MicroRNAs in miR-17-92a cluster are transcribed from a polycistronic transcription unit C13orf25 that generates six mature miRNAs, miR-17, miR-18a, miR-19a, miR- 19b, miR-20a. These miRNAs are reported to be overexpressed in colon and lung cancers, however, we noted a loss of expression of all members of this miR cluster in prostate cancer tissues compared to uninvolved tissues and in aggressive prostate cancer cells. In this study, we show that replenishment of miR-17-92a cluster as a whole showed antiproliferative effects, reduced activation of AKT and MAP kinases, delayed tumorigenicity and reduced tumor growth. Analysis of the expression of mRNA targets showed reduced expression of cell cycle regulatory proteins cyclin D1 and SSH1; and LIMK1 and FGD4 of RhoGTPase signaling pathway through direct targeting. miR-17-92 cluster expression also inhibited EMT via reduced cell migration and expression of mesenchymal markers while elevating expression and surface localization of the epithelial marker E-Cadherin. miR-17-92a miRNAs improved sensitivity of androgen dependent LNCaP 104-S prostate cancer cells to anti-androgen drug Casodex, AKT inhibitor MK-2206 2HCl, and docetaxel. The androgen refractory PC-3 cells also showed increased sensitivity to docetaxel, MK-2206 2HCl and Aurora kinase inhibitor VX680 upon ectopic expression of miR-17-92a cluster miRNAs. RNA seq analysis of prostate cancer cells expressing miR-17-92a cluster revealed altered expression of a number of oncogenic and tumor suppressor mRNAs, and noncoding RNAs, which may have implications in the altered phenotype of these cells. Our data demonstrate a tumor suppressor effect of miR-17-92a cluster miRNAs in prostate cancer cells and restoration of expression of these miRNAs has a therapeutic benefit for both androgen-dependent and -independent prostate cancer cells.

Note: This abstract was not presented at the meeting.

Citation Format: Ratna Chakrabarti, Richard Ottman, Md Faqrul Hasan. Tumor suppressor effects of miR-17-92a cluster miRNAs on prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-325. doi:10.1158/1538-7445.AM2017-LB-325