Paracrine Wnt signaling both promotes and inhibits human breast tumor growth

Proc Natl Acad Sci U S A. 2013 Apr 23;110(17):6991-6. doi: 10.1073/pnas.1303671110. Epub 2013 Apr 4.


Wnt signaling in mouse mammary development and tumorigenesis has been heavily studied and characterized, but its role in human breast cancer remains elusive. Although Wnt inhibitors are in early clinical development, it is unclear whether they will be of therapeutic benefit to breast cancer patients, and subsequently, to which ones. To address this, we generated a panel of Wnt reporting human breast cancer cell lines and identified a previously unrecognized enrichment for the ability to respond to Wnt in the basal B or claudin-low subtype, which has a poor prognosis and no available targeted therapies. By co-injecting Wnt3A expressing human mammary fibroblasts with human breast cancer cell lines into mouse mammary fat pads, we showed that elevated paracrine Wnt signaling was correlated with accelerated tumor growth. Using this heterotypic system and a dual lentiviral reporter system that enables simultaneous real-time measurement of both Wnt-responsive cells and bulk tumor cells, we analyzed the outcome of elevated Wnt signaling in patient-derived xenograft (PDX) models. Interestingly, the PDX models exhibited responses not observed in the cell lines analyzed. Exogenous WNT3A promoted tumor growth in one human epidermal growth factor receptor 2-overexpressing PDX line but inhibited growth in a second PDX line obtained from a patient with triple-negative breast cancer. Tumor suppression was associated with squamous differentiation in the latter. Thus, our work suggests that paracrine Wnt signaling can either fuel or repress the growth of human breast cancers depending on yet to be determined aspects of the molecular pathways they express.

Publication types

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

MeSH terms

  • Animals
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / physiopathology*
  • Cell Line, Tumor
  • Cell Proliferation
  • Female
  • Fibroblasts / metabolism
  • Fibroblasts / transplantation
  • Humans
  • Immunohistochemistry
  • Luciferases
  • Luminescent Proteins
  • Mice
  • Mice, SCID
  • Paracrine Communication / physiology*
  • Receptor, ErbB-2 / metabolism
  • Red Fluorescent Protein
  • Time Factors
  • Transplantation, Heterologous
  • Wnt Signaling Pathway / physiology*
  • Wnt3A Protein / metabolism


  • Luminescent Proteins
  • WNT3A protein, human
  • Wnt3A Protein
  • Luciferases
  • ERBB2 protein, human
  • Receptor, ErbB-2