Loss of heterozygosity in gastric neuroendocrine tumor.

The MEN1 gene locus is known to be partly responsible for the tumorigenesis of sporadic gastric neuroendocrine tumors, but the genetic events that drive the neoplastic process of this tumor remain largely unknown. In order to screen the tumor suppressor genes associated with the tumorigenesis of gastric neuroendocrine tumors, 15 neuroendocrine carcinomas and three carcinoid tumors in the stomach were analyzed for loss of heterozygosity (LOH) using 22 microsatellite markers. In our study, the gastric neuroendocrine tumors showed a high rate of LOH in chromosomes 8p (82%), 15q (58%), 17p (57%), llp (50%), 12p (50%) and 13q (50%). The mean fractional allelic loss (FAL) was higher in the neuroendocrine carcinoma components than in the adenocarcinoma components (0.42 versus 0.33, respectively). In four cases, the adenocarcinoma components showed discordant LOH patterns from those of the neuroendocrine counterparts in half of the informative chromosomes analyzed. Comparably, the gastric neuroendocrine carcinomas exhibited a higher LOH frequency on 8p and a lower LOH on 7q than did the gastric adenocarcinomas. It is suggested that chromosome 8p is the possible location of the tumor suppressor genes associated with the tumorigenesis of gastric neuroendocrine tumors.