Abstract 140: Tumor suppressor role of microRNA-1 in prostate cancer

Abstract

Abstract MicroRNAs (miRNA) are small non-coding RNAs that reduce the translation of target mRNAs via 3’ untranslated region (UTR) binding sites. MicroRNA-1 has been previously shown by genome-wide studies in our lab to be under-expressed in prostate cancer (PCa) tissues and lost in most of the NCI-60 cell lines. We hypothesize that miRNA-1 plays a role in the progression of PCa through tumor suppressor mechanisms. To explore this we used an integrated system biology approach by re-expressing miRNA-1 and studying its targetome by mRNA microarray analysis, miRNA target prediction, pathway analysis, and connectivity mapping. From these analyses we found that miRNA-1 down-regulated transcripts were significantly enriched for predicted targets and genes involved in cell cycle progression, mitosis, and DNA replication/repair. Following this we found evidence that miRNA-1 could increase the number of cells in S-phase while reducing mitotic cell numbers and the protein levels of genes required for S-phase progression including CHK1 and MCM7. Connectivity mapping of miRNA-1 expression profiles revealed that the effects of this miRNA overlap with histone deacetylase inhibitors like Vorinostat and Trichostain (TSA). Supporting this we found that miRNA-1 could be re-expressed when PCa cells were treated with epigenetic drugs such as 5-azadeoxycytidine and TSA. This could implicate a downstream role of miRNA-1 in these epigenetic mechanisms. Moreover, miRNA-1 expression increased radiation mediated levels and resolution of the DNA damage biomarker gamma-H2A.X, while reducing the clonogenic survival of PCa cells to radiation. This indicates that the loss of miRNA-1 could have clinical importance, by leading to an increase in the survivability of PCa cells to radiation therapy. Further, we found that several possible targets of miRNA-1 are actin binding genes that could play roles in both mitosis and migration. Using 3’UTR reporter assays we found that miRNA-1 directly targets several of these genes including, LASP-1, XPO6, NOTCH-3, FN1, MMD, and PTMA. Subsequently, epi-fluorescence microscopy revealed that miRNA-1 was capable of increasing F-actin levels and altering its organization in PCa cells. In conclusion, our findings indicate that miRNA-1 functions as a tumor suppressor in PCa by influencing cell cycle, the DNA damage response, and regulating actin related genes involved in mitosis and cell motility. These studies implicate a possible utility of miRNA-1 expression patterns in the therapeutic outcome of PCa patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 140. doi:10.1158/1538-7445.AM2011-140