Inhibitory effects of microRNA-34a on proliferation of bladder tumor cell line T24 by targeting Notch1

Objective 　To explore the correlation between microRNA-34a (miR-34a) and Notch1, and evaluate the influence of miR-34a overexpression on proliferation of bladder cancer cell line T24. Methods 　Bioinformatics software were used for predicting the binding site of miR-34a and Notch1, and luciferase assay was performed for confirming the direct regulatory relationship between them. miR-34a plasmid was transfected into bladder cancer cell line T24. Notch1 expression was detected by quantitative real-time polymerase chain reaction and Western blotting. Cell proliferation was assayed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Apoptosis and cell cycle were assessed by flow cytometry. Results 　Luciferase assays showed that miR-34a transfection significantly down-regulated the normalized Notch1 3'UTR luciferase activity (P=0.006). Transfection of miR-34a reduced the RNA and protein levels of Notch1. Cell proliferation assay revealed that miR-34a transfection suppressed the proliferation of T24 cells in a time-dependent manner (P < 0.001). Ectopic expression of miR-34a caused significant increase of apoptotic cells (P=0.003) and induced cell cycle arrest at G0-G1 phase in T24 cells (P=0.002). Conclusion 　Overexpressed miRNA-34a can inhibit proliferation of bladder cancer cells by antagonizing Notch1, thus indicating its tumor-suppressive function in bladder cancer.