Cell type-specific expression of angiopoietin-1 and angiopoietin-2 suggests a role in glioblastoma angiogenesis

Beyond VEGF: Angiopoietin-Tie Signaling Pathway in Diabetic Retinopathy

Complications from diabetic retinopathy such as diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) constitute leading causes of preventable vision loss in working-age patients. Since vascular endothelial growth factor (VEGF) plays a major role in the pathogenesis of these complications, VEGF inhibitors have been the cornerstone of their treatment. Anti-VEGF monotherapy is an effective but burdensome treatment for DME. However, due to the intensive and burdensome treatment, most patients in routine clinical practice are undertreated, and therefore, their outcomes are compromised. Even in adequately treated patients, persistent DME is reported anywhere from 30% to 60% depending on the drug used. PDR is currently treated by anti-VEGF, panretinal photocoagulation (PRP) or a combination of both. Similarly, a number of eyes, despite these treatments, continue to progress to tractional retinal detachment and vitreous hemorrhage. Clearly there are other molecular pathways other than VEGF involved in the pathogenesis of DME and PDR. One of these pathways is the angiopoietin-Tie signaling pathway. Angiopoietin 1 (Ang1) plays a major role in maintaining vascular quiescence and stability. It acts as a molecular brake against vascular destabilization and inflammation that is usually promoted by angiopoietin 2 (Ang2). Several pathological conditions including chronic hyperglycemia lead to Ang2 upregulation. Recent regulatory approval of the bi-specific antibody, faricimab, may improve long term outcomes in DME. It targets both the Ang/Tie and VEGF pathways. The YOSEMITE and RHINE were multicenter, double-masked, randomized non-inferiority phase 3 clinical trials that compared faricimab to aflibercept in eyes with center-involved DME. At 12 months of follow-up, faricimab demonstrated non-inferior vision gains, improved anatomic outcomes and a potential for extended dosing when compared to aflibercept. The 2-year results of the YOSEMITE and RHINE trials demonstrated that the anatomic and functional results obtained at the 1 year follow-up were maintained. Short term outcomes of previously treated and treatment-naive eyes with DME that were treated with faricimab during routine clinical practice suggest a beneficial effect of faricimab over other agents. Targeting of Ang2 has been reported by several other means including VE-PTP inhibitors, integrin binding peptide and surrobodies.

Status of alternative angiogenic pathways in glioblastoma resected under and after bevacizumab treatment

Glioblastoma multiforme (GBM) acquires resistance to bevacizumab (Bev) treatment. Bev affects angiogenic factors other than vascular endothelial growth factor (VEGF), which are poorly understood. We investigated changes in angiogenic factors under and after Bev therapy, including angiopoietin-1 (ANGPT1), angiopoietin-2 (ANGPT2), placental growth factor (PLGF), fibroblast growth factor 2, and ephrin A2 (EphA2). Fifty-four GBM tissues, including 28 specimens from 14 cases as paired specimens from the same patient obtained in three settings: initial tumor resection (naïve Bev), tumors resected following Bev therapy (effective Bev), and recurrent tumors after Bev therapy (refractory Bev). Immunohistochemistry assessed their expressions in tumor vessels and its correlation with recurrent MRI patterns. PLGF expression was higher in the effective Bev group than in the naïve Bev group (p = 0.024) and remained high in the refractory Bev group. ANGPT2 and EphA2 expressions were higher in the refractory Bev group than in the naïve Bev group (p = 0.047 and 0.028, respectively). PLGF expression was higher in the refractory Bev group compared with the naïve Bev group for paired specimens (p = 0.036). PLGF was more abundant in T2 diffuse/circumscribe patterns (p = 0.046). This is the first study to evaluate angiogenic factors other than VEGF during effective and refractory Bev therapy in patient-derived specimens.

Proteomic Associations of NT-proBNP (N-Terminal Pro-B-Type Natriuretic Peptide) in Heart Failure With Preserved Ejection Fraction

BACKGROUND

NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels are variably elevated in heart failure with preserved ejection fraction (HFpEF), even in the presence of increased left ventricular filling pressures. NT-proBNP levels are prognostic in HFpEF and have been used as an inclusion criterion for several recent randomized clinical trials. However, the underlying biologic differences between HFpEF participants with high and low NT-proBNP levels remain to be fully understood.

METHODS

We measured 4928 proteins using an aptamer-based proteomic assay (SOMAScan) in available plasma samples from 2 cohorts: (1) Participants with HFpEF enrolled in the PHFS (Penn Heart Failure Study; n=253); (2) TOPCAT (Treatment of Preserved Cardiac Function Heart Failure With an Aldosterone Antagonist Trial) participants in the Americas (n=218). We assessed the relationship between SOMAScan-derived plasma NT-proBNP and levels of other proteins available in the SOMAScan assay version 4 using robust linear regression, with correction for multiple comparisons, followed by pathway analysis.

RESULTS

NT-proBNP levels exhibited prominent proteome-wide associations in PHFS and TOPCAT cohorts. Proteins most strongly associated with NT-proBNP in both cohorts included SVEP1 (sushi, von Willebrand factor type-A, epidermal growth factor, and pentraxin domain containing 1; βTOPCAT=0.539; P<0.0001; βPHFS=0.516; P<0.0001) and ANGPT2 (angiopoietin 2; βTOPCAT=0.571; P<0.0001; βPHFS=0.459; P<0.0001). Canonical pathway analysis demonstrated consistent associations with multiple pathways related to fibrosis and inflammation. These included hepatic fibrosis and inhibition of matrix metalloproteases. Analyses using cut points corresponding to estimated quantitative concentrations of 360 pg/mL (and 480 pg/mL in atrial fibrillation) revealed similar proteomic associations.

CONCLUSIONS

Circulating NT-proBNP levels exhibit prominent proteomic associations in HFpEF. Our findings suggest that higher NT-proBNP levels in HFpEF are a marker of fibrosis and inflammation. These findings will aid the interpretation of NT-proBNP levels in HFpEF and may guide the selection of participants in future HFpEF clinical trials.

Therapeutic targeting of angiopoietins in tumor angiogenesis and cancer development

The formation and progression of tumors in humans are linked to the abnormal development of new blood vessels known as neo-angiogenesis. Angiogenesis is a broad word that encompasses endothelial cell migration, proliferation, tube formation, and intussusception, as well as peri-EC recruitment and extracellular matrix formation. Tumor angiogenesis is regulated by angiogenic factors, out of which some of the most potent angiogenic factors such as vascular endothelial growth factor and Angiopoietins (ANGs) in the body are produced by macrophages and other immune cells within the tumor microenvironment. ANGs have a distinct function in tumor angiogenesis and behavior. ANG1, ANG 2, ANG 3, and ANG 4 are the family members of ANG out of which ANG2 has been extensively investigated owing to its unique role in modifying angiogenesis and its tight association with tumor progression, growth, and invasion/metastasis, which makes it an excellent candidate for therapeutic intervention in human malignancies. ANG modulators have demonstrated encouraging outcomes in the treatment of tumor development, either alone or in conjunction with VEGF inhibitors. Future development of more ANG modulators targeting other ANGs is needed. The implication of ANG1, ANG3, and ANG4 as probable therapeutic targets for anti-angiogenesis treatment in tumor development should be also evaluated. The article has described the role of ANG in tumor angiogenesis as well as tumor growth and the treatment strategies modulating ANGs in tumor angiogenesis as demonstrated in clinical studies. The pharmacological modulation of ANGs and ANG-regulated pathways that are responsible for tumor angiogenesis and cancer development should be evaluated for the development of future molecular therapies.

Acquired temozolomide resistance instructs patterns of glioblastoma behavior in gelatin hydrogels

Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is a key factor contributing to abysmal prognosis, with less than 15 months median overall survival. Aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual highly invasive tumor cells after surgical resection and radiotherapy. Here, we report a three-dimensional (3D) engineered model of acquired TMZ resistance using two isogenically-matched sets of GBM cell lines encapsulated in gelatin methacrylol hydrogels. We benchmark response of TMZ-resistant vs. TMZ-sensitive GBM cell lines within the gelatin-based extracellular matrix platform and further validate drug response at physiologically relevant TMZ concentrations. We show changes in drug sensitivity, cell invasion, and matrix-remodeling cytokine production as the result of acquired TMZ resistance. This platform lays the foundation for future investigations targeting key elements of the GBM tumor microenvironment to combat GBM's devastating impact by advancing our understanding of GBM progression and treatment response to guide the development of novel treatment strategies.

Teaser

A hydrogel model to investigate the impact of acquired drug resistance on functional response in glioblastoma.

Tumor Niches: Perspectives for Targeted Therapies in Glioblastoma

Significance: Glioblastoma (GBM), the most common and lethal primary brain tumor with a median survival rate of only 15 months and a 5-year survival rate of only 6.8%, remains largely incurable despite the intensive multimodal treatment of surgical resection and radiochemotherapy. Developing effective new therapies is an unmet need for patients with GBM. Recent Advances: Targeted therapies, such as antiangiogenesis therapy and immunotherapy, show great promise in treating GBM based upon increasing knowledge about brain tumor biology. Single-cell transcriptomics reveals the plasticity, heterogeneity, and dynamics of tumor cells during GBM development and progression. Critical Issues: While antiangiogenesis therapy and immunotherapy have been highly effective in some types of cancer, the disappointing results from clinical trials represent continued challenges in applying these treatments to GBM. Molecular and cellular heterogeneity of GBM is developed temporally and spatially, which profoundly contributes to therapeutic resistance and tumor recurrence. Future Directions: Deciphering mechanisms of tumor heterogeneity and mapping tumor niche trajectories and functions will provide a foundation for the development of more effective therapies for GBM patients. In this review, we discuss five different tumor niches and the intercellular and intracellular communications among these niches, including the perivascular, hypoxic, invasive, immunosuppressive, and glioma-stem cell niches. We also highlight the cellular and molecular biology of these niches and discuss potential strategies to target these tumor niches for GBM therapy. Antioxid. Redox Signal. 39, 904-922.

KRAS mutation-driven angiopoietin 2 bestows anti-VEGF resistance in epithelial carcinomas

Defining reliable surrogate markers and overcoming drug resistance are the most challenging issues for improving therapeutic outcomes of antiangiogenic drugs (AADs) in cancer patients. At the time of this writing, no biomarkers are clinically available to predict AAD therapeutic benefits and drug resistance. Here, we uncovered a unique mechanism of AAD resistance in epithelial carcinomas with KRAS mutations that targeted angiopoietin 2 (ANG2) to circumvent antivascular endothelial growth factor (anti-VEGF) responses. Mechanistically, KRAS mutations up-regulated the FOXC2 transcription factor that directly elevated ANG2 expression at the transcriptional level. ANG2 bestowed anti-VEGF resistance as an alternative pathway to augment VEGF-independent tumor angiogenesis. Most colorectal and pancreatic cancers with KRAS mutations were intrinsically resistant to monotherapies of anti-VEGF or anti-ANG2 drugs. However, combination therapy with anti-VEGF and anti-ANG2 drugs produced synergistic and potent anticancer effects in KRAS-mutated cancers. Together, these data demonstrate that KRAS mutations in tumors serve as a predictive marker for anti-VEGF resistance and are susceptible to combination therapy with anti-VEGF and anti-ANG2 drugs.

Angiogenic signaling pathways and anti-angiogenic therapy for cancer

Angiogenesis, the formation of new blood vessels, is a complex and dynamic process regulated by various pro- and anti-angiogenic molecules, which plays a crucial role in tumor growth, invasion, and metastasis. With the advances in molecular and cellular biology, various biomolecules such as growth factors, chemokines, and adhesion factors involved in tumor angiogenesis has gradually been elucidated. Targeted therapeutic research based on these molecules has driven anti-angiogenic treatment to become a promising strategy in anti-tumor therapy. The most widely used anti-angiogenic agents include monoclonal antibodies and tyrosine kinase inhibitors (TKIs) targeting vascular endothelial growth factor (VEGF) pathway. However, the clinical benefit of this modality has still been limited due to several defects such as adverse events, acquired drug resistance, tumor recurrence, and lack of validated biomarkers, which impel further research on mechanisms of tumor angiogenesis, the development of multiple drugs and the combination therapy to figure out how to improve the therapeutic efficacy. Here, we broadly summarize various signaling pathways in tumor angiogenesis and discuss the development and current challenges of anti-angiogenic therapy. We also propose several new promising approaches to improve anti-angiogenic efficacy and provide a perspective for the development and research of anti-angiogenic therapy.

Nucleic acid drug vectors for diagnosis and treatment of brain diseases

Nucleic acid drugs have the advantages of rich target selection, simple in design, good and enduring effect. They have been demonstrated to have irreplaceable superiority in brain disease treatment, while vectors are a decisive factor in therapeutic efficacy. Strict physiological barriers, such as degradation and clearance in circulation, blood-brain barrier, cellular uptake, endosome/lysosome barriers, release, obstruct the delivery of nucleic acid drugs to the brain by the vectors. Nucleic acid drugs against a single target are inefficient in treating brain diseases of complex pathogenesis. Differences between individual patients lead to severe uncertainties in brain disease treatment with nucleic acid drugs. In this Review, we briefly summarize the classification of nucleic acid drugs. Next, we discuss physiological barriers during drug delivery and universal coping strategies and introduce the application methods of these universal strategies to nucleic acid drug vectors. Subsequently, we explore nucleic acid drug-based multidrug regimens for the combination treatment of brain diseases and the construction of the corresponding vectors. In the following, we address the feasibility of patient stratification and personalized therapy through diagnostic information from medical imaging and the manner of introducing contrast agents into vectors. Finally, we take a perspective on the future feasibility and remaining challenges of vector-based integrated diagnosis and gene therapy for brain diseases.

A molecular interactome of the glioblastoma perivascular niche reveals integrin binding sialoprotein as a mediator of tumor cell migration

Glioblastoma (GBM) is characterized by extensive microvascular hyperproliferation. In addition to supplying blood to the tumor, GBM vessels also provide trophic support to glioma cells and serve as conduits for migration into the surrounding brain, promoting recurrence. Here, we enrich CD31-expressing glioma vascular cells (GVCs) and A2B5-expressing glioma tumor cells (GTCs) from primary GBM and use RNA sequencing to create a comprehensive molecular interaction map of the secreted and extracellular factors elaborated by GVCs that can interact with receptors and membrane molecules on GTCs. To validate our findings, we utilize functional assays, including a hydrogel-based migration assay and in vivo mouse models to demonstrate that one identified factor, the little-studied integrin binding sialoprotein (IBSP), enhances tumor growth and promotes the migration of GTCs along the vasculature. This perivascular niche interactome will serve as a resource to the research community in defining the potential functions of the GBM vasculature.

Akt1-dependent expression of angiopoietin 1 and 2 in vascular smooth muscle cells leads to vascular stabilization

Retinal angiogenesis was delayed in VSMC-specific Akt1-deficient mice (Akt1^∆SMC) but not in Akt2^∆SMC mice. The proliferation of ECs, recruitment of pericytes, and coverage of VSMCs to the endothelium were defective in Akt1^∆SMC. The silencing of Akt1 in VSMCs led to the downregulation of angiopoietin 1 (Ang1) and the upregulation of Ang2. The activation of Notch3 in VSMCs was significantly reduced in the retinas of Akt1^∆SMC mice. Silencing Akt1 suppressed the activation of Notch3. Moreover, the silencing of Notch3 downregulated Ang1, whereas the overexpression of Notch3 intracellular domain (NICD3) enhanced Ang1 expression. The nuclear localization and transcriptional activity of yes-associated protein (YAP) were affected by the expression level of Akt1. Silencing YAP downregulated Ang2 expression, whereas overexpression of YAP showed the opposite results. Ang1 antibody and Ang2 suppressed endothelial sprouting of wild-type aortic tissues, whereas the Ang2 antibody and Ang1 facilitated the endothelial sprouting of aortic tissues from Akt1^∆SMC mice. Finally, severe hemorrhage was observed in Akt1^∆SMC mice, which was further facilitated under streptozotocin (STZ)-induced diabetic conditions. Therefore, the Akt1-Notch3/YAP-Ang1/2 signaling cascade in VSMCs might play an essential role in the paracrine regulation of endothelial function.

The potential of advanced MR techniques for precision radiotherapy of glioblastoma

As microscopic tumour infiltration of glioblastomas is not visible on conventional magnetic resonance (MR) imaging, an isotropic expansion of 1-2 cm around the visible tumour is applied to define the clinical target volume for radiotherapy. An opportunity to visualize microscopic infiltration arises with advanced MR imaging. In this review, various advanced MR biomarkers are explored that could improve target volume delineation for radiotherapy of glioblastomas. Various physiological processes in glioblastomas can be visualized with different advanced MR techniques. Combining maps of oxygen metabolism (CMRO₂), relative cerebral blood volume (rCBV), vessel size imaging (VSI), and apparent diffusion coefficient (ADC) or amide proton transfer (APT) can provide early information on tumour infiltration and high-risk regions of future recurrence. Oxygen consumption is increased 6 months prior to tumour progression being visible on conventional MR imaging. However, presence of the Warburg effect, marking a switch from an infiltrative to a proliferative phenotype, could result in CMRO₂ to appear unaltered in high-risk regions. Including information on biomarkers representing angiogenesis (rCBV and VSI) and hypercellularity (ADC) or protein concentration (APT) can omit misinterpretation due to the Warburg effect. Future research should evaluate these biomarkers in radiotherapy planning to explore the potential of advanced MR techniques to personalize target volume delineation with the aim to improve local tumour control and/or reduce radiation-induced toxicity.

Angiopoietin-2-induced lymphatic endothelial cell migration drives lymphangiogenesis via the β1 integrin-RhoA-formin axis

Lymphangiogenesis is an essential physiological process but also a determining factor in vascular-related pathological conditions. Angiopoietin-2 (Ang2) plays an important role in lymphatic vascular development and function and its upregulation has been reported in several vascular-related diseases, including cancer. Given the established role of the small GTPase RhoA on cytoskeleton-dependent endothelial functions, we investigated the relationship between RhoA and Ang2-induced cellular activities. This study shows that Ang2-driven human dermal lymphatic endothelial cell migration depends on RhoA. We demonstrate that Ang2-induced migration is independent of the Tie receptors, but dependent on β1 integrin-mediated RhoA activation with knockdown, pharmacological approaches, and protein sequencing experiments. Although the key proteins downstream of RhoA, Rho kinase (ROCK) and myosin light chain, were activated, blockade of ROCK did not abrogate the Ang2-driven migratory effect. However, formins, an alternative target of RhoA, were identified as key players, and especially FHOD1. The Ang2-RhoA relationship was explored in vivo, where lymphatic endothelial RhoA deficiency blocked Ang2-induced lymphangiogenesis, highlighting RhoA as an important target for anti-lymphangiogenic treatments.

Newcastle disease virus suppresses angiogenesis in mammary adenocarcinoma models

Cancer cells heavily utilise angiogenesis process to increase vascularisation for tumour mass growth and spread, so targeting this process is important to create an effective therapy. The AMHA1 strain of Newcastle disease virus (NDV) is an RNA virus with natural oncotropism. NDV induces direct tumour cytolysis, apoptosis, and immune stimulation. This work aimed to test NDV anti-angiogenic activity in a breast cancer model. To evaluate NDV’s antitumour effect in vivo, NDV was tested against mammary adenocarcinoma AN3 transplanted in syngeneic immunocompetent mice. In vivo antiangiogenic activity was evaluated by quantifying the blood vessels in treated and control tumour sections. In vitro experiments that exposed AMN3 mammary adenocarcinoma cells and Hep-2 laryngeal carcinoma cells to NDV at different time intervals were performed to identify the exact mechanism of anti-angiogenesis by using angiogenesis microarray slides. In vivo results showed significant tumour regression and significant decrease in blood vessel formation in treated tumour sections. The in vitro microarray analysis of 14 different angiogenesis factors revealed that NDV downregulated angiopoietin-1, angiopoietin-2, and epidermal growth factor in mammary adenocarcinoma cells. However, NDV elicited a different effect on Hep-2 as represented by the downregulation of inducible protein 10, intracellular adhesion molecule-1, and basic fibroblast growth factor beta in NDV-infected tumour cells. It was found out that microarray analysis results helped interpret the in vivo data. The results suggested that the NDV oncolytic strain reduced angiogenesis by interfering with angiogenesis factors that might reduce tumour cell proliferation, infiltration, and invasion.

Targeting Tie2 in the Tumor Microenvironment: From Angiogenesis to Dissemination

Simple Summary

The dissemination of cancer cells from their original location to distant organs where they grow, a process called metastasis, causes more than 90% of cancer deaths. The identification of the molecular mechanisms of metastasis and the development of anti-metastatic therapies are essential to increase patient survival. In recent years, targeting the tumor microenvironment has become a promising avenue to prevent both tumor growth and metastasis. As the tumor microenvironment contains not only cancer cells but also blood vessels, immune cells, and other non-cancerous cells, it is naïve to think that therapy only affects a single cell type in this complex environment. Here we review the importance, and ways to inhibit the function, of one therapeutic target: the receptor Tie2. Tie2 is a receptor present on the cell surface of several cell types within the tumor microenvironment and regulates tumor angiogenesis, growth, and metastasis to distant organs.

Abstract

The Tie2 receptor tyrosine kinase is expressed in vascular endothelial cells, tumor-associated macrophages, and tumor cells and has been a major focus of research in therapies targeting the tumor microenvironment. The most extensively studied Tie2 ligands are Angiopoietin 1 and 2 (Ang1, Ang2). Ang1 plays a critical role in vessel maturation, endothelial cell migration, and survival. Ang2, depending on the context, may function to disrupt connections between the endothelial cells and perivascular cells, promoting vascular regression. However, in the presence of VEGF-A, Ang2 instead promotes angiogenesis. Tie2-expressing macrophages play a critical role in both tumor angiogenesis and the dissemination of tumor cells from the primary tumor to secondary sites. Therefore, Ang-Tie2 signaling functions as an angiogenic switch during tumor progression and metastasis. Here we review the recent advances and complexities of targeting Tie2 signaling in the tumor microenvironment as a possible anti-angiogenic, and anti-metastatic, therapy and describe its use in combination with chemotherapy.

In Uveal Melanoma, Angiopoietin-2 but Not Angiopoietin-1 Is Increased in High-Risk Tumors, Providing a Potential Druggable Target

Uveal melanoma (UM) metastasize haematogeneously, and tumor blood vessel density is an important prognostic factor. We hypothesized that proangiogenic factors such as angiopoietin-1 (ANG-1) and angiopoietin-2 (ANG-2), two targetable cytokines, might play a role in tumor development and metastatic behavior. mRNA levels of ANG-1 and ANG-2 were determined in 64 tumors using an Illumina HT-12 v4 mRNA chip and compared to clinical, pathologic, and genetic tumor parameters. Tissue expression was also determined by immunohistochemistry (IHC). Samples of aqueous humor were collected from 83 UM-containing enucleated eyes and protein levels that were determined in a multiplex proximity extension assay. High tissue gene expression of ANG-2, but not of ANG-1, was associated with high tumor thickness, high largest basal diameter, involvement of the ciliary body, and with UM-related death (ANG-2 mRNA p < 0.001; ANG-2 aqueous protein p < 0.001). The presence of the ANG-2 protein in aqueous humor correlated with its mRNA expression in the tumor (r = 0.309, p = 0.03). IHC showed that ANG-2 was expressed in macrophages as well as tumor cells. The presence of ANG-2 in the tumor and in aqueous humor, especially in high-risk tumors, make ANG-2 a potential targetable cytokine in uveal melanoma.

Melatonin as an Adjuvant to Antiangiogenic Cancer Treatments

Melatonin is a hormone with different functions, antitumor actions being one of the most studied. Among its antitumor mechanisms is its ability to inhibit angiogenesis. Melatonin shows antiangiogenic effects in several types of tumors. Combination of melatonin and chemotherapeutic agents have a synergistic effect inhibiting angiogenesis. One of the undesirable effects of chemotherapy is the induction of pro-angiogenic factors, whilst the addition of melatonin is able to overcome these undesirable effects. This protective effect of the pineal hormone against angiogenesis might be one of the mechanisms underlying its anticancer effect, explaining, at least in part, why melatonin administration increases the sensitivity of tumors to the inhibitory effects exerted by ordinary chemotherapeutic agents. Melatonin has the ability to turn cancer totally resistant to chemotherapeutic agents into a more sensitive chemotherapy state. Definitely, melatonin regulates the expression and/or activity of many factors involved in angiogenesis which levels are affected (either positively or negatively) by chemotherapeutic agents. In addition, the pineal hormone has been proposed as a radiosensitizer, increasing the oncostatic effects of radiation on tumor cells. This review serves as a synopsis of the interaction between melatonin and angiogenesis, and we will outline some antiangiogenic mechanisms through which melatonin sensitizes cancer cells to treatments, such as radiotherapy or chemotherapy.

DPSCs treated by TGF-β1 regulate angiogenic sprouting of three-dimensionally co-cultured HUVECs and DPSCs through VEGF-Ang-Tie2 signaling

Background

Maintaining the stability and maturation of blood vessels is of paramount importance for the vessels to carry out their physiological function. Smooth muscle cells (SMCs), pericytes, and mesenchymal stem cells (MSCs) are involved in the maturation process of the newly formed vessels. The aim of this study was to investigate whether transforming growth factor beta 1 (TGF-β1) treatment could enhance pericyte-like properties of dental pulp stem cells (DPSCs) and how TGF-β1-treated DPSCs for 7 days (T-DPSCs) stabilize the newly formed blood vessels.

Methods

We utilized TGF-β1 to treat DPSCs for 1, 3, 5, and 7 days. Western blotting and immunofluorescence were used to analyze the expression of SMC markers. Functional contraction assay was conducted to assess the contractility of T-DPSCs. The effects of T-DPSC-conditioned media (T-DPSC-CM) on human umbilical vein endothelial cell (HUVEC) proliferation and migration were examined by MTT, wound healing, and trans-well migration assay. Most importantly, in vitro 3D co-culture spheroidal sprouting assay was used to investigate the regulating role of vascular endothelial growth factor (VEGF)-angiopoietin (Ang)-Tie2 signaling on angiogenic sprouting in 3D co-cultured spheroids of HUVECs and T-DPSCs. Angiopoietin 2 (Ang2) and VEGF were used to treat the co-cultured spheroids to explore their roles in angiogenic sprouting. Inhibitors for Tie2 and VEGFR2 were used to block Ang1/Tie2 and VFGF/VEGFR2 signaling.

Results

Western blotting and immunofluorescence showed that the expression of SMC-specific markers (α-SMA and SM22α) were significantly increased after treatment with TGF-β1. Contractility of T-DPSCs was greater compared with that of DPSCs. T-DPSC-CM inhibited HUVEC migration. In vitro sprouting assay demonstrated that T-DPSCs enclosed HUVECs, resembling pericyte-like cells. Compared to co-culture with DPSCs, a smaller number of HUVEC sprouting was observed when co-cultured with T-DPSCs. VEGF and Ang2 co-stimulation significantly enhanced sprouting in HUVEC and T-DPSC co-culture spheroids, whereas VEGF or Ang2 alone exerted insignificant effects on HUVEC sprouting. Blocking Tie2 signaling reversed the sprouting inhibition by T-DPSCs, while blocking VEGF receptor (VEGFR) signaling boosted the sprouting inhibition by T-DPSCs.

Conclusions

This study revealed that TGF-β1 can induce DPSC differentiation into functional pericyte-like cells. T-DPSCs maintain vessel stability through Ang1/Tie2 and VEGF/VEGFR2 signaling.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02349-y.

ΔNp73/ETS2 complex drives glioblastoma pathogenesis- targeting downstream mediators by rebastinib prolongs survival in preclinical models of glioblastoma

BACKGROUND

Glioblastoma (GBM) remains one of the least successfully treated cancers. It is essential to understand the basic biology of this lethal disease and investigate novel pharmacological targets to treat GBM. The aims of this study were to determine the biological consequences of elevated expression of ΔNp73, an N-terminal truncated isoform of TP73, and to evaluate targeting of its downstream mediators, the angiopoietin 1 (ANGPT1)/tunica interna endothelial cell kinase 2 (Tie2) axis, by using a highly potent, orally available small-molecule inhibitor (rebastinib) in GBM.

METHODS

ΔNp73 expression was assessed in glioma sphere cultures, xenograft glioblastoma tumors, and glioblastoma patients by western blot, quantitative reverse transcription PCR, and immunohistochemistry. Immunoprecipitation, chromatin immunoprecipitation (ChiP) and sequential ChIP were performed to determine the interaction between ΔNp73 and E26 transformation-specific (ETS) proto-oncogene 2 (ETS2) proteins. The oncogenic consequences of ΔNp73 expression in glioblastomas were examined by in vitro and in vivo experiments, including orthotopic zebrafish and mouse intracranial-injection models. Effects of rebastinib on growth of established tumors and survival were examined in an intracranial-injection mouse model.

RESULTS

ΔNp73 upregulates both ANGPT1 and Tie2 transcriptionally through ETS conserved binding sites on the promoters by interacting with ETS2. Elevated expression of ΔNp73 promotes tumor progression by mediating angiogenesis and survival. Therapeutic targeting of downstream ΔNp73 signaling pathways by rebastinib inhibits growth of established tumors and extends survival in preclinical models of glioblastoma.

CONCLUSION

Aberrant expression of ΔNp73 in GBM promotes tumor progression through autocrine and paracrine signaling dependent on Tie2 activation by ANGPT1. Disruption of this signaling by rebastinib improves tumor response to treatment in glioblastoma.

Angiopoietin-2 Combined with Radiochemotherapy Impedes Glioblastoma Recurrence by Acting in an Autocrine and Paracrine Manner: A Preclinical Study

Simple Summary

Glioblastoma (GB) is a highly aggressive brain tumor characterized by poor prognosis and high rate of recurrence in response to conventional treatments consisting of tumor resection and radiochemotherapy (RCT). The reasons for this therapeutic failure are mainly due to the complexity of GB biology and its environment. GB progression is highly dependent on its vascularization and inflammatory status. Besides, evidence showed that RCT also induces vascular change and inflammation. In GB patients, Angiopoietin-2 (Ang2), biomarker of poor prognosis is a crucial angiogenic factor also involved in inflammation. Our aim was to clarify the role of Ang2 in RCT-induced changes in the GB environment. To this end, we generated Ang2-overexpressing GL261 cells and characterized tumor progression, as well as inflammation and vascularization, in response to RCT. We showed that Ang2 delays tumor recurrence and makes a lasting improvement in animal survival when combined with conventional RCT.

Abstract

(1) We wanted to assess the impact of Ang2 in RCT-induced changes in the environment of glioblastoma. (2) The effect of Ang2 overexpression in tumor cells was studied in the GL261 syngeneic immunocompetent model of GB in response to fractionated RCT. (3) We showed that RCT combined with Ang2 led to tumor clearance for the GL261-Ang2 group by acting on the tumor cells as well as on both vascular and immune compartments. (4) In vitro, Ang2 overexpression in GL261 cells exposed to RCT promoted senescence and induced robust genomic instability, leading to mitotic death. (5) Coculture experiments of GL261-Ang2 cells with RAW 264.7 cells resulted in a significant increase in macrophage migration, which was abrogated by the addition of soluble Tie2 receptor. (6) Together, these preclinical results showed that, combined with RCT, Ang2 acted in an autocrine manner by increasing GB cell senescence and in a paracrine manner by acting on the innate immune system while modulating the vascular tumor compartment. On this preclinical model, we found that an ectopic expression of Ang2 combined with RCT impedes tumor recurrence.

The Tie2 signaling pathway in retinal vascular diseases: a novel therapeutic target in the eye

Background

Retinal vascular diseases such as neovascular age-related macular degeneration, diabetic retinopathy and/or diabetic macular edema, and retinal vein occlusion with macular edema—share several key pathophysiologic aspects including neovascularization, vascular permeability, and inflammation. The role of vascular endothelial growth factor (VEGF) in these processes, and the therapeutic benefits of VEGF inhibition, have been well characterized. Anti-VEGF therapy is highly effective for many patients but is not uniformly effective in all patients and imposes a significant treatment burden. More recently, the role of the Tie2 signaling pathway in the pathophysiology of retinal vascular diseases has been investigated, and the Tie2 pathway represents a novel therapeutic target for these conditions.

Areas covered

The index review describes the Tie2 pathway and its complementary role to the VEGF pathway in the angiogenesis cascade and will summarize studies of molecules in development to therapeutically modulate the Tie2 pathway in retinal vascular diseases.

Conclusions

Activation of the Tie2 pathway leads to downstream signaling that promotes vascular health and stability and decreases vascular permeability and inflammation. AXT107 is a collagen IV–derived synthetic peptide with a dual mechanism of action that involves suppression of VEGF signaling and activation of the Tie2 pathway; these actions are accomplished by AXT107 binding to and disrupting different integrin, leading to blockade of the VEGF receptor and rearrangement of cellular Tie2 rendering it susceptible to Ang2 agonism. Other Tie2 agonist compounds are also in development, including faricimab and razuprotafib. Tie2 activation only modestly impacts angiogenesis on its own but significantly potentiates VEGF suppression. Co-regulation of the VEGF and Tie2 signaling pathways has the potential to improve functional and structural outcomes in eyes with retinal vascular diseases.

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.

The Amino-Terminal Oligomerization Domain of Angiopoietin-2 Affects Vascular Remodeling, Mammary Gland Tumor Growth, and Lung Metastasis in Mice

Angiopoietin-2 (ANGPT2) is a context-dependent TIE2 agonistic or antagonistic ligand that induces diverse responses in cancer. Blocking ANGPT2 provides a promising strategy for inhibiting tumor growth and metastasis, yet variable effects of targeting ANGPT2 have complicated drug development. ANGPT2₄₄₃ is a naturally occurring, lower oligomeric protein isoform whose expression is increased in cancer. Here, we use a knock-in mouse line (mice expressing Angpt2₄₄₃), a genetic model for breast cancer and metastasis (MMTV-PyMT), a syngeneic melanoma lung colonization model (B16F10), and orthotopic injection of E0771 breast cancer cells to show that alternative forms increase the diversity of Angpt2 function. In a mouse retina model of angiogenesis, expression of Angpt2₄₄₃ caused impaired venous development, suggesting enhanced function as a competitive antagonist for Tie2. In mammary gland tumor models, Angpt2₄₄₃ differentially affected primary tumor growth and vascularization; these varying effects were associated with Angpt2 protein localization in the endothelium or in the stromal extracellular matrix as well as the frequency of Tie2-positive tumor blood vessels. In the presence of metastatic cells, Angpt2₄₄₃ promoted destabilization of pulmonary vasculature and lung metastasis. In vitro, ANGPT2₄₄₃ was susceptible to proteolytical cleavage, resulting in a monomeric ligand (ANGPT2_DAP) that inhibited ANGPT1- or ANGPT4-induced TIE2 activation but did not bind to alternative ANGPT2 receptor α5β1 integrin. Collectively, these data reveal novel roles for the ANGPT2 N-terminal domain in blood vessel remodeling, tumor growth, metastasis, integrin binding, and proteolytic regulation. SIGNIFICANCE: This study identifies the role of the N-terminal oligomerization domain of angiopoietin-2 in vascular remodeling and lung metastasis and provides new insights into mechanisms underlying the versatile functions of angiopoietin-2 in cancer.See related commentary by Kamiyama and Augustin, p. 35.

A Systems-Based Map of Human Brain Cell-Type Enriched Genes and Malignancy-Associated Endothelial Changes

Changes in the endothelium of the cerebral vasculature can contribute to inflammatory, thrombotic, and malignant disorders. The importance of defining cell-type-specific genes and their modification in disease is increasingly recognized. Here, we develop a bioinformatics-based approach to identify normal brain cell-enriched genes, using bulk RNA sequencing (RNA-seq) data from 238 normal human cortex samples from 2 independent cohorts. We compare endothelial cell-enriched gene profiles with astrocyte, oligodendrocyte, neuron, and microglial cell profiles. Endothelial changes in malignant disease are explored using RNA-seq data from 516 lower-grade gliomas and 401 glioblastomas. Lower-grade gliomas appear to be an "endothelial intermediate" between normal brain and glioblastoma. We apply our method for the prediction of glioblastoma-specific endothelial biomarkers, providing potential diagnostic or therapeutic targets. In summary, we provide a roadmap of endothelial cell identity in normal and malignant brain, using a method developed to resolve bulk RNA-seq into constituent cell-type-enriched profiles.

Resistance to Anti-angiogenic Therapies: A Mechanism Depending on the Time of Exposure to the Drugs

Angiogenesis, the formation of new blood vessels from preexisting one, represents a critical process for oxygen and nutrient supply to proliferating cells, therefore promoting tumor growth and metastasis. The Vascular Endothelial Growth Factor (VEGF) pathway is one of the key mediators of angiogenesis in cancer. Therefore, several therapies including monoclonal antibodies or tyrosine kinase inhibitors target this axis. Although preclinical studies demonstrated strong antitumor activity, clinical studies were disappointing. Antiangiogenic drugs, used to treat metastatic patients suffering of different types of cancers, prolonged survival to different extents but are not curative. In this review, we focused on different mechanisms involved in resistance to antiangiogenic therapies from early stage resistance involving mainly tumor cells to late stages related to the adaptation of the microenvironment.

Host-directed therapies targeting the tuberculosis granuloma stroma

Mycobacteria have co-evolved with their hosts resulting in pathogens adept at intracellular survival. Pathogenic mycobacteria actively manipulate infected macrophages to drive granuloma formation while subverting host cell processes to create a permissive niche. Granuloma residency confers phenotypic antimicrobial resistance by physically excluding or neutralising antibiotics. Host-directed therapies (HDTs) combat infection by restoring protective immunity and reducing immunopathology independent of pathogen antimicrobial resistance status. This review covers innovative research that has discovered ‘secondary’ symptoms of infection in the granuloma stroma are actually primary drivers of infection and that relieving these stromal pathologies with HDTs benefits the host. Advances in our understanding of the relationship between tuberculosis and the host vasculature, haemostatic system and extracellular matrix reorganisation are discussed. Preclinical and clinical use of HDTs against these stromal targets are summarised.

Receptor Tyrosine Kinases: Principles and Functions in Glioma Invasion

Protein tyrosine kinases are enzymes that are capable of adding a phosphate group to specific tyrosines on target proteins. A receptor tyrosine kinase (RTK) is a tyrosine kinase located at the cellular membrane and is activated by binding of a ligand via its extracellular domain. Protein phosphorylation by kinases is an important mechanism for communicating signals within a cell and regulating cellular activity; furthermore, this mechanism functions as an "on" or "off" switch in many cellular functions. Ninety unique tyrosine kinase genes, including 58 RTKs, were identified in the human genome; the products of these genes regulate cellular proliferation, survival, differentiation, function, and motility. Tyrosine kinases play a critical role in the development and progression of many types of cancer, in addition to their roles as key regulators of normal cellular processes. Recent studies have revealed that RTKs such as epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), c-Met, Tie, Axl, discoidin domain receptor 1 (DDR1), and erythropoietin-producing human hepatocellular carcinoma (Eph) play a major role in glioma invasion. Herein, we summarize recent advances in understanding the role of RTKs in glioma pathobiology, especially the invasive phenotype, and present the perspective that RTKs are a potential target of glioma therapy.

Newly Identified Peptide, Peptide Lv, Promotes Pathological Angiogenesis

Background We recently discovered a small endogenous peptide, peptide Lv, with the ability to activate vascular endothelial growth factor receptor 2 and its downstream signaling. As vascular endothelial growth factor through vascular endothelial growth factor receptor 2 contributes to normal development, vasodilation, angiogenesis, and pathogenesis of various diseases, we investigated the role of peptide Lv in vasodilation and developmental and pathological angiogenesis in this study. Methods and Results The endothelial cell proliferation, migration, and 3-dimensional sprouting assays were used to test the abilities of peptide Lv in angiogenesis in vitro. The chick chorioallantoic membranes and early postnatal mice were used to examine its impact on developmental angiogenesis. The oxygen-induced retinopathy and laser-induced choroidal neovascularization mouse models were used for in vivo pathological angiogenesis. The isolated porcine retinal and coronary arterioles were used for vasodilation assays. Peptide Lv elicited angiogenesis in vitro and in vivo. Peptide Lv and vascular endothelial growth factor acted synergistically in promoting endothelial cell proliferation. Peptide Lv-elicited vasodilation was not completely dependent on nitric oxide, indicating that peptide Lv had vascular endothelial growth factor receptor 2/nitric oxide-independent targets. An antibody against peptide Lv, anti-Lv, dampened vascular endothelial growth factor-elicited endothelial proliferation and laser-induced vascular leakage and choroidal neovascularization. While the pathological angiogenesis in mouse eyes with oxygen-induced retinopathy was enhanced by exogenous peptide Lv, anti-Lv dampened this process. Furthermore, deletion of peptide Lv in mice significantly decreased pathological neovascularization compared with their wild-type littermates. Conclusions These results demonstrate that peptide Lv plays a significant role in pathological angiogenesis but may be less critical during development. Peptide Lv is involved in pathological angiogenesis through vascular endothelial growth factor receptor 2-dependent and -independent pathways. As anti-Lv dampened the pathological angiogenesis in the eye, anti-Lv may have a therapeutic potential to treat pathological angiogenesis.

Changing paradigms for targeted therapies against diffuse infiltrative gliomas: tackling a moving target

Introduction: Gliomas are highly heterogeneous primary brain tumors which result in a disproportionately high degree of morbidity and mortality despite their locoregional occurrence. Advances in the understanding of the biological makeup of these malignancies have yielded a number of potential tumor-driving pathways which have been identified as rational targets for therapy. However, early trials of agents that target these pathways have uniformly failed to yield improvement in outcomes in patients with malignant gliomas. Areas covered: This review provides an overview of the most common biological features of gliomas and the strategies to target the same; in addition, the current status of immunotherapy and biological therapies are outlined and the future directions to tackle the challenges of therapy for gliomas are examined. Expert opinion: The limitations of current treatments are attributed to the inability of most of these agents to cross the blood-brain barrier and to the intrinsic heterogeneity of the tumors that result in treatment resistance. The recent emergence of immune-mediated and biological therapies and of agents that target metabolic pathways in gliomas have provided strategies that may overcome tumor heterogeneity and ongoing trials of such agents are anticipated to yield improved outcomes.

Vascular leakage caused by loss of Akt1 is associated with impaired mural cell coverage

Angiogenesis plays a critical role in embryo development, tissue repair, tumor growth and wound healing. In the present study, we investigated the role of the serine/threonine kinase Akt in angiogenesis. Silencing of Akt1 in human umbilical vein endothelial cells significantly inhibited vascular endothelial growth factor (VEGF)-induced capillary-like tube formation. Mice lacking Akt1 exhibited impaired retinal angiogenesis with delayed endothelial cell (EC) proliferation. In addition, VEGF-induced corneal angiogenesis and tumor development were significantly inhibited in mice lacking Akt1. Loss of Akt1 resulted in reduced angiogenic sprouting, as well as the proliferation of ECs and mural cells. Addition of culture supernatant of vascular smooth muscle cells (VSMCs) in which Akt1 was silenced suppressed tube formation, the stability of preformed tubes and the proliferation of ECs. In addition, attachment of VSMCs to ECs was significantly reduced in cells in which Akt1 was silenced. Mural cell coverage of retinal vasculature was reduced in mice lacking Akt1. Finally, mice lacking Akt1 showed severe retinal hemorrhage compared to the wild-type. These results suggest that the regulation of EC function and mural cell coverage by Akt1 is important for blood vessel maturation during angiogenesis.

Differential Effects of Ang-2/VEGF-A Inhibiting Antibodies in Combination with Radio- or Chemotherapy in Glioma

Antiangiogenic strategies have not shown striking antitumor activities in the majority of glioma patients so far. It is unclear which antiangiogenic combination regimen with standard therapy is most effective. Therefore, we compared anti-VEGF-A, anti-Ang2, and bispecific anti-Ang-2/VEGF-A antibody treatments, alone and in combination with radio- or temozolomide (TMZ) chemotherapy, in a malignant glioma model using multiparameter two-photon in vivo microscopy in mice. We demonstrate that anti-Ang-2/VEGF-A lead to the strongest vascular changes, including vascular normalization, both as monotherapy and when combined with chemotherapy. The latter was accompanied by the most effective chemotherapy-induced death of cancer cells and diminished tumor growth. This was most probably due to a better tumor distribution of the drug, decreased tumor cell motility, and decreased formation of resistance-associated tumor microtubes. Remarkably, all these parameters where reverted when radiotherapy was chosen as combination partner for anti-Ang-2/VEGF-A. In contrast, the best combination partner for radiotherapy was anti-VEGF-A. In conclusion, while TMZ chemotherapy benefits most from combination with anti-Ang-2/VEGF-A, radiotherapy does from anti-VEGF-A. The findings imply that uninformed combination regimens of antiangiogenic and cytotoxic therapies should be avoided.

Anti-angiogenic Targets: Angiopoietin and Angiopoietin Receptors

Tumor blood vessel formation (angiogenesis) is essential for tumor growth and metastasis. Two main endothelial ligand–receptor pathways regulating angiogenesis are vascular endothelial growth factor (VEGF) receptor and angiopoietin-TIE receptor pathways. The angiopoietin-TIE pathway is required for the remodeling and maturation of the blood and lymphatic vessels during embryonic development after VEGF and VEGF-C mediated development of the primary vascular plexus. Angiopoietin-1 (ANGPT1) stabilizes the vasculature after angiogenic processes, via tyrosine kinase with immunoglobulin-like and EGF-like domains 2 (TIE2) activation. In contrast, ANGPT2 is upregulated at sites of vascular remodeling. ANGPT2 is secreted by activated endothelial cells in inflammation, promoting vascular destabilization. ANGPT2 has been found to be expressed in many human cancers. Intriguingly, in preclinical models inhibition of ANGPT2 has provided promising results in preventing tumor angiogenesis, tumor growth, and metastasis, making it an attractive candidate to target in tumors. However, until now the first ANGPT2 targeting therapies have been less effective in clinical trials than in experimental models. Additionally, in preclinical models combined therapy against ANGPT2 and VEGF or immune checkpoint inhibitors has been superior to monotherapies, and these pathways are also targeted in early clinical trials. In order to improve current anti-angiogenic therapies and successfully exploit ANGPT2 as a target for cancer treatment, the biology of the angiopoietin-TIE pathway needs to be profoundly clarified.

Vasculogenesis and angiogenesis initiation under normoxic conditions through Wnt/β-catenin pathway in gliomas

The canonical Wnt/β-catenin pathway is up-regulated in gliomas and involved in proliferation, invasion, apoptosis, vasculogenesis and angiogenesis. Nuclear β-catenin accumulation correlates with malignancy. Hypoxia activates hypoxia-inducible factor (HIF)-1α by inhibiting HIF-1α prolyl hydroxylation, which promotes glycolytic energy metabolism, vasculogenesis and angiogenesis, whereas HIF-1α is degraded by the HIF prolyl hydroxylase under normoxic conditions. We focus this review on the links between the activated Wnt/β-catenin pathway and the mechanisms underlying vasculogenesis and angiogenesis through HIF-1α under normoxic conditions in gliomas. Wnt-induced epidermal growth factor receptor/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, Wnt-induced signal transducers and activators of transcription 3 (STAT3) signaling, and Wnt/β-catenin target gene transduction (c-Myc) can activate HIF-1α in a hypoxia-independent manner. The PI3K/Akt/mammalian target of rapamycin pathway activates HIF-1α through eukaryotic translation initiation factor 4E-binding protein 1 and STAT3. The β-catenin/T-cell factor 4 complex directly binds to STAT3 and activates HIF-1α, which up-regulates the Wnt/β-catenin target genes cyclin D1 and c-Myc in a positive feedback loop. Phosphorylated STAT3 by interleukin-6 or leukemia inhibitory factor activates HIF-1α even under normoxic conditions. The activation of the Wnt/β-catenin pathway induces, via the Wnt target genes c-Myc and cyclin D1 or via HIF-1α, gene transactivation encoding aerobic glycolysis enzymes, such as glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production, as the primary alternative of ATP, at all oxygen levels, even in normoxic conditions. Lactate released by glioma cells via the monocarboxylate lactate transporter-1 up-regulated by HIF-1α and lactate anion activates HIF-1α in normoxic endothelial cells by inhibiting HIF-1α prolyl hydroxylation and preventing HIF labeling by the von Hippel-Lindau protein. Increased lactate with acid environment and HIF-1α overexpression induce the vascular endothelial growth factor (VEGF) pathway of vasculogenesis and angiogenesis under normoxic conditions. Hypoxia and acidic pH have no synergistic effect on VEGF transcription.

Evidence for critical role of Tie2/Ang1 interaction in metastatic oral cancer

Angiopoietin-1 (Ang1) is a binding partner of endothelial cell-specific tyrosine-protein kinase receptor (Tie2), which serves important roles in vascular development and angiogenesis. Tie2 is closely associated with the metastasis of oral squamous cell carcinomas (OSCCs) however, little is known about the correlation between Tie2 and Ang1. In the present study, the functional mechanisms of the Tie2/Ang1 interaction were investigated using Tie2 overexpressed (oeTie2) OSCC cells and recombinant Ang1 protein. oeTie2 cells had increased cell-cell and cell-extracellular matrix adhesions compared with the control cells. Additionally, the adhesive activities increased following treatment with exogenous Ang1, indicating that Ang1 directly enhances Tie2 functions. In the clinical OSCC data from 10 cases positive for regional lymph node metastasis, all cases were negative for Tie2 expression and eight cases (80%) were negative for Ang1 expression. These results suggest that Tie2 and Ang1 serve important roles in cancer metastasis and may be potential biomarkers and therapeutic targets for OSCC metastasis.

Angiopoietins as biomarkers of disease severity and bacterial burden in pulmonary tuberculosis

BACKGROUND

Circulating angiogenic factors of the vascular endothelial growth factor family are important biomarkers of disease severity in pulmonary tuberculosis (PTB). However, the role of angiopoietins, which are also involved in angiogenesis, in PTB is not known.

OBJECTIVE AND DESIGN

To examine the association of circulating angiopoietins with TB disease or latent tuberculous infection (LTBI), we examined the systemic levels of angiopoietin (Ang) 1, Ang 2 and Tie-2 receptor in individuals with PTB (n = 44), LTBI (n = 44) or no tuberculous infection (NTBI) (n = 44).

RESULTS

Circulating levels of Ang-1, Ang-2 and Tie-2 were significantly higher in PTB than in individuals with LTBI or NTBI. Moreover, Ang-1, Ang-2 and Tie-2 levels were significantly higher in PTB with bilateral disease. The levels of these factors also exhibited a significant positive relationship with bacterial burdens in PTB. Receiver operating characteristics curve analysis revealed Ang-2 as a marker distinguishing PTB from LTBI or NTBI. Finally, the circulating levels of Ang-1, Ang-2 and Tie-2 were significantly reduced following anti-tuberculosis chemotherapy.

CONCLUSIONS

Our data demonstrate that PTB is associated with elevated levels of circulating angiopoietins, possibly reflecting endothelial dysfunction. In addition, Ang-2 could prove useful as a biomarker to monitor disease severity, bacterial burden and therapeutic responses.

Functional morphology of the blood-brain barrier in health and disease

The adult quiescent blood–brain barrier (BBB), a structure organised by endothelial cells through interactions with pericytes, astrocytes, neurons and microglia in the neurovascular unit, is highly regulated but fragile at the same time. In the past decade, there has been considerable progress in understanding not only the molecular pathways involved in BBB development, but also BBB breakdown in neurological diseases. Specifically, the Wnt/β-catenin, retinoic acid and sonic hedgehog pathways moved into the focus of BBB research. Moreover, angiopoietin/Tie2 signalling that is linked to angiogenic processes has gained attention in the BBB field. Blood vessels play an essential role in initiation and progression of many diseases, including inflammation outside the central nervous system (CNS). Therefore, the potential influence of CNS blood vessels in neurological diseases associated with BBB alterations or neuroinflammation has become a major focus of current research to understand their contribution to pathogenesis. Moreover, the BBB remains a major obstacle to pharmaceutical intervention in the CNS. The complications may either be expressed by inadequate therapeutic delivery like in brain tumours, or by poor delivery of the drug across the BBB and ineffective bioavailability. In this review, we initially describe the cellular and molecular components that contribute to the steady state of the healthy BBB. We then discuss BBB alterations in ischaemic stroke, primary and metastatic brain tumour, chronic inflammation and Alzheimer’s disease. Throughout the review, we highlight common mechanisms of BBB abnormalities among these diseases, in particular the contribution of neuroinflammation to BBB dysfunction and disease progression, and emphasise unique aspects of BBB alteration in certain diseases such as brain tumours. Moreover, this review highlights novel strategies to monitor BBB function by non-invasive imaging techniques focussing on ischaemic stroke, as well as novel ways to modulate BBB permeability and function to promote treatment of brain tumours, inflammation and Alzheimer’s disease. In conclusion, a deep understanding of signals that maintain the healthy BBB and promote fluctuations in BBB permeability in disease states will be key to elucidate disease mechanisms and to identify potential targets for diagnostics and therapeutic modulation of the BBB.

Nanofibrous Electrospun Heart Decellularized Extracellular Matrix-Based Hybrid Scaffold as Wound Dressing for Reducing Scarring in Wound Healing

Produced through electrospinning, poly(l-lactide-co-caprolactone) (PLCL) membranes, which have a porous structure and are biodegradable, are of interest in various medical fields. The porous-structured electrospun membrane is particularly interesting because of several favorable properties as follows: it exudes fluid from the wound, does not build up under the wound covering, and does not cause wound desiccation. Moreover, extracellular matrix (ECM)-based structures derived by tissue decellularization have application as engineered tissue scaffolds and as supports for cellular regeneration. In particular, heart decellularized ECM (hdECM) has various pro-angiogenic factors that can induce angiogenesis for wound healing. In this regard, a nanofibrous electrospun hdECM-based hybrid scaffold (NEhdHS), which is a PLCL membrane, including hdECM as an active agent, was tested as a wound dressing to assess its fundamental biochemical and physical features in wound healing. Use of NEhdHS with its porous structure and pro-angiogenic factors is expected to provide an effective wound dressing and reduced scarring. We first demonstrate the effectiveness of a proposed decellularization protocol through analysis of dECM components and describe the mechanical properties of the fabricated NEhdHS. Next, we present an in vitro angiogenesis analysis of the NEhdHS, using a coculture system with human dermal fibroblasts and human umbilical vein endothelial cells; the results of which confirm its biocompatibility and show that the NEhdHS can significantly enhance angiogenesis over that obtained from PLCL or gelatin-containing PLCL scaffolds. We also studied the effectiveness of the NEhdHS in vivo. Using a rat excisional wound-splinting model, we show that covering the upper part of the wound with NEhdHS significantly reduces scarring in the wound healing process compared to that with PLCL or gelatin-containing PLCL scaffolds. Based upon its properties, we conclude that the NEhdHS has potential for application in wound dressing.

Phase 2 and biomarker study of trebananib, an angiopoietin-blocking peptibody, with and without bevacizumab for patients with recurrent glioblastoma

BACKGROUND

Angiopoietins contribute to tumor angiogenesis and may be upregulated as a compensatory factor after vascular endothelial growth factor (VEGF) blockade. The authors performed a phase 2 and biomarker study to evaluate trebananib, an angiopoietin 1 and angiopoietin 2 blocking peptibody, with and without bevacizumab in patients with recurrent glioblastoma.

METHODS

Forty-eight patients who had bevacizumab-naive, recurrent glioblastoma were treated with trebananib (30 mg/kg weekly) as single agent (n = 11) or combined with bevacizumab (n = 37). The primary endpoint was 6-month progression-free survival rate as determined by investigator review. Circulating biomarker levels were assessed before and after study therapy.

RESULTS

Trebananib was well tolerated as monotherapy and did not enhance bevacizumab-associated toxicity. Trebananib had no single-agent activity, and all treated patients exhibited progressive disease within 2 months. The 6-month progression-free survival rate for trebananib plus bevacizumab was 24.3% (95% confidence interval [CI], 12.1%-38.8%); whereas the median overall survival was 9.5 months (95% CI, 7.5-4.7 months), and the 12-month overall survival rate was 37.8% (95% CI, 22.6%-53.0%). Baseline and post-treatment changes in circulating vascular VEGF and interleukin-8 levels were correlated with survival among patients who received trebananib plus bevacizumab.

CONCLUSIONS

Angiopoietin 1 and angiopoietin 2 inhibition with trebananib was ineffective as monotherapy and did not enhance the ability of VEGF blockade with bevacizumab to improve the outcomes of patients with recurrent glioblastoma. Cancer 2018;124:1438-48. © 2017 American Cancer Society.

Cholera Toxin Subunit B Enabled Multifunctional Glioma-Targeted Drug Delivery

Glioma is among the most formidable brain cancers due to location in the brain. Cholera toxin subunit B (CTB) is investigated to facilitate multifunctional glioma-targeted drug delivery by targeting the glycosphingolipid GM1 expressed in the blood-brain barrier (BBB), neovasulature, and glioma cells. When modified on the surface of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (CTB-NPs), CTB fully retains its bioactivity after 24 h incubation in the fresh mouse plasma. The formed protein corona (PC) of CTB-NP and plain PLGA nanoparticles (NP) after incubation in plasma is analyzed using liquid chromatography tandem massspectrometry (nano-LC-MS/MS). CTB modification does not alter the protein components of the formed PC, macrophage phagocytosis, or pharmacokinetic profiles. CTB-NP can efficiently penetrate the in vitro BBB model and target glioma cells and human umbilical vascular endothelial cells. Paclitaxel is loaded in NP (NP/PTX) and CTB-NP (CTB-NP/PTX), and their antiglioma effects are assessed in nude mice bearing intracranial glioma. CTB-NP/PTX can efficiently induce apoptosis of intracranial glioma cells and ablate neovasulature in vivo, resulting in significant prolongation of survival of nude mice bearing intracranial glioma (34 d) in comparison to those treated with NP/PTX (29 d), Taxol (24 d), and saline (21 d). The present study suggests a potential multifunctional glioma-targeted drug delivery system enabled by cholera toxin subunit B.

c-kit Positive Cardiac Outgrowth Cells Demonstrate Better Ability for Cardiac Recovery Against Ischemic Myopathy

Objective

Resident cardiac stem cells are expected to be a therapeutic option for patients who suffer from severe heart failure. However, uncertainty remains over whether sorting cells for c-kit, a stem cell marker, improves therapeutic outcomes.

Materials and methods

Cardiac outgrowth cells cultured from explants of rat heart atrium were sorted according to their positivity (+) or negativity (−) for c-kit. These cells were exposed to hypoxia for 3 d, and subsequently harvested for mRNA expression measurement. The cell medium was also collected to assess cytokine secretion. To test for a functional benefit in animals, myocardial infarction (MI) was induced in rats, and c-kit+ or c-kit− cells were injected. The left ventricular ejection fraction (LVEF) was measured for up to 4 weeks, after which the heart was harvested for biological and histological analyses.

Results and conclusion

Expression of the angiogenesis-related genes, VEGF and ANGPTL2, was significantly higher in c-kit+ cells after 3 d of hypoxic culture, although we found no such difference prior to hypoxia. Secretion of VEGF and ANGPTL2 was greater in the c-kit+ group than in the c-kit− group, while hypoxia tended to increase cytokine expression in both groups. In addition, IGF-1 was significantly increased in the c-kit+ group, consistent with the relatively low expression of cleaved-caspase 3 revealed by western blot assay, and the relatively low count of apoptotic cells revealed by histochemical analysis. Administration of c-kit+cells into the MI heart improved the LVEF and increased neovascularization. These results indicate that c-kit+cells may be useful in cardiac stem cell therapy.

Role of NOD- like Receptors in Glioma Angiogenesis: Insights into future therapeutic interventions

Gliomas are the most common solid tumors among central nervous system tumors. Most glioma patients succumb to their disease within two years of the initial diagnosis. The median survival of gliomas is only 14.6 months, even after aggressive therapy with surgery, radiation, and chemotherapy. Gliomas are heavily infiltrated with myeloid- derived cells and endothelial cells. Increasing evidence suggests that these myeloid- derived cells interact with tumor cells promoting their growth and migration. NLRs (nucleotide-binding oligomerization domain (NOD)-containing protein like receptors) are a class of pattern recognition receptors that are critical to sensing pathogen and danger associated molecular patterns. Mutations in some NLRs lead to autoinflammatory diseases in humans. Moreover, dysregulated NLR signaling is central to the pathogenesis of several cancers, autoimmune and neurodegenerative diseases. Our review explores the role of angiogenic factors that contribute to upstream or downstream signaling pathways leading to NLRs. Angiogenesis plays a significant role in the pathogenesis of variety of tumors including gliomas. Though NLRs have been detected in several cancers including gliomas and NLR signaling contributes to angiogenesis, the exact role and mechanism of involvement of NLRs in glioma angiogenesis remain largely unexplored. We discuss cellular, molecular and genetic studies of NLR signaling and convergence of NLR signaling pathways with angiogenesis signaling in gliomas. This may lead to re-appropriation of existing anti-angiogenic therapies or development of future strategies for targeted therapeutics in gliomas.

The Role of Vascular Endothelial Growth Factor in Small-airway Remodelling in a Rat Model of Chronic Obstructive Pulmonary Disease

Small-airway remodelling is one of the most remarkable pathological features of chronic obstructive pulmonary disease (COPD), in which angiogenesis plays a critical role that contributes to disease progression. The endothelial cell-specific mitogen vascular endothelial growth factor (VEGF), as well as its receptors, VEGFR1, VEGFR2, are thought to be the major mediators of pathological angiogenesis, and sunitinib exhibits anti-angiogenesis property through VEGF blockage and has been widely used to treat various cancers. In our study, Sprague-Dawley rats were subjected to lipopolysaccharide (LPS) injection and cigarette smoke (CS) inhalation to induce COPD, following sunitinib administration was conducted. Haematoxylin-eosin, Masson staining and immunostaining analysis were used to evaluate the pathological changes; quantitative real-time PCR and enzyme-linked immunosorbent assay were performed to provide more compelling data on the function of VEGF, VEGFR1, VEGFR2 in angiogenesis. Sunitinib treatment was associated with less angiogenesis in small-airway remodelling with a slightly disordered lung architecture, and lower expression level of VEGF, VEGFR1, VEGFR2. Overall, our results indicate that VEGF is a vital important factor that contributes to the small-airway remodelling in a rat model of COPD through promoting angiogenesis, which mainly depend on the specific binding between VEGF and VEGFR1 and can be effectively attenuated by sunitinib.

Novel TIE-2 inhibitor BAY-826 displays in vivo efficacy in experimental syngeneic murine glioma models

Targeting the vascular endothelial growth factor signaling axis in glioblastoma inevitably leads to tumor recurrence and a more aggressive phenotype. Therefore, other angiogenic pathways, like the angiopoietin/tunica interna endothelial cell kinase (TIE) signaling axis, have become additional targets for therapeutic intervention. Here, we explored whether targeting the receptor tyrosine kinase TIE-2 using a novel, highly potent, orally available small molecule TIE-2 inhibitor (BAY-826) improves tumor control in syngeneic mouse glioma models. BAY-826 inhibits TIE-2 phosphorylation in vitro and in vivo as demonstrated by suppression of Angiopoietin-1- or Na₃ VO₄ -induced TIE-2 phosphorylation in glioma cells or extracts of lungs from BAY-826-treated mice. There was a trend toward prolonged survival upon single-agent treatment in two of four models (SMA-497 and SMA-540) and there was a significant survival benefit in one model (SMA-560). Co-treatment with BAY-826 and irradiation was ineffective in one model (SMA-497), but provided synergistic prolongation of survival in another (SMA-560). Decreased vessel densities and increased leukocyte infiltration were observed, but might be independent processes as the effect was also observed in single treatment modalities. These data demonstrate that TIE-2 inhibition may improve tumor response to treatment in highly vascularized tumors such as glioblastoma.

miR-218 suppresses gastric cancer cell proliferation and invasion via regulation of angiopoietin-2

Novel targeted therapies need to be developed for gastric cancer, the third most common cancer type and the second most common cause of cancer-related mortality in China. Previous studies indicate that angiopoietin (Ang)-2 serves a role in the proliferation, migration, invasion and adhesion of malignant cells. The present study identified, using functional studies, that exogenous expression of miR-218 increased migration of NCI-87 and HGC-27 gastric cancer cells, which coincided with a reduction in the expression of Ang-2. In addition, intratumoral delivery of miR-218 inhibited proliferation and angiogenesis of gastric cancer cells in vivo, with a corresponding decreased in Ang-2 expression. These results indicate that miR-218 serves an important role in gastric cancer tumorigenesis through regulating the expression of Ang-2. Therefore, components of miR-218/Ang-2 signaling could provide novel therapeutic targets for the treatment of gastric cancer.

Contribution of pericyte paracrine regulation of the endothelium to angiogenesis

During physiological development and after a stressor event, vascular cells communicate with each other to evoke new vessel formation-a process known as angiogenesis. This communication occurs via direct contact and via paracrine release of proteins and nucleic acids, both in a free form or encapsulated into micro-vesicles. In diseases with an altered angiogenic response, such as cancer and diabetic vascular complications, it becomes of paramount importance to tune the cell communication process. Endothelial cell growth and migration are essential processes for new vessel formation, and pericytes, together with some classes of circulating monocytes, are important endothelial regulators. The interaction between pericytes and the endothelium is facilitated by their anatomical apposition, which involves endothelial cells and pericytes sharing the same basement membrane. However, the role of pericytes is not fully understood. The characteristics and the function of tissue-specific pericytesis are the focus of this review. Factors involved in the cross-talk between these cell types and the opportunities afforded by micro-RNA and micro-vesicle techniques are discussed. Targeting these mechanisms in pathological conditions, in which the vessel response is altered, is considered in relation to identification of new therapies for restoring the blood flow.