Study: Do parabens in personal care products increase breast cancer risk?

IN DEPTH REVIEW OF RESEARCH

Study background:

Estrogen is known to promote breast cancer by binding to estrogen receptors in the breast. Because of this well-established association, there is a lot of concern about “estrogen mimickers,” chemicals that can bind to estrogen receptors in the body. Parabens are estrogen mimickers that are used in many personal care products, including cosmetics, shampoos, and sunscreens, to prevent microbial and fungal growth in the products. Previous studies showed that even though parabens are estrogen mimickers, they bind to estrogen receptors very weakly, and cannot cause cells to become cancerous. For this reason, the FDA has deemed parabens to be safe for use.

In October of 2015, Dale Leitman and colleagues at the University of California, Berkeley published a study in the journal Environmental Health Perspectives that looked at the ability of parabens to stimulate the growth of breast cancer cells. The study authors feel this is important because previous studies only looked at the ability of parabens to encourage cell growth in an environment that did not include human epidermal growth factor receptor 2 (HER2) and the molecule that activates it, which is present in some breast cancers.

Researchers of this study wanted to know:

Whether parabens can stimulate breast cancer cell growth when the HER2 receptor and the molecule that activates it are present.

Population(s) looked at in the study:

This study did not include humans. Rather, it used invasive breast cancer tumor cells taken from a woman; researchers grew the cells in special dishes in the laboratory that provided all of the nutrients a cell needs to grow and divide. The cells included both estrogen receptor (ER+) and human epidermal growth factor receptor 2 (HER2+). Cells from women with ER+/HER2- and ER-/HER2+ breast cancers were used for comparison. 

Study findings: 

1. Using human breast cancer cells that were estrogen receptor-positive (ER+) and human epidermal growth factor receptor 2-positive (HER2+), parabens stimulated cell growth in the laboratory.
2. Growth in breast cells containing the molecule that activates HER2 was stimulated by fewer parabens than cells that did not contain the molecule.

Limitations:

This study isolated one patient’s ER+ and HER2+ invasive breast cancer tumor cells and then grew them in the laboratory.  Studies involving cells have some general limitations. One is that although researchers try to mimic the cells’ environment in the body, it is not possible to do this perfectly. The cells in this study were observed in isolation: they were not surrounded by different types of cells and organs normally found in the body, nor were they potentially affected by what would be going in the body at any given time. Studies like this that use laboratory-grown cells are considered to be very early steps in the research process, and do not necessarily translate to what will happen in humans.

It is also important to note that the cells used in this study were from a woman with invasive breast cancer; they do not represent what occurs in people without cancer.  Study authors did not note whether the cell donor had mutations in BRCA or other genes that increase breast cancer risk.

Conclusions:

Research done with cells has limitations, but it is still an important first step in the research process.  As such, these studies point to ideas that should be studied further in a more biologically relevant environment. While it is possible that the cell findings could be important for humans, it is also possible that the cell findings will not be replicated in other cells or in studies on living organisms. This study indicates that more work needs to be done to determine whether parabens can increase breast cancer cell growth and potentially increase cancer risk, as noted in many media reports, but it will take more studies to show if this is the case.  

Posted 1/12/16