Meanwhile, it could limit the infiltration, effector function, and immune memory of antigen-specific T cells and promote the expression of various immunosuppressive receptors (e.g., PD-1, TIM3, CTLA-4, and LAG3), which thereby promoted T cell exhaustion in the tumor, and assisted tumor immune escape, tumor proliferation and metastasis (Vignali and Kuchroo, 2012; Fu et al., 2016; Sawant and Yano, 2019). Here, PDCD1 is linked to neoplasm.