Transcriptomic analysis of BPA alternative chemicals in primary human mammary epithelial cells

Some everyday consumer products contain endocrine disruptors like bisphenol A (BPA) and its replacements. To date, most in vitro chemical screening to evaluate these compounds has been accomplished using immortalized cell lines, which differ significantly from human tissues. Our goal was to test BPA and select alternatives previously screened in breast cancer cells for toxicological potency and mechanism of action in human mammary epithelial cells (HMECs). HMECs from three human donors were exposed to BPA and four alternative chemicals (in concentration response format from 0.001 – 50 µM) for 48 h and global transcriptomic changes were quantified. Transcriptomic biomarker analysis was employed to explore chemically induced estrogen receptor alpha (ERα) activation and alterations in stress response pathways. Benchmark concentration (BMC) analysis was applied to gene expression data to derive transcriptomic points of departure (tPODs) to compare chemicals for potency. Pathway and upstream regulator analysis was applied among the genes fitting BMCs. All chemicals had tPODs within an order of magnitude of each other. Bisphenol AF (BPAF) was the most potent, followed by tetramethyl bisphenol F (TMBPF), bisphenol C (BPC), 4,4’-bisphenol S (BPS), and BPA. None of the chemicals activated the ERα active biomarker. Some stress response biomarkers were activated at high exposure concentrations. Genes fitting BMCs clustered chemicals into two groups, with one group (BPAF and TMBPF) primarily inhibiting expression patterns and the other (BPC, BPS, and BPA) mostly activating. These data suggest that the BPA alternatives tested have similar toxicological potencies in HMECs and oppositely enrich cancer related gene sets.