There is evidence that T cells lose their effector function and ability to kill tumor cells when stimulated by tumor antigens, which may be due to the increasing diversity and number of inhibitory receptors, including CD274, PDCD1LG2, HAVCR2, CTLA4, LAG3, PDCD1, TIGIT [21, 23, 51–53]. Here, PDCD1 is linked to neoplasm.