Chapter 21: Role of kynurenine pathway in cancer biology

Abstract

The kynurenine pathway for tryptophan catabolism is responsible for the production of the essential cofactor NAD+, but many of the pathway catabolites play roles in many different disease states. The involvement of the kynurenine pathway enzymes and catabolites in cancer occurs via both immune and nonimmune mechanisms. In this chapter, the consequences of the immune response to developing tumors will be summarized, and the role played by indoleamine 2,3-dioxygenase in enabling tumor immune escape via tryptophan depletion will be outlined. In addition, the role played by other enzymes, such as tryptophan 2,3-dioxygenase—which modulates the immune response by producing kynurenine—is described. Further to this, the involvement of downstream enzymes and catabolites of the pathway in tumor development is discussed.