Fas expression and Fas monoclonal antibody-induced apoptosis in a human squamous cell carcinoma cell line, SCC-25

Fas antigen is a cell surface protein that mediates apoptosis via signal tr ansduction from the plasma membrane. Using reverse transcriptase-polymerase chain reaction (RT-PCR), messenger RNA for Fas antigen was detected in the human oral squamous cell carcinoma cell line, SCC-25. in serum-free medium , a monoclonal anti-fas antibody (CH-11) induced Fas antigen expression in SCC-25 cells, as determined by immunocytochemistry and Western blotting, us ing an anti-Fas polyclonal antibody (Fas D) as primary antibody. Fas antige n was localized to the cytoplasm and the cell membrane. The molecular weigh t of the protein recognized by Western blot analysis was 35,000, consistent with the value reported for the Fas antigen. The CH-11 antibody did not in duce Fas antigen expression in serum-containing medium. To determine whethe r CH-11 could induce apoptosis in oral squamous cell carcinoma, we examined its effects on the survival of cultured SCC-25 cells. Anti-Fas monoclonal antibody in serum-free medium induced cytotoxicity in SCC-25 cells in a tim e-dependent manner up to 8 h, as determined by phase-contrast microscopy an d WST-1 assay. Marked nuclear condensation and fragmentation of chromatin w ere observed in the CH-11-treated cells using Hoechst 33342 staining. This anti-fas monoclonal antibody also induced DNA ladder formation in SCC-25 ce lls in a time-dependent manner. The present results indicate that the anti- Fas monoclonal antibody (CH-11) may mediate apoptosis by binding to the Fas antigen expressed in SCC-25 cells.