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) were studied in 8 samples of normal oral mucosa (OM) and in 19 oral squamous cell 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 cells in the basal layer in OM. FasL was found to be highly expressed in poorly 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 lesions, whereas in well-differentiated (WD) lesions expression was considerably lower in both basal (42.7+/-4.1%) and central (11.5+/-2.4%) parts. In normal OM FasL was primarily detected in cells of the basal layer, but in a high proportion of cells (84.9+/-4.3%). Apoptotic cell death was greater in OSCC (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 expressed in low quantities in OSCC and that FasL expression correlates negatively with degree of differentiation and apoptosis in OSCC.