Las Vegas Sun

March 28, 2024

Smoking, cancer link now firmer

The new work "helps close a loophole" that has enabled tobacco lawyers to deny that researchers have proven the smoking-cancer connection, says John Banzhaf, director of Action on Smoking and Health, an anti-tobacco group.

He said the study published today in the journal Science means "we now have the evidence we need."

In the study, researchers report they have found that a tobacco carcinogen called BPDE links up with three molecular sites on the P53 gene -- a gene that is critical in the development of cancer.

"In essence, our study provides a direct link between a defined cigarette-smoke carcinogen and human cancer mutations," Moon-shon Tang, a scientist at the M.D. Anderson Cancer Center in Houston and a lead author of the study, said in a statement. Annie Pao, also of Anderson, and Mikhail F. Denissenko and Gerd P. Pfeifer of the Bechman Research Institute of the City of Hope, Duarte, Calif., are the other authors.

A number of earlier studies have linked BPDE from cigarette smoke to lung cancer. Research also has shown that in most lung cancers, the P53 gene is damaged or altered at points in the gene structure that Tang called "hot spots."

In the new study, researchers show that BPDE binds, or joins, the P53 gene at exactly those same "hot spots."

Though the BPDE has long been linked to lung cancer, Tang said, "until now we did not know it binds with the spots on the P53 gene that are associated with lung cancer."

Despite "overwhelming evidence" from earlier studies, said Banzhaf, tobacco lawyers have been able to argue that science has not shown the specific biological mechanism by which cigarette smoke causes lung cancer. He said the new study now provides that evidence.

"If we had nothing but this study, it wouldn't prove it," said Banzhaf. But added to hundreds of other studies linking smoking and lung cancer, he said, the new study "provides the last link, the smoking gun, if you will, on the issue that smoking causes lung cancer."

He said "it makes it easier now for us to demonstrate in court" the link between smoking and lung cancer.

Banzhaf said the study will add momentum to a drive to ban smoking in all public places and to do away with "smoking sections" in restaurants and bars because the research suggests that even a small amount of tobacco smoke can cause genetic damage that may lead to cancer.

Six tobacco companies are now being sued by 16 states and a number of cities. The state and local governments are seeking to recover the medical costs of treating patients made sick by cigarette smoking, said Banzhaf.

"This study is going to help us win those suits," he said.

The study also drew applause from the scientific community.

Dr. Bert Vogelstein, a Johns Hopkins University researcher who first linked the P53 gene with cancer, said the new evidence on smoking and cancer "is really quite compelling scientifically."

"This is the first specific scientific evidence linking smoking with lung cancer at a molecular level," said Vogelstein. "This is a very important piece of evidence because it complements the overwhelming evidence from epidemiology and other studies that cigarette smoking can cause lung cancer."

Tom Lauria, a spokesman for the Tobacco Institute, a trade group of the cigarette industry, declined comment on the new study, saying his organization has not yet had a chance to examine the work in detail.

P53, the gene identified in 1990 as a key guardian against cancer, works by monitoring the accuracy of DNA copying during cell division. If the gene detects abnormal DNA, it stops the cell division or causes the cell to kill itself. If P53 is damaged, inactivated or absent, however, this guardian function is destroyed. A cell with abnormal DNA may then divide without restraint, a process that can lead to cancer.

A chemical called benzo(a)py rene, or BP, is a component of cigarette smoke that has long been associated with lung cancer. When BP is taken into the lungs, such as when a smoker inhales, the chemical changes to benzo(a)pyrene diol epoxide, or BPDE. It is this chemical that damages the P53, the researchers found.

Science, which published the study, is the journal of the American Association for the Advancement of Science.

archive