title: Who takes the lead in the development of ulcerative colitis-associated colorectal cancers: mutator, suppressor, or methylator pathway?
abstract: Although several genetic alterations have been identified in patients with ulcerative colitis (UC), it remains unclear whether these changes indicate an increased risk for malignancy. This paper analyzes the involvement of suppressor, mutator, and methylator pathways in malignant transformation associated with UC. A total of 60 colonic samples (47 affected non-neoplastic mucosa, 7 dysplasia, and 6 carcinoma) from 51 UC patients were analyzed for 22 microsatellite markers. p53 gene exons 5-8 were analyzed by single-strand conformational polymorphism, and APC gene by denaturing gradient gel electrophoresis (exons 1-14) and protein truncation test (exon 15). Methylation studies for MLH1 and CSPG2 genes were also performed. Microsatellite instability was absent in all samples whereas allelic imbalance (AI) and loss of heterozygosity (LOH) were detected mainly in samples with neoplastic transformation (P<0.0001). AI and/or LOH at loci located on chromosomes 5, 9, and 18 were significantly more frequent in neoplastic samples (P<0.01), as were TP53 gene mutations (P<0.007). A single mutation was detected for APC gene in a cancer sample. MLH1 gene methylation was absent in all analyzed samples, whereas CSPG2 gene methylation was detected in a single non-neoplastic sample. Our results suggest that the suppressor pathway plays the main role in UC associated tumorigenic progression. LOH at specific loci located on chromosomes 5, 9, and 18 appears to be specifically associated with malignancy risk.
authors.affiliation: Centro de Investigação em Patobiologia Molecular (CIPM), Instituto Português de Oncologia Francisco Gentil, Lisbon, Portugal. laramaia@iol.pt
authors.forename: Lara
authors.initials: L
authors.lastname: Maia
authors.forename: Joana
authors.initials: J
authors.lastname: Dinis
authors.forename: Marília
authors.initials: M
authors.lastname: Cravo
authors.forename: Isabel
authors.initials: I
authors.lastname: Claro
authors.forename: Célia
authors.initials: C
authors.lastname: Baltazar
authors.forename: Isabel
authors.initials: I
authors.lastname: Fonseca
authors.forename: Tavarela
authors.initials: T
authors.lastname: Veloso
authors.forename: Ana F
authors.initials: AF
authors.lastname: Capelinha
authors.forename: Fátima
authors.initials: F
authors.lastname: Carneiro
authors.forename: Carlos
authors.initials: C
authors.lastname: Nobre-Leitão
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D002352:Carrier Proteins; D002471:Cell Transformation, Neoplastic; D011508:Chondroitin Sulfate Proteoglycans / Q000235:genetics; D003093:Colitis, Ulcerative / Q000150:complications*; D015179:Colorectal Neoplasms / Q000235:genetics*; D019175:DNA Methylation; D005260:Female; D017491:Genes, APC; D016147:Genes, Tumor Suppressor; D016158:Genes, p53; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009154:Mutation; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins / Q000235:genetics; D009687:Nuclear Proteins; D053675:Versicans
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D011508:Chondroitin Sulfate Proteoglycans; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C508322:VCAN protein, human; D053675:Versicans; D000070957:MutL Protein Homolog 1