Abstract 3107: MicroRNA-1289 is a novel tumor suppressive microRNA in human oral squamous cell carcinoma

Abstract

Abstract MicroRNAs (miRNAs) are small non-coding double-stranded RNA with sizes of approximately 22 nucleotides, and those inhibit protein translation by binding the 3′-untranslated region of target mRNAs. Each miRNA generally can regulate multiple mRNAs and each mRNA can be inhibited by a number of miRNAs. MiRNAs can behave as not only oncogenes but also tumor suppressive (TS) genes in human malignancies. In fact, a number of TS miRNAs (TS-miRs) were found in human many types of cancer, such as let-7, miR-1, miR-34, miR-145, miR-200, miR-206 and more. In this study, we have attempted to identify a novel TS-miR in human oral squamous cell carcinoma (OSCC) using function-based screening. First, we transfected human OSCC cells (GFP-SAS) with approximately 1,000 synthetic mimicking human mature miRNAs at the concentration of 20 nM complexed with Lipofectamine RNAiMAX. After transfection for 72 hours, the growth of these cells was evaluated by WST-8 assay. As a result, miR-1289 had the most potent growth inhibitory effect against GFP-SAS cells. The growth rate of these cells transfected with miR-1289 was reduced by 86.4%. MiR-1289 also remarkably inhibited the growth of other human OSCC cells (Ca9-22, HSC2, HSC3 and primary cultured cells). Subsequently, we assessed the growth inhibitory effect of miR-1289 in vivo using a mouse model. GFP-SAS cells (2 × 106) complexed with matrigel in 100 μl aliquots were injected subcutaneously in nude mice. After tumor formation, we administered 100 ng of miRNA with 0.5% atelocollagen complexes (100 μl) around tumor every 3 days for a total of 5 injections. MiR-1289/atelocollagen complex administration group significantly reduced the size of subcutaneously xenografted GFP-SAS tumors compared with the control group. Next, we investigated the expression of miR-1289 in OSCC tissues by real-time quantitative RT-PCR. The expression levels of miR-1289 were significant decreased in OSCC tissues compared to adjacent normal oral mucosa tissues. Finally, target genes of miR-1289 were explored by microarray and Ingenuity Pathway Analysis (IPA). Microarray analysis revealed that the expression levels of 51 genes were commonly down-regulated in OSCC cells (GFP-SAS, Ca9-22 and HSC2) by transfection with miR-1289. Among these genes, 15 genes were identified as target genes of miR-1289 by IPA. These results suggest that miR-1289 functions as a novel TS-miR in OSCC, and may be a useful therapeutic tool for the patients with OSCC. Citation Format: Kazuki Iwamoto, Koh-ichi Nakashiro, Hiroshi Tnaka, Norihiko Tokuzen, Hiroyuki Hamakawa. MicroRNA-1289 is a novel tumor suppressive microRNA in human oral squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3107. doi:10.1158/1538-7445.AM2015-3107