OBJECTIVETo investigate the expressions of miR-34a in bone marrow of adult acute lymphoblastic leukemia (ALL) and its relationship with drug resistance.

METHODSForty-seven cases of newly diagnosed adult ALL were selected and their bone marrow samples were taken at the time of newly diagnosed and relapsed or complete remission; 26 pairs of specimens were in newly diagnosed-complete remission group, and 21 pairs of specimens were in newly diagnosed-relapse group. The expressions of miR-34a in bone marrow samples, CCRF-CEM cells and resistant CEM-C1 cell strains were detected by real-time quantitative PCR. The expression of miR-34a in CCRF-CEM cells was inhibited and was increased in CEM-C1 cells detected by electroporation transfection method. All the cells were incubated at different concentration of camptothecin. The cell survival was analyzed by CCK-8 method, the cell proliferation inhibition rate (%) and resistance index (RI) were calculated.

RESULTSIn newly diagnosed-complete remission group, the miR-34a expression at newly diagnosis was significantly lower than that in complete remission and the control group, the differences were statistically significant (P < 0.05). In newly diagnosed-relapsed group, the miR-34a expressions at newly diagnosis and relapse were lower than those in the control group, the differences were statistically significant (P < 0.05). The expression level in CEM-C1 cells was (2.64 ± 1.37) which significantly lower than that in CCRF-CEM cells (5.14 ± 2.06), the differences were statistically significant (P < 0.05). The expression level of miR-34a in CCRF-CEM cells transfected with miR-34a inhibitor was (3.14 ± 1.15), which significantly lower than that in the miRNA inhibitor-negative control group, the difference was statistically significant (P < 0.05). The cell proliferation inhibition rate of CCRF-CEM cells transfected with miR-34a inhibitor was significantly higher than that in the negative control transfectedcells (P < 0.05), the IC(50) was 28.73 ng/mL and 2167.00 ng/mL respectively, and RI = 75.43. The expression level of miR-34a in CEM-C1 cells transfected with miR-34a mimic was (5.06 ± 1.73), which was significantly higher than that in the miRNA mimics transteted-negative control CEM-C1 cells (P < 0.05). The proliferation inhibition rate in CEM-C1 cells transfected with miR-34a mimic was significantly lower than that in the negative control-transfected cells (P < 0.05). The IC(50) was 112.57 ng/mL and 1.27 ng/mL respectively, and the RI = 88.64.

CONCLUSIONThe expression of miR-34a in bone marrow samples of adult ALL is low which may be associated with the relapse and drug resistance of ALL.