Functional redundancy between Apc and Apc2 regulates tissue homeostasis and prevents tumorigenesis in murine mammary epithelium

Oncogene. 2017 Mar 30;36(13):1793-1803. doi: 10.1038/onc.2016.342. Epub 2016 Oct 3.


Aberrant Wnt signaling within breast cancer is associated with poor prognosis, but regulation of this pathway in breast tissue remains poorly understood and the consequences of immediate or long-term dysregulation remain elusive. The exact contribution of the Wnt-regulating proteins adenomatous polyposis coli (APC) and APC2 in the pathogenesis of human breast cancer are ill-defined, but our analysis of publically available array data sets indicates that tumors with concomitant low expression of both proteins occurs more frequently in the 'triple negative' phenotype, which is a subtype of breast cancer with particularly poor prognosis. We have used mouse transgenics to delete Apc and/or Apc2 from mouse mammary epithelium to elucidate the significance of these proteins in mammary homeostasis and delineate their influences on Wnt signaling and tumorigenesis. Loss of either protein alone failed to affect Wnt signaling levels or tissue homeostasis. Strikingly, concomitant loss led to local disruption of β-catenin status, disruption in epithelial integrity, cohesion and polarity, increased cell division and a distinctive form of ductal hyperplasia with 'squamoid' ghost cell nodules in young animals. Upon aging, the development of Wnt activated mammary carcinomas with squamous differentiation was accompanied by a significantly reduced survival. This novel Wnt-driven mammary tumor model highlights the importance of functional redundancies existing between the Apc proteins both in normal homeostasis and in tumorigenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenomatous Polyposis Coli Protein / genetics*
  • Adenomatous Polyposis Coli Protein / metabolism*
  • Animals
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / mortality
  • Breast Neoplasms / pathology
  • Carcinogenesis / genetics
  • Carcinogenesis / metabolism
  • Cell Transformation, Neoplastic / genetics*
  • Cell Transformation, Neoplastic / metabolism*
  • Cytoskeletal Proteins / genetics*
  • Cytoskeletal Proteins / metabolism*
  • DNA Copy Number Variations
  • Epithelium / metabolism*
  • Epithelium / pathology
  • Female
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic
  • Gene Knockdown Techniques
  • Homeostasis / genetics
  • Humans
  • Hyperplasia
  • Lactation / genetics
  • Mammary Neoplasms, Animal
  • Mice
  • Mice, Transgenic
  • Prognosis
  • beta Catenin / genetics
  • beta Catenin / metabolism


  • APC2 protein, human
  • Adenomatous Polyposis Coli Protein
  • Cytoskeletal Proteins
  • beta Catenin