Gene expression profiling of SAS cell line transfected with siRNA targeting CYLD

Oral squamous cell carcinoma (OSCC) has a very poor prognosis due to its highly invasive nature, and 5-year survival rate has not changed apparently for the past 30 years. Although cylindromatosis (CYLD) is thought as a potent tumor suppressor, its biological and clinical significances in OSCC are largely unknown. The aim of this study was to clarify roles of CYLD in OSCC progression. Our immunohistochemical analyses revealed that CYLD expression was significantly reduced at invasive lesions in OSCC tissues whereas it was conserved in normal epithelium and carcinoma in situ. Accordingly, downregulation of CYLD by siRNA led to an acquisition of mesenchymal state and increased migratory and invasive activities in OSCC cells and HaCaT keratinocytes. Interestingly, CYLD knockdown promoted TGF-beta signaling by inducing TGF-beta receptor I (ALK5) stabilization in a cell autonomous fashion. In addition, the response to exogenous TGF-beta stimulation was enhanced by CYLD downregulation. The invasive phenotype induced by CYLD knockdown were completely blocked by an ALK5 inhibitor. Furthermore, lower CYLD expression was significantly associated with deep invasion, poor overall survival, and increased Smad3 phosphorylation which is an indicator of TGF-beta signaling activation in invasive OSCC. These findings suggest that downregulation of CYLD promotes invasion with mesenchymal transition via ALK5 stabilization in OSCC cells.

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