In the presence of TGF-β1, H2O2 increased the BRCA1 and Smad3 interaction at the endogenous level in human keratinocyte HaCaT cells (Figure 4A) and wild type BRCA1-reconstituted HCC1937 breast cancer cells (HCCBRCA1) (Figure 4B). This evidence concerns the gene TGFB1 and breast cancer.