Cancer cells bind to co-inhibitory molecules on T cell surface such as CTLA-4, PD-1, TIM-3, and LAG-3 which in turn secrete immune-suppressive mediators such as IDO (indoleamine 2,3-dioxygenase) to create an immune subversive environment in the TME [25, 26]. This evidence concerns the gene HAVCR2 and cancer.