Tim-3 and Tim-4 as the potential targets for antitumor therapy

Both Tim-3 and Tim-4 belong to the T-cell immunoglobulin and mucin domain (Tim) gene family, which plays a critical role in immunoregulation. Tim-3 has been suggested as a negative regulator of anti-tumor immunity due to its function on inducing T cells exhaustion in cancer. In addition to its expression on exhausted T cells, Tim-3 also has been reported to up-regulate on nature killer (NK) cells and promote NK cells functionally exhausted in cancer. While Tim-3 selectively expression on most types of leukemia stem cells, it promotes the progression of acute myeloid leukemia. Recently, data from experimental models of tumor discovered that Tim-3 and Tim-4 up-regulation on tumor associated dendritic cells and macrophages attenuated the anti-tumor effects of cancer vaccines and chemotherapy. Moreover, co-blockage of Tim-3 and PD-1, Tim-3 and CD137, Tim-3 and carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) could enhance cell-mediated immunity in advanced tumor, and combined treatment with anti-Tim-3 and anti-Tim-4 mAbs further increase the efficacy of cancer vaccines. The therapeutic manipulation of TIM-3 and TIM-4 may provide a novel strategy to improve the clinical efficacy of cancer immunotherapy.