of the Max - MDC

Figure 1. S100A4 is a newly identified target gene of the β-catenin/TCF signaling
pathway.
β-Catenin/TCF signaling controls the expression of the metastasis-promoting gene
S100A4. S100A4 acts intracellularly via transcriptional regulation of target genes, and
by protein interaction with binding partners. Functions of extracellular S100A4 are
mediated via transmembrane receptors.
Figure 2. Clinical application of nonviral jet-injection.
Jet-injection of LacZ-expressing plasmid-DNA into skin metastases of a melanoma
patient (A) and injection site shortly after application (B). RT-PCR analysis of LacZmRNA
expression in the tumor (C), verified by Western-blot analysis of LacZ-protein (D)
Detection of LacZ-protein distribution within the tumor tissue by X-gal staining (E; as
indicated by arrows).
terns in human primary tumors, metastases, and mucosa of
colon cancer patients. We cloned the full-length cDNA
sequence of this novel gene, referred to as MACC1. The
encoded putative protein harbors domains for protein-protein-interaction
and potential tyrosine phosphorylation
sites. MACC1 expressions measured in primary colon tumors
were found to be significantly higher in those cancers, that
metachronously developed distant metastases compared to
those tumors, which did not metastasize. Thus, MACC1 levels
predict the probability to develop distant metastases
linked to metastasis-free survival. Moreover, we identified
an autoregulatory system of HGF-induced nuclear translocation
of MACC1 that transcriptionally controls Met expression,
thereby initializing and/or intensifying HGF/Met signaling
downstream events. MACC1 induces proliferation,
motility, and HGF-induced scattering in colon cancer cells.
Transduction of both, MACC1 and Met siRNA, reverted these
effects. Following subcutaneous, orthotopic, and intrasplenal
transplantation of MACC1-expressing tumor cells in
mice, enhanced tumor growth and liver metastases were
found. MACC1 mutants lacking protein-protein interaction
domains lost their biological functions in vitro and in vivo.
Activation of the Wnt/β-catenin pathway is frequently
observed in colorectal cancers, and mutations of the
β-catenin gene were described as early and critical steps
in tumor progression. We analyzed cell lines heterozygous
or homozygous for gain-of-function and/or wildtype
β-catenin. 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, and displayed strongly
increased cell migration and invasion. Transduction of both,
S100A4 and β-catenin siRNA, knocked down these effects.
We demonstrated the direct binding of heterodimeric β-
catenin/TCF complexes to the S100A4 promoter. Reporter
assays confirmed the β-catenin-controlled S100A4 promoter
activity. Furthermore, S100A4 expression was increased
in human primary colon cancers, which later developed distant
metastases, compared to tumors which did not metastasize.
Colon tumors heterozygous for gain-of-function β-
catenin showed concomitant nuclear β-catenin localization,
high S100A4 expression, and distant metastases formation.
Our results relate two pathways with important roles in tumor
progression and metastasis, the β-catenin/TCF signaling pathway
and S100A4, that controls motility and invasiveness.
86 Cancer Research