Alterations of the p16/MTS1-tumor suppressor gene in gastric cancer.

Deletions, mutations and the functional inactivation of tumor suppressor gene p16 are involved in the genesis of different neoplasias. Little is known about the role of p16 gene alterations in the genesis of gastric carcinomas. This study aimed to detect genetic alterations of the p16 gene in gastric carcinomas. We analyzed p16 gene mutations and the frequency of loss of heterozygosity (LOH) at the p16 locus in 43 gastric carcinomas. PCR-SSCP analysis of exons 1 and 2 revealed only one gene mutation in a carcinoma of the diffuse type. Besides carcinomas of the diffuse, intestinal and the mixed type, we also investigated a small-cell primary gastric carcinoma, which was the only one to show a deletion in the p16 gene. LOH analysis was performed using two polymorphic markers located near the p16 gene (D9S171, D9S162) and a sequence-tagged-site marker (c5.1). Allelic loss was noted in two carcinomas of the diffuse type and in one carcinoma of the intestinal type. Allelic instabilities were found in one tumor of the intestinal type and diffuse type each. Although only five of 43 (11.6%) gastric carcinomas had p16 alterations, tumors of the diffuse type tend to show a higher number of genetic alterations near the p16 locus.