Effects of 1-methyltryptophan stereoisomers on IDO2 enzyme activity and IDO2-mediated arrest of human T cell proliferation

Feng Qian, Jianqun Liao, Jeannine Villella, Robert Edwards, Pawel Kalinski, Shashikant Lele, Protul Shrikant, Kunle Odunsi

Research output: Contribution to journalArticle

42 Scopus citations

Abstract

IDO2 is a newly discovered enzyme with 43 % similarity to classical IDO (IDO1) protein and shares the same critical catalytic residues. IDO1 catalyzes the initial and rate-limiting step in the degradation of tryptophan and is a key enzyme in mediating tumor immune tolerance via arrest of T cell proliferation. The role of IDO2 in human T cell immunity remains controversial. Here, we demonstrate that similar to IDO1, IDO2 also degrades tryptophan into kynurenine and is inhibited more efficiently by Levo- 1-methyl tryptophan (L-1MT), an IDO1 competitive inhibitor, than by dextro-methyl tryptophan (D-1MT). Although IDO2 enzyme activity is weaker than IDO1, it is less sensitive to 1-MT inhibition than IDO1. Moreover, our results indicate that human CD4+ and CD8+ T cell proliferation was inhibited by IDO2, but both L-1MT and D-1MT could not reverse IDO2-mediated arrest of cell proliferation, even at high concentrations. These data indicate that IDO2 is an inhibitory mechanism in human T cell proliferation and support efforts to develop more effective IDO1 and IDO2 inhibitors in order to overcome IDO-mediated immune tolerance.

Original languageEnglish (US)
Pages (from-to)2013-2020
Number of pages8
JournalCancer Immunology, Immunotherapy
Volume61
Issue number11
DOIs
StatePublished - Nov 1 2012

Keywords

  • Human
  • IDO2
  • L-1MT
  • T cell

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology
  • Oncology
  • Cancer Research

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