Cationic LNP-formulated mRNA expressing Tie2-agonist in the lung endothelium prevents pulmonary vascular leakage

Dysfunction of endothelial cells (ECs) lining the inner surface of blood vessels are causative for a number of diseases. Hence, the ability to therapeutically modulate gene expression within ECs is of high therapeutic value in treating diseases such as those associated with lung edema. mRNAs formulated with lipid nanoparticles (LNPs) have emerged as a new drug modality to induce transient protein expression for modulating disease-relevant signal transduction pathways. In the study presented here, we tested the effect of a novel synthetic, nucleoside-modified mRNA encoding COMP-Ang1 (mRNA-76) formulated into a cationic LNP on attenuating inflammation-induced vascular leakage. After intravenous injection, the respective mRNA was found to be delivered almost exclusively to the ECs of the lung, while sparing other vascular beds and bypassing the liver. The mode of action of mRNA-76, such as its activation of the Tie2 signal transduction pathway, was tested by pharmacological studies in vitro and in vivo in respective mouse models. mRNA-76 was found to prevent lung vascular leakage/lung edema as well as neutrophil infiltration in a lipopolysaccharide-challenging model.

Brassinin Promotes the Degradation of Tie2 and FGFR1 in Endothelial Cells and Inhibits Triple-Negative Breast Cancer Angiogenesis

Simple Summary

Brassinin is a natural compound enriched in several commonly consumed vegetables, such as broccoli and cabbages. It shows potent anti-cancer activity against several cancers. However, its effects on triple-negative breast cancer (TNBC), an aggressive subtype with limited treatment options, remain elusive so far. Therefore, we investigated the effects of brassinin on TNBC angiogenesis and growth. Our results demonstrate that brassinin inhibits TNBC growth preferentially through inhibiting the angiogenic activity of endothelial cells (ECs). Additional in-vitro analyses revealed that this effect may be mediated by brassinin-stimulated degradation of two pivotal angiogenesis-related receptors in ECs: Tie2 and fibroblast growth factor receptor 1. These findings provide novel insights into the cellular and molecular mechanisms underlying the anti-cancer activity of brassinin and indicate that this phytochemical may be a promising lead compound or drug candidate for TNBC treatment.

Abstract

Brassinin, a phytoalexin derived from cruciferous vegetables, has been reported to exhibit anti-cancer activity in multiple cancer types. However, its effects on triple-negative breast cancer (TNBC) development and the underlying mechanisms have not been elucidated so far. In this study, we demonstrated in vitro that brassinin preferentially reduces the viability of endothelial cells (ECs) when compared to other cell types of the tumor microenvironment, including TNBC cells, pericytes, and fibroblasts. Moreover, brassinin at non-cytotoxic doses significantly suppressed the proliferation, migration, tube formation, and spheroid sprouting of ECs. It also efficiently inhibited angiogenesis in an ex-vivo aortic ring assay and an in-vivo Matrigel plug assay. Daily intraperitoneal injection of brassinin significantly reduced tumor size, microvessel density, as well as the perfusion of tumor microvessels in a dorsal skinfold chamber model of TNBC. Mechanistic analyses showed that brassinin selectively stimulates the degradation of Tie2 and fibroblast growth factor receptor 1 in ECs, leading to the down-regulation of the AKT and extracellular signal-regulated kinase pathways. These findings demonstrate a preferential and potent anti-angiogenic activity of brassinin, which may be the main mechanism of its anti-tumor action. Accordingly, this phytochemical represents a promising candidate for the future anti-angiogenic treatment of TNBC.

The Angiopoietin-Tie2 Pathway in Critical Illness

Lethal features of sepsis and acute respiratory distress syndrome (ARDS) relate to the health of small blood vessels. For example, alveolar infiltration with proteinaceous fluid is often driven by breach of the microvascular barrier. Spontaneous thrombus formation within inflamed microvessels exacerbates organ ischemia, and in its final stages, erupts into overt disseminated intravascular coagulation. Disruption of an endothelial signaling axis, the Angiopoietin-Tie2 pathway, may mediate the abrupt transition from microvascular integrity to pathologic disruption. This review summarizes preclinical and clinical results that implicate the Tie2 pathway as a promising target to restore microvascular health in sepsis and ARDS.

Vascular Endothelial Receptor Tyrosine Phosphatase: Identification of Novel Substrates Related to Junctions and a Ternary Complex with EPHB4 and TIE2

Vascular endothelial protein tyrosine phosphatase (VE-PTP, PTPRB) is a receptor type phosphatase that is crucial for the regulation of endothelial junctions and blood vessel development. We and others have shown recently that VE-PTP regulates vascular integrity by dephosphorylating substrates that are key players in endothelial junction stability, such as the angiopoietin receptor TIE2, the endothelial adherens junction protein VE-cadherin and the vascular endothelial growth factor receptor VEGFR2. Here, we have systematically searched for novel substrates of VE-PTP in endothelial cells by utilizing two approaches. First, we studied changes in the endothelial phosphoproteome on exposing cells to a highly VE-PTP-specific phosphatase inhibitor followed by affinity isolation and mass-spectrometric analysis of phosphorylated proteins by phosphotyrosine-specific antibodies. Second, we used a substrate trapping mutant of VE-PTP to pull down phosphorylated substrates in combination with SILAC-based quantitative mass spectrometry measurements. We identified a set of substrate candidates of VE-PTP, of which a remarkably large fraction (29%) is related to cell junctions. Several of those were found in both screens and displayed very high connectivity in predicted functional interaction networks. The receptor protein tyrosine kinase EPHB4 was the most prominently phosphorylated protein on VE-PTP inhibition among those VE-PTP targets that were identified by both proteomic approaches. Further analysis revealed that EPHB4 forms a ternary complex with VE-PTP and TIE2 in endothelial cells. VE-PTP controls the phosphorylation of each of these two tyrosine kinase receptors. Despite their simultaneous presence in a ternary complex, stimulating each of the receptors with their own specific ligand did not cross-activate the respective partner receptor. Our systematic approach has led to the identification of novel substrates of VE-PTP, of which many are relevant for the control of cellular junctions further promoting the importance of VE-PTP as a key player of junctional signaling.

c-Cbl: An Important Regulator and a Target in Angiogenesis and Tumorigenesis

Casitas B lineage lymphoma (c-Cbl) is a multifunctional protein with a ubiquitin E3 ligase activity capable of degrading diverse sets of proteins. Although previous work had focused mainly on c-Cbl mutations in humans with hematological malignancies, recent emerging evidence suggests a critical role of c-Cbl in angiogenesis and human solid organ tumors. The combination of its unique structure, modular function, and ability to channelize cues from a rich network of signaling cascades, empowers c-Cbl to assume a central role in these disease models. This review consolidates the structural and functional insights based on recent studies that highlight c-Cbl as a target with tantalizing therapeutic potential in various models of angiogenesis and tumorigenesis.

The Angiopoietin-Tie2 Signaling Axis in Systemic Inflammation

Systemic inflammation is a hallmark of commonly encountered diseases ranging from bacterial sepsis to sterile syndromes such as major trauma. Derangements in the host vasculature contribute to the cardinal manifestations of sepsis in profound ways. Recent studies of control pathways regulating the vascular endothelium have illuminated how this single cell layer toggles between quiescence and activation to affect the development of shock and multiorgan dysfunction. This article focuses on one such control pathway, the Tie2 receptor and its ligands the angiopoietins, to describe a growing body of genetic, biochemical, mechanistic, and human studies that implicate Tie2 as a critical switch. In health, activated Tie2 maintains the endothelium in a quiescent state characterized by dynamic barrier function and antiadhesion against circulating leukocytes. In sepsis and related diseases, expression of the angiopoietins becomes markedly imbalanced and Tie2 signaling is greatly attenuated. These rapid molecular changes potentiate pathophysiologic responses throughout the body, resulting in injurious vascular leakage and organ inflammation. The Tie2 axis, therefore, may be a promising avenue for future translational studies.

Tubeimoside-1 suppresses tumor angiogenesis by stimulation of proteasomal VEGFR2 and Tie2 degradation in a non-small cell lung cancer xenograft model

Tubeimoside-1 (TBMS1) is a potent anti-tumor phytochemical. Its functional and molecular mode of action, however, remains elusive so far. Since angiogenesis is essential for tumor progression and metastasis, we herein investigated the anti-angiogenic effects of the compound. In a non-small cell lung cancer (NSCLC) xenograft model we found that treatment of CD1 nu/nu mice with TBMS1 (5 mg/kg) significantly suppressed the growth and vascularization of NCI-H460 flank tumors. Moreover, TBMS1 dose-dependently reduced vascular sprouting in a rat aortic ring assay. In vitro, TBMS1 induced endothelial cell apoptosis without decreasing the viability of NSCLC tumor cells and inhibited the migration of endothelial cells by disturbing their actin filament organization. TBMS1 further stimulated the proteasomal degradation of vascular endothelial growth factor receptor-2 (VEGFR2) and Tie2 in endothelial cells, which down-regulated AKT/mTOR signaling. These findings indicate that TBMS1 represents a novel phytochemical for anti-angiogenic treatment of cancer and other angiogenesis-related diseases.

The angiopoietin-Tie2 signaling axis in the vascular leakage of systemic inflammation

The ability of small blood vessels to undergo rapid, reversible morphological changes is essential for the adaptive response to tissue injury or local infection. A canonical feature of this response is transient hyperpermeability. However, when leakiness is profound or persistent, adverse consequences accrue to the host, including organ dysfunction and shock. A growing body of literature identifies the Tie2 receptor, a transmembrane tyrosine kinase highly enriched in the endothelium, as an important regulator of vascular barrier function in health and in disease. The principal ligands of Tie2, Angiopoietins 1 and 2, exert opposite effects on this receptor in the context of inflammation. This review will focus on recent studies that have illuminated novel aspects of the exquisitely controlled Tie2 signaling axis while proposing unanswered questions and future directions for this field of study.

Angiopoietin 1 and angiopoietin 2 are associated with medial thickening of hepatic arterial branches in biliary atresia

BACKGROUND

Biliary atresia (BA) is an infantile disorder characterized by progressive sclerosing cholangiopathy leading to biliary obstruction. First-line treatment of BA is hepatoportoenterostomy, the prognosis of which is related to age at surgery and to histological variables such as extent of fibrosis and ductular reaction. Hepatic arterial medial thickening (MT) suggests an arteriopathy in BA pathogenesis. We evaluated the expression of angiopoietin (ANGPT)/tyrosine kinase with immunoglobulin-like and epidermal growth factor-like domains 2 (TIE2) system in liver samples obtained from patients with BA, correlating it with MT, variables associated with disease severity, and postoperative prognosis.

METHODS

ANGPT1, ANGPT2, and TIE2 expression levels were assessed by quantitative PCR in liver samples obtained from BA patients (n = 23) at portoenterostomy and age-matched infants with intrahepatic cholestasis (IHC; n = 7). Histological variables were morphometrically assessed.

RESULTS

ANGPT1 and ANGPT2 were overexpressed in BA in comparison with IHC (P = 0.024 and P = 0.029, respectively). In BA, ANGPTs expression was positively correlated with MT (ANGPT1: rs = 0.59, P = 0.013; ANGPT2: rs = 0.52, P = 0.032), not with the variables associated with disease severity. TIE2 and ANGPTs expression levels were negatively correlated (ANGPT1: rs = -0.73, P < 0.001; ANGPT2: rs = -0.54, P = 0.007).

CONCLUSION

In BA, there is overexpression of both ANGPT1 and ANGPT2, which is correlated with MT but not with age at portoenterostomy or with the histological variables associated with disease severity at the time of procedure.

Inhibition of proliferation, sprouting, tube formation and Tie2 signaling of lymphatic endothelial cells by the histone deacetylase inhibitor SAHA

Histone deacetylase (HDAC) inhibitors exert potent inhibitory effects on various types of human cancer. The pioneer drug suberoylanilide hydroxamic acid (SAHA) is currently used in the clinic for cancer treatment. However, the effect of SAHA on tumor lymphangiogenesis is unclear. We recently showed that SAHA suppresses the expression and production of pro-lymphagenic factor vascular endothelial growth factor‑C (VEGF-C) in breast cancer cells. In the present study, the effect of SAHA on lymphatic endothelial cells (LECs) was examined. We generated a lymphatic-like endothelial cell line (named FP01) by overexpressing the master LEC transcription factor PROX1 in EA.hy926 endothelial cells. This cell line exhibited a gene expression pattern and phenotype similar to primarily cultured LECs. SAHA inhibited cell cycle progression and proliferation of FP01 cells. In addition, SAHA suppressed sprouting and tube formation in these cells. Moreover, SAHA attenuated the angiopoietin (Ang)/Tie signaling pathway which plays important roles in the regulation of LEC function. FP01 cells expressed Ang1, Ang2, Tie1 and Tie2, and SAHA dose-dependently reduced the expression of Tie2 in these cells. Tie2 promoter activity was attenuated by SAHA indicating a transcriptional repression. Importantly, Tie2 protein was significantly reduced by SAHA at the concentration in which no alteration of Tie2 mRNA was detected. We found that SAHA enhanced Tie2 protein degradation via the ubiquitin-proteasome pathway, and the expression of c-Cbl, the E3 ligase for Tie2 ubiquitination, rapidly increased after SAHA treatment. Knockdown of c-Cbl reversed SAHA‑induced Tie2 protein degradation. Taken together, our results demonstrate that SAHA impairs the proliferation, sprouting and tube formation of LECs and attenuates Ang/Tie signaling in LECs by downregulating Tie-2 via transcriptional and post-transcriptional mechanisms.

Myoferlin gene silencing decreases Tie-2 expression in vitro and angiogenesis in vivo

Angiogenesis consists in the growth of new blood vessels from pre-existing ones. Although anti-angiogenesis interventions have been shown to have therapeutic properties in human diseases such as cancer, their effect is only partial and the identification of novel modulators of angiogenesis is warranted. Recently, we reported the unexpected proteomic identification in endothelial cells (EC) of Myoferlin, a member of the Ferlin family of transmembrane proteins. Ferlins are well known to regulate the fusion of lipid vesicles at the plasma membrane in muscle cells, and we showed that Myoferlin gene knockdown not only decreases lipid vesicle fusion in EC but also attenuates Vascular Endothelial Growth Factor (VEGF) Receptor-2 (VEGFR-2) expression. Herein, we show that Myoferlin gene silencing in cultured EC also results in attenuated expression of a second tyrosine kinase receptor, Tie-2, which is another well-described angiogenic receptor. Most importantly, we provide evidence that delivery of a low-volume Myoferlin siRNA preparation in mouse tissues results in attenuated angiogenesis and edema formation. This provides the first evidence that acute Myoferlin knockdown has anti-angiogenic effects and validates Myoferlin as an anti-angiogenesis target. Furthermore, this supports the unexpected but increasingly accepted concept that proper tyrosine kinase receptors expression at the plasma membrane requires Myoferlin.

Vascular endothelial growth factor and epidermal growth factor signaling pathways as therapeutic targets for colorectal cancer

Treatment of colorectal cancer (CRC) has developed considerably over the past decade, especially in the areas of targeted therapeutics and biomarker development. Multiple cellular pathways influence the growth and metastatic potential of CRC. Targeted therapies have been designed to interfere with specific molecular events in pathways that mediate tumor growth and progression. Preclinical and clinical studies have shown that the epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) are valid therapeutic targets for patients with CRC. Monoclonal antibodies and tyrosine kinase inhibitors have been developed to target EGFR, VEGF, and VEGF receptors (VEGFRs) and are important additions to CRC treatment options. We review the most recent data on the VEGF and EGFR signaling pathways and therapeutic reagents designed to target them, provide insights into their mechanisms, and describe results from recent clinical trials.