March 22, 2007

Alcohol and Cancer

Study finds that consuming alcohol increases the rate tumors grow.
Dr. Jian-Wei Gu came to Mississippi to study the cardiovascular system, with a special interest in blood vessel growth, but he ended up making headlines.

According to Gu, assistant professor of physiology and biophysics at the University of Mississippi Medical Center, it all happened completely by accident.

...a study from Paris in 1910 that showed that 80 percent of patients with cancer of the esophagus or gastric track were alcoholics...

Reports of Gu's research have appeared in USA Today, Science News, the New Scientist, and on CBS News. Gu made news by doing what many scientists before him have failed to do: describe the mechanism by which alcohol consumption causes tumor growth.

"Scientists have known for a hundred years that there is a strong association between alcohol consumption and several types of cancer," Gu said. He cites a study from Paris in 1910 that showed that 80 percent of patients with cancer of the esophagus or gastric track were alcoholics.

More recently, epidemiological studies show a strong correlation between alcohol consumption and cancer of the mouth, pharynx, larynx, esophagus, liver and large bowel. Alcohol consumption seems to be a risk factor even for breast cancer. But until now, experiments in the lab have failed to show the effects in animals that observers knew to be true in humans.

The problem, it turns out, was that investigators were using too much alcohol. "Most all the previous studies used alcohol concentrations of 20 percent, far more than the equivalent human consumption," Gu said. The animals wasted away but they didn't show abnormal tumor growth, he said. Gu used alcohol concentrations of one percent, about the equivalent of one or two drinks a day in humans, or moderate alcohol consumption. Using what he terms "physiologically relevant" levels of alcohol, he was able to cause tumor growth in both chicken embryos and in mice.

Gu came to Mississippi in 1995 to work on angiogenesis, or blood vessel growth, and what stimulates or controls it. Seven years ago, working in the lab, he and his colleagues noticed that the growth factor that stimulates vessel growth (vascular endothelial growth factor or VEGF) increased "unexpectedly" in certain cell cultures.

They determined that it was the alcohol they used as a solvent, in very low concentrations, that caused the increase in the growth factor.

That accidental finding by Gu in 2000 led to the study in chicken embryos and, most recently, to a study showing that melanoma (skin cancer) in mice grew significantly faster and larger if the mice consumed the equivalent of one or two alcoholic drinks a day.

Dr. Thomas Adair, professor of physiology and biophysics and Gu's mentor when he came to Mississippi, said that Gu's findings have been confirmed by other scientists. "When he presented his findings at a FASEB (Federated Societies for Experimental Biology) meeting, someone from a group in San Diego came up to me afterward and told me they had found the same thing in their lab and didn't know what to make of it. They went back and did a study on rats and found the same thing."

Angiogenesis, or the growth of new blood vessels, is an area of keen interest for its application to cancer therapy. Right now, Adair estimates there may be as many as 40 drugs in clinical trials that fight cancer by controlling angiogenesis. But angiogenesis is not always a bad thing, according to Adair. Stimulating angiogenesis would be helpful, for example, in repairing heart tissue damaged by a heart attack or in wound healing.
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