HAVCR2 and neoplasm: In the tumor microenvironment (TME), cancer cells escape from immune functions through the expression of immune checkpoints such as programmed cell death ligand 1 (PD-L1), cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), T-cell immunoglobulin and mucin domain-containing molecule-3 (Tim-3), lymphocyte-activation gene 3 (LAG-3) and T cell immunoglobulin and ITIM domain (TIGIT) 1-5.