Moreover, PD-1 over-expression on lymphocytes as well as its two ligands PD-L1 and PD-L2 on CD34+ AML cells, may contribute to treatment resistance to azacytidine (137), providing the rationale to combine hypomethylating agents (HMA) and ICPIs in the treatment of AML (76, 140, 141). Here, PDCD1LG2 is linked to acute myeloid leukemia.