MicroRNA-138-5p Regulates The Expression Of PD-L1 In Patients With Acute Myeloid Leukemia

Objective:The aim of this study is to characterize the relative expression levels of PD-L1 and related regulatory microRNAs in peripheral blood mononuclear cells(PBMCs)of patients with acute myeloid leukemia(AML),and to investigate the effect of overexpression of miR-138-5p on the expression of PD-L1 in THP1 cell line and AML primary tumor cell,which is expected to provide predictable biomarkers for immune checkpoint detection of AML,and to provide new target for immunotherapy of AML.Methods:Reverse transcription quantitative polymerase chain reaction(RT-qPCR)was used to detect the expression levels of PD-L1、miR-138-5p and miR-570-3p of PBMCs form 20 patients with primary AML,9 patients with refractory AML,8 AML patients in complete remission(CR)and 20 healthy adults.In addition,transgenic technology was used to up-regulation the expression of miR-138-5p in THP1 cell line and AML primary tumor cells,and then detected the change in PD-L1 expression level by RT-qPCR and Western blot.At the same time,CCK8 KIT and Annexin V-FITC/PI reagent were used to observe the effects of overexpression of miR-138-5p on the proliferation and apoptosis of THP1and AML primary tumor cells.Results:(1)A significantly higher level of PD-L1 mRNA was found in AML patients compared with healthy controls(P<0.001),and the expression level of PD-L1 in refractory AML group was significantly higher than that in the primary AML group(P=0.004).The expression level of PD-1 mRNA in the primary AML group was significantly lower than that in the healthy controls(P<0.001).(2)The expression level of miR-138-5p in PBMCs from primary AML group and refractory AML group were significantly lower than that of healthy controls(P<0.001),and the expression level of miR-138-5p in CR group was higher than that in primary AML group(P=0.017).The expression level of miR-570-3p in primary AML group was significantly lower than that in the healthy controls(P=0.001).(3)There was an inverse correlation between PD-L1 and miR-138-5p in primary AML patients(P=0.011,r~2=0.310),but there was no correlation between PD-L1 and miR-570-3p(P=0.167,r~2=0.104).(4)Overexpression of miR-138-5p reduced the expression of PD-L1 mRNA in AML primary tumor cells,and decreased the expression level of PD-L1 protein both in THP1 cell line and AML primary tumor cells;but up-regulated the expression of miR-138-5p have no effect on the proliferation and apoptosis of THP1 and AML primary tumor cells.Conclusions:We found higher expression of PD-L1 and lower expression of miR-138-5p in PBMCs of AML patients,and an inverse correlation between PD-L1 and miR-138-5p.Overexpression of miR-138-5p reduced the expression of PD-L1 protein both in THP1 cell line and AML primary tumor cells.