PDCD1 and cancer: Notably, this tumoral “immune escape” is mostly mediated by programmed death protein-1 (PD-1) and cytotoxic T-lymphocyte associated antigen-4 (CTLA4), which are expressed on T cells’ plasmalemma and may trigger inhibitory pathways blocking the anti-cancer immune response, thus explaining the revolutionary use of anti-PD-1/PD-L1 and anti-CTLA-4 agents in several tumors.