Structure and Methylation-Based Silencing of a Gene (DBCCR1) within a Candidate Bladder Cancer Tumor Suppressor Region at 9q32–q33

• Published in: Genomics (San Diego, Calif.) Calif.), 1998-03, Vol.48 (3), p.277-288
• Main Authors: Habuchi, Tomonori, Luscombe, Mike, Elder, Patricia A., Knowles, Margaret A.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Azacitidine - analogs & derivatives; Azacitidine - pharmacology; Base Sequence; Biological and medical sciences; Blotting, Northern; Blotting, Southern; Carcinoma, Transitional Cell - genetics; Chromosomes, Artificial, Yeast; Chromosomes, Human, Pair 9; CpG Islands - genetics; DNA Methylation; DNA, Complementary; Exons - genetics; Gene Deletion; Gene Expression Regulation, Neoplastic - drug effects; Genes, Tumor Suppressor; Humans; Introns - genetics; Medical sciences; Molecular Sequence Data; Nephrology. Urinary tract diseases; Polymorphism, Single-Stranded Conformational; Proteins - genetics; RNA, Messenger - metabolism; Sequence Analysis, DNA; Tumor Suppressor Proteins; Tumors of the urinary system; Urinary Bladder Neoplasms - genetics; Urinary tract. Prostate gland; Urothelium - metabolism
• ISSN: 0888-7543; 1089-8646
• DOI: 10.1006/geno.1997.5165

Loss of heterozygosity (LOH) on chromosome 9q is the most frequent genetic alteration in transitional cell carcinoma (TCC) of the bladder, indicating the presence of one or more relevant tumor suppressor genes. We previously mapped one of these putative tumor suppressor loci to 9q32–q33 and localized the candidate region within a single YAC 840 kb in size. This locus has been designatedDBC1(for deleted in bladder cancer gene 1). We have identified a novel gene,DBCCR1,in this candidate region by searching for expressed sequence tags (ESTs) that map to YACs spanning the region. Database searching using the entireDBCCR1cDNA sequence identified several human ESTs and a few homologous mouse ESTs. However, the predicted 761-amino-acid sequence had no significant homology to known protein sequences. Mutation analysis of the coding region and Southern blot analysis detected neither somatic mutations nor gross genetic alterations in primary TCCs. AlthoughDBCCR1was expressed in multiple normal human tissues including urothelium, mRNA expression was absent in 5 of 10 (50%) bladder cancer cell lines. Methylation analysis of the CpG island at the 5′ region of the gene and the induction ofde novoexpression by a demethylating agent indicated that this island might be a frequent target for hypermethylation and that hypermethylation-based silencing of the gene occurs in TCC. These findings makeDBCCR1a good candidate forDBC1.