KLRG1 and neoplasm: Several checkpoint and inhibitory receptors, such as PD-1 (gene name: PDCD1), CTLA4, TIM-3 (HAVCR2), LAG3, CD39 (ENTPD1), CD160, KLRG1, CD96, BTLA, 2B4, and TIGIT, have been implicated in the reduction of immune activity and response in the tumor micro-environment [30,31,32].