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Oncogene (2013) 32, 36063615 & 2013 Macmillan Publishers Limited All rights reserved 0950-9232/13
http://www.nature.com/ONC
Web End =www.nature.com/onc
ORIGINAL ARTICLE
Specic interactions between Smad proteins and AP-1 components determine TGFb-induced breast cancer cell invasion
A Sundqvist1, A Zieba2,5, E Vasilaki1,5, C Herrera Hidalgo1, O Sderberg2, D Koinuma3, K Miyazono1,3, C-H Heldin1, U Landegren2, P ten Dijke1,4 and H van Dam1,4
Deregulation of the transforming growth factor b (TGFb) signal transduction cascade is functionally linked to cancer. In early phases, TGFb acts as a tumor suppressor by inhibiting tumor cell proliferation, whereas in late phases, it can act as a tumor promoter by stimulating tumor cell invasion and metastasis. Smad transcriptional effectors mediate TGFb responses, but relatively little is known about the Smad-containing complexes that are important for epithelialmesenchymal transition and invasion. In this study, we have tested the hypothesis that specic members of the AP-1 transcription factor family determine TGFb signaling specicity in breast cancer cell invasion. Using a 3D model of collagen-embedded spheroids of MCF10A-MII premalignant human breast cancer cells, we identied the AP-1 transcription factor components c-Jun, JunB, c-Fos and Fra1 as essential factors for TGFb-induced invasion and found that various mesenchymal and invasion-associated TGFb-induced genes are co-regulated by these proteins. In situ proximity ligation assays showed that TGFb signaling not only induces complexes between Smad3 and Smad4 in the nucleus but also complexes between Smad2/3 and Fra1, whereas complexes between Smad3, c-Jun and JunB could already be detected before TGFb stimulation. Finally, chromatin immunoprecipitations showed that c-Jun, JunB and Fra1, but not c-Fos, are required for TGFb-induced binding of Smad2/3 to the mmp-10 and pai-1 promoters. Together these results suggest that in particular formation of Smad2/3-Fra1 complexes may reect activation of the Smad/AP-1-dependent TGFb-induced invasion program.
Oncogene (2013) 32, 36063615; doi:http://dx.doi.org/10.1038/onc.2012.370
Web End =10.1038/onc.2012.370 ; published online 27 August 2012
Keywords: invasion; spheroids; TGFb; AP-1; Smad; PLA
INTRODUCTIONTransforming growth factor b (TGFb) family members are secreted homodimeric proteins that exert a wide range of biological effects on a large variety of cell types, including regulation of proliferation, differentiation, migration and apoptosis. Signaling by TGFb cytokines occurs via ligand-induced heteromeric complex formation of distinct type I and type II serine/threonine kinase receptors, causing the type I receptor to become phosphorylated by the constitutively active...