PDCD1 and acute myeloid leukemia: In a phase 2 trial, relapsed/refractory AML patients achieve an encouraging response rate and overall survival after treatment with PD-1 inhibitor and azacytidine.14 Limited activity has been also noticed in clinical trials in which single-agent benefits are restricted to patients after allogeneic hematopoietic stem cell transplantation.15 Indeed, a considerable portion of patients fail to experience a response to the immunotherapy in AML.16,17 Hence, elucidating the underlying mechanism driving PD-L1 expression offers a rationale for the prognostic prediction of immunotherapy in AML.