PMID- 27058624 OWN - NLM STAT- MEDLINE DCOM- 20171226 LR - 20210109 IS - 1949-2553 (Electronic) IS - 1949-2553 (Linking) VI - 7 IP - 22 DP - 2016 May 31 TI - Gene silencing of indoleamine 2,3-dioxygenase 2 in melanoma cells induces apoptosis through the suppression of NAD+ and inhibits in vivo tumor growth. PG - 32329-40 LID - 10.18632/oncotarget.8617 [doi] AB - Indoleamine 2,3-dioxygenase 2 (IDO2) is a newly discovered enzyme that catalyzes the initial and rate-limiting step in the degradation of tryptophan. As a homologous protein of IDO1, IDO2 plays an inhibitory role in T cell proliferation, and it is essential for regulatory T cell (Treg) generation in healthy conditions. Little is known about the immune-independent functions of IDO2 relevant to its specific contributions to physiology and pathophysiology in cancer cells. The purpose of this study was to assess the impact of IDO2 gene silencing as a way to inhibit B16-BL6 cancer cells in a murine model. Here, for the first time, we show that knockdown of IDO2 using small interfering RNA (siRNA) inhibits cancer cell proliferation, arrests cell cycle in G1, induces greater cell apoptosis, and reduces cell migration in vitro. Knockdown of IDO2 decreased the generation of nicotinamide adenine dinucleotide (NAD+) while increasing the generation of reactive oxygen species (ROS). We further demonstrate that cell apoptosis, induced by IDO2 downregulation, can be weakened by addition of exogenous NAD+, suggesting a novel mechanism by which IDO2 promotes tumor growth through its metabolite product NAD+. In addition to in vitro findings, we also demonstrate that IDO2 silencing in tumor cells using short hairpin RNA (shRNA) delayed tumor formation and arrested tumor growth in vivo. In conclusion, this study demonstrates a new non-immune-associated mechanism of IDO2 in vitro and IDO2 expression in B16-BL6 cells contributes to cancer development and progression. Our research provides evidence of a novel target for gene silencing that has the potential to enhance cancer therapy. FAU - Liu, Yanling AU - Liu Y AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. AD - Jiangxi University of Technology, Nanchang, China. AD - Jiangxi Provincial Key Laboratory of Immunotherapy, Nanchang, China. AD - Department of Surgery, Pathology, and Oncology, University of Western Ontario, London, Canada. FAU - Zhang, Yujuan AU - Zhang Y AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. AD - Jiangxi Provincial Key Laboratory of Immunotherapy, Nanchang, China. FAU - Zheng, Xiufen AU - Zheng X AD - Department of Surgery, Pathology, and Oncology, University of Western Ontario, London, Canada. FAU - Zhang, Xusheng AU - Zhang X AD - Department of Surgery, Pathology, and Oncology, University of Western Ontario, London, Canada. FAU - Wang, Hongmei AU - Wang H AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. FAU - Li, Qin AU - Li Q AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. FAU - Yuan, Keng AU - Yuan K AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. AD - Jiangxi Provincial Key Laboratory of Immunotherapy, Nanchang, China. FAU - Zhou, Nanjing AU - Zhou N AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. AD - Jiangxi Provincial Key Laboratory of Immunotherapy, Nanchang, China. FAU - Yu, Yanrong AU - Yu Y AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. AD - Jiangxi Provincial Key Laboratory of Immunotherapy, Nanchang, China. FAU - Song, Na AU - Song N AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. FAU - Fu, Jiamin AU - Fu J AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. FAU - Min, Weiping AU - Min W AD - Institute of Immunotherapy of Nanchang University, and Jiangxi Academy of Medical Sciences, Nanchang, China. AD - Jiangxi Provincial Key Laboratory of Immunotherapy, Nanchang, China. AD - Department of Surgery, Pathology, and Oncology, University of Western Ontario, London, Canada. LA - eng PT - Journal Article PL - United States TA - Oncotarget JT - Oncotarget JID - 101532965 RN - 0 (IDO2 protein, mouse) RN - 0 (Indoleamine-Pyrrole 2,3,-Dioxygenase) RN - 0 (RNA, Small Interfering) RN - 0 (Reactive Oxygen Species) RN - 0U46U6E8UK (NAD) SB - IM MH - Animals MH - *Apoptosis MH - Cell Line, Tumor MH - Cell Movement MH - *Cell Proliferation MH - G1 Phase Cell Cycle Checkpoints MH - Gene Expression Regulation, Enzymologic MH - Gene Expression Regulation, Neoplastic MH - Indoleamine-Pyrrole 2,3,-Dioxygenase/*genetics/metabolism MH - Male MH - Melanoma, Experimental/enzymology/genetics/pathology/*therapy MH - Mice MH - Mice, Inbred C57BL MH - NAD/*metabolism MH - Neoplasm Invasiveness MH - *RNA Interference MH - RNA, Small Interfering/*genetics/metabolism MH - *RNAi Therapeutics MH - Reactive Oxygen Species/metabolism MH - Signal Transduction MH - Skin Neoplasms/enzymology/genetics/pathology/*therapy MH - Time Factors MH - Transfection MH - Tumor Burden PMC - PMC5078016 OTO - NOTNLM OT - IDO2 OT - NAD+ OT - apoptosis OT - neoplasm OT - siRNA COIS- The authors of this manuscript have no conflicts of interest to disclose. EDAT- 2016/04/09 06:00 MHDA- 2017/12/27 06:00 PMCR- 2016/05/31 CRDT- 2016/04/09 06:00 PHST- 2015/12/13 00:00 [received] PHST- 2016/03/14 00:00 [accepted] PHST- 2016/04/09 06:00 [entrez] PHST- 2016/04/09 06:00 [pubmed] PHST- 2017/12/27 06:00 [medline] PHST- 2016/05/31 00:00 [pmc-release] AID - 8617 [pii] AID - 10.18632/oncotarget.8617 [doi] PST - ppublish SO - Oncotarget. 2016 May 31;7(22):32329-40. doi: 10.18632/oncotarget.8617.