OBJECTIVETo explore the expression of PD-L1 in acute leukemia patients, and to analyze the relationship of PD-L1 expression with the patients' clinical characteristics and prognosis.

METHODSThe expression of PD-L1 in leukemia cells of 75 patients including 59 de novo patients and 16 relapse/refractory patients with acute leukemia was detected by the flow cytometry, the clinical information was collected, and the therapeutic efficacy of de novo patients was analyzed.

RESULTSThe PD-L1 was expressed in human acute leukemia cells with total expression rate 32% (24/75), and its expression level in AML-M5 was higher than that in other leukemias [56.3% (9/16) vs 25.4% (15/59)], there was statistical significance (P = 0.019). The PD-L1 possitive rate in relapse/refractory group was higher than that in de novo patient group [(56.3% (9/16) vs 25.4% (15/59)], and there was statistical significance (P = 0.019). In 59 de novo patients, the CR rate of PD-L1 positive group after 1 course of chemotherapy was lower than that in PD-L1 negative group (66.7% vs 71.4%), the CR rate of PD-L1 positive group after 2 courses of chemotherapy was also lower than that in PD-L1 negative group (70% vs 88.6%). The relapse rate and the proportion of refractory patients in PD-L1 possitive group were higher than those in PD-L1 negative group. The expression of PD-L1 did not correlated with the clinical parameters, such as sex, age, extramedullary infiltration, percentage of blast cells in bone marrow, counts of WBC, RBC and platelet, as well as molecular biological features and cytogenetical characteristics.

CONCLUSIONPD-L1 is expressed in human acute leukemia cells, and may be involved in the immune escape and primary resistant mechanisms, PD-L1 may be used as an indicator for evaluation of the the patients' prognosis and reocurrence.