title: Features of colorectal cancers with high-level microsatellite instability occurring in familial and sporadic settings: parallel pathways of tumorigenesis.
abstract: High-level microsatellite instability (MSI-H) is demonstrated in 10 to 15% of sporadic colorectal cancers and in most cancers presenting in the inherited condition hereditary nonpolyposis colorectal cancer (HNPCC). Distinction between these categories of MSI-H cancer is of clinical importance and the aim of this study was to assess clinical, pathological, and molecular features that might be discriminatory. One hundred and twelve MSI-H colorectal cancers from families fulfilling the Bethesda criteria were compared with 57 sporadic MSI-H colorectal cancers. HNPCC cancers presented at a lower age (P < 0.001) with no sporadic MSI-H cancer being diagnosed before the age of 57 years. MSI was less extensive in HNPCC cancers with 72% microsatellite markers showing band shifts compared with 87% in sporadic tumors (P < 0.001). Absent immunostaining for hMSH2 was only found in HNPCC tumors. Methylation of hMLH1 was observed in 87% of sporadic cancers but also in 55% of HNPCC tumors that showed loss of expression of hMLH1 (P = 0.02). HNPCC cancers were more frequently characterized by aberrant beta-catenin immunostaining as evidenced by nuclear positivity (P < 0.001). Aberrant p53 immunostaining was infrequent in both groups. There were no differences with respect to 5q loss of heterozygosity or codon 12 K-ras mutation, which were infrequent in both groups. Sporadic MSI-H cancers were more frequently heterogeneous (P < 0.001), poorly differentiated (P = 0.02), mucinous (P = 0.02), and proximally located (P = 0.04) than HNPCC tumors. In sporadic MSI-H cancers, contiguous adenomas were likely to be serrated whereas traditional adenomas were dominant in HNPCC. Lymphocytic infiltration was more pronounced in HNPCC but the results did not reach statistical significance. Overall, HNPCC cancers were more like common colorectal cancer in terms of morphology and expression of beta-catenin whereas sporadic MSI-H cancers displayed features consistent with a different morphogenesis. No individual feature was discriminatory for all HNPCC cancers. However, a model based on four features was able to classify 94.5% of tumors as sporadic or HNPCC. The finding of multiple differences between sporadic and familial MSI-H colorectal cancer with respect to both genotype and phenotype is consistent with tumorigenesis through parallel evolutionary pathways and emphasizes the importance of studying the two groups separately.
authors.affiliation: Conjoint Gastroenterology Laboratory, Royal Brisbane Hospital Foundation Clinical Research Centre, Bancroft Centre, Herston, Australia. joanney@qimr.edu.au
authors.forename: J
authors.initials: J
authors.lastname: Young
authors.forename: L A
authors.initials: LA
authors.lastname: Simms
authors.forename: K G
authors.initials: KG
authors.lastname: Biden
authors.forename: C
authors.initials: C
authors.lastname: Wynter
authors.forename: V
authors.initials: V
authors.lastname: Whitehall
authors.forename: R
authors.initials: R
authors.lastname: Karamatic
authors.forename: J
authors.initials: J
authors.lastname: George
authors.forename: J
authors.initials: J
authors.lastname: Goldblatt
authors.forename: I
authors.initials: I
authors.lastname: Walpole
authors.forename: S A
authors.initials: SA
authors.lastname: Robin
authors.forename: M M
authors.initials: MM
authors.lastname: Borten
authors.forename: R
authors.initials: R
authors.lastname: Stitz
authors.forename: J
authors.initials: J
authors.lastname: Searle
authors.forename: D
authors.initials: D
authors.lastname: McKeone
authors.forename: L
authors.initials: L
authors.lastname: Fraser
authors.forename: D R
authors.initials: DR
authors.lastname: Purdie
authors.forename: K
authors.initials: K
authors.lastname: Podger
authors.forename: R
authors.initials: R
authors.lastname: Price
authors.forename: R
authors.initials: R
authors.lastname: Buttenshaw
authors.forename: M D
authors.initials: MD
authors.lastname: Walsh
authors.forename: M
authors.initials: M
authors.lastname: Barker
authors.forename: B A
authors.initials: BA
authors.lastname: Leggett
authors.forename: J R
authors.initials: JR
authors.lastname: Jass
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002352:Carrier Proteins; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D019175:DNA Methylation; D004268:DNA-Binding Proteins; D005260:Female; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D019656:Loss of Heterozygosity; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D008875:Middle Aged; D015999:Multivariate Analysis; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009154:Mutation; D009363:Neoplasm Proteins / Q000032:analysis / Q000235:genetics; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000032:analysis; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D018125:Receptors, Transforming Growth Factor beta; D016159:Tumor Suppressor Protein p53; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein