Tenascin-C regulates angiogenesis in tumor through the regulation of vascular endothelial growth factor expression

Revealing the pathogenesis of keloids based on the status: Active vs inactive

Recently, the pathomechanisms of keloids have been extensively researched using transcriptomic analysis, but most studies did not consider the activity of keloids. We aimed to profile the transcriptomics of keloids according to their clinical activity and location within the keloid lesion, compared with normal and mature scars. Tissue samples were collected (keloid based on its activity (active and inactive), mature scar from keloid patients and normal scar (NS) from non-keloid patients). To reduce possible bias, all keloids assessed in this study had no treatment history and their location was limited to the upper chest or back. Multiomics assessment was performed by using single-cell RNA sequencing and multiplex immunofluorescence. Increased mesenchymal fibroblasts (FBs) was the main feature in keloid patients. Noticeably, the proportion of pro-inflammatory FBs was significantly increased in active keloids compared to inactive ones. To explore the nature of proinflammatory FBs, trajectory analysis was conducted and CCN family associated with mechanical stretch exhibited higher expression in active keloids. For vascular endothelial cells (VECs), the proportion of tip and immature cells increased in keloids compared to NS, especially at the periphery of active keloids. Also, keloid VECs highly expressed genes with characteristics of mesenchymal activation compared to NS, especially those from the active keloid center. Multiomics analysis demonstrated the distinct expression profile of active keloids. Clinically, these findings may provide the future appropriate directions for development of treatment modalities of keloids. Prevention of keloids could be possible by the suppression of mesenchymal activation between FBs and VECs and modulation of proinflammatory FBs may be the key to the control of active keloids.

Biology of Tenascin C and its Role in Physiology and Pathology

Tenascin-C (TNC) is a multimodular extracellular matrix (ECM) protein hexameric with several molecular forms (180-250 kDa) produced by alternative splicing at the pre-mRNA level and protein modifications. The molecular phylogeny indicates that the amino acid sequence of TNC is a well-conserved protein among vertebrates. TNC has binding partners, including fibronectin, collagen, fibrillin-2, periostin, proteoglycans, and pathogens. Various transcription factors and intracellular regulators tightly regulate TNC expression. TNC plays an essential role in cell proliferation and migration. Unlike embryonic tissues, TNC protein is distributed over a few tissues in adults. However, higher TNC expression is observed in inflammation, wound healing, cancer, and other pathological conditions. It is widely expressed in a variety of human malignancies and is recognized as a pivotal factor in cancer progression and metastasis. Moreover, TNC increases both pro-and anti-inflammatory signaling pathways. It has been identified as an essential factor in tissue injuries such as damaged skeletal muscle, heart disease, and kidney fibrosis. This multimodular hexameric glycoprotein modulates both innate and adaptive immune responses regulating the expression of numerous cytokines. Moreover, TNC is an important regulatory molecule that affects the onset and progression of neuronal disorders through many signaling pathways. We provide a comprehensive overview of the structural and expression properties of TNC and its potential functions in physiological and pathological conditions.

Can β-catenin, Tenascin and Fascin be potential biomarkers for personalized therapy in Gastric carcinoma?

Gastric carcinoma (GC) is one of the most prevalent cancers worldwide and the fourth leading cause of cancer-related death. Studying the molecular profile of GC is essential for developing targeted therapies. β-catenin, Tenascin, and Fascin expression are among the molecular abnormalities that are claimed to cause GC progression and chemoresistance. Therefore, they could be used as potential therapeutic targets. This study aimed to evaluate β-catenin, Tenascin, and Fascin expression and their possible roles as prognostic and predictive biomarkers in GC using immunohistochemistry. This retrospective study included 84 GC cases. Tissue microarrays were constructed, followed by β-catenin, Tenascin, and Fascin immunostaining. Their expression was assessed and compared with clinicopathological parameters and survival data. The study results revealed that β-catenin nucleocytoplasmic expression, positive Tenascin, and Fascin expressions were detected in 86.9%, 70%, and 59.5% of cases, respectively. Their expression was significantly associated with poor prognostic parameters, such as deeper tumor invasion, lymph node metastasis, advanced pathological stage, vascular invasion, positive omental nodules, poor response to chemotherapy, and short overall survival. Hence, nucleocytoplasmic β-catenin expression together with Tenascin and Fascin positivity can be potential prognostic and predictive markers, and they can be used as therapeutic targets for GC.

Caveolin-1-dependent tenascin C inclusion in extracellular vesicles is required to promote breast cancer cell malignancy

Background: Elevated expression of CAV1 in breast cancer increases tumor progression. Extracellular vesicles (EVs) from CAV1-expressing MDA-MB-231 breast cancer cells contain Tenascin C (TNC), but the relevance of TNC remained to be defined. Methods: EVs were characterized by nanotracking analysis, microscopy and western blotting. The uptake of EVs by cells was studied using flow cytometry. The effects of EVs on breast cancer cells were tested in migration, invasion, colony formation and in vivo assays. Results: EVs were taken up by cells; however, only those containing TNC promoted invasiveness. In vivo, EVs lacking TNC ceased to promote tumor growth. Conclusion: CAV1 and TNC contained in breast cancer cell-derived EVs were identified as proteins that favor progression of breast cancer.

Matricellular protein tenascin C: Implications in glioma progression, gliomagenesis, and treatment

Matricellular proteins are nonstructural extracellular matrix components that are expressed at low levels in normal adult tissues and are upregulated during development or under pathological conditions. Tenascin C (TNC), a matricellular protein, is a hexameric and multimodular glycoprotein with different molecular forms that is produced by alternative splicing and post-translational modifications. Malignant gliomas are the most common and aggressive primary brain cancer of the central nervous system. Despite continued advances in multimodal therapy, the prognosis of gliomas remains poor. The main reasons for such poor outcomes are the heterogeneity and adaptability caused by the tumor microenvironment and glioma stem cells. It has been shown that TNC is present in the glioma microenvironment and glioma stem cell niches, and that it promotes malignant properties, such as neovascularization, proliferation, invasiveness, and immunomodulation. TNC is abundantly expressed in neural stem cell niches and plays a role in neurogenesis. Notably, there is increasing evidence showing that neural stem cells in the subventricular zone may be the cells of origin of gliomas. Here, we review the evidence regarding the role of TNC in glioma progression, propose a potential association between TNC and gliomagenesis, and summarize its clinical applications. Collectively, TNC is an appealing focus for advancing our understanding of gliomas.

Revisiting the Tenascins: Exploitable as Cancer Targets?

For their full manifestation, tumors require support from the surrounding tumor microenvironment (TME), which includes a specific extracellular matrix (ECM), vasculature, and a variety of non-malignant host cells. Together, these components form a tumor-permissive niche that significantly differs from physiological conditions. While the TME helps to promote tumor progression, its special composition also provides potential targets for anti-cancer therapy. Targeting tumor-specific ECM molecules and stromal cells or disrupting aberrant mesenchyme-cancer communications might normalize the TME and improve cancer treatment outcome. The tenascins are a family of large, multifunctional extracellular glycoproteins consisting of four members. Although each have been described to be expressed in the ECM surrounding cancer cells, tenascin-C and tenascin-W are currently the most promising candidates for exploitability and clinical use as they are highly expressed in various tumor stroma with relatively low abundance in healthy tissues. Here, we review what is known about expression of all four tenascin family members in tumors, followed by a more thorough discussion on tenascin-C and tenascin-W focusing on their oncogenic functions and their potential as diagnostic and/or targetable molecules for anti-cancer treatment purposes.

The role of Tenascin-C in HIV associated pre-eclampsia

INTRODUCTION

Pre-eclampsia (PE) accounts for 14.8% of maternal deaths in South Africa. Tenascin C (TN-C) is an anti-inflammatory cytokine expressed in the extracellular matrix and may be dysregulated in the hyperinflammatory PE microenvironment.

MATERIAL AND METHODS

This study examined serum TN-C in normotensive pregnant (n = 36) and pre-eclamptic (n = 36) HIV positive and negative women using an immunoassay.

RESULTS

TN-C was significantly upregulated in PE vs normotensive pregnant women (p = 0.0075) and HIV-positive vs negative pregnant women (p = 0.0009). TN-C levels across all groups was statistically different (p < 0.0001).

CONCLUSION

This study demonstrates an elevation of TN-C in HIV-associated PE. The potential benefit of TN-C as a biomarker to detect PE development requires investigation.

Increased Tenascin C, Osteopontin and HSP90 Levels in Plasmatic Small Extracellular Vesicles of Pediatric ALK-Positive Anaplastic Large Cell Lymphoma: New Prognostic Biomarkers?

Over the past 15 years, several biological and pathological characteristics proved their significance in pediatric anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphoma (ALCL) prognostic stratification. However, the identification of new non-invasive disease biomarkers, relying on the most important disease mechanisms, is still necessary. In recent years, plasmatic circulating small extracellular vesicles (S-EVs) gathered great importance both as stable biomarker carriers and active players in tumorigenesis. In the present work, we performed a comprehensive study on the proteomic composition of plasmatic S-EVs of pediatric ALCL patients compared to healthy donors (HDs). By using a mass spectrometry-based proteomics approach, we identified 50 proteins significantly overrepresented in S-EVs of ALCL patients. Gene Ontology enrichment analysis disclosed cellular components and molecular functions connected with S-EV origin and vesicular trafficking, whereas cell adhesion, glycosaminoglycan metabolic process, extracellular matrix organization, collagen fibril organization and acute phase response were the most enriched biological processes. Of importance, consistently with the presence of nucleophosmin (NPM)-ALK fusion protein in ALCL cells, a topological enrichment analysis based on Reactome- and Kyoto Encyclopedia of Genes and Genomes (KEGG)-derived networks highlighted a dramatic increase in proteins of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in ALCL S-EVs, which included heat shock protein 90-kDa isoform alpha 1 (HSP90AA1), osteopontin (SPP1/OPN) and tenascin C (TNC). These results were validated by Western blotting analysis on a panel of ALCL and HD cases. Further research is warranted to better define the role of these S-EV proteins as diagnostic and, possibly, prognostic parameters at diagnosis and for ALCL disease monitoring.

The Role of Tenascin-C in Tissue Injury and Repair After Stroke

Stroke is still one of the most common causes for mortality and morbidity worldwide. Following acute stroke onset, biochemical and cellular changes induce further brain injury such as neuroinflammation, cell death, and blood-brain barrier disruption. Matricellular proteins are non-structural proteins induced by many stimuli and tissue damage including stroke induction, while its levels are generally low in a normal physiological condition in adult tissues. Currently, a matricellular protein tenascin-C (TNC) is considered to be an important inducer to promote neuroinflammatory cascades and the resultant pathology in stroke. TNC is upregulated in cerebral arteries and brain tissues including astrocytes, neurons, and brain capillary endothelial cells following subarachnoid hemorrhage (SAH). TNC may be involved in blood-brain barrier disruption, neuronal apoptosis, and cerebral vasospasm via the activation of mitogen-activated protein kinases and nuclear factor-kappa B following SAH. In addition, post-SAH TNC levels in cerebrospinal fluid predicted the development of delayed cerebral ischemia and angiographic vasospasm in clinical settings. On the other hand, TNC is reported to promote fibrosis and exert repair effects for an experimental aneurysm via macrophages-induced migration and proliferation of smooth muscle cells. The authors review TNC-induced inflammatory signal cascades and the relationships with other matricellular proteins in stroke-related pathology.

Pleiotropic Role of Tenascin-C in Central Nervous System Diseases: From Basic to Clinical Applications

The extracellular matrix is composed of a variety of macromolecular substances secreted by cells, which form a complex network that supports and connects tissue structures, regulates the morphogenesis of tissues, and maintains the physiological activities of cells. Tenascin-C, a secreted extracellular matrix glycoprotein, is abundantly expressed after exposure to pathological stimuli. It plays an important regulatory role in brain tumors, vascular diseases, and neurodegenerative diseases by mediating inflammatory responses, inducing brain damage, and promoting cell proliferation, migration, and angiogenesis through multiple signaling pathways. Therefore, tenascin-C may become a potential therapeutic target for intracranial diseases. Here, we review and discuss the latest literature regarding tenascin-C, and we comprehensively explain the role and clinical significance of tenascin-C in intracranial diseases.

Matrix-Targeting Immunotherapy Controls Tumor Growth and Spread by Switching Macrophage Phenotype

The interplay between cancer cells and immune cells is a key determinant of tumor survival. Here, we uncovered how tumors exploit the immunomodulatory properties of the extracellular matrix to create a microenvironment that enables their escape from immune surveillance. Using orthotopic grafting of mammary tumor cells in immunocompetent mice and autochthonous models of breast cancer, we discovered how tenascin-C, a matrix molecule absent from most healthy adult tissues but expressed at high levels and associated with poor patient prognosis in many solid cancers, controls the immune status of the tumor microenvironment. We found that, although host-derived tenascin-C promoted immunity via recruitment of proinflammatory, antitumoral macrophages, tumor-derived tenascin-C subverted host defense by polarizing tumor-associated macrophages toward a pathogenic, immune-suppressive phenotype. Therapeutic monoclonal antibodies that blocked tenascin-C activation of Toll-like receptor 4 reversed this phenotypic switch in vitro and reduced tumor growth and lung metastasis in vivo, providing enhanced benefit in combination with anti-PD-L1 over either treatment alone. Combined tenascin-C:macrophage gene-expression signatures delineated a significant survival benefit in people with breast cancer. These data revealed a new approach to targeting tumor-specific macrophage polarization that may be effective in controlling the growth and spread of breast tumors.

Cell Intrinsic and Extrinsic Mechanisms of Caveolin-1-Enhanced Metastasis

Caveolin-1 (CAV1) is a scaffolding protein with a controversial role in cancer. This review will initially discuss earlier studies focused on the role as a tumor suppressor before elaborating subsequently on those relating to function of the protein as a promoter of metastasis. Different mechanisms are summarized illustrating how CAV1 promotes such traits upon expression in cancer cells (intrinsic mechanisms). More recently, it has become apparent that CAV1 is also a secreted protein that can be included into exosomes where it plays a significant role in determining cargo composition. Thus, we will also discuss how CAV1 containing exosomes from metastatic cells promote malignant traits in more benign recipient cells (extrinsic mechanisms). This ability appears, at least in part, attributable to the transfer of specific cargos present due to CAV1 rather than the transfer of CAV1 itself. The evolution of how our perception of CAV1 function has changed since its discovery is summarized graphically in a time line figure.

Internal Affairs: Tenascin-C as a Clinically Relevant, Endogenous Driver of Innate Immunity

To protect against danger, the innate immune system must promptly and accurately sense alarm signals, and mount an appropriate response to restore homeostasis. One endogenous trigger of immunity is tenascin-C, a large hexameric protein of the extracellular matrix. Upregulated upon tissue injury and cellular stress, tenascin-C is expressed during inflammation and tissue remodeling, where it influences cellular behavior by interacting with a multitude of molecular targets, including other matrix components, cell surface proteins, and growth factors. Here, we discuss how these interactions confer upon tenascin-C distinct immunomodulatory capabilities that make this matrix molecule necessary for efficient tissue repair. We also highlight in vivo studies that provide insight into the consequences of misregulated tenascin-C expression on inflammation and fibrosis during a wide range of inflammatory diseases. Finally, we examine how its unique expression pattern and inflammatory actions make tenascin-C a viable target for clinical exploitation in both diagnostic and therapeutic arenas.

Tenascin-c renders a proangiogenic phenotype in macrophage via annexin II

Tenascin-c is an extracellular matrix glycoprotein, the expression of which relates to the progression of atherosclerosis, myocardial infarction and heart failure. Annexin II acts as a cell surface receptor of tenascin-c. This study aimed to delineate the role of tenascin-c and annexin II in macrophages presented in atherosclerotic plaque. Animal models with atherosclerotic lesions were established using ApoE-KO mice fed with high-cholesterol diet. The expression of tenascin-c and annexin II in atherosclerotic lesions was determined by qRT-PCR, Western blot and immunohistochemistry analysis. Raw 264.7 macrophages and human primary macrophages were exposed to 5, 10 and 15 μg/ml tenascin-c for 12 hrs. Cell migration as well as the proangiogenic ability of macrophages was examined. Additionally, annexin II expression was delineated in raw 264.7 macrophages under normal condition (20% O₂ ) for 12 hrs or hypoxic condition (1% O₂ ) for 6-12 hrs. The expression of tenascin-c and annexin II was markedly augmented in lesion aorta. Tenascin-c positively regulated macrophage migration, which was dependent on the expression of annexin II in macrophages. VEGF release from macrophages and endothelial tube induction by macrophage were boosted by tenascin-c and attenuated by annexin II blocking. Furthermore, tenascin-c activated Akt/NF-κB and ERK signalling through annexin II. Lastly, hypoxia conditioning remarkably facilitates annexin II expression in macrophages through hypoxia-inducible factor (HIF)-1α but not HIF-2α. In conclusion, tenascin-c promoted macrophage migration and VEGF expression through annexin II, the expression of which was modulated by HIF-1α.

Tenascin-C secreted by transdifferentiated retinal pigment epithelial cells promotes choroidal neovascularization via integrin αV

Tenascin-C is expressed in choroidal neovascular (CNV) membranes in eyes with age-related macular degeneration (AMD). However, its role in the pathogenesis of CNV remains to be elucidated. Here we investigated the role of tenascin-C in CNV formation. In immunofluorescence analyses, tenascin-C co-stained with α-SMA, pan-cytokeratin, CD31, CD34, and integrin α_V in the CNV membranes of patients with AMD and a mouse model of laser-induced CNV. A marked increase in the expression of tenascin-C mRNA and protein was observed 3 days after laser photocoagulation in the mouse CNV model. Tenascin-C was also shown to promote proliferation and inhibit adhesion of human retinal pigment epithelial (hRPE) cells in vitro. Moreover, tenascin-C promoted proliferation, adhesion, migration, and tube formation in human microvascular endothelial cells (HMVECs); these functions were, however, blocked by cilengitide, an integrin α_V inhibitor. Exposure to TGF-β2 increased tenascin-C expression in hRPE cells. Conditioned media harvested from TGF-β2-treated hRPE cell cultures enhanced HMVEC proliferation and tube formation, which were inhibited by pretreatment with tenascin-C siRNA. The CNV volume was significantly reduced in tenascin-C knockout mice and tenascin-C siRNA-injected mice. These findings suggest that tenascin-C is secreted by transdifferentiated RPE cells and promotes the development of CNV via integrin α_V in a paracrine manner. Therefore, tenascin-C could be a potential therapeutic target for the inhibition of CNV development associated with AMD.

Distinct microenvironmental cues stimulate divergent TLR4-mediated signaling pathways in macrophages

Macrophages exhibit a phenotypic plasticity that enables them to orchestrate specific immune responses to distinct threats. The microbial product lipopolysaccharide (LPS) and the extracellular matrix glycoprotein tenascin-C are released during bacterial infection and tissue injury, respectively, and both activate Toll-like receptor 4 (TLR4). We found that these two TLR4 ligands stimulated distinct signaling pathways in macrophages, resulting in cells with divergent phenotypes. Although macrophages activated by LPS or tenascin-C displayed some common features, including activation of nuclear factor κB and mitogen-activated protein kinase signaling and cytokine synthesis, each ligand stimulated the production of different subsets of cytokines and generated different phosphoproteomic signatures. Moreover, tenascin-C promoted the generation of macrophages that exhibited increased synthesis and phosphorylation of extracellular matrix components, whereas LPS stimulated the production of macrophages that exhibited an enhanced capacity to degrade the matrix. These data reveal how the activation of one pattern recognition receptor by different microenvironmental cues generates macrophage with distinct phenotypes.

The extracellular matrix niche microenvironment of neural and cancer stem cells in the brain

Numerous studies demonstrated that neural stem cells and cancer stem cells (NSCs/CSCs) share several overlapping characteristics such as self-renewal, multipotency and a comparable molecular repertoire. In addition to the intrinsic cellular properties, NSCs/CSCs favor a similar environment to acquire and maintain their characteristics. In the present review, we highlight the shared properties of NSCs and CSCs in regard to their extracellular microenvironment called the NSC/CSC niche. Moreover, we point out that extracellular matrix (ECM) molecules and their complementary receptors influence the behavior of NSCs/CSCs as well as brain tumor progression. Here, we focus on the expression profile and functional importance of the ECM glycoprotein tenascin-C, the chondroitin sulfate proteoglycan DSD-1-PG/phosphacan but also on other important glycoprotein/proteoglycan constituents. Within this review, we specifically concentrate on glioblastoma multiforme (GBM). GBM is the most common malignant brain tumor in adults and is associated with poor prognosis despite intense and aggressive surgical and therapeutic treatment. Recent studies indicate that GBM onset is driven by a subpopulation of CSCs that display self-renewal and recapitulate tumor heterogeneity. Based on the CSC hypothesis the cancer arises just from a small subpopulation of self-sustaining cancer cells with the exclusive ability to self-renew and maintain the tumor. Besides the fundamental stem cell properties of self-renewal and multipotency, GBM stem cells share further molecular characteristics with NSCs, which we would like to review in this article.

Contribution of Human Fibroblasts and Endothelial Cells to the Hallmarks of Inflammation as Determined by Proteome Profiling

In order to systematically analyze proteins fulfilling effector functionalities during inflammation, here we present a comprehensive proteome study of inflammatory activated primary human endothelial cells and fibroblasts. Cells were stimulated with interleukin 1-β and fractionated in order to obtain secreted, cytoplasmic and nuclear protein fractions. Proteins were submitted to a data-dependent bottom up analytical platform using a QExactive orbitrap and the MaxQuant software for protein identification and label-free quantification. Results were further combined with similarly generated data previously obtained from the analysis of inflammatory activated peripheral blood mononuclear cells. Applying a false discovery rate of less than 0.01 at both, peptide and protein level, a total of 8370 protein groups assembled from 117,599 peptides was identified; mass spectrometry data have been made fully accessible via ProteomeXchange with identifier PXD003406 to PXD003417.Comparative proteome analysis allowed us to determine common and cell type-specific inflammation signatures comprising novel candidate marker molecules and related expression patterns of transcription factors. Cardinal features of inflammation such as interleukin 1-β processing and the interferon response differed substantially between the investigated cells. Furthermore, cells also exerted similar inflammation-related tasks; however, by making use of different sets of proteins. Hallmarks of inflammation thus emerged, including angiogenesis, extracellular matrix reorganization, adaptive and innate immune responses, oxidative stress response, cell proliferation and differentiation, cell adhesion and migration in addition to monosaccharide metabolic processes, representing both, common and cell type-specific responsibilities of cells during inflammation.

Tenascin C in metastasis: A view from the invasive front

The extracellular matrix protein tenascin C (TNC) is a large glycoprotein expressed in connective tissues and stem cell niches. TNC over-expression is repeatedly observed in cancer, often at the invasive tumor front, and is associated with poor clinical outcome in several malignancies. The link between TNC expression and poor survival in cancer patients suggests a role for TNC in metastatic progression, which is responsible for the majority of cancer related deaths. Indeed, functional studies using mouse models are revealing new roles of TNC in cancer progression and underscore its important contribution to the development of metastasis. TNC has a pleiotropic role in advancing metastasis by promoting migratory and invasive cell behavior, angiogenesis and cancer cell viability under stress. TNC is an essential component of the metastatic niche and modulates stem cell signaling within the niche. This may be crucial for the fitness of disseminated cancer cells confronted with a foreign environment in secondary organs, that can exert a strong selective pressure on invading cells. TNC is a compelling example of how an extracellular matrix protein can provide a molecular context that is imperative to cancer cell fitness in metastasis.

Role of tenascins in the ECM of gliomas

Tenascins are a family of extracellular matrix molecules that are mainly expressed in embryonic development and down-regulated in adulthood. A re-expression in the adult occurs under pathological conditions such as inflammation, regeneration or neoplasia. As the most prominent member of the tenascin family, TN-C, is highly expressed in glioma tissue and rising evidence suggests that TN-C plays a crucial role in cell migration or invasion - the most fatal characteristics of glioma - also the other members of this protein family have been investigated with regard to their impact on glioma biology. For all tenascins correlations between the expression levels of the different family members and the degree of malignancy and invasiveness of glial tumors could be detected. Overall, the former and recent results in the research on glioma and tenascins point at distinct roles of each of the molecules in glioma biology and the devastating properties of these tumors.

Tumor microenvironment tenascin-C promotes glioblastoma invasion and negatively regulates tumor proliferation

BACKGROUND

Glioblastoma (GBM) is the most frequent and aggressive primary brain tumor in adults. Recent research on cancer stroma indicates that the brain microenvironment plays a substantial role in tumor malignancy and treatment responses to current antitumor therapy. In this work, we have investigated the effect of alterations in brain tumor extracellular matrix tenascin-C (TNC) on brain tumor growth patterns including proliferation and invasion.

METHODS

Since intracranial xenografts from patient-derived GBM neurospheres form highly invasive tumors that recapitulate the invasive features demonstrated in human patients diagnosed with GBM, we studied TNC gain-of-function and loss-of function in these GBM neurospheres in vitro and in vivo.

RESULTS

TNC loss-of-function promoted GBM neurosphere cell adhesion and actin cytoskeleton organization. Yet, TNC loss-of-function or exogenous TNC had no effect on GBM neurosphere cell growth in vitro. In animal models, decreased TNC in the tumor microenvironment was accompanied by decreased tumor invasion and increased tumor proliferation, suggesting that TNC regulates the "go-or-grow" phenotypic switch of glioma in vivo. We demonstrated that decreased TNC in the tumor microenvironment modulated behaviors of stromal cells including endothelial cells and microglia, resulting in enlarged tumor blood vessels and activated microglia in tumors. We further demonstrated that tumor cells with decreased TNC expression are sensitive to anti-proliferative treatment in vitro.

CONCLUSION

Our findings suggest that detailed understanding of how TNC in the tumor microenvironment influences tumor behavior and the interactions between tumor cells and surrounding nontumor cells will benefit novel combinatory antitumor strategies to treat malignant brain tumors.

Temporal expression of tenascin-C and type I collagen in response to gonadotropins in the immature rat ovary

Ovarian morphogenesis and physiology in mammals take place in the context of hormones, paracrine factors and extracellular matrix molecules. Both fibrillar type I collagen and the multidomain tenascin-C are matrix molecules capable of modulating the behavior of both normal and neoplastic cells in many organs. Therefore, the objective of this qualitative study was to simultaneously examine the distribution of both tenascin-C and type I collagen in ovarian follicles and corpora lutea induced to develop in response to gonadotropin treatments. In preantral follicles both matrix proteins were present in the focimatrix, theca externa and the interstitium. Equine gonadotropin induced the appearance of both proteins in the theca interna. Subsequent to administration with human chorionic gonadotropin, tenascin-C appearance in the thecal capillaries preceded type I collagen expression. Tenascin-C was also observed in the capillaries of functional and regressing corpora lutea, while type I collagen was predominantly present in the interstitium and tunica albuginea. Western blots showed both an increase in and degradation of tenascin-C in the regressing corpora lutea. The ovarian surface epithelium also showed immunoreactivity for both tenascin-C and type I collagen. The study reveals that tenascin-C and type I collagen may participate in the morphogenesis of ovarian follicles, and in the formation and regression of corpora lutea.

Quantitative proteomic analysis reveals effects of epidermal growth factor receptor (EGFR) on invasion-promoting proteins secreted by glioblastoma cells

Glioblastoma multiforme is a highly invasive and aggressive brain tumor with an invariably poor prognosis. The overexpression of epidermal growth factor receptor (EGFR) is a primary influencer of invasion and proliferation in tumor cells and the constitutively active EGFRvIII mutant, found in 30-65% of Glioblastoma multiforme, confers more aggressive invasion. To better understand how EGFR contributes to tumor aggressiveness, we investigated the effect of EGFR on the secreted levels of 65 rationally selected proteins involved in invasion. We employed selected reaction monitoring targeted mass spectrometry using stable isotope labeled internal peptide standards to quantity proteins in the secretome from five GBM (U87) isogenic cell lines in which EGFR, EGFRvIII, and/or PTEN were expressed. Our results show that cell lines with EGFR overexpression and constitutive EGFRvIII expression differ remarkably in the expression profiles for both secreted and intracellular signaling proteins, and alterations in EGFR signaling result in reproducible changes in concentrations of secreted proteins. Furthermore, the EGFRvIII-expressing mutant cell line secretes the majority of the selected invasion-promoting proteins at higher levels than other cell lines tested. Additionally, the intracellular and extracellular protein measurements indicate elevated oxidative stress in the EGFRvIII-expressing cell line. In conclusion, the results of our study demonstrate that EGFR signaling has a significant effect on the levels of secreted invasion-promoting proteins, likely contributing to the aggressiveness of Glioblastoma multiforme. Further characterization of these proteins may provide candidates for new therapeutic strategies and targets as well as biomarkers for this aggressive disease.

Tenascin-C downregulates wnt inhibitor dickkopf-1, promoting tumorigenesis in a neuroendocrine tumor model

The extracellular matrix molecule tenascin-C (TNC) is a major component of the cancer-specific matrix, and high TNC expression is linked to poor prognosis in several cancers. To provide a comprehensive understanding of TNC's functions in cancer, we established an immune-competent transgenic mouse model of pancreatic β-cell carcinogenesis with varying levels of TNC expression and compared stochastic neuroendocrine tumor formation in abundance or absence of TNC. We show that TNC promotes tumor cell survival, the angiogenic switch, more and leaky vessels, carcinoma progression, and lung micrometastasis. TNC downregulates Dickkopf-1 (DKK1) promoter activity through the blocking of actin stress fiber formation, activates Wnt signaling, and induces Wnt target genes in tumor and endothelial cells. Our results implicate DKK1 downregulation as an important mechanism underlying TNC-enhanced tumor progression through the provision of a proangiogenic tumor microenvironment.

The niche under siege: novel targets for metastasis therapy

Metastasis is an inefficient process and most cancer cells fail to colonize secondary sites. There are several possible reasons for this. First, the nature of the infiltrating cells is important as a small population of cancer stem cells has been shown to have exclusive metastasis-initiating potential. Secondly, supportive niches are required to promote the outgrowth of disseminated tumour cells. Such niches are either produced prior to the arrival of cancer cells in the target organ or are induced ad hoc upon cell infiltration. Components of the extracellular matrix (ECM) have been found to play a role in establishing these niches. This has highlighted the importance of the ECM for metastatic progression, and suggests that such components may provide alternative targets for treatment of metastatic disease.

Increased tenascin C and Toll-like receptor 4 levels in visceral adipose tissue as a link between inflammation and extracellular matrix remodeling in obesity

CONTEXT

Obesity is associated with an altered inflammatory and extracellular matrix (ECM) profile. Tenascin C (TNC) is an ECM glycoprotein with proinflammatory effects.

OBJECTIVE

We aimed to explore the expression levels of TNC in adipose tissue analyzing the contribution of adipocytes and stromovascular fraction cells (SVFC) as well as its impact on inflammation and ECM regulation. We also analyzed the effect of the stimulation with TNF-α and lipopolysaccharide (LPS) on both SVFC and adipocytes.

PATIENTS AND METHODS

Samples obtained from 75 subjects were used in the study. Expression levels of TNC, TLR4, MMP2, and MMP9 were analyzed in visceral adipose tissue (VAT) as well as in both adipocytes and SVFC. In addition, Tnc expression was measured in two mice models of obesity.

RESULTS

We show, for the first time, that VAT expression levels of TNC are increased in normoglycemic and type 2 diabetic obese patients (P<0.01) as well as in obese patients with nonalcoholic steatohepatitis (P<0.01). Furthermore, expression levels of Tnc in epididymal adipose tissue from two different mice models of obesity were significantly increased (P<0.01). TNC and TLR4 were mainly expressed by SVFC, and its expression was significantly enhanced (P<0.01) by TNF-α treatment. LPS treatment also increased mRNA levels of TNC. Moreover, the addition of exogenous TNC induced (P<0.05) TLR4 and CCL2 mRNA expression in human adipocyte cultures.

CONCLUSIONS

These findings indicate that TNC is involved in the etiopathology of obesity via visceral adipose tissue inflammation representing a link with ECM remodeling.

The role of stromal myofibroblast and extracellular matrix in tumor angiogenesis

Tumor angiogenesis, the building of blood vessels in an expanding tumor mass, is an elegantly coordinated process that dictates tumor growth and progression. Stromal components of the tumor microenvironment, such as myofibroblasts and the extracellular matrix, collaborate with tumor cells in regulating development. Such myofibroblasts and the extracellular matrix have ever-expanding roles in the angiogenic process as well. This review summarizes how stromal myofibroblasts and the extracellular matrix can modulate tumor angiogenesis, highlighting recent findings.

How do tenascins influence the birth and life of a malignant cell?

Tenascins are large glycoproteins found in embryonic and adult extracellular matrices. Of the four family members, two have been shown to be overexpressed in the microenvironment of solid tumours: tenascin-C and tenascin-W. The regular presence of these proteins in tumours suggests a role in tumourigenesis, which has been investigated intensively for tenascin-C and recently for tenascin-W as well. In this review, we follow a malignant cell starting from its birth through its potential metastatic journey and describe how tenascin-C and tenascin-W contribute to these successive steps of tumourigenesis. We consider the importance of the mechanical aspect in tenascin signalling. Furthermore, we discuss studies describing tenascin-C as an important component of stem cell niches and present examples reporting its role in cancer therapy resistance.

Matricellular proteins: a sticky affair with cancers

The multistep process of metastasis is a major hallmark of cancer progression involving the cointeraction and coevolution of the tumor and its microenvironment. In the tumor microenvironment, tumor cells and the surrounding stromal cells aberrantly secrete matricellular proteins, which are a family of nonstructural proteins in the extracellular matrix (ECM) that exert regulatory roles via a variety of molecular mechanisms. Matricellular proteins provide signals that support tumorigenic activities characteristic of the metastastic cascade such as epithelial-to-mesenchymal (EMT) transition, angiogenesis, tumor cell motility, proliferation, invasion, evasion from immune surveillance, and survival of anoikis. Herein, we review the current understanding of the following matricellular proteins and highlight their pivotal and multifacted roles in metastatic progression: angiopoietin-like protein 4 (ANGPTL4), CCN family members cysteine-rich angiogenic inducer 61 (Cyr61/CCN1) and CCN6, osteopontin (OPN), secreted protein acidic and rich in cysteine (SPARC), tenascin C (TNC), and thrombospondin-1 and -2 (TSP1, TSP2). Insights into the signaling mechanisms resulting from the interaction of these matricellular proteins and their respective molecular partner(s), as well as their subsequent contribution to tumor metastasis, are discussed. In addition, emerging evidences of their promising potential as therapeutic options and/or targets in the treatment of cancer are also highlighted.

A proteome comparison between physiological angiogenesis and angiogenesis in glioblastoma

The molecular pathways involved in neovascularization of regenerating tissues and tumor angiogenesis resemble each other. However, the regulatory mechanisms of neovascularization under neoplastic circumstances are unbalanced leading to abnormal protein expression patterns resulting in the formation of defective and often abortive tumor vessels. Because gliomas are among the most vascularized tumors, we compared the protein expression profiles of proliferating vessels in glioblastoma with those in tissues in which physiological angiogenesis takes place. By using a combination of laser microdissection and LTQ Orbitrap mass spectrometry comparisons of protein profiles were made. The approach yielded 29 and 12 differentially expressed proteins for glioblastoma and endometrium blood vessels, respectively. The aberrant expression of five proteins, i.e. periostin, tenascin-C, TGF-beta induced protein, integrin alpha-V, and laminin subunit beta-2 were validated by immunohistochemistry. In addition, pathway analysis of the differentially expressed proteins was performed and significant differences in the usage of angiogenic pathways were found. We conclude that there are essential differences in protein expression profiles between tumor and normal physiological angiogenesis.

Tenascin-C: a novel mediator of hepatic ischemia and reperfusion injury

Hepatic ischemia/reperfusion (IRI) injury remains a major challenge in clinical orthotopic liver transplantation (OLT). Tenascin-C (Tnc) is an extracellular matrix protein (ECM) involved in various aspects of immunity and tissue injury. Using a Tnc-deficient mouse model, we present data that suggest an active role for Tnc in liver IRI. We show that Tnc-deficient mice have a reduction in liver damage and a significant improvement in liver regeneration after IRI. The inability of Tnc(-/-) mice to express Tnc significantly reduced the levels of active caspase-3/transferase-mediated dUTP nick end-labeling (TUNEL) apoptotic markers and enhanced the expression of the proliferation cell nuclear antigen (PCNA) after liver IRI. The lack of Tnc expression resulted in impaired leukocyte recruitment and decreased expressions of interleukin (IL)-1β, IL-6, and CXCL2 after liver reperfusion. Tnc-deficient livers were characterized by altered expression patterns of vascular adhesion molecules, such as vascular cell adhesion molecule-1 and platelet endothelial cell adhesion molecule-1 post-IRI. Moreover, matrix metalloproteinase-9 (MMP-9) synthesis, which facilitates leukocyte transmigration across vascular barriers in liver IRI, was markedly down-regulated in the absence of Tnc. We also show that Tnc is capable of inducing MMP-9 expression in isolated neutrophils through Toll-like receptor 4. Therefore, our data suggest that Tnc is a relevant mediator of the pathogenic events underlying liver IRI. The data also support the view that studies aimed at further understanding how newly synthesized ECM molecules, such as Tnc, participate in inflammatory responses are needed to improve therapeutic approaches in liver IRI.

Advances in tenascin-C biology

Tenascin-C is an extracellular matrix glycoprotein that is specifically and transiently expressed upon tissue injury. Upon tissue damage, tenascin-C plays a multitude of different roles that mediate both inflammatory and fibrotic processes to enable effective tissue repair. In the last decade, emerging evidence has demonstrated a vital role for tenascin-C in cardiac and arterial injury, tumor angiogenesis and metastasis, as well as in modulating stem cell behavior. Here we highlight the molecular mechanisms by which tenascin-C mediates these effects and discuss the implications of mis-regulated tenascin-C expression in driving disease pathology.

A prolonged and exaggerated wound response with elevated ODC activity mimics early tumor development

Induction of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, in ODC transgenic skin stimulates epidermal proliferation but not hyperplasia, activates underlying stromal cells and promotes skin tumorigenesis following a single subthreshold dose of a carcinogen. Because chronic wounds are a well-recognized risk factor for skin cancer, we investigated the response to a tissue remodeling event in normal skin that is abraded to remove only the epidermal layer in K6/ODC transgenic (follicular ODC expression) and in inducible ODCER transgenic mice (suprabasal ODC expression). When regenerative epidermal hyperplasia was resolved in normal littermates following abrasion, ODC transgenic mice exhibited progressive epidermal hyperplasia with formation of benign tumor growths and maintained an increased epidermal proliferation index and activation of translation-associated proteins at abrasion sites. The epidermal hyperplasia and tumor-like growth was accompanied by activation of underlying stromal cells and prolonged infiltration of inflammatory cells. Treatment with the anti-inflammatory agent dexamethasone did not reduce the high proliferative index in the regenerated epidermis but dramatically reduced the epidermal hyperplasia and prevented the wound-induced tumor growths in abraded ODCER skin. Treatment with α-difluoromethylornithine, a specific inhibitor of ODC activity, normalized the wound response in transgenic mice and decreased wound-induced inflammation if administered from the time of abrasion but not if initiated 4 days following abrasion. These results suggest a role for polyamines in prolonging wound-associated inflammation in addition to stimulating proliferation both of which are sufficient to sustain epidermal hyperplasia and benign tumor growth even in the absence of genetic damage.

Tenascins and the importance of adhesion modulation

Tenascins are a family of extracellular matrix proteins that evolved in early chordates. There are four family members: tenascin-X, tenascin-R, tenascin-W, and tenascin-C. Tenascin-X associates with type I collagen, and its absence can cause Ehlers-Danlos Syndrome. In contrast, tenascin-R is concentrated in perineuronal nets. The expression of tenascin-C and tenascin-W is developmentally regulated, and both are expressed during disease (e.g., both are associated with cancer stroma and tumor blood vessels). In addition, tenascin-C is highly induced by infections and inflammation. Accordingly, the tenascin-C knockout mouse has a reduced inflammatory response. All tenascins have the potential to modify cell adhesion either directly or through interaction with fibronectin, and cell-tenascin interactions typically lead to increased cell motility. In the case of tenascin-C, there is a correlation between elevated expression and increased metastasis in several types of tumors.

Quantitative analysis of three-dimensional human mammary epithelial tissue architecture reveals a role for tenascin-C in regulating c-met function

Remodeling of the stromal extracellular matrix and elevated expression of specific proto-oncogenes within the adjacent epithelium represent cardinal features of breast cancer, yet how these events become integrated is not fully understood. To address this question, we focused on tenascin-C (TN-C), a stromal extracellular matrix glycoprotein whose expression increases with disease severity. Initially, nonmalignant human mammary epithelial cells (MCF-10A) were cultured within a reconstituted basement membrane (BM) where they formed three-dimensional (3-D) polarized, growth-attenuated, multicellular acini, enveloped by a continuous endogenous BM. In the presence of TN-C, however, acini failed to generate a normal BM, and net epithelial cell proliferation increased. To quantify how TN-C alters 3-D tissue architecture and function, we developed a computational image analysis algorithm, which showed that although TN-C disrupted acinar surface structure, it had no effect on their volume. Thus, TN-C promoted epithelial cell proliferation leading to luminal filling, a process that we hypothesized involved c-met, a proto-oncogene amplified in breast tumors that promotes intraluminal filling. Indeed, TN-C increased epithelial c-met expression and promoted luminal filling, whereas blockade of c-met function reversed this phenotype, resulting in normal BM deposition, proper lumen formation, and decreased cell proliferation. Collectively, these studies, combining a novel quantitative image analysis tool with 3-D organotypic cultures, demonstrate that stromal changes associated with breast cancer can control proto-oncogene function.

Tenascin-W is a specific marker of glioma-associated blood vessels and stimulates angiogenesis in vitro

The microenvironment hosting a tumor actively participates in regulating tumor cell proliferation, migration, and invasion. Among the extracellular matrix proteins enriched in the stroma of carcinomas are the tenascin family members tenascin-C and tenascin-W. Whereas tenascin-C overexpression in gliomas is known to correlate with poor prognosis, the status of tenascin-W in brain tumors has not been investigated so far. In the present study, we analyzed protein levels of tenascin-W in 38 human gliomas and found expression of tenascin-W in 80% of the tumor samples, whereas no tenascin-W could be detected in control, nontumoral brain tissues. Double immunohistochemical staining of tenascin-W and von Willebrand factor revealed that tenascin-W is localized around blood vessels, exclusively in tumor samples. In vitro, the presence of tenascin-W increased the proportion of elongated human umbilical vein endothelial cells (HUVECs) and augmented the mean speed of cell migration. Furthermore, tenascin-W triggered sprouting of HUVEC spheroids to a similar extent as the proangiogenic factor tenascin-C. In conclusion, our study identifies tenascin-W as a candidate biomarker for brain tumor angiogenesis that could be used as a molecular target for therapy irrespective of the glioma subtype.—Martina, E., Degen, M., Rüegg, C., Merlo, A., Lino, M. M., Chiquet-Ehrismann, R., Brellier, F. Tenascin-W is a specific marker of glioma-associated blood vessels and stimulates angiogenesis in vitro.

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer.

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer.

Comparative immunohistochemical staining of atherosclerotic plaques using F16, F8 and L19: Three clinical-grade fully human antibodies

OBJECTIVE

F16, F8 and L19 are three fully human monoclonal antibodies, specific to splice isoforms of tenascin-C and fibronectin, which stain sites of active tissue remodeling and which are currently in Phase I and II clinical trials as radio-immunoconjugates and immunocytokines in patients with cancer and arthritis. The characterization of atherosclerosis using these antibodies may open novel pharmacodelivery options for the imaging and treatment of cardiovascular conditions. It may also allow a better assessment of the corresponding immunoconjugates in polymorbid patients with atherosclerotic plaques.

METHODS

We performed a comparative immunohistochemical analysis with the F16, F8 and L19 antibodies in 28 freshly frozen human carotid plaques and in 11 normal arteries. Furthermore, we assessed the localization of the antibodies in relation to the infiltrating macrophages, vasa vasorum and Ki67-positive proliferating cells of the plaque.

RESULTS

The F16 antibody, specific to the extra-domain A1 of tenascin-C, stained plaques with a selective and intense pattern, while F8 and L19, specific to the EDA and EDB domains of fibronectin, respectively, exhibited a less selective and intense staining. In immunofluorescence, F16 was found to bind regions rich in macrophages, vasa vasorum and proliferating cells, while showing no detectable vs. weak staining of normal arteries and of quiescent plaque structures.

CONCLUSION

The human monoclonal antibody F16 stains areas of active tissue remodeling in atherosclerotic plaques and may thus deserve to be investigated as a suitable building block for the development of radiopharmaceuticals for plaque imaging or for the antibody-based targeted delivery of therapeutic agents to atherosclerotic lesions.

Targeting stromal-cancer cell interactions with siRNAs

Tumors are composed of both malignant and normal cells, including fibroblasts, endothelial cells, mesenchymal stem cells, and inflammatory immune cells such as macrophages. These various stromal components interact with cancer cells to promote growth and metastasis. For example, macrophages, attracted by colony-stimulating factor-1 (CSF-1) produced by tumor cells, in turn produce various growth factors such as vascular endothelial growth factor, which supports the growth of tumor cells and their interaction with blood vessels leading to enhanced tumor cell spreading. The activation of autocrine and paracrine oncogenic signaling pathways by stroma-derived growth factors and cytokines has been implicated in promoting tumor cell proliferation and metastasis. Furthermore, matrix metalloproteinases (MMPs) derived from both tumor cells and the stromal compartment are regarded as major players assisting tumor cells during metastasis. Collectively, these recent findings indicate that targeting tumor-stroma interactions is a promising strategy in the search for novel treatment modalities in human cancer. This chapter summarizes our current understanding of the tumor microenvironment and highlights some potential targets for therapeutic intervention with small interfering RNAs.

A novel gene expression profile in lymphatics associated with tumor growth and nodal metastasis

Invasion of lymphatic vessels is a key step in the metastasis of primary tumors to draining lymph nodes. Although the process is enhanced by tumor lymphangiogenesis, it is unclear whether this is a consequence of increased lymphatic vessel number, altered lymphatic vessel properties, or both. Here we have addressed the question by comparing the RNA profiles of primary lymphatic endothelial cells (LEC) isolated from the vasculature of normal tissue and from highly metastatic T-241/vascular endothelial growth factor (VEGF)-C fibrosarcomas implanted in C57BL/6 mice. Our findings reveal significant differences in expression of some 792 genes (i.e., >or=2-fold up- or down-regulated, P <or= 0.05) that code for a variety of proteins including components of endothelial junctions, subendothelial matrix, and vessel growth/patterning. The tumor LEC profile, validated by immunohistochemical staining, is distinct from that of normal, inflammatory cytokine, or mitogen-activated LEC, characterized by elevated expression of such functionally significant molecules as the tight junction regulatory protein endothelial specific adhesion molecule (ESAM), the transforming growth factor-beta coreceptor Endoglin (CD105), the angiogenesis-associated leptin receptor, and the immunoinhibitory receptor CD200, and reduced expression of subendothelial matrix proteins including collagens, fibrillin, and biglycan. Moreover, we show similar induction of ESAM, Endoglin, and leptin receptor within tumor lymphatics in a series of human head and neck and colorectal carcinomas, and uncover a dramatic correlation between ESAM expression and nodal metastasis that identifies this marker as a possible prognostic indicator. These findings reveal a remarkable degree of phenotypic plasticity in cancer lymphatics and provide new insight into the processes of lymphatic invasion and lymph node metastasis.

Expression of tenascin-c and CD44 receptors in cardiac myxomas

BACKGROUND

Myxomas are the most frequent primary cardiac neoplasms. They have an abundant extracellular matrix rich in proteoglycans. Interactions between cells and matrix are very important in the development of tumors, but data about myxomas in this setting are scarce because of the rarity of such neoplasms. The expression of tenascin-c and hyaluran receptors in cardiac myxoma has never been investigated. Moreover, it is now well recognized that cells of cardiac myxoma differentiate along endothelial lines.

METHODS

We have analyzed left atrial myxomas from 13 consecutive patients (six male and seven female, surgically treated), via immunohistochemical methods for the expression of molecules also implicated in angiogenesis in normal and pathological conditions, like tenascin-c and hyaluran receptors CD44s, CD44v5 and CD44v6.

RESULTS

Our data suggest that tenascin-c and CD44s play a synergic and perhaps complementary role in development of cardiac myxomas. In particular, tenascin-c seems to promote aggregation of cells and differentiation in vascular structures, whereas CD44s receptors might be important for cellular motility. Cell proliferation rate in such tumors was very low (MIB-1 labeling index <1%) and uniform in all the areas of the neoplasms regardless of the presence of characteristic structures such as cords and rings of multinucleated cells or the expression of tenascin-c and CD44 receptors.

CONCLUSIONS

This study shows that cardiac myxomas express in the extracellular matrix tenascin-c and on the cellular membranes of neoplastic cells the hyaluran receptor CD44s. Such molecules take part in the mechanism of development of the myxomas and might be in the future the target of nonsurgical treatments.

Tenascin-C expression and its prognostic significance in colorectal cancer

OBJECTIVE

The extracellular matrix glycoprotein tenascin-C has been proposed as a tumor marker with prognostic significance in many cancer forms, but in colorectal cancer, reported results have been controversial. The aim of this study was to evaluate the prognostic value of immunohistochemical tenascin-C expression in a series of 231 patients with colorectal cancer.

METHODS

Paraffin-embedded formalin-fixed specimens were stained with a tenascin-C-specific monoclonal antibody, and the stromal staining intensity and pattern were analyzed.

RESULTS

Tenascin-C immunoreactivity was observed in all 231 specimens, with a pattern of staining that was diffuse and interstitial. The staining was occasional in 39 (17%), moderate in 106 (46%) and strong in 86 specimens (37%). There was no statistically significant association between tenascin-C immunoreactivity and any of the other clinicopathological variables. The cumulative 5-year survival rates of patients with occasional and weak staining were similar (56.8 and 54.9%, respectively), while the patients with strong tenascin-C staining had a lower survival rate (46.1%). This difference in survival was not significant (p = 0.23). The staining pattern and distribution can be viewed from digitized representative microscope slides (virtual slides) at http://www.webmicroscope.net/supplements/tenascin.

CONCLUSIONS

Our results indicate that immunohistochemical expression of tenascin-C is not of prognostic significance in colorectal cancer.

A comprehensive review of the treatment of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an uncommon but malignant cutaneous neuroendocrine carcinoma with a high incidence of local recurrence, regional lymph node metastases, and subsequent distant metastases. The etiology of MCC remains unknown. It usually occurs in sun-exposed areas in elderly people, many of whom have a history of other synchronous or metachronous sun-associated skin lesions. The outcome for most patients with MCC is generally poor. Surgery is the mainstay of treatment. The role of adjuvant therapy has been debated. However, data from recent development support a multimodality approach, including surgical excision of primary tumor with adequate margins and sentinel lymph node dissection followed by postoperative radiotherapy in most cases, as current choice of practice with better locoregional control and disease-free survival. Patients with regional nodal involvement or advanced disease should undergo nodal dissection followed by adjuvant radiotherapy and, perhaps, systemic platinum-based chemotherapy in most cases.

CD34 expression on murine marrow-derived mesenchymal stromal cells: impact on neovascularization

OBJECTIVE

CD34 is a sialomucin often expressed by cells with hemangiopoietic potential and widely serves as a surrogate marker of stem cell potential. Mesenchymal stromal cells (MSCs) also express CD34, although the functional significance of its expression remains undefined. In this study, we determined whether CD34(pos) MSCs are functionally distinct from CD34(null) MSCs.

MATERIALS AND METHODS

MSCs derived from C57Bl/6 mice were transduced to express the green fluorescent protein (GFP) from which pure CD34(pos) MSC and CD34(null) MSC clones were selected. In vitro, clones were examined by microarray analysis, while in vivo subcutaneous implantation of matrix-embedded MSCs was used to assess cell survival, differentiation, and neovascularization.

RESULTS

The flow cytometric phenotype of CD34(pos) and CD34(null) MSCs were similar, as was gene expression of vascular endothelial growth factors (VEGFs) A and B. However, CD34(pos) MSCs upregulated a number of supplementary angiogenesis-associated genes and showed a greater expression of gene associated with vascular differentiation. At 15 days postimplantation, cell survival between CD34(pos) and CD34(null) MSCs was similar, however, CD34(pos) MSCs evoked a significantly greater host-derived response (4.2 +/- 0.7 vs 1.9 +/- 0.5 x 10(6) cells; p < 0.05). GFP-expressing CD34(pos) MSC implants acquired significantly more CD31 expression compared to CD34(null) MSC cells (10.7% +/- 8.4% vs 3.1% +/- 0.6%; p < 0.05), as well as a significantly greater host-derived endothelial cell influx (CD31(+)/CD45(-)).

CONCLUSION

CD34 expression by MSCs correlates with enhanced vasculogenic and angiogenic potential in vivo.

Tenascin-W is a novel marker for activated tumor stroma in low-grade human breast cancer and influences cell behavior

This is the first report about human tenascin-W, the fourth and final member of the extracellular matrix protein family of tenascins. Sixty-three human breast tumor extracts were analyzed by Western blotting for the presence of tenascin-W and compared with tenascin-C, an established marker of tumor stroma. Interestingly, we found tenascin-W expression in the majority of the tumor tissues, but no detectable expression in the normal mammary parenchyma. Eighty-one percent of the breast tumor samples were tenascin-W positive and 86% showed expression of tenascin-C. However, tenascin-W and tenascin-C amounts varied greatly between tumors and some contained either tenascin-W or tenascin-C exclusively, indicating independent mechanisms regulating their expression. Although there was no difference between high- or low-grade tumors with respect to the presence of tenascin-C, tenascin-W was more prominent in low-grade tumors. For 42 of the breast cancer tissues, a frozen tumor microarray was available to confirm the Western blot data by immunohistochemistry. Similar to tenascin-C, tenascin-W was detected in the tumor stroma. Fibroblasts adhered to tenascin-W in a beta(1) integrin-dependent manner and spread with a distinctive morphology under conditions where they remained round on tenascin-C. CHOB2 cells expressing alpha(v)beta(1) or alpha4beta(1) integrins were able to spread on tenascin-W. Furthermore, addition of tenascin-W to the culture medium increased migration of breast cancer cells toward a fibronectin substratum in vitro. These data imply that tenascin-W expression in the activated tumor stroma facilitates tumorigenesis by supporting the migratory behavior of breast cancer cells.