| Oral carcinogenesis is closely related to signal transduction pathways regulating growth and differentiation. Protein kinase c (PKC) family transduce the myriad of signals mediated by phospholipids and play important roles in a variety of cellular functions including cell growth, proliferation, differentiation, apoptosis and gene expression. Recent studies show that PKCs also participate in the processes of tumor cell proliferation, invasion and metastasis, apoptosis and multidrug resistance. But the molecular mechanism of PKCs in mediating oral carcinogenesis remains unclear. The purpose of this study was to examine protein expression and subcellular distribution PKC and PKC isoform (PKC-a) in oral squamous cell carcinoma and correlations with proliferation associated gene (PCNA, cyclinD1 and CDK4) and apoptosis associated gene (bcl-2, bax, survivin and caspase-3) by using methods of immunohistochemistry, western blotting and confocal laser scanning microscopy. In further study, effects of PKC-a activation and inhibition on human tongue squamous cell carcinoma (TSCCa) cell line were investigated to elucidate the molecular mechanisms of PKC-a in oral carcinogenesis. Present study includes following four parts:Part I Role of PKC expression and subcellular distribution in oral carcinogenesisPurpose: To investigate the PKC expression and subcellular distribution in oral carcinogenesis and the correlation to the clinicopathologic covariates.Methods: Immunohistochemistry and confocal laser scanning microscopy were used to detect PKC expression in tissue from normal oral mucosa (NOM; w=20), oral pre-cancer lesions (OPL; w=23) and oral squamous cell carcinoma (OSCC; ra=40). The PKC expression was correlated to the differentiation stage and nodal involvement. Western blotwas used to confirm the specificity of antibody and to follow changes in expression of PKC in membranous and plasmic tissue homogenates of NOM, OPL and OSCC.Results: The PKC immunoreactivity increased significantly from 5.00%(1/20) in NOM and 34.78%(8/23) in OPL and 77.50% (31/40) in OSCC. In addition, The PKC immunoreactivity increased significantly with the differentiation and lymph node metastasis (LNM) of OSCC. Confocal laser scanning microscopy showed that protein expression of PKC increased significantly in cytoplasm between each of the OPL and OSCC groups. Accompanying with the oral carcinogenesis, the activity of PKC increased in the plasmic and membranous homogenates, especially in cytomembrane.Conclusions: Increased PKC protein expression and translocation to cytomembrane was associated with oral carcinogenesis.Part II Increased PKC-a is associated with cyclinDl and CDK4 protein in oral carcinogenisisPurpose: To investigate the PKC-a expression in oral carcinogenesis and the correlation to the cyclinD1 and CDK4 peotein in cell proliferation.Methods: Immunohistochemistry was used to detect PKC-a, PCNA, cyclinD1 and CDK4 expression in tissue from normal oral mucosa (NOM; n=20), oral pre-cancer lesions (OPL; n=23) and oral squamous cell carcinoma (OSCC; n=40). The relationship between PKC-a and PCNA, cyclinD1 and CDK4 was analyzed.Results: Immunoreactivity of PKC-a increased significantly from 5.00% in NOM and 26.09% in OPL and 55.0% in OSCC. In addition, The PKC-a immunoreactivity increased significantly with the differentiation and lymph node metastasis (LNM) of OSCC. The PCNA immunoreactivity increased significantly from 20.00% in NOM and 43.48% in OPL and 82.50% in OSCC. The cyclinDl immunoreactivity increased significantly from 0.00% in NOM and 21.74% in OPL and 75.00% in OSCC. The CDK4 immunoreactivity increased significantly from 10.00% in NOM and 26.09% in OPL and 67.50% in OSCC. PKC-a was correlated positively with PCNA, cyclinDl and CDK4.Conclusions: Increased PKC-a was associated with cyclinDl and CDK4 protein in oral carcinogenesis.Part III Correlaltion between PKC-a and apoptosis associated gene bcl-2, bax, survivin and caspase-3 in oral carcinogenesisPurpose: To investigate the PKC-a expression in... |
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