Impaired tumor growth and angiogenesis in mice heterozygous for Vegfr2 (Flk1)

The evolving tumor microenvironment: From cancer initiation to metastatic outgrowth

Cancers represent complex ecosystems comprising tumor cells and a multitude of non-cancerous cells, embedded in an altered extracellular matrix. The tumor microenvironment (TME) includes diverse immune cell types, cancer-associated fibroblasts, endothelial cells, pericytes, and various additional tissue-resident cell types. These host cells were once considered bystanders of tumorigenesis but are now known to play critical roles in the pathogenesis of cancer. The cellular composition and functional state of the TME can differ extensively depending on the organ in which the tumor arises, the intrinsic features of cancer cells, the tumor stage, and patient characteristics. Here, we review the importance of the TME in each stage of cancer progression, from tumor initiation, progression, invasion, and intravasation to metastatic dissemination and outgrowth. Understanding the complex interplay between tumor cell-intrinsic, cell-extrinsic, and systemic mediators of disease progression is critical for the rational development of effective anti-cancer treatments.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

An overview on display systems (phage, bacterial, and yeast display) for production of anticancer antibodies; advantages and disadvantages

Antibodies as ideal therapeutic and diagnostic molecules are among the top-selling drugs providing considerable efficacy in disease treatment, especially in cancer therapy. Limitations of the hybridoma technology as routine antibody generation method in conjunction with numerous developments in molecular biology led to the development of alternative approaches for the streamlined identification of most effective antibodies. In this regard, display selection technologies such as phage display, bacterial display, and yeast display have been widely promoted over the past three decades as ideal alternatives to traditional methods. The display of antibodies on phages is probably the most widespread of these methods, although surface display on bacteria or yeast have been employed successfully, as well. These methods using various sizes of combinatorial antibody libraries and different selection strategies possessing benefits in screening potency, generating, and isolation of high affinity antibodies with low risk of immunogenicity. Knowing the basics of each method assists in the design and retrieval process of antibodies suitable for different diseases, including cancer. In this review, we aim to outline the basics of each library construction and its display method, screening and selection steps. The advantages and disadvantages in comparison to alternative methods, and their applications in antibody engineering will be explained. Finally, we will review approved or non-approved therapeutic antibodies developed by employing these methods, which may serve as therapeutic antibodies in cancer therapy.

Novel treatment strategy for NRAS-mutated melanoma through a selective inhibitor of CD147/VEGFR-2 interaction

More than 70% of human NRAS^mut melanomas are resistant to MEK inhibitors highlighting the crucial need for efficient therapeutic strategies for these tumors. CD147, a membrane receptor, is overexpressed in most cancers including melanoma and is associated with poor prognosis. We show here that CD147i, a specific inhibitor of CD147/VEGFR-2 interaction represents a potential therapeutic strategy for NRAS^mut melanoma cells. It significantly inhibited the malignant properties of NRAS^mut melanomas ex vivo and in vivo. Importantly, NRAS^mut patient's-derived xenografts, which were resistant to MEKi, became sensitive when combined with CD147i leading to decreased proliferation ex vivo and tumor regression in vivo. Mechanistic studies revealed that CD147i effects were mediated through STAT3 pathway. These data bring a proof of concept on the impact of the inhibition of CD147/VEGFR-2 interaction on melanoma progression and represents a new therapeutic opportunity for NRAS^mut melanoma when combined with MEKi.

Mechanoregulation of Vascular Endothelial Growth Factor Receptor 2 in Angiogenesis

The endothelial cells that compose the vascular system in the body display a wide range of mechanotransductive behaviors and responses to biomechanical stimuli, which act in concert to control overall blood vessel structure and function. Such mechanosensitive activities allow blood vessels to constrict, dilate, grow, or remodel as needed during development as well as normal physiological functions, and the same processes can be dysregulated in various disease states. Mechanotransduction represents cellular responses to mechanical forces, translating such factors into chemical or electrical signals which alter the activation of various cell signaling pathways. Understanding how biomechanical forces drive vascular growth in healthy and diseased tissues could create new therapeutic strategies that would either enhance or halt these processes to assist with treatments of different diseases. In the cardiovascular system, new blood vessel formation from preexisting vasculature, in a process known as angiogenesis, is driven by vascular endothelial growth factor (VEGF) binding to VEGF receptor 2 (VEGFR-2) which promotes blood vessel development. However, physical forces such as shear stress, matrix stiffness, and interstitial flow are also major drivers and effectors of angiogenesis, and new research suggests that mechanical forces may regulate VEGFR-2 phosphorylation. In fact, VEGFR-2 activation has been linked to known mechanobiological agents including ERK/MAPK, c-Src, Rho/ROCK, and YAP/TAZ. In vascular disease states, endothelial cells can be subjected to altered mechanical stimuli which affect the pathways that control angiogenesis. Both normalizing and arresting angiogenesis associated with tumor growth have been strategies for anti-cancer treatments. In the field of regenerative medicine, harnessing biomechanical regulation of angiogenesis could enhance vascularization strategies for treating a variety of cardiovascular diseases, including ischemia or permit development of novel tissue engineering scaffolds. This review will focus on the impact of VEGFR-2 mechanosignaling in endothelial cells (ECs) and its interaction with other mechanotransductive pathways, as well as presenting a discussion on the relationship between VEGFR-2 activation and biomechanical forces in the extracellular matrix (ECM) that can help treat diseases with dysfunctional vascular growth.

KIF13B-mediated VEGFR2 trafficking is essential for vascular leakage and metastasis in vivo

VEGF-A induces vascular leakage and angiogenesis via activating the cell surface localized receptor VEGF receptor 2 (VEGFR2). The amount of available VEGFR2 at the cell surface is however tightly regulated by trafficking of VEGFR2 by kinesin family 13 B (KIF13B), a plus-end kinesin motor, to the plasma membrane of endothelial cells (ECs). Competitive inhibition of interaction between VEGFR2 and KIF13B by a peptide kinesin-derived angiogenesis inhibitor (KAI) prevented pathological angiogenesis in models of cancer and eye disease associated with defective angiogenesis. Here, we show the protective effects of KAI in VEGF-A-induced vascular leakage and cancer metastasis. Using an EC-specific KIF13B knockout (Kif13b iECKO ) mouse model, we demonstrated the function of EC expressed KIF13B in mediating VEGF-A-induced vascular leakage, angiogenesis, tumor growth, and cancer metastasis. Thus, KIF13B-mediated trafficking of VEGFR2 to the endothelial surface has an essential role in pathological angiogenesis induced by VEGF-A, and is therefore a potential therapeutic target.

Endothelial FGF signaling is protective in hypoxia-induced pulmonary hypertension

Hypoxia-induced pulmonary hypertension (PH) is one of the most common and deadliest forms of PH. Fibroblast growth factor receptors 1 and 2 (FGFR1/2) are elevated in patients with PH and in mice exposed to chronic hypoxia. Endothelial FGFR1/2 signaling is important for the adaptive response to several injury types and we hypothesized that endothelial FGFR1/2 signaling would protect against hypoxia-induced PH. Mice lacking endothelial FGFR1/2, mice with activated endothelial FGFR signaling, and human pulmonary artery endothelial cells (HPAECs) were challenged with hypoxia. We assessed the effect of FGFR activation and inhibition on right ventricular pressure, vascular remodeling, and endothelial-mesenchymal transition (EndMT), a known pathologic change seen in patients with PH. Hypoxia-exposed mice lacking endothelial FGFRs developed increased PH, while mice overexpressing a constitutively active FGFR in endothelial cells did not develop PH. Mechanistically, lack of endothelial FGFRs or inhibition of FGFRs in HPAECs led to increased TGF-β signaling and increased EndMT in response to hypoxia. These phenotypes were reversed in mice with activated endothelial FGFR signaling, suggesting that FGFR signaling inhibits TGF-β pathway-mediated EndMT during chronic hypoxia. Consistent with these observations, lung tissue from patients with PH showed activation of FGFR and TGF-β signaling. Collectively, these data suggest that activation of endothelial FGFR signaling could be therapeutic for hypoxia-induced PH.

The versican-hyaluronan complex provides an essential extracellular matrix niche for Flk1+ hematoendothelial progenitors

Little is known about extracellular matrix (ECM) contributions to formation of the earliest cell lineages in the embryo. Here, we show that the proteoglycan versican and glycosaminoglycan hyaluronan are associated with emerging Flk1⁺ hematoendothelial progenitors at gastrulation. The mouse versican mutant Vcan^hdf lacks yolk sac vasculature, with attenuated yolk sac hematopoiesis. CRISPR/Cas9-mediated Vcan inactivation in mouse embryonic stem cells reduced vascular endothelial and hematopoietic differentiation within embryoid bodies, which generated fewer blood colonies, and had an impaired angiogenic response to VEGF₁₆₅. Hyaluronan was severely depleted in Vcan^hdf embryos, with corresponding upregulation of the hyaluronan-depolymerase TMEM2. Conversely, hyaluronan-deficient mouse embryos also had vasculogenic suppression but with increased versican proteolysis. VEGF₁₆₅ and Indian hedgehog, crucial vasculogenic factors, utilized the versican-hyaluronan matrix, specifically versican chondroitin sulfate chains, for binding. Versican-hyaluronan ECM is thus an obligate requirement for vasculogenesis and primitive hematopoiesis, providing a vasculogenic factor-enriching microniche for Flk1⁺ progenitors from their origin at gastrulation.

ANKFY1 is essential for retinal endothelial cell proliferation and migration via VEGFR2/Akt/eNOS pathway

Dysregulation of endothelial cell proliferation and migration are hallmarks of angiogenic diseases. Among them, excessive ocular angiogenesis is a major cause of blindness. Vascular endothelial growth factor (VEGF)-VEGF receptor 2 (VEGFR2) signaling plays crucial roles in angiogenesis, endothelial cell proliferation and migration. Here, we showed that ankyrin repeat and FYVE domain containing 1 (ANKFY1), a Rab5-GTP-interacting protein, is required for retinal endothelial cell proliferation and migration. ANKFY1 knockdown significantly suppressed cell growth of human retinal microvascular endothelial cells (HRMECs) in the presence or absence of VEGF. HRMEC migration was also inhibited by depletion of ANKFY1. Western blot analysis showed that ANKFY1 knockdown reduced cell surface VEGFR2 level. In contrast, qRT-PCR analysis indicated that ANKFY1 knockdown had no effect on VEGFR2 mRNA levels. We also found that the attenuation of the protein kinase B/endothelial nitric oxide synthase (Akt/eNOS) pathway in ANKFY1 knockdown HRMECs. In conclusion, our findings revealed novel functions of ANKFY1 in cell growth and migration of retinal endothelial cells.

Genetic Tools to Study Cardiovascular Biology

Progress in biomedical science is tightly associated with the improvement of methods and genetic tools to manipulate and analyze gene function in mice, the most widely used model organism in biomedical research. The joint effort of numerous individual laboratories and consortiums has contributed to the creation of a large genetic resource that enables scientists to image cells, probe signaling pathways activities, or modify a gene function in any desired cell type or time point, à la carte. However, as these tools significantly increase in number and become more sophisticated, it is more difficult to keep track of each tool's possibilities and understand their advantages and disadvantages. Knowing the best currently available genetic technology to answer a particular biological question is key to reach a higher standard in biomedical research. In this review, we list and discuss the main advantages and disadvantages of available mammalian genetic technology to analyze cardiovascular cell biology at higher cellular and molecular resolution. We start with the most simple and classical genetic approaches and end with the most advanced technology available to fluorescently label cells, conditionally target their genes, image their clonal expansion, and decode their lineages.

Role of Extracellular Matrix in Gastrointestinal Cancer-Associated Angiogenesis

Gastrointestinal tumors are responsible for more cancer-related fatalities than any other type of tumors, and colorectal and gastric malignancies account for a large part of these diseases. Thus, there is an urgent need to develop new therapeutic approaches to improve the patients' outcome and the tumor microenvironment is a promising arena for the development of such treatments. In fact, the nature of the microenvironment in the different gastrointestinal tracts may significantly influence not only tumor development but also the therapy response. In particular, an important microenvironmental component and a potential therapeutic target is the vasculature. In this context, the extracellular matrix is a key component exerting an active effect in all the hallmarks of cancer, including angiogenesis. Here, we summarized the current knowledge on the role of extracellular matrix in affecting endothelial cell function and intratumoral vascularization in the context of colorectal and gastric cancer. The extracellular matrix acts both directly on endothelial cells and indirectly through its remodeling and the consequent release of growth factors. We envision that a deeper understanding of the role of extracellular matrix and of its remodeling during cancer progression is of chief importance for the development of new, more efficacious, targeted therapies.

Familial pulmonary arterial hypertension by KDR heterozygous loss of function

Beyond the major gene BMPR2, several new genes predisposing to PAH have been identified during the last decade. Recently, preliminary evidence of the involvement of the KDR gene was found in a large genetic association study.We prospectively analysed the KDR gene by targeted panel sequencing in a series of 311 PAH patients referred to a clinical molecular laboratory for genetic diagnosis of PAH.Two index cases with severe PAH from two different families were found to carry a loss-of-function mutation in the KDR gene. These two index cases were clinically characterised by low diffusing capacity for carbon monoxide adjusted for haemoglobin (D _LCOc) and interstitial lung disease. In one family, segregation analysis revealed that variant carriers are either presenting with PAH associated with low D _LCOc, or have only decreased D _LCOc, whereas non-carrier relatives have normal D _LCOc. In the second family, a single affected carrier was alive. His carrier mother was unaffected with normal D _LCOc.We provided genetic evidence for considering KDR as a newly identified PAH-causing gene by describing the segregation of KDR mutations with PAH in two families. In our study, KDR mutations are associated with a particular form of PAH characterised by low D _LCOc and radiological evidence of parenchymal lung disease including interstitial lung disease and emphysema.

BMP9 signaling promotes the normalization of tumor blood vessels

The presence of an immature tumor vascular network contributes to cancer dissemination and the development of resistance to therapies. Strategies to normalize the tumor vasculature are therefore of significant therapeutic interest for cancer treatments. VEGF inhibitors are used clinically to normalize tumor blood vessels. However, the time frame and dosage of these inhibitors required to achieve normalization is rather narrow, and there is a need to identify additional signaling targets to attain vascular normalization. In addition to VEGF, the endothelial-specific receptor Alk1 plays a critical role in vascular development and promotes vascular remodeling and maturation. Therefore, we sought to evaluate the effects of the Alk1 ligand BMP9 on tumor vascular formation. BMP9 overexpression in Lewis Lung Carcinoma (LLC) tumors significantly delayed tumor growth. Blood vessels in BMP9-overexpressing LLC tumors displayed markers of vascular maturation and were characterized by increased perivascular cell coverage. Tumor vasculature normalization was associated with decreased permeability and increased perfusion. These changes in vascular function in BMP9-overexpressing LLC tumors resulted in significant alterations of the tumor microenvironment, characterized by a decrease in hypoxia and an increase in immune infiltration. In conclusion, we show that BMP9 promotes vascular normalization in LLC tumors that leads to changes in the microenvironment.

Overview of Crosstalk Between Multiple Factor of Transcytosis in Blood Brain Barrier

Blood brain barrier (BBB) conserves unique regulatory system to maintain barrier tightness while allowing adequate transport between neurovascular units. This mechanism possess a challenge for drug delivery, while abnormality may result in pathogenesis. Communication between vascular and neural system is mediated through paracellular and transcellular (transcytosis) pathway. Transcytosis itself showed dependency with various components, focusing on caveolae-mediated. Among several factors, intense communication between endothelial cells, pericytes, and astrocytes is the key for a normal development. Regulatory signaling pathway such as VEGF, Notch, S1P, PDGFβ, Ang/Tie, and TGF-β showed interaction with the transcytosis steps. Recent discoveries showed exploration of various factors which has been proven to interact with one of the process of transcytosis, either endocytosis, endosomal rearrangement, or exocytosis. As well as providing a hypothetical regulatory pathway between each factors, specifically miRNA, mechanical stress, various cytokines, physicochemical, basement membrane and junctions remodeling, and crosstalk between developmental regulatory pathways. Finally, various hypotheses and probable crosstalk between each factors will be expressed, to point out relevant research application (Drug therapy design and BBB-on-a-chip) and unexplored terrain.

Identification of a FGF18-expressing alveolar myofibroblast that is developmentally cleared during alveologenesis

Alveologenesis is an essential developmental process that increases the surface area of the lung through the formation of septal ridges. In the mouse, septation occurs postnatally and is thought to require the alveolar myofibroblast (AMF). Though abundant during alveologenesis, markers for AMFs are minimally detected in the adult. After septation, the alveolar walls thin to allow efficient gas exchange. Both loss of AMFs or retention and differentiation into another cell type during septal thinning have been proposed. Using a novel Fgf18:CreERT2 allele to lineage trace AMFs, we demonstrate that most AMFs are developmentally cleared during alveologenesis. Lung mesenchyme also contains other poorly described cell types, including alveolar lipofibroblasts (ALF). We show that Gli1:CreERT2 marks both AMFs as well as ALFs, and lineage tracing shows that ALFs are retained in adult alveoli while AMFs are lost. We further show that multiple immune cell populations contain lineage-labeled particles, suggesting a phagocytic role in the clearance of AMFs. The demonstration that the AMF lineage is depleted during septal thinning through a phagocytic process provides a mechanism for the clearance of a transient developmental cell population.

Regulation Networks Driving Vasculogenic Mimicry in Solid Tumors

Vasculogenic mimicry (VM) is a mechanism whereby cancer cells form microvascular structures similar to three-dimensional channels to provide nutrients and oxygen to tumors. Unlike angiogenesis, VM is characterized by the development of new patterned three-dimensional vascular-like structures independent of endothelial cells. This phenomenon has been observed in many types of highly aggressive solid tumors. The presence of VM has also been associated with increased resistance to chemotherapy, low survival, and poor prognosis. MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are non-coding RNAs that regulate gene expression at the post-transcriptional level through different pathways. In recent years, these tiny RNAs have been shown to be expressed aberrantly in different human malignancies, thus contributing to the hallmarks of cancer. In this context, miRNAs and lncRNAs can be excellent biomarkers for diagnosis, prognosis, and the prediction of response to therapy. In this review, we discuss the role that the tumor microenvironment and the epithelial-mesenchymal transition have in VM. We include an overview of the mechanisms of VM with examples of diverse types of tumors. Finally, we describe the regulation networks of lncRNAs-miRNAs and their clinical impact with the VM. Knowing the key genes that regulate and promote the development of VM in tumors with invasive, aggressive, and therapy-resistant phenotypes will facilitate the discovery of novel biomarker therapeutics against cancer as well as tools in the diagnosis and prognosis of patients.

Anti-VEGFR2 therapy delays growth of preclinical pediatric tumor models and enhances anti-tumor activity of chemotherapy

Vascular endothelial growth factor receptor 2 (VEGFR2) is an attractive therapeutic target in solid malignancies due to its central role in tumor angiogenesis. Ramucirumab (Cyramza^®, LY3009806) is a human monoclonal antibody specific for VEGFR2 approved for several adult indications and currently in a phase 1 clinical trial for pediatric patients with solid tumors (NCT02564198). Here, we evaluated ramucirumab in vitro and the anti-murine VEGFR2 antibody DC101 in vivo with or without chemotherapy across a range of pediatric cancer models. Ramucirumab abrogated in vitro endothelial cord formation driven by cancer cell lines representing multiple pediatric histologies; this response was independent of the origin of the tumor cell-line. Several pediatric cancer mouse models responded to single agent DC101-mediated VEGFR2 inhibition with tumor growth delay. Preclinical stable disease and partial xenograft regressions were observed in mouse models of Ewing’s sarcoma, synovial sarcoma, neuroblastoma, and desmoplastic small round cell tumor treated with DC101 and cytotoxic chemotherapy. In contrast, DC101 treatment in osteosarcoma models had limited efficacy alone or in combination with chemotherapeutics. Our data indicate differential efficacy of targeting the VEGFR2 pathway in pediatric models and support the continued evaluation of VEGFR2 inhibition in combination with cytotoxic chemotherapy in multiple pediatric indications.

Effect of FGF/FGFR pathway blocking on lung adenocarcinoma and its cancer-associated fibroblasts

Cancer-associated fibroblasts (CAFs) are known to promote tumourigenesis through various mechanisms. Fibroblast growth factor (FGF)/FGF receptor (FGFR)-dependent lung cancers have been described. We have developed a mouse model of lung adenocarcinoma that was constructed through the induction of Fgf9 overexpression in type 2 alveolar cells. The expression of Fgf9 in adult lungs resulted in the rapid development of multiple adenocarcinoma-like tumour nodules. Here, we have characterised the contribution of CAFs and the Fgf/Fgfr signalling pathway in maintaining the lung tumours initiated by Fgf9 overexpression. We found that CAF-secreted Fgf2 contributes to tumour cell growth. CAFs overexpressed Tgfb, Mmp7, Fgf9, and Fgf2; synthesised more collagen, and secreted inflammatory cell-recruiting cytokines. CAFs also enhanced the conversion of tumour-associated macrophages (TAMs) to the tumour-supportive M2 phenotype but did not influence angiogenesis. In vivo inhibition of Fgfrs during early lung tumour development resulted in significantly smaller and fewer tumour nodules, whereas inhibition in established lung tumours caused a significant reduction in tumour size and number. Fgfr inhibition also influenced tumour stromal cells, as it significantly abolished TAM recruitment and reduced tumour vascularity. However, the withdrawal of the inhibitor caused a significant recurrence/regrowth of Fgf/Fgfr-independent lung tumours. These recurrent tumours did not possess a higher proliferative or propagative potential. Our results provide evidence that fibroblasts associated with the Fgf9-induced lung adenocarcinoma provide multiple means of support to the tumour. Although the Fgfr blocker significantly suppressed the tumour and its stromal cells, it was not sufficient to completely eliminate the tumour, probably due to the emergence of alternative (resistance/maintenance) mechanism(s). This model represents an excellent tool to further study the complex interactions between CAFs, their related chemokines, and the progression of lung adenocarcinoma; it also provides further evidence to support the need for a combinatorial strategy to treat lung cancer. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.