Collectively, data mined from three large breast cancer databases (CCLE, TCGA, and Curtis) show a significant and generalizable association between Ahr or AHR activity (Cyp1b1 expression) and cancer stem cell- and migration/invasion-associated gene sets, an outcome consistent with regulation of these genes by a constitutively active (i.e. endogenous AHR ligand-activated) AHR. This evidence concerns the gene AHR and cancer.