HAVCR2 and neoplasm: PD-1, CTLA4, LAG3, TIGIT, and TIM-3 (HAVCR2) are known as inhibitory molecules expressed in exhausted T cells that have an impaired ability to kill tumors because they neither respond to T cell receptor stimulation nor secrete anti-tumor cytokines such as interferon γ and tumor necrosis factor-α (26).