Abstract 2099: Induction of tumor suppressor genes IL24 and IL32 by microRNA-205 in prostate cancer

Abstract

Abstract Introduction and Objective: MicroRNAs are small noncoding RNAs that regulate the expression of approximately 30% of all human genes, either inhibiting target mRNA translation or inducing its degradation. These genes are abnormally expressed in human malignancies, making their biological importance increasingly apparent. Given the functional complexity of miRNA mediated gene regulation, it is unlikely that miRNAs are limited to gene silencing. The main objective of this study was to investigate the involvement of miRNA-205 in prostate carcinogenesis and whether miR-205 functions as a tumor suppressor by transcriptionally up-regulating tumor suppressor genes IL24 and IL32. Methods: The methods employed in this study include quantitative-real time PCR; western blot; in-situ hybridization; fluorescence-activated cell sorting assays for cell cycle distribution and apoptosis; assays for cell viabiltity, clonability, migration and invasiveness of prostate cancer cells. Luciferase reporter and mutational assays; nuclear run-on, in-vitro transcription and chromatin immunoprecipitation assays were also performed. Results: Our results indicated that miR-205 expression levels are either silenced or significantly lower in prostate cancer cell lines and prostate tumors when compared to non-malignant prostate cell lines or benign prostate hyperplasia tissues respectively. By scanning gene promoters for sequences complementary to miR-205, we identified putative miR-205 target sites in the promoters of IL24 and IL32 tumor suppressor genes. Over-expression of miR-205 in prostate cancer cells (PC-3) induced the expression of both genes by targeting specific sites in their promoters. Transfection of miR-205 impaired cancer cell growth, clonability, migration, invasiveness and induced apoptosis and cell cycle arrest by interfering with the expression of genes involved in these pathways. MicroRNA-205 induced in-vitro transcription and caused enrichment of histone markers indicative of transcriptionally active promoters in IL24 and IL32 genes. Luciferase reporter and mutational assays indicated that IL24 and IL32 are the direct targets of miR-205. Conclusion: For the first time we have shown that microRNA-205 specifically activates tumor suppressor genes IL24 and IL32 by targeting complimentary binding sites in their promoters, corroborating a new function for miRNAs in regulating gene transcription. Such a function of microRNAs may contribute to the novel therapeutic approach in the treatment of prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2099.