Deregulation of the transforming growth factor β (TGFβ) signal transduction cascade is functionally linked to cancer. In early phases, TGFβ acts as a tumor suppressor by inhibiting tumor cell... Show moreDeregulation of the transforming growth factor β (TGFβ) signal transduction cascade is functionally linked to cancer. In early phases, TGFβ 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 TGFβ responses, but relatively little is known about the Smad-containing complexes that are important for epithelial-mesenchymal transition and invasion. In this study, we have tested the hypothesis that specific members of the AP-1 transcription factor family determine TGFβ signaling specificity in breast cancer cell invasion. Using a 3D model of collagen-embedded spheroids of MCF10A-MII premalignant human breast cancer cells, we identified the AP-1 transcription factor components c-Jun, JunB, c-Fos and Fra1 as essential factors for TGFβ-induced invasion and found that various mesenchymal and invasion-associated TGFβ-induced genes are co-regulated by these proteins. In situ proximity ligation assays showed that TGFβ 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 TGFβ stimulation. Finally, chromatin immunoprecipitations showed that c-Jun, JunB and Fra1, but not c-Fos, are required for TGFβ-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 reflect activation of the Smad/AP-1-dependent TGFβ-induced invasion program.Oncogene advance online publication, 27 August 2012; doi:10.1038/onc.2012.370. Show less
Wichmann, H.E.; Kuhn, K.A.; Waldenberger, M.; Schmelcher, D.; Schuffenhauer, S.; Meitinger, T.; ... ; Zatloukal, K. 2011
Protein affinity reagents (PARs), most commonly antibodies, are essential reagents for protein characterization in basic research, biotechnology, and diagnostics as well as the fastest growing... Show moreProtein affinity reagents (PARs), most commonly antibodies, are essential reagents for protein characterization in basic research, biotechnology, and diagnostics as well as the fastest growing class of therapeutics. Large numbers of PARs are available commercially; however, their quality is often uncertain. In addition, currently available PARs cover only a fraction of the human proteome, and their cost is prohibitive for proteome scale applications. This situation has triggered several initiatives involving large scale generation and validation of antibodies, for example the Swedish Human Protein Atlas and the German Antibody Factory. Antibodies targeting specific subproteomes are being pursued by members of Human Proteome Organisation (plasma and liver proteome projects) and the United States National Cancer Institute (cancer-associated antigens). ProteomeBinders, a European consortium, aims to set up a resource of consistently quality-controlled protein-binding reagents for the whole human proteome. An ultimate PAR database resource would allow consumers to visit one online warehouse and find all available affinity reagents from different providers together with documentation that facilitates easy comparison of their cost and quality. However, in contrast to, for example, nucleotide databases among which data are synchronized between the major data providers, current PAR producers, quality control centers, and commercial companies all use incompatible formats, hindering data exchange. Here we propose Proteomics Standards Initiative (PSI)-PAR as a global community standard format for the representation and exchange of protein affinity reagent data. The PSI-PAR format is maintained by the Human Proteome Organisation PSI and was developed within the context of ProteomeBinders by building on a mature proteomics standard format, PSI-molecular interaction, which is a widely accepted and established community standard for molecular interaction data. Further information and documentation are available on the PSI-PAR web site. Molecular & Cellular Proteomics 9: 1-10, 2010. Show less
