The family history factor in breast cancer

While it is well known that family history is an important factor in breast cancer risk, in many cases an increased risk of developing breast cancer is not due to genetic mutations that are passed down to future generations. Researchers at Georgetown University Medical Center have found that in rats, exposure of a pregnant mother to estrogenic compounds can result in increased risk of cancer in daughters, granddaughters, and even great granddaughters.

To understand how this increased risk is transmitted without genetic mutation, Joseph Wang used statistical machine-learning techniques to analyze changes in the methylation status of the DNA of descendants with increased risk. DNA methylation is a key process in normal development, allowing cells with the same genome to perform different functions by using methylation to turn some genes on and some genes off.

Wang's group found that the descendants with increased risk had several hundred common DNA regions that were methylated differently than a control group, providing a possible mechanism for how breast cancer risk can be transmitted without genetic mutations. Ultimately, it may be possible to undo this harmful methylation and decrease the risk of breast cancer.