Abstract 539: Downregulation of hnRNP A1 by miRNAs as a new mechanism of survival in ovarian cancer

Abstract

Abstract Background. Posttranscriptional regulation is a critical control point for the expression of genes that promote or retard tumor growth. The mRNA-binding protein hnRNP A1 is required for the processing of miR-18a, an inhibitor of k-ras expression. In this study we hypothesized that downmodulation of hnRNP A1 by miR-25 and miR-15a controls the expression of miR-18a and k-ras by modulating nuclear and cytoplasmic miRNA processing at the posttranscriptional level. Methods. In this study, we determined the expression of hnRNP A1 at mRNA and protein levels in three parental ovarian cancer cells lines (Skov3ip1, HeyA8, and A2780) and their chemotherapy-resistant derivatives (Skov3-TR, HeyA8 MDR, and A2780 cp20). We also predicted in silico which miRNAS can target hnRNP A1 and confirmed the miRNA expression by real-time PCR. Moreover, we inhibited miR-25 and mir-15a to determine their tumorigenic potential in vitro. We also correlated the expression of miR-25 and miR-15a and/or miR-18a and k-ras expression in the TCGA data. Results. Downregulation of hnRNP A1 at the RNA and protein levels was observed in the taxane-resistant cell lines but not in the cisplatin-resistant cell line. Furthermore, we predicted in silico that miR-25and miR-15a can target hnRNP A1 and confirmed the overexpression of these microRNAs in SKOV3-TR (5- and 3-fold, respectively) and HeyA8 MDR (3-fold) by real-time PCR. We also analyzed overall survival, trying to find a correlation between k-ras and miR-15a (high 23.77, low 33.97 months), k-ras and miR-25 (high 16.95, low 35.21 months), and the combination of k-ras, miR-25, and miR18a (k-ras high, miR25 high, mir18a low, 20.73 months; k-ras low, miR25 low, mir18a high, 31.49 months). Comparison of these data with a validation set yielded similar results. Conclusion. These results underscore the importance of a previously uncharacterized circuit of posttranscriptional regulation between miR-25 or -15a and RNA-binding protein hnRNP A1 that regulates miR-18a and k-ras expression. This circuit represents a unique opportunity for novel therapeutics approaches. Citation Format: Cristian Rodriguez-Aguayo, Paloma Monroig, Maria I. Almeida, Cristina Ivan, Vianey Gonzalez-Villasana, Maitri Y. Shah, Anil K. Sood, George Calin, Gabriel Lopez-Berestein. Downregulation of hnRNP A1 by miRNAs as a new mechanism of survival in ovarian cancer. [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 539. doi:10.1158/1538-7445.AM2014-539