The Mechanism Of Leukemia Stem Cell-released Microvesicles By MicroRNA34a

Objective: Investigate whether Leukemia stem cells released MVs(LMVs)can regulate the malignance of AML cells and whether overexpression of tumor suppressive microRNA(miR),miR34 a,is able to interrupt.Methods: Firstly extracted CD34+/CD38--Lekemia Stem Cells(LSCs)from acute myeloid leukemia cell lines KG1 a.LSCs were transfected with miRNA control(miRCtrl)or miR34 a mimic for producing LMVs,respectively,defined as,LMVsmiRCtrl 、LMVsmiR34a and LMVs.The effects of LMVs on the proliferation,migration,and apoptosis of AML cells were determined.The levels of miR34 a targets,caspase-3 and T cell immunoglobulin mucin-3(Tim-3),were analyzed.Results:(1)LSCs were successfully isolated from KG1 a cells.After micro-bead sorting procedures and analyzed by flow cytometry,more than 95% of cells were CD34+CD38-and concerted LSCs.(2)The level of miR34 a in LSCs was significantly elevated after miR34 a mimic transfection when compared with miRCtrl transfection or veh.(3)The number of LMVsmiR34 a was higher than that of LMVs or LMVsmiRCtrl.The level of miR34 a in LMVsmiR34 a was much higher than that of LMVs or LMVsmiRCtrl.There was no significant difference of miR34 a level between LMVs and LMVsmiRCtrl.(4)The apoptosis in KG1 a cells was decreased after coincubation with LMVsmiRCtrl when compared with veh or LMVsmiR34 a.There was no significant difference in apoptosis between veh-treated and LMVsmiR34a-treated KG1 a cells.Moreover,the proliferation and migration abilities of AML cells were enhanced after coincubation with LMVsmiRCtrl whereas these effects were absent in KG1 a cells coincubated with LMVsmiR34 a.(5)The activity of caspase-3 was reduced in AML cells coincubated with LMVsmiRCtrl.However LMVsmiR34 a significantly increased the activity of caspase-3 in AML cells.The expression of Tim-3 was upregulated in LMVsmiRCtrl-treated AML cells but was downregulated in LMVsmiR34a-treated AML cells.Conclusion:(1)LMVs promoted proliferation and migration and inhibited apoptosis of AML cells,which were associated with the level of miR34 a.(2)Overexpression of miR34 a not only inhibits the LSC proliferation but also inhibits these effects of LMVs on AML.(3)The miR34 via modulating caspase-3 and Tim-3 levelsinhibits these effects of LMVs on AML.These findings indicate that LMVs support the malignancy of AML cells and targeting of miR34 a in LMVs could offer a novel approach for treatment of AML.