NF-κB is essential for epithelial-mesenchymal transition and metastasis in a model of breast cancer progression
Margit A. Huber, Ninel Azoitei, Bernd Baumann, Stefan Grünert, Andreas Sommer, Hubert Pehamberger, Norbert Kraut, Hartmut Beug, Thomas Wirth
Margit A. Huber, Ninel Azoitei, Bernd Baumann, Stefan Grünert, Andreas Sommer, Hubert Pehamberger, Norbert Kraut, Hartmut Beug, Thomas Wirth
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Article Oncology

NF-κB is essential for epithelial-mesenchymal transition and metastasis in a model of breast cancer progression

Abstract

The transcription factor NF-κB is activated in a range of human cancers and is thought to promote tumorigenesis, mainly due to its ability to protect transformed cells from apoptosis. To investigate the role of NF-κB in epithelial plasticity and metastasis, we utilized a well-characterized in vitro/in vivo model of mammary carcinogenesis that depends on the collaboration of the Ha-Ras oncoprotein and TGF-β. We show here that the IKK-2/IκBα/NF-κB pathway is required for the induction and maintenance of epithelial-mesenchymal transition (EMT). Inhibition of NF-κB signaling prevented EMT in Ras-transformed epithelial cells, while activation of this pathway promoted the transition to a mesenchymal phenotype even in the absence of TGF-β. Furthermore, inhibition of NF-κB activity in mesenchymal cells caused a reversal of EMT, suggesting that NF-κB is essential for both the induction and maintenance of EMT. In line with the importance of EMT for invasion, blocking of NF-κB activity abrogated the metastatic potential of mammary epithelial cells in a mouse model system. Collectively, these data provide evidence of an essential role for NF-κB during distinct steps of breast cancer progression and suggest that the cooperation of Ras- and TGF-β–dependent signaling pathways in late-stage tumorigenesis depends critically on NF-κB activity.

Authors

Margit A. Huber, Ninel Azoitei, Bernd Baumann, Stefan Grünert, Andreas Sommer, Hubert Pehamberger, Norbert Kraut, Hartmut Beug, Thomas Wirth

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Figure 1

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NF-κB activity is induced during EMT. (A) Schematic illustrates the morp...
NF-κB activity is induced during EMT. (A) Schematic illustrates the morphology and epithelial/mesenchymal marker redistribution or expression found in the cell types used in our study. Nontransformed EpH4 mammary epithelial cells were stably transfected with the Ha-Ras oncogene to yield transformed epithelial EpRas cells that undergo EMT upon treatment with TGF-β, resulting in mesenchymal EpRasXT cells further stabilized by an autocrine TGF-β loop. DPP-IV, dipeptidyl peptidase IV; ZO-1, zona occludens 1. (B) EMSAs of whole-cell extracts (6 μg) of exponentially growing EpRas and EpRasXT cells were performed with an NF-κB–specific probe (upper panel) and with an octamer-specific probe (Oct; lower panel) used as a control. Quantified relative DNA-binding levels are indicated below the EMSAs. Similar data were obtained using different protein extract preparations (see also Figure 2A).