Genetics May Be Tied to Breast Cancer Risk in Unexpected Ways

Scientists found new connections among genes, hormone sensitivity and fat.

TUESDAY, March 19 (HealthDay News) -- Genetic testing may help identify women at risk for certain types of breast cancer, according to a new study.

Researchers found that over-expression or under-expression of certain genes may help doctors pinpoint women with estrogen receptor-positive or estrogen receptor-negative breast cancer. Doctor could then take appropriate steps to reduce breast cancer risk in certain patients.

The study appears March 19 in the journal Cancer Prevention Research.

"Currently, three drugs can be used to prevent breast cancer in women who are at extremely high risk for the disease," study co-author Dr. Seema Khan, said in a journal release. "However, these drugs prevent only breast cancers that are sensitive to hormones, commonly referred to as estrogen receptor-positive breast cancers. They do not prevent breast cancers that are insensitive to hormones, or estrogen receptor-negative breast cancers."

"We should not expose women at risk for hormone-insensitive breast cancer to the side effects of preventive medications that we know will not work for them," added Khan, who is co-leader of the Breast Cancer Program at Northwestern University, in Chicago. "Moreover, if we knew who these women were, we could focus on them in terms of designing new studies to find a solution for preventing hormone-insensitive cancer."

In their study, the researchers collected samples from unaffected breasts of 27 women with estrogen receptor-positive breast cancer, 27 women with estrogen receptor-negative cancer and 12 women without the disease.

The samples from the women with estrogen receptor-negative cancer had significantly higher expression of 13 genes, eight of which are associated with fat metabolism.

"This was interesting because obesity is a breast cancer risk factor for postmenopausal women, but obese women are generally thought to be at increased risk for hormone-sensitive cancer," Khan said. "We were surprised to see that some of these genes that are associated with lipid metabolism, or the metabolism of fats, are actually more highly expressed in the unaffected breasts of women with estrogen receptor-negative breast cancer."

The researchers also found that two genes associated with fat metabolism were under-expressed in samples from women with estrogen receptor-positive breast cancer.

"It will be a few more steps before this information is practically useful, but we are hoping that it can take us to a place where we can obtain a breast sample from healthy women, see that they are at risk for a certain type of breast cancer and tailor the prevention strategy accordingly," Khan said.

More information

The American Academy of Family Physicians has more about breast cancer.