Fas receptor is a member of the tumor necrosis factor/nerve growth factor receptor superfamily. Binding of Fas ligand to Fas receptor leads to activation of the latter and the induction of intracellular signals that result in apoptotic cell death. In the previous studies, our group demonstrated that okadaic acid, protein phosphatase inhibitor, induced apoptosis in several cell lines including human oral squamous carcinoma cells. In the present study, RT-PCR and Western blot analysis were used to examine the expression of mRNA and proteins of Fas receptor and Fas ligand in human oral squamous carcinoma SCC-25 cells treated with okadaic acid. Expression of Fas receptor and Fas ligand mRNAs treated with okadaic acid was stimulated in dose- and time-dependent manners as judged by semiquantitative RT-PCR analysis, with the maximum expression level at 20 nM- and 8 h-treatment. Okadaic acid also stimulated the expression of Fas receptor and Fas ligand proteins in these cells in dose- and time-dependent manners as judged by Western blot analysis. These results indicate that the expression of Fas receptor and Fas ligand is negatively regulated by a protein phosphatase sensitive to okadaic acid. The activity of NF-κB was also stimulated by okadaic acid treatment indicating that expression of Fas receptor and Fas ligand system in SCC-25 cells is related in the activity of NF-κB.
To investigate whether expression of Fas receptor and Fas ligand is involved in okadaic acid-induced apoptosis in SCC-25 cells, effects of okadaic acid on caspase-3 activities were examined. Caspase-3 activities increased after 12 h okadaic acid treatment and maximal activities were observed at 48 h treatment. Okadaic acid induced caspase-3 activities in a dose-dependent manner. Marked nuclear condensation and fragmentation of chromatin were observed in the okadaic acid-treated cells by using Hoechst 33342 staining and electron microscopic observation. Okadaic acid also induced DNA ladder formation in the treated cells with a time-dependent fashion from 12 h to 48 h. The present results indicate that the expression of Fas receptor and Fas ligand is involved in okadaic acid-induced apoptosis in SCC-25 cells. The present results also indicate that Fas receptor and Fas ligand system might regulate apoptosis in SCC-25 cells in an autocrine fashion.

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The General Dentistry Clinic of Kyushu Dental College Hospital is a newly established (July, 1999) dental clinic, designed for training residents to become competent general practitioners who can provide comprehensive, state-of-the-art dental care. Actually, General Dentistry Clinic started its training program with only two residents just last year. Starting in 2006, all the graduate students who pass the National Board of License Examination must undergo training at the teaching Hospitals for one year. The purpose of this study is to evaluate whether there are sufficient new-patients or not, thus providing residents opportunity to advance their knowledge and clinical skills focussing on conservative dentistry, prothetic dentistry and oral surgery.
At this time there are enough cases for training small groups of residents. With the increase in numbers of residents in the near future, efforts should be made to increase the number of new-patients for training, expecially in oral surgery. Further studies should be done to predict the capacity of General Dentistry Clinic for Post-Graduate Clinical Traning Course.

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