In the context of breast cancer cells, although playing a common role as a negative regulator of estrogen signaling, evidence indicates that the aryl hydrocarbon receptor (AhR)-activated pathway promotes intratumoral estrogen synthesis, as indicated by the induction of aromatase expression in MCF-7, T47D-1, and MDA-MB-231 breast cancer cells [61]. This evidence concerns the gene AHR and breast cancer.