Pregnant mothers who drink alcohol may increase their unborn babies’ risk of later developing breast cancer, according to a new study conducted in animals. Researchers from Rutgers, the State University of New Jersey, are presenting the results Sunday at The Endocrine Society’s 92nd Annual Meeting in San Diego.
The investigators found that rats exposed to alcohol during the fetal period had changes in breast gland development. At 20 days of life—before puberty—the alcohol-exposed rat offspring had more sites of rapidly growing ductal structures, which increases future breast cancer risk, than did either group of control rats, whose mothers did not receive alcohol, said study co-author Wendie Cohick, PhD, an associate professor in Rutgers’ Department of Animal Sciences, Brunswick, N.J.
Compared with rats that did not have fetal alcohol exposure, these rats also had more aromatase, a protein responsible for making estrogen. This suggests that estrogen production had increased. High estrogen level is a known risk factor for breast cancer in women. Both changes were evident before the rats reached puberty, suggesting that this pre-programming for breast cancer risk in adulthood occurs early in life, according to Cohick.
“This could represent a significant public health concern, because the Centers for Disease Control and Prevention reports that one in 12 women drink during pregnancy,” she said. “If these studies extend to humans, women whose mothers drank alcohol during pregnancy should be encouraged to get mammography screening at an earlier age than recommended for the general public.”
Pregnant rats in the study received a liquid diet that contained 35 percent of calories from alcohol, “the equivalent of heavy drinking in humans—two to four drinks,” Cohick said. Another group of pregnant rats consumed a liquid diet with no alcohol. To make sure that the liquid diet did not influence results, the researchers had a second control group, in which they gave pregnant rats solid rat chow. At birth the rat pups nursed from mothers that never received alcohol. This ensured that the effects seen were because of events that occurred during fetal development, and not as a result of alcohol consumed through breast milk, she said.
Finally, at both 20 days (before puberty) and 40 days (after puberty) after birth, rats with fetal alcohol exposure had a four- to five-fold increase in expression in liver expression of insulin-like growth factor-1, or IGF-1. A protein hormone made in the liver in humans, IGF-1 travels through the blood to the mammary gland, where it acts in concert with estrogen to increase cell division, Cohick said.
These hormonal changes likely contribute to the increased development of breast tumors in rats after exposure to a carcinogen, which they saw in an earlier study, she said.
Grant support for this research came from the National Institutes of Health and from the Rutgers New Jersey Agricultural Experiment Station and the Charles and Johanna Busch Memorial Fund.
