It is often pointed out

It is often pointed out that tumor FMK can escape immune cells by changing their antigenicity through the modification of targeted peptide sequences or reduction of HLA-molecule expression (Schreiber et al., 2011). This is usually the case when immune therapies with antigen-specific monoclonal CTLs fail. Given their functional similarity to natural iNKT cells, re-iNKT cells, which would be available at an unlimited supply, would be expected to exert cellular adjuvant effects via DCs following the activation of tumor antigen-specific polyclonal CTLs and NK cells, although the level of cytokine production induced by α-GalCer DCs was lower in re-iNKT than in parental cells and there was less cytokine variety. In addition, the NK cell-like cytotoxicity of re-iNKT cells could assist with TCR-independent antitumor responses via NKG2D- and DNAM-1-mediated direct killing of tumor cells. TIGIT inhibits DNAM-1 function via the same ligands not only by competitively inhibiting ligand binding but also through direct interaction with DNAM-1, which physically prevents DNAM-1 homodimerization (Johnston et al., 2014; Stanietsky et al., 2009; Yu et al., 2009). The balance between DNAM-1 and TIGIT expression may control iNKT cell cytotoxicity; that is, re-iNKT and parental iNKT cells express equal levels of DNAM-1, but re-iNKT cells do not express TIGIT, which may enable stronger cytotoxic signaling than primary iNKT cells. In addition, TIGIT was recently identified as a new exhaustion marker expressed in tumor-infiltrating lymphocytes and is thought to be an attractive candidate for blockade, along with PD-1, to reverse CTL dysfunction in cancer (Johnston et al., 2014). That re-iNKT cells scarcely express TIGIT and PD-1 is a property that would be beneficial for cells used in cancer immunotherapy. In addition, iNKT cells reportedly control the tumor microenvironment by killing tumor-associated macrophages (Song et al., 2009) and converting myeloid-derived suppressor cells into APCs (De Santo et al., 2010). The general mechanism of the direct killing activity in re-iNKT cells is unknown. The low expression and hypermethylation of BCL11B may be partly responsible (Figures 2C and S3B), as the loss of the Bcl11b expression induces lineage reprogramming from murine T cells to NK cells (Li et al., 2010). Thus, Th1-biased cytokine production and direct TCR-independent killing may enable re-iNKT cells to exert therapeutic effects against the tumor microenvironment. Nevertheless, it will be important to gather additional therapeutic evidence in vitro and in vivo using appropriate animal models, as the characteristics and responsiveness of the re-iNKT cells were not completely identical to those of parental iNKT cells.
Experimental Procedures
Author Contributions
Acknowledgments The authors thank Drs. Shinya Yamanaka, Yasuhiro Yamada, Hiroshi Kawamoto, Yuta Mishima (Kyoto University), and Tetuya Nakatsura (NCC) for helpful discussion; Dr. Ken Nishimura (University of Tsukuba), Ms. Manami Ohtaka (AIST), Kaho Hiramatsu (ACCRI), and Yukiko Kobayashi (Kyoto University) for technical assistance; Dr. Peter Karagiannis (Kyoto University) for editing the manuscript; and Dr. Hiromitsu Nakauchi (The University of Tokyo) for providing the cell lines. This work was supported in part the Japanese Ministry of Education, Culture, Sports, Science and Technology, 23592022 (Y.U.), 26462078 (Y.U.), 25861253 (R.Z.), 26670578 (S. Kaneko), 25114707 “Carcinogenic Spiral”(S. Kaneko), and Core Center for iPS Cell Research of Research Center Network for Realization of Regenerative Medicine (S. Kaneko) by the Japanese Ministry of Education, Culture, Sports, Science and Technology; the Aichi Cancer Research Foundation (Y.U.); Takeda Science Foundation (K.K.), The National Cancer Center Research and Development Fund (25-A-7, Y.U.); Daiwa Securities Health Foundation (Y.U.); Pancreas Research Foundation of Japan (Y.U.); and SENSHIN Medical Research Foundation (Y.U.). S. Kaneko is a founder and shareholder at AsTlym Co., Ltd, and Thyas Co., Ltd. M.N. is a founder and CTO of TOKIWA-Bio Inc.