Alcohol And Genetic Factors Linked To Breast Cancer Risk

US scientists have discovered two genes that play a role in the metabolism of alcohol, which are linked with increased risk of breast cancer in postmenopausal women who drink.

The study was presented yesterday in San Diego, California, at the Annual Meeting of the American Association for Cancer Research (AACR). The research leaders were Dr. Peter Shields, professor of medicine and oncology based at Georgetown University's Lombardi Comprehensive Cancer Center in Washington DC, and Dr. Jo Freudenheim, chair of social and preventive medicine at the State University of New York in Buffalo.

The research showed that variations in two genes, ADH1B and ADH1C, that code for an enzyme that breaks down alcohol, were linked with increased risk of breast cancer among women who drink.

Research instructor of cancer genetics and epidemiology at Lombardi, and lead author of the study, Dr. Catalin Marian said:

"The higher their alcohol consumption, the higher their risk."

The researchers examined DNA information from 991 women aged 35 to 79 residing in two western New York counties between 1996 and 2001 who had histologically confirmed primary stage breast cancer. These were matched by 1,698 randomly selected healthy participants according to age, race and county of residence.

All participants were taking part in a population-based case-control study called the Western New York Exposure and Breast Cancer (WEB) Study, conducted by Freudenheim.

The results showed that increased breast cancer risk in postmenopausal women was linked to variations in DNA sequences in two genes: ADH1B (sequence rs1042026) and ADH1C (sequence rs1614972).

Among postmenopausal women with the ADH1B (sequence rs1042026) gene variant, the risk of breast cancer for the alcohol drinkers was nearly double that of the abstainers.

Among women with the ADH1C (sequence rs1614972) gene variant, there was a protective effect against breast cancer risk that varied inversely with the amount of alcohol: the more alcohol a woman with this gene variant consumed, the less protection offered, and the higher the risk of breast cancer. (Conversely, this could be viewed as the protection conferred by the gene appeared to get stronger as alcohol consumption dropped).

Marian warned that more research was needed to confirm and replicate the findings before any firm conclusions could be drawn. This study merely suggests that the variants are linked with increased breast cancer risk, it does not suggest they cause it biologically.

Variations in the two genes will impact alcohol metabolism because they are involved in that process, explained Marian, but she was cautious to point out this may not be the whole story:

"We have to keep in mind that the gene sequence variations we observed are not located directly in coding regions, but they may be associated and inherited together with other variations that have this effect on the enzyme function."

According to the National Cancer Institute, in 2008 there will be over 180,000 new cases of breast cancer among women and nearly 2,000 among men, while over 40,000 women and nearly 500 men will die of the disease.

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