Fas receptor (CD95) & Fas ligand (CD178) expression in patients with tobacco-related intraoral squamous cell carcinoma

BACKGROUND & OBJECTIVES: Fas receptor and Fas Ligand (FasL) system has been implicated in the resistance to apoptosis, insensitivity to chemotherapy and in providing immune privileged status to most of the tumours. However, no reports are available on Fas and FasL expression in patients with tobacco-related oral carcinoma. Therefore, the present study was undertaken to observe Fas and FasL expression and their correlation with clinicopathological features as well as cell cycle parameters. METHODS: Immunohistochemistry for Fas, FasL and DNA flow cytometry for cell cycle parameters was successfully done on 41 paraffin embedded tumour and 10 normal samples. The results were evaluated for possible association of Fas and FasL with clinicopathological features and cell cycle parameters. RESULTS: Weak Fas expression was observed on the cell membrane only in 2 of 41 (5%) oral tumours while FasL immunoreactivity was seen in 26 of 41 (63.4%) tumours. In contrast, all ten normal oral tissues exhibited strong cytoplasmic and membrane Fas receptor immunoreactivity but absence of FasL staining. Older patients, greater tumour size and lymph node positivity were found to be associated with high expression of FasL. Significantly higher (P<0.01) expression of FasL was observed in oral tumours with aggressive DNA pattern like aneuploidy and high S-phase fraction. INTERPRETATION & CONCLUSIONS: Downregulation of Fas receptor and up-regulation of Fas ligand appear to be an important feature of tobacco-related intraoral carcinoma. Association of FasL expression with advanced clinical stage and aggressive DNA pattern suggests that the Fas and FasL system may be used as an important prognostic variable in patients with tobacco-related intraoral squamous cell carcinoma.