A study conducted by researchers from Silent Spring Institute in collaboration with scientists from the University of California, Berkeley and the University of Florida College of Veterinary Medicine found that lower doses of parabens might increase breast cancer risk. Parabens are chemicals used as preservatives in cosmetics, lotions, sunscreens and other personal care products. They are considered to be estrogenic because they mimic the natural hormone estradiol by activating the same estrogen receptor, and as a result, may affect breast cancer and reproduction.
Existing chemical safety tests, which measure the effects of chemicals on human cells, only look at parabens in isolation and fail to take into account that parabens could interact with other types of molecules in the cells to increase breast cancer risk. To better reflect what goes on in real life, the researchers looked at breast cancer cells that express two types of receptors: estrogen receptor and HER2 receptor. Approximately 25 percent of breast cancers produce an abundance of HER2. HER2-positive tumors tend to grow and spread more aggressively than other types of breast cancer. The researchers activated the HER2 receptors in breast cancer cells with a growth factor called heregulin that is naturally made in breast cells, while exposing the cells to parabens, which bind to the estrogen receptor.
- Parabens triggered the estrogen receptors in HER2-activated cells by turning on genes that caused the breast cancer cells to proliferate.
- The parabens in the HER2-activated cells were able to stimulate breast cancer cell growth at concentrations 100 times lower than in cells where HER2 receptors were not activated.
- Parabens may increase breast cancer risk at lower doses than previously thought.
- Chemical safety tests may underestimate parabens’ potency and effects on human health.
“While this study focused on parabens, it’s also possible that the potency of other estrogen mimics have been underestimated by current testing approaches.” –Chris Vulpe, co-author and toxicologist at the Center for Environmental and Human Toxicology at the University of Florida College of Veterinary Medicine.
The California Breast Cancer Research Program
Pan, S., C. Yuan, A. Tagmount, R.A. Rudel, J.M. Ackerman, P. Yaswen, C.D. Vulpe, and D.C. Leitman. 2015. Parabens and Human Epidermal Growth Factor Receptor Ligands Cross-Talk in Breast Cancer Cells. Environmental Health Perspectives.