Vascular endothelial growth factor B, a novel growth factor for endothelial cells

Addition of PTK787/ZK 222584 can lower the dosage of amsacrine to achieve equal amounts of acute myeloid leukemia cell death

Acute myeloid leukemia (AML) is a disease with a poor prognosis. It has been demonstrated that AML cells express the vascular endothelial growth factors, VEGFA and VEGFC, as well as kinase insert domain-containing receptor (VEGFR2), the main receptor for downstream effects, resulting in an autocrine pathway for cell survival. This study investigates the role of the VEGFR inhibitor PTK787/ZK 222584 in leukemic cell death, and the possibility of an additional effect on cell death by a chemotherapeutic drug, amsacrine. In three AML cell lines and 33 pediatric AML patient samples, we performed total cell-kill assays to determine the percentages of cell death achieved by PTK787/ZK 222584 and/or amsacrine. Both drugs induced AML cell death. Using a response surface analysis, we could show that, in cell lines as well as in primary AML blasts, an equal magnitude of leukemic cell death could be obtained when lower doses of the more toxic amsacrine were combined with low dosages of the less toxic VEGFR inhibitor. This study shows that PTK787/ZK 222584 might have more clinical potential in AML when combined with a chemotherapeutic drug such as amsacrine. In future, it will be interesting to study whether the complications and the long-term effects of chemotherapy can be reduced by lowering the dosages of amsacrine, and by replacing it with other drugs with lower toxicity profiles, such as PTK787/ZK 222584.

Transgenic system for conditional induction and rescue of chronic myocardial hibernation provides insights into genomic programs of hibernation

A key energy-saving adaptation to chronic hypoxia that enables cardiomyocytes to withstand severe ischemic insults is hibernation, i.e., a reversible arrest of contractile function. Whereas hibernating cardiomyocytes represent the critical reserve of dysfunctional cells that can be potentially rescued, a lack of a suitable animal model has hampered insights on this medically important condition. We developed a transgenic mouse system for conditional induction of long-term hibernation and a system to rescue hibernating cardiomyocytes at will. Via myocardium-specific induction (and, in turn, deinduction) of a VEGF-sequestering soluble receptor, we show that VEGF is indispensable for adjusting the coronary vasculature to match increased oxygen consumption and exploit this finding to generate a hypoperfused heart. Importantly, ensuing ischemia is tunable to a level at which large cohorts of cardiomyocytes are driven to enter a hibernation mode, without cardiac cell death. Relieving the VEGF blockade even months later resulted in rapid revascularization and full recovery of contractile function. Furthermore, we show that left ventricular remodeling associated with hibernation is also fully reversible. The unique opportunity to uncouple hibernation from other ischemic heart phenotypes (e.g., infarction) was used to determine the genetic program of hibernation; uncovering hypoxia-inducible factor target genes associated with metabolic adjustments and induced expression of several cardioprotective genes. Autophagy, specifically self-digestion of mitochondria, was identified as a key prosurvival mechanism in hibernating cardiomyocytes. This system may lend itself for examining the potential utility of treatments to rescue dysfunctional cardiomyocytes and reverse maladaptive remodeling.

A single bout of exercise with high mechanical loading induces the expression of Cyr61/CCN1 and CTGF/CCN2 in human skeletal muscle

High mechanical loading was hypothesized to induce the expression of angiogenic and/or lymphangiogenic extracellular matrix (ECM) proteins in skeletal muscle. Eight men performed a strenuous exercise protocol, which consisted of 100 unilateral maximal drop jumps followed by submaximal jumping until exhaustion. Muscle biopsies were taken 30 min and 48 h postexercise from the vastus lateralis muscle and analyzed for the following parameters: mRNA and protein expression of ECM-associated CCN proteins [cysteine-rich angiogenic protein 61 (Cyr61)/CCN1, connective tissue growth factor (CTGF)/CCN2], and mRNA expression of vascular endothelial growth factors (VEGFs) and hypoxia-inducible factor-1α. The mRNA expression of Cyr61 and CTGF increased 30 min after the exercise (14- and 2.5-fold, respectively; P < 0.001). Cyr61 remained elevated 48 h postexercise (threefold; P < 0.05). The mRNA levels of VEGF-A, VEGF-B, VEGF-C, VEGF-D, or hypoxia-inducible factor-1α did not change significantly at either 30 min or 48 h postexercise; however, the variation between subjects increased markedly in VEGF-A and VEGF-B mRNA. Cyr61 protein levels were higher at both 30 min and 48 h after the exercise compared with the control ( P < 0.05). Cyr61 and CTGF proteins were localized to muscle fibers and the surrounding ECM by immunohistochemistry. Fast fibers stained more intensively than slow fibers. In conclusion, mechanical loading induces rapid expression of CCN proteins in human skeletal muscle. This may be one of the early mechanisms involved in skeletal muscle remodeling after exercise, since Cyr61 and CTGF regulate the expression of genes involved in angiogenesis and ECM remodeling.

Association between expression of vascular endothelial growth factor C, chemokine receptor CXCR4 and lymph node metastasis in colorectal cancer

OBJECTIVES

Lymph node metastasis is one of the determining factors of a poor prognosis for colorectal cancer. Recent studies have reported that cancer cells can promote lymphangiogenesis and that chemokine receptors expressed by cancer cells might play a role in metastasis. In this study, we examined the correlation between the expression of vascular endothelial growth factor (VEGF) C, the chemokine receptor CXCR4 and lymph node metastasis in colorectal cancer.

METHODS

One hundred and sixty-one consecutive patients who underwent resection at our department were studied. Lymph node metastasis was observed in 69 cases (43%) and lymphatic involvement was present in 105 cases (65%). Immunohistochemical staining was performed using antibodies for VEGF-C and CXCR4. Moreover, lymphatic vessel density (LVD) was evaluated within the tumor by immunostaining with a D2-40 antibody.

RESULTS

VEGF-C expression was found in 81 cases (50%) and CXCR4 expression in 87 cases (54%). Regarding the correlation between nodal metastasis and the expression of CXCR4 and VEGF-C, the incidence of nodal metastasis was significantly (p < 0.01) higher in patients with CXCR4-positive tumors than in those with CXCR4-negative tumors. In addition, a significant correlation was observed between CXCR4 and VEGF-C expression and lymphatic invasion (p < 0.01). LVD was significantly higher in VEGF-C-positive tumors compared with VEGF-C-negative tumors. However, there was no significant correlation between LVD and CXCR4 expression. Using multivariate analysis, VEGF-C, CXCR4, lymphatic invasion and wall invasion were found to be independent risk factors for lymph node metastasis.

CONCLUSIONS

This study suggests that although the mechanism that promoted lymph node metastasis was different between VEGF-C and CXCR4, both VEGF-C and CXCR4 contributed to lymphatic involvement and nodal metastasis in colorectal cancer.

Different networks, common growth factors: shared growth factors and receptors of the vascular and the nervous system

Growth factors and their respective receptors are key regulators during development and for homeostasis of the nervous system. In addition, changes in growth factor function, availability or downstream signaling is involved in many neuropathological disorders like Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, stroke and brain tumours. Research of the recent years revealed that some growth factors, initially discovered as neural growth factors are also affecting blood vessels [e.g. nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF)]. Likewise, vascular growth factors, such as vascular endothelial growth factor (VEGF), which was previously described as an endothelial cell specific mitogen, also affect neural cells. The discovery of shared growth factors affecting the vascular and the nervous system is of relevance for potential therapies of vascular and neurological diseases. This review aims to give an overview about the growing field of common growth factors and receptors within the two different networks.

Targeting the vascular endothelial growth factor pathway in the treatment of multiple myeloma

Multiple myeloma is a clonal plasma cell malignancy within the bone marrow associated with bone loss, renal disease and immunodeficiency. Despite new insights into the pathogenesis of multiple myeloma and novel targeted therapies, the median survival remains 3-5 years. It is now well established that the intimate relation between the tumor cells and components of the microenvironment plays a key role in multiple myeloma pathogenesis. Specifically, tumor cells impact the bone marrow and thereby cause immune suppression and lytic bone lesions; conversely, components of the bone marrow provide signals that influence the behavior of multiple myeloma cells, including tumor cell growth, survival, migration and drug resistance. Important contributing effectors are tumor cell-stroma cell and cell-extracellular matrix contacts, the bone marrow vasculature, and a variety of cytokines and growth factors in the bone marrow milieu.

Vascular endothelial growth factor and angiopoietin are required for prostate regeneration

BACKGROUND

The regulation of the prostate size by androgens may be partly the result of androgen effects on the prostatic vasculature. We examined the effect of changes in androgen levels on the expression of a variety of angiogenic factors in the mouse prostate and determined if vascular endothelial growth factor (VEGF)-A and the angiopoietins are involved in the vascular response to androgens.

METHODS

Expression of angiogenic factors in prostate was quantitated using real-time PCR at different times after castration and after administration of testosterone to castrated mice. Angiopoietins were localized in prostate by immunohistochemistry and in situ hybridization. The roles of VEGF and the angiopoietins in regeneration of the prostate were examined in mice inoculated with cells expressing soluble VEGF receptor-2 or soluble Tie-2.

RESULTS

Castration resulted in a decrease in VEGF-A, VEGF-B, VEGF-C, placenta growth factor, FGF-2, and FGF-8 expression after 1 day. In contrast, VEGF-D mRNA levels increased. No changes in angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), hepatocyte growth factor, VEGF receptor-1, VEGF receptor-2, or tie-2 mRNA levels were observed. Administration of testosterone to castrated mice had the opposite effect on expression of these angiogenic factors. Ang-2 was expressed predominantly in prostate epithelial cells whereas Ang-1 was expressed in epithelium and smooth muscle. Inoculation of mice with cells expressing soluble VEGF receptor-2 or Tie-2 blocked the increase in vascular density normally observed after administration of testosterone to castrated mice. The soluble receptors also blocked the increase in prostate weight and proliferation of prostatic epithelial cells.

CONCLUSION

VEGF-A and angiopoietins are required for the vascular response to androgens and for the ability of the prostate to regenerate in response to androgens.

Angiogenesis in cancer

New growth in the vascular network is important since the proliferation, as well as metastatic spread, of cancer cells depends on an adequate supply of oxygen and nutrients and the removal of waste products. New blood and lymphatic vessels form through processes called angiogenesis and lymphangiogenesis, respectively. Angiogenesis is regulated by both activator and inhibitor molecules. More than a dozen different proteins have been identified as angiogenic activators and inhibitors. Levels of expression of angiogenic factors reflect the aggressiveness of tumor cells. The discovery of angiogenic inhibitors should help to reduce both morbidity and mortality from carcinomas. Thousands of patients have received antiangiogenic therapy to date. Despite their theoretical efficacy, antiangiogeic treatments have not proved beneficial in terms of long-term survival. There is an urgent need for a new comprehensive treatment strategy combining antiangiogenic agents with conventional cytoreductive treatments in the control of cancer.

Pro-angiogenic cytokines and their role in tumor angiogenesis

The development of solid tumors depends upon an adequate supply of blood. This can be achieved by way of co-option of preexisting blood vessels and by the induction of angiogenesis. During the past 30 years, tumor angiogenesis had been found to play a crucial role in the progression of solid tumors. Tumor angiogenesis was found to be induced by a variety of pro-angiogenic cytokines of which the best characterized is vascular endothelial growth factor (VEGF). Indeed, the first FDA approved anti-angiogenic drug for the treatment of cancer is Avastin, a neutralizing antibody directed against VEGF. This review focuses on cytokines which have been reported to induce tumor angiogenesis.

Vascular endothelial growth factor family of ligands and receptors: review

VEGF signaling often represents a critical rate-limiting step in physiological angiogenesis. The VEGF family comprises seven secreted glycoproteins that are designated VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-E, placental growth factor (PlGF) and VEGF-F. The VEGF family members bind their cognate receptors. The receptors identified so far are designated VEGFR-1, VEGFR-2, VEGFR-3 and the neuropilins (NP-1 and NP-2). We review in this article the biology of the VEGF ligands and the receptors.

Vascular endothelial growth factors: biology and current status of clinical applications in cardiovascular medicine

Members of the vascular endothelial growth factor (VEGF) family are among the most powerful modulators of vascular biology. They regulate vasculogenesis, angiogenesis, and vascular maintenance during embryogenesis and in adults. Because of their profound effects on blood vessels, VEGFs have received much attention regarding their potential therapeutic use in cardiovascular medicine, especially for therapeutic vascular growth in myocardial and peripheral ischemia. However, completed randomized controlled VEGF trials have not provided convincing evidence of clinical efficacy. On the other hand, recent preclinical proangiogenic VEGF studies have given insight, and anti-VEGF studies have shown that the disturbance of vascular homeostasis by blocking VEGF-A may lead to endothelial dysfunction and adverse vascular effects. Excess VEGF-A may contribute to neovascularization of atherosclerotic lesions but, currently, there is no evidence that transient overexpression by gene transfer could lead to plaque destabilization. Here, we review the biology and effects of VEGFs as well as the current status of clinical applications and future perspectives of the therapeutic use of VEGFs in cardiovascular medicine.

Vascular endothelial growth factor-C expression in bladder transitional cell cancer and its relationship to lymph node metastasis

OBJECTIVE

To elucidate the role of vascular endothelial growth factor-C (VEGF-C) in bladder transitional cell carcinoma (TCC), examining VEGF-C expression in bladder TCC tissue and the association of VEGF-C with clinicopathological features, as the expression of VEGF-C in several carcinomas is significantly associated with angiogenesis, lymphangiogenesis and regional lymph node metastasis, but there are few reports of VEGF-C expression in bladder TCC.

PATIENTS AND METHODS

The study included 45 patients with bladder TCC; VEGF-C expression was assessed by immunohistochemistry and the association between VEGF-C expression and angiogenesis, as evaluated by microvessel density (MVD), was examined.

RESULTS

There was VEGF-C expression in the cytoplasm of tumour cells, but very little in the normal transitional epithelium. VEGF-C expression was significantly associated with tumour size, pathological T stage, pathological grade, lymphatic-venous involvement and pelvic lymph node metastasis (all P < 0.05). Multivariate analysis showed that VEGF-C expression was an exclusive independent factor influencing pelvic lymph node metastasis. Moreover, the patients with high VEGF-C expression had a markedly poorer prognosis than those with no or low VEGF-C expression (P = 0.014). A multivariate analysis based on the Cox proportional hazard model showed that lymph node metastasis was only an independent prognostic factor in the multivariate analysis using the Cox regression model (P = 0.010).

CONCLUSION

The present study provides evidence supporting the involvement of VEGF-C expression in the promotion of lymph node metastasis in bladder TCC. Examination of VEGF-C expression in biopsy specimens might be beneficial in predicting pelvic lymph node metastasis.

The prognostic value of vascular endothelial growth factors (VEGFs)-A and -B and their receptor, VEGFR-1, in invasive breast carcinoma

OBJECTIVES

Vascular endothelial growth factors A and B (VEGF-A and VEGF-B) play a major role in angiogenesis and activate VEGF receptor 1 (VEGFR-1). However, the clinicopathologic and clinical value of VEGF-B and VEGFR-1 in invasive breast carcinoma remains unclear.

METHODS

We immunohistochemically examined the expression pattern of VEGF-A, VEGF-B and VEGFR-1 in 177 invasive breast carcinomas in relation to clinicopathological parameters, p53, c-erbB2 proteins expression and patients' survival.

RESULTS

VEGF-A, VEGF-B and VEGFR-1 were immunodetected predominantly in the cytoplasm of the malignant cells. None of the studied markers correlated with any of the clinicopathological parameters, other than stromal VEGFR-1 which inversely correlated with PR (p=0.021). Cancerous VEGF-A and stromal VEGFR-1 were positively related to p53 (p=0.016 and p=0.033, respectively). Cancerous VEGF-B was positively associated with c-erbB-2 (p=0.045) and was found to exert an unfavorable impact on both disease-free and the overall survival of the node-positive patients (p=0.05 and p=0.029, respectively). Cancerous VEGFR-1 was recognized as being an independent poor prognostic indicator (p=0.037).

CONCLUSION

These findings suggest that, while VEGF-B seems to be useful as a prognostic indicator only in node-positive patients, VEGFR-1 may be an independent poor prognosticator in patients with invasive breast carcinoma.

Decreased Expression of VEGF-A in Rat Experimental Autoimmune Encephalomyelitis and in Cerebrospinal Fluid Mononuclear Cells from Patients with Multiple Sclerosis

Vascular endothelial growth factor A (VEGF-A) stimulates angiogenesis, but is also pro-inflammatory and plays an important role in the development of neurological disease, where it can have both attenuating and exacerbating effects. VEGF-B, a related molecule, is highly expressed in the central nervous system and seems to be important in neurological injury. A few studies have indicated that VEGF-A may play a role in the pathogenesis of multiple sclerosis (MS), but the role of VEGF-B has not been studied. We have studied the expression of VEGF-A, -B and their receptors by mRNA in situ hybridization, immunohistochemistry and real-time PCR in spinal cord from LEW rats with experimental autoimmune encephalomyelitis (EAE) and in cerebrospinal fluid (CSF) and blood samples from MS patients. Whereas VEGF-A is downregulated in glia in EAE, the infiltrating inflammatory cells are positive for VEGF-A. Expression of VEGF-B and the VEGF receptors is unaltered. In addition, the levels of VEGF-A mRNA in mononuclear cells [corrected] in CSF are lower in MS patients compared with controls. These results demonstrate a complex regulation of VEGF-A during neuroinflammation and suggest that VEGF-B is not involved in the pathogenesis of MS.

The regulation of vascular endothelial growth factors (VEGF-A, -C, and -D) expression in the retinal pigment epithelium

The vascular endothelial growth factor (VEGF) family plays an essential role in vascular development, angiogenesis and lymphangiogenesis. VEGF-A is a key regulator of endothelial cell functions and VEGF-C and VEGF-D are known to stimulate both angiogenesis and lymphangiogenesis. In a surgically removed subretinal vascular membrane of an age-related macular degeneration (AMD) patient, both VEGF-C and VEGF-D were confirmed, in addition to VEGF-A, to be markedly positive in the retinal pigment epithelium (RPE). There is no lymph vessel in ocular tissue, so it is possible that VEGF-C and VEGF-D expression in the RPE play some role in ocular angiogenesis, as well as VEGF-A. Next, we assessed the transition of VEGF-A, -C, and -D expression on several conditions, in human RPE. Hypoxia proverbially induced VEGF-A mRNA expression, meanwhile VEGF-C and VEGF-D mRNA expression was down-regulated. The Ca(2+) deprivation from culture medium strongly up-regulated VEGF-A and VEGF-D mRNA expression. Culture on plastic flasks precoated with poly-2-hydroxyethyl methacrylate up-regulated VEGF-D expression. Meanwhile, no significant change of VEGF-C mRNA expression was found in the blockade of cell-cell and/or cell-matrix adhesion. These findings suggest the possibility that VEGF-C and VEGF-D expression in RPE modify the ocular angiogenesis as angiogenic stimulators.

Molecular and functional diversity of vascular endothelial growth factors

Members of the vascular endothelial growth factor (VEGF) family are crucial regulators of neovascularization and are classified as cystine knot growth factors that specifically bind cellular receptor tyrosine kinases VEGFR-1, VEGFR-2, and VEGFR-3 with high but variable affinity and selectivity. The VEGF family has recently been expanded and currently comprises seven members: VEGF-A, VEGF-B, placenta growth factor (PlGF), VEGF-C, VEGF-D, viral VEGF (also known as VEGF-E), and snake venom VEGF (also known as VEGF-F). Although all members are structurally homologous, there is molecular diversity among the subtypes, and several isoforms, such as VEGF-A, VEGF-B, and PlGF, are generated by alternative exon splicing. These splicing isoforms exhibit differing properties, particularly in binding to co-receptor neuropilins and heparin. VEGF family proteins play multiple physiological roles, such as angiogenesis and lymphangiogenesis, while exogenous members (viral and snake venom VEGFs) display activities that are unique in physiology and function. This review will highlight the molecular and functional diversity of VEGF family proteins.

Expression and localization of VEGF-C and VEGFR-3 in glioblastomas and haemangioblastomas

Primary human brain tumours account for approximately 2% of all cancers. High levels of expression of vascular endothelial growth factor-A (VEGF-A), a potent angiogenic factor, are linked to poor prognosis. In contrast, the potential role in human brain tumour biology of newer VEGF family members, VEGF-C and VEGF-D, both of which are lymphangiogenic factors, is poorly understood. In the present study, the expression of all VEGFs (VEGF-A, -B, -C, and -D) and their receptors (VEGFR-1, -2, and -3) has been assessed in 39 primary human brain tumours. The well-established findings were confirmed with VEGF-A. Surprisingly, however, VEGF-C and VEGF-D, as well as VEGFR-3, were expressed in some tumour types such as haemangioblastomas and glioblastomas, despite their lack of lymphatic vessels. VEGF-C and VEGFR-3 transcripts were localized to the tumour palisade around necrotic areas in glioblastomas and were evenly distributed throughout haemangioblastomas. VEGF-C protein was localized by immunohistochemistry to the palisade layer in glioblastomas. More than 50% of VEGF-C-positive cells also expressed the intermediate-stage inflammatory macrophage marker CD163; however, a significant proportion of VEGF-C-positive cells were CD163-negative. These data demonstrate the presence of molecules, primarily described as regulators of lymphangiogenesis, in normal human brain and brain tumours that are devoid of lymphatics. Their localization in macrophages points to a role in tumour-associated inflammation.

Crystal structure of human vascular endothelial growth factor-B: identification of amino acids important for receptor binding

The development of blood vessels (angiogenesis) is critical throughout embryogenesis and in some normal postnatal physiological processes. Pathological angiogenesis has a pivotal role in sustaining tumour growth and chronic inflammation. Vascular endothelial growth factor-B (VEGF-B) is a member of the VEGF family of growth factors that regulate blood vessel and lymphatic angiogenesis. VEGF-B is closely related to VEGF-A and placenta growth factor (PlGF), but unlike VEGF-A, which binds to two receptor tyrosine kinases VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR), VEGF-B and PlGF bind to VEGFR-1 and not VEGFR-2. There is growing evidence of a role for VEGF-B in physiological and pathological blood vessel angiogenesis. VEGF-B may provide novel therapeutic strategies for the treatment of vascular disease and be a potential therapeutic target in aberrant vessel formation. To help understand at the molecular level the differential receptor binding profile of the VEGF family of growth factors we have determined the crystal structure of human VEGF-B(10-108) at 2.48 Angstroms resolution. The overall structure is very similar to that of the previously determined cysteine-knot motif growth factors: VEGF-A, PlGF and platelet-derived growth factor-B (PDGF-B). We also present a predicted model for the association of VEGF-B with the second domain of its receptor, VEGFR-1. Based on this interaction and the present structural data of the native protein, we have identified several putative residues that could play an important role in receptor recognition and specificity.

Soluble vascular endothelial growth factor receptor-1 in intrauterine growth restricted fetuses and neonates

BACKGROUND

Angiogenesis, a critical process for growth and development is altered in intrauterine growth restriction (IUGR). Vascular endothelial growth factor (VEGF) and its receptors VEGFR-1, soluble (s) VEGFR-1 and VEGFR-2 represent a regulatory system, essential for both physiological and pathological angiogenesis.

AIM

To study the implication of sVEGFR-1-a VEGF antagonist-in IUGR.

STUDY DESIGN

Prospective study.

METHODS

Twenty-five IUGR and 15 appropriate for gestational age (AGA) full-term fetuses and neonates with their mothers were included in the study.

OUTCOME MEASURES

sVEGFR-1 levels were determined by enzyme immunoassay in the serum of: mothers (MS), umbilical cords (UC)-representing fetal state - and neonates on day 1 (N1) and 4 (N4) of life.

RESULTS

MS, UC, N1 and N4 sVEGFR-1 levels in IUGR were significantly higher compared to respective AGA cases (p = 0.005, p = 0.026, p = 0.005 and p = 0.017, respectively). In IUGR and AGA groups, maternal sVEGFR-1 levels were significantly higher than fetal and neonatal levels (p in all cases < 0.001). The latter presented in both IUGR and AGA groups a significant decrease from UC to N4 (p in all cases < 0.01). MS, N1 and N4 sVEGFR-1 levels negatively correlated with the infants' customized centiles [(r = -0.489, p = 0.001), (r = -0.440, p = 0.004), (r = -0.431, p = 0.006), respectively].

CONCLUSIONS

Higher sVEGFR-1 levels in the IUGR as compared to the AGA group possibly reflect the predominance of antiangiogenic mechanisms present in IUGR. The decrease of sVEGFR-1 levels from UC to N4 may represent ex utero initiation of growth and development and therefore, prevalence of angiogenic mechanisms.

Angiogenic and cell survival functions of vascular endothelial growth factor (VEGF)

Vascular endothelial growth factor (VEGF) was originally identified as an endothelial cell specific growth factor stimulating angiogenesis and vascular permeability. Some family members, VEGF C and D, are specifically involved in lymphangiogenesis. It now appears that VEGF also has autocrine functions acting as a survival factor for tumour cells protecting them from stresses such as hypoxia, chemotherapy and radiotherapy. The mechanisms of action of VEGF are still being investigated with emerging insights into overlapping pathways and cross-talk between other receptors such as the neuropilins which were not previously associated with angiogenesis. VEGF plays an important role in embryonic development and angiogenesis during wound healing and menstrual cycle in the healthy adult. VEGF is also important in a number of both malignant and non-malignant pathologies. As it plays a limited role in normal human physiology, VEGF is an attractive therapeutic target in diseases where VEGF plays a key role. It was originally thought that in pathological conditions such as cancer, VEGF functioned solely as an angiogenic factor, stimulating new vessel formation and increasing vascular permeability. It has since emerged it plays a multifunctional role where it can also have autocrine pro-survival effects and contribute to tumour cell chemoresistance. In this review we discuss the established role of VEGF in angiogenesis and the underlying mechanisms. We discuss its role as a survival factor and mechanisms whereby angiogenesis inhibition improves efficacy of chemotherapy regimes. Finally, we discuss the therapeutic implications of targeting angiogenesis and VEGF receptors, particularly in cancer therapy.

The biology of vascular endothelial growth factor-B (VEGF-B)

The formation of new blood vessels (angiogenesis) is critical for both embryonic development and a variety of normal postnatal physiological processes. Various pathological processes, most notably tumour growth and chronic inflammation, are also known to be dependent on the new vessel formation. Amongst the variety of factors that contribute to the regulation of this complex process, vascular endothelial growth factor (VEGF or VEGF-A) is arguably the most well characterised. The VEGF family of growth factors is now known to comprise of VEGF-A plus four additional members, including VEGF-B. In contrast to VEGF-A, surprisingly little is known about the precise biological role of VEGF-B. Unlike VEGF-A, which binds to the two receptor tyrosine kinases VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR), VEGF-B binds only to VEGFR-1 and the functional significance of VEGFR-1 signalling has remained problematic. More recently, however, evidence has emerged suggesting a key role for VEGFR-1 signalling in pathological angiogenesis and this has raised the possibility that, like VEGF-A, VEGFR-1 specific ligands such as VEGF-B may provide for novel therapeutic strategies and/or represent new therapeutic targets. Here we review current knowledge of the biology of VEGF-B. We note that although analysis to date, including expression profiling and the generation of gene targetted mice, has provided only limited insights, future studies using recently generated recombinant proteins and antagonist monoclonal antibodies should provide for a more comprehensive understanding.

Vascular endothelial growth factor-B (VEGFB) stimulates neurogenesis: Evidence from knockout mice and growth factor administration

Vascular endothelial growth factor-B (VEGFB) is an angiogenic and neuroprotective protein that reduces hypoxic and ischemic neuronal injury. To determine if VEGFB also regulates neurogenesis in the adult brain, we studied the effects of VEGFB administration in vitro and in vivo, as well as the effect of VEGFB gene knockout (KO) in mice, on bromodeoxyuridine (BrdU) incorporation and expression of immature neuronal markers in the subgranular zone (SGZ) of the hippocampal dentate gyrus and the forebrain subventricular zone (SVZ). Intracerebroventricular VEGFB administration increased BrdU incorporation into cells of neuronal lineage both in vitro and in vivo, and VEGFB-KO mice showed impaired neurogenesis, consistent with a neurogenesis-promoting effect of VEGFB. In addition, intraventricular administration of VEGFB restored neurogenesis to wild-type levels in VEGFB-KO mice. These results suggest a role for VEGFB in the regulation of adult neurogenesis, which could have therapeutic implications for diseases associated with central neuronal loss.

Structure-function studies of two synthetic anti-vascular endothelial growth factor Fabs and comparison with the Avastin Fab

In the quest to discover new research tools and to develop better agents in the fight against cancer, two antibodies, G6 and B20-4, were isolated from synthetic antibody phage libraries. Unlike the AVASTINtrade mark antibody, a recently approved agent for the treatment of patients with colorectal cancer, B20-4 and G6 bind and block both human and murine vascular endothelial growth factor (VEGF). Here we have analyzed and compared the binding epitopes on VEGF for these three antibodies using alanine-scanning mutagenesis and structural analyses. The epitopes recognized by both synthetic antibodies are conserved between human and mouse VEGF, and they match closely to the receptor epitopes both structurally and functionally. In contrast, the Avastin epitope overlaps minimally with the receptor binding surface and centers around a residue that is not conserved in mouse. Our structural and functional analyses elucidate the cross-species reactivity of all three antibodies and emphasize the potential advantages of antibody generation using phage display as the resulting antibodies do not depend on sequence differences across species and preferentially target natural protein-protein interaction surfaces.

Transcriptional expression of the genes implicated in angiogenesis and tumor invasion in cervical carcinomas

OBJECTIVE

Co-expression patterns of the genes implicated in angiogenesis and tumor invasion in cervical carcinoma cells were investigated together with invasive activity of tumor cells. Transcript levels of those genes were also compared between tumor cells and normal cervical tissues.

METHODS

Real-time quantitative RT-PCR analysis was conducted on selected 11 genes (total VEGF-A, VEGF(121), VEGF(165), VEGF(189), VEGF-B, C and D, bFGF, dThdPase, MMP-2 and uPA) using 11 cervical carcinoma cell lines and 14 normal cervical tissues. Protein expression of VEGF-C and MMP-2 and invasive activity of tumor cells were evaluated for each cell line by sandwich ELISA and haptoinvasion assay, respectively.

RESULTS

Gene co-expression analysis revealed the significant correlation between angiogenic factors and proteinases in malignant but not in normal cervical samples. Gene or protein expression levels of VEGF-C and MMP-2 were well correlated with the number of invaded tumor cells. VEGF-A splicing variants were increased in malignant compared to normal cervical samples but not associated with the invasive activity of the cells.

CONCLUSION

VEGF-C and MMP-2 were closely related to invasive phenotype of tumor cells, whereas VEGF-A isoforms were considered to be involved in cervical carcinogenesis.

Homologs of vascular endothelial growth factor and receptor, VEGF and VEGFR, in the jellyfish Podocoryne carnea

Vascular endothelial growth factors (VEGF) are the major inducers of vasculogenesis and angiogenesis in vertebrates. Their effects are mediated by receptor tyrosine kinases of the VEGF receptor (VEGFR) family located on endothelial cells and include stimulation of cell survival, proliferation, migration, and tube formation as well as regulation of vascular permeability. Here, we report the presence of VEGF and VEGFR homologous genes in a basal invertebrate of the phylum Cnidaria. The marine jellyfish Podocoryne carnea features a gastrovascular system consisting of the feeding organ, or manubrium, the radial and ring canals, and the tentacle bulbs. Expression analysis indicates that both genes are involved in tentacle and gastrovascular canal formation, indicating an early recruitment of the VEGF signalling pathway for morphogenetic processes leading to tube formation in metazoans. The evolutionary origin of the VEGF signalling pathway resides in the common ancestor of the Cnidaria and Bilateria.

PTK787/ZK222584, a tyrosine kinase inhibitor of vascular endothelial growth factor receptor, reduces uptake of the contrast agent GdDOTA by murine orthotopic B16/BL6 melanoma tumours and inhibits their growth in vivo

Assessment of tumour vascularity may characterize malignancy as well as predict responsiveness to anti-angiogenic therapy. Non-invasive measurement of tumour perfusion and blood vessel permeability assessed as the transfer constant, K(trans), can be provided by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Using the orthotopic murine tumour model B16/BL6 melanoma, the small contrast agent GdDOTA (DOTAREM(R); Guerbet, Paris) was applied to assess the vascular transfer constant, K(trans), and interstitial leakage space, whereas intravascular iron oxide nanoparticles (Endorem(R); Guerbet, Paris) were used to detect relative tumour blood volume (rTBV), and in one experiment blood flow index (BFI). No correlations were observed between these four parameters (r(2) always <0.05). The B16/BL6 primary tumour and lymph-node cervical (neck) metastases produced high levels of the permeability/growth factor, VEGF. To probe the model, the novel VEGF receptor (VEGF-R) tyrosine kinase inhibitor, PTK787/ZK222584 (PTK/ZK) was tested for anti-tumour efficacy and its effects on DCE-MRI measured parameters of tumour vascularity. Data from the non-invasive measure of tumour vascularity were compared with a histological measurement of vasculature using the DNA-staining dye H33342. PTK/ZK inhibited growth of the primary and, particularly, cervical tumour metastases following chronic treatment for 2 weeks (50 or 100 mg/kg daily) of 1-week-old tumours, or with 1 week of treatment against more established (2-week-old) tumours. After chronic treatment with PTK/ZK, DCE-MRI detected significant decreases in K(trans) and interstitial leakage space, but not rTBV of both primary tumours and cervical metastases. Histological data at this time-point showed a significant decrease in blood vessel density of the cervical metastases but not the primary tumours. However, in the cervical metastases, the mean blood vessel width was increased by 38%, suggesting overall no marked change in blood volume. After acute (2-4 day) treatment, DCE-MRI of the cervical metastases demonstrated a significant decrease in K(trans) and interstitial leakage space and also in the initial area under the enhancement curve for GdDOTA (IAUC), but no change in the rTBV or BFI. Thus, significant changes could be detected in the DCE-MRI measurement of tumour uptake of a small contrast agent prior to changes in tumour size, which suggests that DCE-MRI could be applied in the clinic as a rapid and sensitive biomarker for the effects of VEGF-R inhibition on tumour blood vessel permeability and thus may provide an early marker for eventual tumour response.

Gene expression profiling of human atrial myocardium with atrial fibrillation by DNA microarray analysis

BACKGROUND

Atrial fibrillation (AF) is the most frequently encountered arrhythmia in the clinical setting. However, a comprehensive investigation of the molecular mechanism of AF has not been performed. The aim of this study was to clarify transcriptional profiling of genes modulated in the atrium of AF patients using DNA microarray technology.

METHODS

We obtained 17 fresh cardiac specimens, right atrial appendages, isolated from 10 patients with normal sinus rhythm and seven chronic AF patients who underwent cardiac surgery. Affymetrix GeneChip (Human Genome U95A) investigating 12,000 human genes was used for each specimen. Quantitative analysis of selected genes was performed by the real-time PCR method.

RESULTS

The left atrial diameter in the AF group was greater than that in the sinus rhythm group. We could identify 33 AF-specific genes that were significantly activated (>1.5-fold), compared with the sinus rhythm group, including an ion channel, an antioxidant, an inflammation, three cell growth/cell cycle, three transcription such as nuclear factor-interleukin 6-beta, several cell signaling and several protein genes, and seven expressed sequence tags (ESTs). In contrast, we found 63 sinus rhythm-specific genes, including several cell signaling/communication such as sarcoplasmic reticulum Ca2+-ATPase 2, several cellular respiration and energy production and two antiproliferative or negative regulator of cell growth genes, and 22 ESTs.

CONCLUSIONS

The present study demonstrated that about one hundred genes were modulated in the atria of AF patients. These findings suggest that these genes may play critical roles in the initiation or perpetuation of AF and the pathophysiology of atrial remodeling.

Phase I Study of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of PTK787/ZK 222584 Administered Twice Daily in Patients With Advanced Cancer

Purpose

PTK787/ZK 222584 (PTK/ZK) is an oral angiogenesis inhibitor targeting all known vascular endothelial growth factor (VEGF) receptor tyrosine kinases, including VEGFR-1/Flt-1, VEGFR-2/KDR, VEGFR-3/Flt-4, the platelet-derived growth factor receptor tyrosine kinase, and the c-kit protein tyrosine kinase. In this phase I dose-escalating study, PTK/ZK was administered bid to exploit the theoretical advantage of maintaining constant drug levels above a threshold known from preclinical data to interfere with VEGF receptor signaling.

Patients and Methods

Forty-three patients with advanced cancers received single-agent PTK/ZK at doses of 150 to 1,000 mg orally bid. Assessments for safety and pharmacokinetics were performed. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used as a pharmacodynamic marker of response.

Results

At 1,000 mg bid, the dose-limiting toxicity of reversible grade 3 lightheadedness was observed. Dose-related grade 3 fatigue and vomiting were observed but these were not dose-limiting. Pharmacokinetic data confirmed that PTK/ZK exposure increased with increasing dose up to 500 mg bid and appeared to plateau at higher doses. A greater than 40% reduction in the DCE-MRI bidirectional transfer constant (Ki) at day 2 predicted for nonprogression of disease.

Conclusion

The maximum-tolerated oral dose of PTK/ZK is 750 mg orally bid. DCE-MRI and pharmacokinetic data indicate that PTK/ZK ≥ 1,000 mg total daily dose is the biologically active dose.

Therapeutic targeting of receptor tyrosine kinases in lung cancer

Lung cancer is a difficult illness with a poor overall survival. Even though combination strategies with chemotherapy, radiation therapy and surgery have all been utilised, the overall outcome for this disease continues to be relatively disappointing. In order to make a difference in the treatment of lung cancer, novel therapeutics will have to be developed. Through basic biological studies, a number of receptor tyrosine kinases have been implicated in the pathogenesis and progression of lung cancer. In this review, the authors summarise the mechanisms of several major receptor tyrosine kinases in lung cancer, especially epidermal growth factor receptor, Her2/neu, MET, vascular endothelial growth factor and KIT. The biology associated with these receptors is described, and the various novel therapeutic inhibitory strategies that are ongoing in preclinical and clinical studies for lung cancer are detailed. Through understanding of receptor tyrosine kinases and the utilisation of specific inhibitors, it is hopeful that a dramatic impact will be made on the biology and therapy for lung cancer.

Autocrine and Paracrine Regulation of Interleukin-8 Expression in Lung Cancer Cells

We had previously demonstrated that lung cancer cells, upon contact with macrophages, could be induced to secrete angiogenic factors to promote tumor angiogenesis. In this study, we focused on the paracrine and autocrine regulation of interleukin (IL)-8 expression in sensitized lung cancer cells after interacting with macrophages. We found that the IL-8 mRNA expression in lung cancer cells significantly increased after coculture with phorbol myristate acetate-treated THP-1 cells and human primary lung macrophages. Fresh lung cancer CL1-5 cells cocultured with macrophage-sensitized lung cancer cells still had a 35% of increase in IL-8 mRNA expression. The addition of anti-inflammatory agents pyrrolidine dithiocarbamate, pentoxifylline, aspirin, and dexamethasone could completely suppress the expression of IL-8 mRNA in fresh/sensitized lung cancer cell cocultures. Human recombinant tumor necrosis factor (TNF)-alpha and IL-1alpha could induce IL-8 expression in lung cancer cells in a dose-dependent manner. Neutralization with TNF-alpha and IL-1alpha antibodies in cocultures decreased the levels of IL-8 expression in sensitized lung cancer cells. Nuclear factor-kappaB transcriptional activity was also suppressed by the same antibodies, as confirmed by a reporter gene assay and the electrophoretic mobility shift assay. Our results highly suggest that both autocrine and paracrine regulation are involved in IL-8 expression of lung cancer cells cocultured with macrophage. Also, the regulations of IL-8 expression in lung cancer cells were through the nuclear factor-kappaB pathway and modulated by TNF-alpha and IL-1alpha.

Classification analysis of the transcriptosome of nonlesional cultured dermal fibroblasts from systemic sclerosis patients with early disease

OBJECTIVE

To compare the transcriptosome of early-passage nonlesional dermal fibroblasts from systemic sclerosis (SSc) patients with diffuse disease and matched normal controls in order to gain further understanding of the gene activation patterns that occur in early disease.

METHODS

Total RNA was isolated from early-passage fibroblasts obtained from nonlesional skin biopsy specimens from 21 patients with diffuse SSc (disease duration <5 years in all but 1) and 18 healthy controls who were matched to the cases by age (+/-5 years), sex, and race. Array experiments were performed on a 16,659-oligonucleotide microarray utilizing a reference experimental design. Supervised methods were used to select differentially expressed genes. Quantitative polymerase chain reaction (PCR) was used to independently validate the array results.

RESULTS

Of the 8,324 genes that passed filtering criteria, classification analysis revealed that <5% were differentially expressed between SSc and normal fibroblasts. Individually, differentially expressed genes included COL7A1, COL18A1 (endostatin), DAF, COMP, and VEGFB. Using the panel of genes discovered through classification analysis, a set of model predictors that achieved reasonably high predictive accuracy was developed. Analysis of 1,297 gene ontology (GO) classes revealed 35 classes that were significantly dysregulated in SSc fibroblasts. These GO classes included anchoring collagen (30934), extracellular matrix structural constituent (5201), and complement activation (6958, 6956). Validation by quantitative PCR demonstrated that 7 of 7 genes selected were concordant with the array results.

CONCLUSION

Fibroblasts cultured from nonlesional skin of patients with SSc already have detectable abnormalities in a variety of genes and cellular processes, including those involved in extracellular matrix formation, fibrillogenesis, complement activation, and angiogenesis.

VEGF and its receptors (flt-1 and KDR/flk-1) as prognostic indicators in endometrial carcinoma

Vascular endothelial growth factor (VEGF) is associated with increased angiogenesis and aggressive tumour growth. We investigated the expression and clinical significance of VEGF and its receptors, flt-1 and KDR/flk-1, in patients with uterine endometrial carcinoma. The series consisted of 115 endometrioid endometrial adenocarcinoma patients with FIGO stage I-IV. Additionally, samples from 3 patients with adenoacanthoma and 12 patients with poor prognostic variants of endometrial carcinoma were examined. Immunohistochemical assessment was classified as negative or positive based on staining intensity. The median follow-up time of patients with endometrioid endometrial adenocarcinoma was 87 months. In endometrioid endometrial carcinomas, the positive immunostaining rate was 39% for VEGF, 65% for flt-1 and 68% for KDR/flk-1. There was a significant correlation between VEGF and both its receptors. Furthermore, this receptor expression was correlated between the two types of receptors. VEGF-, flt-1- and KDR/flk-1-positive immunostainings were not related to poor prognosis. We conclude that VEGF, flt-1 and KDR/flk-1 expressions are not useful prognostic markers for overall survival in patients with endometrioid endometrial carcinoma.

Vascular Endothelial Growth Factor-C Expression and Invasive Phenotype in Ovarian Carcinomas

PURPOSE

To investigate the biological correlation between vascular endothelial growth factor (VEGF)-C expression and invasive phenotype in ovarian carcinomas.

EXPERIMENTAL DESIGN

Gene and protein expression levels of VEGF-C in 10 ovarian carcinoma cell lines were correlated with invasive activity of the cells. The correlation between immunohistochemical expression of VEGF-C and tumor aggressiveness in 73 ovarian carcinomas was also examined with respect to clinicopathologic features and patient outcome.

RESULTS

VEGF-C gene and protein expression differed remarkably among the cell lines, and there was a statistical correlation among VEGF-C expression, in vitro invasive activity, and matrix metalloproteinase-2 (MMP-2) gene expression and its activity. Anti-VEGF-C and anti-MMP-2 antibodies inhibited the invasive activity of tumor cells. VEGF-C expression in clinical tissue samples was well correlated with clinical stages, retroperitoneal lymph node metastasis, MMP-2 expression, angiogenesis, lymphangiogenesis, and low apoptotic index (AI). The patients whose tumors had strong VEGF-C expression and low AI underwent a poorer prognosis than did those with weak VEGF-C expression and high AI.

CONCLUSION

VEGF-C expression is closely related to invasive phenotype and affects the patient's survival in ovarian carcinomas.

Expression of vascular endothelial growth factors and their receptors in human endometrium from women experiencing abnormal bleeding patterns after prolonged use of a levonorgestrel-releasing intrauterine system

BACKGROUND

Menstrual bleeding disturbances are a common initial complaint among users of the levonorgestrel-releasing intrauterine system (LNG-IUS). In this study, women who experienced bleeding disturbances recurring after a previous period of problem-free use and who therefore wanted removal of their LNG-IUD were investigated. Vascular endothelial growth factors (VEGFs) and their receptors are thought to be involved in normal endometrial angiogenesis. The aim of the study was to elucidate the possible association of these VEGF and receptors with bleeding disturbances among users of LNG-IUS.

METHODS

Endometrial biopsies were obtained from users of the LNG-IUS who complained of bleeding disturbances (n = 17) and from women without such problems (n = 14). The endometrial expression of these VEGFs and their receptors was analysed using immunohistochemistry.

RESULTS

Endometrial endothelial cells from LNG-IUS users with menstrual bleeding disturbances exhibited significantly higher immunoreactivity for VEGFR-1 and VEGFR-3 than those from women without bleeding disturbances. Stromal cells showed significantly lower immunoreactivity for VEGF-A in samples from LNG-IUS users with bleeding disturbances than in those without.

CONCLUSION

Changes in the expression of these angiogenic growth factors and their receptors in LNG-IUS-exposed endometrium might be involved in the formation of fragile and dysfunctional blood vessels that subsequently give rise to bleeding disturbances.

Serum vascular endothelial growth factor (VEGF) and VEGF-C levels as tumor markers in patients with cervical carcinoma

BACKGROUND

Vascular endothelial growth factor (VEGF) and VEGF-C play a crucial role in the regulation of tumor growth and metastasis. The current study examined the significance of serum VEGF and VEGF-C levels in relation to conventional clinicopathologic parameters, response to treatment, and survival in patients with cervical carcinoma.

METHODS

Between December 1999 and March 2004, serum VEGF and VEGF-C levels were analyzed in 78 patients with cervical carcinoma undergoing primary treatment (primary surgery [n=40] and radiotherapy [n=38]), as well as in 30 healthy controls. Serum VEGF and VEGF-C levels were assessed by enzyme-linked immunosorbent assay before and within 2 weeks after treatment.

RESULTS

Serum VEGF and VEGF-C levels were higher in patients with cervical carcinoma than in the healthy control (P=0.0002 and P=0.0007, respectively). Both VEGF and VEGF-C concentrations increased significantly in patients with squamous cell carcinoma (SCC vs. normal control: P<0.0001 and P=0.0001, respectively), but not in adenocarcinoma (vs. normal control: P=0.2982 and P=0.7766, respectively). In an analysis of SCC, the pretherapeutic serum levels of VEGF and VEGF-C correlated significantly with advanced International Federation of Gynecology and Obstetrics stage and large tumor size, but not with lymph node metastasis. The pretherapeutic serum level of VEGF-C also correlated significantly with disease recurrence or persistence after treatment. Both serum VEGF and VEGF-C levels decreased significantly after treatment.

CONCLUSIONS

The serum levels of both VEGF and VEGF-C have potential usefulness as biologic markers of SCC of the uterine cervix.

Constitutive and inducible expression and regulation of vascular endothelial growth factor

Vascular endothelial growth factor (VEGF), which was originally discovered as vascular permeability factor, is critical to human cancer angiogenesis through its potent functions as a stimulator of endothelial cell survival, mitogenesis, migration, differentiation and self-assembly, as well as vascular permeability, immunosuppression and mobilization of endothelial progenitor cells from the bone marrow into the peripheral circulation. Genetic alterations and a chaotic tumor microenvironment, such as hypoxia, acidosis, free radicals, and cytokines, are clearly attributed to numerous abnormalities in the expression and signaling of VEGF and its receptors. These perturbations confer a tremendous survival and growth advantage to vascular endothelial cells as manifested by exuberant tumor angiogenesis and a consequent malignant phenotype. Understanding the regulatory mechanisms of both inducible and constitutive VEGF expression will be crucial in designing effective therapeutic strategies targeting VEGF to control tumor growth and metastasis. In this review, molecular regulation of VEGF expression in tumor cells is discussed.

Vascular endothelial growth factor and related molecules in acute lung injury

VEGFs and their receptors have been implicated in the regulation of vascular permeability in many organ systems, including the lung. Increased permeability and interstitial and pulmonary edema are prominent features of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Extrapolating data from other organ systems and animal experiments have suggested that overexpression of VEGF functions primarily as proinjurious molecules in the lung. Recent data, from animal models as well as from patients with ARDS, have shown decreased levels of VEGF in the lung. The role of VEGF and related molecules in ALI/ARDS is, therefore, controversial: what has become clear is that there are many unique features in the regulation of pulmonary vascular permeability and in VEGF expression in the lung. In this review, we explore a growing body of literature looking at the expression and function of VEGF and related molecules in different models of ALI and in patients with ALI/ARDS. Novel evidence points to a potential role of VEGF in promoting repair of the alveolar-capillary membrane during recovery from ALI/ARDS. Understanding the role of VEGF in this disease process is crucial for developing new therapeutic strategies for ALI/ARDS.

Tyrosine kinases in disease: overview of kinase inhibitors as therapeutic agents and current drugs in clinical trials

Tyrosine kinases, first described as oncogenes, have been shown to play a role in normal cellular processes. Aberrations in tyrosine kinase activity lead to disease states. For fifteen years it has been postulated that the inhibition of tyrosine kinases may have therapeutic utility and the design and testing of inhibitors have been major focuses of research and development in both academic institutions and pharmaceutical companies. While early research focused on developing chemical entities that mimic phosphotyrosine, later research has focused on developing competitive adenosine triphosphate (ATP) inhibitors with various levels of selectivity on kinase targets. This review focuses on a discussion of tyrosine kinases thought to be important in disease, including platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), vascular endothelial cell growth factor (VEGF), epidermal growth factor (EGF) receptors, HER-2 and Src. In addition, the classes of inhibitors designed to affect these targets and that have overcome research and development challenges and entered clinical trials are discussed. These include isoxazole, quinazoline, substituted pyrimidines and indolinone compounds, all of which are in clinical trials or near clinical development by SUGEN, Zeneca, Novartis, Pfizer and Parke-Davis. A summary of the chemistry and activity of these agents is provided.

Concentration of cord serum placenta growth factor in normal and diabetic pregnancies

OBJECTIVE

To investigate whether maternal diabetes or diabetes-related complications, such as macrosomia and chronic fetal hypoxia, are associated with altered placenta growth factor (PlGF) levels in cord serum.

DESIGN

Case-control study.

SETTING

Helsinki University Central Hospital, Helsinki, Finland.

POPULATION

Sixty-two normal pregnancies, 67 pregnancies complicated by type 1 diabetes and 28 pregnancies complicated by insulin-treated gestational diabetes.

METHODS

Cord serum PlGF concentration was measured by an enzyme-linked immunosorbent assay. Amniotic fluid erythropoietin concentration was measured by a chemiluminescent immunologic method. Umbilical artery gas variables were analysed with standard blood gas and pH electrodes.

MAIN OUTCOME MEASURE

PlGF concentration in cord serum at birth.

RESULTS

Cord serum PlGF concentration was similar in normal pregnancies [13.4 (1.0) ng/L], in pregnancies complicated by type 1 diabetes [15.1 (1.8) ng/L, P= 0.583 vs controls] and in pregnancies complicated by insulin-treated gestational diabetes [13.6 (0.9) ng/L, P= 0.991 vs controls]. Cord serum PlGF did not correlate with relative birthweight. In diabetic pregnancies, cord serum PlGF correlated negatively with amniotic fluid erythropoietin (r=-0.449, P < 0.0001) and positively with umbilical artery Po(2) (r= 0.333, P= 0.001). There was a trend toward lower cord serum PlGF levels in diabetic pregnancies with pre-eclampsia compared with those without any hypertensive disorders.

CONCLUSIONS

Maternal diabetes per se is not associated with altered PlGF levels in cord serum. The correlation between PlGF and indices of fetal hypoxia in diabetic pregnancies may be related to the role of PlGF in potentiating the angiogenic response to vascular endothelial growth factor in ischaemia.

Targeting vascular endothelial growth factor and angiogenesis for the treatment of colorectal cancer

Angiogenesis, the development and proliferation of new blood vessels, is critical for the growth of tumors. The process of new blood vessel formation is under complex control from a variety of pro- and anti-angiogenesis factors. By identifying and understanding these factors, new therapies have been developed to inhibit tumor growth and survival by blocking tumor-related angiogenesis. Recent success with the monoclonal antibody against vascular endothelial growth factor (VEGF; bevacizumab) in a large, randomized, phase III study has provided a critical proof of principle for this therapeutic area. This review will outline the biology of angiogenesis in colorectal cancer and discuss the current status of angiogenesis inhibition in its treatment.

Pharmacology and Pharmacodynamics of Bevacizumab as Monotherapy or in Combination with Cytotoxic Therapy in Preclinical Studies

Preclinical models have examined the pharmacologic and pharmacodynamic activities of an anti–vascular endothelial growth factor (VEGF) humanized, monoclonal antibody, bevacizumab, and/or its murine equivalent A4.6.1. These studies found that single-agent therapy with bevacizumab/A4.6.1 resulted in tumor growth inhibition of 20 different human tumor cell lines (13 tumor types) implanted into nude mice irrespective of the route of administration or tumor location. Several of these studies also observed significant inhibition of tumor metastases. Various studies have examined the feasibility of combining anti-VEGF therapy with cytotoxic or biological agents. Combining bevacizumab/A4.6.1 with doxorubicin, topotecan, paclitaxel, docetaxel, or radiotherapy resulted in additive or synergistic tumor growth inhibition. Changes in vascular functions were frequently reported, including decreased vessel diameter, density, and permeability in response to treatment. A reduction in interstitial fluid pressure was also observed. In some studies, these improvements resulted in an increase in intratumoral uptake of chemotherapy, implying that the most effective use of anti-VEGF therapy is in combination with chemotherapy. Alternatively, combination treatment with radiation increased tumor oxygenation and tumor growth inhibition. Interestingly, anti-VEGF therapy has also been reported to reduce the development of ascites in ovarian mouse models. Finally, safety pharmacology studies with bevacizumab in cynomolgus monkeys showed that this agent is generally well tolerated with no unexpected adverse events.

The vascular endothelial growth factor (VEGF) family: angiogenic factors in health and disease

Vascular endothelial growth factors (VEGFs) are a family of secreted polypeptides with a highly conserved receptor-binding cystine-knot structure similar to that of the platelet-derived growth factors. VEGF-A, the founding member of the family, is highly conserved between animals as evolutionarily distant as fish and mammals. In vertebrates, VEGFs act through a family of cognate receptor kinases in endothelial cells to stimulate blood-vessel formation. VEGF-A has important roles in mammalian vascular development and in diseases involving abnormal growth of blood vessels; other VEGFs are also involved in the development of lymphatic vessels and disease-related angiogenesis. Invertebrate homologs of VEGFs and VEGF receptors have been identified in fly, nematode and jellyfish, where they function in developmental cell migration and neurogenesis. The existence of VEGF-like molecules and their receptors in simple invertebrates without a vascular system indicates that this family of growth factors emerged at a very early stage in the evolution of multicellular organisms to mediate primordial developmental functions.

Localization of the VEGF and angiopoietin genes in uterine carcinosarcoma

OBJECTIVE

Carcinosarcoma of the uterus is a highly aggressive tumor. However, the angiogenesis in this tumor remains unclear. This is the first study to examine the characteristics of angiogenesis in this tumor at the molecular level while also comparing the findings with those of high-grade endometrial carcinoma.

METHODS

The expression of vascular endothelial growth factors (VEGF) and angiopoietins (Ang) genes were examined in 35 primary uterine carcinosarcomas as well as in 12 high-grade endometrial carcinomas by in situ hybridization.

RESULTS

A strong expression of VEGF-A mRNA was significantly seen in carcinosarcomas compared to high-grade endometrial carcinomas. Interestingly, in uterine carcinosarcoma, VEGF-A mRNA was more strongly expressed in the carcinoma cells than in the sarcoma cells. In addition, a decrease in the VEGF-A mRNA expression was found in the transitional areas between carcinomatous and sarcomatous elements in most carcinosarcomas evaluated. Moreover, the Ang-2 mRNA expression was significantly seen in the vasculature adjacent to the periphery of the carcinoma cells in most carcinosarcomas, in comparison to that of endometrial carcinomas.

CONCLUSIONS

A high angiogenic activity in uterine carcinosarcoma was shown, in comparison to that of endometrial carcinoma. Tumor angiogenesis in uterine carcinosarcoma might be chiefly influenced by VEGF-A in the carcinoma cells, in cooperation with Ang-2 in the surrounding microvessels, however, this is not fully usually the case in sarcoma cells.

Expression of angiogenesis factors in human umbilical vein endothelial cells and their regulation by PEDF

The VEGFs and FGF-2 stimulate angiogenesis. Pigment epithelium-derived factor (PEDF) and thrombospondin-1 (TSP-1) strongly inhibit angiogenesis. Human umbilical vein endothelial cells (HUVECs) expressed VEGF-A, -B, -C, the VEGF receptors R1, R2, and R3, PEDF, FGF-2, and TSP-1, but VEGF-D transcripts were barely detectable. Hypoxia reduced the transcript levels of VEGF-C and its cognate receptor, VEGF-R3. PEDF blocked the effect of CoCl(2) on these two factors. The expression of VEGF-A and -B as well as VEGF-R1 and VEGF-R2 remained unchanged after exposure to hypoxia, PEDF, or both. There was a marked reduction in TSP-1 transcripts in CoCl(2) treated cultures and PEDF blocked this reduction. PEDF induced a small increase in FGF-2 transcripts in HUVECs, but there was no change in FGF-2 expression in HUVECs exposed to hypoxia or hypoxia plus PEDF. PEDF may control neovascularization, in part, by restoring the negative effects of hypoxia on the expression of a potent angiogenesis inhibitor, TSP-1. PEDF may also modulate vascular leakage by maintaining the transcriptional levels of the vascular homeostasis factors, VEGF-C and VEGF-R3 in hypoxic conditions.

Vascular endothelial growth factor A (VEGF-A) is involved in guidance of VEGF receptor-positive cells to the anterior portion of early embryos

The hemangioblast in the mesoderm gives rise to both angioblasts and hematopoietic stem cells. The movement of hemangioblast precursor cells in the fetal trunk is a critical event in early embryogenesis. Vascular endothelial growth factor (VEGF) signaling is likely involved in this migration given the partial disturbance of VEGF receptor (VEGFR)-positive cell accumulation and migration in VEGFR2 null mice or mice with a truncated VEGFR1. However, it is not clear how the VEGF system regulates this migration or its direction. We show here that the expression of VEGF-A is dominant in the anterior portion of the embryo, whereas VEGFR1 and VEGFR2 are expressed in the posterior portion of the embryo. An inhibitor of VEGFR kinase blocked the migration of VEGFR-positive cells in a whole-embryo culture system. In addition, VEGFR-positive cells migrated toward a VEGFR1- or VEGFR2-specific ligand in vitro. Furthermore, VEGFR-positive cells derived from wild-type or VEGFR2(+/-) mice moved rapidly anteriorly, whereas cells derived from VEGFR2(+/-) mice carrying a truncated VEGFR1 [VEGFR1(TM-TK)(-/-)] migrated little when injected into wild-type mice. These results suggest that the VEGF-A protein concentrated in the anterior region plays an important role in the guidance of VEGFR-positive cells from the posterior portion to the head region by interacting with VEGFR in the mouse embryo.

Lymphangiogenic growth factors as markers of tumor metastasis

Understanding the complex process of tumor metastasis is a problem which has challenged both clinician and scientist for well over 100 years. Defining molecular markers which reflect the metastatic potential of a tumor has also proved elusive. Recently, members of the vascular endothelial growth factor (VEGF) family of glycoproteins have been demonstrated to be potent mediators of both blood vessel and lymphatic vessel formation in the context of tumor biology. Experimental studies in animal models combined with extensive clinicopathological data provide a compelling case indicating that members of the VEGF family play a key role in the formation of metastases in a broad range of solid tumors. The question of whether VEGF signaling pathways can now serve as therapeutic targets alone, or in combination with other forms of anti-cancer agents, needs to be addressed.