Aberration of a TGF-β Signaling Molecule, Smad4, in Oral Squamous Cell Carcinoma

Abstract:Although carcinogenesis of oral squamous cell carcinoma (OSCC) have been studied by many investigators in the past decade, the data about its molecular mechanism remain fragmented. The objective of the present study was to investigate the expression of a signaling molecule of TGF-β pathway, Smad4 in OSCC in comparison with normal oral mucosa. The expression of Smad4 in tissue samples of OSCC and oral normal mucosa was studied by means of immunohistochemical technique. We also compared the expression of Smad4 protein in SCC cell lines and normal oral keratinocytes by Western blot analysis. The rate of Smad4 expression in OSCC tissue samples was only 60% while 82% in tissue samples of normal oral mucosa. A reduction of Smad4 expression was clearly shown in all SCC cell lines as compared with normal oral keratinocytes. These findings indicate that the aberration of TGF-β pathway as evidenced by a reduction or deletion of Smad4 expression may promote carcinogenesis of OSCC. 「Introduction」Oral squamous cell carcinoma (OSCC) is a serious problem of oral health worldwide including the northern Thailand population(1).