RAPID ASSESSMENT OF REPLICATION ERROR PHENOTYPE IN GASTRIC-CANCER

Forty gastric tumors were investigated for microsatellite instability at the D2S119 and L-myc loci. These tumors and 143 other gastrointesti nal cancers were previously analyzed for instability at several differ ent microsatellites. By evaluating previous and present results, repea ted sequences were selected that frequently underwent replication erro rs (RERs). To coamplify these sequences, the following multiplex polym erase chain reactions (PCRs) were performed: 1) D2S119/L-myc/D18S59; 2 ) D2S119/L-myc/D3S1076; and 3) D2S177/L-myc/BAT-RII. Therefore, the 40 gastric tumors in the present survey were rescreened using multiplex PCRs. Each multiplex allowed detection of nearly all RER+ tumors (80% for multiplex 3 and 87% for multiplexes 1 and 2) that had been previou sly identified by amplifying 9 different loci with independent reactio ns. Moreover, for multiplexes 1 and 2, the size differences between no rmal and RER alleles were sufficient to be detected by electrophoresis on conventional polyacrylamide gels after DNA staining with ethidium bromide. This approach allows a rapid and easy assessment of RER pheno type in gastric tumors.