Molecular biology of the Ah receptor and its role in carcinogenesis.
The aryl hydrocarbon receptor (AhR) is a ligand-activated nuclear transcription factor that mediates responses to toxic halogenated aromatic toxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polynuclear aromatic hydrocarbons, combustion products, and numerous phytochemicals such as flavonoids and indole-3-carbinol (I3C). The nuclear AhR complex is a heterodimer containing the AhR and AhR nuclear translocator (Arnt) proteins, and the molecular mechanism of AhR action is associated with binding of the heterodimer to dioxin responsive elements (DREs) in regulatory regions of Ah-responsive genes. TCDD, a 'xenodioxin', is a multi-site carcinogen in several species and possibly in humans, whereas natural AhR ligands including I3C and flavonoids tend to protect against cancer. Both TCDD and phytochemicals inhibit estrogen-induced breast and endometrial cancer, and the molecular mechanisms of this common response will be described.
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Department of Veterinary Physiology & Pharmacology, Texas A&M University, 4466 TAMU, College Station, TX 77843-4466, USA. ssafe@cvm.tamu.edu
D000818:Animals; D001943:Breast Neoplasms / Q000188:drug therapy / Q000209:etiology*; D016889:Endometrial Neoplasms / Q000188:drug therapy / Q000209:etiology*; D047628:Estrogen Receptor alpha; D005260:Female; D006801:Humans; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D018336:Receptors, Aryl Hydrocarbon / Q000187:drug effects / Q000502:physiology*; D011960:Receptors, Estrogen / Q000502:physiology
D047628:Estrogen Receptor alpha; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D011960:Receptors, Estrogen