GENETIC INSTABILITY IN PANCREATIC-CANCER AND POORLY DIFFERENTIATED TYPE OF GASTRIC-CANCER

To examine genetic instability during carcinogenesis, we screened 171 carcinomas of the breast, liver, proximal colon, stomach, pancreas, ut erine cervix, and ovary for replication error at four microsatellite m arker loci on chromosomes 2, 3, and 17. A significantly high incidence of genetic instability was observed in pancreatic (6 of 9 tumors) and gastric cancers (22 of 57 cases). In other types of carcinoma, the in cidence of replication error-positive cases was relatively low (3-16%) . Among gastric carcinomas, significantly more replication error-posit ive cases were observed in the poorly differentiated types (16 of 25 c ases) than in well differentiated types (3 of 18) (P = 0.0023 by Fishe r's exact test). Our results suggested that genetic instability is lik ely to play an important role in development of pancreatic and gastric cancers, particularly poorly differentiated adenocarcinomas.