Open Access Highly Accessed Primary research

Oncogenic transformation of mammary epithelial cells by transforming growth factor beta independent of mammary stem cell regulation

Karen A Dunphy1*, Jae-Hong Seo2, Daniel J Kim1, Amy L Roberts1, Luwei Tao1, James DiRenzo3, Amanda L Balboni3, Giovanna M Crisi4, Mary J Hagen1, Thiruppavai Chandrasekaran1, Kelly J Gauger5, Sallie Smith Schneider5 and D Joseph Jerry15*

Author Affiliations

1 Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01003, USA

2 Korea University, Seoul, Korea

3 Dartmouth Medical School, Hanover, NH 03755, USA

4 Baystate Medical Center, Springfield, MA 01107, USA

5 Pioneer Valley Life Sciences Institute, Springfield, MA 01107, USA

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Cancer Cell International 2013, 13:74  doi:10.1186/1475-2867-13-74

Published: 25 July 2013

Abstract

Background

Transforming growth factor beta (TGFβ) is transiently increased in the mammary gland during involution and by radiation. While TGFβ normally has a tumour suppressor role, prolonged exposure to TGFβ can induce an oncogenic epithelial to mesenchymal transition (EMT) program in permissive cells and initiate the generation of cancer stem cells. Our objective is to mimic the transient exposure to TGFβ during involution to determine the persistent effects on premalignant mammary epithelium.

Method

CDβGeo cells, a transplantable mouse mammary epithelial cell line, were treated in vitro for 14 days with TGFβ (5 ng/ml). The cells were passaged for an additional 14 days in media without TGFβ and then assessed for markers of EMT and transformation.

Results

The 14-day exposure to TGFβ induced EMT and transdifferentiation in vitro that persists after withdrawal of TGFβ. TGFβ-treated cells are highly tumorigenic in vivo, producing invasive solid de-differentiated tumours (100%; latency 6.7 weeks) compared to control (43%; latency 32.7 weeks). Although the TGFβ-treated cells have initiated a persistent EMT program, the stem cell population was unchanged relative to the controls. The gene expression profiles of TGFβ-treated cells demonstrate de-differentiation with decreases in the expression of genes that define luminal, basal and stem cells. Additionally, the gene expression profiles demonstrate increases in markers of EMT, growth factor signalling, TGFβ2 and changes in extra cellular matrix.

Conclusion

This model demonstrates full oncogenic EMT without an increase in stem cells, serving to separate EMT markers from stem cell markers.

Keywords:
Transforming growth factor beta; TGFβ; Epithelial to mesenchymal transition; EMT; Transdifferentiation