Suppression of Fas receptor and negative correlation of Fas ligand with differentiation and apoptosis in oral squamous cell carcinoma

Apoptosis and the expression of Fas receptor (Fas and Fas ligand (FasL) wer e studied in 8 samples of normal oral mucosa (OM) and in 19 oral squamous c ell carcinomas (OSCC) by immunohistochemistry and the TUNEL method. Fas was detected in less than 2% of cells in OSCC compared with 84.3+/-9.0% of cel ls in the basal layer in OM. Fast was found to be highly expressed in poorl y differentiated lesions (90.9+/-3.6%). and in cells of both the basal (88. 3+/-4.3%) and central (85.3+/-5.7%) parts of moderately differentiated lesi ons, whereas in well-differentiated (WD) lesions expression was considerabl y lower in both basal (42.7+/-4.1%) and central (11.5+/-2.4%) parts. In nor mal OM FasL was primarily detected in cells of the basal layer, but in a hi gh proportion of cells (84.9+/-4.3%). Apoptotic cell death was greater in O SCC (1.6+/-0.6%) than in OM (0.6+/-0.2%, P<0.05) and was most pronounced in the central part of WD OSCC (2.3+/-0.5%). Our results show that Fas is exp ressed in low quantities in OSCC and that Fast expression correlates negati vely with degree of differentiation and apoptosis in OSCC.