Localization of Fas antigen in oral squamous cell carcinoma

Fas antigen is a cell-surface protein that transduces an apoptotic signal from the cell surface into the cytoplasm. The localization of Fas antigen in human oral squamous cell carcinoma (SCC) was examined by immunohistochemistry using a monospecific polyclonal antibody with a high titre. This antibody, designated as Fas D, was raised against a synthetic polypeptide segment corresponding to a specific extracellular domain of human Fas antigen (aa 104–114). Thirty-eight specimens of oral SCCs were stained with Fas D antibody and 26 (68%) reacted intensely. The specimens were graded as ‘well’, ‘moderately’, or ‘poorly differentiated’, according to the histopathological criteria. Out of 24 cases of the well differentiated tumours examined, 22 had reacted to Fas staining. The tumour cells formed nests that encompassed keratin pearls; staining was confined to cytoplasmic granules of peripheral cells. Among the moderately differentiated tumours, 4 out of 11 cases had reacted to Fas staining. No Fas-positive cells were observed in the poorly differentiated tumours, but only three specimens were examined. The expression of Fas antigen seems to be related to the degree of tumour differentiation.