To investigate the role of miR-21 on multidrug resistance (MDR) in non-small cell lung cancer(NSCLC)and to provide experimental and theoretical basis for MDR reversal.
Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was used to determine the mRNA level of miR-21 both in the chemo-sensitivity cell strain A549 and the chemo-resistance cell strain A549/DDP (primary A549/DDP cells). The miR-21 interference sequence was synthesized and transfected into A549/DDP cells by liposome as the carrier. The miR-21 expression level was knocked down and the change of chemo-sensitivity of cells was detected. Effects of miR-21 on the cell apoptosis and cell cycle in miR-21-depleted A549/DDP cells were analyzed by flow cytometry to elucidate the involvement of miR-21 in MDR reversal in NSCLC. The expression of multidrug-resistant proteins Survivin, Cyclin D1, Epidermal growth factor receptor (EGFR), Multidrug resistance-associated protein1 (MRP1) and Lipoprotein receptor-related protein (LRP) were detected by Western blot.
MiR-21 level in multidrug-resistant NSCLC cell line A549/DDP was (5.223±0.316) folds higher than that in A549 cell line (t=48.318, P<0.01). Knockdown of miR-21 in A549/DDP cells significantly reversed their sensitivity to cis-DDP, meanwhile, the value of half maximal inhibitory concentration was significantly decreased compared with control group transfected with empty vector ((22.2±1.2) and (48.6±3.2) μmol/L, t=5.608, P<0.01). Cell apoptosis rate in A549/DDP cell with knockdown of miR-21 was significantly increased compared with primary A549/DDP cell line ((27.7±1.1) % and (16.8±1.1) %, t=10.183, P<0.01). Cell cycle G0/G1 phase in A549/DDP cell with knockdown of miR-21 was significantly decreased compared with primary A549/DDP cell line ((37.5±1.2) % and (43.4±2.3) %, t=8.202, P<0.01). Compared with primary A549/DDP cell line, the expression of Survivin, Cyclin D1, EGFR, MRP1 and LRP in A549/DDP cell with knockdown of miR-21 were significantly decreased ((71.7±4.3)%, t=8.325, P<0.01; (69.4±4.5)%, t=5.162, P<0.01; (52.3±3.2)%, t=8.042, P<0.01; (60.6±4.2)%, t=6.641, P<0.01; (72.9±3.8)%, t=4.566, P<0.01, respectively).
miR-21 silencing reverses the multidrug resistance in lung cancer cell via accelerating cell apoptosis and modulating multidrug resistance-related gene expression. miR-21 may be a potential therapeutic candidate in multidrug resistance patients with lung cancer.