Moreover, PAH exposure activates the expression of AhR (aryl hydrocarbon receptor).[47] AhR may act as a transcription factor to perform the transcription of a wide range of genes that may exhibit the biological and toxicological effects of PAHs.[48] It has been reported that AhR inhibited BRCA1 transcription in MCF7, UACC3199, and HCC38 BC cells.[49] However, whether BPDE might regulate HR repair through AhR in human trophoblast cells is completely unknown and should be investigated. This evidence concerns the gene BRCA1 and breast cancer.