Activation of different Wnt/beta-catenin signaling components in mammary epithelium induces transdifferentiation and the formation of pilar tumors

Oncogene. 2002 Aug 15;21(36):5548-56. doi: 10.1038/sj.onc.1205686.


The Wnt/beta-catenin signaling pathway controls cell fate and neoplastic transformation. Expression of an endogenous stabilized beta-catenin (DeltaE3 beta-catenin) in mammary epithelium leads to the transdifferentiation into epidermis- and pilar-like structures. Signaling molecules in the canonical Wnt pathway upstream from beta-catenin induce glandular tumors but it is not clear whether they also cause squamous transdifferentiation. To address this question we have now investigated mammary epithelium from transgenic mice that express activating molecules of the Wnt pathway: Wnt10b, Int2/Fgf3, CK2alpha, DeltaE3 beta-catenin, Cyclin D1, and dominant negative (dn) GSK3beta. Cytokeratin 5 (CK5), which is expressed in both mammary myoepithelium and epidermis, and the epidermis-specific CK1 and CK6 were used as differentiation markers. Extensive squamous metaplasias and widespread expression of CK1 and CK6 were observed in DeltaE3 beta-catenin transgenic mammary tissue. Wnt10b and Int2 transgenes also induced squamous metaplasias, but expression of CK1 and CK6 was sporadic. While CK5 expression in Wnt10b transgenic tissue was still confined to the lining cell layer, its expression in Int2 transgenic tissue was completely disorganized. In contrast, cytokeratin expression in CK2alpha, dnGSK3beta and Cyclin D1 transgenic mammary tissues was similar to that in DeltaE3 beta-catenin tissue. In support of transdifferentiation, expression of hard keratins specific for hair and nails was observed in pilar tumors. These results demonstrate that the activation of Wnt signaling components in mammary epithelium induces not only glandular tumors but also squamous differentiation, possibly by activating LEF-1, which is expressed in normal mammary epithelium.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Breast / metabolism*
  • Breast / pathology
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cell Transformation, Neoplastic / metabolism*
  • Cell Transformation, Neoplastic / pathology
  • Cyclin D1 / genetics
  • Cyclin D1 / metabolism
  • Cytoskeletal Proteins / metabolism*
  • DNA-Binding Proteins / metabolism
  • Female
  • Fibroblast Growth Factor 3
  • Fibroblast Growth Factors / genetics
  • Fibroblast Growth Factors / metabolism
  • Glycogen Synthase Kinase 3
  • Immunoenzyme Techniques
  • Keratins / metabolism
  • Lymphoid Enhancer-Binding Factor 1
  • Mammary Neoplasms, Experimental / metabolism*
  • Mammary Neoplasms, Experimental / pathology
  • Mice
  • Mice, Transgenic
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Signal Transduction*
  • Trans-Activators / metabolism*
  • Transcription Factors / metabolism
  • Up-Regulation
  • Wnt Proteins
  • beta Catenin


  • CTNNB1 protein, mouse
  • Cytoskeletal Proteins
  • DNA-Binding Proteins
  • Fgf3 protein, mouse
  • Fibroblast Growth Factor 3
  • Lef1 protein, mouse
  • Lymphoid Enhancer-Binding Factor 1
  • Proto-Oncogene Proteins
  • Trans-Activators
  • Transcription Factors
  • Wnt Proteins
  • Wnt10b protein, mouse
  • beta Catenin
  • Cyclin D1
  • Fibroblast Growth Factors
  • Keratins
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Glycogen Synthase Kinase 3