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Your Environment. Your Health.

Newly Identified Mechanism in Breast Cancer

D. Jerry Joseph, Ph.D.
University of Massachusetts Amherst

A recent NIEHS-funded study identified a new mechanism in which chemicals that act like estrogens may promote breast cancer. The team used a novel approach to study the effects of two chemicals commonly used in cosmetics and sunscreen and found that they caused DNA damage in both mouse and human breast cells at surprisingly low levels. Breast cells have estrogen receptors that may make them uniquely susceptible to DNA damage by estrogenic chemicals.

The researchers compared the ultraviolet filter benzophenone-3 (BP-3), found in sunscreen, and propylparaben (PP), a preservative found in cosmetics and other personal care products, with a form of estrogen called 17 beta estradiol (E2). They studied DNA damage from exposure to the two chemicals in three groups of cells: mammary cells from treated and control mice; lab-grown human breast cells that lacked estrogen receptors; and newly designed human breast cells in which the researchers could selectively activate estrogen receptors.

Similar to E2 treatment, BP-3 and PP increased DNA damage even at low levels, but only in cells with estrogen receptors. According to the authors, the DNA damage in breast epithelial cells was caused by formation of estrogen receptor-dependent R-loops, a specific type of DNA damage that may be a sensitive endpoint for screening potentially harmful chemicals. They further noted that activating estrogen receptor expression in normal breast cells provided a tool to measure differences in sensitivity to these compounds among individuals. This may help researchers determine whether some people may be more susceptible to cancer.

Citation: Majhi PD, Sharma A, Roberts AL, Daniele E, Majewski AR, Chuong LM, Black AL, Vandenberg LN, Schneider SS, Dunphy KA, Jerry DJ. 2020. Effects of benzophenone-3 and propylparaben on estrogen receptor-dependent R-loops and DNA damage in breast epithelial cells and mice. Environ Health Perspect 128(1):17002.

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