title: Mutations of p16Ink4/CDKN2 and p15Ink4B/MTS2 genes in biliary tract cancers.
abstract: p16Ink4 and p15Ink4B are cyclin-dependent kinase 4 inhibitors and link to the regulation of cell cycle in mammalian cells. The genes encoding these inhibitors are located at 9p21, which is a frequent site of allelic loss in various types of tumors. Twenty-five primary biliary tract cancers were examined for somatic mutations in p16Ink4/CDKN2, p15Ink4B/MTS2, p53, and K-ras genes and allelic loss of 9p21 by microsatellite analysis. Four biliary tract cancer cell lines were analyzed for homozygous deletions and point mutations. We found frequent homozygous deletions in p16Ink4/CDKN2 and p15Ink4B/MTS2 genes in the biliary tract cancer cell lines. Each cancer cell line had alteration of either p16Ink4/CDKN2, p15Ink4B/MTS2, or p53 genes. In primary tumors, 16 of 25 (64%) biliary tract cancers had point mutations in the p16Ink4/CDKN2 gene. These include 14 missense and 2 silent mutations. The frequency of mutations in gall bladder cancer and hilar bile duct cancer were 80% (8 of 10) and 63% (5 of 8), respectively. Each of codons 1, 80, and 111 was changed in two cases of these cancers. One of three intrahepatic bile duct cancers, one of two common bile duct cancers, and one of two ampullary cancers had mutations in the p16Ink4/CDKN2 gene. In contrast, no mutation in the p15Ink4B/MTS2 gene, one base change in the K-ras gene, and one loss of heterozygosity at the IFN alpha locus in 25 cancers and one base change in the p53 gene in 19 cancers were observed. These results suggest that p16Ink4/CDKN2, rather than p15Ink4B/MTS2 or p53 genes, and its inactivation may be important in biliary tract carcinogenesis.
authors.affiliation: Department of Biochemistry and Molecular Oncology, University of Tsukuba, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yoshida
authors.forename: T
authors.initials: T
authors.lastname: Todoroki
authors.forename: Y
authors.initials: Y
authors.lastname: Ichikawa
authors.forename: S
authors.initials: S
authors.lastname: Hanai
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: M
authors.initials: M
authors.lastname: Hori
authors.forename: K
authors.initials: K
authors.lastname: Fukao
authors.forename: M
authors.initials: M
authors.lastname: Miwa
authors.forename: K
authors.initials: K
authors.lastname: Uchida
mesh_terms: D001483:Base Sequence; D001650:Bile Duct Neoplasms / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm / Q000235:genetics; D005706:Gallbladder Neoplasms / Q000235:genetics*; D016158:Genes, p53; D011905:Genes, ras; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D018807:Polymorphism, Single-Stranded Conformational; D017384:Sequence Deletion; D025521:Tumor Suppressor Proteins
chemical_list: C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm; D025521:Tumor Suppressor Proteins