Vascular endothelial growth factor: biology and therapeutic applications

While the development of anti-angiogenic therapy, as it pertains to cancer treatment, may still be in its infancy relative to well-established modalities such as chemotherapy, radiation, and surgery, major strides made in the past several decades have allowed translation of basic science discoveries in this field into clinical reality. The discovery of key molecular modulators of angiogenesis, notably vascular endothelial growth factor (VEGF), has catalyzed the development of numerous neutralizing therapeutic agents. The validity of VEGF inhibition as a therapeutic strategy has been well supported in randomized clinical trials, as well as U.S. Food and Drug Administration approval of the VEGF antagonists bevacizumab, sunitinib malate, sorafenib, pegaptinib and ranibizumab. Accordingly, this review will (1) briefly review the basic molecular biology of VEGF and (2) summarize recent progress in targeting the VEGF molecular pathway as therapy for angiogenic diseases such as cancer and age-related macular degeneration.     

Understanding telomerase in cancer stem cell biology

Comment on: Vicente-Dueñas C, et al. Oncotarget 2012; Epub ahead of print; PMID:22408137.     

Vascular endothelial growth factor increases the intracellular magnesium

Vascular endothelial growth factor (VEGF) is one of the key players in the process of angiogenesis. However, its underlying mechanism remains unclear. Mg2+ is the most abundant intracellular divalent cation in the body and plays critical roles in many cell functions. We investigated the effect of VEGF on intracellular Mg2+ in human umbilical vein endothelial cells (HUVECs). VEGF-A165 increased the intracellular Mg2+ concentration ([Mg2+]i) in a dose-dependent manner, with or without extracellular Mg2+, and the increase of [Mg2+]i was blocked by pretreatment with SU1498, tyrosine kinase inhibitors (tyrphostin A-23 and genistein), phosphatidylinositol 3-kinase (PI3K) inhibitors (wortmannin and LY294002) or phospholipase Cgamma (PLCgamma) inhibitor (U73122). In contrast, mitogen-activated protein kinase inhibitors (SB202190 and PD98059) had no effect on the VEGF-induced [Mg2+]i increase. These results suggest that VEGF-A165 increases the [Mg2+]i from the intracellular Mg2+ stores through the tyrosine kinase/PI3K/PLCgamma-dependent signaling pathways.     

Vascular endothelial growth factor receptor-2 in breast cancer

Investigations over the last decade have established the essential role of growth factors and their receptors during angiogenesis and carcinogenesis. The vascular endothelial growth factor receptor (VEGFR) family in mammals contains three members, VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1) and VEGFR-3 (Flt-4), which are transmembrane tyrosine kinase receptors that regulate the formation of blood and lymphatic vessels. In the early 1990s, the above VEGFR was structurally characterized by cDNA cloning. Among these three receptors, VEGFR-2 is generally recognized to have a principal role in mediating VEGF-induced responses. VEGFR-2 is considered as the earliest marker for endothelial cell development. Importantly, VEGFR-2 directly regulates tumor angiogenesis. Therefore, several inhibitors of VEGFR-2 have been developed and many of them are now in clinical trials. In addition to targeting endothelial cells, the VEGF/VEGFR-2 system works as an essential autocrine/paracrine process for cancer cell proliferation and survival. Recent studies mark the continuous and increased interest in this related, but distinct, function of VEGF/VEGFR-2 in cancer cells: the autocrine/paracrine loop. Several mechanisms regulate VEGFR-2 levels and modulate its role in tumor angiogenesis and physiologic functions, i.e.: cellular localization/trafficking, regulation of cis-elements of promoter, epigenetic regulation and signaling from Notch, cytokines/growth factors and estrogen, etc. In this review, we will focus on updated information regarding VEGFR-2 research with respect to the molecular mechanisms of VEGFR-2 regulation in human breast cancer. Investigations in the activation, function, and regulation of VEGFR-2 in breast cancer will allow the development of new pharmacological strategies aimed at directly targeting cancer cell proliferation and survival.     

Platelet-derived endothelial cell growth factor.

Platelet-derived endothelial cell growth factor (PD-ECGF) is a 45 kDa single chain polypeptide which stimulates endothelial cell growth and chemotaxis in vitro and angiogenesis in vivo. Analysis of a full length PD-ECGF cDNA revealed an open reading frame coding for 482 amino acids without homology to other known proteins. No signal sequence was observed, and analysis of the biosynthesis and processing of PD-ECGF in a thyroid carcinoma cell line revealed that PD-ECGF is released only very slowly. PD-ECGF becomes covalently associated with nucleotide triphosphates (e.g., ATP) in vivo, as well as in vitro. The physiological significance of this posttranslational modification remains to be elucidated. The tissue distribution and target cell specificity of PD-ECGF suggest roles in angiogenesis (e.g., during wound healing and in the developing placenta), as well as in the maintenance of the integrity of the endothelial cell lining of large vessels.     

Vascular endothelial growth factor promotes cardiomyocyte differentiation of embryonic stem cells

Embryonic stem cells (ESCs) overexpressing the vascular endothelial growth factor (VEGF) improve cardiac function in mouse models of myocardial ischemia and infarction by mechanisms that are poorly understood. Here we studied the effects of VEGF on cardiomyocyte differentiation of mouse ESCs in vitro. We used flow cytometry to determine the expression of alpha-myosin heavy chain (alpha-MHC), cardiac troponin I (cTn-I), and Nkx2.5 in differentiated ESCs. VEGF (20 ng/ml) significantly enhanced alpha-MHC, cTn-I, and Nkx2.5 expression in differentiated ESCs. Western blot analysis confirmed these findings. We found that VEGF receptor FMS-like tyrosine kinase-1 (Flt-1) and fetal liver kinase-1 (Flk-1) expression increased during ESC differentiation. Antibodies against Flk-1 totally blocked and against Flt-1 partially blocked VEGF-induced NKx2.5-positive-stained cells. The ERK inhibitor PD-098059 abolished VEGF-induced cardiomyocyte differentiation of ESCs. Our results suggest that VEGF promotes cardiomyocyte differentiation predominantly by ERK-mediated Flk-1 activation and, to a lesser extent, by Flt-1 activation. These findings may be of significance for stem cell and growth factor therapies to regenerate failing cardiomyocytes.     

Vascular endothelial growth factor and basic fibroblast growth factor in patients with squamous cell oesophageal cancer

It is suggested that vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) play an important role in tumor-induced angiogenesis. The purpose of this study was to estimate the correlation between VEGF and bFGF levels and tumor pathological status according to pTNM classification in patients with squamous cell oesophageal cancer. A group of 25 healthy controls and 32 consecutive patients with oesophageal cancer were included in this study. Serum VEGF and bFGF levels were determined by enzyme-linked immunosorbent assay (Quantikine R&D Systems). Serum VEGF and bFGF levels were significantly elevated in the patient groups (VEGF: 146.0 pg/ml, 79.0-386.3 pg/ml vs. 38.0 pg/ml, 6.5-135.1 pg/ml, p<0.005, and bFGF: 5.2 pg/ml, 1.2-10.6 pg/ml vs. 2.06 pg/ml, 0.07-4.0 pg/ml, p<0.02 Fisher test). The highest correlation between serum VEGF and bFGF levels were found in patients with advanced cancers, especially with: T4, N1, and M1 factors. The VEGF and bFGF levels were significantly higher in patients with pT4 (p<0.01). Patients with N1 lymph node invasion, compared with N0 factor, have higher levels of angiogenetic factors (p<0.04). Also in patients with advanced cancers with liver metastases the serum levels VEGF and bFGF were significantly higher (M1 vs. M0, VEGF p<0.001 and bFGF p<0.05). Consecutive monitoring of VEGF and bFGF serum levels may be a useful prognostic marker for patients with squamous cell oesophageal cancer.     

Vascular endothelial growth factor and substrate mechanics regulate in vitro tubulogenesis of endothelial progenitor cells

Endothelial progenitor cells (EPCs) in the circulatory system have been suggested to maintain vascular homeostasis and contribute to adult vascular regeneration and repair. These processes require that EPCs break down the extracellular matrix (ECM), migrate, differentiate and undergo tube morphogenesis. Evidently, the ECM plays a critical role by providing biochemical and biophysical cues that regulate cellular behaviour. Using a chemically and mechanically tunable hydrogel to study tube morphogenesis in vitro, we show that vascular endothelial growth factor (VEGF) and substrate mechanics co‐regulate tubulogenesis of EPCs. High levels of VEGF are required to initiate tube morphogenesis and activate matrix metalloproteinases (MMPs), which enable EPC migration. Under these conditions, the elasticity of the substrate affects the progression of tube morphogenesis. With decreases in substrate stiffness, we observe decreased MMP expression while increased cellular elongation, with intracellular vacuole extension and coalescence to open lumen compartments. RNAi studies demonstrate that membrane type 1‐MMP (MT1‐MMP) is required to enable the movement of EPCs on the matrix and that EPCs sense matrix stiffness through signalling cascades leading to the activation of the RhoGTPase Cdc42. Collectively, these results suggest that coupled responses for VEGF stimulation and modulation of substrate stiffness are required to regulate tube morphogenesis of EPCs.     

Vascular endothelial growth factor and its receptors

Vascular endothelial growth factor (VEGF) is a prime regulator of endothelial cell proliferation, angiogenesis, vasculogenesis and vascular permeability. Its activity is mediated by the high affinity tyrosine kinase receptors, KDR/Flk-1 and Flt-1. In this article, recently discovered structural, molecular and biological properties of VEGF are described. Among the topics discussed are VEGF and VEGF receptor structure and bioactivity, the regulation of VEGF expression, the role of VEGF and its receptors in vascular development, and the involvement of VEGF and its receptors in normal and pathological (ocular and tumor) angiogenesis.     

血管内皮生长因子与一氧化氮

血管内皮生长因子（ＶＥＧＦ）是内皮细胞特异性促有丝分裂原,具有促进内皮细胞增生、迁移及增加血管通透性的作用,其强大的促进新血管形成的作用使其在梗塞性血管病的基因治疗中发挥巨大作用。但其作用机制仍不清楚。研究表明ＶＥＧＦ与一氧化氮９ＮＯ）间存在密切关系,ＮＯ是ＶＥＧＦ发挥许多重要生理作用过程中必不可少的因素。探讨ＶＥＧＦ与ＮＯ的关系有助于进一步阐明ＶＥＧＦ的作用机制。     

Vascular endothelial growth factor in the lung

Vascular endothelial growth factor (VEGF) is a pluripotent growth and permeability factor that has a broad impact on endothelial cell function. The lung tissue is very rich in this protein; many different lung cells produce VEGF and also respond to VEGF. VEGF is critical for the development of the lung and serves as a maintenance factor during adult life. In addition to the physiological functions of this protein, there is increasing evidence that VEGF also plays a role in several acute and chronic lung diseases, such as acute lung injury, severe pulmonary hypertension, and emphysema. Here we provide a comprehensive overview of the rapidly expanding literature.     

血管内皮生长因子受体--结构与功能

血管内皮生长因子 (VEGF)的生物学效应是通过其特异的膜受体介导实现的。迄今发现VEGF有三种受体 ,受体的结构、功能 ,及VEGF的信号转导途径各不相同 ,也一直是VEGF研究的热点。本文主要综述了这方面的进展。     

Vascular endothelial growth factor promotes cardiac stem cell migration via the PI3K/Akt pathway

VEGF is a major inducer of angiogenesis. However, the homing role of VEGF for cardiac stem cells (CSCs) is unclear. In in vitro experiments, CSCs were isolated from the rat hearts, and a cellular migration assay was performed using a 24-well transwell system. VEGF induced CSC migration in a concentration-dependent manner, and SU5416 blocked this. Western blot analysis showed that the phosphorylated Akt was markedly increased in the VEGF-treated CSCs and that inhibition of pAkt activity significantly attenuated the VEGF-induced the migration of CSCs. In in vivo experiments, rat heart myocardial infarction (MI) was induced by left coronary artery ligation. One week after MI, the adenoviral vector expressing hVEGF165 and LacZ genes were injected separately into the infarcted myocardium at four sites before endomyocardial transplantation of 2 × 10⁵ PKH26 labeled CSCs (50 μL) at atrioventricular groove. One week after CSC transplantation, RT-PCR, immunohistochemical staining, Western blot, and ELISA analysis were performed to detect the hVEGF mRNA and protein. The expression of hVEGF mRNA and protein was significantly increased in the infarcted and hVEGF165 transfected rat hearts, accompanied by an enhanced PI3K/Ak activity, a greater accumulation of CSCs in the infarcted region, and an improvement in cardiac function. The CSC accumulation was inhibited by either the VEGF receptor blocker SU5416 or the PI3K/Ak inhibitor wortmannin. VEGF signaling may mediate the migration of CSCs via activation of PI3K/Akt.     

Vessel-associated stem cells from skeletal muscle: From biology to future uses in cell therapy

Over the last years, the existence of different stem cells with myogenic potential has been widely investigated. Besides the classical skeletal muscle progenitors represented by satellite cells, numerous multipotent and embryologically unrelated progenitors with a potential role in muscle differentiation and repair have been identified. In order to conceive a therapeutic approach for degenerative muscle disorders, it is of primary importance to identify an ideal stem cell endowed with all the features for a possible use in vivo. Among all emerging populations, vessel-associated stem cells are a novel and promising class of multipotent progenitors of mesodermal origin and with high myogenic potential which seem to best fit all the requirements for a possible cell therapy. In vitro and in vivostudies have already tested the effectiveness and safety of vessel-associated stem cells in animal models. This leads to the concrete possibility in the future to start pilot human clinical trials, hopefully opening the way to a turning point in the treatment of genetic and acquired muscle disorders.     

Vascular endothelial growth factor inhibits programmed cell death of endothelial cells induced by clinorotation

The principal aim of this study was to investigate short- and long-term effects of clinorotation on human endothelial cells (EA hy 926 cell line) using a three-dimensional random positioning machine. Moreover, the impact of vascular endothelial growth factor (VEGF) was addressed. Immediately, within one hour and after four and twenty-four hours an increase of apoptotic cells was detected. VEGF significantly inhibited the amount of apoptotic endothelial cells (EC). VEGF reduced the amount of fas-positive EC. Moreover, after 24 hours, proliferating EC grew in form of three-dimensional multicellular spheroids and also as monolayers. The initially formed spheroids (maximum diameter 3 mm) remained stable up to the 15th day of clinorotation. Some spheroids revealed tubular structures. In addition, a clear increase of extracellular matrix proteins such as osteopontin and fibronectin was measured. The three-dimensional clinostat represents an important tool for cell biological experiments. VEGF significantly attenuated the changes of endothelial cells induced by simulated weightlessness in a cell protective manner.