AHR and breast cancer: For example, strong ligands of the aryl hydrocarbon receptor (AhR) such as such as 6-formylindolo [3,2-b]carbazole, 3-methylcholantrene and benzo[a]pyrene are known to induce hypomethylation of LINE-1 and then increase LINE-1 mRNA expression through the mitogen-activated protein kinase (MAPK) in breast cancer cell line and through the transforming growth factor-β1 (TGF-β1)/Smad pathway in HepG2 hepatocarcinoma cell line [165].