Given our prior findings that AhR signaling mediates breast cancer cell resistance to apoptosis induced by UV radiation or anti-cancer drugs (34), we next examined the impact of AhRR expression on response of UCD-PYMT cells to doxorubicin (Dox), a DNA intercalating agent and etoposide (EtOP), an inhibitor of Topoisomerase-II. This evidence concerns the gene AHRR and cancer.