Abstract 1619: MicroRNA-466 regulates bone metastasis by targeting RUNX2 in prostate cancer
Authors: Majid Shahana , Nip Hanna , Dar Altaf A. , Saini Sharanjot , Shahryari Varahram , Yamamura Soichiro , Mitsui Yozo , Bucay Nathan , Deng Guoren , Dahiya Rajvir , Tanaka Yuichiro 
Published: July 2016

MicroRNAs are small, non-coding RNAs that regulate gene expression by targeted repression of transcription and translation. The main objective of this study was to investigate the role of microRNA-466 (miR-466) in prostate carcinogenesis (PC). The expression of miR-466 was significantly suppressed in PC tissue samples and cell lines (PC3, Du145, LNCaP, MDaPCa2b and LAPC4) when compared with normal tissues and a non-malignant cell line (RWPE1). Receiver operating curve analysis showed that miR-466 expression is an independent diagnostic predictor to discriminate between normal and tumor cases. Functionally ectopic expression of miR-466 caused a robust decrease in cell migration, invasion and proliferation of prostate cancer cells. We found that miR-466 exerted these functional effects by directly targeting the oncogenic RUNX2, a key transcription factor in PC. Over-expression of miR-466 in prostate cancer cells suppressed luciferase activity of reporter plasmids containing wild type 3’UTR sequences complementary to RUNX2, which was abolished by 3’UTR mutations. miR-466 reduced RUNX2 regulated downstream molecules such as ANGPT1, ANGPT4, MMP11, Osteopontin (SPP1), and Osteocalcin (OC). MiR-466 also inhibited genes involved in cell proliferation, migration and invasion such as pAKT, FYN and FAK. To determine the biological significance of miR-466 in prostate cancer, we performed parallel experiments in the non-malignant cell line RWPE1 followed by functional assays. Attenuation of miR-466 induced oncogenic characteristics such as increased proliferation, migration and invasion in RWPE1 cells. To examine the in vivo antitumor effects of miR-466, we performed primary and metastatic mouse model experiments. Intra-prostatic implantation of stable cells expressing miR-466 significantly attenuated primary tumor growth. Whereas, bone metastatic dissemination of PC cells was significantly suppressed by intra-cardiac inoculation of stable miR-466 expressing cells compared to control cells in nude mice. We also monitored the overall survival of mice in the metastatic model. Kaplan-Meier survival analysis indicated higher overall survival in the miR-466 group compared to controls.

This is the first study demonstrating that: i) miRNA-466 is downregulated, acts as metastasis suppressor and has diagnostic implications in PC; ii) miR-466 has biological significance in PC as its attenuation induced oncogenic characteristics in normal cells; iii) miR-466 directly targeted RUNX2 and inhibited its downstream genes and iv) stable expression of miR-466 inhibited primary tumor growth and bone metastasis in in vivo models. The use of RNAi is currently being implemented as a gene-specific approach for molecular medicine. By the same principle, it is possible that restoration of silenced miR-466 may lead to down-regulation of target oncogenes thereby contributing to novel therapeutic approaches in the treatment of prostate cancer metastasis.

Citation Format: Shahana Majid, Hanna Nip, Altaf A. Dar, Sharanjot Saini, Varahram Shahryari, Soichiro Yamamura, Yozo Mitsui, Nathan Bucay, Guoren Deng, Rajvir Dahiya, Yuichiro Tanaka. MicroRNA-466 regulates bone metastasis by targeting RUNX2 in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1619.