Research Report 2010 - MDC

protein-protein interactions. We found several sites forserine/threonine and tyrosine phosphorylation; featuresthat predestine MACC1 as a signal transducer.We identified the gene Met as transcriptional target ofMACC1. Following application the hepatocyte growthfactor (HGF), MACC1 translocates from the cytoplasminto the nucleus, binds to the Met promoter, andinduces its transcription. The HGF/Met pathway is particularlyinvolved in colon cancer metastasis. Thus, weidentified MACC1 as a major regulator of this importantcellular metastasis pathway.MACC1 induces migration, invasion, proliferation, colonyformation, and HGF-mediated scattering in cell culture.These functional MACC1 effects were reverted byMACC1- or Met-specific siRNA. Cells with mutantMACC1 protein interaction domains did neither showMACC1-induced cell motility nor proliferation. Subcutaneous,orthotopic or intrasplenic transplantation ofMACC1-expressing colon cancer cells in mice resulted inelevated tumor growth and increased numbers of distantmetastases. MACC1- or Met-specific shRNA led tolowered numbers of metastases in vivo.MACC1 was overexpressed in human colon cancer comparedto normal tissues. Importantly, MACC1 expressionswere significantly higher in those tumors, thatmetachronously metastasized compared to those,which did not metastasize within up to 10 years. MACC1levels predict the probability of metastasis linked tometastasis-free survival. The correct positive or negativeprediction for metastasis was 74% and 80%, respectively.The 5-year-survival was 80% for patients with lowMACC1, compared to 15% for patients with high MACC1expressions. MACC1 in tumor specimens is an independentprognostic indicator for metastasis andmetastasis-free survival. For clinical practice, MACC1 isan important prognostic gene for early identification ofhigh-risk subjects with colorectal cancer, and a promisingnew target for intervention of metastasis formation.Inhibition of colon cancer metastasis by smallmolecules targeting the metastasis progressorS100A4U. Stein, U. Sack, W. Walther, P.M. Schlag. In cooperationwith W. Birchmeier, I. Fichtner (MDC), N. Scudiero, M. Selby(SAIC, Frederick, MD), Robert H. Shoemaker (NationalCancer Institute-Frederick, MD)The calcium-binding protein S100A4 is involved inmetastasis formation and aggressive tumor growth inmany types of cancer. We identified S100A4 as a Wnt/βcatenintarget gene which induces migration, invasionHGF-induced translocation of MACC1 from the cytoplasm into thenucleus in human colon cancer cells, detected by immunofluorescence(bar 50 µm). Stein U, Walther W, Arlt F, Schwabe H, Smith J, Fichtner I,Birchmeier W, Schlag PM. MACC1, a newly identified key regulator ofHGF/Met signaling, predicts colon cancer metastasis. Nature Med15:59-67, 2009and angiogenesis. Hence, its suppression bears potentialfor therapeutic intervention of metastasis.Here we report the identification of small moleculeinhibitors which significantly reduce S100A4 expressionin colorectal carcinoma cells. These inhibitors wereidentified from a high throughput screening of 1,280compounds, employing the S100A4 gene promoterreporter system, and by targeting key molecules of theWnt/β-catenin signaling pathway.Functional assays with selected and validated compoundsrevealed that proliferation rates were diminishedupon treatment while cell viability was only slightlyaffected. More strikingly, migration and invasion ratesof treated cells were significantly decreased by theseinhibitors, but could be rescued by overexpressingS100A4 cDNA. The impact of these small molecules onmetastasis formation in vivo was demonstrated withsmaller and fewer metastases per animal. In summary,our findings present a new strategy to restrict S100A4induced metastasis formation in colon cancer.Clinical application of nonviral gene therapy forlocal treatment of solid tumorsW. Walther, D. Kobelt, R. Siegel, J. Aumann, S. Burock,U. Stein, P. M. Schlag. In cooperation with M. Dietel (Instituteof Pathology, Charité), M. Schleef (PlasmidFactory,Bielefeld), A. Menne (EMS Medical, Nyon, Switzerland)98 Cancer Research