March 16, 1995 in Nation/World

Tobacco Damages Anti-Cancer Gene Drinking May Also Raise Risk Of Certain Cancers Among Smokers Baltimore Sun


Three decades after a surgeon general’s report linked smoking to human cancers, researchers at the Johns Hopkins School of Medicine here have traced one of the genetic pathways by which tobacco does its harm.

Scientists studying people with head and neck cancer found that tobacco damages a gene, known as p53, that works as a natural brake against a developing cancer. Without this repair mechanism, malignant cells can multiply and flourish into full-blown tumors.

Although the mutation has been blamed for many cancers, the research by Dr. David Sidransky and colleagues at Hopkins is the first time the genetic defect has been tied specifically to tobacco smoke in a large series of human patients.

The scientists also found that the mutation occurs with even greater regularity among people who both smoke and drink alcohol. Although the reasons are not completely understood, Sidransky said alcohol may cause a cell’s genetic material to act like a sponge, soaking up carcinogens more readily.

Some studies, he said, have suggested that alcohol may also damage the protective lining of the mouth and other tissues, allowing carcinogens to pass more easily into the underlying cells.

“What we saw was phenomenal,” said Sidransky. “If you smoke and drink, you had a much, much higher rate of the p53 mutation than if you were a non-smoker and a nondrinker.”

The findings, reported in today’s New England Journal of Medicine, grew out of a study of 129 people who had cancers of the lip, mouth, tongue, jaw and other tissues of the head and neck. More than three-quarters of the patients were smokers.

When the scientists studied the genetic makeup of the patients’ tumors, they found that one-third of the patients who smoked carried defects of the tumor suppressor gene. In the smokers, the mutation showed up twice as frequently as it did in the small number of cancer patients who did not smoke.

The mutation, however, was found in 58 percent of the cancer patients who both smoke and drank - suggesting that alcohol enhances the cancer-causing power of tobacco smoke.

The Hopkins findings are merely the latest chapter in the scientific community’s evolving case against tobacco.

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