Interference with activator protein-2 transcription factors leads to induction of apoptosis and an increase in chemo- and radiation-sensitivity in breast cancer cells.
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-2alpha and AP-2gamma 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.
Thewes
Verena
V
Department of Developmental Pathology, Institute of Pathology, University of Bonn, Medical School, Germany.
Orso
Francesca
F
Jäger
Richard
R
Eckert
Dawid
D
Schäfer
Sabine
S
Kirfel
Gregor
G
Garbe
Stephan
S
Taverna
Daniela
D
Schorle
Hubert
H
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D030541:Databases, Genetic; D019008:Drug Resistance, Neoplasm; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic; D053263:Gene Regulatory Networks; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D020033:Protein Isoforms; D011836:Radiation Tolerance; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D050656:Transcription Factor AP-2 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D000970:Antineoplastic Agents; D020033:Protein Isoforms; D018719:Erb-b2 Receptor Tyrosine Kinases; D050656:Transcription Factor AP-2; C524056:Erbb2 protein, mouse
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