Abstract B15: MicroRNA-145/145* as a dual tumor-suppressor targeting UHRF1 in bladder cancer
Authors: Matsushita Ryosuke , Seki Naohiko , Yoshino Hirofumi , Goto Yusuke , Miyamoto Kazutaka , Yonemori Masaya , Enokida Hideki , Nakagawa Masayuki 
Published: May 2016

Background: Bladder cancer (BC) can be classified into two categories: non-muscle-invasive BC (NMIBC) and muscle-invasive BC (MIBC). Although 70%–80% of patients are diagnosed with NMIBC, high recurrence rates (50%–70%) are observed in these patients. Moreover, among recurrent cases, 15% of BCs progress to MIBC disease. The five year survival rate for patients with NMIBC is close to 90%, whereas that for patients with MIBC is only approximately 60%. Patients with advanced BC are generally treated with combination chemotherapy consisting of gemcitabine and cisplatin, but progression-free survival is of limited duration. There are currently no effective second-line chemotherapeutic agents for advanced BC. The molecular mechanisms of recurrence and muscle invasion process of BC are not well understood. Therefore, understanding the molecular mechanisms of metastatic pathways underlying advanced BC using currently available genomic approaches might improve therapies for and prevention of the disease.

Our recent study of microRNA (miRNA) expression signature of BC by deep-sequencing revealed that microRNA-145 (miR-145) and microRNA-145* (miR-145*) were significantly down regulated in BC tissues. In miRNA biogenesis, during RISC loading one strand (passenger strand) of miRNA duplex is discarded, while the other strand (guide strand) is retained to direct recruitment of the RISC to target mRNAs. In generally, miR-145* recognized as a passenger strand of pre-miR-145. We hypothesis that these miRNAs function as tumor suppressors in BC. The aim of the present study was to investigate the functional roles of these miRNAs and their modulation of cancer networks in BC cells.

Methods: Expression levels of miR-145, miR-145* and its candidate target gene were evaluated in BC cell lines (T24 and BOY) and BC clinical specimens (71 BCs and 12 normal bladder epitheliums: NBEs) by qRT-PCR methods. The functional studies of miR-145, miR-145* and target gene were performed to investigate cell proliferation, migration and invasion by cancer cell lines. To identify miR-145/145*-regulated molecular targets, genome-wide gene expression analysis, in silico database analysis, and dual-luciferase reporter assays were applied.

Results: The expression levels of miR-145 and miR-145* were significantly reduced in tumor tissues and BC cell lines compared with NBEs (P &lt; 0.0001). The expression levels of miR-145 and miR-145* were analysed for their correlation with one another.Restoration of miR-145 or miR-145* in cancer cells revealed that both miRNAs significantly inhibited cancer cell proliferation, migration and invasion. Our data demonstrated that the gene coding for Ubiquitin-like, containing PHD and RING finger domains 1 (UHRF1) was a direct target of miR-145/145* regulation. Moreover, silencing of UHRF1 significantly inhibited cell proliferation, migration and invasion by bladder cancer cells.

Conclusion: Down-regulation of the miR-145 and miR-145* were frequently observed in BC cells, and these miRNAs significantly inhibited cancer cell proliferation, migration and invasion, suggesting act as tumor-suppressors in BC. To the best of our knowledge, this is the first report demonstrating that dual tumor-suppressive miR-145/145* directly regulated UHRF1 in BC cells. The identification of novel target gene regulated by dual tumor-suppressor miR-145/145* may lead to a better understanding of BC and the development of new therapeutic strategies to treat this disease.

Citation Format: Ryosuke Matsushita, Naohiko Seki, Hirofumi Yoshino, Yusuke Goto, Kazutaka Miyamoto, Masaya Yonemori, Hideki Enokida, Masayuki Nakagawa. MicroRNA-145/145* as a dual tumor-suppressor targeting UHRF1 in bladder cancer. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B15.