A targeted constitutive mutation in the APC tumor suppressor gene underlies mammary but not intestinal tumorigenesis.
Germline mutations in the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant hereditary predisposition to the development of multiple colorectal adenomas and of a broad spectrum of extra-intestinal tumors. Moreover, somatic APC mutations play a rate-limiting and initiating role in the majority of sporadic colorectal cancers. Notwithstanding its multifunctional nature, the main tumor suppressing activity of the APC gene resides in its ability to regulate Wnt/beta-catenin signaling. Notably, genotype-phenotype correlations have been established at the APC gene between the length and stability of the truncated proteins encoded by different mutant alleles, the corresponding levels of Wnt/beta-catenin signaling activity they encode for, and the incidence and distribution of intestinal and extra-intestinal tumors. Here, we report a novel mouse model, Apc1572T, obtained by targeting a truncated mutation at codon 1572 in the endogenous Apc gene. This hypomorphic mutant allele results in intermediate levels of Wnt/beta-catenin signaling activation when compared with other Apc mutations associated with multifocal intestinal tumors. Notwithstanding the constitutive nature of the mutation, Apc(+/1572T) mice have no predisposition to intestinal cancer but develop multifocal mammary adenocarcinomas and subsequent pulmonary metastases in both genders. The histology of the Apc1572T primary mammary tumours is highly heterogeneous with luminal, myoepithelial, and squamous lineages and is reminiscent of metaplastic carcinoma of the breast in humans. The striking phenotype of Apc(+/1572T) mice suggests that specific dosages of Wnt/beta-catenin signaling activity differentially affect tissue homeostasis and initiate tumorigenesis in an organ-specific fashion.
Gaspar
Claudia
C
Department of Pathology, Josephine Nefkens Institute, Erasmus MC, Rotterdam, The Netherlands.
Franken
Patrick
P
Molenaar
Lia
L
Breukel
Cor
C
van der Valk
Martin
M
Smits
Ron
R
Fodde
Riccardo
R
D011125:Adenomatous Polyposis Coli / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D018390:Gene Targeting; D018095:Germ-Line Mutation; D006801:Humans; D007414:Intestinal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008297:Male; D015674:Mammary Neoplasms, Animal / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020125:Mutation, Missense; D009928:Organ Specificity; D015398:Signal Transduction; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
D025601:Adenomatous Polyposis Coli Protein; D051153:Wnt Proteins; D051176:beta Catenin