Robert Sucher¹, Katharina Kurz², Guenter Weiss², Raimund Margreiter¹, Dietmar Fuchs³ and Gerald Brandacher¹

¹Center of Operative Medicine, Department of Visceral, Transplant and Thoracic Surgery, ²Department of Internal Medicine I, ³Division of Biological Chemistry, Biocenter, Innsbruck Medical University, Austria.  

Abstract

Immune escape is a fundamental trait of cancer in which the Th1-type cytokine interferon-γ (IFN-γ) seems to play a key role. Among other tumoricidal biochemical pathways, IFN-γ induces the tryptophan-degrading enzyme indoleamine 2,3-dioxygenase (IDO) in a variety of cells including macrophages, dendritic cells (DCs) and tumor cells. IDO activity has been shown to reflect the extent and the course in a plethora of malignancies including prostate, colorectal, pancreatic, cervical, endometrial, gastric, lung, bladder, ovarian, esophageal and renal cell carcinomas, glioblastomas, mesotheliomas, and melanomas. Furthermore IDO activity during malignant tumor diseases seems to be part of the tumoricidal immune defense strategy, which in the long run is detrimental to the host, when tryptophan deprivation and production of pro-apoptotic tryptophan catabolites counteract T-cell responsiveness.