The effects of environmental aryl hydrocarbon receptor ligands on signaling and cell metabolism in cancer

Dioxin and dioxin-like compounds are chlorinated organic pollutants formed during the manufacturing of other chemicals. Dioxins are ligands of the aryl hydrocarbon receptor (AHR), that induce AHR-mediated biochemical and toxic responses and are persistent in the environment. 2,3,7,8- tetrachlorodibenzo para dioxin (TCDD) is the prototypical AHR ligand and its effects represent dioxins. TCDD induces toxicity, immunosuppression and is a suspected tumor promoter. The role of TCDD in cancer however is debated and context-dependent. Environmental particulate matter, polycyclic aromatic hydrocarbons, perfluorooctane sulfonamide, endogenous AHR ligands, and cAMP signaling activate AHR through TCDD-independent pathways. The effect of activated AHR in cancer is context-dependent. The ability of FDA-approved drugs to modulate AHR activity has sparked interest in their repurposing for cancer therapy. TCDD by interfering with endogenous pathways, and overstimulating other endogenous pathways influences all stages of cancer. Herein we review signaling mechanisms that activate AHR and mechanisms by which activated AHR modulates signaling in cancer including affected metabolic pathways.