title: Mismatch repair genes expression defects & association with clinicopathological characteristics in colorectal carcinoma.
abstract: OBJECTIVE
  DNA mismatch repair gene (MMR) abnormalities are seen in 95 per cent of hereditary nonpolyposis colorectal cancer (HNPCC) and 10-15 per cent of sporadic colorectal cancers. There are no data on MMR abnormalities in Malaysian colorectal cancer patients. This study was aimed to determine the frequency of abnormal MMR gene protein expression in colorectal carcinoma in Northern Peninsular Malaysia using immunohistochemistry.
  
  
  METHODS
  Clinicopathological information was obtained from 148 patients' records who underwent bowel resection for colorectal cancer (CRC) at the three hospitals in Malaysia. Immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 proteins were performed on paraffin embedded tissue containing carcinoma.
  
  
  RESULTS
  A total of 148 subjects and 150 colorectal carcinomas of sporadic and hereditary types were assessed. Three patients had synchronous tumours. Twenty eight cancers (18.6%) from 26 subjects (17.6%) had absent immunohistochemical expression of any one of the MMR gene proteins. This comprised absent MLH1 only - 3 cancers, absent MSH2 only - 3, absent MSH6 only - 2, absent PMS2 only - 3, absent MLH1 and PMS2 - 14, absent MSH2 and MSH6 - 2 and absent MLH1, MSH6 and PMS2 - 1. There was significant association between abnormal MMR gene protein expression and proximal colon cancers, mucinous, signet ring and poorly differentiated morphology.
  
  
  CONCLUSIONS
  Cancers with abnormal MMR gene expression were associated with microsatellite instability-high (MSI-H) phenotype. About 15 per cent demonstrated absent MSH2, MSH6 and PMS2 protein expression in isolation or in combination with other MMR genes, which often predicts a germline mutation, synonymous with a diagnosis of HNPCC. This appears to be high frequency compared to reported data.
authors.affiliation: Institute for Research in Molecular Medicine, Universiti Sains Malaysia, Penang, Malaysia. gurjeet@usm.my
authors.forename: Gurjeet
authors.initials: G
authors.lastname: Kaur
authors.forename: Abdelhafid
authors.initials: A
authors.lastname: Masoud
authors.forename: N
authors.initials: N
authors.lastname: Raihan
authors.forename: M
authors.initials: M
authors.lastname: Radzi
authors.forename: W
authors.initials: W
authors.lastname: Khamizar
authors.forename: Lee Suk
authors.initials: LS
authors.lastname: Kam
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics / Q000473:pathology; D053843:DNA Mismatch Repair / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D015870:Gene Expression / Q000235:genetics; D018095:Germ-Line Mutation / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D008296:Malaysia; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D051719:MutS DNA Mismatch-Binding Protein / Q000378:metabolism; D051718:MutS Homolog 2 Protein / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D012189:Retrospective Studies
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C497172:MSH2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D051719:MutS DNA Mismatch-Binding Protein; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes