Many healthy people who smoke or drink may have a genetic alteration in the cells of the mouth and throat that could signal an increased risk of developing cancer, according to researchers at the University of Hong Kong.

The genetic alteration affects the p15 gene, which is involved in the process that normally kills off cells when they go haywire. In many cancers, the p15 gene is methylated, meaning that it is turned off and is unable to perform its “tumor suppressor” function.

The researchers’ study of healthy adults and patients with head and neck cancers found that 68 percent of healthy smokers and drinkers showed methylated p15 in some of their oral cells. The same was true of 48 percent of the cancer patients, but only 8 percent of healthy adults who were non-smokers and drank only occasionally or not at all.

The investigators say it is unclear whether the healthy men and women who showed signs of p15 methylation are in fact at increased risk of developing head and neck cancer, a group of diseases that includes cancers of the mouth, nasal cavity and throat.

However, the findings do support the idea that “these p15 methylation changes are present in the very early stages of head and neck cancer development,” study co-author Dr. Anthony Po-Wing Yuen told Reuters Health.

He and his colleagues report on the study in the July 1st issue of the journal Cancer.

That smokers and drinkers face a risk of head and neck cancers is nothing new. Tobacco use is behind the majority of these cancers, and people who smoke and drink are at greater risk than those who do one or the other.

Identifying the “early genetic aberrations” that spur the cancer process may help doctors predict which smokers and drinkers are at particular risk of head and neck cancers, according to Yuen. What’s more, he said, if scientists know which early genetic changes are at the root of cancer, they may be able to develop drugs that reverse these alterations.

However, the researcher stressed, cancer development is a complex process, and a range of factors - including any number of genetic aberrations - conspire to determine who develops cancers of the head and neck.

The study included 37 healthy adults who did not smoke and drank rarely or not at all, and 22 healthy adults who smoked and regularly drank or did one or the other. Thirty-one patients with head and neck cancers also participated.

Yuen’s team found that while only three people who abstained from smoking and drinking showed p15 methylation in some of their oral cells, 15 of the 22 smokers and/or drinkers did.

Among the cancer patients, nearly half had p15 methylation in their mouth and throat cells, and even more - 65 percent - showed the genetic alteration in their tumor cells.

The fact that some participants who neither smoked nor drank showed some p15 methylation suggests that other factors, such as pollution or exposure to secondhand smoke or certain chemicals, may also help trigger the process, the researchers note.

SOURCE: Cancer, July 1, 2004.