[Effects of miR-144 on proliferation, apoptosis and cisplatin resistance by targeting MYCN in pediatric neuroblastoma].

Objective: To investigate the effects and mechanisms of miR-144 on proliferation, apoptosis and cisplatin (DDP) resistance of neuroblastoma cells. Methods: Real-time fluorescence quantitative PCR (RT-qPCR) was used to detect the mRNA expressions of miR-144 and MYCN in neuroblastoma cell lines, including SH-SY5Y and SK-N-SH, and human umbilical vein endothelial cells HUVEC. The miR-negative control, miR-144 mimics, si-negative control, si-MYCN, miR-144 mimics and pcDNA, miR-144 mimics and pcDNA-MYCN co-transfected SH-SY5Y cells were described as miR-NC, miR-144, si-NC, si-MYCN, miR-144+ pcDNA and miR-144+ pcDNA-MYCN group, respectively. The half maximal inhibitory concentration (IC(50)) and cell proliferation were detected by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) assay. The protein expressions of MYCN, p21, cyclin D1, Bax, Bcl-2 were analyzed by western blot. Cell apoptosis was detected by flow cytometry. The cell fluorescence activity was detected by double luciferase reporter gene assay. Results: Compared with HUVEC cells, the expressions of miR-144 in neuroblastoma cells SH-SY5Y and SK-N-SH significantly decreased, while the mRNA and protein expression of MYCN significantly increased. The IC(50) of DDP was 9.16 µg/ml in SH-SY5Y cells. The absorbance value in 490nm (A(490) value) of miR-144 group was 0.30±0.03, significantly lower than 0.46±0.03 of miR-NC group. The cell apoptotic rate of miR-144 group was 26.94%±2.01%, significantly higher than 9.68%±0.52% of miR-NC group. The IC(50) value of DDP in miR-144 group was 2.95±0.26, significantly lower than 9.23±0.61 of miR-NC group. The expressions of p21, cyclin D1, Bax, Bcl-2 in miR-NC and miR-144 group were 2.67±0.19, 0.41±0.04, 2.12±0.21, 0.18±0.01 and 1.01±0.07, 1.00±0.06, 1.00±0.05, 1.00±0.06, respectively, with statistical significance (all P<0.05). Knockdown of MYCN showed the similar effects with those of miR-144 overexpression in SH-SYSY cells. MiR-144 significantly inhibited the fluorescence activity of ectopic MYCN expressing cells and negatively regulated the expression of MYCN. Overexpression of MYCN can reverse the effects of miR-144 on proliferation inhibition, apoptosis promotion and sensitization of SH-SY5Y cells to DDP. Conclusion: MiR-144 inhibits proliferation, promotes apoptosis and enhances the sensitivity of neuroblastoma cells to DDP through targeting MYCN, which provides a potential treatment for neuroblastoma.