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Open Access Research article

Interference with Activator Protein-2 transcription factors leads to induction of apoptosis and an increase in chemo- and radiation-sensitivity in breast cancer cells

Verena Thewes16, Francesca Orso23, Richard Jäger17, Dawid Eckert1, Sabine Schäfer1, Gregor Kirfel4, Stephan Garbe5, Daniela Taverna23 and Hubert Schorle1*

Author Affiliations

1 Department of Developmental Pathology, Institute of Pathology, University of Bonn, Medical School, Germany

2 Molecular Biotechnology Center (MBC) and Department of Oncological Sciences, University of Turin, Via Nizza, 52, 10126 Torino, Italy

3 Center for Complex Systems in Molecular Biology and Medicine, University of Turin, Via Acc. Albertina, 13, 10023 Torino, Italy

4 Department of Cell Biology, University of Bonn, Germany

5 Department of Radiology, University of Bonn, Medical School, Germany

6 Division Molecular Genetics, German Cancer Research Center (DKFZ), Heidelberg, Germany

7 National Centre for Biomedical Engineering Science, National University of Ireland, Galway, Ireland

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BMC Cancer 2010, 10:192  doi:10.1186/1471-2407-10-192

Published: 11 May 2010

Abstract

Background

Activator Protein-2 (AP-2) transcription factors are critically involved in a variety of fundamental cellular processes such as proliferation, differentiation and apoptosis and have also been implicated in carcinogenesis. Expression of the family members AP-2α and AP-2γ is particularly well documented in malignancies of the female breast. Despite increasing evaluation of single AP-2 isoforms in mammary tumors the functional role of concerted expression of multiple AP-2 isoforms in breast cancer remains to be elucidated. AP-2 proteins can form homo- or heterodimers, and there is growing evidence that the net effect whether a cell will proliferate, undergo apoptosis or differentiate is partly dependent on the balance between different AP-2 isoforms.

Methods

We simultaneously interfered with all AP-2 isoforms expressed in ErbB-2-positive murine N202.1A breast cancer cells by conditionally over-expressing a dominant-negative AP-2 mutant.

Results

We show that interference with AP-2 protein function lead to reduced cell number, induced apoptosis and increased chemo- and radiation-sensitivity. Analysis of global gene expression changes upon interference with AP-2 proteins identified 139 modulated genes (90 up-regulated, 49 down-regulated) compared with control cells. Gene Ontology (GO) investigations for these genes revealed Cell Death and Cell Adhesion and Migration as the main functional categories including 25 and 12 genes, respectively. By using information obtained from Ingenuity Pathway Analysis Systems we were able to present proven or potential connections between AP-2 regulated genes involved in cell death and response to chemo- and radiation therapy, (i.e. Ctgf, Nrp1, Tnfaip3, Gsta3) and AP-2 and other main apoptosis players and to create a unique network.

Conclusions

Expression of AP-2 transcription factors in breast cancer cells supports proliferation and contributes to chemo- and radiation-resistance of tumor cells by impairing the ability to induce apoptosis. Therefore, interference with AP-2 function could increase the sensitivity of tumor cells towards therapeutic intervention.