Previous clinical studies in leukemia have shown decreased methylation and increased expression of immune checkpoint molecules such as programmed death receptor 1 (PD-1), PD ligand 1 (PD-L1), and Cytotoxic T-lymphocyte Antigen-4 (CTLA-4) in patients after HMA treatment, prompting combination therapy of HMAs with immune checkpoint blockade antibodies [39,40]. This evidence concerns the gene CTLA4 and leukemia.