One byproduct of blogging that I had never anticipated when I started is how it sometimes gets me interested in scientific questions that I would never have paid much attention to before or looked into other than superficially. One such scientific question is whether dichloroacetate (DCA), the small molecule that was shown to have significant anti-tumor activity against human tumor xenografts implanted in rats, media reports about which caused a blogospheric hysteria in late January representing DCA as a "cure" for cancer that "big pharma" doesn't want you to know about, mainly because it's relatively cheap and unpatentable in its present form. I gathered some minor notoriety by pointing out that the hype was excessive and that the drug had not even been tested against cancer in humans yet, adding that most drugs that show promise in cell culture and against experimental tumors end up failing to show efficacy in humans. Unfortunately, none of that stopped unscrupulous "entrepreneurs" from selling DCA as "Pet-DCA" supposedly intended for use "in pets only," even though the most cursory reading of the discussion boards revealed that desperate cancer patients are trying to buy it to use themselves, nor did it stop ignorant dupes like DaveScot from cheering them on in doing so or credulous bloggers who think far more of their scientific knowledge than is warranted from blathering about DCA as an allegedly "suppressed" or "ignored" cure like vitamin C.
It is not my purpose today to rehash all of this or to rail yet again against the dubious marketing of a "cure" that hasn't even been shown to be a cure yet. I'm more interested in discussing an interesting bit of science related to DCA and the whole concept that altered bioenergetics are important to the development of cancer.
The entire concept behind the use of DCA is to target a phenomenon known as the Warburg Effect. This effect was first observed by a biochemist named Otto Warburg back in the late 1920's in tumor cells. In brief, Dr. Warburg noted that tumor cells avidly consumed glucose and produced what is normally the byproduct of the anaerobic metabolism of glucose for energy (glycolysis) even in an aerobic (oxygen-containing) environment, conditions under which normal cells usually use a process that requires oxygen, oxidative phosphorylation. Normal cells usually use oxidative phosphorylation, which takes place in the mitochondria, when oxygen is available and only switch over to anaerobic glycolysis in conditions of low or no oxygen (anaerobic conditions), producing lactate as a byproduct. (Normally, the end product of glycolysis, pyruvate, is then used in the Kreb's cycle and oxidative phosphorylation. In the absence of oxygen, the pyruvate is used for energy and turned into lactate. Lactate buildup makes your muscles sore after intense exercise, when the energy demand of the muscles can exceed the amount of oxygen available.) The problem in normal cells is that glycolysis produces much less usable chemical energy per molecule of glucose than oxidative phosphorylation, and normal cells normally cannot survive on anaerobic glycolysis alone for very long. However, many tumor cells can. Indeed, many tumor cells continue to use glycolysis and produce lactate even in aerobic conditions, an observation that led Dr. Warburg to postulate that in tumor cells the mitochondria (which is where oxidative phosphorylation takes place) are reduced or functionally impaired. Indeed, he postulated more than that, namely that impaired mitochondrial function contributes to tumorigenesis.
The reason that I became more interested in DCA is because my main research interest is tumor angiogenesis. Because blocking tumor angiogenesis works by decreasing oxygen and nutrient delivery to tumors, in essence, "starving" them, one might imagine that one way in which tumors could be or become resistant to antiangiogenic therapy might conceivably be through cranking up the Warburg Effect, allowing tumor cells. As it turns out, DCA targets the Warburg Effect. It also turns out that the enzyme that DCA happens to inhibit to accomplish this targeting, pyruvate dehydrogenase kinase (PDK), is activated by a gene called HIF-1, which itself is activated by hypoxia. PDK inactivates an enzyme complex called the pyruvate dehydrogenase complex (PDH), which, when turned off attenuates mitochondrial respiration and oxidative phosphorylation.
Consequently, I've been checking out papers about the bioenergetics of tumors, and I found a doozy of one last week in the February 15 issue of Cancer Research, entitled Adaptation of Energy Metabolism in Breast Cancer Brain Metastases. Basically, the investigators found a fascinating (and disturbing) adaptation that occurs in breast cancer cells when they metastasize to the brain that shows just how unbelievably complex and difficult a foe cancer can be.
The investigators at the Scripps Research Institute led by Brunhilde Felding-Haberman asked the question: What are the changes in the amounts and types of proteins made by breast cancer cells that metastasize to the brain that make them able to grow there? To attack this question, they isolated tumor cells from the blood of a patient with stage IV breast cancer, cultured them, and then grew them into SCID mice (a strain of immune deficient mice in which human tumors can grow as xenografts). The tumors grew and, even more than that, they metastasized to brain and bone. Metastases from brain and bone were isolated, injected again into new mice, and then the metastases were isolated again. It turns out that the cells from the brain metastasis became much more likely to metastasize to to and avid for growing in the brain than the parental cell line from which they were derived, as the cells from bone metastases became more avid for bone. This is a common technique used to study metastasis and why certain tumors tend to metastasize to certain organs. Basically, tumor cells are subjected to one or more rounds of selection for clones that are able to grow in the organ desired.
Now here's where things get interesting. They next did a technique called multidimensional chromatography and tandem mass spectroscopy. There's no need to sweat the details other than to understand that this is a proteomics technique by which it is possible to simultaneously compare the levels of hundreds of proteins between cell types. Basically, the idea was to see which proteins were expressed at higher or lower levels in the brain metastases than in the parental cell line from which the metastatic cells were involved. The results were startling. In essence, the brain metastases made lots more of the proteins involved in oxidative phosphorylation.
In other words, they underwent what might well be characterized as the anti-Warburg effect. Although they had increased levels of glycolysis, they also cranked up their oxidative phosphorylation, as well as and had increased activation of pathways that minimize the production of or damage from reactive oxygen species (a.k.a. free radicals, the production of which was stimulated by treatment with DCA in the Michelakis experiments and contributed to tumor cell apoptosis in response to the drug). The overall effect of these changes in gene expression leading to increases in the enzymes responsible for oxidative phosphorylation is that the brain metastatic cell line became resistant to drugs that affect the cellular oxidation-reduction balance.
Drugs like DCA.
It's rather disappointing that they didn't actually test DCA, but, then, the work on this paper and the work on Michelakis' paper were likely going on at the same time. The drug they did test is 2-deoxyglucose (2-DG) a drug that is being tested because of its ability to inhibit glycolysis and shift the balance of energy production towards aerobic oxidative phosphorylation by a mechanism different from that of DCA. Consistent with the increased levels of proteins involved in oxidative phosphorylation, the cells derived from brain metastases were over two-fold less sensitive to 2-DG than the parental cell line, probably because the cells were no longer exhibiting the Warburg Effect, making them not nearly as dependent upon glycolysis for their energy. More than likely, these cells would also be as resistant to the effect of DCA.
The authors speculate that breast cancer cells that successfully metastasize to and colonize the brain take on characteristics that allow them to thrive in the environment found in the brain, and that their observations imply a link between a preference for oxidative phosphorylation and "homing" to the brain. The reason for this might well be that the brain is has a high blood flow and high oxygen tension, with the surrounding brain tissue always operating at a high oxidative metabolic level. As the authors state:
Our experimental metastasis data and proteomic analyses indicate that the brain metastatic cells, selected in vivo for their ability to establish brain metastases, possess a phenotype distinct from the parental circulating tumor cells and their bone metastatic counterparts. The protein expression profile of the brain metastatic cells and its functional validation imply a predisposition or bioenergetic adaptation of the tumor cells to the energy metabolism of the brain, conferring an advantage for tumor cell survival and proliferation in the brain microenvironment.
What these results suggest is something that those of us studying cancer have known for a long time. Cancer is an unbelievably devious and resourceful foe; if it weren't we'd be far better at curing it now than we are. As much as we would like to wish it to be so, there will almost certainly never be a "magic bullet" that will cure all cancers. Antiangiogenic therapy was touted as one eight years ago and, in the time since then, has shown only modest success against cancer. Certainly it was no magic bullet. My guess is that DCA (and drugs designed to target the Warburg Effect) will similarly show modest success against cancer in humans. My guess (and remember, it is just an educated guess) is that it may well be ineffective against many forms of brain metastases and against some forms of brain tumors, while being most effective against tumors that are most avid in taking up glucose, which happen to be the tumors that show up the most brightly on PET scans. However, more work needs to be done, as one glaring weakness of this study (and probably the reason that it wasn't accepted to a journal like Cancer Cell) is that the 2-DG experiments were all done in vitro. There were no experiments in which mice bearing brain metastases created by direct injection of either the parental cell line or the cell line derived from brain metastases were treated with 2-DG to see if in vivo results recapitulate in vitro sensitivities; so the tumor microenvironment could conceivably be sufficiently different than cell culture that these results might not hold up.
The bottom line is that cancer is always more complex than we think it is, and there are always wrinkles that we don't think of. Moreover, cancer cells are incredibly adaptable and--dare I say it?--evolve rapidly to infiltrate and colonize new environments. (Indeed one depressing possibility raised by these experiments is that drugs designed to target the Warburg Effect might actually select for cells able to metastasize to the brain.) An adaptation that allows tumor cells to grow in the brain appears to have the byproduct of eliminating the Warburg Effect and rendering them resistant to attempts to manipulate the energy balance.
Sadly, all too often, cancer is like that.
ADDENDUM: Walnut has posted his critique on Daily Kos as well.
All Orac posts on DCA:
- In which my words will be misinterpreted as "proof" that I am a "pharma shill"
- Will donations fund dichloroacetate (DCA) clinical trials?
- Too fast to label others as "conspiracy-mongers"?
- Dichloroacetate: One more time...
- Laying the cluestick on DaveScot over dichloroacetate (DCA) and cancer
- A couple of more cluesticks on dichloroacetate (DCA) and cancer
- Where to buy dichloroacetate (DCA)? Dichloroacetate suppliers, even?
- An uninformative "experiment" on dichloroacetate
- Slumming around The DCA Site (TheDCASite.com), appalled at what I'm finding
- Slumming around The DCA Site (TheDCASite.com), the finale (for now)
- It's nice to be noticed
- The deadly deviousness of the cancer cell, or how dichloroacetate (DCA) might fail
- The dichloroacetate (DCA) self-medication phenomenon hits the mainstream media
- Dichloroacetate (DCA) and cancer: Magical thinking versus Tumor Biology 101
- Checking in with The DCA Site
- Dichloroacetate and The DCA Site: A low bar for "success"
- Dichloroacetate (DCA): A scientist's worst nightmare?
- Dichloroacetate and The DCA Site: A low bar for "success" (part 2)
- "Clinical research" on dichloroacetate by TheDCASite.com: A travesty of science
- A family practitioner and epidemiologist are prescribing dichloracetate (DCA) in Canada
- An "arrogant medico" makes one last comment on dichloroacetate (DCA)
Posts by fellow ScienceBlogger Abel Pharmboy:
- The dichloroacetate (DCA) cancer kerfuffle
- Where to buy dichloroacetate...
- Local look at dichloroacetate (DCA) hysteria
- Edmonton pharmacist asked to stop selling dichloroacetate (DCA)
- Four days, four dichloroacetate (DCA) newspaper articles
- Perversion of good science
- CBC's 'The Current' on dichloroacetate (DCA)
My naivete about human physiology is clearly showing through here, but wouldn't DCA also seriously poison the metabolism of cardiac and skeletal muscle?
As I have indicated in the past when we discussed DCA and its effects on energy metabolism, this molecule is a derivative (toxic one) of acetate, a monocarboxylate that can be used as an energy substrate by astrocytes. Astrocytes are glial cells in the brain that usually fulfil housekeeping functions and protect neurones against toxic effects of certain excitatory neurotransmitters such as glutamate and aspartate (excitotoxins). There are several known toxins that are selective against astrocytes through interference with these cells' energy metabolism pathways. When astrocytes are eliminated, neurons usually lose the protection astrocytes provide them with. DCA could very well be one of those astrocytic toxins and may help rather than hinder brain cancer cells.
The weakened effect of 2-deoxyglucose on brain cancer cells in the study mentioned by Orac is interesting, since one must asks where the mitochondrial energy substrate of the cancerous cells come from when glycolysis is inhibited? Let's remember that for mitochondria to work efficiently, they must be provided with the glycolytic product, pyruvate, which originates from glucose. Thus, in the presence of 2-deoxyglucose, cancerous cells must be able to use other molecules as energy substrates (fatty acids?).
As a side bar; my main expertise is brain energy metabolism and as such I can attest to the fact that much of the classical formulation of the pathways of energy metabolism as presented in textbooks for the past 60 years is now being re-evaluated as more and more studies show that even glycolysis, the more primitive and much less efficient energy making pathway, had been somewhat wrongly formulated, especially in regard to its main aerobic end-product, pyruvate. There are indications that whether glycolysis is anaerobic or aerobic, its end-product is lactate rather than pyruvate, and that lactate is actually the substrate that mitochondria use for their oxidative phosphorylation.
Yes, several of the enzymes involved in fatty acid oxidation were expressed at higher levels in the brain metastases. Consequently, that's one possible explanation. In addition, I forgot to mention that one protein, AMPK, was also expressed at a much higher level. AMPK turns off fatty acid biosynthesis and turns on fatty acid oxidation and glycolysis. Also, remember that the cells were only less sensitive to 2-DG (by a roughly two-fold ratio), not totally insensitive to 2-DG. Consequently, it could be that, when glycolysis is inhibited by 2-DG, the cells can survive on fatty acid oxidation and whatever small amount of pyruvate is still being made.
Great post and a very timely article. I've also been thinking about DCA as a research question I wouldn't have delved into had I not been blogging and thought very simply about what all cancer pharmacologists do when a new drug is discovered: they select cancer cell lines that evolve resistance to the drug in question. The process is quite easy, given the inherent genetic instability of most tumor cell lines and give insight as to how a drug actually works. The proteomic angle of the Felding-Haberman group is great but I agree that it needs to be coupled with 2-DG or DCA in vivo.
As for Steven Chang, he was also over at my site talking about flavonoids but failed to produce any data when queried.
Yes, pyruvate can be produced from other sources than glycolysis, including, of course, fatty acids. 2-Deoxyglucose (2DG), over time, will inhibit glycolysis completely as it interacts with hexokinase, an enzyme that is being fooled by 2DG to phosphorylate it. 2DG-6-P occupies the next glycolytic enzyme in the pathway, phosphohexose isomerase, and brings glycolysis to a halt. Hence, under 2DG, most, if not all the energy supply would come from other sources than glucose.
I believe I have already found a potential cancer cure, using flavonoids.
For more info, please email:
schang1984REMOVETHIS@hotmail.com
remove REMOVETHIS
Steven,
You are on the wrong blog trying to sell your snake oil.
I'm not selling, I'm serious.
Steven,
It's brilliant marketing. Go on highly trafficed blogs discussing the flaws inherent in an alleged cancer cure, and then spam those blogs with another alleged cancer cure. I admire your thought process, if not your actual thoughts.
I've had enough. I'm banning the guy, as this isn't the first post that he's done this on. His comments will now all be moderated. If they have something substantive to say, I will approve them. If it's just more of the same, they will remain in my Spam Folder.
Interesting stuff. I'm actually struck by an odd thought: "If God had meant us to cure cancer, he would have made it easy!" Seriously, your description of the stubborn adaptivity of cancer made me wonder if some of the hyperactive alternative medicine market isn't driven by a sort of theological replacement issue. Cancer, in effect, has become the Satan of the modern world: sneaky, deadly, related to sin (and warded off by healthy lifestyles, sometimes) but not limited by it, implacable. The alternative therapies, etc., are indeed "faith-based" because they see cancer as evil not just a structural issue.
This raises all kinds of other issues: doctors as priests, etc.....
Beautiful post, Orac.
I would like to add to the topic saying that the Warburg effect and "lack of oxygen" are often used in fuzzy explanations on why an "oxygen therapy" could cure cancer. Many supplements on the market claim they can increase the "amount of oxygen in your blood" - some like microhydrin, based on the flamboyant quackery of Mr. Flanagan, others like hydroxygen plus (which had to change name) that are claimed to be able to "split water into simple H- and O-.
If oxygen were the magic bullet, we would not be posting about cancer right now...but people keep being bought into such things, no matter how hard one tried to disprove them logically.
Orac,
I also wonder if DCA might apply enough selection pressure to select for tumor cells that are better adapted to live in the brain. It wouldn't be much of a stretch (certainly less of a stretch than the DCA purveyors are making) to postulate that DCA might increase the risk of metastasis.
Just a happy thought.
Prometheus
I'm not a biologist, so what I'm about to write may be dumb.
As I read the news, DCA has a double take on the cancer cells. The one is the attack through the glycolytic metabolism, and the other is the activation of a mitochondrial apoptosis program. In fact, Michelakis seems to emphasis this later one in his interviews. Is this a total misunderstandig? Thanks.
I'm not surprised that a cancer cell can switch its energy source from glycolysis and back again, it is after all emryonic in origin, using many of the same genes and tricks as an embryo. The fetus runs on glycolysis, then switches to normal glucose use later on. Cancer is just a cell using fetal tricks to execute its program.
No I'm not Dave Scott.
I think my biggest complaint about folks who push "cure-alls" for cancer is addressed well here. I've wondered if terminology is the root of the problem for some people...the fact that there's one word for something as vastly complicated as cancer leads people to believe it can be cured like polio.
The differences still amaze me on a personal level. I lived with a LARGE giant cell tumor in my right hip for several months with (relatively) little damage to myself. (Apparently that type of tumor is extremely benign, and when it does metastasize, it does so in the lungs, for reasons I'm not sure are understood.) Yet a friend's mother was diagnosed with a pea-size breast tumor and it had spread through her body within a month. And I've talked to dozens of people, each with radically different stories.
(Yeah, I know, it's anecdotal, but even that's been enough to convince me to be wary of any supposed cancer 'cure' I've ever read or seen a news report about.)
"The overall effect of these changes in gene expression leading to increases in the enzymes responsible for oxidative phosphorylation is that the brain metastatic cell line became resistant to drugs that affect the cellular oxidation-reduction balance."
...and there will be those who will say blithely that this is not evidence that selection pressures can generate new information, or will claim that the selection applied here was 'artificial,' as if this in some unexplained way magically negates any possibility that the same sorts of changes could take place in response to 'natural' phenomena. (This is not to discount potentially significant differences the post points out between in vitro and in vivo environments.)
I'd like to rephrase my previous question, being not really neutral (sorry, if I seem to be offensive, last try, I promise). Michelakis' team has found that DCA attacked cancer cells in *two* ways:
(i) through glytolytic metabolism (Warburg effect); AND
(ii) by (suprise!) activating a mitochondrial pathway to cell apoptosis.
Seems to me, that it is different from other designated cures targeting just the starvation of cancer cells, as the synchronous apoptotic processes might successfully interfere with the well established adaptiveness of cancer cells.
Is this reconstruction a total crap, or has some meaning? Thanks (really).
If you read the paper in detail, it is explained how the apoptotic pathway is linked with the function of mitochondria. As I understand it, the increased oxidative stress from the reactivation of the mitochondria and increased production of NADH can lead to activation of the mitochondrial apoptotic pathway. Indeed several of the proteins involved in apoptosis are mitochondrial. That's one reason why targeting the Warburg effect in general can lead to apoptosis. 2-DG treatment can also lead to tumor cell apoptosis.
Thank you. (It's not me. That would be all right.)
I wish there were more people here sharing real DCA-Cancer self test results.
Patient: Woman, 65, Lungs cancer, brain cancer, spread in many other parts of the body, even visible on the ouside. Doctors not sure where it started anyway. Stage IV. Given weeks to live. Went 3 chemios, 2 radiation sessions, brain operation - some tumors shrank after that for 4 months, now growing again. Patient will not survive another Chemio.
Will receive 50mg/kg/day in drinking water for first week, with 500mg B1.
after first week will recive 25mg/kg/day with 500mg B1
I got DCA from Cole Parmer.
If anyone has any GOOD reason why I should stop - let me know now. Otherwise I will keep you all updated as we go along. Please share all you can.
It is my understanding that a lot of tumors are hypoxic, and that hypoxic tumors are more difficult to treat than non-hypoxic ones.
If there isn't enough O2 (or mitochondria) available to oxidize lactate, I think that it gets used as a substrate to make stuff with, ie fat or ectopic fat. Most cells derive lots (or even most) ATP from glycolysis. It is only highly metabolicly active tissues like muscle, liver, heart, brain and kidney that have lots of mitochondria and that mostly rely on oxidative phosphorylation.
The flux of lactate in the body is quite high, comparable to that of glucose. Most of the metabolic studies were done on healthy college students, with intact livers, kidneys and in good health. Some of what is in the literature on metabolism might not pertain as closely to people under metabolic stress, diabetics, metabolic syndrome, chronic fatigue, and the various degenerative diseases.
What we need to remember about cancer cells, is that typically they have genetic deletions, and so are actually "less complex" than "normal cells". That when "normal cells" have massive deletions and yet are extremely difficult to kill, shows how complex and redundant normal cells actually are.