The Anti-tumor Role And Mechanism Of MiR-433 In Bladder Cancer

Bladder cancer (BCa) is the most common malignancy of the urinary tract. It is the seventh most common cancer in males and the 17th most common in females. It is an aggressive epithelial tumor characterized by a high rate of early systemic dissemination. Approximately one third of BCa patients develop locally invasive or metastatic disease. Although numerous therapeutic strategies have been improved upon and utilized in recent years, radical cystectomy remains the standard of care for invasive BCa, with a 5-year survival reported to be as low as 62% in the current literature. These data support continuing efforts to develop novel and more effective therapeutic strategies.MicroRNAs (miRNAs) are a class of short (19-22 nucleotides) noncoding RNA sequences that suppress gene expression through sequence-specific binding with the 3’ untranslated region (3’-UTR) of a target mRNA. Emerging evidence reveals that disordered miRNA expression contributes to the initiation and progression of human BCa.Our research aimed to explore the inhibition effect to progression effect and molecular mechanism of miR-433 in bladder cancer. The main investigations and results are as follows:1) miR-433 is down-regulated in bladder cancer. To evaluate the expression of miR-433 in bladder cancer, quantitative real-time PCR (qRT-PCR) was performed in 13 pairs of clinical BCa tissues and adjacent non-cancerous tissues, as well as in three types of urinary bladder cancer cell lines T24, UM-UC-3, and 5637. The expression level of miR-433 was generally lower in tumor tissue than in non-tumor tissue. The examination of miR-433 in three different bladder cancer lines also showed significant downregulation compared with SV-HUC-1 cell line.2) The results of BSP revealed that methylation levels of miR-433 were significantly higher in bladder cancer cell lines (T24, UM-UC-3, and 5637). Treatment with 5-Aza-2’-deoxycytidine treatment (5-Aza-CdR) significantly upregulated the expression of miR-433.3) Overexpression of miR-433 inhibits proliferation and colony formation in bladder cancer cells. Furthermore, Overexpression of miR-433 could also inhibit cell motility and induces the EMT by regulating Akt/GSK-3β/Snail signaling.4) We used two methods to screen for potential direct targets of miR-433: bioinformatics prediction and gene expression microarray analysis. CREB1 and c-Met were identified as the direct targets of miR-433.5) Repression of CREB1 or c-Met by siRNA inhibited cell motility and induced EMT by regulating Akt/GSK-3β/Snail signaling, which phenocopied the effect of miR-433 on cell motility and EMT. Moreover, the overexpression of CREBl expression was an independent prognostic factor for overall survival in patients with bladder cancer.6) miR-409-3p is involved in miR-433-mediated inhibition of cell motility. c-Met could regulate the expression of miR-409-3p and miR-433. Both miR-409-3p and miR-433 could directly target the c-Met. There was a reciprocal regulation between miR-433/miR-409-3p and c-Met.In conclusion, this study indicated that miR-433 was a novel suppressor in bladder cancer through its negative regulation of CREB1 and c-Met.