OBJECTIVETo investigate the reversal effect of targeted modulation of bcl-2 expression by miR-15a and miR-16 on drug resistance of human colon cancer cells.

METHODSMimics or inhibitors of miR-15a and miR-16 were transfected into HCT8 or HCT8/VCR cells with the help of Lipofectamine 2000. The expressions of miR-15a and miR-16 mRNA were detected by RT-qPCR. The levels of bcl-2 and P-gp proteins were measured by Western blot. The inhibitory effects of VCR on growth of HCT8 and HCT8/VCR cells were detected by CCK8.

RESULTSAfter transfection of the mimics, the expression of miR-15a in the blank control group, negative control group and miR-15a mimic group was 1.00, 0.87 ± 0.24, and 223.44 ± 59.07, respectively, and miR-15a was increased significantly (P < 0.001). The expression of miR-16 in the blank control group, negative control group and miR-16 mimic group was 1.00, 0.66 ± 0.19, and 107.32 ± 22.58, respectively, and miR-16 expression was increased significantly (P < 0.001). The Western blot assay showed that the relative expressions of bcl-2 protein in the blank control group, negative control group, miR-15a mimic group and miR-16 mimic group were 1.00, 0.97 ± 0.02, 0.51 ± 0.06, and 0.65 ± 0.03, respectively, and the expression of bcl-2 protein was decreased significantly (P < 0.05), however, the expressions of P-gp protein showed no significant difference. The CCK8 test showed that at 1, 5, 25 and 125 µg/ml concentration of VCR, the survival rates of HCT8/VCR cells were basically the same in the blank control group, negative control group, miR-15a mimic group and miR-16 mimic group, but the survival rate of HCT8/VCR cells was significantly decreased after transfection of mimics (P < 0.05). After transfection of the inhibitors, the expressions of both miR-15a and miR-16 were decreased significantly (P < 0.001). The Western blot showed that the expression of bcl-2 protein was increased (P < 0.05), while the expression of P-gp protein showed no significant difference. The CCK8 test showed that the survival rate of HCT8 cells which were transfected with inhibitors was significantly higher than that of the blank control group (P < 0.05).

CONCLUSIONSmiR-15a and miR-16 may reverse the drug resistance in human colon cancer cells. A possible mechanism is regulating the expression of bcl-2.

ATP-Binding Cassette, Sub-Family B, Member 1 ; Apoptosis ; Apoptosis Regulatory Proteins ; metabolism ; Cell Line, Tumor ; Colonic Neoplasms ; Drug Resistance ; Humans ; MicroRNAs ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; genetics ; metabolism ; RNA, Messenger ; Transfection