were in? It was an act of desperation. We tried a bunch of things and nothing was informative. And

00:19:26.580 then I told the people in the lab, why don't we just look at these cancer cells under the electron

00:19:31.900 microscope? And that way we can, we can see everything because we couldn't understand how

00:19:38.220 they could be surviving a buffer. And when we got the electron micrographs back, we saw something we

00:19:43.760 had never seen before. And all these double membrane vesicles all over the cell. And so that,

00:19:50.920 when we finally, all those are autophagosomes, which we had never, ever seen.

00:19:55.660 But wait, how did you, I mean, first of all, this is just to me, one of the beautiful moments in

00:20:00.380 science that I think, I think it's so important for people who don't do science for a living to

00:20:06.480 understand that while science is 99% failure, every once in a while, you have a moment like that.

00:20:12.140 A eureka moment.

00:20:13.340 Yeah. It probably makes up for 10 years of failure.

00:20:16.880 Yes.

00:20:17.620 When you realize in that moment, you are seeing something that has never been seen before.

00:20:22.860 And therefore, this is the cusp of new knowledge.

00:20:26.900 That's right. That's happened to me a bunch of times in my career, which is fortunate. And this

00:20:32.420 was one of those moments. And then we started reading, oh, what are these autophagosomes? What do

00:20:37.440 they do? And then when we realized from when we looked in the yeast literature, they were

00:20:42.260 meant to capture intracellular proteins and organelles and bring them to the vacuole of the 0.65

00:20:49.220 mammalian lysosome for degradation and recycling. And that this was a mechanism by which yeast survived

00:20:55.720 starvation.

00:20:56.940 And what was the tumor line or what was the cell line you were doing this in?

00:21:01.780 At the time, we were using kidney cancer cell lines.

00:21:05.720 Mice or human?

00:21:07.140 These were mouse.

00:21:08.480 But it was basically the first time this had been seen in mammalian cell line?

00:21:12.020 No, I think people had seen autophagosomes before. I mean, you've got to remember in the

00:21:16.920 olden days when electron microscopes were first available, that that's one of the things that

00:21:23.260 people did was describe all kinds of different processes. So autophagosomes were known to exist,

00:21:30.620 but there was very, very little information, almost no information on autophagy and cancer

00:21:36.400 at the time. So we went into this area where there was almost no information. And so the first question

00:21:44.180 we asked is, okay, well, the yeast data tells us that when you see autophagosomes, that means

00:21:51.280 cells are starved and they're recycling and they're using this to survive. And we hypothesized

00:22:00.780 that that's what was going on in these cancer cells. And if that was the case, if autophagy was a

00:22:07.820 survival pathway in cancer, that was a game changer. We had to understand it and we had to demonstrate

00:22:16.660 that that that's what was actually happening. And then if that was the case, if cancer cells had

00:22:23.740 usurped the autophagy pathway for their survival, then we needed to inhibit autophagy for cancer

00:22:32.020 therapy. The first thing we did was we looked to see what would happen if we inhibited autophagy

00:22:40.580 in these cancer cells? And the answer was very simple. In many, many circumstances and many

00:22:48.520 different cell lines that we looked at, when you inhibited autophagy, the survival of the cancer

00:22:53.840 cells was reduced. Let me interject for a second and ask a question. I don't know if you ever did

00:22:58.780 this experiment, but if you took the kidney line and the kidney cancer line, so basically the same

00:23:04.060 histology from the same tissue from the same animal, but one has the oncogenic properties and

00:23:10.540 one does not, and you put them in the identical nutrient deprived stress, can you quantify the

00:23:18.480 amount of autophagy or the efficiency with which those two cells undergo autophagy? In other words,

00:23:23.280 is cancer simply preserving the autophagy capacity that it had as a non-cancer cell,

00:23:31.700 but not enhancing it or not having any attenuation of it? Is it simply just, hey,

00:23:36.260 this just happens to be something that gets preserved as you go from non-cancer to cancer?

00:23:40.040 Or is there some qualitative or quantitative change in the character of autophagy as a cell mutates?

00:23:47.300 That's interesting. So let me see if I can unpack that. So if you have the general observation

00:23:54.120 is that normal cells in the fed state don't have autophagy on, it functions at a very,

00:24:02.800 very low level. And if you starve cells or mammals for nutrients, then there's a massive

00:24:11.200 upregulation of autophagy. What was striking about the cancer setting was that even in the fed state,

00:24:19.360 autophagy was elevated. Ah, so there is a fundamental difference there.

00:24:23.860 Yes. And then if you stress them, it goes up even further. But the problem is,

00:24:29.740 is that when it's already high, how much higher can it go?

00:24:33.260 And just to be clear, Eileen, this is in vitro. So you can't even make, when you said that,

00:24:38.780 the first thought that came to my mind was, well, maybe the reason is they're undergoing a different

00:24:43.020 stress, which is, for example, a vascular stress, a hypoxic stress, because, you know,

00:24:46.520 haven't got enough VEGF or they haven't created enough. In other words, the apoptosis is going up

00:24:51.960 despite being fed because there's something else that's impairing them. But if what you just said

00:24:56.440 is true in vitro, then that wouldn't explain that, would it? In other words, if they're not

00:25:01.160 limited for oxygen, if they're in a petri dish and this is happening, my hypothesis wouldn't make

00:25:06.100 sense. That would only make sense if what you said was true in vivo. Right. So in the fed state,

00:25:11.260 the cancer cells already have elevated autophagic flux. And when you fast them, it does go up, but

00:25:20.420 it's only so high it can go. I see. So this probably, you know, it's really funny. I'm sure

00:25:27.060 you're familiar with the paper that Matt Vander Heiden and Luke Hantley and Craig Thompson run in

00:25:30.280 Science in 2009, which was, at least to my knowledge, the first time that someone offered

00:25:35.300 an alternative explanation for the Warburg hypothesis, which is, hey, it might not be that

00:25:39.580 the mitochondria of the cancer cells are defective and can't undergo oxidative phosphorylation.

00:25:44.820 It might be that they're optimizing for growth as opposed to metabolism. They don't care as much

00:25:50.200 about ATP as they care about building blocks. And therefore they're deliberately taking an

00:25:55.880 inefficient route of glycolysis to lactate because they want the cellular building blocks. And that

00:26:02.980 might be the explanation here is that the tumor cell is undergoing more constant proliferation and

00:26:10.360 therefore they want more building block. Exactly right. And in fact, when we look at cancer cells and

00:26:17.780 we study their metabolism, what we've noticed, and this is something that we found, and it's been

00:26:23.560 a common observation, is that nucleotides seem to be rate limiting. And so the metabolism of a cancer

00:26:33.780 cell is designed to facilitate de novo synthesis of nucleotides. So that's really interesting,

00:26:40.980 isn't it? When you realize something about it, like you think of all the things that could potentially

00:26:44.340 be rate limiting to a cell. Think of how many phospholipids, for example, they need to build

00:26:48.980 all of those cell membranes. And yet it's the nucleic acid to continue to propagate its DNA

00:26:57.200 that becomes rate limiting. That to me is very interesting. I wouldn't necessarily have ever guessed

00:27:02.000 that. We may learn more as going forward, but that is what seems to be a recurring theme. But it's not

00:27:09.980 just DNA, it's also RNA. And you have to remember that RNA and ribosomes make up a huge amount.

00:27:16.840 They're a much greater demand. Exactly. And I think David Sabatini has mentioned this many times that

00:27:22.520 a large amount of the mass of a cell is ribosomal RNA. And he had a beautiful paper

00:27:29.620 where he was making the argument that ribophagy, the autophagy of ribosomes,

00:27:35.880 was an important metabolic survival mechanism. And you could think of ribosomes as being a depot,

00:27:42.920 a storage depot for not only nucleic acids, but also protein. And when a cell

00:27:50.140 is stressed or starved, it doesn't need to make protein. So it doesn't really need large numbers

00:27:56.280 of ribosomes. And so the autophagy pathway can cannibalize those ribosomes because they're

00:28:03.180 unnecessary. And then recycle all that protein and nucleic acids to support survival. 0.94

00:28:10.600 A moment ago, you mentioned, of course, that some of this had already been observed in yeast. And

00:28:14.340 the moment we start talking about things that are true in yeast and then true in animals,

00:28:18.640 mammals, for example, or higher-order animals, we're talking about a billion years of evolution

00:28:22.240 here. So this ranks as one of the few things that seems remarkably conserved over evolution.

00:28:28.760 As a general rule, that makes it very important. Do we have a sense of when this first showed up?

00:28:36.420 Again, I might be out of my league. I mean, I know it's certainly a big

00:28:40.120 function in yeast. Prior to yeast, I don't know.

00:28:44.440 Yeah, but it's amazing. I mean, it's in the category of mTOR.

00:28:48.280 Yes.

00:28:48.880 Something that is so important that it just doesn't really seem to change over about a billion years.

00:28:55.120 Rule of thumb, it matters.

00:28:56.680 That's right. And I think when you compare how yeast does autophagy and how mammals do autophagy and

00:29:03.100 what they're using it for, it just looks like mammalian version of autophagy is a little bit

00:29:09.320 more complicated. It's probably, they have probably more different circumstances where autophagy

00:29:17.060 might be necessary, but the basic process is surprisingly the same.

00:29:23.940 What are some of the other stresses that induce autophagy? And let's maybe just for the moment,

00:29:28.360 even start with just in a normal cell. So let me sort of re-synthesize what we've talked about.

00:29:33.380 Clearly, nutrient deprivation is one of the biggest triggers for autophagy. And I mean,

00:29:38.380 maybe just for the sake of time, I'll kind of throw this out there and you can correct me if I'm wrong,

00:29:43.380 but I've always sort of thought of this through three pathways at the sort of mechanistic level.

00:29:47.860 So you have sort of the mTOR pathway, which is mostly sensing amino acids. You have the

00:29:54.120 AMPK pathway, which is mostly sensing energy and ATP in general. And then you have sort of the

00:29:59.920 acetyl-CoA protein deacetylation pathway, which is also just basically sensing substrate of fatty

00:30:06.140 acid and glucose. Is that sort of a fair way to say that those are three ways that low nutrients can

00:30:13.080 still trigger the same pathway? Yeah. And I think you could add on to that

00:30:17.800 stresses that result in organelle damage, such as depolarization of mitochondria or dysfunction of

00:30:26.800 mitochondria, activation of protein misfolding and generation of protein aggregates. So I think

00:30:34.520 there's the things that are directly related to metabolic signaling that you've mentioned,

00:30:39.640 but then there are other stresses that also can tie into the autophagy pathway.

00:30:44.080 Are there other stresses like the nutrient that are stresses that come from outside the cell to

00:30:49.380 inside the cell? So the protein misfolding, the mitochondrial depolarization, those are things that

00:30:56.180 are occurring as damage within the cell that stress. Do we know anything, for example, about temperature?

00:31:01.120 Do heat shock proteins stimulate autophagy in extremes of temperature? Does exercise, I mean,

00:31:07.040 which obviously is in the short term quite stressful, how potent is that at inducing autophagy in a normal

00:31:12.880 cell? So temperature wise, I would fully expect that temperature extremes would induce protein

00:31:20.340 misfolding and induce autophagy as a remedy for that. But I don't recall any studies on that. In terms

00:31:28.980 of exercise, that's very well studied that exercise induces autophagy very potently. And you actually need

00:31:38.380 autophagy to, because exercise damages the muscle and autophagy is one of the processes that helps

00:31:46.160 mitigate the damage that occurs during exercise. What about hypoxia? Oh, potently. Hypoxia potently

00:31:54.000 induces autophagy. Wow. And in fact, one of the first things we did was when we looked at tumors,

00:32:00.280 tumors are well known to have hypoxia in the center. When we engineered tumor cells to

00:32:08.100 be genetically deficient for autophagy, and you look at them, they're completely hollow.

00:32:16.160 Meaning they have no organelles, nothing? Not the cells are hollow. The tumor is hollow. Oh, wow.

00:32:21.880 The further the cells get from a blood supply, meaning the more susceptible they are to hypoxia,

00:32:27.300 they're dead. Right. So if you take a tumor, if the middle is hypoxic, that's where your autophagy is

00:32:34.040 most active. And if you genetically ablate autophagy in the tumor, you end up with a hollow tumor

00:32:39.420 because the tumor cells in the middle don't survive. Yeah. So it does come back to this

00:32:44.400 idea that we talked about earlier about hypoxia being potentially one of the things that autophagy

00:32:49.000 is protecting cancer from. Absolutely. How easy is it to create an animal model that is unable to

00:32:55.620 undergo autophagy? How difficult is that from a knockout perspective? Well, it's been done and we've done

00:33:01.340 it and it can be done different ways. So the original mouse strains that were made were deficient

00:33:07.680 in either of two of essential autophagy genes, one called HG5 and another one called HG7. And these

00:33:15.660 mice were developed in Japan and these mice are born, but they fail to survive the neonatal starvation

00:33:24.460 period. So when mammals are born... Meaning once they are cut off from an umbilical nutrient source,

00:33:29.760 it's almost like they have a glycogen storage disease, you know, those conditions where you

00:33:33.600 can't produce any glycogen, it's uniformly fatal if not treated the moment you're cut off from an

00:33:38.940 umbilical source of nutrient. Right. So that neonatal starvation period between the cutoff of the

00:33:47.480 placenta and suckling is a common feature in mammals. And there's potent induction of autophagy during

00:33:56.580 that period. I can't speak for humans, but certainly I would think so. And in mice, that's exactly what

00:34:03.200 happens. And so these autophagy deficient newborn mice don't survive. Wow. That really, I mean, again,

00:34:11.500 I think that simply underscores the evolutionary preservation of something. If you knock it out,

00:34:17.100 it is uniformly fatal. Do not pass go. Do not collect $200. You're gone.

00:34:21.380 And then what we did was, you asked a different question. It was like, what happens in an adult

00:34:27.240 mouse? So in a newborn mouse, it's a very different situation because any newborn mammal,

00:34:34.880 they don't have any fat. They have no reserves. And so when the Japanese group did the extraordinary 1.00

00:34:41.620 thing of trying to force feed these autophagy deficient newborn animals, and they didn't extend 0.99

00:34:48.160 their survival very much. Now, is this Yoshinori's group?

00:34:51.620 This was Niburo Mizushima and the Kumatsu group, I believe. I think it was coming from those two labs. 0.94

00:35:00.640 So what happened in that experiment?

00:35:02.040 They discovered that the mice died shortly after birth. And then they realized that, well,

00:35:09.360 they suspected they had a metabolic problem and they weren't suckling because they were probably too 0.96

00:35:15.440 ill by the time they would have been able to. So they force fed them and that allowed them to live

00:35:23.300 for 24 hours, but they still died anyway. And then are you able to induce an autophagy knockout in an

00:35:31.420 adult? Yeah. So that's what we did because we realized that the newborn animal is- It's just too

00:35:37.580 fragile. Too fragile. They have no nutrient reserves. And actually in the setting of cancer,

00:35:43.320 we're thinking of, you want to treat an adult with a tumor. So what's happening in autophagy in a

00:35:50.600 newborn animal isn't even relevant. And so we engineered mice where we can take an adult mouse

00:35:56.980 and give the mice a chemical so that an essential autophagy gene will be deleted throughout the entire 0.65

00:36:04.860 animal. So one day they're an adult mouse with autophagy. And then a few days later, they're an adult

00:36:11.500 mouse with no autophagy. And these mice were very extraordinary. They lived for two to three months

00:36:18.560 and then they died predominantly of neurodegeneration. Autophagy is very important in the brain over the

00:36:26.320 long term. But if we fasted the mice, they were all dead within 16 hours.

00:36:33.160 Let's unpack that again. That's pretty remarkable. So you take a normal mouse that's got through the

00:36:38.780 vulnerability period of infancy and you genetically knock out its capacity for autophagy. The first

00:36:45.560 thing you observe is if you fasted for 16 hours, which admittedly is a pretty long fast for a mouse,

00:36:49.920 that might be the equivalent of fasting a human for a week. But that degree of nutrient deprivation

00:36:55.440 is uniformly fatal. If you continue to feed them well, they only survive another couple of months

00:37:01.740 because they ultimately succumb to neurodegeneration, suggesting that the role of autophagy in preventing

00:37:09.280 neurodegeneration is essential. And it's really not surprising when you think about the role,

00:37:14.700 everything you talked about with protein misfolding. I mean, when you start to think

00:37:17.780 about the toxicities that are driving neurodegeneration, using Alzheimer's disease

00:37:22.880 specifically as an example, there's a lot of crap that's basically getting accumulated in neurons.

00:37:29.820 This would be an elegant way to suggest that autophagy is keeping that at bay.

00:37:34.740 Exactly right. So one other way of looking at it is what tissues are more autophagy dependent than

00:37:43.340 others? Exactly. Brain would be really important. And there are a few others. And what we've noticed

00:37:48.960 when we looked at the mouse, the lacked autophagy, when we genetically deleted the autophagy gene in

00:37:56.200 the adult mouse, was that there were tissues like the brain that were very sensitive. And there were

00:38:02.920 other tissues like the lungs that didn't have any phenotype. So wait, in other words, when those

00:38:09.120 animals ultimately die of neurodegeneration and you undergo the pathology analysis, obviously the brain

00:38:14.360 is where you see the cause of death. You're saying in the lung, it looked completely normal.

00:38:19.640 Relatively normal. What about liver?

00:38:22.180 Liver was very sensitive. So it doesn't lead to the death of the mouse. So if you did a liver specific

00:38:30.360 knockout of an essential autophagy gene, those mice have theotosis and their liver gets huge and

00:38:37.440 whatever, but it doesn't kill them. I mean, they can live for quite a long time.

00:38:41.620 So you induce fatty liver disease. So again, suggesting that autophagy probably plays a role

00:38:47.580 in preventing fat accumulation in the liver. Exactly right. And also protein aggregate

00:38:52.580 formation. One of the other phenotypes of steatosis is the accumulation of these Mallory bodies, 1.00

00:38:59.400 which are large protein aggregates composed of a protein called P62. When you lose autophagy in the

00:39:06.360 liver, you're causing accumulation of fat accumulation of protein aggregates, but the liver manages to 0.71

00:39:14.640 tolerate it. The brain, however, is a different story. If you have post mitotic neurons where

00:39:22.240 they don't have the capacity, they don't have the capacity to do that. I mean, when they accumulate

00:39:26.540 the crap, as you said, then it's game over. 0.98

00:39:29.240 Was there evidence that the brain in some last ditch effort to survive was undergoing more apoptosis 0.99

00:39:37.080 of neurons? Yes. That's a common feature of these animals is increased apoptosis in the brain. But

00:39:44.940 before that, you see all kinds of terrible things going wrong. This has been part of a major effort

00:39:50.980 to generate autophagy stimulators as a remedy or as a means to delay neurodegenerative diseases.

00:40:01.060 I want to come back to this later on in the discussion, but I'll just plant the seed now.

00:40:06.140 Obviously, fasting is one of the most potent stimulators of autophagy. I spend a lot of time

00:40:11.660 thinking about how does fasting fit into our toolkit of longevity? A big part of longevity,

00:40:19.760 in fact, probably the single most important piece of longevity when it comes to the lifespan aspect

00:40:24.660 of it. So, you know, you think of lifespan versus health span, how long you live versus how well you

00:40:28.260 live. On the how long you live front, I think it's very safe to say, based on all of the animal data

00:40:34.260 and frankly, all of the centenarian data, that the key to living longer is delaying the onset of

00:40:40.520 chronic disease. So even when you look at centenarians who are genetically gifted with tools to live

00:40:47.820 longer, if you unpack what the gift is, it's delaying the onset of the disease, not living

00:40:54.780 longer once you have the disease. So the centenarians, once they get cancer and once they get heart

00:40:59.340 disease, they die at about the same rate over the same duration as the rest of us schmucks. 0.95

00:41:04.040 The difference is they get those diseases 20 to 25 years later. And again, that suggests to me that 0.94

00:41:10.420 if you want to live longer, you have to delay the onset of these things, not live longer once you have

00:41:14.200 them. And so it's hard to think that fasting doesn't play an essential role in that. When you realize

00:41:21.740 the role that fasting plays in the mitigation of Alzheimer's disease and metabolic disease, of course,

00:41:28.180 what we're going to come back to in a second is cancer, which seems to be this conundrum. This is the

00:41:32.400 needle we're going to want to thread a little later down the line. I'll plant the seed now, but I do want

00:41:37.900 to come back to the idea of ways that we can also induce autophagy sort of pharmacologically or

00:41:45.000 chemically. The first thing that would jump to your mind is anything that mimics fasting. The first

00:41:49.800 thing that comes to mind would be metformin, rapamycin, things like that, that what we talked about

00:41:54.700 earlier, just for the listener to sort of tie this together, we talked about these huge pathways that tell

00:42:00.760 the body nutrients are scarce. So when mTOR activity is down, that's a sign that we're deficient in amino

00:42:08.200 acids, but we can also do that with rapamycin. When AMPK is up, that's the cell being told we're

00:42:15.480 deficient in ATP. Another way you can do that is to give metformin. We haven't talked about sirtuins yet.

00:42:21.400 Maybe I'll pause for a moment. Do we have any sense of what sirtuin activity does in autophagy?

00:42:26.940 I'm not familiar with that literature. Okay. I was going to say,

00:42:30.300 because then you could get into the whole NAD versus NADH ratios and how that might factor into

00:42:34.860 it. So again, I'm really curious about this through a clinical lens as well, which is what

00:42:40.160 is the suite of products, but almost just saying that out loud. So between the two of us, we remember

00:42:44.260 to come back to this, but I now kind of want to get back to your story, which is we've got these mice,

00:42:49.280 you've got this much more elegant experiment now, which is you're actually going after the phenotype

00:42:53.480 of interest, which is in an adult in which you inhibit autophagy. What was happening in that

00:42:58.980 animal if it had cancer? So did you ever do the experiment where you had an adult with cancer,

00:43:04.680 then you knock out autophagy? That's actually one of the reasons we made that mouse.

00:43:10.080 So we had two questions we wanted to answer. One was if you inhibited autophagy in an adult mouse,

00:43:17.940 what would happen? Because if they died in an hour, then targeting autophagy for cancer therapy

00:43:24.480 would be pointless. Especially if you can't do it specifically. That's right. So the answer was

00:43:29.460 they didn't die in an hour, they died in two or three months, which was actually good news,

00:43:33.860 because that meant that there was a potential window of opportunity for inhibiting autophagy for

00:43:40.800 cancer therapy. And I'm sorry, Eileen, when they died in two to three months, was it still from the

00:43:44.620 neurodegenerative disease? And did they still have cancer at the time of death? We had to first make

00:43:48.920 a mouse that lacked where we could switch off autophagy and find out what happened to that mouse.

00:43:54.800 Okay, so we did that. And we saw that they died of neurodegeneration two or three months,

00:44:00.680 which was good. They died immediately, then we would have stopped, there would be no point in trying

00:44:06.160 to make cancer on that animal. But we did learn that they were intolerant to fasting, which was

00:44:12.840 perfectly consistent with everything we knew about what autophagy functionally did. So then we moved

00:44:19.220 to the second step, was to do the experiment that you just suggested, to make cancer in that mouse.

00:44:27.540 And then after the mouse had cancer, to then shut the autophagy pathway off. And then to ask the key

00:44:34.340 question, which died first, the mouse or the tumor? And the answer was the tumor died first.

00:44:41.840 Wow. Okay, so then here's the gangster question. Once the tumor died, could you reactivate autophagy

00:44:48.560 to prevent the neurodegeneration? Or is it a one switch direction?

00:44:52.700 That required a different type of mouse model. So what we were doing was making a mouse with cancer.

00:44:59.520 And then once the mouse had lung cancer, in this case, we deleted an essential autophagy gene in the

00:45:06.140 entire mouse tumor and all. But the gene was gone. So it wasn't like we could turn autophagy back on

00:45:14.120 in that model. But since then, one of my trainees in collaboration with a lab in the UK, they have

00:45:21.180 developed a model where they can toggle autophagy off and then back on again. And what they've seen

00:45:29.360 is a remarkable capacity of the normal tissues to restore themselves. So the experiment would be to

00:45:38.020 have a mouse to induce an shRNA to a specific autophagy gene to down regulate the expression

00:45:45.920 and inhibit autophagy that way. And then later on, take that shRNA away or shut it off and restore

00:45:55.680 normal autophagy in the mouse. And you see a lot of capacity for the tissues to restore themselves

00:46:03.440 back to normal. So that experiment basically becomes the proof point that says targeting

00:46:12.460 autophagy in cancer makes sense. That's probably the most elegant description you could provide of that.

00:46:18.580 That's right. I think it would be better if we had specific targeted therapies against

00:46:25.660 some of the enzymes in the autophagy pathway, because these are all genetic experiments. And

00:46:32.060 it's not exactly the same. Right. You might not get the complete penetration with a drug.

00:46:37.580 Or inhibiting a protease is not exactly the same as deleting the gene. But this is all what's called

00:46:45.640 proof of principle that the concept of inhibiting autophagy in cancer is valid.

00:46:52.180 So what do we know today about what you've just described as it pertains to two things? So I want

00:47:00.720 to slice the data across two variables. The first is tissue type or histology of cancer. And the second

00:47:08.100 is underlying genetic mutation. So I know that a lot of what you're describing is clearly true in KRAS

00:47:14.600 mutation. What about other drivers? We and a number of other cancer labs that use genetically engineered

00:47:24.140 mouse models for cancer have been banging away at that for a number of years. And what we've learned is that

00:47:30.580 KRAS driven lung cancer and pancreatic cancer are extraordinarily autophagy dependent. And you do it, you know,

00:47:39.660 make the mouse models and the tumors are very susceptible to the functional loss of autophagy.

00:47:45.720 Can you briefly tell folks what a KRAS driven cancer does? Like what is it about the mutation that drives

00:47:51.720 the oncogenesis? So KRAS is a GTP binding protein that is responsible for activating what's called the

00:48:00.740 MAP kinase pathway. And this pathway is very key in driving cell proliferation. And so cancers

00:48:09.480 have a mutation in RAS or mutations in RAS that leave it in the GTP bound or on state. So there's

00:48:19.080 perpetual growth signaling through the MAP kinase pathway. Which of course is the hallmark of cancer,

00:48:25.160 which is it's unresponsive to cell signaling. And when you are fixed in the on position,

00:48:29.300 you can't turn off. And basically that is cancer. That's right. And what's particularly

00:48:34.960 interesting about RAS driven cancers is that we have been very unsuccessful in drugging RAS.

00:48:42.800 And there's recent hope that the cysteine, the particular subset of the mutations in RAS that

00:48:49.940 involve a cysteine residue, that there are now drugs that target that. There's hope after decades of

00:48:57.080 failure.

00:48:57.720 Is the primary issue in the failure to drug RAS that you can't do it without creating toxicity for

00:49:05.320 other cells that are non-cancer or that it has too many workarounds to whatever you put in place?

00:49:11.080 I think too many workarounds is a common problem. What they've done is that they said, okay,

00:49:16.860 if targeting RAS is difficult, then let's go downstream of RAS.

00:49:20.600 And try MAP kinase.

00:49:21.720 Right, right. So there are inhibitors of RAF, MEK, and ERK, which are downstream of RAS. And those are

00:49:29.600 actively in use in the clinic, but they seem to be not durably effective in RAS driven cancers because

00:49:39.200 of the workarounds.

00:49:41.060 Yeah. So are there mutations or mutant drivers of cancer that we know are not dependent on autophagy

00:49:49.180 and unresponsive to the autophagy blockade?

00:49:52.680 Yeah. It seems like there's a spectrum. So RAS driven cancers are particularly sensitive.

00:49:59.620 BRAF driven cancers like BRAF V600E is a common BRAF oncogenic mutation. And those cancers are

00:50:09.160 particularly sensitive. And those, the ones that were examined were lung cancers and melanoma.

00:50:14.920 The BRAF V600E mutation melanoma is very common. Homologous recombination deficient breast cancers.

00:50:24.700 And those would be, well, I mean, those would be models of hereditary breast cancer. Those are very

00:50:30.980 sensitive to loss of autophagy. APC deficient colon cancer is another example.

00:50:38.920 What about non-APC driven colon cancer, which of course is the majority of it? What do we know about that?

00:50:44.920 I don't think I can remember seeing a paper. I remember the APC deficient model. That's in fact

00:50:52.500 the most commonly used model.

00:50:54.360 Anything we know about prostate cancer or other hormone sensitive breast cancers?

00:50:59.700 So prostate cancer is sensitive. We did that work. And hormone sensitive breast cancer, 0.97

00:51:06.080 I'm not recalling right now, but there are a long list of cancers that are sensitive. The sensitivity

00:51:12.700 is not all equal. For example, BRAF driven cancers are very sensitive, more so than RAS driven lung

00:51:20.960 cancer. So you just compare lung, BRAF lung cancer to RAS lung cancer. The BRAF mutant lung cancer is more

00:51:28.440 sensitive. The most sensitive cancer that we've encountered is in fact, RAS driven lung cancer with

00:51:35.620 LKB mutations. And this makes a lot of sense too. So one of my trainees who has her own research lab

00:51:43.180 hypothesized that we sat down and we thought, what cancer would be, would you predict to be most

00:51:49.960 autophagy dependent? And it should be a cancer with loss of LKB1. LKB1 is a tumor suppressor gene

00:51:58.520 that's involved in activating AMP kinase. And AMP kinase activates autophagy as a survival mechanism to

00:52:07.400 low energy. And so there were a whole class of lung cancers that have lost LKB1. And as a result,

00:52:15.860 they can't activate this protective mechanism. This is Dr. Jessie Guo. She made this mouse model,

00:52:23.180 rash driven lung cancer without LKB1. And lo and behold, when you delete an essential autophagy gene,

00:52:30.580 you abrogate tumorigenesis. So it makes a huge amount of sense. LKB deficient rash driven lung

00:52:39.080 cancer is probably the number one sensitive tumor. So how do we reconcile these two observations

00:52:48.220 that almost seem to have a difficulty coexisting? So the first is everything you've just stated,

00:52:54.400 which is pretty clear and unambiguously suggesting that autophagy is at least for a number of cancers,

00:53:03.960 an important part of their survival and proliferation. And we contrast that with an

00:53:11.060 abundant body of literature that suggests that when you combine fasting, which is a potent

00:53:17.420 inducer of autophagy with chemotherapy, for example, you enhance its efficacy. And we can

00:53:23.900 speculate about why that might be the case. These two things, although not directly comparable,

00:53:30.100 seem a little bit at odds. How do you think about those things?

00:53:34.960 I would probably think about it in a slightly different way. So if you want to get at the two

00:53:40.880 different roles of autophagy, one is cancer cells usurping it and turning it on for their own

00:53:47.200 survival. Then the other side of it is when we know that autophagy is protective. We know what

00:53:54.460 happens if you have a mouse without autophagy. Many terrible things happen. It takes a while,

00:53:59.780 but the mice die of neurodegeneration. Can I interrupt for one second? I'm sorry to do this,

00:54:04.340 but I'll forget this question. I want to come right back to your thought. In those animals that

00:54:08.780 died of neurodegenerative disease after two to three months, did they show an increase in

00:54:14.140 tumor genesis in any other tissue? No, they don't. But if you make a mouse

00:54:20.140 where you bypass the neurodegeneration by knocking out an essential autophagy everywhere else,

00:54:27.680 okay, but not the brain, then those mice will get benign hepatomas, so benign tumors of the liver.

00:54:34.740 But that makes sense too. Think about autophagy in normal tissues. We know it's important because if you

00:54:41.520 knock autophagy out on a mouse, there's tissue-specific but gradual deterioration,

00:54:47.820 ultimately leading to neurodegeneration, and you end up with steatosis, fatty liver disease.

00:54:54.100 The brain phenotype can be explained, as we discussed before. Neurons in the brain need this

00:55:01.000 protein and organelle quality control function. They're post-mitotic. They have to have a way of

00:55:05.920 getting rid of the garbage. In the liver, what happens when you damage the liver?

00:55:11.800 It regenerates. It's got infinite capacity.

00:55:14.160 That's right. But what happens when you-

00:55:16.980 Unless there's too much inflammation.

00:55:18.960 Exactly. So you end up with, when you inactivate autophagy in the liver,

00:55:23.420 you end up with these chronic cycles of damage, repair, and chronic inflammation.

00:55:28.500 And that is oncogenic. And that's not, you know, it's particularly obvious in the liver.

00:55:34.400 The pancreas as well.

00:55:35.540 Exactly.

00:55:35.820 Very, very sensitive to that inflammation.

00:55:37.820 So I think what this is telling us is something very important. It's telling us that a main function

00:55:44.960 of autophagy in tissue homeostasis is to preserve cellular function to be normal to prevent chronic

00:55:56.220 damage and inflammation. And tissues that are susceptible to cancer as a result of chronic

00:56:02.760 damage and inflammation, autophagy is highly protective.

00:56:07.400 Which again, think about how complicated this is. Now I'll bring us back to the question I posed

00:56:12.340 a moment ago, but using this example, why does NAFLD ultimately lead to cancer? Because if you have

00:56:18.060 enough accumulation of fat, you get enough inflammation, you're going to get a pedacellular

00:56:21.220 carcinoma. Same with pancreatic cancer. Highly, you know, this is why alcohol is such a horrible

00:56:26.420 molecule. So toxic to the pancreas, to the liver, and you sow those seeds of inflammation and lo and

00:56:33.420 behold, you're increasing this risk of cancer. So on the one hand, we know that autophagy helps

00:56:39.280 ameliorate that. It cleans that up. It buffers that. At the same time, we just realized a moment ago,

00:56:44.400 oh boy, once you do get pancreatic cancer, it's a KRAS-driven cancer, autophagy is helping it.

00:56:50.200 That's right.

00:56:50.620 So now let's come back to the question I posed a moment ago that I so rudely interrupted you in

00:56:54.140 answering, which was, how do you reconcile these?

00:56:57.300 I think it's a matter of thinking of the role of autophagy in cancer as being context dependent.

00:57:02.560 On the one hand, functional autophagy can delay the onset of chronic damage and inflammation

00:57:10.620 that are known causes of cancer in particular tissues, such as the pancreas and the liver

00:57:16.340 amongst a few others. So I think that stimulating autophagy through fasting or through pharmacologic

00:57:25.920 means at one point can be thought of as preserving health. But once you have a cancer, I think it's a

00:57:33.140 different ballgame. And at that point, it's a completely different context. And in that setting,

00:57:42.360 what we've learned is inhibiting autophagy is preferentially damaging to the tumor compared

00:57:49.580 to the normal tissues.

00:57:51.600 And then going back to the other literature, which looks at the efficacy of fasting combined

00:57:58.140 with chemotherapy, which is superior to just chemotherapy, do you think that the reason for

00:58:04.660 that is that the chemotherapy itself, maybe once you're rendering the cells more sensitive to

00:58:12.160 chemotherapy and also potentially generating a more durable immune response? Because one

00:58:16.920 interpretation of what you're saying is a person with cancer should never be calorically restricted.

00:58:21.240 I don't know. That's going too far. I would say that I don't know that you can equate caloric

00:58:29.140 restriction with the loss of autophagy or regulation of autophagy because I think they're not equal

00:58:36.780 things because I think that caloric restriction is limiting tumor nutrients. And so I think what that's

00:58:45.280 doing in the context of cancer therapy needs to be better understood. I'm just not sure that we know

00:58:53.320 what's happening there.

00:58:56.120 If I'm hearing you correctly, you're saying, look, it might be that we can't necessarily say that

00:59:00.580 fasting isn't helpful in cancer because while it may be counterproductive from the standpoint of

00:59:07.300 autophagy, that may be offset by other things that are beneficial, such as the reduction of overall

00:59:11.780 nutrients and inflammation that accompany this.

00:59:14.040 Exactly right.

00:59:15.540 Yeah. To me, of all of the areas of autophagy that have me scratching my head the most,

00:59:21.100 it is this question of, given that fasting is one of our most potent ways to stimulate it. In fact,

00:59:28.480 I would argue it's more potent than metformin, which is an AMPK activator, more potent probably

00:59:33.020 than exercise. I mean, it might be the most potent thing we can do to turn this amazing tool on.

00:59:37.740 How do we think about using it in disease prevention and disease treatment? And they aren't necessarily

00:59:42.860 the same thing.

00:59:43.520 I completely agree. And in fact, I would ask a question of you. So there's multiple efforts in

00:59:51.460 the biotech industry to identify pharmacologic agents that are potent stimulators of autophagy.

00:59:58.400 And I think their idea is, is that normal, healthy people will take a pill, autophagy will be turned

01:00:05.080 on, and there'll be some fountain of youth type thing.

01:00:09.420 Yeah. Spermidine is one of the things that people are talking a lot about, right?

01:00:12.500 So why not cultivate the use of fasting instead?

01:00:18.680 I will tell you exactly why, Eileen. And I love how you have fed into, it's almost like you can

01:00:24.580 read my mind and know where I'm going to go with this discussion. I think a big part of it is we

01:00:30.780 don't have the tools to measure the signatures of autophagy. In other words, if a patient comes to me

01:00:37.840 and says, Peter, I want to do whatever I can to enhance autophagy because I have now bought into the

01:00:45.280 idea that it is going to basically protect me from every chronic disease. And I would say,

01:00:50.180 yeah, I agree with you. And they say, great. Fasting seems like a great way to do it. I'd say,

01:00:54.240 you're absolutely right. And they say, well, how long do I need to fast, Peter?

01:00:57.560 Guess what I get to say? I don't know. And I'll tell you in reality what I say. I say, well, look,

01:01:03.220 I'm really sure that after about seven days of nothing but water, autophagy is fully cranked.

01:01:09.320 And I'm also really sure that if you just go 12 hours without a meal, you probably haven't done

01:01:15.120 anything. Where I struggle is we're between them. Now I want to share with you some personal

01:01:21.100 experience and I want you to weigh in on it. And then I think maybe we can pivot off into

01:01:25.780 actually kind of going back to what you and I spoke about over the phone five or six years ago,

01:01:30.200 which is what would a molecular signature for autophagy look like? And again, I think this is,

01:01:36.340 I put this in the top three most important translational questions in my field. In other words,

01:01:42.380 as I think about the practice of medicine, as it pertains to longevity, it's our inability to

01:01:49.140 understand how to quantify the benefit of nutrient deprivation. In other words, our inability to dose

01:01:55.360 it. That is our greatest, certainly among our top three detriments to using this incredibly potent tool.

01:02:03.280 So I fast a lot. I just finished a fast yesterday, actually. So I used to do a thing where I fasted

01:02:09.080 seven days every quarter. So four times a year, I would just do a water only fast.

01:02:14.640 How hard is it to do that?

01:02:16.960 It is not that hard. I'm going to be completely honest with you. I wish I could sit here and say,

01:02:21.680 oh, I'm a real stud. Nobody can do it. No, no, no. Anybody can do it. I really think anybody can do

01:02:27.060 it. Which is not to say that there aren't moments throughout those fasts where it's sort of difficult,

01:02:31.040 but you'd also be surprised at how resilient the body is. So yeah, not that hard. You have to make

01:02:36.720 some adjustments. Obviously you have to be very thoughtful about how much water you're drinking

01:02:41.020 and how many electrolytes you supplement. There are a lot of changes that are happening in terms

01:02:44.640 of electrolyte management and things like that. But again, we certainly have the knowledge to know

01:02:49.120 how to manage people through that. But I began to ask the question, right? Which is, okay, is seven

01:02:55.180 days a quarter the right dose? I'm convinced that it's a big bolus of autophagy, but is it frequent

01:03:01.400 enough? What about three days every month? That's about the same number of total days fasted,

01:03:08.200 but it's more frequent, but it's probably less potent. And the reason I sort of decided to try

01:03:12.680 three days a month was I noticed that a couple of things happened at the end of my fasts. So I always

01:03:19.500 check my blood before and after one of these seven day fasts, and there's a very predictable set of

01:03:24.260 changes that occurs. Some of them that are really obvious. Glucose plummets. Insulin becomes

01:03:29.260 unmeasurable. Uric acid goes through the roof, along with beta-hydroxybutyrate, of course.

01:03:36.080 Two possible explanations for the uric acid going through the roof. One is the breakdown of nucleic

01:03:41.500 acid. And obviously, when I talk go through, I mean doubling of uric acid. So much so that I

01:03:46.980 started taking allopurinol during a fast to make sure I didn't get gout. Of course, it could also be,

01:03:52.900 and I've read something that says that uric acid and BHB compete for the same transporter in the

01:03:58.340 kidneys. So there might also be a bit of a competitive blockade, but nevertheless, we have

01:04:01.940 at least one possible explanation there. Endocrine function changes dramatically. T3 goes down

01:04:07.380 significantly and reverse T3 goes up significantly such that the ratio of them changes by four to six

01:04:14.720 fold, which means you basically shut off metabolism. Not surprising. Explains why you become incredibly

01:04:21.620 cold and tolerant during a fast. And also gonadotropins go down. So you have all these really

01:04:27.540 predictable things. Well, what I noticed was I see virtually all of them, though not quite to the

01:04:32.620 same magnitude after three days, but not after two days. So that just got me intuitively thinking

01:04:38.680 in a hand-waving way that three days was sort of the minimum dose you needed to really move the

01:04:47.200 needle on a bunch of these other metabolic things, meaning the spike in uric acid, the bottoming out

01:04:52.400 of glucose. So there's another thing that sort of happens. It's as you turn more and more free fatty

01:04:57.460 acid into ketone and turn more glycerol into glucose, you reach an equilibrium where your glucose is

01:05:03.800 pretty much going to stay at about three to four millimolar. And that takes about two to three days.

01:05:09.540 And again, when we think about it through the lens, we've already discussed AMPK must be up through the

01:05:15.560 roof, mTOR must be through the floor, and protein deacetylation must be off. I think my gestalt is

01:05:23.820 that that takes about three days. And obviously it gets greater and greater the more you go. But what

01:05:29.640 would be amazing is if I could draw a tube of blood, send it to you after a three-day fast, a four-day fast,

01:05:36.960 a five-day fast, a seven-day fast, a 10-day fast, and get some sort of quantification. What is it that we

01:05:44.080 would see in... Now, of course, it's complicated because you'd probably want to accompany each of

01:05:49.140 those tubes of blood with a muscle biopsy so that you could look at LC3, LC2, and things like that.

01:05:53.580 So I'll stop on my diatribe for a moment and now turn it over to you, which is where would you even

01:05:59.260 begin to look for that signature of autophagy? And let's just start broadly with any tissue. You can

01:06:03.800 have blood, you can have muscle, you can have liver, you can have adipose tissue. How would you now

01:06:08.900 create a dose effect? Well, we know that what happens in a mouse, let's just take a minute to

01:06:17.020 discuss that. So Mizushima Lab made a mouse that had a transgenic LC3 EGFP protein expressed,

01:06:26.440 and they could use that mouse. Tell folks what LC3 is just so... Because we're going to talk about

01:06:30.340 this quite a bit. So LC3 is the protein that is attached to the autophagosome membrane and links

01:06:38.600 to the cargo that ends up in the autophagosome. So this is a very mechanical thing, right? Like

01:06:44.600 this goes back to your observation in the electron microscope. Exactly right. So LC3 is one of the

01:06:50.920 key proteins attached to the autophagosome membrane. And you use it to see autophagosomes because

01:06:59.960 normally when autophagy is off, LC3 is diffuse. But when autophagosomes form, the LC3 protein is

01:07:10.020 attached to them and you start to see spots where all the autophagosomes are present. And so the

01:07:17.520 Mizushima Lab used that to assess autophagy in a living mouse. They fasted the mouse and they found that

01:07:26.920 they could see the formation of autophagosomes throughout the mouse.

01:07:31.560 And could they do this in like PBMC out of blood or did they need to use tissue?

01:07:35.560 They did it with tissue. What they learned was that yes, autophagy is turned on during fasting in

01:07:41.880 a mouse, which wasn't surprising, but it seemed to not be uniform across every tissue. So that was

01:07:50.000 interesting. But we don't have a way to do that in people. All we can do, because this is involved

01:07:57.420 making a genetically engineered mouse. So the only thing we can do in people would be to look at a

01:08:04.100 tissue section and stain it for LC3 and look to see if there were spots.

01:08:09.700 In other words, you could not look at LC3 conversion in white blood cells.

01:08:14.000 You could, but there's another problem in that you could take PBMCs and do a Western blot for LC3

01:08:21.380 and LC3 gets processed from LC3 one to two. And the two form is the one that's attached to the

01:08:29.660 autophagosome membrane. So you could do a Western blot of PBMCs to measure the conversion of one to two,

01:08:38.980 but then two ends up in the lysosome and gets degraded. So the typical measurement of

01:08:47.280 autophagic flux involves measuring the rate at which LC3 one gets converted to LC3 two,

01:08:55.160 and then the rate at which LC3 two ends up being degraded in the lysosome. And in order to see that

01:09:03.060 flux, you need to block the degradation of LC3 two in the lysosome with baphylomycin or hydroxychloroquine.

01:09:13.080 And so you would only be able by looking at LC3 one and two in PBMCs in a person that was fasting,

01:09:21.460 you would only be able to infer autophagic flux because you wouldn't actually be able to measure it.

01:09:29.360 It's a clue. It's a clue. It wouldn't be proof, but it would be one could presume. I would expect

01:09:36.680 you would see more conversion of one to two and then two going into the lysosome. I don't think

01:09:43.140 that would get you the answer that you need. Now, what if we had a hundred volunteers who are willing

01:09:48.340 to fast and subject to blood draws and muscle biopsies? So you could use the muscle biopsies

01:09:56.100 to actually quantify the flux and establish, let's say you could do it at a different time point.

01:10:01.780 So you had a hundred people fast for different periods of time, three, four, five, six, seven

01:10:06.080 days, et cetera. You've got tissue and you've got blood. What else could you look for? So again,

01:10:11.620 could BHB be a proxy? Could glucose be a proxy? I remember you once mentioning another organic

01:10:18.600 molecule you had identified. You knew it by how many carbons it had, and you thought it was ringed,

01:10:24.360 but you weren't sure what it was yet. Have you figured that out?

01:10:27.540 Yes. That was something that accumulated when we inhibited autophagy, and that was glucuronic acid.

01:10:34.560 So that would be, I think you're going down the right road. So I think what we can do,

01:10:41.720 and we haven't really done this yet, would be to look at metabolites because metabolism is so

01:10:50.300 drastically changed. So if we can't look at directly measure autophagic flux in humans very easily,

01:10:57.860 because we don't yet have the proper tools, we could use metabolites as surrogate markers for

01:11:07.900 the consequences of autophagy.

01:11:11.940 That's exactly why I call it a signature as opposed to a biomarker, because I think it's basically,

01:11:17.440 how do you use machine learning to take many metabolites? There's a bunch of things we know

01:11:23.820 are happening. We just have to integrate them. We know that leucine is going down. We know

01:11:27.960 methionine will be almost unmeasurable. We know what's going to happen to glucose, uric acid. And

01:11:33.400 then there's probably a whole bunch of other small molecules and things in the proteome that we don't

01:11:37.500 yet know that are probably discernible from PBMC directly or indirectly through other things in

01:11:44.620 the plasma. And it just seems like a problem that is so ripe for a machine learning environment where

01:11:51.000 you don't need that many people because you know what the gold standard is. You just starve them. And

01:11:56.820 then you have the check, which is the muscle biopsy, which can give you some sort of quantifiable

01:12:01.140 gradation. I mean, do you get the sense that that's something an IRB would approve? It's invasive,

01:12:06.500 you know, it requires biopsies and fasting and things like that. But, or would they demand that you,

01:12:10.540 hey, first you have to do this in mice? That's what I would expect. And so one of the things that

01:12:15.840 we have been talking about is we've done some of this, but probably not enough, is to do a metabolic

01:12:24.600 characterization of a wild type mouse fasted versus an autophagy deficient mouse fasted. I think that

01:12:33.460 would potentially identify the metabolic changes that were autophagy dependent. And I think that would

01:12:40.520 provide some clues as to what to look at in humans, because the problem with looking at metabolism

01:12:47.680 is you get an enormous amount of data and it's very, very helpful to know what to look for. We may

01:12:54.520 have a list of things that are obvious to look for, but... Right, but the fine tuning is going to come

01:12:59.660 in the non-obvious. It's not going to be a regression model based on five things we know. It's going to be

01:13:04.720 much more complicated. And I prefer not the under the lamppost science.

01:13:10.780 Yeah, take an unbiased view and go... And honestly, I get asked about this more than any other

01:13:17.240 translational problem. So the good news is I think there are a lot of people in the philanthropic

01:13:22.180 community that would be interested in this, even if this is not a question NIH is interested in.

01:13:26.880 I doubt NIH is interested in this problem, although that strikes me as

01:13:30.760 odd given how potent a tool fasting is and yet how we don't know how to dose it. And I think it's worth

01:13:37.280 pausing on that for a moment because that is such a stark statement, if I'm correct. I believe I am.

01:13:43.160 Which is, imagine we had the most amazing drug imaginable. Imagine we had a proteose inhibitor

01:13:50.640 for HIV and we knew deep down this could cure HIV. The problem is we didn't know how to dose it.

01:13:56.580 How long would we tolerate that ignorance? Imagine we had a drug that we knew could kill cancer,

01:14:04.260 but we just didn't know how much to give or how often to give it. We wouldn't tolerate that for

01:14:09.240 a minute. And yet in fasting, we have arguably the most potent tool, and certainly if not the most

01:14:17.600 potent, probably one of the three most potent tools in which we can affect human health. And we don't have

01:14:23.900 a clue how to dose it or what frequency with which to use it. And I find that ridiculous.

01:14:31.180 So I'm actually really confident that if there were a really great proposal put together that

01:14:38.380 would go from the animal model to the human model, it would be fundable. It would be fully fundable

01:14:44.140 through philanthropic efforts. And so if nothing else comes of this discussion, I would love to plant

01:14:49.300 that seed with you and think about what would be the right consortium of people to do that work.

01:14:54.380 Obviously, there are lots of skill sets that we'd want to have involved in there, but I really believe

01:14:59.640 that could be funded quite easily. And I think that the implication of that is as potent as anything

01:15:04.400 else. Because again, here I am doing my three-day fast every month versus my seven-day every quarter

01:15:09.840 versus five-day every quarter. We just don't know. And it really is troubling to me. It just drives me insane.

01:15:16.400 Well, I think for the general community, I think it's an important question, even for practical

01:15:23.360 reasons, because you may be able to control your life to the extent that you can do all this at your

01:15:32.720 own convenience. But a lot of people don't have that flexibility. And so if they can be told that

01:15:40.820 fasting for X amount of time is all you need to do, then the beneficial effects of fasting could be,

01:15:49.560 there would be more people that could take advantage of it.

01:15:52.500 Absolutely. And if you look at the work of someone like Walter Longo, who his assertion is,

01:15:58.300 you can get most of the benefit without actually having to be fully fasted, but to do something that

01:16:03.260 is like a fast mimic, where you reduce your calories significantly for a period of five days.

01:16:08.260 Again, maybe he's right, but we have no idea. We have no idea what the efficacy of that approach

01:16:15.120 is versus a total water-only fast for five days. And it would be great to know, because

01:16:20.040 if we could demonstrate that you're getting 80% of the benefit doing a fast mimicking diet versus a

01:16:25.740 complete fast, well, that opens the door to many more people who would be willing to do fast mimicry

01:16:31.400 versus an outright fast. And again, I think about this constantly, which is, I'm almost willing to

01:16:37.980 do anything. I just want to know what to do. So I think that now is the right time to ask that

01:16:44.000 question. Let me just digress a little bit to talk about metabolism. So we know a lot about metabolism,

01:16:52.660 essentially the field of not only just cancer metabolism, but metabolism in general mapped out

01:16:59.640 all the metabolic, most of the metabolic pathways. But what we lack the ability to do until fairly

01:17:07.000 recently was to have a thorough understanding of metabolism in a living mammal. And so Joshua

01:17:14.920 Binowitz and I have invested a lot of effort in developing technology to use isotope tracers.

01:17:23.800 This would be C13 labeled glucose and amino acids and so forth. And to deliver them to living mice

01:17:32.880 running around and doing normal mice things in a cage, and then look to see how they're used and how

01:17:40.160 different tissues use them and how there's nutrients sharing between tissues. Because when you're

01:17:47.460 fasting, there's many complicated things going on. It's not just like there's no food and you're

01:17:54.880 inducing autophagy and that's that. That's the only thing that's happening in a vacuum, right?

01:17:59.500 So you have dedicated nutrient stores, you have glycogen in your liver that's mobilized,

01:18:04.620 and that's dumping glucose into the bloodstream. You have made out of post tissue that starts

01:18:11.300 degrading your triglycerides, and then you end up with glycerol and fatty acids in the bloodstream,

01:18:17.640 which then, you know, are taken up by the liver and so forth. So you have all these, you know, if you're

01:18:23.580 really without nutrients for a long time, then your muscle proteins start being degraded, which is

01:18:30.120 probably undesirable. That's dumping amino acids into the circulation so that you can maintain your

01:18:36.920 survival. We have to understand all of that. Because it really occurs in different phases.

01:18:43.320 Again, if we just limit it to humans for a moment where we have a pretty good understanding of this,

01:18:48.000 what's happening in the first 24 hours versus the next 24 hours versus the next 24 hours is very

01:18:53.060 different. And George Cahill's famous fasting study, the 40-day fast on the healthy subjects,

01:18:58.400 really divides it into these phases. What's interesting is by about seven days into a

01:19:05.220 prolonged fast, you pretty much reach a steady state. You've got a pretty consistent flux of

01:19:10.900 triglyceride into free fatty acid out of the fat cell. You reach a steady state level of beta

01:19:16.120 hydroxybutyrate, acetoacetate, and glucose, such that basically the sum total of them in millimolar

01:19:22.160 concentrations is about preserved to where you would be non-fasting-like. And so it begs the question,

01:19:28.660 if we posit that once you reach that steady state of seven to 10 days, you're clearly in a fully

01:19:34.680 turned on autophagy state, what's the switch look like? When you're 24 hours or 48 hours or 72 hours

01:19:42.720 into that, are you 80% of the way to the benefit or just 20%? That's a jugular question.

01:19:48.720 Yes. I think it would be fascinating to understand that. And I think that if you look back over

01:19:56.160 history, almost all cultures have fasting as part of their history. And I'm thinking that

01:20:05.080 that is not by accident. I think they must have learned by trial and error that this was a healthy

01:20:11.580 thing to do. And so I think that autophagy, I would expect is playing a major role in promoting health

01:20:20.340 in response to fasting. But I really think, well, maybe I'm sticking my neck out, but I think

01:20:26.440 using fasting as opposed to trying to find some pill you could take is something that's easy to do.

01:20:34.840 And of course, it speaks to the irony of it, which is if you took probably 1% of the budget that is being

01:20:40.900 dispensed to find pills that stimulate autophagy, we would actually be able to answer this question

01:20:46.240 clearly and actually just have a dose of response. And look, that doesn't mean these things can't

01:20:51.680 coexist. I'm all for it. And I wanted to ask you, of course, about some of the other pills like

01:20:57.320 rapamycin and metformin and the role that they might have and how we might be able to measure that.

01:21:00.800 But again, this just strikes me as the most obvious question in the space of how to prevent disease.

01:21:09.580 And it's like you have this beautiful, beautiful tool and you don't know what the dose is and you

01:21:16.800 don't know what the frequency is. If someone knows that they're susceptible to a neurodegenerative disease,

01:21:23.740 has anyone looked at those people to see if they engaged in some sort of fasting regimen,

01:21:31.800 whether that was helpful or not? Indirectly. I mean, it's possible that that's been done

01:21:37.040 directly and I just am not familiar with that. I think what we've seen indirectly is dietary

01:21:42.260 restriction as opposed to just pure caloric restriction where you improve the quality of

01:21:47.680 macronutrients, specifically around improving glycemic control. You can take people that are in an

01:21:53.680 early stage of cognitive impairment and delay it and or reverse it through that type of nutritional

01:21:59.260 intervention. Now, of course, that doesn't necessarily say autophagy is playing a role

01:22:03.640 because that's doing a lot of other things. It's improving glucose and insulin signaling in the

01:22:09.460 brain. It's doing a lot of other things and we're really starting to see the impact of metabolism in

01:22:14.000 the brain. So that's not entirely clear. Indirectly, I would say there are, I think, some pretty

01:22:20.200 interesting, compelling pilot data that suggests that rapamycin is neuroprotective. And again,

01:22:27.180 rapamycin, a very potent inhibitor of mTOR, would presumably on some level induce autophagy. I think

01:22:33.320 it's a very interesting question as to what is it about rapamycin that induces a longevity phenotype.

01:22:41.600 Rapamycin to me is the most interesting molecule out there because it is, I think, the only molecule

01:22:46.720 that has demonstrated a longevity benefit across all four models of eukaryotic cells. So that's a

01:22:53.860 really big deal that can't be ignored. But how much of that benefit is through autophagy? I'd like to

01:22:59.160 turn that question to you. How much of it is through inhibition of senescent cells, reduction of

01:23:04.940 inflammation? Again, so it's very indirect and it speaks to, again, I don't mean to sound like a

01:23:11.380 conspiracy theory guy because I'm not, but it is a little frustrating that we have these amazing

01:23:16.300 tools, but because they're not particularly profitable, you don't really have somebody

01:23:20.180 that's interested in answering them. And that's why I, again, come back to, A, I think these are

01:23:24.380 answerable questions. B, I don't think they are billion dollar questions. I think they are really

01:23:29.200 questions that are amenable to the philanthropic community. And I think from an ROI perspective,

01:23:34.920 it's hard to think of examples of where you could put dollars to work in research that would

01:23:39.520 have a greater impact on human life.

01:23:41.380 Right. And I think that our biomedical community is mostly focused on putting out fires rather than

01:23:50.980 disease prevention, although I've seen a change. I mean, I see at the NCI, the National Cancer

01:23:56.960 Institute, a bigger interest in cancer prevention. So I think people are coming around to realizing that

01:24:05.980 making people healthier longer is probably more important than once they discover to have stage

01:24:13.660 four pancreatic cancer, what can we throw at it to make them live another two months?

01:24:20.620 Yeah. Again, it is sort of amazing to me how lopsided our resource allocation is with respect to that

01:24:28.500 problem, because you're absolutely right. We have spent probably a quarter of a trillion dollars

01:24:34.960 in the last 40 years on the second question, which is once you have metastatic cancer, how do you live

01:24:42.360 longer? And we've done an analysis on this. So for the quarter of a trillion dollars that has been spent

01:24:48.080 on that problem on average for solid organ tumors, we have extended median survival by less than about

01:24:55.900 a year since 1970. So almost 50 years. That's pretty sad when you think about the fact that there's not

01:25:03.500 much evidence we've reduced the arrival of cancer. In fact, all we've done is basically come up with a

01:25:10.700 second leading cause of cancer in terms of modifiable behavior, which is after smoking. It

01:25:16.060 becomes down to diabetes, insulin resistance, and all of the metabolic dysregulation. So yeah, I'll get

01:25:22.080 off my soapbox now. But again, this is in many ways just a sort of a plea for help, which is I think

01:25:27.700 there's an amazing opportunity to understand this. So there's another component to this that worries me

01:25:33.980 greatly. So what we've seen, you know, so a lot of this, you're talking about controlling metabolism

01:25:42.400 to preserve health through implementation of fasting and understanding fasting. But look what's

01:25:49.740 happened to the American diet. I mean, there are people now that don't even recognize vegetables in

01:25:59.480 the supermarket. There are people that only eat prepared food. And so what we've seen is, on the

01:26:09.200 one hand, you're talking about preserving health and all that. But on the other hand, the overall

01:26:14.840 health of Americans is deteriorating. Obesity is greatly increased and has no sign of abating.

01:26:23.180 The diet of Americans loaded with high fructose corn syrup and diets that are disproportionate with

01:26:32.360 prepared food. So the only way to globally improve the health of Americans or anyone else for that

01:26:41.040 matter is to deal with both of these problems at the same time. And to me, that's probably the

01:26:46.880 greatest line of reasoning that says fasting is probably protective against all chronic disease.

01:26:53.900 Because if you look at the three main chronic diseases that account for, to our last analysis, 82%

01:27:01.660 of deaths above the age of 50 in the United States, excluding COPD. So if you take out the obvious

01:27:08.880 smoking-related death of COPD, 82% of death is attributable to cardiovascular disease, cancer,

01:27:15.540 Alzheimer's disease, and complications of diabetes. That's pretty stark. There's no question that when

01:27:23.980 you improve metabolic health, which you can do through fasting, you reduce the risk of all of

01:27:29.420 those significantly. Of course, the question becomes, how much of a role does autophagy play in

01:27:34.900 that? Specifically, you look at the example you gave of neurodegeneration. That makes a very compelling

01:27:39.920 case for it. Probably also in cancer. What do we know about cardiovascular disease, by the way?

01:27:44.540 Nothing comes to mind. I don't recall seeing anything in that area.

01:27:50.600 Yeah. I mean, my take on the literature is that the benefits of fasting in cardiovascular disease

01:27:58.060 are primarily mediated through the metabolic health benefits of it. Lower glucose, lower insulin,

01:28:04.880 lower homocysteine in time, lower inflammation primarily, as opposed to something that directly

01:28:11.480 pertains to ApoB or the inflammatory response to that. But again, maybe it's just there and I

01:28:17.620 haven't seen it. What else do you think is going on? What travels with autophagy? Can we talk about

01:28:22.700 senescence for a moment? Do we understand a sense of what's happening when an animal or a human is

01:28:27.240 undergoing autophagy with respect to either SASP or just the overall senescent cells?

01:28:33.660 Yeah. There seems to be complicated roles for autophagy and senescence. There's evidence from

01:28:41.780 the Noreta lab that SASP, the secretion of inflammatory factors that occurs during senescence

01:28:49.360 is facilitated by autophagy. But then in the cancer setting, there's also examples where

01:28:57.680 loss of autophagy limits senescence. So I think in the senescence area, it's still a little bit

01:29:05.320 confusing and maybe a little bit context dependent as to what's happening.

01:29:11.640 And then going back to the question about molecules, what do we know about metformin

01:29:16.360 and autophagy? Do we know that in a fed state, if we give an animal or a human metformin,

01:29:23.580 we can still induce autophagy, all things equal through just the AMPK activation?

01:29:28.820 Yes. And I think that that's true, but I think that we don't understand over the long term what

01:29:35.880 happens and what the consequence of having autophagy or not having autophagy is. So for example,

01:29:43.640 we've never given metformin to our mice that don't have autophagy. That might be an interesting

01:29:49.920 thing to do. What is the consequence of autophagy induction by metformin? It actually might be

01:29:57.520 better to do that in a system where autophagy could be, wasn't completely gone, but could be

01:30:05.940 toggled up. Do you have the ability to turn autophagy into an analog versus a digital,

01:30:12.760 meaning where you can actually use gradations versus just on or off?

01:30:17.120 Yes. I think the mouse model where autophagy, the expression of a central autophagy gene is

01:30:24.320 controlled by an shRNA might be the way to do that experiment.

01:30:29.000 And then what about rapamycin? What do we know about the use of rapamycin, which has been studied

01:30:36.040 so liberally across, again, everything from yeast, flies, worms, mammals, uniformly extends life,

01:30:42.680 potent inhibitor of mTOR, which would signal autophagy, all things equal. Where do we see

01:30:47.600 that relationship? So there's been a lot of discussion about using rapamycin or rapalogs

01:30:54.340 as autophagy stimulators, but it's like what you said before, it does many other things and

01:31:01.800 it's also immune suppressive.

01:31:03.880 Although that also depends on the dose, right? I mean, the Evrolimus data suggested that it was

01:31:09.020 actually immune enhancing when given intermittently.

01:31:12.300 I also have to remember that if you have a small molecule like rapamycin and you want to

01:31:18.480 use it to preserve someone's health, you have to make sure that it's safe. And I think that's when

01:31:26.360 everyone backs away. Because if you've got cancer and they want to try an experimental drug and you've

01:31:33.560 got no other hope and you're going to be dead in a short period of time, there's a bit of latitude in

01:31:41.240 what can be done clinically to test whether or not there's a small molecule or some sort of drug that

01:31:48.340 will be safe and possibly have efficacy. But when you're talking about prevention, it's a big problem.

01:31:57.520 The drug companies are not interested in it because the amount of time it would take in the risk of...

01:32:05.060 Right. Just a much narrower margin. By the way, that's exactly the reason we're in the situation

01:32:09.260 we're in. So just to reiterate, we have a situation where I am not convinced that longevity as a game

01:32:17.280 is going to be one on the back of extending the time you have a disease. I have never seen a shred

01:32:23.880 of evidence to suggest that that is the answer. Everything in humans and animals points to the

01:32:29.760 opposite end of the spectrum. Longevity is about delaying the time it takes until disease comes.

01:32:35.420 The implication of that is prevention is the single most important tool in the longevity toolkit.

01:32:41.220 How do we reconcile that with what you just said? All of our pharmacologic efforts,

01:32:46.140 the trillion dollars we spend on drug development is all on the wrong side of the equation.

01:32:53.200 It's on the how do you live longer once you have a disease? And I understand why that's the case

01:32:59.900 for all the reasons you just said. And if that doesn't make the most compelling case for taking

01:33:05.520 the best and safest drug of them all, which is fasting and understanding how to dose it and what

01:33:11.000 frequency to dose it, I don't know what makes a better case. Along with exercise, by the way,

01:33:14.820 I put exercise in that same category, which is it bothers me that we don't really know how to dose

01:33:20.140 exercise either. I mean, it's less of a problem, I think, because for most people, the issue is do

01:33:26.480 more, but it would be really nice to know what the dose response is on different types of exercise,

01:33:33.340 especially for people who want to do the minimum effective amount. So both from an exercise

01:33:37.840 perspective and a nutrient deprivation perspective, there's no more low hanging fruit

01:33:42.760 in terms of minimizing human suffering than understanding how these things work.

01:33:47.180 You should start a biotech company to do this.

01:33:49.980 David Sabatini and I have talked about this at length, and he has constantly told me to do this.

01:33:55.420 And the way we've thought about it, it's not going to happen because I won't do it.

01:33:59.480 So someone else will have to do it.

01:34:00.720 The way David describes it very eloquently is, right now, metabolic response to nutrients is

01:34:07.260 a black box. And what David thinks, and I think he's right, is there's a multi-billion dollar

01:34:13.440 opportunity in decoding the black box. In other words, when we understand exactly what the response

01:34:20.640 is to each different type of nutrient in every different dose and frequency, and we can decode that

01:34:26.540 in the way that we can do with so many other biochemical processes, you can do everything.

01:34:31.220 Because then you could actually develop drugs, probably, that could actually do something.

01:34:34.500 So there's a drug development platform that comes out of that. And then from my standpoint,

01:34:38.480 what I'm really interested in is simply just on the front lines as a sort of knuckle-dragging doctor,

01:34:43.820 how do you even just put this into clinical practice? But again, it's high risk. It's a lot of

01:34:48.900 effort to do part of that. I think on the drug development side, there's a lot there. I don't think

01:34:53.060 it's very high risk on the question I posed to you earlier. I think let's do the mouse study

01:34:58.860 and identify the 50 metabolites, proteomic signature things that are generally going up

01:35:07.180 with autophagy, and then let's shotgun that in an unbiased way against human subjects. I feel like

01:35:13.200 that's a project in the tens of millions of dollars, not even the hundreds of millions of dollars.

01:35:18.840 And again, if you add one year of life to each human as a result of that, that's kind of staggering.

01:35:25.420 Right. And I think if you couple understanding mechanisms of metabolic delay of damaging diseases

01:35:35.600 with surveillance for risk factors, I think those two things really need to be coupled together

01:35:44.080 because you can, even if you define what the optimal diet and exercise and fasting regimen is for

01:35:53.940 delaying the onset of disease, there are still unlucky people. And I think that we can't forget about

01:36:02.780 them in the context of health and longevity and well-being because you could have the healthiest diet

01:36:09.740 and do everything right. Vogelstein has written about this, right? I mean, there's clearly a

01:36:14.660 component, there's a stochastic component to this. And yeah, so absolutely. And again, I don't think

01:36:19.720 there's any reason to believe that we couldn't be addressing both of these.

01:36:22.500 Yes. I mean, I think that there's no reason to do everything. One always has to bear in mind that

01:36:28.960 there is this other risk factor that no matter what happens with understanding metabolism and fasting and

01:36:37.520 good health practices, that other thing is still going to be there. If you have a BRCA1 mutation,

01:36:44.660 that's a compounding and separate issue.

01:36:48.300 So in 2016, the Nobel Prize was awarded for basically the genetic elucidation of autophagy.

01:36:55.500 What are the salient features of that award? What was it about Osumi's work that led to that award?

01:37:00.940 So what Osumi did was quite profound and very creative. He developed an assay. Well, he asked,

01:37:08.920 what are the, I mean, yeast requires nitrogen for survival. And he asked, what are the genes that

01:37:15.040 are required for nitrogen survival? And he identified the autophagy, essential autophagy genes.

01:37:21.780 And I always wondered whether if he was in the United States, would work like that be funded?

01:37:29.580 Because it just seems like it was an important question, but-

01:37:33.860 It didn't have such a clear application down the line.

01:37:37.300 That's right.

01:37:37.580 It was a bit too high risk to fund.

01:37:40.060 Right. And also the clear disease connection wasn't there and so forth and so on. And nonetheless,

01:37:46.220 he did that. And I guess the point is, is that sometimes scientific discoveries are so basic

01:37:53.280 that you can't ever anticipate what it would ultimately lead to. And in this case, it led to

01:38:00.740 something very extraordinary, but he probably had no idea at the time. And once they discovered these

01:38:09.120 essential autophagy genes in yeast, then it was apparent that there were homologs in mammals and so

01:38:14.920 forth and so on.

01:38:16.220 How conserved are those genes between yeast and mammals?

01:38:19.600 If you do a blast search, you can see them. I mean, not all of them, but the amino acid homology

01:38:27.120 was compelling.

01:38:29.220 Wow. So when you sort of think about the future of this, I think so much of what we've talked about

01:38:35.060 kind of feeds into what your optimism is, but how do you want to spend the next 10 years of your

01:38:41.160 career? What are the questions you want to probe?

01:38:43.900 I think I would like to translate what we've learned about the role of autophagy in cancer.

01:38:52.720 And that involves developing small molecule inhibitors to inhibit autophagy for cancer therapy.

01:39:01.740 And Alec Kiliman and I started a company to do that. And what we're focusing on now is defining at the

01:39:12.080 molecular level what the functional requirements for autophagy are in individual cancers. And this

01:39:21.340 involves understanding the metabolic role of autophagy, why one cancer needs autophagy more than another.

01:39:28.160 And then the newest connection is the connection to inflammation. When you inactivate autophagy,

01:39:34.920 you stimulate inflammation. And this is what we've talked about earlier. In the context of cancer,

01:39:40.720 that could be a really good thing because the game changer in cancer therapy now is immune checkpoint

01:39:48.160 blockade. In fact, what I was just talking about at the ACR meeting yesterday was the particular

01:39:55.860 patient that came to our cancer center and went through surgery, radiation, chemotherapy,

01:40:03.620 and it all failed. And her body was riddled with tumors. And she went on a clinical trial

01:40:11.540 for immune checkpoint blockade and all the tumors melted away. And that was five years ago. And she's

01:40:18.120 perfectly fine. So what we have to do is make that work for everybody. And if inhibiting autophagy activates

01:40:26.820 the immune response and can facilitate not people who wouldn't respond to immune checkpoint blockade

01:40:34.200 to respond, then that would be critically important to do.

01:40:39.560 I mean, let me think about that for a second. So when we think about the patients that are responsive,

01:40:45.220 and we really have two big targets, right? CTLA-4 and PD-1. Melanoma obviously is a huge

01:40:53.580 success story here because it is so mutagenic. It's interesting. I have a friend who has Lynch

01:40:59.820 syndrome. So that's a familial syndrome where people are predisposed to cancer. He developed

01:41:05.580 colon cancer when he was quite young, went on to develop pancreatic cancer, adenocarcinoma of the

01:41:10.560 pancreas, which is uniformly fatal, almost without exception. He presented with an advanced state.

01:41:16.340 So he was not even a surgical candidate. So the tumor had completely engulfed his mesenteric artery

01:41:21.760 and vein, which meant he couldn't even undergo the surgical procedure, though it wouldn't have done

01:41:26.480 much anyway. I had just read a paper six months earlier in the New England Journal of Medicine

01:41:32.420 about, I forget what the paper was exactly about, but it made me think that because he had Lynch

01:41:40.080 syndrome and he has so many mutations, he might be a candidate for a checkpoint inhibitor.

01:41:45.000 So we went back to his oncologist and said, hey, can we get him on Keytruda? They said,

01:41:49.860 which is an anti-PD-1. They said, no, there's no standard for that. But we found a clinical trial,

01:41:56.600 actually got him in. He got Keytruda. That was five years ago. He's disease-free. So you go from

01:42:03.580 unresectable pancreatic adenocarcinoma to no pancreatic cancer. Pretty remarkable.

01:42:09.720 Now the question is, when I think about how broadly extendable that's going to be,

01:42:15.780 it really comes down to how many shots on gold do you get? How many mutations do you get

01:42:21.220 such that you can activate these checkpoint inhibitors? And so tell me how autophagy fits

01:42:27.500 into that, because I think I'm missing the link of why enhanced immune, non-specific immune response

01:42:35.160 would factor into that. I know there's a link, but I need you to explain it to me.

01:42:39.400 So that's exactly where we're going with our research.

01:42:43.420 I should have been at the AARC yesterday.

01:42:45.940 So we know that tumors with a very high mutation burden respond better to immune checkpoint blockade.

01:42:54.480 But it's not that simple, because there are patients with tumors that do have a high mutation

01:42:59.300 burden that don't respond, and we don't know why. It could be they've upregulated some other

01:43:04.820 checkpoint that we can't yet inhibit, or it could be some other reason they don't express class one,

01:43:10.720 or that the immune system can't see the tumor for some various reasons. And then we also know

01:43:17.340 there are tumors that have a low mutation burden that do respond.

01:43:20.800 Yeah. And so a big part, in fact, we just got an NIH grant to study this, is to make mouse models

01:43:30.020 of cancer with low, medium, and high mutation burden with which to study.

01:43:36.760 And then you can bang out autophagy.

01:43:38.740 Exactly. We haven't done the autophagy part yet. We're just generating the models using proofreading

01:43:46.440 mutations and polymerase epsilon and delta to generate mice with cancer with various levels

01:43:55.200 of mutation burden in their tumors. And this is so cool, because we'll be able to ask basic

01:44:01.800 questions like, how many mutations do you need? When you have a low mutation burden, what can you do

01:44:08.020 to make the immune system see that tumor? Do you need only mutations in the nuclear genome? What about

01:44:15.680 mutations in the mitochondrial genome? So one of the mouse models we made was to generate a mutator

01:44:23.700 phenotype in the mitochondrial genome. There are human cancers that have a high level of mitochondrial

01:44:30.500 genome mutations. Whether that has any effect on anything is completely unknown. There's no reason why

01:44:37.980 they couldn't be presented as tumor antigens.

01:44:41.860 And you'd think, if anything, they would be more immunogenic. I mean, they should be, all things equal,

01:44:47.600 just because of their bacterial origin. That should elicit a much greater immune response.

01:44:52.000 Exactly right. This is what this grant is designed to do, to generate mutator phenotypes

01:44:57.820 in mouse models of cancer, so we can have a spectrum from low to really high mutations

01:45:03.780 in the nuclear genome as well as the mitochondrial genome, then to figure out the mechanism of response

01:45:09.960 to immune checkpoint blockade to make cold tumors hot. And that's essentially what the loss of

01:45:17.640 autophagy is doing by promoting inflammation. It's taking a tumor that is not killed by T-cells,

01:45:24.920 that does not respond to immune checkpoint blockade, and rendering that tumor responsive.

01:45:30.540 And where do you put this in the hierarchy of optimism for the future of cancer therapy? I mean,

01:45:37.480 to me, the interesting stuff in cancer therapy is getting more and more targeted and stacking more

01:45:41.860 and more therapies on top of each other. So this is an elegant example of stacking something that is

01:45:47.780 clearly going to become a pillar of oncology, which is immune-based therapy, with something that,

01:45:53.980 frankly, is partially metabolic and, frankly, partially more complicated than just metabolic therapy.

01:45:59.920 So you've got, you almost add this to the layer of pieces of Swiss cheese you start to stack on top.

01:46:06.200 If you have enough of them, you're not going to be able to drop a pencil through. The cancer doesn't

01:46:09.240 survive. That's right. So one of the limitations that we have with immune checkpoint blockade is,

01:46:16.100 some of which I've already mentioned, we can't identify who's going to respond and who's not going

01:46:21.480 to respond, and we have to extend the responder pool. But we have to be able to model that,

01:46:28.800 because it's very clear that as single agents, there's going to be immune checkpoint blockade

01:46:34.540 therapy is not going to help most of the patients. So how do we go about optimizing this treatment?

01:46:43.400 And having models where you can combine immune checkpoint blockade with other therapies to

01:46:51.740 evaluate what is the optimal response is critical, and that's what we're doing. And whether fasting

01:46:59.120 influences this, it's completely unknown.

01:47:03.560 What's the role of autophagy in the immune cell itself? So either adaptive or innate? I mean, maybe both.

01:47:09.740 So we know that one of the things we did was to turn autophagy off in a mouse and ask how that affected

01:47:21.760 basic immune responses. And the answer was, everything in the short term appeared to be

01:47:28.940 completely functional. And if anything, the T cells were more anti-tumorogenic. But if you go into

01:47:37.760 the long term, if you knock out an essential autophagy gene, only in T cells, for example,

01:47:44.740 and look nine months later, I think those T cells are not going to be very functional.

01:47:49.740 But it really depends on how you design the experiment. For cancer therapy, we want to know

01:47:56.620 what happens acutely. When you're inhibiting autophagy, you're going to be looking at things in the

01:48:04.740 short term, not in the long term. So there's still a lot we need to do in that area. But in the short

01:48:13.180 term, for cancer therapy, the immune system seems to function well, if not better, in the presence of

01:48:22.040 autophagy inhibition.

01:48:23.340 And this just doesn't stop getting confusing. Because again, you would think that given the

01:48:31.540 benefits of autophagy and preventing cancer, one of them, you would think that that would only enhance

01:48:38.720 innate immunity because of the role innate immunity plays in cancer screening. Which again, I think just

01:48:44.740 speaks to we are still really scratching the surface of all of the different tentacles that come out of

01:48:54.320 these tools. Something like fasting seems very simple. And it's simple, of course, to do. But it

01:49:00.680 has such a set of pleiotropic extensions and benefits that it's very unlikely that it's about

01:49:08.520 all or none. There's nothing black and white here. It's really all these shades of gray

01:49:13.060 that it's not intuitive when you look at them what the net effect is, because it's a little bit of

01:49:18.640 this, a little bit of that, more of this than that. It's the balance of this versus that.

01:49:23.480 Yes, I would agree. And I think context is important too.

01:49:27.520 When you think of all the big chronic diseases, just based on what you've talked with us today

01:49:31.980 about, I think we have to be really excited about Alzheimer's disease based on the model you've

01:49:36.460 shared. I mean, that strikes me as an amazing opportunity because one, we don't have a single

01:49:43.400 tool. Once somebody has Alzheimer's disease, I'm sure you saw the most recent, I don't know if you

01:49:48.440 follow that literature, but we just saw two enormous failures in the anti-mammeloid beta drug trials.

01:49:56.040 So we're back to kind of square one, which is not a single drug that works for this condition.

01:50:00.380 If any disease demands prevention, it has to be this one. It's hard to make the case that fasting

01:50:08.540 isn't going to play a beneficial role there, isn't it? I believe you. I'd love to-

01:50:13.000 I mean, we have to test this now. Yeah, we have to test. It has to be tested. But I think that when

01:50:17.000 you look at the dramatic failures in preventing or delaying Alzheimer's disease, you have to ask the

01:50:25.720 question, what is the root cause of that? And if you look at the approaches, all the approaches are designed

01:50:33.840 to ameliorate a symptom. And the research has not yet gotten to the root cause. And I think that that is the

01:50:45.680 reason for these spectacular failures, is they're trying to treat a symptom of the disease, rather than the cause of

01:50:55.640 the disease. And when you look at the genes that are involved in neurodegeneration in general,

01:51:03.240 they fall into a broad array of different categories. And so my thinking is that they're all

01:51:10.600 doing different things, but there's some common denominator that has yet to be identified.

01:51:16.220 And I think that until the root cause of disease is identified, just finding means to ameliorate the

01:51:28.440 symptoms is not going to be productive. Eileen, you know, I could sit here and talk about this for

01:51:33.780 hours and hours. I want to be respectful of your time, because I know you've stayed an extra day to

01:51:38.060 have this discussion with me, which I really appreciate. Is there anything else you want to talk

01:51:41.720 about today, either as it pertains to your work, something you're excited about in the future,

01:51:47.060 or anything else that pertains to autophagy? I mean, I think that understanding in greater detail

01:51:54.460 how autophagy impacts metabolism, we've done some of that, but I think there's way more to do.

01:52:02.060 We have the technical ability to examine metabolic flux in a mouse in vivo, in normal, in starvation

01:52:11.260 conditions, and in response to different diseases. And we're only at the beginning of doing that.

01:52:18.400 And I think that that's something that we will continue to do, and hope that we can identify

01:52:25.060 new targets for anti-cancer therapy or signatures of metabolic problems. And we will continue to do

01:52:35.860 that. But again, I want to return to the immunotherapy. I think in the field of cancer,

01:52:41.600 building on that huge gain, we can't take our eyes off that ball.

01:52:48.760 Those are both very interesting. And of course, the former, it sounds like you really agree with

01:52:52.620 David Sabatini, which is there's an enormous opportunity to decode metabolism in a way that

01:52:59.020 we should have done 20 years ago. I think we lack the technology. I mean, I think that,

01:53:04.780 so maybe I could take a minute to explain what we do. And that by using C13 or N15 labeled tracers,

01:53:15.080 you can put them into a mouse, infuse a mouse with these tracers. And by looking at where they go by

01:53:24.660 mass spectrometry- Over different time points.

01:53:27.060 Over different time points. You can see metabolism. And that was something that was never possible

01:53:33.360 before.

01:53:34.360 What is it, because we've been able to label these things forever, what, was it the mass spec didn't

01:53:38.740 have the resolution before? Or what is it that, why is it we couldn't do this 20 years ago, I guess?

01:53:42.620 I think they could do it with radioactive material, and they could do it somewhat with

01:53:47.820 the technology they had way back when. But I think that the technology now is far more sophisticated.

01:53:55.200 By using heavy isotopes, you don't need radioactivity. Now there are more mouse models of disease. You

01:54:01.680 could even do this in humans. So Ralph D. Berardinas at UT Southwestern is infusing these isotope

01:54:10.200 tracers into humans with cancer and actually measuring the metabolism of human tumors.

01:54:17.400 Wow. That's interesting. I did an experiment once on myself with doubly labeled water, which of course

01:54:22.000 is a very simple version of doing that sort of thing to examine energy expenditure. I had a field

01:54:27.500 day doing that.

01:54:28.500 Wow. Yeah. But I think that, in fact, next week I'm supposed to go to a Keystone Tumor Metabolism

01:54:35.600 meeting where all the experts in this area will get together and talk about this in detail. But this

01:54:42.060 is a growing field. It's very exciting, and understanding metabolism in mammals at a level

01:54:52.120 we've never seen before in various disease states is tremendous.

01:54:56.900 And then lastly, is it safe to say that should there be a strong enough public demand and a

01:55:02.720 philanthropic demand to go after that question we talked about earlier about sort of decoding

01:55:08.620 the dose effect of fasting? Is that the sort of thing you'd be interested in working on?

01:55:13.100 Yes. I was fascinated by what happened when mice didn't have autophagy and they died when they

01:55:20.360 were fasted. And I am very much interested in fasting as a way to preserve health. I'm also

01:55:28.940 interested in, as I mentioned earlier, the dietary part, because I think all of this has

01:55:34.260 to go together. It's not just how many calories you eat or how often you eat them. It's what

01:55:40.020 they are. So yes, that's something that's very important to me.

01:55:45.020 Well, Eileen, thank you very much. This was super, super interesting. And I know that folks are

01:55:49.660 going to, this will probably pose a few more questions than, than even we had time to go

01:55:54.220 into, but that's great. Your work is fantastic and I appreciate your generosity.

01:55:58.400 Oh, this has been a lot of fun. I'm glad I took the time to do this.

01:56:02.160 Thanks.

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01:58:51.540 Thank you.

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The Peter Attia Drive - June 08, 2020

#114 - Eileen White, Ph.D.： Autophagy, fasting, and promising new cancer therapies

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