title: [Microsatellite instability among patients with colorectal cancer].
abstract: BACKGROUND
  In patients with colorectal carcinoma, insertions or deletions of short sequences of DNA, a phenomenon called microsatellite instability, are observed.
  
  
  OBJECTIVE
  To look for microsatellite instability and mutations of MLH1 and MSH2 gene mutations in patients with colorectal carcinoma.
  
  
  METHODS
  Ten patients with sporadic colorectal carcinoma and 31 patients fulfilling criteria for hereditary nonpolyposis colon cancer (HNPCC), aged 9 to 70 years, were studied. Microsatellite instability was studied in samples of tumor and peripheral blood mononuclear cell DNA. Six markers were amplified by polymerase chain reaction and capillary electrophoresis. In samples with microsatellite instability, mutations of MLH1 and MSH2 genes were studied by direct sequencing.
  
  
  RESULTS
  Thirty four percent of patients had microsatellite instability and among these, 76% had a high degree of instability. BAT40 marker had the higher frequency of instability. No mutations for MLH1 and MSH2 genes were observed. However a new polymorphism, C399T, was identified in exon 3 of MSH2 gene. This polymorphism was observed both in patients with sporadic colorectal carcinoma and patients with HNPCC.
  
  
  CONCLUSIONS
  There is a high frequency of microsatellite instability among patients with colorectal cancer. A new polymorphism, not previously reported, was identified in MSH2 gene.
authors.affiliation: Unidad de Genética Médica, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia.
authors.forename: Yenny
authors.initials: Y
authors.lastname: Montenegro
authors.forename: José Luis
authors.initials: JL
authors.lastname: Ramírez-Castro
authors.forename: Luis Fernando
authors.initials: LF
authors.lastname: Isaza
authors.forename: Gabriel
authors.initials: G
authors.lastname: Bedoya
authors.forename: Carlos Mario
authors.initials: CM
authors.lastname: Muñetón-Peña
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000235:genetics*; D002648:Child; D015179:Colorectal Neoplasms / Q000235:genetics*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000175:diagnosis / Q000235:genetics; D004252:DNA Mutational Analysis; D005820:Genetic Testing; D006801:Humans; D053842:Microsatellite Instability; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic / Q000235:genetics*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein