Bisphenol-A and Breast Cancer—It’s Beginning to Look a Lot Like DES

Bisphenol-A, BPA, is the subject of a study looking at its risk for increasing breast cancer, or precisely, the mechanism by which breast cancer risk may be increased after in utero exposure to either the substance or DES. Researchers looked at mothers ingesting either of these estrogen-like compounds during pregnancy and then determined what effect they had on the female offspring after they had been born as adults. DES, commonly used in the 1950s-1960s to prevent miscarriage, has long been studied and shown to increase risk of breast cancer to offspring of mothers who were given it during pregnancy. In animal studies, BPA is showing similar effects on breast tissue even though in a straight comparison between DES and BPA, DES is a much stronger substance.

The mechanism of why both these substances may increase breast cancer risk was the basis for the study. It was observed that one gene closely linked to breast cancer is permanently elevated in mice exposed to these substances, and leads to a permanent lifelong elevation of a molecule called enhancer of zeste homologue (EZH2), which, when elevated increases risk for cancer. Women who had biopsies that turned out to be benign but showed elevated EZH2 had a greater chance of developing breast cancer. Furthermore women with breast cancer who have expressed this gene have a worse prognosis. This change in gene formation only appears to happen during pregnancy. Exposure to these substances after birth does not express the gene change.

BPA is found in many substances. Most common forms are plastic bottles, hard plastic food containers, and cans. BPA is found in many more substances and has been around for years. There are some efforts to eliminate BPA from products. In California and Connecticut, there is a law to remove them from children’s toys, and nalgene has taken them out of their water bottles. The best way to avoid BPA as much as possible is to switch to stainless steel water bottles, buy fresh fruits, vegetables, beans so you are not using canned foods, and not cook or heat anything in plastics.

Dr. Kerry Ferguson