Detection of microsatellite instability but not truncating APC mutations in gastric adenocarcinomas in Brazilian patients

A crucial role for the adenomatous polyposis colonic (APC) gene in colorect al carcinogenesis has been conclusively established, but, the role of APC i n gastric tumors remains controversial. APC mutations have been detected at a relatively high frequency in gastric tumors of Japanese patients, yet su ch mutations have been reported to be extremely rare in British patients an d patients from north-central-Italy We here report the analysis of 40 prima ry sporadic gastric adenocarcinomas and 35 primary sporadic colon adenocarc inomas (from patients resident in Sao Paulo, Brazil), for mutations in the APC gene between codons 686 and 1693 using the protein truncation test. Alt hough 19 truncating mutations were detected in 35 colon adenocarcinomas (54 .2%) none were found in any of the gastric adenocarcinomas. As an internal control the tumor samples were also evaluated for microsatellite alteration s, which are also common features of both tumor types. Microsatellite insta bility was present in 1 colon and 7 gastric tumor samples. This suggests th at in relation to APC mutations gastric adenocarcinomas from Brazilian pati ents are similar to those that occur in Europe, and support a fundamental d ifference both between gastric carcinomas that occur in different geographi cal regions and between the molecular etiology of gastric and colorectal ad enocarcinomas occurring in Sao Paulo, Brazil.