Damage to Cancer Gene Linked to Smoking
The strongest evidence yet tying tobacco smoke directly to the genetic damage that leads to cancer was reported this week by a research team in Baltimore.
The new work, reported Wednesday in the New England Journal of Medicine, “is molecular proof that smoking increases the rate of mutation” in a specific gene called p53, said Dr. David Sidransky, a cancer specialist at the Johns Hopkins School of Medicine. Damage to the p53 gene is known to play a central role in the cancer process.
Sidransky said the results also show that adding alcohol to the mix--combining smoking with moderate or heavy drinking--raises the risk even higher.
As a result, he said, “now the most common carcinogens that people expose themselves to are linked to the most common (genetic) change in human cancer.”
The take-home message, he added, “is to tell every single doubter--anyone who clings to some hope that the evidence associating it (smoking) with cancer is incomplete--that proof has arrived. It really indicates that stopping smoking is essential for the prevention of these cancers.”
The detailed report by Sidransky and eight research colleagues deals with so-called head and neck cancers, such as tumors of the larynx and mouth. They found that the mutation rate was doubled in cancer patients who were smokers compared to those who were not. Equally important, the types of mutations found in the smokers differed from those found in nonsmokers.
Molecular biologist Christine Nogueira at the Boston University School of Medicine said Sidransky’s study “gives definitive evidence of the association between smoking and head and neck cancer. They used the most powerful molecule tool, sequencing of the gene,” to get the answers. Sequencing involves “reading” a gene by noting the exact sequence of its chemicals and noting how a mutated gene differs from a normal gene.
She added that “everybody knew” smoking and gene damage were linked, “but they have proved it consistently” in the Johns Hopkins work.
According to the American Cancer Society, cigarette smoking is responsible for about 90% of all lung cancer deaths. Smoking also had been associated with the head and neck cancers studied by Sidransky and with cancer of the esophagus, pancreas, cervix, kidney and bladder.
The tobacco industry’s trade organization, the Tobacco Institute, said it did not have the expertise to comment. The industry has long maintained that a cause-and-effect relationship between smoking and cancer remains unproven.
