Micrornas Regulated By Ese3/Ehf Control Important Mediators Of Epithelial Cell Differentiation And Stemness In Prostate Tumors

Deregulated expression of ETS transcription factors has emerged as an important event in prostate cancer pathogenesis. We found that loss of the ETS factor ESE3/EHF induced a broad dedifferentiation program associated with epithelial-to-mesenchymal transition (EMT) and induction of metastatic and cancer stem-like cell properties. To understand the mechanism by which ESE3/EHF controls differentiation of prostate epithelial cells, we examined microRNA (miRNA) expression in a cohort of primary prostate tumors and prostate epithelial normal and cancer cells using miRNA gene arrays. A distinct set of miRNAs was specifically deregulated in cancer cells and tumors with low ESE3/EHF expression. Bioinformatic analysis indicated that the deregulated miRNAs controlled many genes involved in EMT and cell stemness. Interestingly, we found that miR-424 was at the top list of the miRNAs up-regulated in ESE3 low expressing tumors and cell lines. This finding was confirmed by qRT-PCR both in cells and human tumors. Functional assays showed that ESE3/EHF controlled directly miR-424 by binding to the pre-miRNA promoter and repressing its transcription. Inhibition of miR-424 using an antimiR reduced anchorage-independent growth and cell migration in cancer cells with low ESE3 expression and high miR-424 level. On the contrary, stable expression of pre-miR-424 in cells with low endogenous miR-424 level increased anchorage-independent growth and cell migration. Furthermore, modulation of miR-424 expression affected in vitro prostatosphere formation, a phenotype associated with cancer stem-like cell properties. Consistently, inhibition of miR-424 in DU145 prostate cancer cells reduced growth of tumor xenografts in immunodeficient mice. Integrating bioinformatic analyses of the predicted targets and gene profiling of cells with miR-424 overexpression we found that miRNA-424 controlled several factors involved in protein degradation. Collectively, these results show for the first time that ESE3/EHF controls a distinct network of miRNAs with both oncogenic and tumor suppressor functions. Loss of ESE3/EHF resulted specifically in increased expression of miR-424, which has oncogenic properties in prostate epithelial cells. This represents a novel mechanism by which deregulation of ESE3/EHF impact on prostate tumorigenesis. Thus, targeting miR-424 could be a novel therapeutic strategy for prostate cancer. Citation Format: Cecilia Dallavalle, Domenico Albino, Gianluca Civenni, Paola Ostano, Davide Genini, Ramon Garcia-Escudero, Laura Curti, Sandra Pinton, Manuela Sarti, Giovanna Chiorino, Carlo V. Catapano, Giuseppina M. R. Carbone. MicroRNAs regulated by ESE3/EHF control important mediators of epithelial cell differentiation and stemness in prostate tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1451. doi:10.1158/1538-7445.AM2014-1451