Mariam Grigorian

The metastasis-associated Mts1(S100A4) protein could act as an angiogenic factor

The involvement of Mts1(S100A4), a small Ca2+-binding protein in tumor progression and metastasis had been demonstrated. However, the mechanism by which mts1(S100A4) promoted metastasis had not been identified. Here we demonstrated that Mts1(S100A4) had significant stimulatory effect on the angiogenesis. We detected high incidence of hemangiomas – benign tumors of vascular origin in aged transgenic mice ubiquitously expressing the mts1(S100A4) gene. Furthermore, the serum level of the Mts1(S100A4) protein increased with ageing. Tumors developed in Mts1-transgenic mice revealed an enhanced vascular density. We showed that an oligomeric, but not a dimeric form of the Mts1(S100A4) protein was capable of enhancing the endothelial cell motility in vitro and stimulate the corneal neovascularization in vivo. An oligomeric fraction of the protein was detected in the conditioned media as well as in human serum. The data obtained allowed us to conclude that mts1(S100A4) might induce tumor progression via stimulation of angiogenesis.

Fra-1 Induces Morphological Transformation and Increases In Vitro Invasiveness and Motility of Epithelioid Adenocarcinoma Cells

ABSTRACT Two cell lines originating from a common ancestral tumor, CSML0 and CSML100, were used as a model to study AP-1 transcription factors at different steps of tumor progression. CSML0 cells have an epithelial morphology; they express epithelial but not mesenchymal markers and are invasive neither in vitro nor in vivo. CSML100 possesses all characteristics of a highly progressive carcinoma. These cells do not form tight contacts, are highly invasive in vitro, and are metastatic in vivo. AP-1 activity was considerably higher in CSML100 cells than in CSML0 cells. There was a common predominant Jun component, namely, JunD, detected in both cell lines. We found that the enhanced level of AP-1 in CSML100 cells was due to high expression of Fra-1 and Fra-2 proteins, which were undetectable in CSML0 nuclear extracts. Analysis of the transcription of different AP-1 members in various cell lines derived from tumors of epithelial origin revealed a correlation of fra-1 expression with mesenchymal characteristics of carcinoma cells. Moreover, we show here for the first time that the expression of exogenous Fra-1 in epithelioid cells results in morphological changes that resemble fibroblastoid conversion. Cells acquire an elongated shape and become more motile and invasive in vitro. Morphological alterations were accompanied by transcriptional activation of certain genes whose expression is often induced at late stages of tumor progression. These data suggest a critical role of the Fra-1 protein in the development of epithelial tumors.

Suppression of Tumor Development and Metastasis Formation in Mice Lacking the S100A4(mts1) Gene

The S100A4(mts1) protein stimulates metastatic spread of tumor cells. An elevated expression of S100A4 is associated with poor prognosis in many human cancers. Dynamics of tumor development were studied in S100A4-deficient mice using grafts of CSML100, highly metastatic mouse mammary carcinoma cells. A significant delay in tumor uptake and decreased tumor incidences were observed in S100A4(-/-) mice compared with the wild-type controls. Moreover, tumors developed in S100A4(-/-) mice never metastasize. Immunohistochemical analyses of these tumors revealed reduced vascularity and abnormal distribution of host-derived stroma cells. Coinjection of CSML100 cells with immortalized S100A4(+/+) fibroblasts partially restored the dynamics of tumor development and the ability to form metastasis. These fibroblasts were characterized by an enhanced motility and invasiveness in comparison with S100A4(-/-) fibroblasts, as well as by the ability to release S100A4 into the tumor environment. Taken together, our results point to a determinative role of host-derived stroma cells expressing S100A4 in tumor progression and metastasis.

Extracellular S100A4(mts1) stimulates invasive growth of mouse endothelial cells and modulates MMP-13 matrix metalloproteinase activity

S100A4(mts1) protein expression has been strongly associated with metastatic tumor progression. It has been suggested as a prognostic marker for a number of human cancers. It is proposed that extracellular S100A4 accelerates cancer progression by stimulating the motility of endothelial cells, thereby promoting angiogenesis. Here we show that in 3D culture mouse endothelial cells (SVEC 4-10) respond to recombinant S100A4 by stimulating invasive growth of capillary-like structures. The outgrowth is not dependent on the stimulation of cell proliferation, but rather correlates with the transcriptional modulation of genes involved in the proteolytic degradation of extracellular matrix (ECM). Treatment of SVEC 4-10 with the S100A4 protein leads to the transcriptional activation of collagenase 3 (MMP-13) mRNA followed by subsequent release of the protein from the cells. β-Casein zymography demonstrates enhancement of proteolytic activity associated with MMP-13. This observation indicates that extracellular S100A4 stimulates the production of ECM degrading enzymes from endothelial cells, thereby stimulating the remodeling of ECM. This could explain the angiogenic and metastasis-stimulating activity of S100A4(mts1).

Liprin β1, a Member of the Family of LAR Transmembrane Tyrosine Phosphatase-interacting Proteins, Is a New Target for the Metastasis-associated Protein S100A4 (Mts1)

Metastasis-associated protein S100A4 (Mts1) induces invasiveness of primary tumors and promotes metastasis. S100A4 belongs to the family of small calcium-binding S100 proteins that are involved in different cellular processes as transducers of calcium signal. S100A4 modulates properties of tumor cells via interaction with its intracellular targets, heavy chain of non-muscle myosin and p53. Here we report identification of a new molecular target of the S100A4 protein, liprin β1. Liprin β1 belongs to the family of leukocyte common antigen-related (LAR) transmembrane tyrosine phosphatase-interacting proteins that may regulate LAR protein properties via interaction with another member of the family, liprin α1. We showed by the immunoprecipitation analysis that S100A4 interacts specifically with liprin β1 in vivo.Immunofluorescence staining demonstrated the co-localization of S100A4 and liprin β1 in the cytoplasm and particularly at the protrusion sites of the plasma membrane. We mapped the S100A4 binding site at the C terminus of the liprin β1 molecule between amino acid residues 938 and 1005. The S100A4-binding region contains two putative phosphorylation sites by protein kinase C and protein kinase CK2. S100A4-liprin β1 interaction resulted in the inhibition of liprin β1 phosphorylation by both kinases in vitro.

The mts1 gene and control of tumor metastasis.

The main stream of biology today is the analysis of the molecular mechanisms of major biological phenomena through studies of the genes governing these processes and their protein products. An example is the problem of tumor metastasis which is extremely important both theoretically and practically. Here we describe the data obtained on the detection, cloning, structure and transcription control of the mts1 gene, that encodes metastasin 1, a protein which seems to play an important role in the control of metastasis in mouse tumors. In particular, the experiments on tumor cell transfection with constructions containing either a sense or antisense mts1 sequence under a strong promoter/enhancer element show the direct dependence of the metastatic phenotype on the expression of the mts1 gene at least in some systems. Gene mts1 encodes a protein belonging to the family of Ca(2+)-binding proteins and may be involved in the control of cell motility in different types of cells, such as macrophages and T-lymphocytes. The relationship between mts1 and other genes up- and down-regulated in metastatic cells is discussed.

Cancer predisposition in mice deficient for the metastasis-associated Mts1(S100A4) gene

Metastasis-promoting Mts1(S100A4) protein belongs to the S100 family of Ca2+-binding proteins. A mouse strain with a germ-line inactivation of the S100A4 gene was generated. The mice were viable and did not display developmental abnormalities in the postnatal period. However, an abnormal sex ratio was observed in the litters with the S100A4−/− genotype, raising the possibility of a certain level of embryonic lethality in this strain. In all, 10% of 10–14-month-old S100A4-null animals developed tumors. This is a characteristic feature of mouse strains with inactivated tumor suppressor genes. Spontaneous tumors of S100A4−/− mice were p53 positive. Recently, we have shown that S100A4 interacts with p53 tumor suppressor protein and induces apoptosis. We proposed that impairment of this interaction could affect the apoptosis-promoting function of p53 that is involved in its tumor suppressor activity. The frequency of apoptosis in the spleen of S100A4−/− animals after whole-body γ-irradiation was reduced compared to the wild-type animals. The same was true for the transcriptional activation of the p53 target genes – waf/p21/cip1 and bax. Taken together, these observations indicate that spontaneous tumors in S100A4−/− mice are a result of functional destabilization of p53 tumor suppressor gene.

Lung Metastasis Fails in MMTV-PyMT Oncomice Lacking S100A4 Due to a T-Cell Deficiency in Primary Tumors

Interactions between tumor and stroma cells are essential for the progression of cancer from its initial growth at a primary site to its metastasis to distant organs. The metastasis-stimulating protein S100A4 exerts its function as a stroma cell-derived factor. Genetic depletion of S100A4 significantly reduced the metastatic burden in lungs of PyMT-induced mammary tumors. In S100A4(+/+) PyMT mice, massive leukocyte infiltration at the site of the growing tumor at the stage of malignant transition was associated with increased concentration of extracellular S100A4 in the tumor microenvironment. In contrast, in S100A4(-/-) PyMT tumors, a significant suppression of T-cell infiltration was documented at the transition period. In vitro, the S100A4 protein mediated the attraction of T cells. Moreover, S100A4(+/+), but not S100A4(-/-), fibroblasts stimulated the invasion of T lymphocytes into fibroblast monolayers. In vivo, the presence of S100A4(+/+), but not S100A4(-/-), fibroblasts significantly stimulated the attraction of T lymphocytes to the site of the growing tumor. Increased levels of T cells were also observed in the premetastatic lungs of tumor-bearing mice primed to metastasize by S100A4(+/+) fibroblasts. Treatment of T cells with the S100A4 protein stimulated production of cytokines, particularly granulocyte colony-stimulating factor and eotaxin-2. The same cytokines were detected in the fluid of S100A4(+/+) PyMT tumors at the transition period. We suggest that release of S100A4 in the primary tumor stimulates infiltration of T cells and activates secretion of cytokines, thus triggering sequential events that fuel tumor cells to metastasize. Similar processes could occur in the premetastatic lungs, facilitating generation of inflammatory milieu favorable for metastasis formation.

Epidermal growth factor receptor ligands as new extracellular targets for the metastasis-promoting S100A4 protein.

The function of S100A4, a member of the calcium‐binding S100 protein family, has been associated with tumor invasion and metastasis. Although an essential pro‐metastatic role of extracellular S100A4 in tumor progression has been demonstrated, the identification of the precise underlying mechanisms and protein partners (receptors) has remained elusive. To identify putative targets for extracellular S100A4, we screened a phage display peptide library using S100A4 as bait. We identified three independent peptide motifs with varying affinities for the S100A4 protein. Sequence analyses indicated that the most abundant peptide mimicked the F/YCC motif present in the epidermal growth factor domain of ErbB receptor ligands. S100A4 selectively interacted with a number of epidermal growth factor receptor (EGFR) ligands, demonstrating highest affinity for amphiregulin. Importantly, we found that S100A4 stimulated EGFR/ErbB2 receptor signaling and enhanced the amphiregulin‐mediated proliferation of mouse embryonic fibroblasts. S100A4‐neutralizing antibodies, as well as EGFR‐ and ErbB2 receptor‐specific tyrosine kinase inhibitors, blocked these effects. The present results suggest that extracellular S100A4 regulates tumor progression by interacting with EGFR ligands, thereby enhancing EGFR/ErbB2 receptor signaling and cell proliferation.

Transcriptional regulation of the mts1 gene in human lymphoma cells: the role of DNA-methylation

The transcription of the mts1 gene putatively involved in the control of tumor metastasis was studied in three human lymphoma cell lines: MOLT-4, CEM and Jurkat. The level of the mts1 gene transcription is high in MOLT-4 cells, lower in CEM cells and hardly detectable in Jurkat cells. This correlates with the hypomethylation of DNA in the first exon and the first intron of the mts1 gene in the analyzed culture cells. This area was also found to be undermethylated in human peripheral blood cells--macrophages, neutrophils and lymphocytes where the mts 1 gene is highly expressed. 5-Azadeoxycytidine (AzadC)--an inhibitor of the eukaryotic DNA-methylase--significantly induces the expression of the mts1 gene in CEM and Jurkat cells and has little effect on mts1 gene transcription in MOLT-4 cells. The drug does not influence mts1 transcription in cultivated peripheral blood lymphocytes. These data indicate the possible involvement of the methylation of the first exon/first intron sequences in the transcriptional repression of the mts1 gene. The finding of two DNAaseI hypersensitivity sites (DHSs) mapped in the first intron of the mts1 gene supports this suggestion.