Abstract 145: MicroRNA-361-3p functions as an oncogenic microRNA in human oral cancer cells

Abstract

Abstract MicroRNAs (miRNAs) are small non-coding double-stranded RNA with sizes of 20-25 nucleotides, and inhibit protein translation by binding the 3'-untranslated region of target mRNA. Each miRNA can regulate multiple mRNAs and each mRNA can be targeted by a number of miRNAs. In cancer, miRNAs can act as not only tumor suppressor genes but also oncogenes (OncomiR). Most recent study has demonstrated OncomiR addiction in mouse pre-B-cell lymphoma. OncomiR addiction may also provide therapeutic opportunities in human cancers such as oncogene addiction. In this study, we have attempted to identify an OncomiR in human oral cancer cells through functional screening and considered whether targeting miRNA can be possible for cancer therapy. First, we performed functional screening for OncomiR in human oral cancer cells by the use of miRCURY LNATM microRNA Knockdown Library (Exiqon). We transfected 918 locked nucleic acid (LNA) antisense oligonucleotides for specific human mature miRNAs into human oral squamous cell carcinoma cells (GFP-SAS) and salivary gland cancer cells (GFP-ACCM). After transfection for 80 hours, each cell growth was evaluated. LNA antisense oligonucleotides against microRNA-361-3p (LNA-miR-361-3p) showed a remarkable growth inhibition in both types of cells as compared with non-targeting LNA oligonucleotides. We also observed the change of cell morphology, diminution of colony size, and a number of non-adherent cells after transfection of LNA-miR-361-3p. Subsequently, we examined the knockdown effect of LNA-miR-361-3p in GFP-SAS cells by quantitative RT-PCR. Compared with control oligonucleotides, the expression of miR-361-3p was significantly reduced by 71%. These effects of LNA-miR-361-3p were not observed by transfection of DNA or RNA antisense oligonucleotides for miR-361-3p. Next, we transfected synthetic human mature miR-361-3p into GFP-SAS cells to investigate the effect of miR-361-3p overexpression. Cell growth resulted in a significant 20% increase compared with non-targeting control miRNA. Furthermore, co-transfection of LNA-miR-361-3p and its decoy oligonucleotides abrogated the growth inhibitory effect by LNA-miR-361-3p in GFP-SAS cells. These results suggest that miR-361-3p functions as an OncomiR in human oral cancer cells and LNA antisense oligonucleotides are useful and efficient for silencing miRNA. Targeting miR-361-3p with LNA antisense oligonucleotides may be a useful therapeutic approach for patients with oral cancer. 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 145. doi:10.1158/1538-7445.AM2011-145