The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that belongs to the bHLH/PAS (basic helix-loop-helix/Per-Arnt-Sim) family of chemosensors.106,107 It mediates many of the toxicities and carcinogenic effects from environmental carcinogens including chloracne, wasting, teratogenicity, immunotoxicity, tumor promotion, and carcinogenicity. The gene discussed is AHR; the disease is neoplasm.