title: Colorectal cancers show distinct mutation spectra in members of the canonical WNT signaling pathway according to their anatomical location and type of genetic instability.
abstract: It is unclear whether the mutation spectra in WNT genes vary among distinct types of colorectal tumors. We have analyzed mutations in specific WNT genes in a cohort of 52 colorectal tumors and performed a meta-analysis of previous studies. Notably, significant differences were found among the mutation spectra. We have previously shown that in familial adenomatous polyposis, APC somatic mutations are selected to provide the "just-right" level of WNT signaling for tumor formation. Here, we found that APC mutations encompassing at least two beta-catenin down-regulating motifs (20 a.a. repeats) are significantly more frequent in microsatellite unstable (MSI-H) than in microsatellite stable (MSS) tumors where truncations retaining less than two repeats are more frequent (P = 0.0009). Moreover, in cases where both APC hits are detected, selection for mutations retaining a cumulative number of two 20 a.a. repeats became apparent in MSI-H tumors (P = 0.001). This type of mutations were also more frequent in proximal versus distal colonic tumors, regardless of MSI status (P = 0.0008). Among MSI-H tumors, CTNNB1 mutations were significantly more frequent in HNPCC than in sporadic lesions (28% versus 6%, P < 10-6) and were preferentially detected in the proximal colon, independently of MSI status (P = 0.017). In conclusion, the observed spectra of WNT gene mutations in colorectal tumors are likely the result from selection of specific levels of beta-catenin signaling, optimal for tumor formation in the context of specific anatomical locations and forms of genetic instability. We suggest that this may underlie the preferential location of MMR deficient tumors in the proximal colon.
authors.affiliation: Centro de Investigação de Patobiologia Molecular (CIPM), Instituto Português de Oncologia de Lisboa Francisco Gentil, EPE, Lisboa, Portugal. mc.albuquerque@sapo.pt
authors.forename: Cristina
authors.initials: C
authors.lastname: Albuquerque
authors.forename: Célia
authors.initials: C
authors.lastname: Baltazar
authors.forename: Bruno
authors.initials: B
authors.lastname: Filipe
authors.forename: Filipa
authors.initials: F
authors.lastname: Penha
authors.forename: Teresa
authors.initials: T
authors.lastname: Pereira
authors.forename: Ron
authors.initials: R
authors.lastname: Smits
authors.forename: Marília
authors.initials: M
authors.lastname: Cravo
authors.forename: Pedro
authors.initials: P
authors.lastname: Lage
authors.forename: Paulo
authors.initials: P
authors.lastname: Fidalgo
authors.forename: Isabel
authors.initials: I
authors.lastname: Claro
authors.forename: Paula
authors.initials: P
authors.lastname: Rodrigues
authors.forename: Isabel
authors.initials: I
authors.lastname: Veiga
authors.forename: José Silva
authors.initials: JS
authors.lastname: Ramos
authors.forename: Isabel
authors.initials: I
authors.lastname: Fonseca
authors.forename: Carlos Nobre
authors.initials: CN
authors.lastname: Leitão
authors.forename: Riccardo
authors.initials: R
authors.lastname: Fodde
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000236:Adenoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D060466:Axin Protein; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000235:genetics*; D017491:Genes, APC; D006801:Humans; D007124:Immunoenzyme Techniques; D053842:Microsatellite Instability; D009154:Mutation / Q000235:genetics*; D015398:Signal Transduction; D051153:Wnt Proteins / Q000235:genetics*; D051176:beta Catenin / Q000235:genetics* / Q000378:metabolism
chemical_list: C491761:AXIN2 protein, human; D060466:Axin Protein; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D051153:Wnt Proteins; D051176:beta Catenin