title: Whole-genome analyses of loss of heterozygosity and methylation analysis of four tumor-suppressor genes in N-methyl-N'-nitro-N-nitrosoguanidine-induced rat stomach carcinomas.
abstract: N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced rat stomach carcinomas are considered to be a good model for differentiated-type human stomach carcinomas. However, as for their molecular basis, only infrequent mutations of Catnb (beta-catenin) and Trp53 (p53) have been observed. Here, we carried out a whole-genome analysis of loss of heterozygosity (LOH) using 21 stomach carcinomas induced by MNNG in F(1) hybrids of ACI and BUF rats, and also analyzed promoter methylation of four tumor-suppressor genes. LOH analysis was performed using 130 polymorphic markers covering rat chromosomes 1-20 with an average interval of 20 Mbp. Despite adapting conditions so that LOH could be detected with up to a 50% contamination of stromal cells, no LOH was detected at any loci. CpG islands in putative promoter regions of four tumor-suppressor genes, Cdh1 (E-cadherin), Cdkn2a (p16), Mlh1, and Rassf1a, were analyzed by methylation-specific polymerase chain reaction (PCR). However, no methylation was detected. In contrast, the promoter region of Pgc (pepsinogen C), which lacks a CpG island, was methylated in all 21-cancer samples. These results indicated that LOH spanning a chromosomal region larger than 30-40 Mbp or silencing of Cdh1, Cdkn2a, Mlh1, and Rassf1a, was not involved in MNNG-induced rat stomach carcinomas. The search for other genes involved in these carcinomas needs to be continued.
authors.affiliation: Carcinogenesis Division, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Niwa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuramoto
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nomoto
authors.forename: Kuniko
authors.initials: K
authors.lastname: Wakazono
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Fujita
authors.forename: Taijiro
authors.initials: T
authors.lastname: Matsushima
authors.forename: Masae
authors.initials: M
authors.lastname: Tatematsu
authors.forename: Takashi
authors.initials: T
authors.lastname: Sugimura
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Ushijima
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015820:Cadherins / Q000235:genetics; D002352:Carrier Proteins; D018899:CpG Islands / Q000235:genetics; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D019175:DNA Methylation; D016147:Genes, Tumor Suppressor; D016678:Genome; D019656:Loss of Heterozygosity; D008769:Methylnitronitrosoguanidine; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D051381:Rats; D011912:Rats, Inbred ACI; D011915:Rats, Inbred BUF; D013274:Stomach Neoplasms / Q000139:chemically induced / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015820:Cadherins; D002352:Carrier Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; C501486:MLH1 protein, human; C501484:Mlh1 protein, rat; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; C411762:RASSF1 protein, human; D025521:Tumor Suppressor Proteins; D008769:Methylnitronitrosoguanidine; D000070957:MutL Protein Homolog 1