Somatic mutations in the death domain of the Fas (Apo-I/CD95) gene in gastric cancer

It is now believed that genes regulating apoptosis are also important varia bles in cancer development. Fas, a transmembrane protein of the tumour necr osis factor receptor family, is a key molecule for cell death signalling. T he mutation of the primary structure of the Fas gene might also be one of t he possible mechanisms that disrupt Fas-mediated apoptosis in tumour cells. The purpose of this study was to determine whether somatic mutation of the Fas gene could be involved in the tumourigenesis of gastric cancer. Polyme rase chain reaction (PCR)-based loss of heterozygosity (LOH) analysis with two intragenic polymorphic markers, and mutation analysis for the entire co ding regions of the Fas gene were performed in 43 cases of gastric cancer, using PCR-single-strand conformational polymorphism sequencing. Five (11.6% ) missense mutations were detected, only in the death domain of the Fas gen e. Although these mutations were observed only in intestinal-type gastric c ancers, there was no statistically significant difference in the frequency of Fas mutation between intestinal- and diffuse-type gastric cancer (p=0.06 8), Nine LOH out of 22 informative cases were also detected with one or bot h markers (41%), Three of them demonstrated a somatic mutation in the remai ning allele, indicating the inactivation of both alleles, These results sug gest that genetic alterations of the Fas gene may not only be limited to ga stric canter cell protection through Fas resistance, but may also play an i mportant role in tumour promotion and/or progression in a subset of gastric cancer. Copyright (C) 2000 John Wiley & Sons, Ltd.