Archive for November, 2008

SAN DIEGO, CA — Green tea is high in the antioxidant EGCG (epigallocatechin-3- gallate) which helps prevent the body’s cells from becoming damaged and prematurely aged. Studies have suggested that the combination of green tea and EGCG may also be beneficial by providing protection against certain types of cancers, including breast cancer. A new study conducted by researchers at the University of Mississippi researchers now finds that consuming EGCG significantly inhibits breast tumor growth in female mice. These results bring us one step closer to better understanding the disease and potentially new and naturally occurring therapies.

The study was conducted by Jian-Wei Gu, Emily Young, Jordan Covington, James Wes Johnson, and Wei Tan, all of the Department of Physiology & Biophysics, University of Mississippi Medical Center, Jackson, MS. Dr. Gu will present his team’s findings, entitled, Oral Administration of EGCG, an Antioxidant Found in Green Tea, Inhibits Tumor Angiogenesis and Growth of Breast Cancer in Female Mice, at the  121^st Annual Meeting of the American Physiological Society (APS; www.the-APS.org/press), part of the Experimental Biology 2008 scientific conference.

The Study

Epidemiological studies suggest that green tea and its major constituent, EGCG, can provide some protection against cancer. Because these studies were very limited, the anti-cancer mechanism of green tea and EGCG was not clear. As a result, the researchers examined whether drinking EGCG (just the antioxidant infused in water) inhibited the following: expression of VEGF (vascular endothelial growth factor, which is found in a variety of breast cancer types); tumor angiogenesis (thought to help tumors expand by supplying them with nutrients); and the growth of breast cancer in female mice.

Seven week old female mice were given EGCG (25 mg/50 ml) in drinking water for five weeks (approximately 50-100 mg/kg/day.) The control mice received regular drinking water. In the second week of the study mouse breast cancer cells were injected in the left fourth mammary glands of the mice. Tumor size was monitored by measuring the tumor cross section area (TCSA). Tumors were eventually isolated and measured for tumor weight, intratumoral microvessel (IM) density (using staining), and VEGF protein levels (using ELISA).

At the end of the five week period the researchers found that oral consumption of EGCG caused significant decreases in TCSA (66%), tumor weight (68%), IM density 155±6 vs.111±20 IM#mm^2) and VEGF protein levels (59.0±3.7 vs. 45.7±1.4 pg/mg) in the breast tumors vs. the control mice, respectively (N=8; P<0.01).  Further, VEGF plasma levels were lower in EGCG mice than in control mice (40.8±3.5 vs. 26.5±3.8 pg/ml P< 0.01).

Dr. Gu, the senior researcher for the study, hypothesized that the reason for the link between EGCG and the reductions in the cancer data was because EGCG directly targets both tumor blood vessels and tumor cells of breast cancer for suppressing the new blood vessels formation in breast tumor, the proliferation and migration of breast cancer cells.

Gu concluded by saying, “In this study we have demonstrated that the frequent ingestion of EGCG significantly inhibits breast tumor growth, VEGF expression and tumor angiogenesis in mice. We believe our findings will help lead to new therapies for the prevention and treatment of breast cancer in women.”

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (APS; www.The-APS.org/press) has been an integral part of this discovery process since it was established in 1887.

by Dianne C. Witter

Dr. Aggarwal is conducting laboratory studies on the apparent anticancer activity of curcumin, which is the main ingredient of the curry spice turmeric.

Razelle Kurzrock, M.D., rigorously evaluates the laboratory data behind any new pharmaceutical agent she considers moving into clinical trials at M. D. Anderson Cancer Center. As a physician, she is cautious; as a scientist, she’s a skeptic; she wants unbiased, evidence-based information. And that, to her own surprise, is how she became interested in studying curcumin—the primary ingredient of the curry spice turmeric—as a possible anticancer agent in humans.

“Dr. Bharat Aggarwal, chief of the cytokine research laboratory in the Department of Experimental Therapeutics, came to me and said, ‘I want to show you some great results we’ve gotten in the lab with an exciting new agent,’” said Dr. Kurzrock. “But he wouldn’t tell me what the agent was—he wanted me to see the data first.”

Dr. Kurzrock, professor in and chair ad interim of M. D. Anderson’s Department of Investigational Cancer Therapeutics (formerly the Phase I Clinical Trials program), was impressed with the data. “It was clear that this agent was just as potent at killing tumor cells in the lab as any experimental drug I’d seen from pharmaceutical companies,” she said. When Dr. Aggarwal told her this active agent was curcumin, she was intrigued and began designing a clinical study to test curcumin’s efficacy in humans.

Shutting down the master switch

Curcumin’s anti-inflammatory properties have been valued in Eastern medicine for centuries, but its specific mechanism of action has only recently been identified. In 1995, Dr. Aggarwal and colleagues demonstrated that curcumin shuts down nuclear factor kappa B (NF-kB), which is involved in the regulation of inflammation and many other processes.

By blocking the activity of this “master switch,” curcumin appears to interfere with the cancer process at an early point, impeding multiple routes of development: reducing the inflammatory response, inhibiting the proliferation of tumor cells, inducing their self-destruction, and discouraging the growth of blood vessels feeding tumors. These effects can shrink tumors and inhibit metastasis. Furthermore, shutting down NF-kB can enable traditional chemotherapy drugs to destroy cancer cells more effectively.

Hundreds of laboratory studies by Drs. Aggarwal and Kurzrock and others have demonstrated that curcumin is biologically active against many types of cancer cells—melanoma, and breast, bladder, brain, pancreatic, and ovarian carcinomas, to name just a few. “In the lab, we haven’t yet found a type of cancer it doesn’t show activity against,” Dr. Aggarwal said.

While it’s a long road from lab to clinic, Dr. Aggarwal sees promise in curcumin both as a possible preventive agent and as a cancer treatment. As a medicinal agent, its potential extends far beyond cancer. Laboratory studies have demonstrated curcumin’s promise in a number of different diseases that are also affected by inflammation, including arthritis, inflammatory bowel disease, Alzheimer’s disease, diabetes, cardiovascular disease, autoimmune diseases, and others. In light of these findings, the number of clinical studies of curcumin has grown substantially in the past few years and continues to rise.

Studying activity in cancer patients

The clinical research on curcumin in cancer is new but promising. Early studies at M. D. Anderson and elsewhere have shown curcumin to be well tolerated and non-toxic at high oral doses.

Dr. Kurzrock is designing clinical trials of curcumin, based on promising lab results.

Dr. Kurzrock and colleagues recently conducted a trial of curcumin in 49 patients with advanced pancreatic cancer, which is notoriously resistant to treatment. Two of those patients had clinically meaningful responses and remained stable for 8 months and more than 22 months, respectively. Another had a brief but dramatic response (73% reduction in tumor size).

“In advanced pancreatic cancer, the response rate to the Food and Drug Administration-approved treatments is only about 5%, so we were very encouraged that we saw any activity at all in this group,” said Dr. Kurzrock. “That tells us curcumin does have biologic activity in pancreatic cancer—there was a true antitumor effect. It’s too soon to know if it will affect survival rates, but more study is definitely warranted.” The fact that some patients benefited is encouraging, since there were questions about whether therapeutic concentrations could be achieved with oral administration.

To address the issue of absorption, Dr. Kurzrock is leading the development of an intravenous, liposome-encapsulated delivery system for curcumin that she says has so far been “very potent” in the lab. Liposomal curcumin would be given intravenously, thereby circumventing the problem of poor absorption.

“The fact that the curcumin did show some activity in the study even though it was poorly absorbed suggests that if we can develop a more effective method to get it to the tumors, it may well have promise as an anticancer treatment,” said Dr. Kurzrock. She hopes to have the liposome-encapsulated delivery system ready to test in a phase I clinical trial for patients with a variety of cancers in 2008. Whether the intravenous formulation would have more side effects in patients because of the higher blood levels of the agent is not yet known, but preliminary testing in mice has shown no toxicity, even at maximum doses.

Currently under way at M. D. Anderson is a clinical trial of curcumin in multiple myeloma, and researchers are seeking funding for a trial in breast cancer. Trials of curcumin in colorectal cancer and in myelodysplastic syndrome are in progress at other institutions. Curcumin is also in clinical trials as a treatment for non-cancer diseases such as Alzheimer’s disease, arthritis, and psoriasis.

Food for thought

Dr. Aggarwal, for one, is not surprised at the evidence that curcumin may have efficacy in treating cancer. He feels curcumin has the potential to one day be an inexpensive and nontoxic alternative to harsher oncology drugs; a chemopreventive agent; and an adjunct to chemotherapy. But he notes that progress in developing curcumin for medical use is likely to be much slower than for pharmaceutical agents because curcumin can’t be patented on a broad scale and therefore is unlikely to attract the interest and the funding of pharmaceutical companies.

For his part, Dr. Aggarwal takes a curcumin tablet every day, and he offers this food for thought: “The combined rate of the four most common cancers in the United States—lung, prostate, breast, and colon—is at least 10 times lower in India, where curry is a staple in the diet.”

For more information, call Dr. Aggarwal at 713-794-1817 or Dr. Kurzrock at 713-794-1226.

Scientists at Dana-Farber Cancer Institute have identified a previously undetected trigger point on a naturally occurring “death protein” that helps the body get rid of unwanted or diseased cells. They say it may be possible to exploit the newly found trigger as a target for designer drugs that would treat cancer by forcing malignant cells to commit suicide.

Loren Walensky, MD, PhD, pediatric oncologist and chemical biologist at Dana-Farber and Children’s Hospital Boston, and colleagues report in the Oct. 23 issue of the journal Nature that they directly activated this trigger on the “executioner” protein BAX, killing laboratory cells by setting in motion their self-destruct mechanism.

The researchers fashioned a peptide (a protein subunit) that precisely matched the shape of the newly found trigger site on the killer protein, which lies dormant in the cell’s interior until activated by cellular stress. When the peptide docked into the binding site, BAX was spurred into assassin mode. The activated BAX proteins flocked to the cell’s power plants, the mitochondria, where they poked holes in the mitochondria’s membranes, killing the cells. This process is called apoptosis, or programmed cell death.

“We identified a switch that turns BAX on, and we believe this discovery can be used to develop drugs that turn on or turn off cell death in human disease by targeting BAX,” said Walensky, who is also an assistant professor of pediatrics at Harvard Medical School.

BAX is one of about two dozen proteins known collectively as the BCL-2 family. The proteins interact in various combinations leading to either the survival of a cell or its programmed self-destruction. Cancer cells have an imbalance of BCL-2 family signals that drives them to survive instead of dying on command.

The late Stanley Korsmeyer, MD, an apoptosis research pioneer and Walensky’s Dana-Farber mentor, had suggested that killer proteins like BAX could be activated directly by “death domains,” termed BH3, contained within a subset of BCL-2 family proteins. He hypothesized that this activating interaction was a fleeting “hit-and-run” event, making it especially challenging for scientists to study the phenomenon.

As suspected, the proposed BAX-activating interactions could not be captured by traditional methods. “When you tried to measure binding of the BH3 subunits to BAX, you couldn’t detect the interaction,” explained Walensky. He recognized, however, that the BH3 peptides being used in the laboratory didn’t retain the coiled shape of the natural BH3 domains that participate in BCL-2 family protein interactions. Walensky and his colleagues pioneered the design of “stapled” BH3 peptides, which contain a chemical crosslink that locks the peptides into their natural coiled shape. With biologically active shape restored, the stapled BH3 peptides bound directly to BAX and triggered its killer activity.

Defining how the activating peptides docked on BAX remained a formidable catch-22. In order to solve the structure of an interaction complex, it needed to be stable enough for analysis. In this case, the BH3 binding event itself triggers BAX to change its shape and self-associate to perform its killer function, rendering the activating interaction unstable by definition.

What if, Walensky proposed, you could set up the interaction of BH3 and BAX under laboratory conditions that caused it to be more stable or proceed in slow motion? The plan was to adjust the potency of the stapled BH3 peptide so that, according to Walensky, “it was good enough to bind BAX, yet activate it just a bit more slowly so that we could actually study the interaction.” The researchers would then look for any detectable shift in the three-dimensional structure of the BAX protein to help point them to the docking site.

The researchers used nuclear magnetic resonance (NMR) spectroscopy to monitor the arrangement of atoms in the protein. First authors of the Nature paper Evripidis Gavathiotis, PhD, of Walensky’s laboratory and Motoshi Suzuki, PhD, of Nico Tjandra, PhD,’s laboratory at the National Institutes of Health, succeeded in generating pure BAX protein that could be put into solution with the stapled BH3 peptide — the latter in increasing concentrations until it initiated a BH3-BAX interaction. Gavathiotis and Suzuki used the NMR technique to spot a group of BAX amino acids, the building blocks of proteins, which were affected by the addition of the stapled BH3 peptide.

“The discrete subset of amino acids that shifted upon exposure to the stapled BH3 peptide mapped to a completely unanticipated location on BAX,” said Walensky. The long-elusive binding site on BAX that initiates its killer activity was revealed. “Because BAX lies at the crossroads of the cell’s decision to live or die, drugs that directly activate BAX could kill diseased cells like in cancer and BAX-blocking drugs could potentially prevent unwanted cell death, such as in heart attack, stroke, and neurodegeneration,” said Walensky.

Additional authors include Marguerite Davis, Kenneth Pitter, Gregory Bird, PhD, and Samuel Katz, MD, PhD, of Dana-Farber, and Ho-Chou Tu, Hyungjin Kim, and Emily H.-Y. Cheng, MD, PhD, of Washington University School of Medicine, St. Louis.

BRUCE MIRKIN WASHINGTON

ONCE AGAIN the cancer diagnosis of a well-known national figure — in this case Sen. Ted Kennedy — has sparked a flurry of interest in efforts to treat and cure this frustrating, complex and deadly illness. One of the most promising areas of research involves a group of chemicals whose origins may seem shocking.

The chemicals, called cannabinoids, are the active components in marijuana.

Yes, marijuana, the very same drug that seems to generate endless controversy here and abroad, and that our government still claims causes cancer — a claim that appears to stand reality on its head.

The first solid data showing the anti-cancer effects of cannabinoids was developed by U.S. government researchers and published in the Journal of the National Cancer Institute back in 1975. The scientists found that THC, the component that produces marijuana’s “high,” inhibits the growth of lung-cancer cells in the test tube and in mice.

In a world that made sense, this discovery would have set off a frenzy of new research. After all, President Richard Nixon had declared “war on cancer” just a few years before, and vast sums of money were being spent investigating new approaches. But Nixon had also declared “war on drugs,” with marijuana at the top of the demon-drugs list, so our government — by far the world’s largest source of medical research funding — never pursued these remarkable findings. Research ground to a near-complete halt until the late 1990s.

Since then, THC and other marijuana components have been shown to block growth not only of lung tumors but a variety of other cancers, including leukemia, lymphoma and cancers of the breast and skin. These effects seem to occur through a variety of different cellular mechanisms.

As Spanish researcher Dr. Manuel Guzman, one of the world’s leading experts in the field, wrote in a 2003 review in the journal Nature Reviews: Cancer, “Cannabinoids are selective anti-tumor compounds, as they can kill tumor cells without affecting their non-transformed counterparts. It is probable that cannabinoid receptors regulate cell-survival and cell-death pathways differently in tumor and non-tumor cells.”

That is exactly what you want in a cancer drug: Something that kills the malignant cells without harming healthy cells. It’s because most chemotherapy drugs aren’t selective enough that they cause such terrible nausea, vomiting, hair loss and other side effects.

One of the most fruitful areas of research has involved gliomas, the same type of brain tumor that Sen. Kennedy is battling. A search of PubMed, the U.S. government’s medical database, using the search terms cannabis (the scientific name for marijuana), cannabinoid, and glioma turned up 94 scientific-journal articles, most of them published since 2000.

Most are lab or animal studies, demonstrating various mechanisms by which these marijuana chemicals kill glioma cells or stop glioma tumor growth. Amazingly, despite all this evidence, there has been only one, tiny, human study thus far, conducted by Dr. Guzman.

Guzman and colleagues injected THC directly into brain tumors in a handful of patients with recurring, inoperable gliomas — patients considered terminal. It was primarily a safety study, and the THC injections proved completely safe.

Although the researchers concluded that the injection method they used may not have adequately distributed the medicine to all parts of these large tumors, two patients seemed to show definite (albeit temporary) improvement because of the treatment. The researchers urge that additional trials testing THC and other cannabinoids in this and other types of tumors be undertaken.

This is an exciting area of research, but one that has been needlessly — and perhaps lethally — slowed down by the U.S. government’s slavish devotion to anti-marijuana dogma. That most of the work testing these marijuana derivatives as anti-cancer drugs is occurring outside the United States is a sad commentary indeed.

Bruce Mirken, a longtime health journalist, serves as director of communications for the Marijuana Policy Project, www.mpp.org.

The smoke from burning marijuana leaves contains several known carcinogens and the tar it creates contains 50 percent more of some of the chemicals linked to lung cancer than tobacco smoke. A marijuana cigarette also deposits four times as much of that tar as an equivalent tobacco one. Scientists were therefore surprised to learn that a study of more than 2,000 people found no increase in the risk of developing lung cancer for marijuana smokers.
“We expected that we would find that a history of heavy marijuana use–more than 500 to 1,000 uses–would increase the risk of cancer from several years to decades after exposure to marijuana,” explains physician Donald Tashkin of the University of California, Los Angeles, and lead researcher on the project. But looking at residents of Los Angeles County, the scientists found that even those who smoked more than 20,000 joints in their life did not have an increased risk of lung cancer.
The researchers interviewed 611 lung cancer patients and 1,040 healthy controls as well as 601 patients with cancer in the head or neck region under the age of 60 to create the statistical analysis. They found that 80 percent of those with lung cancer and 70 percent of those with other cancers had smoked tobacco while only roughly half of both groups had smoked marijuana. The more tobacco a person smoked, the greater the risk of developing cancer, as other studies have shown.
But after controlling for tobacco, alcohol and other drug use as well as matching patients and controls by age, gender and neighborhood, marijuana did not seem to have an effect, despite its unhealthy aspects. “Marijuana is packed more loosely than tobacco, so there’s less filtration through the rod of the cigarette, so more particles will be inhaled,” Tashkin says. “And marijuana smokers typically smoke differently than tobacco smokers; they hold their breath about four times longer allowing more time for extra fine particles to deposit in the lungs.”
The study does not reveal how marijuana avoids causing cancer. Tashkin speculates that perhaps the THC chemical in marijuana smoke prompts aging cells to die before becoming cancerous. Tashkin and his colleagues presented the findings yesterday at a meeting of the American Thoracic Society in San Diego.