title: β-Catenin signaling dosage dictates tissue-specific tumor predisposition in Apc-driven cancer.
abstract: Apc-driven tumor formation in patients and Apc-mutant mouse models is generally attributed to increased levels of β-catenin signaling. We and others have proposed that a specific level of β-catenin signaling is required to successfully initiate tumor formation, and that each tissue prefers different dosages of signaling. This is illustrated by APC genotype-tumor phenotype correlations in cancer patients, and by the different tumor phenotypes displayed by different Apc-mutant mouse models. Apc1638N mice, associated with intermediate β-catenin signaling, characteristically develop intestinal tumors (<10) and extra-intestinal tumors, including cysts and desmoids. Apc1572T mice associated with lower levels of β-catenin signaling are free of intestinal tumors, but instead develop mammary tumors. Although the concept of β-catenin signaling dosage and its impact on tumor growth among tissues is gaining acceptance, it has not been formally proven. Additionally, alternative explanations for Apc-driven tumor formation have been proposed. To obtain direct evidence for the dominant role of β-catenin dosage in tumor formation and tissue-specific tumor predisposition, we crossed Apc1638N mice with heterozygous β-catenin knockout mice, thereby reducing β-catenin levels. Whereas all the Apc1638N;Ctnnb1(+/+) mice developed gastrointestinal tumors, none were present in the Apc1638N;Ctnnb1(-/+) mice. Incidence of other Apc1638N-associated lesions, including desmoids and cysts, was strongly reduced as well. Interestingly, Apc1638N;Ctnnb1(-/+) females showed an increased incidence of mammary tumors, which are normally rarely observed in Apc1638N mice, and the histological composition of the tumors resembled that of Apc1572T-related tumors. Hereby, we provide in vivo genetic evidence confirming the dominant role of β-catenin dosage in tumor formation and in dictating tumor predisposition among tissues in Apc-driven cancer.
authors.affiliation: Department of Gastroenterology and Hepatology, Erasmus MC University Medical Center, Rotterdam, The Netherlands.
authors.forename: E R M
authors.initials: ER
authors.lastname: Bakker
authors.forename: E
authors.initials: E
authors.lastname: Hoekstra
authors.forename: P F
authors.initials: PF
authors.lastname: Franken
authors.forename: W
authors.initials: W
authors.lastname: Helvensteijn
authors.forename: C H M
authors.initials: CH
authors.lastname: van Deurzen
authors.forename: W
authors.initials: W
authors.lastname: van Veelen
authors.forename: E J
authors.initials: EJ
authors.lastname: Kuipers
authors.forename: R
authors.initials: R
authors.lastname: Smits
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D017491:Genes, APC; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D051176:beta Catenin