VE-cadherin junction dynamics in initial lymphatic vessels promotes lymph node metastasis

The endothelial junction component vascular endothelial (VE)-cadherin governs junctional dynamics in the blood and lymphatic vasculature. Here, we explored how lymphatic junction stability is modulated by elevated VEGFA signaling to facilitate metastasis to sentinel lymph nodes. Zippering of VE-cadherin junctions was established in dermal initial lymphatic vessels after VEGFA injection and in tumor-proximal lymphatics in mice. Shape analysis of pan-cellular VE-cadherin fragments revealed that junctional zippering was accompanied by accumulation of small round-shaped VE-cadherin fragments in the lymphatic endothelium. In mice expressing a mutant VEGFR2 lacking the Y949 phosphosite (Vegfr2 Y949F/Y949F ) required for activation of Src family kinases, zippering of lymphatic junctions persisted, whereas accumulation of small VE-cadherin fragments was suppressed. Moreover, tumor cell entry into initial lymphatic vessels and subsequent metastatic spread to lymph nodes was reduced in mutant mice compared with WT, after challenge with B16F10 melanoma or EO771 breast cancer. We conclude that VEGFA mediates zippering of VE-cadherin junctions in initial lymphatics. Zippering is accompanied by increased VE-cadherin fragmentation through VEGFA-induced Src kinase activation, correlating with tumor dissemination to sentinel lymph nodes.

Phenotypic changes in low-density lipoprotein particles as markers of adverse clinical outcomes in COVID-19

BACKGROUND AND AIMS

Low-density lipoprotein (LDL) plasma concentration decline is a biomarker for acute inflammatory diseases, including coronavirus disease-2019 (COVID-19). Phenotypic changes in LDL during COVID-19 may be equally related to adverse clinical outcomes.

METHODS

Individuals hospitalized due to COVID-19 (n = 40) were enrolled. Blood samples were collected on days 0, 2, 4, 6, and 30 (D0, D2, D4, D6, and D30). Oxidized LDL (ox-LDL), and lipoprotein-associated phospholipase A2 (Lp-PLA2) activity were measured. In a consecutive series of cases (n = 13), LDL was isolated by gradient ultracentrifugation from D0 and D6 and was quantified by lipidomic analysis. Association between clinical outcomes and LDL phenotypic changes was investigated.

RESULTS

In the first 30 days, 42.5% of participants died due to Covid-19. The serum ox-LDL increased from D0 to D6 (p < 0.005) and decreased at D30. Moreover, individuals who had an ox-LDL increase from D0 to D6 to over the 90th percentile died. The plasma Lp-PLA2 activity also increased progressively from D0 to D30 (p < 0.005), and the change from D0 to D6 in Lp-PLA2 and ox-LDL were positively correlated (r = 0.65, p < 0.0001). An exploratory untargeted lipidomic analysis uncovered 308 individual lipids in isolated LDL particles. Paired-test analysis from D0 and D6 revealed higher concentrations of 32 lipid species during disease progression, mainly represented by lysophosphatidyl choline and phosphatidylinositol. In addition, 69 lipid species were exclusively modulated in the LDL particles from non-survivors as compared to survivors.

CONCLUSIONS

Phenotypic changes in LDL particles are associated with disease progression and adverse clinical outcomes in COVID-19 patients and could serve as a potential prognostic biomarker.

Tyrosine-protein kinase Yes controls endothelial junctional plasticity and barrier integrity by regulating VE-cadherin phosphorylation and endocytosis

Vascular endothelial (VE)-cadherin in endothelial adherens junctions is an essential component of the vascular barrier, critical for tissue homeostasis and implicated in diseases such as cancer and retinopathies. Inhibitors of Src cytoplasmic tyrosine kinase have been applied to suppress VE-cadherin tyrosine phosphorylation and prevent excessive leakage, edema and high interstitial pressure. Here we show that the Src-related Yes tyrosine kinase, rather than Src, is localized at endothelial cell (EC) junctions where it becomes activated in a flow-dependent manner. EC-specific Yes1 deletion suppresses VE-cadherin phosphorylation and arrests VE-cadherin at EC junctions. This is accompanied by loss of EC collective migration and exaggerated agonist-induced macromolecular leakage. Overexpression of Yes1 causes ectopic VE-cadherin phosphorylation, while vascular leakage is unaffected. In contrast, in EC-specific Src-deficiency, VE-cadherin internalization is maintained, and leakage is suppressed. In conclusion, Yes-mediated phosphorylation regulates constitutive VE-cadherin turnover, thereby maintaining endothelial junction plasticity and vascular integrity.

Palmdelphin Regulates Nuclear Resilience to Mechanical Stress in the Endothelium

Supplemental Digital Content is available in the text.

PALMD (palmdelphin) belongs to the family of paralemmin proteins implicated in cytoskeletal regulation. Single nucleotide polymorphisms in the PALMD locus that result in reduced expression are strong risk factors for development of calcific aortic valve stenosis and predict severity of the disease.

Suppressed Vascular Leakage and Myocardial Edema Improve Outcome From Myocardial Infarction

Aim

The acute phase of myocardial infarction (MI) is accompanied by edema contributing to tissue damage and disease outcome. Here, we aimed to identify the mechanism whereby vascular endothelial growth factor (VEGF)-A induces myocardial edema in the acute phase of MI to eventually promote development of therapeutics to specifically suppress VEGFA-regulated vascular permeability while preserving collateral vessel formation.

Methods and Results

VEGFA regulates vascular permeability and edema by activation of VEGF receptor-2 (VEGFR2), leading to induction of several signaling pathways including the cytoplasmic tyrosine kinase c-Src. The activated c-Src in turn phosphorylates vascular endothelial (VE)-cadherin, leading to dissociation of endothelial adherens junctions. A particular tyrosine at position 949 in mouse VEGFR2 has been shown to be required for activation of c-Src. Wild-type mice and mice with phenylalanine replacing tyrosine (Y) 949 in VEGFR2 (Vegfr2 ^Y949F/Y949F ) were challenged with MI through permanent ligation of the left anterior descending coronary artery. The infarct size was similar in wild-type and mutant mice, but left ventricular wall edema and fibrinogen deposition, indicative of vascular leakage, were reduced in the Vegfr2 ^Y949F/Y949F strain. When challenged with large infarcts, the Vegfr2 ^Y949F/Y949F mice survived significantly better than the wild-type strain. Moreover, neutrophil infiltration and levels of myeloperoxidase were low in the infarcted Vegfr2 ^Y949F/Y949F hearts, correlating with improved survival. In vivo tyrosine phosphorylation of VE-cadherin at Y685, implicated in regulation of vascular permeability, was induced by circulating VEGFA in the wild-type but remained at baseline levels in the Vegfr2 ^Y949F/Y949F hearts.

Conclusion

Suppression of VEGFA/VEGFR2-regulated vascular permeability leads to diminished edema without affecting vascular density correlating with improved myocardial parameters and survival after MI.

Myc-dependent endothelial proliferation is controlled by phosphotyrosine 1212 in VEGF receptor-2

Exaggerated signaling by vascular endothelial growth factor (VEGF)‐A and its receptor, VEGFR2, in pathologies results in poor vessel function. Still, pharmacological suppression of VEGFA/VEGFR2 may aggravate disease. Delineating VEGFR2 signaling in vivo provides strategies for suppression of specific VEGFR2‐induced pathways. Three VEGFR2 tyrosine residues (Y949, Y1212, and Y1173) induce downstream signaling. Here, we show that knock‐in of phenylalanine to create VEGFR2 Y1212F in C57Bl/6 and FVB mouse strains leads to loss of growth factor receptor‐bound protein 2‐ and phosphoinositide 3′‐kinase (PI3K)p85 signaling. C57Bl/6 Vegfr2^{Y1212F/Y1212F} show reduced embryonic endothelial cell (EC) proliferation and partial lethality. FVB Vegfr2^{Y1212F/Y1212F} show reduced postnatal EC proliferation. Reduced EC proliferation in Vegfr2^{Y1212F/Y1212F} explants is rescued by c‐Myc overexpression. We conclude that VEGFR2 Y1212 signaling induces activation of extracellular‐signal‐regulated kinase (ERK)1/2 and Akt pathways required for c‐Myc‐dependent gene regulation, endothelial proliferation, and vessel stability.

Correction to: DNA methylation-based reclassification of olfactory neuroblastoma

In the original publication, the second name of the twentieth author was incorrect. It should read as 'Miguel Sáinz-Jaspeado'. The original publication of the article has been updated to reflect the change. This correction was authored by Ulrich Schüller on behalf of all authors of the original publication.

Intravital imaging-based analysis tools for vessel identification and assessment of concurrent dynamic vascular events

The vasculature undergoes changes in diameter, permeability and blood flow in response to specific stimuli. The dynamics and interdependence of these responses in different vessels are largely unknown. Here we report a non-invasive technique to study dynamic events in different vessel categories by multi-photon microscopy and an image analysis tool, RVDM (relative velocity, direction, and morphology) allowing the identification of vessel categories by their red blood cell (RBC) parameters. Moreover, Claudin5 promoter-driven green fluorescent protein (GFP) expression is used to distinguish capillary subtypes. Intradermal injection of vascular endothelial growth factor A (VEGFA) is shown to induce leakage of circulating dextran, with vessel-type-dependent kinetics, from capillaries and venules devoid of GFP expression. VEGFA-induced leakage in capillaries coincides with vessel dilation and reduced flow velocity. Thus, intravital imaging of non-invasive stimulation combined with RVDM analysis allows for recording and quantification of very rapid events in the vasculature.

Different stimuli can induce dynamic changes in blood flow velocity, vessel diameter and permeability. Here the authors develop a multi-photon microscopy-based image analysis tool allowing the identification of vessels and the assessment of rapid changes in large vascular networks.

Cytokines regulating lymphangiogenesis

Lymphatic vessels are established by differentiation of lymphendothelial progenitors during embryogenesis. Lymphangiogenesis, the formation of new lymphatic vessels from pre-existing ones is rare in the healthy adult but takes place during pathological conditions such as inflammation, tissue repair and tumor growth. Conditions of dysfunctional lymphatics exist after surgical interventions or in certain genetic diseases. A key lymphangiogenic stimulator is vascular endothelial growth factor-C (VEGFC) acting on VEGF receptor-3 (VEGFR3) expressed on lymphendothelial cells. Other cytokines may act directly to regulate lymphangiogenesis positively or negatively, or indirectly by inducing expression of VEGFC. This review describes different known lymphangiogenic cytokines, their mechanism of action and role in lymphangiogenesis in health and disease.

Caveolin-1 promotes Ewing sarcoma metastasis regulating MMP-9 expression through MAPK/ERK pathway

Ewing sarcoma (ES) is a bone and soft tissue sarcoma affecting mostly children and young adults. Caveolin-1 (CAV1) is a well-known target of EWS/FLI1, the main driver of ES, with an oncogenic role in ES. We have previously described how CAV1 is able to induce metastasis in ES via matrix metalloproteinase-9 (MMP-9). In the present study we showed how CAV1 silencing in ES reduced MEK1/2 and ERK1/2 phosphorylation. Accordingly, chemical inhibition of MEK1/2 resulted in reduction in MMP-9 expression and activity that correlated with reduced migration and invasion. IQ Motif Containing GTPase Activating Protein 1 (IQGAP1) silencing reduced MEK1/2 and ERK1/2 phosphorylation and MMP-9 expression. Furthermore, IQGAP1 silenced cells showed a marked decrease in their migratory and invasive capacity. We demonstrated that CAV1 and IQGAP1 localize in close proximity at the cellular edge, thus IQGAP1 could be the connecting node between CAV1 and MEK/ERK in ES metastatic phenotype. Analysis of the phosphorylation profile of CAV1-silenced cells showed a decrease of p-ribosomal protein S6 (RPS6). RPS6 can be phosphorylated by p90 ribosomal S6 kinases (RSK) proteins. CAV1-silenced cells showed reduced levels of p-RSK1 and treatment with U0126 provoked the same effect. Despite not affecting ERK1/2 and RPS6 phosphorylation status neither MMP-9 expression nor activity, RSK1 silencing resulted in a reduced migratory and invasive capacity in vitro and reduced incidence of metastases in vivo in a novel orthotopic model. The present work provides new insights into CAV1-driven metastatic process in ES unveiling novel key nodes.

VEGFR2 pY949 signalling regulates adherens junction integrity and metastatic spread

The specific role of VEGFA-induced permeability and vascular leakage in physiology and pathology has remained unclear. Here we show that VEGFA-induced vascular leakage depends on signalling initiated via the VEGFR2 phosphosite Y949, regulating dynamic c-Src and VE-cadherin phosphorylation. Abolished Y949 signalling in the mouse mutant Vegfr2^Y949F/Y949F leads to VEGFA-resistant endothelial adherens junctions and a block in molecular extravasation. Vessels in Vegfr2^Y949F/Y949F mice remain sensitive to inflammatory cytokines, and vascular morphology, blood pressure and flow parameters are normal. Tumour-bearing Vegfr2^Y949F/Y949F mice display reduced vascular leakage and oedema, improved response to chemotherapy and, importantly, reduced metastatic spread. The inflammatory infiltration in the tumour micro-environment is unaffected. Blocking VEGFA-induced disassembly of endothelial junctions, thereby suppressing tumour oedema and metastatic spread, may be preferable to full vascular suppression in the treatment of certain cancer forms.

Signals through VEGF receptor 2 (VEGFR2) increase vascular permeability, promoting cancer progression. Here the authors show that a point mutation in VEGFR2 preventing its auto-phosphorylation leads to reduced metastatic spread and improved response to chemotherapy in tumor-bearing mice, without affecting tumor inflammation.

Abstract A18: Epigenetic profiling uncovers the suppressive role of caveolae in Ewing sarcoma

Ewing sarcoma (ES) is the second most common bone tumor in childhood. ES harbors a characteristic gene translocation that gives rise to a fusion protein, most commonly EWS/FLI1 (EF). Caveolin-1 (CAV1) is a direct target of EF, it is overexpressed in ES and has an oncogenic role. CAV1 and the Polymerase I and transcript release factor (PTRF) interact at the plasma membrane and are essential for caveolae formation. The methylome analysis of ES samples and cell lines revealed a hypermethylation in the N-shore islands of the PTRF promoter compared to normal cells. We hypothesize that, as ES cells have very few caveolae and do not express PTRF, the oncogenic role of CAV1 in ES would be driven by the impossibility of being recruited at caveolae.

Epigenetic silencing of PTRF was confirmed by bisulfite genomic sequencing on ES cells and human samples. We verified that ES cells do not express PTRF by western blot. Demethylating agent 5-aza (decitabine) treatment of A673 cells resulted in re-expression of PTRF and enhancement of caveolae formation as shown by electron microscopy. Immunofluorescent imaging in TC252 cells stably transfected with PTRF showed co-localization with CAV1 at the plasma membrane. Immunoprecipitation assays also confirmed their interaction. PTRF transfection in TC252 cells promoted an increase in cell death up to 50% in a caspase-3 dependent way. Furthermore, PTRF-expressing xenografts had a lower capacity to form tumors compared to controls. CAV1-PTRF pro-apoptotic interaction was verified also in EW7 cells.

These results pointed that CAV1-PTRF interaction and caveolae formation promote cell death in ES cells. The presence of caveolae has been related with stress and p53 activation, due to the MDM2 binding to CAV1, that causes the release and activation of p53. To elucidate the role of p53 in the PTRF-mediated cell death, PTRF-transfected TC252 cells were treated with a p53 siRNA and cell death was significantly reduced. Our results suggest that PTRF acts as a tumor suppressor in ES. PTRF re-expression enhances caveolae formation in ES cells, thus modulating CAV1 localization that results in p53-mediated cell death.

Citation Format: Juan Huertas-Martínez, Frank Court, Santiago Rello-Varona, David Herrero Martin, Olga Almacellas, Miguel Sáinz-Jaspeado, Silvia Garcia-Monclús, Laura Lagares-Tena, Raqeul Buj, Lourdes Hontecillas-Prieto, Silvia Mateo-Lozano, Ana Sastre, Daniel Azorín, Jaune Mora, Josep Roma, Sebastian Moran, Soledad Gallego, Miguel Angel Peinado, Xavier Garcia del Muro, Javier Alonso, Enrique de Alava, Dave Monk, Manel Esterller, Oscar M Tirado. Epigenetic profiling uncovers the suppressive role of caveolae in Ewing sarcoma. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr A18.

Phase I study and preclinical efficacy evaluation of the mTOR inhibitor sirolimus plus gemcitabine in patients with advanced solid tumours

Background:

We conducted a phase I study in patients with advanced solid tumours to identify the recommended dose, assess pharmacokinetics (PK), pharmacodynamic activity and preclinical antitumour efficacy of the combination of sirolimus and gemcitabine.

Methods:

Nineteen patients were treated with sirolimus 2 or 5 mg daily and gemcitabine 800 or 1000 mg m⁻² on days 1 and 8. Dose escalation depended on dose-limiting toxicity (DLT) rate during the first 3-week period. Paired skin biopsies were evaluated for phosphorylated S6 (pS6) as marker of mTOR (mammalian target of rapamycin) inhibition. Pharmacokinetics and preclinical evaluation of efficacy using two different sarcoma cell lines and leiomyosarcoma xenografts were also conducted.

Results:

Three DLTs were observed: grade 3 transaminitis, grade 3 thrombocytopenia and grade 4 thrombocytopenia. Common treatment-related adverse events included anaemia, neutropenia, thrombocytopenia and transaminitis. Pharmacodynamic analyses demonstrated mTOR inhibition with sirolimus 5 mg and PK showed no influence of sirolimus concentrations on gemcitabine clearance. In vitro and in vivo studies suggested mTOR pathway hyperactivation by gemcitabine that was reversed by sirolimus. Tumour growth in leiomyosarcoma xenografts was dramatically inhibited by the treatment.

Conclusions:

Recommended dose was sirolimus 5 mg per 24 h plus gemcitabine 800 mg m⁻². Antitumour activity in preclinical sarcoma models and mTOR signalling inhibition were observed. A phase II study is currently ongoing.

EphA2-induced angiogenesis in ewing sarcoma cells works through bFGF production and is dependent on caveolin-1

Angiogenesis is the result of the combined activity of the tumor microenvironment and signaling molecules. The angiogenic switch is represented as an imbalance between pro- and anti-angiogenic factors and is a rate-limiting step in the development of tumors. Eph receptor tyrosine kinases and their membrane-anchored ligands, known as ephrins, constitute the largest receptor tyrosine kinase (RTK) subfamily and are considered a major family of pro-angiogenic RTKs. Ewing sarcoma (EWS) is a highly aggressive bone and soft tissue tumor affecting children and young adults. As other solid tumors, EWS are reliant on a functional vascular network for the delivery of nutrients and oxygen and for the removal of waste. Based on the biological roles of EphA2 in promoting angiogenesis, we explored the functional role of this receptor and its relationship with caveolin-1 (CAV1) in EWS angiogenesis. We demonstrated that lack of CAV1 results in a significant reduction in micro vascular density (MVD) on 3 different in vivo models. In vitro, this phenomenon correlated with inactivation of EphA2 receptor, lack of AKT response and downregulation of bFGF. We also demonstrated that secreted bFGF from EWS cells acted as chemoattractant for endothelial cells. Furthermore, interaction between EphA2 and CAV1 was necessary for the right localization and signaling of the receptor to produce bFGF through AKT and promote migration of endothelial cells. Finally, introduction of a dominant-negative form of EphA2 into EWS cells mostly reproduced the effects occurred by CAV1 silencing, strongly suggesting that the axis EphA2-CAV1 participates in the promotion of endothelial cell migration toward the tumors favoring EWS angiogenesis.

Targeted therapies in sarcomas: challenging the challenge

Sarcomas are a heterogeneous group of mesenchymal malignancies that very often lead to death. Nowadays, chemotherapy is the only available treatment for most sarcomas but there are few active drugs and clinical results still remain very poor. Thus, there is an imperious need to find new therapeutic alternatives in order to improve sarcoma patient's outcome. During the last years, there have been described a number of new molecular pathways that have allowed us to know more about cancer biology and tumorigenesis. Sarcomas are one of the tumors in which more advances have been made. Identification of specific chromosomal translocations, some important pathways characterization such as mTOR pathway or the insulin-like growth factor pathway, the stunning development in angiogenesis knowledge, and brand new agents like viruses have lead to the development of new therapeutic options with promising results. This paper makes an exhaustive review of preclinical and clinical evidence of the most recent targeted therapies in sarcomas and provides a future view of treatments that may lead to improve prognosis of patients affected with this disease.

Caveolin-1 in sarcomas: friend or foe?

Sarcomas represent a heterogeneous group of tumors with a complex and difficult reproducible classification. Their pathogenesis is poorly understood and there are few effective treatment options for advanced disease. Caveolin-1 is a multifunctional scaffolding protein with multiple binding partners that regulates multiple cancer-associated processes including cellular transformation, tumor growth, cell death and survival, multidrug resistance, angiogenesis, cell migration and metastasis. However, ambiguous roles have been ascribed to caveolin-1 in signal transduction and cancer, including sarcomas. In particular, evidence indicating that caveolin-1 function is cell context dependent has been repeatedly reported. Caveolin-1 appears to act as a tumor suppressor protein at early stages of cancer progression. In contrast, a growing body of evidence indicates that caveolin-1 is up-regulated in several multidrug-resistant and metastatic cancer cell lines and human tumor specimens. This review is focused on the role of caveolin-1 in several soft tissue and bone sarcomas and discusses the use of this protein as a potential diagnostic and prognostic marker and as a therapeutic target.

Caveolin-1 modulates the ability of Ewing's sarcoma to metastasize

Metastasis is the final stage of tumor progression and is thought to be responsible for up to 90% of deaths associated with solid tumors. Caveolin-1 (CAV1) regulates multiple cancer-associated processes related to malignant tumor progression. In the present study, we tested the hypothesis that CAV1 modulates the metastatic ability of cells from the Ewing's sarcoma family of tumors (ESFT). First, we analyzed the expression of CAV1 by immunostaining a tissue microarray containing 43 paraffin-embedded ESFT tumors with known EWS translocations. Even though no evidence was found for a significant association between CAV1 expression and stage, size or tumor site, all metastatic samples (10 of 10) had significantly high CAV1 expression, suggesting that high CAV1 content could positively contribute to enhance ESFT metastasis. To determine the effect of CAV1 on the migratory and invasive capabilities of ESFT cells, we knocked down CAV1 expression in TC252 and A673 cells by stably transfecting a previously validated shRNA construct. In vitro, migration and invasion assays showed that for both cell lines, CAV1 knocked-down cells migrated and invaded significantly less (P ≤ 0.01) than control cells. Moreover, control A673 cells introduced into BALB/c nude mice by tail vein injection strongly colonized the lungs. In contrast, animals injected with CAV1 knocked-down cells showed either no incidence of metastasis or developed lung metastases after a significant delay (P < 0.0001). Finally, we show that the molecular mechanisms by which CAV1 carries out its key role in regulating ESFT metastasis involve matrix metalloproteinase production and activation as well as the control of the expression of SPARC, a known determinant of lung colonization.