"It is well known that alcohol consumption is associated with increased risk of breast cancer, but the mechanisms of action are still unclear," Menghua Tao said in a statement.

"In our population study, we found that alcohol consumption is associated with increased likelihood of hypermethylation -- unregulated cell growth -- of the E-cadherin gene."

Alcohol consumption causes genes that promote normal cell growth to produce proteins that precipitate unregulated cell growth, or hypermethylation, the study said.

Tao and colleagues analyzed tumor blocks from 803 women who took part in Western New York Exposures and Breast Cancer Study with data on alcohol consumption.

Hypermethylation of the gene was twice as likely to be found in tumors of women classified as drinkers than in those classified as never drinkers, Tao said.

This mechanism was linked with an increased risk of postmenopausal breast cancer, but not premenopausal breast cancer, the study showed.

Tao presented the findings at the American Association of Cancer Research meeting held recently in San Diego.