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. In two instances research arguing against a connection was undertaken and published by individuals with links to tobacco companies. Both studies were published in a journal whose editor-in-chief has an extensive and undisclosed history of working as a tobacco industry researcher and consultant. "The tobacco companies claim that they are now working with the public health community to 'support a single, consistent public health message on the role played by cigarette smoking in the development of the disease in smokers;" Glantz says. "But their multifaceted response to p53 research as recently as 2001 suggests that they have not changed their practices." "The extent and sophistication of the tobacco industry involvement in p53 research challenge authors, editors and users of scientific literature to be vigilant in demanding and maintaining rigorous standards for disclosing and evaluating potential conflicts of interest. Universities and other biomedical researchers should stop taking money from the tobacco industry in order to minimize the potential for any impairment of the integrity of the scientific process," Glantz notes in an email.

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