Natural (tryptophan) metabolites—mediated activation of aryl hydrocarbon receptor inhibits cancer stem cell signaling: what does it mean to prevent cancer recurrence?

Environmental pollutes and toxicants have long been believed as the drivers for cancer initiation and progression. The aryl hydrocarbon receptor (AhR) is one of the master regulators of the metabolism of the environmental toxicants in the cells. The AhR ligands which act as agonist have been identified in a broad range such as air pollutes of Dioxin (also called TCDD) in mist, Polycyclic aromatic hydrocarbon found in soil and particulate matter suspended in air, benzoapyrene found in atmospheric wood burning, indigo dye and dietary carotenoids (1). Ligand bound AhR can be released from HSP90-AhR complex and enter into the nucleus. As a transcription factor with basic helix-loop-helix/Per-Arnt-Sim (bHLH-PAS) domains, AhR nuclear translocation can promote transcription of several genes whose encoding proteins catalyze the metabolism and conjugation of xenobiotics or carcinogens such as CYP1A1 in which gene promoter embeds dioxin response elements (DREs) (1).