Oncogenic miRNA-182-5p Targets Smad4 and RECK in Human Bladder Cancer

Hiroshi Hirata,Z Laura Tabatabai,Varahram Shahryari,Rajvir Dahiya,Koji Ueno,Yuichiro Tanaka,Yuji Hinoda,Fazlul H Sarkar

doi:10.1371/journal.pone.0051056

Abstract

Onco-miR-182-5p has been reported to be over-expressed in bladder cancer (BC) tissues however a detailed functional analysis of miR-182-5p has not been carried out in BC. Therefore the purpose of this study was to: 1. conduct a functional analysis of miR-182-5p in bladder cancer, 2. assess its usefulness as a tumor marker, 3. identify miR-182-5p target genes in BC. Initially we found that miR-182-5p expression was significantly higher in bladder cancer compared to normal tissues and high miR-182-5p expression was associated with shorter overall survival in BC patients. To study the functional significance of miR-182-5p, we over-expressed miR-182-5p with miR-182-5p precursor and observed that cell proliferation, migration and invasion abilities were increased in BC cells. However cell apoptosis was inhibited by miR-182-5p. We also identified Smad4 and RECK as potential target genes of miR-182-5p using several algorithms. 3′UTR luciferase activity of these target genes was significantly decreased and protein expression of these target genes was significantly up-regulated in miR-182-5p inhibitor transfected bladder cancer cells. MiR-182-5p also increased nuclear beta-catenin expression and while Smad4 repressed nuclear beta-catenin expression. In conclusion, our data suggests that miR-182-5p plays an important role as an oncogene by knocking down RECK and Smad4, resulting in activation of the Wnt-beta-catenin signaling pathway in bladder cancer.

Highlights

Bladder cancer (BC) is the third leading cause of death among urological tumors and the most common histological type of bladder cancer is urothelial carcinoma (UC), formerly known as transitional cell carcinoma (TCC) [1]
We investigated the association of miR-182-5p and several clinical parameters as shown in Figure 1B and observed that high miR-182-5p expression was significantly associated with shorter overall survival
We divided the 18 bladder cancer patients into two categories based on the median value and Kaplan Meier plots showed that overall survival was shorter in the high miR-182-5p expressing group (p value = 0.0349, Log-rank test) (Figure 1-C)

Summary

Introduction

Bladder cancer (BC) is the third leading cause of death among urological tumors and the most common histological type of bladder cancer is urothelial carcinoma (UC), formerly known as transitional cell carcinoma (TCC) [1]. 75% of patients are ‘‘non-muscle invasive UC (pTa, pTis, pT1) and have a 5-year survival rate of between 88–98% [2]. The common treatment for these patients is endoscopic resection [1,3]. Patients with muscle invasive UC are usually treated with radical cystectomy or chemo radiotherapy [1,4]. Half of muscle invasive UC patients develop subsequent metastatic disease after the first aggressive treatment [1,5]. Previous studies have identified several potential molecular biomarkers for bladder cancer [6,7]. Inactivation of tumor suppressor genes TP53 and Rb and Ras oncogene activation have been regarded as important key players in bladder cancer carcinogenesis [6]

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Conclusion