Fas antigen and Fas ligand with signaling pathway in Squamous carcinoma cells

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To determine the relationship between the expression of Fas antigen and apoptosis in oral epithelium, we investigated the expression of Fas antigen in oral mucosa by immunohistochemical and immunoblotting methods. Fas antigen distributed in stratum spinosum and basal part of the stratum coreneum in normal human gingiva. Expression of Fas antigen was related to the degree of the tumor differentiation. Using RT-PCR method, mRNA for Fas antigen was detected in the human oral squamous cell carcinoma cell line SCC-25. In serum-free medium, a monoclonal anti-Fas antibody stimulated the expression of Fas antigen in SCC-25 cells. Fas antigen was localized in the cytoplasm and at the cell membrane.Protein phosphatase inhibitors, okadaic acid and calyculin A induced apoptosis in SCC-25 cells and another human squamous carcinoma cells lines SCC KN and SCC TF cells. Okadaic acid also simulated the expression of mRNA and protein of Fas antigen and Fas ligand in SCC-25 cells in time- and dose-dependent manners. Using immunoblotting and electrophoretic mobility shift assays, okadaic acid activated NF-κB, transcriptional factor, in SCC-25 cells. Our results indicate that okadaic acid mediate apoptosis by inducing of NF-κB activity that may stimulate the transcriptional activity of Fas ligand in SCC-25 cells.