Study Reveals Tobacco Industry Continuing to Challenge Cancer-Smoking Link

By UCSF Today | January 18, 2005

A study of once-confidential tobacco industry documents reveals that in the past few years several tobacco companies have continued to support research challenging the link between cancer and a potent carcinogen found in cigarette smoke.

The companies continued this approach even after a landmark 1996 study demonstrated strong molecular evidence of the direct carcinogenic effect of the tobacco smoke constituent.

The new study from the Center for Tobacco Control Research and Education at UCSF, published online Jan. 14 in the British medical journal Lancet, uncovers the strategies used by the tobacco industry to counteract research linking tobacco smoke to cancer-causing mutations in a gene called p53.

Damage to the p53 gene leads to uncontrolled cell division. Mutations in this gene are found in more than 50 percent of all human tumors, including 60 percent of lung cancers.

Benzo[a]pyrene, a potent carcinogen, was identified in cigarette smoke in 1952. In the 1990s, studies demonstrated patterned changes in p53 after exposure to benzo[a]pyrene. A 1996 landmark study showed benzo[a]pyrene's interaction with p53 mirrored mutations found in actual human lung tumors. This finding provided strong molecular evidence of the direct carcinogenic effect of a tobacco smoke constituent.

Stanton Glantz, PhD, professor of medicine and director of UCSF's Center for Tobacco Control Research and Education, and colleagues examined 43 previously confidential tobacco industry documents relating to p53 and tobacco smoke. The researchers found that prior to 1996, several tobacco companies supported research projects investigating the mechanisms of p53 mutations. Following the 1996 landmark study, tobacco companies planned a number of research projects in response and supported studies which appeared to cast doubt on a link between p53 damage and benzo[a]pyrene in tobacco smoke.

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