Abstract 144: microRNA-107 regulates PKCepsilon and functions as a tumor suppressor miR in head and neck squamous cell carcinoma

Abstract

Abstract Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer worldwide with about 600,000 new cases diagnosed in the last year. The 5-year survival rate of HNSCC has remained stagnant despite advances in the clinical management of this disease. Understanding the molecular pathways that lead to aggressive HNSCC is crucial to identify new “druggable” targets for anti-cancer drug development. Protein kinase Cepsilon (PKCε) is elevated in HNSCC and regulates cell invasion and motility thorough activation of Rho GTPases. Our laboratory and others provide evidence that PKCε is a transforming oncogene that phosphorylates and modulates a cascade of signal transduction pathways, including Akt, EGFR, Rho GTPases, and Stat3. Thus, targeting PKCε may be an attractive therapeutic approach to dampen multiple hyper-active signaling pathways in concert. At this time, the molecular mechanism of PKCε dysregulation in HNSCC remains to be elucidated. In silico analysis with TargetScan, MiRBase, and miRanda identified numerous putative microRNA (miR) binding sites in the 3’-UTR region of PKCε. We screened a panel of miRs using qPCR and miR-107 was identified to have an inverse association with PKCε in HNSCC cell lines with high endogenous PKCε. Ectopic expression of miR-107 in several HNSCC cell lines significantly reduced PKCε mRNA expression and protein levels. The expression of a luciferase reporter construct containing the 3’-UTR of PKCε was down-regulated by miR-107 and deletion/mutation of the three cognate miR-107 binding sites completely abolished the regulation by miR-107. These observations confirm PKCε as a validated target of miR-107. Ectopic expression of miR-107 in HNSCC cell lines significantly inhibited cell proliferation, DNA replication, clonogenic survival, invasion and migration. Tumor take and tumor growth of HNSCC cells was suppressed by miR-107 in a pre-clinical nude mouse model of HNSCC. Lastly, miR-107 was significantly reduced and showed an inverse expression relationship with PKCε in human primary HNSCC tumors. These results indicate that miR-107 regulates PKCε levels to control the tumorigenicity of HNSCC cells. Taken together, our data substantiate the potential application of miR-107 as a novel anti-cancer therapeutic for HNSCC. 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 144. doi:10.1158/1538-7445.AM2011-144