title: KRAS, BRAF oncogene mutations and tissue specific promoter hypermethylation of tumor suppressor SFRP2, DAPK1, MGMT, HIC1 and p16 genes in colorectal cancer patients.
abstract: BACKGROUND
  Colorectal cancer is a serious disease that causes significant morbidity and mortality in developed countries. Genetic changes, such as mutations in proto-oncogenes and DNA repair genes, and loss of function in the tumor suppressor genes cause colorectal cancer development. Abnormal DNA methylation is also known to play a crucial role in colorectal carcinogenesis.
  
  
  OBJECTIVE
  In this study, frequencies of KRAS and BRAF mutations, promoter hypermethylation profiles of SFRP2, DAPK1, MGMT, HIC1 and p16 genes, and possible associations between hypermethylation of these genes and KRAS and BRAF mutations were aimed to find out.
  
  
  METHODS
  Ninety three colorectal cancer tissues and 14 normal colon mucosas were included in the study. Common twelve KRAS gene mutation were investigated with using reverse-hybridization strip assay method. BRAF V600E mutations were investigated with RFLP method. Hypermethylation status of five tumor suppressor genes were detected by using reverse-hybridization strip assay method after bisulfite modification of DNA.
  
  
  RESULTS
  KRAS and BRAF mutation frequencies were determined as 54.84% and 12.9%, respectively. Promoter hypermethylation frequencies of tumor suppressor genes SFRP2, DAPK1, MGMT, HIC1 and p16 were determined as 66.7%, 45.2%, 40.9%, 40.9% and 15.1%, respectively. Statistically significant associations were found between BRAF mutation and SFRP2 and p16 tumor suppressor genes hypermethylation (SFRP2; p= 0.005, p16; p= 0.016). Compared to rectum, SFRP2 (p= 0.017) and MGMT (p= 0.013) genes have statistically significantly higher promoter hypermethylation in colon.
  
  
  CONCLUSIONS
  Results of the current study have confirmed that KRAS mutations and SFRP2 hypermethylation can be used as genetic markers in colorectal cancer.
authors.affiliation: Department of Nutrition and Dietetics, Faculty of Health Sciences, Cumhuriyet University, Sivas, Turkey.|Advanced Technology Research Center (CÜTAM), Cumhuriyet University, Sivas, Turkey.
authors.forename: Binnur
authors.initials: B
authors.lastname: Bagci
authors.affiliation: Department of Biology, Faculty of Science, Cumhuriyet University, Sivas, Turkey.
authors.forename: Musa
authors.initials: M
authors.lastname: Sari
authors.affiliation: Department of General Surgery, Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: Kursat
authors.initials: K
authors.lastname: Karadayi
authors.affiliation: Department of General Surgery, Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Turan
authors.affiliation: Department of Medical Genetics, Faculty of Medicine, On Sekiz Mart University, Çanakkale, Turkey.
authors.forename: Ozturk
authors.initials: O
authors.lastname: Ozdemir
authors.affiliation: Department of Medical Genetics, Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: Gokhan
authors.initials: G
authors.lastname: Bagci
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003062:Codon; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D018899:CpG Islands; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000235:genetics; D045643:DNA Repair Enzymes / Q000235:genetics; D005260:Female; D019942:Genes, p16; D011905:Genes, ras; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D059645:Mutation Rate; D015513:Oncogene Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: D003062:Codon; D015513:Oncogene Proteins; D025521:Tumor Suppressor Proteins; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D048493:Proto-Oncogene Proteins B-raf; D045643:DNA Repair Enzymes
keywords: BRAF; Colorectal cancer; DAPK1; HIC1; KRAS; MGMT; SFRP2; hypermethylation; oncogene; p16; tumor suppressor gene