Regulation of Estrogen Receptor (ER) and BRCA1 By Bisphenol-S (BPS) in Breast Cancer Cells

Presentation Number: OR15-2
Date of Presentation: April 1st, 2017

Katie Marie Aleck*, Kelly Marie Hallman, Brigitte Dwyer, Victoria Lloyd, Monica Szmyd, Tyler Bedgood, Ann Fuelle and Sumi Dinda
Oakland University, Rochester, MI

Abstract

Bisphenol-S (BPS), a substitute for bisphenol-A (BPA), has been suggested to be an endocrine disrupting compound interfering with normal hormonal activity. This bisphenol analogue is found in plastic substitutes, paper currency, and most products marked “BPA-free.” Despite hopes for a safer alternative, studies have shown BPS to exhibit similar estrogenic activity due to its structural commonalities with its analogue BPA. Generally, bisphenols have been shown to disrupt proper estrogen receptor alpha (ERα) functioning in breast cancer cells. Given that a mutated BRCA1 gene will likely develop into hereditary breast cancer in 55-65% of people, determining the estrogenic effects of BPS in both genes is essential. This study focused on the effects of BPS, alone and in combination with hormones and anti-hormones, to examine the expression of ERα and BRCA1 in T-47D and MCF-7 breast cancer cells via Western Blot analyses, cellular viability, and RT-qPCR analyses. Western blot analysis revealed alterations in the expression of ERα and BRCA1 protein levels after 24 hours of treatment with varying concentrations of BPS (4-20 µM). A concentration-dependent decrease of ERα protein levels was observed in both cell lines, with a 49% reduction occurring with 8 µM BPS as compared to control. BRCA1 levels portray continued expression through concentrations of 20 µM BPS, found similarly in both cell lines. To gain further insight into possible similarities between BPS and other known effectors of ERα, the optimal concentration of BPS (8 μM) was used in combination with hormones and anti-hormones. Down-regulation of ERα protein levels was observed after 24-hour co-treatment of T-47D and MCF-7 cells with 8µM BPS and 10 nM E2. BPS with ICI showed significant down-regulation as compared to BPS alone, and BPS with TAM portrayed no significant differences. A similar trend in the effects on BRCA1 expression was depicted in T-47D and MCF-7 cells. Image cytometric analysis with propidium iodide staining was utilized to quantify cell values and viability changes to further portray the effects of BPS on T-47D and MCF-7 cellular growth. Following a six-day treatment with 4 µM to 20 µM BPS, cellular proliferation showed a 12-60% increase in both cell lines. The proliferative effect of E2 and BPS in cells was reversed when treated in combination with anti-estrogens. Gene analysis showed a transcriptional expression of ESR1 mRNA levels that correlate with the translational data obtained via western blot analyses on BPS. This study may contribute to the understanding of the molecular effects in breast cancer cells exhibited by endocrine disrupting compounds, specifically BPS, on tumor suppressor proteins and steroid receptors.

 

Nothing to Disclose: KMA, KMH, BD, VL, MS, TB, AF, SD