The Metastasis-Associated Gene S100A4 Is a Novel Target of β-catenin/T-cell Factor Signaling in Colon Cancer

Abstract

Background & Aims: Activation of the Wnt/β-catenin pathway is frequently observed in colorectal cancers. Our aim was to elucidate the impact of gain-of-function β-catenin on the metastasis-associated gene S100A4 in human colon cancer cell lines and tumors. Methods: We analyzed cell lines heterozygous for gain-of-function and wild-type β-catenin, and variants homozygous for gain- or loss-of-function mutation in β-catenin, for S100A4 expression, cell motility, and in vivo metastasis. β-catenin-mediated S100A4 promoter activation was tested by reporter assays. For human colon carcinomas, S100A4 expression, β-catenin genotype, and metachronous metastasis were correlated. Results: We identified S100A4 as the most regulated gene by gain-of-function β-catenin using a 10K microarray. Cell lines with gain-of-function β-catenin expressed up to 60-fold elevated S100A4 levels, displayed strongly increased migration and invasion in vitro, and induced metastasis in mice. S100A4 small interfering RNA, β-catenin small interfering RNA, or dominant negative T-cell factor (TCF) knocked down S100A4 and blocked biological effects. S100A4 complementary DNA transfection increased migration and invasion. We identified a TCF binding site within the S100A4 promoter and demonstrated the direct binding of heterodimeric β-catenin/TCF complexes. Reporter assays confirmed the β-catenin-induced S100A4 promoter activity. Furthermore, S100A4 mRNA expression was increased in primary colon cancers, which later developed distant metastases, compared to non-metastasizing tumors. Colon tumors heterozygous for gain-of-function β-catenin showed concomitant nuclear β-catenin localization, high S100A4 expression, and metastases. Conclusions: S100A4 is a direct β-catenin/TCF target, induces migration and invasion in vitro and metastasis in vivo, and has value for prognosis of metastasis formation in colon cancer patients. © 2006 AGA Institute.