title: [Immunohistochemical analysis of mismatch repair proteins in colorectal adenomas].
abstract: BACKGROUND
  The deficiency of mismatch repair system is one of the main pathways in colorectal cancer. This system consists mainly of four proteins: MLH1, MSH2, MSH6 and PMS2. Colorectal cancer develops in the majority of cases from precancerous lesions called adenomas. Only few studies have reported on the deficiencies of these proteins in adenomas.
  
  
  OBJECTIVE
  In this study we used immunohistochemistry staining in colorectal adenomas to assay functional status of MLH1, MSH2, MSH6, and PMS2 proteins.
  
  
  METHODS
  102 adenomas from 93 patients were collected in our institution during six years (2007-2012). The immunohistochemical technique was performed with 4 antibodies: MLH1, MSH2, MSH6 and PMS2. The loss of expression was retained if adenomatous cells were not stained with positive internal control. Staining was considered as abnormal if nucleus of adenomatous cells showed low nuclear staining and / or heterogeneous one, while positive internal control had normal staining.
  
  
  RESULTS
  Loss of expression of MSH2 and MSH6 in adenomatous cells was found in only 1 case which was a tubular adenoma 3mm high-grade dysplasia. Abnormal staining of the adenomatous cells was noted in 23 cases (22.5%) for MSH2 and in 8 cases (7.8%) for MSH6. No cases showed loss of expression of MLH1 and PMS2. Abnormal expression of MSH2 and MSH6 was not correlated with sex of patients, the location of the adenoma, its grade of dysplasia and its histological type.
  
  
  CONCLUSIONS
  Loss of Mismatch repair proteins expression is a rare event in adenomas. However, the abnormal expression levels are higher in our study compared to those reported in the literature. This could reflect a higher rate of microsatellite instability in our patients. Multicenter and larger studies with molecular biology techniques are needed.
authors: Soumaya
authors: S
authors: Rammeh
authors: Nadia
authors: N
authors: Sabbegh Znaidi
authors: Amira
authors: A
authors: Arfaoui
authors: Kaouther
authors: K
authors: Ayouni
authors: Ahlem
authors: A
authors: Blel
authors: Faten
authors: F
authors: Farah
authors: Yosra
authors: Y
authors: Zidi
authors: Taoufik
authors: T
authors: Najjar
authors: Nadia
authors: N
authors: Kourda
authors: Yosra
authors: Y
authors: Said
authors: Rachida
authors: R
authors: Zermani
mesh_terms: D000236:Adenoma / Q000201:enzymology* / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics; D045643:DNA Repair Enzymes / Q000032:analysis / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000032:analysis / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D051718:MutS Homolog 2 Protein / Q000032:analysis / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes