Study 'locks up' lung cancer, smoking link

Reported by Doug Levy, Oct. 18 1996, USA Today, Health

Scientists have found the strongest direct link yet between cigarette smoking and lung cancer.

Gerd Pfeifer of the Beckman Research Institute of the City of Hope, Duarte, Calif., and colleagues report in Friday's Science on a study showing that specific carcinogens in cigarette smoke target parts of p53, a key cancer gene.

When p53 is normal, it protects against cancer. But when mutations occur, it is responsible for cancer growth. About 60% of lung cancers involve mutations of the p53 gene.

In Pfeifer's study, human cells were treated with a derivative of benzopyrene, a potent carcinogen in tobacco smoke. Researchers then studied where mutations occurred and found they were in precisely the same locations on p53 as in the most common human lung cancers. "It is also of interest that two of the . . . hot spots . . . are at positions that are common mutational sites not only in lung cancer but also in many other cancers," they say.

Doctors have known since the 1950s that smoking is statistically linked to lung cancer, but this study and another report out last year are the first to demonstrate the specific biological mechanism.

Dr. David Sidransky, who found a direct relationship between how much people smoke and the number of p53 mutations in their cancers, says Pfeifer's report "really locks up" the link between smoking and lung cancer.

"Smoking can induce those genetic changes that can lead to cancer. The p53 gene is a specific target of cigarette smoke," says Sidransky of The Johns Hopkins Medical Institutions, Baltimore.

Lung cancer kills about 158,700 Americans each year; 177,000 new cases are expected to be diagnosed this year. About 28% of smoking-related deaths are from lung cancer.

By Doug Levy, USA TODAY