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A. Proving Tobacco's Link To Lung Cancer

Narrator: This is Science Today. Researchers have found new evidence which may prove that an individual's lung cancer was the direct result of exposure to tobacco smoke - even secondhand. John Wiencke, a professor of epidemiology at the University of California, San Francisco, found tobacco smoke caused specific mutations in what's called the p53 tumor suppressor gene of lung cells. These genes are key factors associated with some cases of lung cancer.

Wiencke: In tobacco smoke related cancers, there are certain regions of the gene that appear to be preferentially mutated or disrupted and those are called hot spots, hot spots for mutation in the p53 gene.

Narrator: These hot spots may be caused by the tar in cigarettes which bind to certain parts of the p53 gene and leave what Wiencke calls Afingerprints@ of tobacco smoke carcinogens.

Wiencke: I think we're on the right track and these are significant developments but cancer is a very complicated problem and so we're not going to have answers about environmental tobacco smoke overnight.

Narrator: For Science Today, I'm Larissa Branin.