Expression of Fas Antigen and Its Mediation of Apoptosis in Human Gastric Cancer Cell Lines

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Abstract
Fas, a member of the tumor necrosis factor receptor/nerve growth factor receptor family, induces apoptosis by crosslinking with Fas ligand or anti‐Fas antibody in a variety of cultured cells. We examined the expression of Fas antigen and its mediation of apoptosis in six human gastric carcinoma cell lines. Flow cytometric analysis and western blotting revealed relatively high expression of Fas antigen in MKN‐74 (wild‐type p53 gene) and MKN‐45 (wild‐type), followed by MKN‐1 (mutated), MKN‐7 (mutated) and KATO‐III (deleted). MKN‐28 (mutated) showed minimal expression of the antigen. The expression was apparently enhanced by interferon‐γ, except for MKN‐1 and MKN‐28. Anti‐Fas antibody (100 ng/ml) induced nuclear fragmentation characteristic of apoptosis. Apoptosis occurred in a delayed fashion and the apoptotic index at 72 h was approximately 60% in MKN‐74, 35% in MKN‐45, and 20% in MKN‐1 and KATO‐III. A DNA ladder was noted in MKN‐74 at 72 h. Expression levels of P53 and P21Wafl did not change for up to 48 h in MKN‐74. The biological effects did not correlate with endogenous Bcl‐2 expression. These results indicated that a) Fas antigen is variably expressed in human cultured gastric carcinoma cells, b) the protein transduces an apoptotic signal which leads to delayed cell death, and c) susceptibility to the antibody correlates well with the expression level of Fas antigen.

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