title: Central role of IFNgamma-indoleamine 2,3-dioxygenase axis in regulation of interleukin-12-mediated antitumor immunity.
abstract: Sustained intratumoral delivery of interleukin-12 (IL-12) and granulocyte macrophage colony-stimulating factor induces tumor regression via restoration of tumor-resident CD8+ T-effector/memory cell cytotoxicity and subsequent repriming of a secondary CD8+ T-effector cell response in tumor-draining lymph nodes (TDLN). However, treatment-induced T-effector activity is transient and is accompanied with a CD4+ CD25+ Foxp3+ T-suppressor cell rebound. Molecular and cellular changes in posttherapy tumor microenvironment and TDLN were monitored to elucidate the mechanism of counterregulation. Real-time PCR analysis revealed a 5-fold enhancement of indoleamine 2,3-dioxygenase (IDO) expression in the tumor and the TDLN after treatment. IDO induction required IFNgamma and persisted for up to 7 days. Administration of the IDO inhibitor D-1-methyl tryptophan concurrent with treatment resulted in a dramatic enhancement of tumor regression. Enhanced efficacy was associated with a diminished T-suppressor cell rebound, revealing a link between IDO activity and posttherapy regulation. Further analysis established that abrogation of the regulatory counterresponse resulted in a 10-fold increase in the intratumoral CD8+ T-cell to CD4+ Foxp3+ T-cell ratio. The ratio of proliferating CD8+ T-effector to CD4+ Foxp3+ T-suppressor cells was prognostic for efficacy of tumor suppression in individual mice. IFNgamma-dependent IDO induction and T-suppressor cell expansion were primarily driven by IL-12. These findings show a critical role for IDO in the regulation of IL-12-mediated antitumor immune responses.
authors.affiliation: Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York 14214, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Gu
authors.forename: Rachael B
authors.initials: RB
authors.lastname: Rowswell-Turner
authors.forename: Mehmet O
authors.initials: MO
authors.lastname: Kilinc
authors.forename: Nejat K
authors.initials: NK
authors.lastname: Egilmez
mesh_terms: D000818:Animals; D005434:Flow Cytometry; D007108:Immune Tolerance / Q000276:immunology; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology*; D018664:Interleukin-12 / Q000276:immunology*; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout / Q000276:immunology*; D009374:Neoplasms, Experimental; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D018664:Interleukin-12; D007371:Interferon-gamma