Functional significance of metastasis-inducing S100A4(Mts1) in tumor-stroma interplay

Critical role for the advanced glycation end-products receptor in pulmonary arterial hypertension etiology

Background

Pulmonary arterial hypertension (PAH) is a vasculopathy characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation and suppressed apoptosis. This results in both increase in pulmonary arterial pressure and pulmonary vascular resistance. Recent studies have shown the implication of the signal transducer and activator of transcription 3 (STAT3)/bone morphogenetic protein receptor 2 (BMPR2)/peroxisome proliferator‐activated receptor gamma (PPARγ) in PAH. STAT3 activation induces BMPR2 downregulation, decreasing PPARγ, which both contribute to the proproliferative and antiapoptotic phenotype seen in PAH. In chondrocytes, activation of this axis has been attributed to the advanced glycation end‐products receptor (RAGE). As RAGE is one of the most upregulated proteins in PAH patients' lungs and a strong STAT3 activator, we hypothesized that by activating STAT3, RAGE induces BMPR2 and PPARγ downregulation, promoting PAH‐PASMC proliferation and resistance to apoptosis.

Methods and Results

In vitro, using PASMCs isolated from PAH and healthy patients, we demonstrated that RAGE is overexpressed in PAH‐PASMC (6‐fold increase), thus inducing STAT3 activation (from 10% to 40% positive cells) and decrease in BMPR2 and PPARγ levels (>50% decrease). Pharmacological activation of RAGE in control cells by S100A4 recapitulates the PAH phenotype (increasing RAGE by 6‐fold, thus activating STAT3 and decreasing BMPR2 and PPARγ). In both conditions, this phenotype is totally reversed on RAGE inhibition. In vivo, RAGE inhibition in monocrotaline‐ and Sugen‐induced PAH demonstrates therapeutic effects characterized by PA pressure and right ventricular hypertrophy decrease (control rats have an mPAP around 15 mm Hg, PAH rats have an mPAP >40 mm Hg, and with RAGE inhibition, mPAP decreases to 20 and 28 mm Hg, respectively, in MCT and Sugen models). This was associated with significant improvement in lung perfusion and vascular remodeling due to decrease in proliferation (>50% decrease) and BMPR2/PPARγ axis restoration (increased by ≥60%).

Conclusion

We have demonstrated the implications of RAGE in PAH etiology. Thus, RAGE constitutes a new attractive therapeutic target for PAH.

An efficient expression and purification strategy for the production of S100 proteins in Escherichia coli

S100 proteins belong to a family of small, acidic, EF-hand Ca ( 2+) -binding proteins and have been found to exert both intracellular and extracellular functions in regulation of Ca ( 2+) homeostasis, cytoskeletal dynamics, cell cycle, motility and differentiation. As a result, they have been widely investigated for their association with diseases, such as, neurological diseases, cardiomyopathy, neoplasias and inflammatory diseases. To facilitate further studies of S100 proteins, we reported a simple and efficient method for the expression and purification of human S100A4 and S100A11 proteins in Escherichia coli. Since S100 proteins share many common physical and chemical characteristics, we expect that this approach can be extended to the production of most S100 proteins.

Building the niche: the role of the S100 proteins in metastatic growth

Communication between cancer cells and stromal cells, often mediated by extracellular molecules in the tumor microenvironment, plays a central role in tumorigenesis and metastasis. The establishment of a pro-inflammatory milieu is increasingly recognized as an important consequence of these interactions. The family of S100 Ca2+-binding proteins has been implicated in many aspects of the interaction between cancer cells and stromal cells, and contributes to the formation of an inflammatory tumor microenvironment. Focusing on S100A4, S100A8 and S100A9, in this review we discuss the role these proteins play in primary tumors and in the development of metastases, in particular during the formation of pre-metastatic niches.

S100A4 expression in xenograft tumors of human carcinoma cell lines is induced by the tumor microenvironment

Increased expression of the invasion- and metastasis-associated protein S100A4 is found in many types of cancer, but the regulation of S100A4 expression is poorly understood. The microenvironment surrounding tumors has a significant effect on tumor progression, and in the present study, we investigated the role of the microenvironment in the expression of S100A4. Tumors of three different human carcinoma cell lines were established in the tongue or skin of mice, and S100A4 expression was assessed by quantitative RT-PCR, Western blotting, and immunohistochemical analysis in tumors and stromal tissue and in cancer cells grown in vitro. Tongue tumors of the oral squamous cell carcinoma cell line HSC-4 showed a pronounced increase in S100A4 expression during tumor growth, whereas only a minor increase was detected in skin tumors of the same cell line. The S100A4 expression correlated with the methylation status of cytosine-guanine sites in the first intron of the gene. For all cell lines, S100A4 expression in the tumor stroma was related to the presence of inflammatory cells rather than to the level of S100A4 in the tumor cells.

Osteopontin--an important downstream effector of S100A4-mediated invasion and metastasis

Substantial evidence has linked the small calcium-binding protein S100A4 to metastatic progression. S100A4-mediated effects include stimulation of angiogenesis, regulation of cell death and increased cell motility and invasion, but the exact molecular mechanisms by which the protein exerts these effects are incompletely elucidated. In the present study, we demonstrate that S100A4 induces NF-κB-dependent expression and secretion of osteopontin (OPN) in a selection of osteosarcoma cell lines. OPN is, as S100A4, known to result in a variety of cellular effects potentially leading to increased angiogenesis and metastasis, and several of the activated signaling pathways are common for the two proteins. In our study, extracellular S100A4 was found to upregulate enzymes of the plasminogen activator system and matrix metalloproteinase (MMP) family, especially urokinase plasminogen activator and MMP-13. Furthermore, increased motility and invasion was observed in vitro as a result of S100A4 treatment. OPN expression was inhibited by the use of siRNA molecules, and a partial blocking of S100A4-induced effects on protease expression and invasive capacity was detected. In conclusion, our results suggest regulation of OPN as a downstream molecular mechanism of S100A4 signaling. This novel finding adds more information to how S100A4 mediates tumor development and metastatic progression. The observation of a link between S100A4 and OPN, and also identification of common downstream effect molecules, highlights them, their receptors or downstream proteins, as targets for therapeutic approaches.

Frequent S100A4 Expression with Unique Splicing Pattern in Gastric Cancers: A Hypomethylation Event Paralleled with E-cadherin Reduction and Wnt Activation

S100A4 promotes cancer metastasis, but its overall status and splicing manner during gastrocarcinogenesis remains less known. We therefore examined S100A4 frequencies, splicing pattern(s) and the underlying reason(s) for S100A4 expression in gastric cancers. Immunohistochemistry revealed frequent S100A4 expression in intestinal gastric cancers (37/45; 82%) and diffuse gastric cancers (12/20; 60%), but uncommon in noncancerous epithelia (0/12), chronic gastritis (2/24; 8%), and intestinal metaplasia (3/15; 20%). Of 65 primary tumors, 18 were found with focal S100A4 expression, while their LN metastases showed homogenous distribution. S100A4-oriented reverse transcription-polymerase chain reaction yielded a transcript containing exons 1, 3, and 4 (AS1) in 20% of noncancerous, 84% premalignant, and 92% tumor tissues and a transcript harboring exons 1 to 4 (AS2) in 65% of gastric cancers (GCs), 26% premalignant but none in noncancerous tissues. Further analyses found AS1 expression in stromal but not epithelial cells of premalignant tissues, absence of AS2 in endoscopic inflammatory mucosa, and the coexistence of AS1/AS2 in the cultured fibroblasts. Methylation DNA sequencing revealed hypermethylation of four critical CpG sites within S100A4 intron first among S100A4-negative gastric tissues and hypomethylation in S100A4-expressing GC tissues/cell lines. E-cadherin reduction and Wnt activation were common in gastric cancers, which were closely correlated but unnecessarily overlapped with S100A4 expression. Our findings suggest that S100A4 expression is closely related with GC formation, which, as a hypomethylation event, is accompanied with E-cadherin reduction and Wnt activation. The preferential S100A4 AS2 expression in GC cells would have potential values in GC surveillance and prognostic assessment.

Potential role for S100A4 in the disruption of the blood-brain barrier in collagen-induced arthritic mice, an animal model of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease associated with chronic inflammation of the joints. RA has been shown to increase the morbidity of and mortality due to cardiovascular and cerebrovascular diseases. We recently reported that cerebrovascular permeability was increased in mice with collagen-induced arthritis (CIA), an animal model of RA. S100A4, a member of the S100 family, is up-regulated in synovial fluid and plasma from RA patients. This study was aimed at evaluating a role of S100A4 in the mediation of blood-brain barrier (BBB) dysfunction in CIA mice. CIA was induced by immunization with type II collagen in mice. Cerebrovascular permeability was assessed by measurement of sodium fluorescein (Na-F) levels in the brains of control and CIA mice. Serum S100A4 concentrations in control and CIA mice were measured by enzyme-linked immunosorbent assays (ELISA). Accumulation of Na-F in the brain and serum levels of S100A4 were increased in CIA mice. Increased S100A4 levels in the serum are closely correlated with hyperpermeability of the cerebrovascular endothelium to Na-F. We investigated whether S100A4 induces BBB dysfunction using mouse brain capillary endothelial cells (MBECs). S100A4 decreased the transendothelial electrical resistance and increased Na-F permeability in the MBECs. S100A4 reduced the expression of occludin, a tight junction protein, and stimulated p53 expression in MBECs. These findings suggest that S100A4 increases paracellular permeability of MBECs by decreasing expression levels of occludin, at least in part, via p53. The present study highlights a potential role for S100A4 in BBB dysfunction underlying cerebrovascular diseases in patients with RA.

S100A14 stimulates cell proliferation and induces cell apoptosis at different concentrations via receptor for advanced glycation end products (RAGE)

S100A14 is an EF-hand containing calcium-binding protein of the S100 protein family that exerts its biological effects on different types of cells. However, exact extracellular roles of S100A14 have not been clarified yet. Here we investigated the effects of S100A14 on esophageal squamous cell carcinoma (ESCC) cell lines. Results demonstrated that low doses of extracellular S100A14 stimulate cell proliferation and promote survival in KYSE180 cells through activating ERK1/2 MAPK and NF-κB signaling pathways. Immunoprecipitation assay showed that S100A14 binds to receptor for advanced glycation end products (RAGE) in KYSE180 cells. Inhibition of RAGE signaling by different approaches including siRNA for RAGE, overexpression of a dominant-negative RAGE construct or a RAGE antagonist peptide (AmphP) significantly blocked S100A14-induced effects, suggesting that S100A14 acts via RAGE ligation. Furthermore, mutation of the N-EF hand of S100A14 (E39A, E45A) virtually reduced 10 µg/ml S100A14-induced cell proliferation and ERK1/2 activation. However, high dose (80 µg/ml) of S100A14 causes apoptosis via the mitochondrial pathway with activation of caspase-3, caspase-9, and poly(ADP-ribose) polymerase. High dose S100A14 induces cell apoptosis is partially in a RAGE-dependent manner. This is the first study to demonstrate that S100A14 binds to RAGE and stimulates RAGE-dependent signaling cascades, promoting cell proliferation or triggering cell apoptosis at different doses.

S100A4 protects gastric cancer cells from anoikis through regulation of αv and α5 integrin

Detachment from the extracellular matrix induces a form of programmed cell death termed anoikis. Resistance to anoikis permits cancer cells to survive in systemic circulation and facilitates their metastasis to distant organs. It is well known that S100A4 is overexpressed in many tumors and involved in tumor metastasis, but the mechanisms of the metastasis-promoting function of S100A4 are not fully understood. We hypothesized that S100A4 might play a role in anoikis of gastric cancer cells and further affects their metastasis. To test this hypothesis, we changed the expression of S100A4 by means of RNA interference or experimental overexpression and investigated the effect on anoikis. We found that knockdown of S100A4 by RNA interference led to significantly increased anoikis, whereas overexpression of S100A4 resulted in inhibition of anoikis. Furthermore, we provide evidence that inhibition of S100A4 resulted in the downregulation of α5 and αv integrin expression. These findings suggest that S100A4 protects gastric cancer cells from anoikis by regulation of αv and α5 integrin expression, which sheds a novel light for the role of S100A4 in cancer metastasis.

Human mammary fibroblasts stimulate invasion of breast cancer cells in a three-dimensional culture and increase stroma development in mouse xenografts

INTRODUCTION

Tumour phenotype is regulated in a complex fashion as a result of interactions between malignant cells and the tumour stroma. Fibroblasts are the most abundant and perhaps most active part of the tumour stroma. A better understanding of the changes that occur in fibroblasts in response to the presence of malignant cells may lead to the development of new strategies for cancer treatment. We explored the effects of fibroblasts on the growth and invasion of mammary carcinoma tumour cells in vitro and in vivo.

METHODS

In order to analyse secreted factors that affect invasive abilities of breast cancer cells we co-cultured human mammary fibroblasts (HMF3s) and cancer cells (MCF7S1) in three-dimensional (3D) growth conditions devoid of heterogeneous cell-cell contact. To study the possible influence of fibroblasts on MCF7S1 cancer cell growth in vivo we co-injected HMF3s and MCF7S1 cells in Balb/c nu/nu mice.

RESULTS

In 3D co-culture both HMF3s and MCF7S1 cells demonstrated enhanced invasion into a Matrigel matrix. This was correlated with enhanced expression of the metastasis promoting S100A4 protein in fibroblasts, stimulation of the matrix metalloproteinase (MMP)-2 activity, and enhanced secretion of a range of different cytokines. Orthotopic injection of oestrogen-dependent MCF7S1 cancer cells together with fibroblasts showed stimulation of tumour growth in mice without an external oestrogen supply. The resulting tumours were characterized by increased development of extracellular matrix, as well as an increase of murine S100A4 concentration and activity of MMP-2 in the tumour interstitial fluid.

CONCLUSION

Stimulation of the invasive phenotype of tumour cells in 3D co-cultures with fibroblasts could be correlated with increased production of S100A4 and MMP-2. We propose that enhanced development of mouse host-derived tumour stroma in a MCF7S1 co-injection xenograft model leads to oestrogen independency and is triggered by the initial presence of human fibroblasts.

Overexpression of S100A4 in human cancer cell lines resistant to methotrexate

Background

Methotrexate is a chemotherapeutic drug that is used in therapy of a wide variety of cancers. The efficiency of treatment with this drug is compromised by the appearance of resistance. Combination treatments of MTX with other drugs that could modulate the expression of genes involved in MTX resistance would be an adequate strategy to prevent the development of this resistance.

Methods

The differential expression pattern between sensitive and MTX-resistant cells was determined by whole human genome microarrays and analyzed with the GeneSpring GX software package. A global comparison of all the studied cell lines was performed in order to find out differentially expressed genes in the majority of the MTX-resistant cells. S100A4 mRNA and protein levels were determined by RT-Real-Time PCR and Western blot, respectively. Functional validations of S100A4 were performed either by transfection of an expression vector for S100A4 or a siRNA against S100A4. Transfection of an expression vector encoding for β-catenin was used to inquire for the possible transcriptional regulation of S100A4 through the Wnt pathway.

Results

S100A4 is overexpressed in five out of the seven MTX-resistant cell lines studied. Ectopic overexpression of this gene in HT29 sensitive cells augmented both the intracellular and extracellular S100A4 protein levels and caused desensitization toward MTX. siRNA against S100A4 decreased the levels of this protein and caused a chemosensitization in combined treatments with MTX. β-catenin overexpression experiments support a possible involvement of the Wnt signaling pathway in S100A4 transcriptional regulation in HT29 cells.

Conclusions

S100A4 is overexpressed in many MTX-resistant cells. S100A4 overexpression decreases the sensitivity of HT29 colon cancer human cells to MTX, whereas its knockdown causes chemosensitization toward MTX. Both approaches highlight a role for S100A4 in MTX resistance.

Signal transduction mechanisms involved in S100A4-induced activation of the transcription factor NF-kappaB

BACKGROUND

The metastasis-promoting protein S100A4 activates the transcription factor NF-kappaB through the classical NF-kappaB activation pathway. The upstream signal transduction mechanisms leading to increased NF-kappaB activity are, however, incompletely characterized.

METHODS

The human osteosarcoma cell line II-11b was stimulated with recombinant S100A4 in the presence or absence of inhibitors of common signal transduction pathways, and NF-kappaB activity was examined using a luciferase-based reporter assay and phosphorylation of IkappaBalpha. mRNA expression was analyzed by real-time RT-PCR, protein expression was examined by Western blotting and IKK activity was measured using an in vitro kinase assay. The role of upstream kinases and the cell surface receptor RAGE was investigated by overexpression of dominant negative proteins and by siRNA transfection.

RESULTS

The Ser/Thr kinase inhibitors H-7 and staurosporine inhibited S100A4-induced IkappaBalpha phosphorylation and subsequent NF-kappaB activation. The protein tyrosine kinase inhibitor genistein and the phospholipase C inhibitor compound 48/80 had a partial inhibitory effect on IkappaBalpha phosphorylation, whereas inhibitors of protein kinase C, G-protein coupled receptors and PI 3-kinases had no effect on the level of phosphorylation. Interestingly, S100A4 treatment induced activating phosphorylations of IKKalpha/beta, but neither H-7 nor staurosporine was able to significantly inhibit IKK activation. Dominant negative MEKK1 or NIK did not inhibit S100A4-induced NF-kappaB activity, and S100A4 stimulation did not influence AKT phosphorylation. Furthermore, diminished expression of the putative S100 protein receptor RAGE did not affect the observed phosphorylation of IkappaBalpha.

CONCLUSIONS

S100A4 activates NF-kappaB by inducing phosphorylation of IKKalpha/beta, leading to increased IkappaBalpha phosphorylation. The Ser/Thr kinase inhibitors H-7 and staurosporine attenuated S100A4-induced NF-kappaB activation and inhibited IKK-mediated phosphorylation of IkappaBalpha. S100A4-induced NF-kappaB activation was independent of the putative S100 protein receptor RAGE and the Ser/Thr kinases MEKK1, NIK and AKT. These findings lead to increased understanding of S100A4 signaling, which may contribute to the identification of novel targets for anti-metastatic therapy.

Subcellular distribution of S100A4 and its transcriptional regulation under hypoxic conditions in gastric cancer cell line BGC823

It is well known that S100A4 is overexpressed in many tumors and involved in tumor invasion and metastasis. But the regulation of it is ill understood. We previously found that hypoxia mimicking cobalt chloride (CoCl(2)) enhanced the mRNA and protein expressions of the S100A4 gene in the gastric cancer cell line BGC823. In this study we found that S100A4 also displayed increased expression in BGC823 cells after exposure to real hypoxia (2.5% O(2)) as that by CoCl(2) treatment. Moreover, S100A4 protein showed different subcellular distribution under real hypoxia compared with that by CoCl(2) treatment or in normoxic conditions. To investigate the underlying molecular mechanism by which hypoxia regulates the expression of S100A4, we analyzed the regulatory sequences of the genes by bioinformatics and found a putative hypoxia responsive element (HRE) motif in the first intron of S1004. Furthermore, luciferase reporter assay showed that it is responsive to hypoxia. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays demonstrated that hypoxia-inducible factor 1 (HIF-1) binds to the functional HRE in vitro and in vivo. The results provide evidence that S100A4 is a hypoxia-inducible gene, whose transcription is stimulated at least partly through the interaction of HIF-1 and HRE located at +329 to +334 of S100A4.

Metastasis-inducing S100A4 and RANTES cooperate in promoting tumor progression in mice

BACKGROUND

The tumor microenvironment has been described as a critical milieu determining tumor growth and metastases. A pivotal role of metastasis-inducing S100A4 in the development of tumor stroma has been proven in animal models and verified in human breast cancer biopsies. Expression and release of S100A4 has been shown in various types of stroma composing cells, including fibroblasts and immune cells. However, the events implicated in upstream and downstream pathways regulating the activity of the extracellular S100A4 protein in the tumor milieu remain unsolved.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the interplay between the tumor cell-derived cytokine regulated-upon-activation, normal T-cell expressed and secreted (RANTES; CCL5) and S100A4 which were shown to be critical factors in tumor progression. We found that RANTES stimulates the externalization of S100A4 via microparticle shedding from the plasma membrane of tumor and stroma cells. Conversely, the released S100A4 protein induces the upregulation of fibronectin (FN) in fibroblasts and a number of cytokines, including RANTES in tumor cells as well as stimulates cell motility in a wound healing assay. Importantly, using wild type and S100A4-deficient mouse models, we demonstrated a substantial influence of tumor cell-derived RANTES on S100A4 release into blood circulation which ultimately increases the metastatic burden in mice.

CONCLUSIONS/SIGNIFICANCE

Altogether, the data presented strongly validate the pro-metastatic function of S100A4 in the tumor microenvironment and define how the tumor cell-derived cytokine RANTES acts as a critical regulator of S100A4-dependent tumor cell dissemination. Additionally, for the first time we demonstrated the mechanism of S100A4 release associated with plasma membrane microparticle shedding from various cells types.

Synchronous collision malignant melanoma and adenocarcinoma of the rectum

"Collision tumors" consist of two independent but coexisting tumors. This uncommon situation might be easily mistaken for a composite tumor where one histogenetic event originates from two apparently distinct neoplasms. Colorectal collisions are particularly unusual; here, we report the exceedingly rare case of a 61-year-old man with malignant melanoma and adenocarcinoma colliding in the rectum. Collision tumors have an idiopathic pathophysiology and in fact "accidental meeting" is accepted by many authors. This article discusses the concepts about cancer development, which are overlooked by this hypothesis, another theory to explain that this rare occurrence involves microenvironment changes.

COX-2 and prostaglandin EP3/EP4 signaling regulate the tumor stromal proangiogenic microenvironment via CXCL12-CXCR4 chemokine systems

Bone marrow (BM)-derived hematopoietic cells, which are major components of tumor stroma, determine the tumor microenvironment and regulate tumor phenotypes. Cyclooxygenase (COX)-2 and endogenous prostaglandins are important determinants for tumor growth and tumor-associated angiogenesis; however, their contributions to stromal formation and angiogenesis remain unclear. In this study, we observed that Lewis lung carcinoma cells implanted in wild-type mice formed a tumor mass with extensive stromal formation that was markedly suppressed by COX-2 inhibition, which reduced the recruitment of BM cells. Notably, COX-2 inhibition attenuated CXCL12/CXCR4 expression as well as expression of several other chemokines. Indeed, in a Matrigel model, prostaglandin (PG) E2 enhanced stromal formation and CXCL12/CXCR4 expression. In addition, a COX-2 inhibitor suppressed stromal formation and reduced expression of CXCL12/CXCR4 and a fibroblast marker (S100A4) in a micropore chamber model. Moreover, stromal formation after tumor implantation was suppressed in EP3-/- mice and EP4-/- mice, in which stromal expression of CXCL12/CXCR4 and S100A4 was reduced. The EP3 or EP4 knockout suppressed S100A4+ fibroblasts, CXCL12+, and/or CXCR4+ stromal cells as well. Immunofluorescent analyses revealed that CXCL12+CXCR4+S100A4+ fibroblasts mainly comprised stromal cells and most of these were recruited from the BM. Additionally, either EP3- or EP4-specific agonists stimulated CXCL12 expression by fibroblasts in vitro. The present results address the novel activities of COX-2/PGE2-EP3/EP4 signaling that modulate tumor biology and show that CXCL12/CXCR4 axis may play a crucial role in tumor stromal formation and angiogenesis under the control of prostaglandins.

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.

Gene expression profiling of cholangiocarcinoma-derived fibroblast reveals alterations related to tumor progression and indicates periostin as a poor prognostic marker

Background

Fibroblasts play important roles in several cancers. It was hypothesized that cholangiocarcinoma (CCA)-associated fibroblasts (Cfs) differ from non-tumorigenic liver fibroblasts (Lfs) in their gene expression profiles resulting in the capability to promote cancer. Periostin (PN) is a multi-functional protein and has emerged as a promising marker for tumor progression. The role of PN in CCA, however, has not yet been explored.

Results

In this study, the gene expression profile of Cfs in comparison to Lfs was performed using oligonucleotide microarrays. The common- and unique-expressed genes in Cfs and the promising roles in cancer promotion and progression were determined. PN was markedly over-expressed in Cfs confirmed by real time RT-PCR and western blot analysis. Immunohistochemistry examination of a number of patients with intrahepatic CCA showed the expression of PN solely in stromal fibroblasts, but was expressed neither in cancer cells nor immune cells. Low to no expression of PN was observed in tissues of benign liver disease and hepatocellular carcinoma. CCA patients with high levels of PN had significantly shorter survival time than those with low levels (P = 0.026). Multivariate analysis revealed high levels of PN (P = 0.045) and presence of lymph node metastasis (P = 0.002) as independent poor prognostic factors. The in vitro study revealed that recombinant PN induced CCA cell proliferation and invasion. Interestingly, interference RNA against integrin α₅ significantly reduced the cellular response to PN-stimulated proliferation and invasion.

Conclusion

The gene expression profile of fibroblasts in CCA is apparently explored for the first time and has determined the genes involving in induction of this cancer progression. High PN can be used to distinguish CCA from other related liver diseases and is proposed as a prognostic factor of poor survival. Regulation of fibroblast-derived PN in CCA proliferation and invasion may be considered as an alternative therapeutic approach.

Gene expression profiling of cholangiocarcinoma-derived fibroblast reveals alterations related to tumor progression and indicates periostin as a poor prognostic marker

BACKGROUND

Fibroblasts play important roles in several cancers. It was hypothesized that cholangiocarcinoma (CCA)-associated fibroblasts (Cfs) differ from non-tumorigenic liver fibroblasts (Lfs) in their gene expression profiles resulting in the capability to promote cancer. Periostin (PN) is a multi-functional protein and has emerged as a promising marker for tumor progression. The role of PN in CCA, however, has not yet been explored.

RESULTS

In this study, the gene expression profile of Cfs in comparison to Lfs was performed using oligonucleotide microarrays. The common- and unique-expressed genes in Cfs and the promising roles in cancer promotion and progression were determined. PN was markedly over-expressed in Cfs confirmed by real time RT-PCR and western blot analysis. Immunohistochemistry examination of a number of patients with intrahepatic CCA showed the expression of PN solely in stromal fibroblasts, but was expressed neither in cancer cells nor immune cells. Low to no expression of PN was observed in tissues of benign liver disease and hepatocellular carcinoma. CCA patients with high levels of PN had significantly shorter survival time than those with low levels (P = 0.026). Multivariate analysis revealed high levels of PN (P = 0.045) and presence of lymph node metastasis (P = 0.002) as independent poor prognostic factors. The in vitro study revealed that recombinant PN induced CCA cell proliferation and invasion. Interestingly, interference RNA against integrin alpha 5 significantly reduced the cellular response to PN-stimulated proliferation and invasion.

CONCLUSION

The gene expression profile of fibroblasts in CCA is apparently explored for the first time and has determined the genes involving in induction of this cancer progression. High PN can be used to distinguish CCA from other related liver diseases and is proposed as a prognostic factor of poor survival. Regulation of fibroblast-derived PN in CCA proliferation and invasion may be considered as an alternative therapeutic approach.

S100A4 and metastasis: a small actor playing many roles

The calcium-binding protein S100A4 promotes metastasis in several experimental animal models, and S100A4 protein expression is associated with patient outcome in a number of tumor types. S100A4 is localized in the nucleus, cytoplasm, and extracellular space and possesses a wide range of biological functions, such as regulation of angiogenesis, cell survival, motility, and invasion. In this review, we summarize the evidence connecting S100A4 and cancer metastasis and discuss the mechanisms by which S100A4 promotes tumor progression.

S100A4 mRNA is a diagnostic and prognostic marker in pancreatic carcinoma

OBJECTIVE

The aim of this study is to evaluate the clinical significance of S100A4 mRNA expression in pancreatic cancer.

MATERIALS AND METHODS

We obtained invasive ductal carcinoma (IDC) cells from ten lesions, intraductal papillary mucinous neoplasm (IPMN) cells from 20 lesions, and normal ductal cells from 20 normal pancreatic tissues by laser microdissection of frozen tissues. S100A4 expression was examined in the microdissected cells and in formalin-fixed paraffin-embedded (FFPE) samples of 87 pancreatic cancers by quantitative reverse transcription-polymerase chain reaction.

RESULTS

IDC cells expressed higher levels of S100A4 than IPMN cells (P = 0.002) and normal ductal cells (P < 0.001), although the difference between IPMN cells and normal ductal cells was not statistically significant (P = 0.070). Analysis of FFPE samples revealed that high S100A4 expression was significantly associated with a shorter overall survival (P = 0.023). In immunohistochemical analysis, the extent of S100A4 mRNA expression was significantly correlated with the expression of S100A4 protein (P = 0.028).

CONCLUSION

S100A4 could be a marker for malignancy in pancreatic tumors and for poor prognosis in patients with pancreatic cancer.

Opposite roles of metastasin (S100A4) in two potentially tumoricidal mechanisms involving human lymphocyte protein Tag7 and Hsp70

We compare the physical and functional interactions between three widespread multifunctional proteins [metastasin (Mts1/S100A4), innate immunity-related Tag7/PGRP-S, and Hsp70] in two experimental models relevant to host-tumor relationships on humoral and cellular levels. (i) Tag7 and Hsp70 in solution or in a lymphocyte make a stable binary complex that is highly cytotoxic for some tumor cells. Here, we show that Mts1 prevents Tag7.Hsp70 assembly in solution, and an excess of Mts1 disrupts the existing Tag7.Hsp70 complex; accordingly, Tag7.Hsp70 cytotoxicity (exemplified with L929 cells) is diminished in the presence of excess Mts1. (ii) Tag7 exposed on a specialized subset of lymphokine-activated killer cells makes specific contact with Hsp70 exposed on some HLA-negative tumor cells, thus enabling FasL/Fas-mediated induction of apoptosis. Here, we show that some CD4(+)CD25(+) cells coexpose Mts1 with Tag7 and FasL, that Mts1 and Tag7 closely contact the same Hsp70 molecule on the target K562 cell (as evidenced by cross-linking), and that killing of such targets is abolished by Mts1-specific antibodies (or selective removal of Mts1-exposing lymphocytes). Thus, this phenotype active against immunoevasive cancerous cells is defined as CD4(+)CD25(+), FasL(+), Tag7(+)Mts1(+) (approximately 0.5% of total lymphocytes in culture). Remarkably, similar effectors with at least the same activity are often found in fresh donor blood samples (approximately 10(4) effectors/mL). Thus, our models suggest that interactions between the three proteins in different situations may have opposite functional outcomes as regards antitumor defense, immune escape, and metastasis.

S100A11: diverse function and pathology corresponding to different target proteins

S100A11, as a member of S100 protein family, while featuring the common identities as the other EF-hand Ca(2+)-binding family members, has its own individual characteristics. S100A11 is widely expressed in multiple tissues, and is located in cytoplasm, nucleus, and even cell periphery. S100A11 exists as a non-covalent homodimer with an antiparallel conformation. Ca(2+) binding to S100A11 would trigger conformational changes which would expose the hydrophobic cleft of S100A11 and facilitate its interaction with target proteins. Since S100A11 appears to lack enzymatic activity, in this article, corresponding to a variety of its target proteins, we systematically describe the biological roles of S100A11 and its possible mechanism in the processes of inflammation, regulation of enzyme activity, and cell growth regulation. As a dual cell growth mediator, S100A11 acts as either a tumor suppressor or promoter in many different types of tumors and would play respective roles in influencing the proliferation of the cancer cells. We intend to illustrate the biological function of the S100 protein, and shed light on the further research, which will provide us with a better understanding of it.

Immunogenicity of HLA-A1-restricted peptides derived from S100A4 (metastasin 1) in melanoma patients

S100A4 (metastasin 1) belongs to the S100 family of Ca(2+) binding proteins. While not present in most differentiated adult tissues, S100A4 is upregulated in the micromilieu of tumors. It is primarily expressed by tumor-associated macrophages, fibroblasts, and tumor endothelial cells. Due to its strong induction in tumors S100A4 is a promising target for cancer immunotherapy. By reverse immunology, using epitope prediction programs, we identified 3 HLA-A1-restricted peptide epitopes (S100A4 A1-1, A1-2, and A1-3) which are subject to human T cell responses as detected in peripheral blood of melanoma patients by means of IFN-gamma ELISPOT and cytotoxicity assays. In addition, IFN-gamma responses to S100A4 A1-2 can not only be induced by stimulation of T cells with peptide-loaded DC but also by stimulation with S100A4 protein-loaded DC, indicating that this epitope is indeed generated by processing of the endogenously expressed protein. In addition, S100A4 A1-2 reactive T cells demonstrate lysis of HLA-A1(+) fibroblasts in comparison to HLA-A1(-) fibroblasts. In summary, this HLA-A1-restricted peptide epitope is a candidate for immunotherapeutical approaches targeting S100A4-expressing cells in the tumor stroma.

Interleukin-7 stimulates secretion of S100A4 by activating the JAK/STAT signaling pathway in human articular chondrocytes

OBJECTIVE

S100A4 has been shown to be increased in osteoarthritic (OA) cartilage and to stimulate chondrocytes to produce matrix metalloproteinase 13 (MMP-13) through activation of the receptor for advanced glycation end products (RAGE). The aim of this study was to examine the mechanism of S100A4 secretion by chondrocytes.

METHODS

Human articular chondrocytes isolated from ankle cartilage were stimulated with 10 ng/ml of interleukin-1beta (IL-1beta), IL-6, IL-7, or IL-8. Cells were pretreated with either a JAK-3 inhibitor, brefeldin A, or cycloheximide. Immunoblotting with phospho-specific antibodies was used to determine the activation of signaling proteins. Secretion of S100A4 was measured in conditioned media by immunoblotting, and MMP-13 was measured by enzyme-linked immunosorbent assay.

RESULTS

Chondrocyte secretion of S100A4 was observed after treatment with IL-6 or IL-8 but was much greater in cultures treated with equal amounts of IL-7 and was not observed after treatment with IL-1beta. IL-7 activated the JAK/STAT pathway, with increased phosphorylation of JAK-3 and STAT-3, leading to increased production of S100A4 and MMP-13. Overexpression of a dominant-negative RAGE construct inhibited the IL-7-mediated production of MMP-13. Pretreatment of chondrocytes with a JAK-3 inhibitor or with cycloheximide blocked the IL-7-mediated secretion of S100A4, but pretreatment with brefeldin A did not.

CONCLUSION

IL-7 stimulates chondrocyte secretion of S100A4 via activation of JAK/STAT signaling, and then S100A4 acts in an autocrine manner to stimulate MMP-13 production via RAGE. Since both IL-7 and S100A4 are up-regulated in OA cartilage and can stimulate MMP-13 production by chondrocytes, this signaling pathway could contribute to cartilage destruction during the development of OA.

Genetic risk factors for portopulmonary hypertension in patients with advanced liver disease

RATIONALE

Portopulmonary hypertension (PPHTN) occurs in 6% of liver transplant candidates. The pathogenesis of this complication of portal hypertension is poorly understood.

OBJECTIVES

To identify genetic risk factors for PPHTN in patients with advanced liver disease.

METHODS

We performed a multicenter case-control study of patients with portal hypertension. Cases had a mean pulmonary artery pressure >25 mm Hg, pulmonary vascular resistance >240 dynes.s(-1).cm(-5), and pulmonary capillary wedge pressure < or =15 mm Hg. Controls had a right ventricular systolic pressure < 40 mm Hg (if estimated) and normal right-sided cardiac morphology by transthoracic echocardiography. We genotyped 1,079 common single nucleotide polymorphisms (SNPs) in 93 candidate genes in each patient.

MEASUREMENTS AND MAIN RESULTS

The study sample included 31 cases and 104 controls. Twenty-nine SNPs in 15 candidate genes were associated with the risk of PPHTN (P < 0.05). Multiple SNPs in the genes coding for estrogen receptor 1, aromatase, phosphodiesterase 5, angiopoietin 1, and calcium binding protein A4 were associated with the risk of PPHTN. The biological relevance of one of the aromatase SNPs was supported by an association with plasma estradiol levels.

CONCLUSIONS

Genetic variation in estrogen signaling and cell growth regulators is associated with the risk of PPHTN. These biologic pathways may elucidate the mechanism for the development of PPHTN in certain patients with severe liver disease.

Metastasis promoter S100A4 is a potentially valuable molecular target for cancer therapy

The growth, invasion and metastatic spread of cancer have been identified with the deregulation of cell proliferation, altered intercellular and cell-substratum adhesion and enhanced motility and the deposition of disseminated cancer cells at distant sites. The identification of therapeutic targets for cancer is crucial to human welfare. Drug development, molecular modelling and design of effective drugs greatly depend upon the identification of suitable therapeutic targets. Several genetic determinants relating to proliferation and growth, invasion and metastasis have been identified. S100A4 appears to be able to activate and integrate pathways to generate the phenotypic responses that are characteristic of cancer. S100A4 signalling can focus on factors associated with normal and aberrant proliferation, apoptosis and growth, and differentiation. It is able to activate signalling pathways leading to the remodelling of the cell membrane and the extracellular matrix; modulation of cytoskeletal dynamics, acquisition of invasiveness and induction of angiogenesis. Therefore S100A4 is arguably a molecular target of considerable potential possessing a wide ranging biological activity that can alter and regulate the major phenotypic features of cancer. The evolution of an appropriate strategy that permits the identification of therapeutic targets most likely to be effective in the disease process without unduly affecting normal biological processes and function is an incontrovertible imperative. By virtue of its ability to activate interacting and multi-functional signalling systems, S100A4 appears to offer suitable targets for developing new therapeutic procedures. Some effectors of the S100A4-activated pathways might also lend themselves as foci of therapeutic interest.

The Tumor Microenvironment: Key to Early Detection

The tumor microenvironment plays an important role equal to the tumor cell population in the progression of cancer. Consisting of stromal fibroblasts, inflammatory cells, components of the vasculature, normal epithelia, and extracellular matrix, the surrounding environment interacts or "cross-talks" with tumor cells through the release of growth factors, cytokines, proteases, and other bioactive molecules. Tumor growth, formation of new vascular networks, evasion of the host immune system, and invasion and metastasis are processes that co-evolve and become finely optimized and regulated within the tumor microenvironment. However, relatively recent reports on three areas of study have come together to add new levels of complexity to the tumor microenvironment. These include ectodomain shedding of proteins, shedding of membrane-derived vesicles, and novel roles for phospholipids. These dynamic changes that take place in the tumor microenvironment provide new avenues for study and for the early detection of cancer, whereas proteomic technologies provide the means to detect these unique proteins and lipids. Here we review the evolving concepts of the tumor microenvironment that, together with advances in proteomic technologies, hold the promise to facilitate the detection of early-stage cancer.

Activation of NF-kappaB by extracellular S100A4: analysis of signal transduction mechanisms and identification of target genes

The metastasis-promoting protein S100A4 stimulates metastatic progression through both intracellular and extracellular functions. Extracellular activities of S100A4 include stimulation of angiogenesis, regulation of cell death and increased cell motility and invasion, but the exact molecular mechanisms by which extracellular S100A4 exerts these effects are incompletely elucidated. The aim of the present study was to characterize S100A4-induced signal transduction mechanisms and to identify S100A4 target genes. We demonstrate that extracellular S100A4 activates the transcription factor NF-kappaB in a subset of human cancer cell lines through induction of phosphorylation and subsequent degradation of the NF-kappaB inhibitor IkappaBalpha. Concomitantly, S100A4 induced a sustained activation of the MAP kinase JNK, whereas no increased activity of the MAP kinases p38 or ERK was observed. Microarray analyses identified 136 genes as being significantly regulated by S100A4 treatment, and potentially interesting S100A4-induced gene products include IkappaBalpha, p53, ephrin-A1 and optineurin. Increased expression of ephrin-A1 and optineurin was validated using RT-PCR, Western blotting and functional assays. Furthermore, S100A4-stimulated transcription of these target genes was dependent on activation of the NF-kappaB pathway. In conclusion, these findings contribute to the understanding of the complex molecular mechanisms responsible for the diverse biological functions of extracellular S100A4, and provide further evidence of how S100A4 may stimulate metastatic progression.

S100A4: a common mediator of epithelial-mesenchymal transition, fibrosis and regeneration in diseases?

Multiple reports have focused on S100A4's role in cancer progression, specifically its ability to enhance metastasis. However, recent studies have linked S100A4 to several diseases besides cancer, including kidney fibrosis, cirrhosis, pulmonary disease, cardiac hypertrophy and fibrosis, arthritis and neuronal injuries. Common to all these diseases is the involvement of fibrotic and inflammatory processes, i.e. processes greatly dependent on tissue remodelling, cell motility and epithelial-mesenchymal transition. Therefore, the basic biological mechanisms behind S100A4's effects are emerging. S100A4 belongs to the S100 family of proteins that contain two Ca2+-binding sites including a canonical EF-hand motif. S100A4 is involved in the regulation of a wide range of biological effects including cell motility, survival, differentiation and contractility. S100A4 has both intracellular and extracellular effects. Hence, S100A4 interacts with cytoskeletal proteins and enhances metastasis of several types of cancer cells. In addition, S100A4 is secreted by unknown mechanisms, thus, paracrinely stimulating a variety of cellular responses, including angiogenesis and neuronal growth. Although many cellular effects of S100A4 are well described, the molecular mechanisms whereby S100A4 elicits these responses remain largely unknown. However, it is likely that the intracellular and the extracellular effects involve distinct mechanisms. In this review, we explore the possible roles of S100A4 in non-cancer diseases and employ this knowledge to describe underlying biological mechanisms including a change in cellular phenotype towards less tightly adherent cells and activation of fibrotic processes that may explain this protein's involvement in multiple pathologies.

The grateful dead: damage-associated molecular pattern molecules and reduction/oxidation regulate immunity

The response to pathogens and damage in plants and animals involves a series of carefully orchestrated, highly evolved, molecular mechanisms resulting in pathogen resistance and wound healing. In metazoans, damage- or pathogen-associated molecular pattern molecules (DAMPs, PAMPs) execute precise intracellular tasks and are also able to exert disparate functions when released into the extracellular space. The emergent consequence for both inflammation and wound healing of the abnormal extracellular persistence of these factors may underlie many clinical disorders. DAMPs/PAMPs are recognized by hereditable receptors including the Toll-like receptors, the NOD1-like receptors and retinoic-acid-inducible gene I-like receptors, as well as the receptor for advanced glycation end products. These host molecules 'sense' not only pathogens but also misfolded/glycated proteins or exposed hydrophobic portions of molecules, activating intracellular cascades that lead to an inflammatory response. Equally important are means to not only respond to these molecules but also to eradicate them. We have speculated that their destruction through oxidative mechanisms normally exerted by myeloid cells, such as neutrophils and eosinophils, or their persistence in the setting of pathologic extracellular reducing environments, maintained by exuberant necrotic cell death and/or oxidoreductases, represent important molecular means enabling chronic inflammatory states.

Dysregulation of matrix metalloproteinases and their tissue inhibitors by S100A4

The S100A4 protein as well as the matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are associated with diseases such as arthritis and cancer. This mini review focuses on in vitro and in vivo studies indicating S100A4 involvement in regulation of MMPs and TIMPs, and the biological and pathobiological consequences of this regulation.

Expression of S100A4 by a variety of cell types present in the tumor microenvironment of human breast cancer

The S100A4 protein, which is involved in the metastasis process, is a member of the S100 superfamily of Ca-binding proteins. Members of this family are multifunctional signaling proteins with dual extra and intracellular functions involved in the regulation of diverse cellular processes. Several studies have established a correlation between S100A4 protein expression and worse prognosis for patients with various malignancies including breast cancer. In this article, we have used specific antibodies in combination with immunohistochemistry (IHC) to identify the cell types that express S100A4 in human breast cancer biopsies obtained from high-risk patients. IHC analysis of 68 tumor biopsies showed that the protein is expressed preferentially by various cell types present in the tumor microenvironment (macrophages, fibroblasts, activated lymphocytes), rather than by the tumor cells themselves. Moreover, we show that the protein is externalized by the stroma cells to the fluid that bathes the tumor microenvironment, where it is found in several forms that most likely correspond to charge variants. Using a specific ELISA test, we detected a significant higher concentration of S100A4 in the tumor interstitial fluid (TIF) as compared to their corresponding normal counterparts (NIF).

CTGF enhances the motility of breast cancer cells via an integrin-alphavbeta3-ERK1/2-dependent S100A4-upregulated pathway

Connective tissue growth factor (CTGF) expression is elevated in advanced stages of breast cancer, but the regulatory role of CTGF in invasive breast cancer cell phenotypes is unclear. Presently, overexpression of CTGF in MCF-7 cells (MCF-7/CTGF cells) enhanced cellular migratory ability and spindle-like morphological alterations, as evidenced by actin polymerization and focal-adhesion-complex aggregation. Reducing the CTGF level in MDA-MB-231 (MDA231) cells by antisense CTGF cDNA (MDA231/AS cells) impaired cellular migration and promoted a change to an epithelial-like morphology. A neutralizing antibody against integrin alphavbeta3 significantly attenuated CTGF-mediated ERK1/2 activation and cellular migration, indicating that the integrin-alphavbeta3-ERK1/2 signaling pathway is crucial in mediating CTGF function. Moreover, the cDNA microarray analysis revealed CTGF-mediated regulation of the prometastatic gene S100A4. Transfection of MCF-7/CTGF cells with AS-S100A4 reversed the CTGF-induced cellular migratory ability, whereas overexpression of S100A4 in MDA231/AS cells restored their high migratory ability. Genetic and pharmacological manipulations suggested that the CTGF-mediated S100A4 upregulation was dependent on ERK1/2 activation, with expression levels of CTGF and S100A4 being closely correlated with human breast tumors. We conclude that CTGF plays a crucial role in migratory/invasive processes in human breast cancer by a mechanism involving activation of the integrin-alphavbeta3-ERK1/2-S100A4 pathway.

Expression, purification and fluorine-18 radiolabeling of recombinant S100 proteins--potential probes for molecular imaging of receptor for advanced glycation endproducts (RAGE) in vivo

Data concerning the pathophysiological role of the interaction of circulating S100 proteins, a multigenic family of Ca(2+)-modulated proteins, with the receptor for advanced glycation endproducts (RAGE) in cardiovascular diseases, inflammatory processes, and tumorigenesis in vivo are scarce. One reason is the shortage of suitable radiotracer methods. We report a novel methodology using recombinant human S100A1, S100B, and S100A12 as potential probes for molecular imaging of this interaction. Therefore, human S100 proteins were cloned as GST fusion proteins in the bacterial expression vector pGEX-6P-1 and expressed in E. coli strain BL21. Purified recombinant human S100 proteins were radiolabeled with the positron emitter fluorine-18 ((18)F) by conjugation with N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). The radiolabeled recombinant S100 proteins ((18)F-S100) were used in biodistribution experiments and small animal positron emission tomography (PET) studies in rats. The tissue-specific distribution of (18)F-S100 proteins in vivo correlated well with the anatomical localization of RAGE, e.g., in lungs and in the vascular system. These findings indicate circulating S100A1, S100B, and S100A12 proteins to be ligands for RAGE in rats in vivo. The approach allows the use of small animal PET and provides novel probes to delineate functional expression of RAGE under normal and pathophysiological conditions in rodent models of disease.

Intimal smooth muscle cells of porcine and human coronary artery express S100A4, a marker of the rhomboid phenotype in vitro

We reported that smooth muscle cell (SMC) populations isolated from normal porcine coronary artery media exhibit distinct phenotypes: spindle-shaped (S) and rhomboid (R). R-SMCs are recovered in higher proportion from stent-induced intimal thickening compared with media suggesting that they participate in intimal thickening formation. Our aim was to identify a marker of R-SMCs in vitro and to explore its possible expression in vivo. S- and R-SMC protein extracts were compared by means of 2-dimensional polyacrylamide gel electrophoresis followed by tandem mass spectrometry. S100A4 was found to be predominantly expressed in R-SMC extracts. Using a monoclonal S100A4 antibody we confirmed that S100A4 is highly expressed by R-SMCs and hardly detectable in S-SMCs. S100A4 was colocalized with alpha-smooth muscle actin in stress fibers of several quiescent cells and upregulated during migration. PDGF-BB, FGF-2 or coculture with endothelial cells, which modulate S-SMCs to a R-phenotype, increased S100A4 expression in both S- and R-SMCs. Silencing of S100A4 mRNA in R-SMCs decreased cell proliferation, suggesting a functional role for this protein. In vivo S100A4 was absent in normal porcine coronary artery media, but highly expressed by SMCs of stent-induced intimal thickening. In humans, S100A4 was barely detectable in coronary artery media and markedly expressed in SMCs of atheromatous and restenotic coronary artery lesions. Our results indicate that S100A4 is a marker of porcine R-SMCs in vitro and of intimal SMCs during intimal thickening development. It is also a marker of a large population of human atheromatous and restenotic SMCs. Clarifying S100A4 function might be useful to understand the evolution of atherosclerotic and restenotic processes.

Modified expression of Mts1/S100A4 protein in C6 glioma cells or surrounding astrocytes affects migration of tumor cells in vitro and in vivo

The calcium-binding Mts1/S100A4 protein plays an important role in motility and metastatic activity of tumor cells. Recently we showed that Mts1/S100A4 is expressed in white matter astrocytes and influences their migration in vitro and in vivo. Here, we have investigated the role of Mts1/S100A4 expression in C6 glioma cells or surrounding astrocytes for migration of C6 cells on astrocytes, using short interference (si) RNA to silence Mts1/S100A4 expression. We find that in vitro, the migration of Mts1/S100A4 expressing and silenced C6 cells on astrocytes is predominantly dependent on the expression of Mts1/S100A4 in astrocytes, i.e. C6 cells preferably migrate on Mts1/S100A4-silenced astrocytes. In vivo, Mts1/S100A4-positive C6 cells preferably migrate in white matter. In contrast Mts1/S100A4-silenced C6 cells avoid white matter and migrate in gray matter and meninges. Thus, the migration pattern of C6 cells is affected by their intrinsic Mts1/S100A4 expression as well as Mts1/S100A4 expression in astrocytes. To investigate if Mts1/S100A4 has a significant role on brain tumor progression, we made quantitative RT-PCR analysis for the expression of S100A4/Mts1 in various grades of astrocytic tumors. Our data showed that high-grade glioblastomas express higher amount of S100A4/Mts1 than low-grade astrocytic tumors.

Up-regulation of metastasis-promoting S100A4 (Mts-1) in rheumatoid arthritis: Putative involvement in the pathogenesis of rheumatoid arthritis

OBJECTIVE

To examine the involvement of the metastasis-inducing protein S100A4 (Mts-1) in the pathogenesis of rheumatoid arthritis (RA).

METHODS

Synovial tissue, synovial fluid, and plasma were obtained from RA and osteoarthritis (OA) patients who were undergoing joint surgery. Immunohistochemical and immunofluorescence analyses and enzyme-linked immunosorbent assays were used to determine the locations and concentrations of S100A4. The conformational structure of S100A4 in plasma and synovial fluid was determined after fractionation by size-exclusion chromatography, protein separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western blot analysis. Expression of various S100 proteins in RA synovium was determined by immunofluorescence and double-staining using specific anti-S100 antibodies.

RESULTS

We found an up-regulation of S100A4 in cells infiltrating RA synovial tissue. Most cell types identified by cell-specific markers (fibroblasts, immune cells, and vascular cells) contributed to the production of S100A4 in RA synovial tissue. The pattern of S100A4 expression differed significantly from that of the proinflammatory proteins S100A9 and S100A12, which were restricted to phagocytes and granulocytes. The up-regulation of S100A4 in RA synovial tissue was consistent with the high concentrations of the protein in RA versus OA plasma (mean 1,100 versus 211 ng/ml) and synovial fluid (mean 1,980 versus 247 ng/ml). Moreover, we found that S100A4 in RA plasma and synovial fluid was present in bioactive multimeric (M-S100A4) conformations, whereas in OA, the majority of extracellular S100A4 was detected as the less active dimeric form. Consistent with our observations in tumor models, extracellular S100A4 stabilized the p53 tumor suppressor in RA synovial fibroblast-like cells and affected the regulation of p53 target genes, including Bcl-2, p21(WAF), and Hdm-2, as well as matrix metalloproteinases.

CONCLUSION

Overexpression of S100A4 in RA synovial tissue and its release as M-S100A4 can influence p53 function and modulate the expression of several genes that are potentially implicated in the disease process. Thus, S100A4 might play an important role in the pathogenesis of RA and might represent a new target for the treatment of RA.

Role of Annexin-II in GI cancers: interaction with gastrins/progastrins

The role of the gastrin peptide hormones (G17, G34) and their precursors (progastrins, PG; gly-extended gastrin, G-gly), in gastrointestinal (GI) cancers has been extensively reviewed in recent years [W. Rengifo-Cam, P. Singh, Role of progastrins and gastrins and their receptors in GI and pancreatic cancers: targets for treatment, Curr. Pharm. Des. 10 (19) (2004) 2345-2358; M. Dufresne, C. Seva, D. Fourmy, Cholecystokinin and gastrin receptors, Physiol. Rev. 86 (3) (2006) 805-847; A. Ferrand, T.C. Wang, Gastrin and cancer: a review, Cancer Lett. 238 (1) (2006) 15-29]. A possible important role of progastrin peptides in colon carcinogenesis has become evident from experiments with transgenic mouse models [W. Rengifo-Cam, P. Singh, (2004); A. Ferrand, T.C. Wang, (2006)]. It is now known that growth stimulatory and co-carcinogenic effects of gastrin/PG peptides are mediated by both proliferative and anti-apoptotic effects of the peptides on target cells [H. Wu, G.N. Rao, B. Dai, P. Singh, Autocrine gastrins in colon cancer cells Up-regulate cytochrome c oxidase Vb and down-regulate efflux of cytochrome c and activation of caspase-3, J. Biol. Chem. 275 (42) (2000) 32491-32498; H. Wu, A. Owlia, P. Singh, Precursor peptide progastrin(1-80) reduces apoptosis of intestinal epithelial cells and upregulates cytochrome c oxidase Vb levels and synthesis of ATP, Am. J. Physiol. Gastrointest. Liver Physiol. 285 (6) (2003) G1097-G1110]. Several receptor subtypes have been described that mediate growth effects of gastrin peptides [W. Rengifo-Cam, P. Singh (2004); M. Dufresne, C. Seva, D. Fourmy, (2006)]. Recently, we identified Annexin II as a high affinity binding protein for gastrin/PG peptides [P. Singh, H. Wu, C. Clark, A. Owlia, Annexin II binds progastrin and gastrin-like peptides, and mediates growth factor effects of autocrine and exogenous gastrins on colon cancer and intestinal epithelial cells, Oncogene (2006), doi:10.1038/sj.onc.1209798]. Importantly, the expression of Annexin II was required for mediating growth stimulatory effects of gastrin and PG peptides on intestinal epithelial and colon cancer cells [P. Singh, H. Wu, C. Clark, A. Owlia, Annexin II binds progastrin and gastrin-like peptides, and mediates growth factor effects of autocrine and exogenous gastrins on colon cancer and intestinal epithelial cells, Oncogene (2006), doi:10.1038/sj.onc.1209798], suggesting that Annexin-II may represent the elusive novel receptor for gastrin/PG peptides. The importance of this finding in relation to the structure and function of Annexin-II, especially in GI cancers, is described below. Since this surprising finding represents a new front in our understanding of the mechanisms involved in mediating growth effects of gastrin/PG peptides in GI cancers, our current understanding of the role of Annexin-II in proliferation and metastasis of cancer cells is additionally reviewed.

S100A4 is expressed at site of invasion in rheumatoid arthritis synovium and modulates production of matrix metalloproteinases

The metastasis-associated protein S100A4 promotes the progression of cancer by regulating the remodelling of the extracellular matrix. The expression of S100A4 in vivo is shown and the functional role of S100A4 in the pathogenesis of osteoarthritis and rheumatoid arthritisis is explored. The expression of S100A4 in rheumatoid arthritis, osteoarthritis and normal synovial tissues was determined by immunohistochemistry. The expression of matrix metalloproteinase (MMP) mRNA was measured in rheumatoid arthritis and osteoarthritis synovial fibroblasts treated and untreated with S100A4 oligomer by real-time polymerase chain reaction. Levels of released MMPs were confirmed by ELISA in cell culture supernatants. S100A4 protein was expressed in rheumatoid arthritis and osteoarthritis synovial tissues, in contrast with normal synovium. S100A4 up regulated MMP-3 mRNA in rheumatoid arthritis synovial fluid, with a peak after 6 h. This resulted in release of MMP-3 protein. MMP-1, MMP-9 and MMP-13 mRNA were also up regulated in synovial fluid, but with different kinetics. MMP-14 mRNA showed no change. Thus, S100A4 protein is expressed in synovial tissues of patients with rheumatoid arthritis and osteoarthritis in contrast with healthy people. It induces the expression and release of MMP-3 and other MMPs from synovial fluid. The data suggest that S100A4-producing cells could be involved in the pathogenesis of osteoarthritis and rheumatoid arthritis, including pannus formation and joint destruction.