Feng, ShanCheng, XiZhang, LinLu, XueminChaudhary, SeemaTeng, RuifangFrederickson, ChristianChampion, Matthew M.Zhao, RenCheng, LiangGong, YiyiDeng, HaitengLu, Xin2019-08-022019-08-022018-10-02Feng, S., Cheng, X., Zhang, L., Lu, X., Chaudhary, S., Teng, R., … Lu, X. (2018). Myeloid-derived suppressor cells inhibit T cell activation through nitrating LCK in mouse cancers. Proceedings of the National Academy of Sciences of the United States of America, 115(40), 10094–10099. doi:10.1073/pnas.1800695115https://hdl.handle.net/1805/20169Potent immunosuppressive mechanisms within the tumor microenvironment contribute to the resistance of aggressive human cancers to immune checkpoint blockade (ICB) therapy. One of the main mechanisms for myeloid-derived suppressor cells (MDSCs) to induce T cell tolerance is through secretion of reactive nitrogen species (RNS), which nitrates tyrosine residues in proteins involved in T cell function. However, so far very few nitrated proteins have been identified. Here, using a transgenic mouse model of prostate cancer and a syngeneic cell line model of lung cancer, we applied a nitroproteomic approach based on chemical derivation of 3-nitrotyrosine and identified that lymphocyte-specific protein tyrosine kinase (LCK), an initiating tyrosine kinase in the T cell receptor signaling cascade, is nitrated at Tyr394 by MDSCs. LCK nitration inhibits T cell activation, leading to reduced interleukin 2 (IL2) production and proliferation. In human T cells with defective endogenous LCK, wild type, but not nitrated LCK, rescues IL2 production. In the mouse model of castration-resistant prostate cancer (CRPC) by prostate-specific deletion of Pten, p53, and Smad4, CRPC is resistant to an ICB therapy composed of antiprogrammed cell death 1 (PD1) and anticytotoxic-T lymphocyte-associated protein 4 (CTLA4) antibodies. However, we showed that ICB elicits strong anti-CRPC efficacy when combined with an RNS neutralizing agent. Together, these data identify a previously unknown mechanism of T cell inactivation by MDSC-induced protein nitration and illuminate a clinical path hypothesis for combining ICB with RNS-reducing agents in the treatment of CRPC.en-USPublisher PolicyLCKImmune checkpoint blockadeMyeloid-derived suppressor cellsProstate cancerProtein nitrationArticle