Human S100A4 (p9Ka) induces the metastatic phenotype upon benign tumour cells

Targeted Destruction of S100A4 Inhibits Metastasis of Triple Negative Breast Cancer Cells

Most patients who die of cancer do so from its metastasis to other organs. The calcium-binding protein S100A4 can induce cell migration/invasion and metastasis in experimental animals and is overexpressed in most human metastatic cancers. Here, we report that a novel inhibitor of S100A4 can specifically block its increase in cell migration in rat (IC50, 46 µM) and human (56 µM) triple negative breast cancer (TNBC) cells without affecting Western-blotted levels of S100A4. The moderately-weak S100A4-inhibitory compound, US-10113 has been chemically attached to thalidomide to stimulate the proteasomal machinery of a cell. This proteolysis targeting chimera (PROTAC) RGC specifically eliminates S100A4 in the rat (IC50, 8 nM) and human TNBC (IC50, 3.2 nM) cell lines with a near 20,000-fold increase in efficiency over US-10113 at inhibiting cell migration (IC50, 1.6 nM and 3.5 nM, respectively). Knockdown of S100A4 in human TNBC cells abolishes this effect. When PROTAC RGC is injected with mouse TNBC cells into syngeneic Balb/c mice, the incidence of experimental lung metastases or local primary tumour invasion and spontaneous lung metastasis is reduced in the 10-100 nM concentration range (Fisher's Exact test, p ≤ 0.024). In conclusion, we have established proof of principle that destructive targeting of S100A4 provides the first realistic chemotherapeutic approach to selectively inhibiting metastasis.

The Role of the C-Terminal Lysine of S100P in S100P-Induced Cell Migration and Metastasis

S100P protein is a potent inducer of metastasis in a model system, and its presence in cancer cells of patients is strongly associated with their reduced survival times. A well-established Furth Wistar rat metastasis model system, methods for measuring cell migration, and specific inhibitors were used to study pathways of motility-driven metastasis. Cells expressing C-terminal mutant S100P proteins display markedly-reduced S100P-driven metastasis in vivo and cell migration in vitro. These cells fail to display the low focal adhesion numbers observed in cells expressing wild-type S100P, and the mutant S100P proteins exhibit reduced biochemical interaction with non-muscle myosin heavy chain isoform IIA in vitro. Extracellular inhibitors of the S100P-dependent plasminogen activation pathway reduce, but only in part, wild-type S100P-dependent cell migration; they are without effect on S100P-negative cells or cells expressing C-terminal mutant S100P proteins and have no effect on the numbers of focal adhesions. Recombinant wild-type S100P protein, added extracellularly to S100P-negative cells, stimulates cell migration, which is abolished by these inhibitors. The results identify at least two S100P-dependent pathways of migration, one cell surface and the other intracellularly-linked, and identify its C-terminal lysine as a target for inhibiting multiple migration-promoting activities of S100P protein and S100P-driven metastasis.

The liver metastatic niche: modelling the extracellular matrix in metastasis

Dissemination of malignant cells from primary tumours to metastatic sites is a key step in cancer progression. Disseminated tumour cells preferentially settle in specific target organs, and the success of such metastases depends on dynamic interactions between cancer cells and the microenvironments they encounter at secondary sites. Two emerging concepts concerning the biology of metastasis are that organ-specific microenvironments influence the fate of disseminated cancer cells, and that cancer cell-extracellular matrix interactions have important roles at all stages of the metastatic cascade. The extracellular matrix is the complex and dynamic non-cellular component of tissues that provides a physical scaffold and conveys essential adhesive and paracrine signals for a tissue's function. Here, we focus on how extracellular matrix dynamics contribute to liver metastases - a common and deadly event. We discuss how matrix components of the healthy and premetastatic liver support early seeding of disseminated cancer cells, and how the matrix derived from both cancer and liver contributes to the changes in niche composition as metastasis progresses. We also highlight the technical developments that are providing new insights into the stochastic, dynamic and multifaceted roles of the liver extracellular matrix in permitting and sustaining metastasis. An understanding of the contribution of the extracellular matrix to different stages of metastasis may well pave the way to targeted and effective therapies against metastatic disease.

Optimization of Peptidomimetics as Selective Inhibitors for the β-Catenin/T-Cell Factor Protein-Protein Interaction

The β-catenin/T-cell factor (Tcf) protein-protein interaction (PPI) plays a critical role in the β-catenin signaling pathway which is hyperactivated in many cancers and fibroses. Based on compound 1, which was designed to target the Tcf4 G¹³ANDE¹⁷ binding site of β-catenin, extensive structure-activity relationship studies have been conducted. As a result, compounds 53 and 57 were found to disrupt the β-catenin/Tcf PPI with the K_i values of 0.64 and 0.44 μM, respectively, and exhibit good selectivity for β-catenin/Tcf over β-catenin/E-cadherin and β-catenin/adenomatous polyposis coli (APC) PPIs. The 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2 H-tetrazolium (MTS) cell viability assays revealed that 56, the ethyl ester of 53, was more potent than 53 in inhibiting viability of most of the Wnt/β-catenin hyperactive cancer cells. Further cell-based studies indicated that 56 disrupted the β-catenin/Tcf PPI without affecting the β-catenin/E-cadherin and β-catenin/APC PPIs, suppressed transactivation of Wnt/β-catenin signaling in dose-dependent manners, and inhibited migration and invasiveness of Wnt/β-catenin-dependent cancer cells.

Expression and Roles of S100A4 in Anaplastic Cells of Canine Mammary Carcinomas

S100A4 (metastasin), a member of the S100 protein family, was initially identified in metastatic cells and is well established as a marker of aggressive human cancer. However, expression and roles of S100A4 in canine mammary tumors have not been clarified. In this study, expression of S100A4 was examined immunohistochemically in normal, hyperplastic, and neoplastic mammary glands of dogs. In all normal and benign lesions, S100A4 was restricted to a few stromal fibroblasts and inflammatory cells. However, in 7 of 57 (12%) of the malignant tumors examined, cytoplasmic and nuclear expression of S100A4 was observed in epithelial tumor cells and stromal cells. Particularly, the frequency of S100A4-positive anaplastic carcinomas was high (4/8 cases, 50%). Next, we established a novel cell line, named NV-CML, from a S100A4-positive canine mammary carcinoma. The cultured NV-CML cells and the tumors that developed in the immunodeficient mice after subcutaneous injection of the cells maintained the immunophenotype of the original tumor, including S100A4 expression. Using this cell line, we examined the cellular functions of S100A4 using RNA interference. S100A4 expression level in NV-CML cells transfected with small interfering RNA (siRNA) targeting canine S100A4 (siS100A4) was reduced to about one-fifth of those with negative-control siRNA (siNeg). Cell proliferation in WST-8 assay and cell migration in Boyden chamber assay were significantly decreased in siS100A4-transfected cells compared with siNeg-transfected cells. These findings suggest that S100A4 may be related to progression of canine mammary carcinomas via its influence on cell growth and motility.

Attenuation of cancer-initiating cells stemness properties by abrogating S100A4 calcium binding ability in head and neck cancers

S100A4 is a calcium-binding protein capable of promoting epithelial-mesenchymal transition. Previously, we have demonstrated that S100A4 is required to sustain the head and neck cancer-initiating cells (HN-CICs) subpopulation. In this study, to further investigate the molecular mechanism, we established the head and neck squamous cell carcinoma (HNSCC) cell lines stably expressing mutant S100A4 proteins with defective calcium-binding sites on either N-terminal (NM) or C-terminal (CM), or a deletion of the last 15 amino-acid residues (CD). We showed that the NM, CM and CD harboring sphere cells that were enriched with HN-CICs population exhibited impaired stemness and malignant properties in vitro, as well as reduced tumor growth ability in vivo. Mechanistically, we demonstrated that mutant S100A4 proteins decreased the promoter activity of Nanog, likely through inhibition of p53. Moreover, the biophysical analyses of purified recombinant mutant S100A4 proteins suggest that both NM and CM mutant S100A4 were very similar to the WT S100A4 with subtle difference on the secondary structure, and that the CD mutant protein displayed the unexpected monomeric form in the solution phase.Taken together, our results suggest that both the calcium-binding ability and the C-terminal region of S100A4 are important for HN-CICs to sustain its stemness property and malignancy, and that the mechanism could be mediated by repressing p53 and subsequently activating the Nanog expression.

Role of Wnt Co-Receptor LRP6 in Triple Negative Breast Cancer Cell Migration and Invasion

The low-density lipoprotein receptor-related protein 6 (LRP6) is an essential Wnt co-receptor of the Wnt/β-catenin signaling pathway. Although studies have shown an increased expression of LRP6 in several types of cancer, its function in tumor development and progression remains to be elucidated. We herein demonstrated that LRP6 expression is up-regulated in human triple negative breast cancer (TNBC) patients and human TNBC cell lines, and that knockdown of LRP6 expression and treatment of recombinant Mesd protein (a specific inhibitor of LRP6) significantly decreased cell migration and invasion of TNBC MDA-MB-231 and BT549 cells. Interestingly, the effects of LRP6 knockdown and Mesd treatment on TNBC cell migration and invasion were more prominent than on TNBC cell proliferation/viability. Mechanistically, LRP6 knockdown and Mesd treatment inhibited Wnt/β-catenin signaling and decreased the expression of S100A4, a mediator of cancer metastasis and a specific target of Wnt/β-catenin signaling, in TNBC cells. Together, our data suggest that LRP6 promotes TNBC cell migration and invasion by regulating the expression and function of S100A4 via the Wnt/β-catenin signaling pathway. J. Cell. Biochem. 118: 2968-2976, 2017. © 2017 Wiley Periodicals, Inc.

Expression and Functional Analysis of Tumor-Related Factor S100A4 in Antler Stem Cells

Annual antler renewal is a stem cell-based epimorphic process driven by antler stem cells (ASCs) resident in antlerogenic periosteum (AP). Antlerogenic periosteal cells express a high level of S100A4, a metastasis-associated protein, which intrigued us to explore what role S100A4 could play in antler regeneration. The present study set out to investigate expression and effects of S100A4 in the ASCs and their progeny. The results showed that not only did cells from the AP express a high level of S100A4, but also the pedicle periosteum and the antler growth center. In the antler growth center, we found S100A4-positive cells were specifically located in blood vessel walls and in vascularized areas. In vitro, recombinant deer S100A4 protein stimulated the proliferation of the AP cells, promoted proliferation, migration and tube formation of human vascular endothelial cells, and enhanced migration of Hela cells, but not AP cells. These findings demonstrated that S100A4 in the ASCs may play a significant role in stimulating angiogenesis, proliferation, but not motility, of ASCs. Deer antlers offer a unique model to explore how rapid cell proliferation with a high level of S100A4 expression is elegantly regulated without becoming cancerous.

S100A4 Is a Biomarker and Regulator of Glioma Stem Cells That Is Critical for Mesenchymal Transition in Glioblastoma

Glioma stem cells (GSC) and epithelial-mesenchymal transition (EMT) are strongly associated with therapy resistance and tumor recurrence, but the underlying mechanisms are incompletely understood. Here, we show that S100A4 is a novel biomarker of GSCs. S100A4⁺ cells in gliomas are enriched with cancer cells that have tumor-initiating and sphere-forming abilities, with the majority located in perivascular niches where GSCs are found. Selective ablation of S100A4-expressing cells was sufficient to block tumor growth in vitro and in vivo We also identified S100A4 as a critical regulator of GSC self-renewal in mouse and patient-derived glioma tumorspheres. In contrast with previous reports of S100A4 as a reporter of EMT, we discovered that S100A4 is an upstream regulator of the master EMT regulators SNAIL2 and ZEB along with other mesenchymal transition regulators in glioblastoma. Overall, our results establish S100A4 as a central node in a molecular network that controls stemness and EMT in glioblastoma, suggesting S100A4 as a candidate therapeutic target. Cancer Res; 77(19); 5360-73. ©2017 AACR.

Control of cell mechanics by RhoA and calcium fluxes during epithelial scattering

Epithelial tissues use adherens junctions to maintain tight interactions and coordinate cellular activities. Adherens junctions are remodeled during epithelial morphogenesis, including instances of epithelial-mesenchymal transition, or EMT, wherein individual cells detach from the tissue and migrate as individual cells. EMT has been recapitulated by growth factor induction of epithelial scattering in cell culture. In culture systems, cells undergo a highly reproducible series of cell morphology changes, most notably cell spreading followed by cellular compaction and cell migration. These morphology changes are accompanied by striking actin rearrangements. The current evidence suggests that global changes in actomyosin-based cellular contractility, first a loss of contractility during spreading and its activation during cell compaction, are the main drivers of epithelial scattering. In this review, we focus on how spreading and contractility might be controlled during epithelial scattering. While we propose a central role for RhoA, which is well known to control cellular contractility in multiple systems and whose role in epithelial scattering is well accepted, we suggest potential roles for additional cellular systems whose role in epithelial cell biology has been less well documented. In particular, we propose critical roles for vesicle recycling, calcium channels, and calcium-dependent kinases.

Kaiso depletion attenuates transforming growth factor-β signaling and metastatic activity of triple-negative breast cancer cells

Triple-negative breast cancers (TNBCs) represent a subset of breast tumors that are highly aggressive and metastatic, and are responsible for a disproportionate number of breast cancer-related deaths. Several studies have postulated a role for the epithelial-to-mesenchymal transition (EMT) program in the increased aggressiveness and metastatic propensity of TNBCs. Although EMT is essential for early vertebrate development and wound healing, it is frequently co-opted by cancer cells during tumorigenesis. One prominent signaling pathway involved in EMT is the transforming growth factor-β (TGFβ) pathway. In this study, we report that the novel POZ-ZF transcription factor Kaiso is highly expressed in TNBCs and correlates with a shorter metastasis-free survival. Notably, Kaiso expression is induced by the TGFβ pathway and silencing Kaiso expression in the highly invasive breast cancer cell lines, MDA-MB-231 (hereafter MDA-231) and Hs578T, attenuated the expression of several EMT-associated proteins (Vimentin, Slug and ZEB1), abrogated TGFβ signaling and TGFβ-dependent EMT. Moreover, Kaiso depletion attenuated the metastasis of TNBC cells (MDA-231 and Hs578T) in a mouse model. Although high Kaiso and high TGFβR1 expression is associated with poor overall survival in breast cancer patients, overexpression of a kinase-active TGFβR1 in the Kaiso-depleted cells was insufficient to restore the metastatic potential of these cells, suggesting that Kaiso is a key downstream component of TGFβ-mediated pro-metastatic responses. Collectively, these findings suggest a critical role for Kaiso in TGFβ signaling and the metastasis of TNBCs.

S100 proteins in cancer

In humans, the S100 protein family is composed of 21 members that exhibit a high degree of structural similarity, but are not functionally interchangeable. This family of proteins modulates cellular responses by functioning both as intracellular Ca(2+) sensors and as extracellular factors. Dysregulated expression of multiple members of the S100 family is a common feature of human cancers, with each type of cancer showing a unique S100 protein profile or signature. Emerging in vivo evidence indicates that the biology of most S100 proteins is complex and multifactorial, and that these proteins actively contribute to tumorigenic processes such as cell proliferation, metastasis, angiogenesis and immune evasion. Drug discovery efforts have identified leads for inhibiting several S100 family members, and two of the identified inhibitors have progressed to clinical trials in patients with cancer. This Review highlights new findings regarding the role of S100 family members in cancer diagnosis and treatment, the contribution of S100 signalling to tumour biology, and the discovery and development of S100 inhibitors for treating cancer.

Use of proteins as biomarkers and their role in carcinogenesis

Summary: Improved diagnostic methods and medical therapies are necessary for early detection and treatment and an improved prognosis. It is thus vital to both examine and evaluate the role of the various existing proteins as biomarkers in carcinogenesis and to assess the contribution of these proteins in anti-cancer activity, for consideration in therapeutic strategies. It is essential to both examine and evaluate the role of the various existing proteins as biomarkers in carcinogenesis and to assess the contribution of these proteins in anti-cancer activity, for consideration in therapeutic strategies. The purpose of this review is twofold. Firstly, it is to evaluate recent data about which proteins can be utilized as biomarkers in carcinogenesis. The proteins reviewed include: CPTP, IL-6, CCN, and S100. Secondly, it is to evaluate the contribution of dietary proteins in cancer activity. Specifically, how whey protein, soy proteins and lectin, a phytochemical could be useful in cancer prevention and treatment.

Recent Findings: Whey protein, present in dairy products, is an excellent source of the sulphur amino acid cysteine, the rate limiting substrate in glutathione synthesis. Notably, this protein survives digestion and has been shown to have anti-carcinogenic properties in animal studies. Lectins are phytochemicals present in plant foods, and have active components which alters cancer initiation, promotion and progression. Lectins have been characterized as a useful tool in biochemistry, cell biology, immunology and in diagnostic and therapeutic purposes in cancer research. Soy proteins contain various compounds, including isoflavones, protease inhibitors and protein kinase inhibitors, which have been proven effective in tumor growth inhibition. They have therefore, been greatly emphasized in cancer prevention and treatment. It has been proved that soy food consumption was associated with decreased risk of death and recurrence of breast cancer. CPTP is a recently discovered protein whose main role is to transport C1P, a pro-inflammatory molecule. The discovery of CPTP may shine a light on the mechanism of inflammatory diseases, and hopefully offer a potential target for therapeutic purposes in cancer research. Interleukin-6 is a multifunctional cytokine that affects the activity of cancer cells. It is involved in tumor growth, and elevated levels is associated with an increased risk of cancer. S100B is a well-established biomarker for malignant melanoma, and useful in assessing tumor load, stage and prognosis for patients with this disease. Other members of this family of proteins include S100A4, which has been associated with several malignancies and S100A2, which has been found to be decreased in some cancers. CCN are a group of regulatory proteins, located in the extracellular matrix (maricellular). They are involved in cellular adhesion, mitogenesis, chemotaxis, cell survival, and wound healing. CCN proteins are also able to modulate the signals of several proteins, which may also influence skeletal development and angiogenesis. Many of the functions of these proteins are thus also related to tumor growth. Furthermore, CCN interacts with estrogen in the development of cancer, and is implicated in some breast and ovarian cancers.

Clinicopathological and prognostic value of S100A4 expression in gastric cancer: a meta-analysis

PURPOSES

For several years S100A4 has been implicated in tumor progression and prognosis. However, the prognostic value of S100A4 overexpression in patients with gastric cancer remains unknown. Therefore, we performed a meta-analysis to assess the relationship between S100A4 overexpression and clinical outcome of gastric cancer.

METHODS AND RESULTS

Candidate studies were searched from PubMed, Embase, Cochrane Library, and ISI Web of Science. We included studies that evaluated the prognostic value of S100A4 expression in gastric cancer patients with regard to survival and a series of clinicopathological parameters. The pooled hazard ratios (HR) and odds ratios (OR) with 95% confidence intervals (CI) were used to estimate the effects. Ten studies, all from Asia, were included in the meta-analysis. The pooled analysis showed that S100A4 overexpression was significantly associated with worse overall survival (OS) (HR=1.86, 95% CI: 1.45-2.38, p<0.00001) without heterogeneity in the data (I2=43.6%, p=0.131). Furthermore, our results showed that S100A4 overexpression was significantly correlated with some clinicopathological parameters such as tumor grade, stage, metastasis, invasion, and relapse.

CONCLUSIONS

The results of our meta-analysis indicate that S100A4 overexpression correlates with more adverse clinical features and a poor prognosis of gastric cancer patients in Asia, thus suggesting that S100A4 could be a useful marker to evaluate progression and prognosis of Asian gastric cancer patients. More studies from Western countries with a larger number of tumors and standardized methods are required before significant conclusions can be drawn.

Inhibition of the activation of hepatic stellate cells by arundic acid via the induction of cytoglobin

BACKGROUND

The activation of hepatic stellate cells plays a central role in the development of liver fibrosis during chronic liver trauma. The aim of the present study was to identify a compound that inhibits the activation process of stellate cells.

METHODS

Rat primary cultured stellate cells and a human stellate cell line (LX-2) were used. The effects of arundic acid on the expression of α-smooth muscle actin, collagen 1α1, and cytoglobin were evaluated.

RESULTS

Arundic acid (300 μM) inhibited the activation of primary rat stellate cells, as determined by morphological transformation and α-smooth muscle actin expression, after both prophylactic and therapeutic treatment. The level of α-smooth muscle actin mRNA showed a dose-dependent decrease in response to arundic acid, and 50 μM arundic acid exhibited the maximum inhibition of collagen 1α1 mRNA expression. In contrast, arundic acid triggered an unexpected increase in mRNA and protein levels of cytoglobin, the fourth globin in mammals expressed exclusively in hepatic stellate cells. The effect of arundic acid on the level of α-smooth muscle actin mRNA was abrogated in HSCs treated with cytoglobin siRNA. Arundic acid decreased the expression of collagen 1α1 mRNA in LX-2 cells.

CONCLUSION

Arundic acid affects the activation process of hepatic stellate cells via the unexpected induction of cytoglobin.

Expression of S100A4 in renal epithelial neoplasms

Expression of S100A4 has been associated with progression and poor clinical outcome in a variety of malignancies including those of the breast, pancreas, bladder, and thyroid. To date, the expression of S100A4 protein in renal epithelial neoplasms is poorly understood. In this study, we evaluated the expression of S100A4 protein and mRNA in the nontumoral kidney and renal epithelial neoplasms of different types and correlated its expression with patient outcome. The study population included 155 clear cell renal cell carcinomas (cRCC), 22 papillary renal cell carcinomas (pRCC), 13 chromophobe renal cell carcinomas and 13 oncocytomas. In nontumoral kidney, nuclear and cytoplasmic S100A4 staining was detected in the glomerular epithelium and endothelium, distal tubules and collecting ducts, and loops of Henle. A different expression pattern was noted in the various neoplasms. S100A4 expression was significantly increased in the stromal cells in cRCC (83%) and pRCC (73%) compared with paired nontumoral kidney tissue (P<0.001). There was no increased stromal cell expression of S100A4 in oncocytomas and chromophobe carcinomas. Positive epithelial staining was more common in pRCC (58%) than cRCC (11%) (P=0.01). The level of mRNA detected by reverse transcription-polymerase chain reaction was significantly higher in the tumor as opposed to normal tissue in cRCC but not in the other neoplasms (P=0.03). Multivariate analysis revealed that epithelial S100A4 protein expression is an independent poor prognostic factor along with grade and stage only in cRCC (P<0.01). Although S100A4 protein was expressed in a minority of cRCC, its expression was associated with shorter overall patient survival.

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 downregulates filopodia formation through increased dynamic instability

Cell migration requires the initial formation of cell protrusions, lamellipodia and/or filopodia, the attachment of the leading lamella to extracellular cues and the formation and efficient recycling of focal contacts at the leading edge. The small calcium binding EF-hand protein S100A4 has been shown to promote cell motility but the direct molecular mechanisms responsible remain to be elucidated. In this work, we provide new evidences indicating that elevated levels of S100A4 affect the stability of filopodia and prevent the maturation of focal complexes. Increasing the levels of S100A4 in a rat mammary benign tumor derived cell line results in acquired cellular migration on the wound healing scratch assay. At the cellular levels, we found that high levels of S100A4 induce the formation of many nascent filopodia, but that only a very small and limited number of those can stably adhere and mature, as opposed to control cells, which generate fewer protrusions but are able to maintain these into more mature projections. This observation was paralleled by the fact that S100A4 overexpressing cells were unable to establish stable focal adhesions. Using different truncated forms of the S100A4 proteins that are unable to bind to myosin IIA, our data suggests that this newly identified functions of S100A4 is myosin-dependent, providing new understanding on the regulatory functions of S100A4 on cellular migration.

Expression of protein S100A4 is a predictor of recurrence in colorectal cancer

AIM: To investigate the prognostic significance of S100A4 expression in colorectal cancer and its correlation with expression of E-cadherin and p53.

METHODS: A cohort of archival formalin-fixed paraffin-embedded specimens was selected from 127 patients with colorectal cancer who underwent surgical resection between April 2000 and March 2004 at the Department of Surgery, Korea University Guro Hospital. The expression of protein S100A4 was evaluated according to the proportion of positively stained cancer cells. In each case, three core biopsies with a diameter of 2 mm were punched out and positioned in a recipient paraffin array block. Four-μm sections of these tissue array blocks were used for immunohistochemical analysis of protein S100A4, E-cadherin, and p53. Clinicopathological data were based on the original histopathologic reports and clinical records of patients.

RESULTS: In normal colorectal mucosa, protein S100A4 immunoreactivity was clearly absent in both cytoplasm and nucleus. However, positive immunoreactivity of protein S100A4 was detected in 45 (35.4%) of the tumor cases. There was no significant association between positive immunoreactivity of protein S100A4 and clinicopathological parameters such as tumor differentiation or TNM stage, and also no correlation between the reactivity and E-cadherin or p53 expression. However, positive immunoreactivity of protein S100A4 was found to be associated with tumor recurrence (P = 0.004), and was also associated with significantly worse overall survival in the Kaplan-Meyer survival analysis (P = 0.044). After adjustment for tumor differentiation, tumor depth and nodal status, however, it failed to achieve statistical significance (P = 0.067).

CONCLUSION: The expression of protein S100A4 is associated with tumor recurrence and poor overall survival in patients with colorectal cancer.

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.

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.

Self-association of calcium-binding protein S100A4 and metastasis

Elevated levels of the calcium-binding protein S100A4 promote metastasis and in carcinoma cells are associated with reduced survival of cancer patients. S100A4 interacts with target proteins that affect a number of activities associated with metastatic cells. However, it is not known how many of these interactions are required for S100A4-promoted metastasis, thus hampering the design of specific inhibitors of S100A4-induced metastasis. Intracellular S100A4 exists as a homodimer through previously identified, well conserved, predominantly hydrophobic key contacts between the subunits. Here it is shown that mutating just one key residue, phenylalanine 72, to alanine is sufficient to reduce the metastasis-promoting activity of S100A4 to 50% that of the wild type protein, and just 2 or 3 specific mutations reduces the metastasis-promoting activity of S100A4 to less than 20% that of the wild type protein. These mutations inhibit the self-association of S100A4 in vivo and reduce markedly the affinity of S100A4 for at least two of its protein targets, a recombinant fragment of non-muscle myosin heavy chain isoform A, and p53. Inhibition of the self-association of S100 proteins might be a novel means of inhibiting their metastasis-promoting activities.

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.

The basic C-terminal amino acids of calcium-binding protein S100A4 promote metastasis

The calcium-binding protein S100A4 can induce a metastatic phenotype in animal model systems and its expression in various human cancers has been shown to be associated with metastasis and reduced patient survival. Using a series of nested deletion mutants, it is now shown that the two C-terminal lysine residues are required for the enhanced metastasis, invasion and migration abilities that S100A4 confers on cells in a model system of metastasis. Basic C-terminal residues enhance the affinity between S100A4 and its best characterized target, a recombinant C-terminal fragment of non-muscle myosin II heavy chain isoform A (NMMHC-IIA). In wild-type S100A4 protein, the presence of the C-terminal lysine, residue 101, enhances the rate of association between S100A4 and NMMHC-IIA. These results identify the amino acids of S100A4 that are involved in metastasis induction and show that the C-terminal region of S100A4 is a possible target for inhibitors of its metastatic action.

Crystal structure of metastasis-associated protein S100A4 in the active calcium-bound form

S100A4 (metastasin) is a member of the S100 family of calcium-binding proteins that is directly involved in tumorigenesis. Until recently, the only structural information available was the solution NMR structure of the inactive calcium-free form of the protein. Here we report the crystal structure of human S100A4 in the active calcium-bound state at 2.03 A resolution that was solved by molecular replacement in the space group P6(5) with two molecules in the asymmetric unit from perfectly merohedrally twinned crystals. The Ca(2+)-bound S100A4 structure reveals a large conformational change in the three-dimensional structure of the dimeric S100A4 protein upon calcium binding. This calcium-dependent conformational change opens up a hydrophobic binding pocket that is capable of binding to target proteins such as annexin A2, the tumor-suppressor protein p53 and myosin IIA. The structure of the active form of S100A4 provides insight into its interactions with its binding partners and a better understanding of its role in metastasis.

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.

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.

Identification and validation of S100A7 associated with lung squamous cell carcinoma metastasis to brain

To identify potential markers associated with non-small cell lung cancer (NSCLC) metastasis to brain, comparative proteome analysis on two lung squamous cell carcinoma (SCC) cell lines, NCI-H226 and H226Br (the brain metastatic cell line of NCI-H226), was performed using two-dimensional electrophoresis (2-DE) followed by a tandem mass spectrometer with a matrix-assisted laser desorption/ionization (MALDI) source. Twenty differential proteins were identified, of which 6 proteins were up-regulated in H226Br cell compared with NCI-H226 cells, whereas 14 proteins were down-regulated. S100A7 and 14-3-3sigma, two of candidate proteins significantly upregulated and downregulated in H226Br cell, were selected to verify the liability of the differential proteins by Western blot. The results were in accordance with 2-D data. To determine whether S100A7 overexpression is actually associated with SCC metastasis to brain, S100A7 protein was testified in 10 brain metastasis tissues from NSCLC, 38 primary NSCLC tissues including half matched local positive lymph nodes, 5 primary brain tumors and 2 non-cancer brain tissues by immunohistochemistry. Of particular interest to us was that the positive staining of S100A7 could be found in 3/5 (60%) brain metastases tissue from SCC and 8/21 (38%) the primary lung SCC tissues, while no positive staining was observed in the brain metastases tissue from Ad (n=5), the primary adenocarcinoma (Ad) tissues (n=17), the primary brain tumors (n=5), all local positive lymph nodes from the primary NSCLC (n=19) and non-cancer brain tissues (n=2). These findings suggest that S100A7 expression is closely associated with SCC metastasis to brain and may be a potential biomarker for monitoring the development of SCC.

A review of the S100 proteins in cancer

AIM

In the quest to reduce mortality and morbidity from cancer, there is continued effort to identify novel biomarkers to aid in the early detection and the accurate prediction of tumour behaviour. One group of proteins that is emerging as a potentially important group of markers in multiple tumour types is the S100 family. This review summarises the biological and clinical relevance of these proteins in relation to different tumour types.

METHODS

A literature search was performed using the PubMed database and the reference lists of relevant articles. Single case studies were excluded and only reports with a clinical relevance from 1961 to 2007 were included.

RESULTS

The search yielded over 1000 published articles and reports. Important reports and studies were reviewed, screened and tracked for further relevant publications. Only the most relevant publications are discussed with relation to individual members of the S100 family.

CONCLUSION

There is increasing evidence that altered expression of S100 family members is seen in many cancers including breast, lung, bladder, kidney, thyroid, gastric, prostate and oral cancers. S100 proteins are commonly up-regulated in tumours and this is often associated with tumour progression. In contrast S100A2, S100A11 and S100A9 have been documented as tumour suppressors in some cancers but as tumour promoters in others. This demonstrates the complexity of the family and variability of their functions. Although the precise roles of these proteins in cancer is still to be discovered many of the family are associated with promoting metastases through interactions with matrix metalloproteinases or by acting as chemoattractants. There is also evidence that some members can regulate transcription factors such as p53. S100B already has a role in a clinical setting in the diagnosis and therapeutic monitoring of malignant melanoma. As our understanding of this family develops it is likely that many more members will aid the diagnosis, monitoring and potential treatment of cancers in the future.

Focal S100A4 Protein Expression Is an Independent Predictor of Development of Metastatic Disease in Cystectomized Bladder Cancer Patients

OBJECTIVE

The prognosis of patients with apparently localized, operable, muscle-invasive bladder cancer depends to a large extent on the presence or absence of subclinical, microscopic distant metastases at the time of surgery. Expression of the S100A4 protein has been shown to correlate with the risk of metastasis in both animal tumour-model systems and clinical investigations in other tumour types. The purpose of the present study was to investigate the prognostic potential of S100A4 protein expression for predicting distant metastatic relapse in muscle-invasive bladder cancer.

METHODS

We analyzed 108 consecutive patients, treated for transitional cell bladder cancer with preoperative radiotherapy and cystectomy. Pretherapeutic biopsies of the bladder tumours were investigated for immunohistochemical expression of S100A4 protein and results, along with clinical and histopathological data, compared with the pattern of relapses over a 10+ yr follow-up period.

RESULTS

Focal S100A4 protein expression emerged as the only significant independent predictor of distant metastatic relapse and distant metastasis-free survival in multivariate analysis.

CONCLUSION

There is a potential role for this marker in denoting patients with high or low risk of distant relapse independent of clinical stage and grade.

Induction of metastasis by S100P in a rat mammary model and its association with poor survival of breast cancer patients

S100P, an EF-hand calcium-binding protein, has been reported to be associated with the progression of many types of cancers. Transfection of an expression vector for S100P into a benign, nonmetastatic rat mammary cell line causes a 4- to 6-fold increase in its level in all four transformant cell clones. When the resultant transformant cell lines are introduced in turn into the mammary fat pads of syngeneic Furth-Wistar rats, there is a significant 3-fold increase in local muscle invasion and a significant induction of metastasis in 64% to 75% of tumor-bearing animals. In a group of 303 breast cancer patients followed for up to 20 years, antibodies to S100P immunocytochemically stain 161 primary tumors. Survival of patients with S100P-positive carcinomas is significantly worse by about 7-fold than for those with negatively stained carcinomas. There is also a significant association between the class level of immunocytochemical staining of the carcinoma cells and decreased patient survival. Positive staining for S100P is significantly associated with that for two other metastasis-inducing proteins, S100A4 and osteopontin. Patients with tumors that stained positively for both S100P and S100A4 have a significantly reduced survival of 1.1% over patients with either S100 protein alone. Multivariate regression analysis identifies S100P, S100A4, and osteopontin as the most significant independent indicators of death in this group of patients. These results suggest that stratification of patients into groups according to expression of multiple metastasis-inducing proteins may lead to a more accurate prediction of patient survival.

Relaxin Downregulates the Calcium Binding Protein S100A4 in MDA-MB-231 Human Breast Cancer Cells

Expressed in the human breast and in human breast cancer tissues, the heterodimeric peptide hormone relaxin is involved in extracellular matrix turnover. To investigate the role of relaxin in estrogen receptor-alpha negative human breast cancer cells, we established transfectants of the human MDA-MB-231 breast cancer cell line stably overexpressing H2-relaxin (MDA-MB-231/pIRES-EGFP-H2). These transfectants produced and secreted functional relaxin. Our investigations revealed downregulation of mRNA and protein of the calcium binding protein S100A4 (metastasin) in MDA-MB-231/pIRES-EGFP-H2 transfectants, indicating a distinct and novel role for relaxin in estrogen receptor-alpha negative human breast cancer cells.

S100A4 (Mts1) gene overexpression is associated with invasion and metastasis of papillary thyroid carcinoma

Tumour cell invasion and metastasis are the hallmark of malignant neoplasm. S100A4 is a member of small calcium-binding protein family and is involved in the cell proliferation and cancer progression. S100A4 is capable of inducing metastasis in animal models and is associated with aggressive phenotype of human tumours. We previously identified S100A4 as a candidate gene involved in anaplastic thyroid cancer metastasis by microarray analysis. To further determine whether S100A4 overexpression is associated with thyroid tumour invasion and metastasis, in the present study, we examined S100A4 gene expression in six benign multinodular goitres (MNG) and 28 matched samples of adjacent normal thyroid tissue (N), primary (T) and metastatic (M) papillary thyroid carcinomas (PTC) by immunohistochemistry and real-time reverse transcription–polymerase chain reaction (RT-PCR) analysis. This gave us the advantage of directly comparing levels of S100A4 expression within the same genetic background. Using immunohistochemistry, we found that high levels of S100A4 were detected in 24 of 28 (86%) PTC specimens and their local regional lymph node or distant metastases. No S100A4 staining was observed in normal thyroid tissues and simple MNG. However, in MNG coexistent with PTC, moderate focal staining could be found in 11 of 15 MNG adjacent to PTC. The S100A4 was stained more intensely in invading fronts than in central portions of both T and M. Real-time RT–PCR analysis of primary tumours and their matched lymph node metastasis demonstrated that significantly higher S100A4 transcripts were present in metastatic tumours as compared to the primary tumours (P<0.01). These data suggest that overexpression of S100A4 is associated with thyroid tumour invasion and metastasis and it may be a potential target for therapeutic intervention.

Transcript and proteome analysis reveals reduced expression of calgranulins in head and neck squamous cell carcinoma

The calcium-binding proteins of the S100 and the annexin protein families have been implicated in a variety of important physiological functions including membrane remodeling, calcium-related intracellular signaling, cytoskeleton dynamics, tissue homeostasis, and formation of the cornified envelope in differentiating keratinocytes. Deregulated expression of members of these families has been reported in different types of neoplasia and other diseases, but the results were not consistent. Here we have applied a combination of cDNA microarrays, quantitative reverse transcriptase-PCR (qRT-PCR) and surface enhanced laser desorption ionisation-time of flight mass spectrometry (SELDI-TOF MS) to study differential expression of these genes in head and neck squamous cell carcinoma (HNSCC). The calgranulins A and B and annexins 1 and 2 were found to be down-regulated in HNSCC, compared with normal mucosa, at both the mRNA and protein level. Upon validation of the differential gene expression by tissue microarray immunohistochemistry, we detected novel expression patterns of calgranulins A and B both in normal mucosa as well as in HNSCC. In contrast to squamous cancer of skin and other cancers in which the calgranulins were found to be up-regulated, most HNSCC showed reduced and widely deranged staining patterns including heterogeneous nuclear, cytoplasmic and membranous staining, and even enhanced staining in the tumor stroma. These observations suggest that the normal function of the calgranulins A and B in mucosa might be different from that in skin.

Crystal Structure of Human E1 Enzyme and its Complex with a Substrate Analog Reveals the Mechanism of its Phosphatase/Enolase Activity

Enolase-phosphatase E1 (MASA) is a bifunctional enzyme in the ubiquitous methionine salvage pathway that catalyzes the continuous reactions of 2,3-diketo-5-methylthio-1-phosphopentane to yield the aci-reductone metabolite using Mg2+ as cofactor. In this study, we have determined the crystal structure of MASA and its complex with a substrate analog to 1.7A resolution by multi-wavelength anomalous diffraction and molecular replacement techniques, respectively. The structures support the proposed mechanism of phosphatase activity and further suggest the probable mechanism of enolization. We establish a model for substrate binding to describe in detail the enzymatic reaction and the formation of the transition state, which will provide insight into the reaction mechanisms of other enzymes in the same family.

Purification, crystallization and preliminary X-ray diffraction analysis of human enolase-phosphatase E1

Enolase-phosphatase E1 (MASA) is a bifunctional enzyme in the ubiquitous methionine-salvage pathway and catalyzes the continuous reaction of 2,3-diketo-5-methylthio-1-phosphopentane to yield the acireductone metabolite. Recombinant human E1 enzyme has been crystallized using the hanging-drop vapour-diffusion method and diffraction-quality crystals were grown at 291 K using PEG 4000 as precipitant. Diffraction data were collected to 1.7 A resolution from SeMet-derivative crystals at 100 K using synchrotron radiation. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 54.02, b = 57.55, c = 87.32 A. The structure was subsequently solved by the multi-wavelength anomalous diffraction (MAD) phasing method.

The C-terminal region of S100A4 is important for its metastasis-inducing properties

The EF-hand protein, S100A4, binds calcium ions and interacts specifically in vitro with protein targets. Elevated levels of S100A4 have been shown to produce a metastatic phenotype in independent models of breast cancer. The presence of S100A4 in the carcinoma cells of patients with different carcinomas is associated with reduced patient survival. In order to identify the region of the S100A4 molecule that is responsible for its metastasis-inducing properties, specific mutant S100A4 genes and proteins have been produced which contain targeted mutations to the two calcium-binding sites and a deletion of the last 15 amino-acid residues of the protein. The ability of the mutant proteins to bind to a potential specific target in vitro, nonmuscle myosin heavy chain, is correlated with their ability to cause motile, invasive and metastatic phenotypes. Mutation of the C-EF hand of S100A4 virtually abolished calcium binding, and motility/invasion in vitro, abolished interaction with a molecular target, and reduced metastasis induction by 2.5-3-fold. However, deletion of the last 15 amino acids of S100A4 reduced motility/invasion, target binding and metastasis-induction to similar extents as the C-EF-hand mutant, but reduced calcium binding by only 26%. The results suggest that the ability to interact with protein target(s) is important in S100A4-induced metastasis.

Proteins of the S100 family regulate the oligomerization of p53 tumor suppressor

S100B protein is elevated in the brains of patients with early stages of Alzheimer's disease and Down's syndrome. S100A4 is correlated with the development of metastasis. Both proteins bind to p53 tumor suppressor. We found that both S100B and S100A4 bind to the tetramerization domain of p53 (residues 325-355) only when exposed in lower oligomerization states and so they disrupt the tetramerization of p53. In addition, S100B binds to the negative regulatory and nuclear localization domains, which results in a very tight binding to p53 protein sequences that exposed the tetramerization domain in their C terminus. Because the trafficking of p53 depends on its oligomerization state, we suggest that S100B and S100A4 could regulate the subcellular localization of p53. But, the differences in the way these proteins bind to p53 could result in S100B and S1004 having different effects on p53 function in cell-cycle control.

Prognostic Significance of Metastasis-Associated Protein S100A4 (Mts1) in Prostate Cancer Progression and Chemoprevention Regimens in an Autochthonous Mouse Model

Purpose: We recently showed that metastasis-promoting Mts1 gene (S100A4) and protein is overexpressed during progression of prostate cancer in humans. The purpose of this study was to assess the expression of S100A4 during autochthonous prostate cancer progression in transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Because oral consumption of green tea polyphenols (GTP) has been shown to inhibit metastasis and prostate cancer in TRAMP, we further assessed the significance of S100A4 during chemoprevention regimen.

Experimental Design: Male TRAMP mice 8 weeks of age were equally divided into two groups. A freshly prepared 0.1% GTP solution in tap water was supplied thrice a week to experimental animals as the sole source of drinking fluid for 24 weeks, whereas the control group of animals received the same tap water throughout the experiment. The animals were sacrificed at 0, 8, 16, and 24 weeks of GTP feeding and were analyzed for S100A4 and E-cadherin. Additional untreated and treated nontransgenic controls were also included in the study.

Results: With the progression of age and prostate cancer growth in TRAMP mice, an increase in the expression of S100A4 at mRNA and protein level in dorsolateral prostate, but not in nontransgenic mice, occurred. GTP feeding to TRAMP mice resulted in marked inhibition of prostate cancer progression, which was associated with reduction of S100A4 and restoration of E-cadherin.

Conclusions: S100A4 represents a promising marker for prostate cancer progression and could be employed as a biomarker in chemoprevention regimens.

Mutually antagonistic actions of S100A4 and S100A1 on normal and metastatic phenotypes

Increased levels of the homodimeric calcium-binding protein, S100A4, have been shown to cause a metastatic phenotype in at least three independent model systems of breast cancer and its presence in carcinoma cells has been shown to be associated with a reduction in the survival of patients suffering from a range of different cancers. S100A4 has been shown to interact in vitro with another member of the S100 family of proteins, S100A1. The purpose of the present study was to find out whether S100A1 could affect S100A4 function. Fluorescence resonance energy transfer was used to show the interaction of S100A4 and S100A1 in living cells and the binding affinities between S100A4 and S100A1 were determined using a biosensor. S100A1 reduced the S100A4 inhibition of nonmuscle myosin A self-association and phosphorylation in vitro. S100A1 reduced S100A4 induced motility and growth in soft agar and metastasis in vivo. The results show for the first time that interactions between different S100 proteins can affect cancer-related activity, and that the presence of S100A1 protein in carcinoma cells might modulate the effect of S100A4 on their metastatic abilities.

Differential gene expression after complete spinal cord transection in adult rats: an analysis focused on a subchronic post-injury stage

In an attempt to characterize changes in transcription after a sub-chronic spinal cord injury (SCI), we investigated gene expression profiles using cDNA microarray. Among 7523 genes and expressed sequence tags (ESTs) examined, 444 transcripts, including 218 genes and 226 ESTs, were identified to be either up-regulated (373 of 444) or down-regulated (71 of 444) greater than 2.0-fold in the spinal cord at 14 days after a complete spinal transection at the 11th thoracic level in adult rats. Based on their potential function, these differentially expressed genes were categorized into seven classes which include cell division-related protein, channels and receptors, cytoskeletal elements, extracellular matrix proteins, metalloproteinases and inhibitors, growth-associated molecules, metabolism, intracellular transducers and transcription factors, as well as others. Strong expressional changes were found in all classes revealing the complexity and diversity of gene expression profiles following SCI. We verified array results with RT-PCR for eight genes, Northern blotting for nine genes, and in situ hybridization for one gene and immunohistochemistry for four genes. These analyses confirmed, to a large extent, that the array results have accurately reflected the molecular changes occurring at 14 days post-SCI. Importantly, the current study has identified a number of genes, including annexins, heparin-binding growth-associated protein (HB-GAM), P9ka (S100A4), matrix metalloproteinases, and lysozyme, that may shed new light on SCI-related inflammation, neuroprotection, neurite-outgrowth, synaptogenesis, and astrogliosis. In conclusion, the identification of molecular changes using the large-scale microarray analysis may lead to a better understanding of underlying mechanisms, thus, the development of new repair strategies for SCI.

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. Beta-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).

Role of endogenous thrombin in tumor implantation, seeding, and spontaneous metastasis

Tumor/host-generated thrombin (endogenous thrombin) was investigated with tumor growth and metastasis experiments in mice by the use of hirudin, a highly potent specific inhibitor of thrombin. Pretreatment with hirudin inhibited tumor implantation in nude or syngeneic mice, following subcutaneous injection of 2 human and 2 murine tumors. Hirudin induced a considerable lag period in the appearance of tumor growth, compared with phosphate-buffered saline (PBS) treatment, but had no effect on established tumor nodule growth in vivo or on tumor growth in vitro. Hirudin treatment induced central necrosis of the tumor nodule compared with no effect with PBS treatment. Greater protection was noted with longer duration of treatment. Tumor seeding into blood was examined with green fluorescent protein (GFP)-labeled tumor cells. Hirudin inhibited seeding into the blood as well as systemic organs which varied from complete protection to 15- to 32-fold in the blood and 17- to 395-fold in the lung. Hirudin inhibited spontaneous metastases from subcutaneously implanted tumor by reducing the number of tumor nodules in the lungs. Mouse survival in animals injected subcutaneously with highly aggressive 4T1 cells revealed 5 of 5 deaths of PBS-treated animals on day 40 compared with no deaths with hirudin treatment, with prolongation of survival with hirudin treatment of 16 days to more than 31 days. Thus, endogenous thrombin contributes to tumor implantation, seeding, and spontaneous metastasis. A potent antithrombin agent should be of clinical benefit to patients with cancer.

Correlation of S100A4 expression with invasion and metastasis in oral squamous cell carcinoma

S100A4 is known to be involved in cancer cell motility by virtue of its ability to activate non-muscle myosin. In the current study, we investigated the interrelationship of clinico-pathological findings and S100A4 expression in oral squamous cell carcinoma (SCC). The expression of S100A4 was examined immunohistochemically in 41 clinical specimens of oral SCC. S100A4 expression was detected in 11 (26.8%) of 41 cases. Although the expression of S100A4 was not associated with the primary tumor site and degree of differentiation, there was a significant correlation between the increased S100A4-expression and the mode of invasion (p < 0.0001). In addition, the S100A4 status showed a clear correlation with lymph node metastasis (P < 0.01). These results lead us to conclude that S100A4 expression status may be a useful prognostic factor in patients with invasive and metastatic oral SCCs.

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

Causal implication of S100A4 in inducing metastases was convincingly shown previously. However, the mechanisms that associate S100A4 with tumor progression are not well understood. S100A4 protein, as a typical member of the S100 family, exhibits dual, intracellular and extracellular, functions. This work is focused on the extracellular function of S100A4, in particular its involvement in tumor-stroma interplay in VMR (mouse adenocarcinoma cell line) tumor cells, which exhibit stroma-dependent metastatic phenotype. We demonstrated the reciprocal influence of tumor and stroma cells where tumor cells stimulate S100A4 secretion from fibroblasts in culture. In turn, extracellular S100A4 modifies the cytoskeleton and focal adhesions and triggers several other events in tumor cells. We found stabilization of the tumor suppressor protein p53 and modulation of its function. In particular, extracellular S100A4 down-regulates the pro-apoptotic bax and the angiogenesis inhibitor thrombospondin-1 genes. For the first time, we demonstrate here that the S100A4 protein added to the extracellular space strongly stimulates proteolytic activity of VMR cells. This activity most probably is associated with matrix metalloproteinases and, in particular, with matrix metalloproteinase-13. Finally, the application of the recombinant S100A4 protein confers stroma-independent metastatic phenotype on VMR tumor cells. In conclusion, our results indicate that metastasis-inducing S100A4 protein plays a pivotal role in the tumor-stroma environment. S100A4 released either by tumor or stroma cells triggers pro-metastatic cascades in tumor cells.