title: An insight into the genetic pathway of adenocarcinoma of the small intestine.
abstract: BACKGROUND
  Although the adenoma to carcinoma pathway in colorectal cancer is well described, the mechanisms of carcinogenesis in the small intestine remain unclear.
  
  
  OBJECTIVE
  The aim of this study was to investigate candidate genes in the genetic pathway of adenocarcinoma of the small intestine.
  
  
  METHODS
  A total of 21 non-familial, non-ampullary adenocarcinomas of the small intestine were analysed. DNA was extracted from formalin fixed paraffin wax embedded tissue using standard techniques. The replication error (RER) status was determined by amplification of BAT26. The mutation cluster region (MCR) of the adenomatous polyposis coli (APC) gene was screened using polymerase chain reaction single strand conformational polymorphism and direct sequencing. Immunohistochemistry was performed on formalin fixed paraffin wax embedded tissue using monoclonal antibodies for hMLH1, hMSH2, beta-catenin, E-cadherin, and p53.
  
  
  RESULTS
  Fourteen male and seven female patients with a median age of 64 years (range 21-85) presented with adenocarcinoma of the duodenum (10), jejunum (7), and ileum (4). One cancer (5%) was found to be RER+, and all tumours stained positive for hMLH1 and hMSH2. No mutations were detected in the MCR of the APC gene. beta-Catenin showed increased nuclear expression with loss of membranous staining in 10 cancers (48%). Absent or decreased membrane expression of E-cadherin was found in eight cancers (38%). Strong staining of p53 was found in the nucleus of five cancers (24%).
  
  
  CONCLUSIONS
  We did not detect mutations in the MCR of the APC gene, and this suggests that adenocarcinoma of the small intestine may follow a different genetic pathway to colorectal cancer. Abnormal expression of E-cadherin and beta-catenin was common and reflects an early alternative to APC in this pathway in which mutations may be found in adenocarcinoma of the small intestine.
authors.affiliation: Department of Colorectal Surgery and Imperial Cancer Research Fund, John Radcliffe Hospital, Oxford, UK.
authors.forename: J M D
authors.initials: JM
authors.lastname: Wheeler
authors.forename: B F
authors.initials: BF
authors.lastname: Warren
authors.forename: N J McC
authors.initials: NJ
authors.lastname: Mortensen
authors.forename: H C
authors.initials: HC
authors.lastname: Kim
authors.forename: S C
authors.initials: SC
authors.lastname: Biddolph
authors.forename: G
authors.initials: G
authors.lastname: Elia
authors.forename: N E
authors.initials: NE
authors.lastname: Beck
authors.forename: G T
authors.initials: GT
authors.lastname: Williams
authors.forename: N A
authors.initials: NA
authors.lastname: Shepherd
authors.forename: A C
authors.initials: AC
authors.lastname: Bateman
authors.forename: W F
authors.initials: WF
authors.lastname: Bodmer
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma / Q000235:genetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015820:Cadherins / Q000378:metabolism; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins; D004379:Duodenal Neoplasms / Q000235:genetics*; D005260:Female; D017491:Genes, APC / Q000502:physiology; D006801:Humans; D007078:Ileal Neoplasms / Q000235:genetics*; D007150:Immunohistochemistry / Q000379:methods; D007580:Jejunal Neoplasms / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D016133:Polymerase Chain Reaction / Q000379:methods; D018807:Polymorphism, Single-Stranded Conformational; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051176:beta Catenin
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C495270:CTNNB1 protein, human; D015820:Cadherins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D051176:beta Catenin; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein