Loss of heterozygosity analysis of a candidate gastric carcinoma tumor suppressor locus at 7q31.

Gastric carcinoma is one of the most common malignancies in Asia. Although the allelic deletion of 7q has been reportedly associated with primary gastric carcinoma tumorigenesis, no predisposing genes in this region have been identified so far. Here, we report the results of genotype and loss of heterozygosity (LOH) analysis on 7q in this tumor. A panel of nine microsatellite markers distributed over the whole chromosome 7q was used for genotyping primary gastric carcinomas. Of 72 primary tumors LOH of D7S486 occurred in 24.0% (12/50) of cases. Fine mapping with 12 additional markers flanking D7S486 resulted in LOH of 30.36% (17/56) and defined one minimal deleted region in primary gastric carcinomas, a 90-kilobase region bounded by D7S2543 and D7S486 at 7q31.2. The allelic deletion correlates statistically with clinicopathologic variables. Our data suggest a possible link between putative tumor suppressor genes and gastric carcinoma in the 7q31 region.

[Advancement of studying the biological characteristics of nasopharyngeal carcinogenesis].

This review is to summarize the main achievements of studying the biological characteristics of nasopharyngeal carcinogenesis performed by the authors' research team and the recent advancement in this field during the past 5 years as well as to explain the authors' viewpoints concerning the nasopharyngeal carcinogenesis. In order to study the nasopharyngeal carcinogenesis, more than 20,000 nasopharyngeal carcinoma biopsies and more than 600 nasopharyngeal biopsies of Epstein-Barr virus seropositive persons who had been got follow-up over 12 years, were collected. In addition, nude mice and cell lines were also to be utilized. Besides histopathological staining, methods of molecular biology, including in-situ hybridization, PCR etc. were applied. Up to date, 26 papers concerning this subject had been formally published in the medico-biological journals at home and abroad. The results and conclusions were as follows. (1) The squamous metaplasia, epithelial dysplasia, carcinoma in-situ and microinvasive carcinoma are the morphogenetic sequence found in nasopharyngeal carcinogenesis. (2) This morphogenetic sequence is frequently observed in a restricted area of nasopharyngeal mucosal epithelium, representing as an appearance of field carcinogenesis. (3) EB virus may play a critical role in nasopharyngeal carcinogenesis, since EB virus DNA and small RNAs could be detected in epithelial dysplasia first and several viral encoded products, especially LMP1, might be expressed in dysplasia, carcinoma in-situ and microinvasive carcinoma. (4) The multigenic mechanisms, including interactions between EB viral genes encoded products and the products abnormally expressed step by step from genes related to cell-cycle regulation, are the molecular events involved in nasopharyngeal carcinogenesis. (5) The cellular immunity of individuals should also be considered as an important factor influencing nasopharyngeal carcinogenesis, because EB virus specific cytotoxic T-lymphocytes could not only be observed in carcinoma nests but also detected in peripheral blood.