Genotoxicity of bisphenol A and bisphenol analogues using human breast cancer (MCF-7) mutants

Abstract

In response to the restriction of bisphenol A (BPA), bisphenol analogues (BPs) have been often used as alternative compounds for the production of polycarbonate plastics. However, limited information is available on their genotoxic effects. In this study, the genotoxic effects and underlying mechanisms of BPs were investigated using human breast cancer (MCF-7) mutants that were deficient in major DNA repair pathway. We assessed whether tyrosyl-DNA phosphodiesterase 2 (TDP2) contributed to the repair of BPs-induced double strand breaks (DSBs) in MCF-7 cell line. MCF-7 TDP2-/- mutant cells were generated by CRISPR/Cas9 gene targeting with a guide RNA designed and cloned into pX459. After pulse exposure (2 hr) of MCF-7 TDP2-/- mutants to DMSO (as solvent control), estradiol (as positive control), and seven BPs (BPA, BPAF, BPAP, BPC, BPF, BPS, and BPSIP 20 ppm), immunostaining of tumor suppressor p53-binding protein 1 (53BP1) foci was performed. To exclude the effects of DNA replication and homology-directed repair, we enriched G1-phase cells by serum starvation using serum-free medium for 24 hr before chemicals treatment. The average number of 53BP1 foci was significantly increased in MCF-7 TDP2-/- mutant cells exposed to BPA and its analogues compared to the solvent control. The extent of increase in foci number was greater in BPAF, BPSIP, and BPS-treated groups than in BPA or E2 exposure group. These results suggest that BPs could induce DSBs repaired through TDP2 pathway, and BPAF, BPSIP, and BPS appeared to have more profound effects on genotoxicity than BPA did. The present study indicated that BPs have a genotoxicity similar or greater than the compound that they were intended to replace, i.e., BPA. Acknowledgement: This study was supported by the National Research Foundation of Korea (Project NRF-2019R1A2C1002712).