tenascin-C Isoforms Research Articles

RBM10 loss induces aberrant splicing of cytoskeletal and extracellular matrix mRNAs and promotes metastatic fitness.

RBM10 modulates transcriptome-wide cassette exon splicing. Loss-of-function RBM10 mutations are enriched in thyroid cancers with distant metastases. Analysis of transcriptomes and genes mis-spliced by RBM10 loss showed pro-migratory and RHO/RAC signaling signatures. RBM10 loss increases cell velocity. Cytoskeletal and ECM transcripts subject to exon-inclusion events included vinculin (VCL), tenascin C (TNC) and CD44. Knockdown of the VCL exon inclusion transcript in RBM10-null cells reduced cell velocity, whereas knockdown of TNC and CD44 exon-inclusion isoforms reduced invasiveness. RAC1-GTP levels were increased in RBM10-null cells. Mouse Hras G12V /Rbm1O KO thyrocytes develop metastases that are reversed by RBM10 or by combined knockdown of VCL, CD44 and TNC inclusion isoforms. Thus, RBM10 loss generates exon inclusions in transcripts regulating ECM-cytoskeletal interactions, leading to RAC1 activation and metastatic competency. Moreover, a CRISPR-Cas9 screen for synthetic lethality with RBM10 loss identified NFkB effectors as central to viability, providing a therapeutic target for these lethal thyroid cancers.

Extracellular matrix complexity in biomarker studies: a novel assay detecting total serum tenascin-C reveals different distribution to isoform-specific assays.

Serum biomarkers are the gold standard in non-invasive disease diagnosis and have tremendous potential as prognostic and theranostic tools for patient stratification. Circulating levels of extracellular matrix molecules are gaining traction as an easily accessible means to assess tissue pathology. However, matrix molecules are large, multimodular proteins that are subject to a vast array of post-transcriptional and post-translational modifications. These modifications often occur in a tissue- and/or disease-specific manner, generating hundreds of different variants, each with distinct biological roles. Whilst this complexity can offer unique insight into disease processes, it also has the potential to confound biomarker studies. Tenascin-C is a pro-inflammatory matrix protein expressed at low levels in most healthy tissues but elevated in, and associated with the pathogenesis of, a wide range of autoimmune diseases, fibrosis, and cancer. Analysis of circulating tenascin-C has been widely explored as a disease biomarker. Hundreds of different tenascin-C isoforms can be generated by alternative splicing, and this protein is also modified by glycosylation and citrullination. Current enzyme-linked immunosorbent assays (ELISA) are used to measure serum tenascin-C using antibodies, recognising sites within domains that are alternatively spliced. These studies, therefore, report only levels of specific isoforms that contain these domains, and studies on the detection of total tenascin-C are lacking. As such, circulating tenascin-C levels may be underestimated and/or biologically relevant isoforms overlooked. We developed a highly specific and sensitive ELISA measuring total tenascin-C down to 0.78ng/ml, using antibodies that recognise sites in constitutively expressed domains. In cohorts of people with different inflammatory and musculoskeletal diseases, levels of splice-specific tenascin-C variants were lower than and distributed differently from total tenascin-C. Neither total nor splice-specific tenascin-C levels correlated with the presence of autoantibodies to citrullinated tenascin-C in rheumatoid arthritis (RA) patients. Elevated tenascin-C was not restricted to any one disease and levels were heterogeneous amongst patients with the same disease. These data confirm that its upregulation is not disease-specific, instead suggest that different molecular endotypes or disease stages exist in which pathology is associated with, or independent of, tenascin-C. This immunoassay provides a novel tool for the detection of total tenascin-C that is critical for further biomarker studies. Differences between the distribution of tenascin-C variants and total tenascin-C have implications for the interpretation of studies using isoform-targeted assays. These data highlight the importance of assay design for the detection of multimodular matrix molecules and reveal that there is still much to learn about the intriguingly complex biological roles of distinct matrix proteoforms.

Elevated glucose alters global gene expression and tenascin-C alternative splicing in mesangial cells

Mesangial cells are the major extracellular matrix (ECM)-producing cells in the kidney glomerulus and, when exposed to elevated glucose levels, they up-regulate assembly of fibronectin (FN) and other ECM proteins. Increases in glucose concentration are known to alter gene expression; here we investigated the connection between increased ECM production and changes in gene expression in mesangial cells. Comparison of mesangial cells grown in normal or high glucose conditions by RNA-sequencing showed significant expression changes in over 6000 genes and, when grouped by KEGG pathway analysis, identified the ECM-receptor interaction and focal adhesion pathways among the top 5 upregulated pathways. Of note was the significant increase in expression of tenascin-C (TN-C), a known regulator of FN matrix assembly. Mouse TN-C has multiple isoforms due to alternative splicing of 6 FNIII repeat exons. In addition to the transcriptional increase with high glucose, exon inclusion via alternative splicing was also changed resulting in production of higher molecular weight isoforms of TN-C. Mesangial cells grown in normal glucose secreted small isoforms with 1–2 variable repeats included whereas in high glucose large isoforms estimated to include 5 repeats were secreted. Unlike the smaller isoforms, the larger TN-C was not detected in the FN matrix. This change in TN-C isoforms may affect the regulation of FN matrix assembly and in this way may contribute to increased ECM accumulation under high glucose conditions.

Protease-Cleavable Linkers Modulate the Anticancer Activity of Noninternalizing Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) represent an attractive class of biopharmaceutical agents, with the potential to selectively deliver potent cytotoxic agents to tumors. It is generally assumed that ADC products should preferably bind and internalize into cancer cells in order to liberate their toxic payload, but a growing body of evidence indicates that also ADCs based on noninternalizing antibodies may be potently active. In this Communication, we investigated dipeptide-based linkers (frequently used for internalizing ADC products) in the context of the noninternalizing F16 antibody, specific to a splice isoform of tenascin-C. Using monomethyl auristatin E (MMAE) as potent cytotoxic drug, we observed that a single amino acid substitution of the Val-Cit dipeptide linker can substantially modulate the in vivo stability of the corresponding ADC products, as well as the anticancer activity in mice bearing the human epidermoid A431 carcinoma. In these settings, the linker based on the Val-Ala dipeptide exhibited better performances, compared to Val-Cit, Val-Lys, and Val-Arg analogues. Mass spectrometric analysis revealed that the four linkers displayed not only different stability in vivo but also differences in cleavage sites. Moreover, the absence of anticancer activity for a F16-MMAE conjugate featuring a noncleavable linker indicated that drug release modalities, based on proteolytic degradation of the immunoglobulin moiety, cannot be exploited with noninternalizing antibodies. ADC products based on the noninternalizing F16 antibody may be useful for the treatment of several human malignancies, as the cognate antigen is abundantly expressed in the extracellular matrix of several tumors, while being virtually undetectable in most normal adult tissues.

Non-internalizing antibody-drug conjugates display potent anti-cancer activity upon proteolytic release of monomethyl auristatin E in the subendothelial extracellular matrix.

Antibody-drug conjugates (ADCs) represent a promising class of biopharmaceuticals with the potential to localize at the tumor site and improve the therapeutic index of cytotoxic drugs. While it is generally believed that ADCs need to be internalized into tumor cells in order to display optimal therapeutic activity, it has recently been shown that non-internalizing antibodies can efficiently liberate disulfide-linked drugs at the extracellular tumor site, leading to potent anti-cancer activity in preclinical animal models. Here, we show that engineered variants of the F16 antibody, specific to a splice isoform of tenascin-C, selectively localize to the subendothelial tumor extracellular matrix in three mouse models of human cancer (U87, A431, MDA-MB-231). A site-specific coupling of F16 in IgG format with a monomethyl auristatin E (MMAE) derivative, featuring a valine-citrulline dipeptide linker equipped with a self-immolative spacer, yielded an ADC product, which cured tumor-bearing mice at a dose of 7 mg/Kg. The observation of an efficient extracellular proteolytic cleavage of the valine-citrulline linker was surprising, as it has generally been assumed that this peptidic structure would be selectively cleaved by cathepsin B in intracellular compartments. The products described in this article may be useful for the treatment of human malignancies, as their cognate antigen is strongly expressed in the majority of human solid tumors, lymphomas and aggressive leukemias, while being virtually undetectable in most normal adult tissues.

Abstract 2164: Tenascin-C binding peptides for cancer targeting

Abstract Extracellular matrix protein tenascin C (TNC) is strongly overexpressed in the stroma of many solid tumors. TNC expression is upregulated at the invasive front of tumors while being nearly undetectable in normal adult tissues. TNC-targeted humanized antibodies are undergoing clinical development for targeting compounds to solid tumors. Compared to antibodies, homing peptides may have more favorable extravasation and tumor penetration properties. We used in vitro T7 peptide display to identify peptides that bind to the alternatively spliced domain C of the large isoform of Tenascin-C (TNC FnIIIC). The selected phage pool showed 500-fold increase in binding to immobilized TNC FnIIIC. Candidate TNC FnIIIC-binding peptides (designated PL1- 3) were found to bind to TNC FnIII C protein, to the extracellular matrix extracted from PC3 prostate tumors and to cultured tumor cells known to overexpress TNC. To evaluate candidate peptides in vivo, we used mice bearing patient-derived xenografts of P3 glioma (R. Bjerkvig, Bergen, Norway), 4T1 breast tumors, and PC-3prostate carcinoma. A pool of the phages displaying TNC FnIIIC binding peptides, and a panel of phages displaying published tumor homing and control peptides was injected intravenously in tumor-bearing mice, and relative tumor homing and background in control tissues was determined for each phage using high-throughput sequencing (HTS) of phage genomic DNA. These studies demonstrated that among TNC FnIIIC targeting peptides, the PL3 peptide showed the best tumor homing and specificity profile. To evaluate the potential of the synthetic PL3 peptide for tumor targeting of nanoparticles, we coupled PL3 peptide to iron oxide nanoworms (IONW) - paramagnetic nanoparticles that are PEGylated to extend blood half-life, and have because of their elongated shape more effective targeting properties than spherical nanoparticles. 5 hours after intravenous administration of 7.5mg/kg of IONW in mice bearing PC3 prostate cancer xenografts, PL3-IONW but not control IONW showed a robust accumulation in tumor vasculature, and some extravasation into extravascular tumor tissue. Our data suggests that the newly identified TNC FnIIIC targeting peptide, PL3, may be used for payload delivery into tumor stroma. Currently, we are evaluating PL3-targeted IONWs as a MRI contrast agent and as carriers for cytotoxic compounds to TNC expressing tumors. Citation Format: Prakash Lingasamy, Allan Tobi, Hedi Hunt, Pille Säälik, Markko Salumäe, Tambet Teesalu, Tambet Teesalu. Tenascin-C binding peptides for cancer targeting. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2164.

Tenascin-C, a Prognostic Determinant of Esophageal Squamous Cell Carcinoma.

BackgroundTenascin-C, an adhesion modulatory extracellular matrix molecule, is highly expressed in numerous human malignancies; thus, it may contribute to carcinogenesis and tumor progression. We explored the clinicopathological significance of Tenascin-C as a prognostic determinant of esophageal squamous cell carcinoma (ESCC).MethodsIn ESCC patient tissues and cell lines, the presence of isoforms were examined using western blotting. We then investigated Tenascin-C immunohistochemical expression in 136 ESCC tissue samples. The clinical relevance of Tenascin-C expression and the correlation between Tenascin-C expression and expression of other factors related to cancer-associated fibroblasts (CAFs) were also determined.ResultsBoth 250 and 350 kDa sized isoforms of Tenascin-C were expressed only in esophageal cancer tissue not in normal tissue. Furthermore, both isoforms were also identified in all of four CAFs derived from esophageal cancer tissues. Tenascin-C expression was remarkably higher in ESCC than in adjacent non-tumor esophageal epithelium (p < 0.001). Tenascin-C expression in ESCC stromal fibroblasts was associated with patient’s age, tumor (pT) stage, lymph node metastasis, clinical stage, and cancer recurrence. Tenascin-C expression in cancer cells was correlated with an increase in tumor-associated macrophage (TAM) population, cancer recurrence, and hypoxia inducible factor1α (HIF1α) expression. Moreover, Tenascin-C overexpression in cancer cells and stromal fibroblasts was an independent poor prognostic factor for overall survival (OS) and disease-free survival (DFS). In the Cox proportional hazard regression model, Tenascin-C overexpression in cancer cells and stromal fibroblasts was a significant independent hazard factor for OS and DFS in ESCC patients in both univariate and multivariate analyses. Furthermore, Tenascin-C expression in stromal fibroblasts of the ESCC patients was positively correlated with platelet-derived growth factor α (PDGFRα), PDGFRβ, and smooth muscle actin (SMA) expression. The 5-year OS and DFS rates were remarkably lower in patients with positive expressions of both Tenascin-C and PDGFRα (p < 0.001), Tenascin-C and PDGFRβ (p < 0.001), Tenascin-C and SMA (p < 0.001), Tenascin-C and fibroblast activation protein (FAP) (p < 0.001), and Tenascin-C and fibroblast-stimulating protein-1 (FSP1) (p < 0.001) in ESCC stromal fibroblasts than in patients with negative expressions of both Tenascin-C and one of the abovementioned CAF markers.ConclusionOur results show that Tenascin-C is a reliable and significant prognostic factor in ESCC. Tenascin-C may thus be a potent ESCC therapeutic target.

Abstract SY35-04: Arming tumor-targeting antibodies with cytokine payloads: Emerging clinical results

Abstract Antibodies can be used to deliver bioactive molecules (drugs, cytokines, photosensitizers, radionuclides, etc.) to the tumor environment, thus sparing normal tissues. Pharmacodelivery strategies targeting certain modified extracellular matrix components, associated with the tumor neo-vasculature, is particularly attractive, because of: (i) the abundance and stability of these antigens (e.g., splice isoforms of fibronectin and tenascin-C); (ii) the dependence of cancer on new blood vessels; (iii) the accessibility of neo-vascular structures for therapeutic agents coming from the blood-stream; (iv) the fact that some extracellular matrix components are very abundant in many different cancer types, while being virtually undetectable in most normal adult tissues [Refs. 1-8]. In this lecture, I will present our experience (at a preclinical and clinical level) in the development and clinical applications of antibody-cytokine fusion proteins (“immunocytokines”) for cancer therapy applications. In particular, I will focus on pro-inflammatory immunocytokines specific to the alternatively-spliced EDA and EDB domains of fibronectin, or A1 domain of tenascin-C, used either as single agents or in combination. Immunocytokines based on IL2 or TNF as payloads are able to dramatically increase the density of certain leukocytes (e.g., T cells and NK cells) at the neoplastic site in various types of malignancies.

Tenascin-C (TNC) Promotes Breast Cancer Cell Invasion and Proliferation: Functional Effects of TNC Knockdown in Highly Invasive Breast Cancer Cell Lines

The tumour microenvironment plays a crucial role in the development of breast cancer. Tenascin-C (TNC), a matricellular protein and its high molecular weight (MW) isoforms have been shown to be over-expressed in the stroma of breast cancers and are associated with poor prognosis. The aim of this study was to investigate the effects of TNC knockdown in TNC expressing invasive breast cancer cell lines on cancer cell behaviour. Small interfering RNA (siRNA) targeting different exons in TNC (24, 14 and 14-AD1) were designed, synthesised and transfected into the highly invasive MDA-MB-231 breast cancer cell line. The phenotypic alterations caused by TNC knockdown were analysed by Two Dimension (2D) invasion assays and proliferation assays using the mitotic marker Phispho-Histone H3 (pHH3). The siRNA targeted cells showed significant down-regulation of both total TNC (p <0.001) and high MW isoforms (p <0.001) in MDA-MB-231 cells. Moreover, knockdown of total TNC and high MW TNC isoforms significantly decreased both cell invasion (total TNC p<0.001 and TNC-14 p <0.001) and proliferation (total TNC p <0.001 and TNC-AD1 p <0.05). In conclusion, TNC knockdown significantly decreases proliferation and invasion in breast cancer cell lines, confirming its importance in breast cancer progression.

Targeting Interleukin-2 to the Bone Marrow Stroma for Therapy of Acute Myeloid Leukemia Relapsing after Allogeneic Hematopoietic Stem Cell Transplantation

The tumor-directed delivery of therapeutics using monoclonal antibodies specific to a tumor-associated antigen promises to accumulate large doses of the delivered payload at the tumor site while sparing healthy organs. The antibody-based delivery of interleukin-2 (IL-2) to extracellular targets expressed in the easily accessible tumor vasculature has shown promising results in animal models of solid tumors and hematological malignancies. In xenograft and immunocompetent murine models of acute myeloid leukemia (AML), IL-2-based vascular targeting antibody fusions have recently demonstrated potent anti-leukemic activity, especially when used in combination with cytarabine. Here, we report our experiences in four patients with relapsed AML after allogeneic hematopoietic stem cell transplantation (allo-HSCT), who were treated with the immunocytokine F16-IL2, consisting of a human monoclonal antibody specific to spliced large isoforms of tenascin-C fused to human IL-2, in combination with very low dose cytarabine (5 mg subcutaneously twice daily for 10 days). Clinical evidence of anti-leukemia efficacy was shown in all patients. One patient with rapidly progressing disseminated extramedullary AML lesions achieved a complete metabolic response in PET/CT, which lasted three months. Two out of three patients with bone marrow relapse achieved a blast reduction with transient molecular negativity (NPM1). One of the two enjoyed a short complete remission before AML relapse occurred two months after the first infusion of F16-IL2. The other patient did not regenerate neutrophil and thrombocyte counts and showed progressive disease after completion of the first cycle. In line with a site-directed delivery of the cytokine, F16-IL2 led to an extensive infiltration of immune effector cells (natural killer cells, CD8+ T cells, γδ T cells) in the bone marrow. Grade 2 fevers were the only non-hematological side effects in two patients. Grade 3 cytokine-release syndrome developed in the other two patients, required hospitalization, but was manageable in both cases with systemic glucocorticoids. No non-hematological grade 4 toxicities were observed. The concept of specifically targeting IL-2 to the leukemia-associated stroma using armed antibodies deserves further evaluation in clinical trials, especially in patients who relapse after allo-HSCT. DisclosuresOff Label Use: In this report, the antibody-cytokine fusion protein F16-IL2 has been used in a compassionate use setting in individual patients presenting with AML relapse after allogeneic stem cell transplantation. F16-IL2 is currently being evaluated in phase I/II studies in patients with solid cancer.. Neri:Philogen SpA: Employment, Equity Ownership.

Splicing factor SRSF6 promotes hyperplasia of sensitized skin

SummaryMany biological processes involve gene-expression regulation by alternative splicing. Here, we identify the splicing factor SRSF6 as a regulator of wound healing and tissue homeostasis in skin. We show that SRSF6 is a proto-oncogene that is frequently overexpressed in human skin cancer. Overexpressing it in transgenic mice induces hyperplasia of sensitized skin and promotes aberrant alternative splicing. We identify 139 target genes of SRSF6 in skin, and show that this SR protein binds to alternative exons of the extracellular-matrix protein tenascin C pre-mRNA, promoting the expression of isoforms characteristic of invasive and metastatic cancer in a cell-type-independent manner. SRSF6 overexpression additionally results in depletion of Lgr6+ stem cells, and excessive keratinocyte proliferation and response to injury. Furthermore, the effects of SRSF6 in wound healing assayed in vitro depend on the TNC isoforms. Thus, abnormal SR-protein expression can perturb tissue homeostasis.

Abstract SY28-04: Targeting the tumor extracellular matrix with armed antibodies

Abstract Antibodies can be used to deliver bioactive molecules (drugs, cytokines, photosensitizers, radionuclides, etc.) to the tumor environment, thus sparing normal tissues. The targeting of modified sub-endothelial extracellular matrix components using armed antibodies is particularly attractive, because of: (i) the abundance and stability of some of these antigens (e.g., splice isoforms of fibronectin and tenascin-C); (ii) the dependence of cancer on new blood vessels (iii) accessibility of these structures from the blood-stream (iv) the fact that some of these antigens are very aboundant in many different cancer types, while being virtually undetectable in most normal adult tissues. Advanced preclinical and clinical data on armed antibodies will be presented in this lecture.

Platelet-Derived Growth Factor-BB Mediates Cell Migration through Induction of Activating Transcription Factor 4 and Tenascin-C

The acute response to vascular cell injury, which underpins vasculo-occlusive pathologies such as atherogenesis and restenosis after percutaneous coronary intervention, involves a complex series of molecular events that alter patterns of gene expression and favor a synthetic phenotype. One transcription factor that has been implicated in this process is the evolutionarily conserved mammalian stress response pathway regulator activating transcription factor 4 (ATF-4). Here, we show for the first time that both mRNA and protein levels of ATF-4 are induced in smooth muscle cells (SMCs) by the potent migratory factor PDGF-BB through PDGFR-β. PDGF-BB also stimulates the expression of tenascin-C (TN-C), an extracellular matrix glycoprotein that regulates the activity of focal adhesion complexes, facilitating the SMC migration that underlies negative vascular remodeling in response to injury. Overexpression of ATF-4 increased transcript levels of the four TN-C isoforms in rat vascular SMCs, and ATF-4 knockdown inhibited PDGF-BB-inducible TN-C expression in vitro and injury-inducible TN-C protein expression in the balloon-injured rat artery wall. Furthermore, we show that ATF-4 is required for PDGF-BB-inducible SMC migration in response to injury. PDGF-BB-induced migration was also compromised in ATF-4 null mEFs, and this effect was rescued by the addition of TN-C. Our findings thus demonstrate the role of ATF-4 in both injury- and PDGF-BB-inducible TN-C expression and cell migration.

Differential vascular expression and regulation of oncofetal tenascin-C and fibronectin variants in renal cell carcinoma (RCC): implications for an individualized angiogenesis-related targeted drug delivery

The study was aimed at determining the vascular expression of oncofetal fibronectin (oncfFn) and tenascin-C (oncfTn-C) isoforms in renal cell carcinoma (RCC) and its metastases which are well-known targets for antibody-based pharmacodelivery. Furthermore, the influence of tumour cells on endothelial mRNA expression of these molecules was investigated. Evaluation of vascular ED-A(+) and ED-B(+) Fn as well as A1(+) and C(+) Tn-C was performed after immunofluorescence double and triple staining using human recombinant antibodies on clear cell, papillary and chromophobe primary RCC and metastases. The influence of hypoxic RCC-conditioned medium on oncfFn and oncfTn-C mRNA expression was examined in human umbilical vein endothelial cells (HUVEC) by real time RT-PCR. There are RCC subtype specific expression profiles of vascular oncfFn and oncfTn-C and corresponding patterns when comparing primary tumours and metastases. Within one tumour, there are different vessel populations with regard to the incorporation of oncfTn-C and oncfFn into the vessel wall. In vitro tumour-derived soluble mediators induce an up regulation of oncfTn-C and oncfFn mRNA in HUVEC which can be blocked by Avastin(®). Vascular expression of oncFn and oncTn-C variants depends on RCC subtype and may reflect an individual tumour stroma interaction or different stages of vessel development. Therefore, oncFn or oncTn-C variants can be suggested as molecular targets for individualized antibody based therapy strategies in RCC. Tumour-derived VEGF could be shown to regulate target expression.

Existence of tenascin-C isoforms in rat that contain the alternatively spliced AD1 domain are developmentally regulated during hippocampal development.

Tenascin-C (TN-C) is a multimodular glycoprotein of the extracellular matrix which is important for the development of the nervous system and has a range of different functions which are mediated by the different protein domains present. TN-C contains eight constitutive fibronectin type III (FNIII) domains and a region of alternatively spliced FNIII domains. In the mouse and chick, six of these domains have been described and characterized, whereas in human there are nine of them. In this report, we show that seven alternatively spliced FNIII domains exist in rat and describe the differential expression pattern of the additional domain AD1 during embryonic and postnatal rat brain development. The AD1 domain of rat is homologous to the ones described in human and chick proteins but does not exist in mouse. Its expression can be located to the developing rat hippocampus and the lining of the lateral ventricle, regions where the TN-C protein may affect the behavior of stem and progenitor cells. During hippocampal development AD1 and the other alternatively spliced domains are differentially expressed as shown by RT-PCRs, immunocytochemistry and in situ hybridizations.

A comparative immunofluorescence analysis of three clinical-stage antibodies in head and neck cancer

BackgroundThe antibody-based targeted delivery of bioactive molecules to tumour vasculature is an attractive avenue to concentrate therapeutic agents at cancer sites, while sparing normal organs. L19, F8 and F16 are three fully human monoclonal antibodies, specific to splice isoforms of fibronectin and tenascin-C, which bind to 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.In this article, we report the first comparative analysis of expression patterns for the extra domains EDB and EDA of fibronectin and A1 of tenascin-C in both primary and metastatic head and neck cancer lesions.MethodsWe performed a comparative immunofluorescence analysis with the L19, F8 and F16 antibodies in 40 freshly frozen human head and neck cancer specimens.ResultsOn average, F8 and F16 exhibited similar staining intensities, which were typically stronger than L19. Interestingly, some specimens exhibited striking differences in staining by the three antibodies.ConclusionsThese results suggests that an individualized treatment procedure (e.g., choice of L19, F8 or F16 based on immuno-PET or immunofluorescence procedure) may represent the most logical avenue for offering the best possible antibody to any given patient.

Chaotic neovascularization induced by aggressive fibrosarcoma cells overexpressing S-adenosylmethionine decarboxylase

S-adenosylmethionine decarboxylase is a key enzyme in the biosynthesis of polyamines essential for cell proliferation. Overexpression of S-adenosylmethionine decarboxylase in rodent fibroblasts led to aggressive transformants (Amdc-s cells) that had unforeseen high invasive capacity in nude mice, invading rapidly from the subcutaneous injection site into the peritoneal cavity and its organs. In vitro, these cells were much more invasive than Ras-oncogene-transformed fibroblasts, or human HT-1080 fibrosarcoma and MDA-MB-231 breast cancer cells. In immunohistological characterization, Amdc-s-induced tumors showed chaotic neovascularization, with abundant pleomorphic vessel-like structures that had noncontiguous or totally missing laminin (basement membrane) and CD31 (endothelial cell) immunoreactivity. Gene expression and protein analyses of Amdc-s cells showed them to overexpress several pro-angiogenic molecules, including vascular endothelial growth factor (VEGF-A), and to exhibit profound down-regulation of the anti-angiogenic thrombospondin-1 (TSP-1). By reintroduction of TSP-1 into Amdc-s cells, the high invasiveness was efficiently inhibited in vitro. Interestingly, Amdc-s cells showed up-regulation of hepatocyte growth factor (HGF) and also expressed the MET receptor, creating thus an autocrine loop able to regulate VEGF-A and TSP-1 levels. Further, we found Amdc-s cells to express increased amounts of matrix metalloproteinase-2 (MMP-2) and the large isoform of tenascin-C (TN-C), which may also contribute to the angiogenic switch and invasiveness. Consequently, Amdc-s cells offer an excellent model to sort out the key molecules of aggressive tumor growth, and thereby help in designing rational, novel anti-vascular and other cancer therapies.

EMT in NSCLC and malignant pleural mesothelioma

Both NSCLC and MPM are composed of different histotypes. These histotypes are clinically relevant, since both mutational profiles and response to chemotherapeutic drugs are different. Next to histotype markers, predictors such as EGFR are increasingly required in clinical pathology, also on cell blocks from pleural effusions. Such effusions can arise from both lung adenocarcinoma and MPM, thus are a valid resource for new biomarkers. We identified the epithelial-mesenchymal transition N-glycoprotein periostin in effusions from lung AC by shotgun mass spectrometry. EMT is an important transdifferentiation concept, whereby polarized epithelial cells detach from their solid lattice and become migratory and invasive via acquisition of a fibroblastoid phenotype. The EMT programme is regulated by a complex signalling network, leading to an upregulation of mesenchymal proteins like vimentin, associated with loss of E-cadherin. The EMT protein periostin was correlated with clinico-pathological parameters of tumour progression, the squamous cell histotype of NSCLC and the sarcomatoid of MPM, respectively. Importantly, EMT is related to the cancer stem cell phenotype, conferring increased drug resistance. Both NSCLC and MPM tumour cells are embedded in a prominent desmoplastic stroma. A microenvironment therapy could comprise a combination of inhibitors directed against tumour cell surface receptors, neo-vessels, extracellular matrix fibres and immune cells. Derivatives of the human monoclonal scFv antibodies L19 and F16, specific to the splice isoforms of fibronectin (with extracellular domain B) and tenascin-C (Al domain) are clinically effective, thus intracavitary chemotherapy with pleural infusion is a phase 1/2 study rationale for advanced lung AC or MPM.

Jekyll and Hyde: the role of the microenvironment on the progression of cancer

It is now recognized that the host microenvironment undergoes extensive change during the evolution and progression of cancer. This involves the generation of cancer-associated fibroblasts (CAFs), which, through release of growth factors and cytokines, lead to enhanced angiogenesis, increased tumour growth and invasion. It has also been demonstrated that CAFs may modulate the cancer stem cell (CSC) phenotype, which has therapeutic implications. The altered fibroblast phenotype also contributes to the development of an altered extracellular matrix (ECM), with synthesis of ECM isoforms rarely found in normal tissues, including tenascin-C isoforms and the fibronectin EDA isoform. There is also emerging evidence of how the tensile strength of the tumour-associated ECM may be modified and lead to altered signalling in tumour cells. The hypoxic environment of the tumour stimulates angiogenesis and also impacts on other aspects of cell signalling, including the c-met pathway and lysyl oxidase-mediated signalling, which can directly promote tumour cell invasion. The inflammatory infiltrate associated with many solid tumours also modulates tumour function, having both anti- and pro-tumour effects. All of these components of the microenvironment provide potential targets for therapeutic attack, with a number of molecules already in clinical trials. It is also becoming evident that characterizing the tumour microenvironment can provide important prognostic and predictive information about tumours, independent of the tumour cell phenotype.

Expression of tenascin-C and its isoforms in the breast

Tenascin-C (TNC) is an extracellular matrix glycoprotein which is frequently up-regulated in a variety of pathological conditions including chronic inflammation and cancer. TNC has been implicated in the modulation of cell migration, proliferation, invasion and angiogenesis. Multiple isoforms of TNC can be generated through the alternative splicing of nine exons located in the fibronectin type III region of the molecule. The profile of isoforms expressed differs between cancers and normal breast, with the fully truncated TNC isoform being predominant in normal and benign tissues and higher molecular weight isoforms induced predominantly in cancer. The addition of extra domains within the fibronectin type III repeat domain greatly affects TNC function with multiple exon combinations available for splicing. Exons 14 and 16 are considered to be tumour-associated and have been shown to affect breast cell line invasion and growth in vitro to a greater extent than the full-length TNC isoform. This mini review will provide a summary of the literature to date regarding the expression of TNC isoforms in the breast and also discuss more recent developments in the field regarding exon AD1.