Suspicions that the AHR plays some key role(s) in cancer arose from pioneering studies demonstrating dramatically increased AHR expression in numerous cancer subtypes, including Hodgkin’s lymphoma and chronic lymphocytic leukemia [82], adult T-cell leukemia [83], and cancers of the breast [52,56,84,85], head and neck [86,87], brain [88,89,90], kidney [91], lung [92,93], pancreas [94], and GI tract [95,96,97,98]. Here, AHR is linked to breast cancer.