Evidence mounts that a single antibody could knock out many cancers

Willingham and Volkmer, along with pathology professor Matt van de Rijn, MD, PhD, showed that the anti-CD47 antibody could stop cancer from metastasizing, or spreading from the original tumor….

                                                http://stanmed.stanford.edu/2012summer/article7.html

“It’s no fun to manage a patient’s death,” says Stanford physician and researcher Ravi Majeti, MD, PhD, with grim and deliberate understatement. As a physician specializing in treating leukemia and lymphoma, Majeti is often required to perform that task with as much compassion and empathy as possible. In the case of acute blood cancers, even in young patients who undergo aggressive treatment, the odds of surviving more than five years is less than 50-50. For those over age 65, Majeti says, five-year survival rates are about 10 percent. 
What’s particularly frustrating is that these atrocious odds haven’t changed in decades, says Majeti, an assistant professor of hematology and a member of the Stanford Institute for Stem Cell Biology and Regenerative Medicine and the Stanford Cancer Institute. “The primary drugs and the combinations we use have not changed in 30 years. They have not,” he says. If a patient fails a first round of chemotherapy, it is difficult to halt the malignant blood stem cells from multiplying uncontrollably, crowding out nearly all the normal blood cells that protect us from infection, carry oxygen and clot to keep us from hemorrhaging. Lung infections are usually the ultimate cause of death, he says. 
In large part because of his frustration with these terrible and unchanging statistics, Majeti spends much of his time in the laboratory, looking for new ways to shift the odds in the patients’ favor. Some of his work involves taking samples of leukemia cells from patients in the hospital and putting them into mice to test new therapies. 
So it was with some small hope, on a day in November 2007, that Majeti tested a new antibody discovered in the laboratory of institute director Irving Weissman, MD. Majeti and MD/PhD student Mark Chao first injected a mouse with aggressive human acute myelogenous leukemia cells. This particular leukemia had, in fact, eventually killed the patient who donated a blood sample for research. Injected into a mouse, leukemic blood cells normally do the same thing they do in humans — multiply out of control until they kill the host. What happened next was one of the most astonishing moments in Majeti’s scientific career.
“For the first test, we were just guessing a dosage and hoping we could observe some small effect,” Majeti says. But there was no small effect — it was huge. A day after injecting the antibody, Majeti and Chao couldn’t observe any cancer cells in the mouse at all. “One dose, one day, and the cancer was gone,” Majeti says. At first Chao thought he had done something wrong, but there was no mistake. The same lethal cancer cells that could not be stopped in the human patient, the same cancer that was so irritatingly resistant to everything the doctors could throw at it in the clinic, had simply disappeared in the mouse after being exposed to a single dose of experimental antibody.
As dramatic as that experiment was, further research kept producing new amazements, suggesting that the applications of this antibody to cancer therapy are far broader and more powerful than anyone dared hope. The experimental antibody that Weissman and his collaborators discovered blocks a cell protein called CD47 — a cellular cloaking device that offers cancer safe passage from immune cells that eat damaged cells or foreign matter. 
Investigation into the role of CD47 began slowly 14 years ago in Weissman’s laboratory, but like a snowball kicked off a hilltop, it has picked up speed and mass as it has rolled along. It now seems on a course to blast through the traditional cancer treatment community. As the researchers prepare to test the treatment in humans, they have dared to hope that they’re on the trail of something many have dreamed about but most had begun to think impossible: a single therapy that uses our own immune system to effectively attack all cancers with almost no side effects.
The “don’t eat me” signal
It is the nature of life that things will go wrong eventually. Our cellular software, our DNA, can get damaged in many ways. Eventually “bugs” in that software accumulate, and cells stop following instructions written and revised over billions of years to make sure they do their proper jobs. One result of this process is cancer — cells that are supposed to behave within the rules of the body’s decorum begin breaking those rules and multiplying out of control. 
In 1998, Weissman and his postdoc David Traver, PhD, were crossbreeding mice with various genes that block programmed suicide in cells that have been damaged, genes that are known to be associated with cancer. They created a breed that was particularly prone to developing leukemia, then analyzed all the genes being manufactured (or “expressed”) by the blood-forming cells in these mice. “The first gene that we saw that was overexpressed in the mice that got leukemia was CD47,” Weissman says. In fact, it turned out that high levels of CD47 were common in every kind of leukemia, in mice and humans both. 
But no one knew what CD47 did. Then, two years later, a group in Sweden discovered that one role of the CD47 protein was to act as an age marker on red blood cells. They discovered that red blood cells start out with a lot of CD47 on their cell surface and slowly lose the protein as they age. At a certain level, the dearth of CD47 allows macrophages to eat the aging red blood cells, thus making way for younger red blood cells and a refreshed blood supply. CD47 thereafter became known as a “don’t eat me” signal to the macrophages.
For Weissman, the Swedish work and the work in his lab suggested an explanation for leukemia cells’ invincibility. Leukemia, which is a disease of excess production of specific sorts of blood cells, always features high levels of CD47. And CD47 naturally protects red blood cells from being cleared away by the immune system. Could blood cancer cells be boosting levels of CD47 to protect themselves from being consumed by macrophages?
Oddly enough, no one in Weissman’s lab was interested in looking for an answer to that question. Principal investigators with large labs generally don’t conduct experiments themselves, relying instead on an army of postdocs and students to do research under their direction. Weissman, unlike many principle investigators, doesn’t order people in his lab to carry out specific research, preferring instead to let them pick projects that interest them. “I’ve found over my career that the people I had to direct more closely never developed as scientists,” Weissman says. “Whereas those people who take on problems and figure out how to approach them go on to become accomplished scientists.”
So for three years, Weissman says, he found himself saying, “Come on you guys, how could it be more apparent? Every mouse leukemia has CD47, and CD47 is a ‘don’t eat me’ signal to macrophages. It has got to be important.”
Finally, in 2003, an MD/PhD student named Siddhartha Jaiswal took an interest. Jaiswal showed that human leukemias, like those in mice, also have elevated levels of CD47 on the leukemic cells. He also found another intriguing link with cancer. When blood-forming stem cells leave the bone marrow to move to another site, they dial up their production of CD47 to protect themselves against macrophages. The way these cells do this looks a lot like the way metastatic cancer cells move around the body and invade tissues. These and other experiments performed by Jaiswal showed that CD47 could indeed play an important role in blood cancers. “But showing that it’s possible is different than showing that’s what happens in real life,” says Jaiswal, who just completed his second year of residency in pathology in Boston. 
‘we started out small, but in the end we were giving mice really large doses of anti-cd47 antibody, and the mice were just fine.’        

If leukemia cells can use CD47 to protect themselves against macrophages, then the obvious next question is whether one can reverse that process. Could doctors get macrophages to eat leukemia cells by blocking the CD47 “don’t eat me” signal? Majeti, who at that time was still a postdoctoral researcher in the Weissman lab, decided he wanted to take on this project. Majeti identified an anti-CD47 antibody that would block the “don’t eat me” signal to the macrophages. He and Chao then mixed labeled leukemia cells with macrophages and the antibody. Under the microscope, they could see the marked leukemia cells inside the immune cells. In some cases, he could see macrophage cells in the act of eating the cancer cells. Blocking CD47 worked, at least in glassware. After these early tests, the two of them performed the dramatic experiments that showed the antibody worked in mice, too. 
When Majeti and his colleagues conducted a full series of experiments with human acute myelogenous leukemia in mice, they were able to totally eliminate the cancers in a majority of the mice. Ash Alizadeh, MD, PhD, another postdoc in the Weissman lab, found that CD47 was also present on non-Hodgkin’s lymphoma and performed a similar experiment. He, Majeti and Chao showed that the anti-CD47 antibody, combined with an FDA-approved antibody called rituximab, would eliminate aggressive human non-Hodgkins lymphoma in mice. Rituximab by itself does not. 
A magic bullet?
Killing cancer cells is not that hard. A little household bleach will annihilate the worst cancer doctors have ever encountered. But of course you can’t treat cancer with bleach. The trick to all cancer treatments is to harass, inhibit, contain, cut out, beat down and, you hope, kill cancer cells while simultaneously doing as little harm as possible to normal cells in the body. This is especially hard because cancer cells and normal cells are so closely related.
CD47 is not found only on cancer cells. The protein is also on many normal cells, and the obvious danger is that an anti-CD47 antibody would strip away the protective protein cloak from normal cells. Stephen Willingham, PhD, a postdoctoral scholar in the Weissman lab, took on the task of finding out if the use of the antibody would cause macrophage cells to attack normal tissue. If it did, that would rule out its use as a therapy, no matter how well it eliminated cancer cells.
“The experiments in mice are impressive, but they are rigged in a way because we are using a human form of the antibody against a human cancer, but we are doing it in a mouse,” Willingham says. “The humanized antibodies don’t attach to the mouse’s cells, so the mouse’s immune system won’t attack its own healthy tissue.”
A more fitting test of the safety of the therapy would be to use the mouse version of the anti-CD47 antibody in mice without cancer, which is exactly what Willingham did next. Luckily, these tests showed no major effects on normal tissues in the mouse. 
“We started out small, but in the end we were giving mice really large doses of anti-CD47 antibody, and the mice were just fine,” says Willingham. The only change was a temporary anemia as the mice’s red blood cell count fell (because declining CD47 is a sign of age in red blood cells, blocking CD47 makes the young red blood cells look old to the immune system, which eliminates them). But within days, the level of red blood cells in the mice’s bloodstream was back to normal. 
“It was actually amazing to me how little effect there was on normal tissue,” Willingham says.
Cancer’s ‘eat me’ signal
How could it be that blocking CD47 is so devastating against cancer but affects normal cells so little? If healthy cells also have CD47, why doesn’t blocking CD47 also lead to their destruction? The Stanford researchers hypothesized CD47 can’t be the whole story. Cancer cells must also have an “eat me” signal that normal cells do not carry. “It wouldn’t be likely that killing cells was the default action of the immune system,” Majeti says.
The idea that cancer cells would carry the seeds of their own destruction is not really surprising. Cells have many ways of signaling that not all is well inside them. For instance, specialized proteins inside cells carry bits and pieces of what they find to the cell surface and show it to circulating immune cells. If something is wrong inside the cell, the immune cells can then spot it. It’s a bit like a scenario in which parents sit outside their house chatting while the kids play inside. When the kids occasionally come to the window to show them a toy or game they are playing with, the parents know all is well. If a child comes to the window holding a severed human arm, the parents will know something is terribly amiss.
The genetic changes involved in making a cell cancerous disrupt its normal function, making it more likely that the cell will present signs of abnormality, the “eat me” signals that mark it for destruction. Warning signs like these actually make our bodies fairly adept at fighting errant cells. It’s likely that every one of us has had cells that are precancerous or cancerous, and that these cells have been effectively dealt with by our body’s defenses.
Majeti, Chao and Rachel Weissman-Tsukamoto — a high school student who is also Weissman’s daughter — took on the search for an “eat me” signal. They began to focus on a molecule called calreticulin as a possible “eat me” signal because other researchers had shown that it worked together with CD47 to regulate cell suicide. Indeed, the Stanford scientists found calreticulin on a variety of cancers, including several leukemias, non-Hodgkin’s lymphoma and bladder, brain and ovarian cancers.
“Our research demonstrates that the reason blocking the CD47 ‘don’t eat me’ signal works to kill cancer is that leukemias, lymphomas and many solid tumors also display an ‘eat me’ signal,” says Weissman. “The research also shows that most normal cell populations don’t display calreticulin and are therefore not depleted when we expose them to a blocking anti-CD47 antibody.”
Understanding how calreticulin and CD47 balance out each other’s influence in controlling how the immune system reacts to cancer is important because it can affect how anti-CD47 antibodies are used as a therapy. “If calreticulin is displayed in response to cell damage, you might not want to use anti-CD47 immediately after chemotherapy or radiation,” says Majeti. “These treatments can cause damage to normal cells, which might make them vulnerable to macrophage attack when CD47 is blocked.”
One treatment for all cancers?
One of the many frustrations of cancer is that each type can be so different. New drugs that seem to be effective against one type of cancer turn out to be ineffective against other types. Drugs like Gleevec are miraculous therapies for chronic myelogenous leukemia, but ineffective against acute lymphocytic leukemia. Researchers had high hopes for drugs that block the growth of blood vessels that tumors need, but one such drug, Avastin, while effective against colon cancer, turns out to be ineffective against breast cancer.
As Majeti and his colleagues investigated CD47’s role on leukemias, another team in the Weissman lab began to look at solid tumors. Willingham and Jens-Peter Volkmer, MD, a urologist who came from Germany to study stem cells in the lab, began looking at cancer tumor samples collected from patients at the hospital. They were astounded to find CD47 everywhere they looked. 
“When Stephen and I first started, we thought we might get lucky and find CD47 on a few tumors, but nobody expected that every kind of cancer we looked at would have high expression of CD47,” Volkmer says. The list of cancers with high CD47 levels ultimately reached 20 and could still be growing. The natural next step was to find out if the methods that were so successful in treating human leukemias could be replicated with solid tumors. 
Using collaborative relationships Weissman had built with oncologists at Stanford Hospital over a decade, Volkmer and Willingham obtained biopsies of human cancers, embedded those cancers in laboratory mice and then treated half the mice with the anti-CD47 antibody. As expected, in the untreated control group the samples of deadly, aggressive cancers of the breast, ovaries, colon, bladder, brain, liver and prostate grew rapidly. Special imaging shows how the cancers whipped like wildfire in the mice, starting as one dot of color but growing inexorably over weeks until they had spread throughout their bodies. But in the mice treated with the anti-CD47 antibody, clusters of cancer cells shrank or even disappeared. 
“If the tumors were large, then we could shrink them, but if the tumors were small, the antibody could eliminate them altogether,” Volkmer says.
Even more dramatic, Willingham and Volkmer, along with pathology professor Matt van de Rijn, MD, PhD, showed that the anti-CD47 antibody could stop cancer from metastasizing, or spreading from the original tumor. This finding is highly important because tumors can most often be cut out or controlled by focused radiation therapy when they restrict themselves to one site in the body. Many cancers become really deadly only once they start spreading the seeds of cancer throughout the body. 
“I think the most amazing moment in our research was when we saw that anti-CD47 antibody could stop the metastatic spread of cancers, and even treat cancers that had already metastasized,” says Willingham.
As amazing as it seems to the researchers, the CD47-blocking therapy looks as though it could be useful in combating almost every type of cancer (although not every individual cancer — a very small number of cancer samples seem to use other, unknown methods to escape macrophages). It may turn out to be most effective when combined with antibodies that reinforce the positive “eat me” signals from cell surface proteins like calreticulin. “The nice thing is that anti-CD47 antibodies should work with, and boost the effectiveness of, other treatments that use the immune system to fight cancer,” says Volkmer. 
With the help of a $20 million grant from the voter-funded California Institute for Regenerative Medicine, the Stanford researchers are pushing ahead with plans to begin human clinical trials of the therapy in late 2013 or early 2014. This will be none too soon for many current cancer patients and even the researchers, many of whom spend time treating patients when they are not conducting lab research. 
“We are tremendously excited about the potential of CD47 antibodies for improving the lives of our patients,” says Beverly Mitchell, MD, PhD, director of the Stanford Cancer Institute. 
Majeti remembers many of the patients who graciously donated their cancer cells for research, especially those patients whom he could not cure and who succumbed to their illness. He is sensitive to the cruel irony that in mice, he is able to defeat some of the very same leukemic cells that he could not vanquish in his patients.
“Working in the clinic is a very motivating thing,” Majeti says. “When I find myself in a situation that can’t be addressed clinically, I say, ‘We have got to get back to the lab and get on this.’”

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Calorie Restriction to Treat Cancer: The Time Is Now

Calorie Restriction to Treat Cancer: The Time Is Now
Nick Mulcahy
February 01, 2013
Cancer research history was quietly made at an American university in January.
For the first time ever, a randomized controlled trial that uses calorie restriction as a treatment for cancer — and measures a cancer-related outcome — was approved by the institutional review board at Duke University in Durham, North Carolina, and is on its way to the clinic.
“In the entire field of cancer research, there have only been a handful of studies of calorie restriction as a cancer treatment,” Stephen Freedland, MD, from Duke, told Medscape Medical News. But none of them were randomized clinical trials.
In what appears to be a manifestation of zeitgeist, the approval at Duke comes when single-group studies of calorie restriction as a cancer treatment are being planned (in breast cancer at Thomas Jefferson University in Philadelphia, Pennsylvania) or are underway (in pancreatic and lung cancer at the University of Iowa in  Iowa City).
Such clinical trials should be seen in a larger research context, explained an expert.
“During the past 10 years or so, interest in the metabolism of cancer cells has seen a dramatic increase, which is surely why interest in dietary interventions…has increased,” said Rainer Klement, MD, a radiation oncologist at the University Hospital of Würzburg in Germany.

The time is definitely ripe.

“The time is definitely ripe to test the various ways of altering cancer patients’ metabolism — be it through physical exercise, ketogenic diets, fasting, or calorie restriction. The combination of these lifestyle interventions with the standards of care seems very promising to me,” he wrote in an email to Medscape Medical News.
In 2011, Dr. Klement and a colleague published a review of the possible role of carbohydrate restriction in the treatment and prevention of cancer (Nutr Metab. 2011;8:75).
The hypothesis that suppressing carbohydrates could suppress or slow cancer growth is supported by a lot of laboratory science. The pair explain that complex carbohydrates are ultimately digested as glucose, which can cause tumor cells to proliferate.
“First, contrary to normal cells, most malignant cells depend on steady glucose availability in the blood for their energy and biomass-generating demands, and are not able to metabolize significant amounts of fatty acids or ketone bodies due to mitochondrial dysfunction,” they write. In other words, cancer cells thrive on glucose and starve on fats and ketones, which are food-derived energy units that are plentiful in low-carbohydrate diets.
The commonplace advice to avoid dietary fat is not a good recommendation to give cancer patients. “They should eat a lot of fat and avoid sugar,” Dr. Freedland noted.
The Duke study will involve calorie restriction in men with prostate cancer — specifically, cutting down on carbohydrates. The participants will have “failed” primary therapy for prostate cancer, as evidenced by a rising prostate-specific antigen (PSA) score after surgery, and will have experienced disease progression.
“No treatments have been shown to slow prostate cancer progression after radical prostatectomy. We hypothesize that a carbohydrate-restricted diet will slow prostate cancer growth,” the Duke researchers write in their trial description.
A projected 60 men will be randomized to either a low-carbohydrate diet (<20 g/day) or usual care. The outcome measure is PSA doubling time or change in PSA over the 6-month study period. The value of PSA in diagnosing prostate cancer is dubious, but in the treatment of men with diagnosed disease it is a well-established measure of disease progression and stabilization.
The Duke study, which is not yet enrolling patients and has a projected end date of 2016, is funded by the National Cancer Institute and the Atkins Foundation, which is a philanthropic outgrowth of the famed Atkins diet enterprise. The study will employ an “Atkinsesque” diet, said Dr. Freedland, which means carbohydrates are severely limited.
Calorie Restriction Along With Standard Treatment
The planned trial at Jefferson will employ a different calorie-restriction strategy, according to Nicole Simone, MD, a radiation oncologist.
“I have designed a clinical trial that will open at Thomas Jefferson University in the next few weeks. Early-stage breast cancer patients will undergo caloric restriction concurrent with radiation,” she told Medscape Medical News in an email.
In this case, the calorie restriction, which includes fasting, is expected to have a synergistic effect with an established treatment, explained Dr. Simone.
“We hypothesize that caloric restriction may augment the effect of cytotoxic targeted therapies in breast cancer, such as radiation, through an IGF-1R pathway-mediated mechanism,” she and her colleagues write in their project proposal.
They expand on just how calorie restriction might prime these breast tumor cells for destruction in a review published in the January issue of the Oncologist.
The Jefferson trial design calls for stage 0 and I breast cancer patients who are candidates for breast-conserving therapy to consume a liquid diet 36 hours prior to definitive surgery, and then a diet with a 25% calorie reduction during radiation therapy. Calorie restriction will start the week of radiation planning and continue for the 6 weeks of radiation, for a total of 10 weeks.
The primary end point of this feasibility study, which has the winning name of CAREFOR (Caloric Restriction for Oncology Research), will be acute toxicity. The secondary end points include progression-free and overall survival. If the combination of radiation plus calorie restriction does not add toxicity — Dr. Simone believes it might actually reduce it —  the researchers hope to eventually conduct a national multicenter study.
The Jefferson study shares some similarities with research being conducted at the University of Iowa, in which calorie restriction (a ketogenic diet consisting of high fat, adequate protein, low carbohydrates) is being administered at the same time as chemoradiation in separate trials of pancreatic cancer and lung cancer. The phase I trials aim to determine the safety and early efficacy of dietary manipulation during traditional therapy. “Preclinical data from mouse studies indicates a ketogenic diet increases tumor cell killing,” write the Iowa researchers in their project descriptions.
The trials are sponsored by the National Cancer Institute, the University of Iowa, and Nutricia North America, and will use the latter’s branded ketogenic diet in combination with standard therapy as the intervention.
Other Evidence
Extensive research suggests that restricting calories will improve cancer outcomes, according to Dr. Simone and  colleagues. More than 100 years ago, lab research first indicated that mice fed a calorie-restricted diet had “significantly slower” tumor growth than those fed their regular diet, they write.
Human data are also suggestive. Dr. Simone and colleagues explain that “multiple population-based studies of underweight patients have revealed a significantly lower cancer incidence than in the general population.”
Furthermore, obesity can lead to a higher risk for cancer, and prospective studies have demonstrated an association between obesity and cancer-specific mortality in multiple sites, they note.
The relation between insulin metabolism, obesity, exercise, and cancer has led to a recent surge of interest in dietary intervention during cancer treatment. “This is exemplified with newer trials, such as the National Cancer Institute of Canada MA.32 trial, which is treating early-stage breast cancer patients with standard therapy and randomizes them to placebo or metformin, which affects several metabolic pathways,” write Dr. Simone and colleagues.
Although a lot of research is underway or about to be underway, Dr. Simone still has evidence-based advice to share with her breast cancer patients.
“I discuss decreasing weight with all of my breast cancer patients. From recent literature, we know that most breast cancer patients gain weight during cancer treatment, and this has been linked to worse outcomes,” she said.
This research was supported in part by an NCI Cancer Center Support Grant. The authors have disclosed no relevant financial relationships.
Oncologist. 2013;18:97-103. Abstract

Medscape Medical News © 2013                     WebMD, LLC

Naturally Occurring Compounds Selectively Deplete Mutant P53 In Tumor Cells

Naturally Occurring Compounds Selectively Deplete Mutant P53 In Tumor Cells

Apr. 24, 2009 — Researchers at Lombardi Comprehensive Cancer Center at Georgetown University Medical Center have demonstrated that naturally-occurring compounds can selectively deplete mutant p53 and restore “wild type” function to p53 in a variety of tumor cells.

Mutations in the p53 tumor suppressor gene – which is involved in apoptosis and DNA repair – occur in about half of all human tumors.  p53 often acts as a checkpoint  preventing abnormal cells from continuing to grow and divide. However mutations in p53 gene are one way that pre-cancerous cells overcome normal cellular controls and replicate without restraint.
This study demonstrates for the first time that phenethyl isothiocyante (PEITC), a naturally-occurring compound, can selectively deplete mutant p53. The authors also made an intriguing observation that the depletion of mutant p53 in human cancer cells is accompanied by restoration of the wild type p53.  PEITC is a member of the isothiocyanate family compounds found in cruciferous vegetables, such as watercress, broccoli and cabbage. PEITC has been shown to have cancer preventive activity.
The researchers found that PEITC not only decreases the level of mutated p53 protein in tumor cells, but also restores the “wild type” or normal activity to mutated p53. The effect of this is that tumor cell lines with mutant p53 became more sensitive to PEITC-induced cytotoxicity than tumor cells with wild type p53, suggesting that the normal p53 checkpoint control pathways have been restored in the mutant p53-expressing tumor cells. This novel finding suggests that the PEITC and other compounds in the isothiocyante family could play important role in both cancer prevention and treatment of human cancers with mutant p53.

Copper Intake Makes Tumors Breathe

Copper Intake Makes Tumors Breathe

Copper in drinking water — given at the maximum levels permitted in public water supplies — accelerated the growth of tumors in mice. (Credit: © SEBASTIAN ZIELONKA / Fotolia)

Nov. 14, 2013 — Copper imbalances have been associated with a number of pathological conditions, including cancer. Publishing in PNAS scientists at EPFL have found that copper in drinking water — given at the maximum levels permitted in public water supplies — accelerated the growth of tumors in mice. On the other hand, reducing copper levels reduced tumor growth. The study strongly suggests that copper is an essential factor for the growth of tumors in humans as well.

Copper is a key player in cell growth. In order to proliferate, cells require energy, which they produce and store in the form of a molecule called ATP. Like all cells, tumor cells produce energy in two different ways: respiration, which requires oxygen, and glycolysis, which does not. Of the two, respiration is the more efficient way to make ATP. However it involves a number of enzymes, and one of the most important ones requires copper for its activity.
In a study led by Douglas Hanahan, researcher at EPFL and holder of the Merck Serono Chair in Oncology, scientists sought to examine the role of copper in cancer. To do this, they used genetically engineered mice with pancreatic neuroendocrine tumors. “This study was motivated by our previous puzzling observation; namely that cancers, unlike healthy tissues, are especially sensitive to changes in systemic copper levels,” said Seiko Ishida, the lead author of the paper.
Their research provides direct evidence that copper can enhance the proliferation of cancer cells. “The biggest surprise was that a small amount of copper added to drinking water accelerated the growth of tumors, indicating that copper is an essential nutrient for them, said Ishida.
Teaming up with Johan Auwerx, also at EPFL, the researchers found that copper insufficiency resulted in a lower activity of the respiration enzyme in tumors. PET scans also revealed that copper-deficient tumors took higher levels of glucose, suggesting that their cells were compensating more and more by using glycolysis rather than respiration for their energy. But despite this, ATP levels did not fully recover, and tumors did not grow further.
Importantly, the researchers do not think that copper causes cancer. Exposure of healthy mice to the same amount of copper via drinking water for up to two years did not result in an increased incidence of cancer. The authors suggest that copper levels could be monitored in cancer patients.

**** They propose that minimizing copper in the patient’s system may be beneficial in cancer therapy, especially when combined with drugs that block glycolysis. This two-step strategy would starve cancer cells — which tend to require much higher amounts of energy than normal cells — by limiting their two major pathways for ATP production.*****

Ketones and lactate increase cancer cell “stemness,” driving recurrence, metastasis and poor clinical outcome in breast cancer: achieving personalized medicine via Metabolo-Genomics.

Cell Cycle. 2011 Apr 15;10(8):1271-86. doi: 10.4161/cc.10.8.15330.
Ketones and lactate increase cancer cell “stemness,” driving recurrence, metastasis and poor clinical outcome in breast cancer: achieving personalized medicine via Metabolo-Genomics.

Source
The Jefferson Stem Cell Biology and Regenerative Medicine Center, Thomas Jefferson University, Philadelphia, PA, USA.

Abstract

Previously, we showed that high-energy metabolites (lactate and ketones) “fuel” tumor growth and experimental metastasis in an in vivo xenograft model, most likely by driving oxidative mitochondrial metabolism in breast cancer cells. To mechanistically understand how these metabolites affect tumor cell behavior, here we used genome-wide transcriptional profiling. Briefly, human breast cancer cells (MCF7) were cultured with lactate or ketones, and then subjected to transcriptional analysis (exon-array). Interestingly, our results show that treatment with these high-energy metabolites increases the transcriptional expression of gene profiles normally associated with “stemness,” including genes upregulated in embryonic stem (ES) cells. Similarly, we observe that lactate and ketones promote the growth of bonafide ES cells, providing functional validation. The lactate- and ketone-induced “gene signatures” were able to predict poor clinical outcome (including recurrence and metastasis) in a cohort of human breast cancer patients. Taken together, our results are consistent with the idea that lactate and ketone utilization in cancer cells promotes the “cancer stem cell” phenotype, resulting in significant decreases in patient survival. One possible mechanism by which these high-energy metabolites might induce stemness is by increasing the pool of Acetyl-CoA, leading to increased histone acetylation, and elevated gene expression. Thus, our results mechanistically imply that clinical outcome in breast cancer could simply be determined by epigenetics and energy metabolism, rather than by the accumulation of specific “classical” gene mutations.

We also suggest that high-risk cancer patients (identified by the lactate/ketone gene signatures) could be treated with new therapeutics that target oxidative mitochondrial metabolism, such as the anti-oxidant and “mitochondrial poison” metformin.

Finally, we propose that this new approach to personalized cancer medicine be termed “Metabolo-Genomics,” which incorporates features of both 1) cell metabolism and 2) gene transcriptional profiling. Importantly, this powerful new approach directly links cancer cell metabolism with clinical outcome, and new therapeutic strategies for inhibiting the TCA cycle and mitochondrial oxidative phosphorylation in cancer cells.

PMID:21512313   [PubMed – indexed for MEDLINE]

PMCID:PMC3117136         Free PMC Article

Metformin may antagonize Lin28 and/or Lin28B activity, thereby boosting let-7 levels and antagonizing cancer progression.

Med Hypotheses. 2012 Feb;78(2):262-9. doi: 10.1016/j.mehy.2011.10.041. Epub  2011 Nov 29.
Metformin may antagonize Lin28 and/or Lin28B activity, thereby boosting let-7 levels and antagonizing cancer progression.
McCarty MF.

Source
NutriGuard Research, 1051 Hermes Ave., Encinitas, CA 92024, USA.markfmccarty@gmail.com

Abstract

Cancer cells with stem cell characteristics are harbored by most tumors, and are characterized by epithelial-mesenchymal transition (EMT) – which promotes invasive growth and metastasis – chemoresistance, and the capacity to reconstitute new tumors. Hence, the control or destruction of cancer stem cells should be a major goal of cancer management. The let-7 family of microRNAs has cancer suppressor activity, and recent evidence suggests that markedly reduced levels of let-7 are not only a typical feature of cancer stem cells, but may be largely responsible for cancer stemness. It is therefore particularly intriguing that metformin, a diabetes drug thought to have potential in the prevention and treatment of cancer, has recently been found to oppose cancer cell stemness, to markedly potentiate chemotherapeutic control of cancer in mouse xenograft models, and to notably boost let-7a levels in cancer stem cells. It is proposed that this latter effect of metformin may reflect AMPK-mediated inhibition of the expression or activity of Lin28/Lin28A, proteins which act post-transcriptionally to decrease the levels of all let-7 family members.

The transcription of Lin28B is promoted by NF-kappaB and by Myc; hence, practical measures which antagonize NF-kappaB or Myc activity may complement the utility of metformin for boosting let-7 expression and controlling cancer stemness;

salsalate, antioxidants, tyrosine kinase and cox-2 inhibitors, ribavirin, vitamin D, gamma-secretase inhibitors (when available), and parenteral curcumin may have some utility in this regard.

Although the impact of histone deacetylase inhibitors on let-7 expression has not been assessed, there is reason to suspect that these drugs might complement let-7’s impact on chemoresistance, EMT, and stemness. Multifocal strategies centering on metformin may have considerable potential for reversing cancer stemness and rendering advanced cancers more susceptible to long term control.

Copyright © 2011 Elsevier Ltd. All rights reserved.

PMID:22129484      [PubMed – in process]

LIN28/LIN28B: an emerging oncogenic driver in cancer stem cells.

Int J Biochem Cell Biol. 2013 May;45(5):973-8. doi: 10.1016/j.biocel.2013.02.006. Epub 2013 Feb 16.
LIN28/LIN28B: an emerging oncogenic driver in cancer stem cells.
Zhou J, Ng SB, Chng WJ.

Source
Cancer Science Institute of Singapore, National University of Singapore, Singapore.csizjb@nus.edu.sg

Abstract

LIN28 (LIN28A) is a reprogramming factor and conserved RNA-binding protein. LIN28B is the only homolog of LIN28 in humans, sharing structure and certain function. LIN28/LIN28B has been identified to be overexpressed in a wide range of solid tumors and hematological malignancies. Blockage of let-7 miRNA biogensis and subsequent derepression of let-7 miRNA target genes by LIN28/LIN28B play important roles in cancer progression and metastasis. We will first provide an overview of LIN28/LIN28B gene and protein structures, followed by summary of the studies that showed their aberrant expression in primary human cancers and relevant clinical significance with emphasis on their roles in formation of cancer stem cells. Next, we will highlight the current knowledge of LIN28/LIN28B regulators and molecular mechanisms of LIN28/LIN28B-mediated oncogenesis. The potential medical applications for targeting LIN28/LIN28B will also be discussed in this review.
Copyright © 2013 Elsevier Ltd. All rights reserved.

PMID:23420006      [PubMed – indexed for MEDLINE]