Abstract 16: Downregulation of CYLD leads to acquisition of mesenchymal state and increased migration via ligand-independent TGFβR1 activation in human oral squamous cell carcinoma cells

Abstract

Abstract The 5-year survival of patients with oral squamous cell carcinoma (OSCC) has not changed apparently for the past 30 years. Although cylindromatosis (CYLD) is thought as a potent tumor suppressor, its biological significances in malignancies are largely unknown. The aim of this study was to clarify the role of CYLD in OSCC progression. We investigated expression of CYLD in OSCC including intraepithelial neoplasia (IEN; n = 48) and invasive carcinomas (n = 133) tissues and normal oral mucosal tissues (n = 35) by immunohistochemistry. In addition, effects of CYLD knockdown by siRNA transfection on OSCC progression using 5 OSCC cell lines (SAS, Tu4, HSC3, Ca9-22, and SCC-NA) and HaCaT keratinocytes. Our immunohistochemical analyses revealed that CYLD expression was significantly reduced at invasive lesions in OSCC tissues whereas it was conserved in normal epithelium and IEN. In addition, lower CYLD expression was associated with the correlation with the increased tumor size, advanced clinical stage, and poor overall survival in invasive OSCC. Accordingly, CYLD knockdown led to acquisition of mesenchymal state and increased migratory activity in all the OSCC cell lines as well as HaCaT keratinocytes. Notably, such EMT-like changes were completely blocked by a TGFβR1 inhibitor in all the OSCC cell lines, but not in HaCaT keratinocytes. Furthermore, treatment with excess amount of anti-TGFβ antibody (1D11) did not inhibit the EMT-like changes induced by CYLD repression. These findings suggest that downregulation of CYLD promotes invasion through EMT-like changes via ligand-independent TGFβR1 activation in OSCC cells in mechanisms distinct from normal epithelium. Further studies for these mechanisms probably provide new insights into the biology including “TGFβ switch” and development of a novel therapy in OSCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 16. doi:1538-7445.AM2012-16