Abstract: Objective To evaluate the effect of miR-140 on the sensitivity of imatinib(IM)-resistant chronic myeloid leukemia (CML) cell strain KBM5R to IM and potential underlying mechanism. Methods The expression level of miR-140 and Bcl-2 in CML cells KBM5 and IM resistant CML cells KBM5R were detected by RT-qPCR and Western blot, respectively. KBM5R cells were transfected with miR-NC or miR-140 mimic, and then incubated with 25-100 nmol/L IM for 24 h. Cell viability was examined by CCK-8 assay. KBM5R cells transfected with miR-NC or miR-140 mimic were examined with 100 nmol/L IM for 24 h then cell apoptosis was detected by flow cytometry; Mitochondrial membrane potential was detected by JC-1 staining, and cleaved caspase-3 expression was detected by Western blot.The targeting relation between miR-140 and Bcl-2 was verified by bioinformatics and fluorescence activity analysis. Results Compared with KBM5 cells, the expression of miR-140 in KBM5R cells was significantly decreased (P＜0.01) and the expression of Bcl-2 was significantly increased(P＜0.001). In the presence of IM, compared with the miR-NC group, the cell viability in miR-140 mimic group was significantly decreased (P＜0.01 or P＜0.001); Cell apoptosis was significantly increased(P＜0.001); Mitochondrial membrane potential was significantly decreased (P＜0.001), and cleaved caspase-3 expression was significantly increased(P＜0.001). Bcl-2 was a target of miR-140. Conclusions miR-140 may increase the sensitivity of KBM5R cells to IM by inhibiting the target gene Bcl-2.

Key words: miR-140, Bcl-2, KBM5 cells, imatinib, sensitivity