title: Molecular subtypes of colorectal cancers determined by PCR-based analysis.
abstract: Tumor tissue consists of a heterogeneous cell population. The allelic imbalance (AI) ratio, determined in isolated tumor glands, is a good index of tumor heterogeneity. However, associations of the patterns of AI and microsatellite instability (MSI) development, observed in most cases of colorectal cancer (CRC), with tumor progression have not been reported previously. In this study, we examined whether CRC genetic profiles stratified by a combination of the AI ratio and MSI facilitate categorization of CRC, and whether these genetic profiles are associated with specific molecular alterations in CRC. A crypt isolation method was used to isolate DNA from tumors and normal glands obtained from 147 sporadic CRCs. AI and MSI statuses were determined using PCR-based microsatellite analysis and stratified based on AI ratio and MSI status. DNA methylation status (high methylation, intermediate methylation and low methylation status and mutations in KRAS, BRAF, and TP53 were examined. In addition, mucin markers were immunostained. Based on this analysis, four subgroups were categorized. Subgroup 1 was characterized by a high MSI status and BRAF mutation; subgroup 2 was closely associated with a high AI ratio, which accumulated during the early phases of colorectal carcinogenesis, and TP53 mutation; subgroup 3 was associated with a low AI ratio, seen during the later phases of colorectal carcinogenesis, and KRAS mutation; and subgroup 4 was defined as a minor subgroup. These results confirmed that classification of distinct molecular profiles provides important insights into colorectal carcinogenesis.
authors.affiliation: Department of Molecular Diagnostic Pathology, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Sugai
authors.affiliation: Department of Molecular Diagnostic Pathology, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Eizuka
authors.affiliation: Department of Molecular Diagnostic Pathology, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Molecular Diagnostic Pathology, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Fukagawa
authors.affiliation: Pharmacodynamics and Molecular Genetics, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Habano
authors.affiliation: Department of Molecular Biology, Sapporo Medical University, Sapporo, Japan.
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Yamamoto
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Risaburo
authors.initials: R
authors.lastname: Akasaka
authors.affiliation: Department of Surgery, School of Medicine, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Kouki
authors.initials: K
authors.lastname: Otuska
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, School of Pharmacy, Iwate Medical University, Morioka, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Molecular Biology, Sapporo Medical University, Sapporo, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000145:classification / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D018895:Microsatellite Repeats / Q000235:genetics*; D008875:Middle Aged; D009077:Mucins / Q000276:immunology; D009154:Mutation / Q000235:genetics; D016133:Polymerase Chain Reaction; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: C117307:KRAS protein, human; D009077:Mucins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras)
keywords: Allelic imbalance; cluster analysis; colorectal cancer; methylation; microsatellite instability