Other two common events concurring with immune escape instauration are the blocking of the PD-1 receptor on immune system cells by means of its ligands, namely programmed death-ligand 1 or 2 (PD-L1 or PD-L2), expressed by cancer cells, and the recruitment of myeloid-derived suppressor cells (MDSCs) (Figure 2). Here, CD274 is linked to cancer.