Clinical applications of angiogenic growth factors and their inhibitors

Mechanisms of resistance to vascular endothelial growth factor blockade

Angiogenesis is essential for the growth of primary tumors and for their metastasis. This process is induced by factors, such as vascular endothelial growth factors (VEGFs), that bind to transmembrane VEGF receptors (VEGFRs). VEGF-A is the primary factor involved with angiogenesis; it binds to both VEGFR-1 and VEGFR-2. The inhibition of angiogenesis by obstructing VEGF-A signaling has been investigated as a method to treat solid tumors, but the development of resistance to this blockade has complicated treatment. The major mechanisms of this resistance to VEGF-A blockade include signaling by redundant receptors, such as the fibroblast growth factors, angiopoietin-1, ephrins, and other forms of VEGF. Other major mechanisms of resistance are increased metastasis of hypoxia-resistant tumor cells, recruitment of cell types capable of promoting VEGF-independent angiogenesis, and increased circulation of nontumor proangiogenic factors. Additional mechanisms of resistance to VEGF-A blockade include heterogeneity of responsiveness among tumor cells, use of anti-VEGF-A agents at insufficient doses or for insufficient duration, altered sensitivity to anti-VEGF-A agents by mutations in endothelial cells or vascular remodeling, maintenance of vascular sleeves that allow for easy regrowth of tumor vasculature upon discontinuation of therapy, vascular cooption, and intussusceptive angiogenesis. An understanding of these mechanisms may lead to the development of targeted therapies that overcome this resistance. Some of these approaches include the combined inhibition of redundant angiogenic pathways, proper patient selection for various therapies based on gene expression profiles, blockade of cellular migration by inhibition of colony-stimulating factor, or the use of agents to disrupt vascular architecture.

Controlled release of thymosin β4 using collagen-chitosan composite hydrogels promotes epicardial cell migration and angiogenesis

Rapid vascularization at the infarcted site is crucial for cardiac repair following myocardial infarction. Thymosin β4 (Tβ4), a 43-amino acid peptide, is both angiogenic and cardioprotective. Tβ4 in soluble form was previously shown to promote cell migration from quiescent adult cardiac explants. Here we developed a collagen-chitosan hydrogel for the encapsulation of Tβ4, which allowed its controlled release over 28days to elicit localized and prolonged effects. Contrastingly, Tβ4 was fully released over 3days when encapsulated in collagen-only hydrogels due to charge repulsion and lack of interconnected pores as shown by SEM. The charge of encapsulated molecules affected their release from collagen-chitosan hydrogels. While the release of neutral polyalanine was size-controlled diffusion, that of negatively-charged Tβ4 and positively-charged polylysine was affected by electrostatic interactions of peptides with collagen/chitosan molecules. Hydrogels with encapsulated Tβ4 significantly increased cell migration and outgrowth of CD31-positive capillaries from mouse and rat epicardial explants in vitro, compared to Tβ4-free and soluble controls. Potential advantage of Tβ4 over commonly-used angiogenic growth factors is that it can induce recruitment and differentiation of both endothelial and smooth muscle cells necessary for vascular stability. Importantly, Tβ4-encapsulated collagen-chitosan hydrogels promoted angiogenesis in vivo upon subcutaneous injection, compared to collagen-only hydrogels.

Molecular pathways of lymphangiogenesis and lymph node metastasis in head and neck cancer

Metastasis to regional lymph nodes constitutes the main route toward progression and dissemination of head and neck carcinoma; at the same time it is the most significant adverse prognostic indicator for this disease. In recent years, significant focus has been given on the molecular mechanisms behind lymph node metastasis of head and neck cancer. The aim of this study is to assess the role of growth factor expression and function in association with lymph node metastasis and overall prognosis of head and neck cancer. Current literature, searching for experimental data regarding the molecular pathways of lymph node dissemination of head and neck cancer, is reviewed giving special emphasis on the expression and prognostic significance of specific growth factors. Members of the vascular endothelial growth factor (VEGF), mostly VEGF-C and VEGF-D, with their action through the receptors VEGFR-3 and VEGFR-2, constitute the most extensively studied growth factors associated with lymphangiogenesis so far. High expression of these as well as other molecules, including angiopoietins, insulin-like growth factor, and fibroblast growth factor, has been associated with lymph node metastasis and poor prognosis in head and neck squamous cell carcinoma. Numerous growth factors seem to play an important role regarding the lymph node metastatic potential of head and neck cancer. Further research is necessary in order to further clarify the molecular pathways and introduce novel therapeutic options.

Critical roles of cold shock domain protein A as an endogenous angiogenesis inhibitor in skeletal muscle

Angiogenesis is regulated by the local balance between angiogenic stimulators and inhibitors and is maintained by muscle-derived angiogenic factors in ischemic tissues.

AIMS

Our objectives were to investigate the effect of cold shock domain protein A (CSDA) as an endogenous angiogenesis inhibitor and to develop a novel strategy of therapeutic angiogenesis by blocking CSDA expression.

RESULTS

In human skeletal muscle cells, CSDA was upregulated during hypoxia when cells were damaged and apoptosis was induced. CSDA expression could repress the activity of hypoxia inducible factor-1α and nuclear factor κB, because CSDA can competitively bind the hypoxia response element and the nuclear factor κB-binding element. As a result, vascular endothelial growth factor-A, interleukin-6, and interleukin-8 secretions from skeletal muscle cells were decreased. Further, CSDA depletion increased the secretion level of these angiogenic factors. In a hindlimb ischemia model, transfer of short-hairpin RNA targeting CSDA ameliorated ischemia without direct transfer of angiogenic factors. In this ischemic tissue, vascular endothelial growth factor-A, interleukin-6, and CXCL2 protein levels were increased.

INNOVATION AND CONCLUSION

CSDA appears to play a critical role as an endogenous angiogenesis inhibitor in skeletal muscle, and RNA interference targeting of CSDA is a promising gene therapy strategy for treating peripheral arterial disease.

Importance of vascular endothelial growth factor (VEGF) in ovarian physiology of mammals

Ovarian folliculogenesis in mammals is a complex process. Several compounds have been tested during in vitro culture of follicular cells for a better understanding of the mechanisms and factors related to ovarian folliculogenesis in mammals. From these compounds, vascular endothelial growth factor (VEGF) can be highlighted, as it is strongly associated with angiogenesis and, in recent years, its presence in ovarian cells has been investigated extensively. Previous studies have shown that the presence of VEGF protein, as well as mRNA expression of its receptor 2 (VEGFR-2) increases during follicular development. Therefore, it is likely that the interaction between VEGF and VEGFR-2 is crucial to promote follicular development. However, few studies on the influence of this factor on follicular development have been reported. This review addresses aspects related to the structural characterization and mechanism of action of VEGF and its receptors, and their biological importance in the ovary of mammals.

Targeted nanoparticle enhanced proapoptotic peptide as potential therapy for glioblastoma

Antiangiogenic therapy can produce transient tumor regression in glioblastoma (GBM), but no prolongation in patient survival has been achieved. We have constructed a nanosystem targeted to tumor vasculature that incorporates three elements: (i) a tumor-homing peptide that specifically delivers its payload to the mitochondria of tumor endothelial cells and tumor cells, (ii) conjugation of this homing peptide with a proapoptotic peptide that acts on mitochondria, and (iii) multivalent presentation on iron oxide nanoparticles, which enhances the proapoptotic activity. The iron oxide component of the nanoparticles enabled imaging of GBM tumors in mice. Systemic treatment of GBM-bearing mice with the nanoparticles eradicated most tumors in one GBM mouse model and significantly delayed tumor development in another. Coinjecting the nanoparticles with a tumor-penetrating peptide further enhanced the therapeutic effect. Both models used have proven completely resistant to other therapies, suggesting clinical potential of our nanosystem.

12/15-Lipoxygenase gene knockout severely impairs ischemia-induced angiogenesis due to lack of Rac1 farnesylation

To understand the mechanisms by which 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) activates Rac1 in the induction of angiogenesis, we studied the role of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and αPix. 15(S)-HETE stimulated Rac1 in a sustained manner in human dermal microvascular endothelial cells (HDMVECs). Simvastatin, a potent inhibitor of HMG-CoA reductase, suppressed 15(S)-HETE-induced Rac1 activation in HDMVECs affecting their migration and tube formation. 15(S)-HETE by inducing HMG-CoA reductase expression caused increased farnesylation and membrane translocation of Rac1 where it became activated by Src-dependent αPix stimulation. Mevalonate rescued 15(S)-HETE-induced Rac1 farnesylation and membrane translocation in HDMVECs and the migration and tube formation of these cells from inhibition by simvastatin. Down-regulation of αPix inhibited 15(S)-HETE-induced HDMVEC migration and tube formation. Hind-limb ischemia induced Rac1 farnesylation and activation leading to increased angiogenesis and these effects were blocked by simvastatin and rescued by mevalonate in WT mice. In contrast, hind-limb ischemia failed to induce Rac1 farnesylation and activation as well as angiogenic response in 12/15-Lox(-/-) mice. Activation of Src and αPix were also compromised at least to some extent in 12/15-Lox(-/-) mice compared with WT mice in response to hind-limb ischemia. Together, these findings demonstrate for the first time that HMG-CoA reductase plays a determinant role in 12/15-Lox-induced angiogenesis.

Mechanisms Conferring Resistance to Pro-Apoptotic Cancer Gene Therapy

Recently, we have described a novel approach to the treatment of cancer that employs a series of vectors that encode surface expressed chimeric proteins in which the cytoplasmic death domain of Fas is fused in-frame to the extracellular domain of one of a number of cell surface receptors that recognize and bind various ligands that are differentially expressed within the tumor microenvironment. Although the majority of tumor cells transduced with such vectors are killed in the presence of the corresponding cognate ligand, a small percentage survive and in vivo may go on to repopulate a treated tumor. In order to understand the mechanisms employed by tumors to escape the cytotoxic effects of pro-apoptotic signals triggered via Fas, we isolated a large number of 293 tumor cell clones that survive following transfection with a plasmid vector encoding Flk-1/Fas, a chimeric receptor that induces tumor cell death in the presence of the pro-angiogenic cytokine VEGF. Characterization of Flk-1/Fas-positive clones revealed that while survival can most often be attributed simply to the down-regulation of VEGF ligand expression, in cells that express both receptor and ligand, other proteins involved in the regulation of apoptosis may be targeted. Specifically, a Flk-1/Fas-positive, VEGF-positive clone was identified in which expression of APAF-1 was almost completely abrogated.

An integrated mathematical model of thrombin-, histamine-and VEGF-mediated signalling in endothelial permeability

BACKGROUND

Endothelial permeability is involved in injury, inflammation, diabetes and cancer. It is partly regulated by the thrombin-, histamine-, and VEGF-mediated myosin-light-chain (MLC) activation pathways. While these pathways have been investigated, questions such as temporal effects and the dynamics of multi-mediator regulation remain to be fully studied. Mathematical modeling of these pathways facilitates such studies. Based on the published ordinary differential equation models of the pathway components, we developed an integrated model of thrombin-, histamine-, and VEGF-mediated MLC activation pathways.

RESULTS

Our model was validated against experimental data for calcium release and thrombin-, histamine-, and VEGF-mediated MLC activation. The simulated effects of PAR-1, Rho GTPase, ROCK, VEGF and VEGFR2 over-expression on MLC activation, and the collective modulation by thrombin and histamine are consistent with experimental findings. Our model was used to predict enhanced MLC activation by CPI-17 over-expression and by synergistic action of thrombin and VEGF at low mediator levels. These may have impact in endothelial permeability and metastasis in cancer patients with blood coagulation.

CONCLUSION

Our model was validated against a number of experimental findings and the observed synergistic effects of low concentrations of thrombin and histamine in mediating the activation of MLC. It can be used to predict the effects of altered pathway components, collective actions of multiple mediators and the potential impact to various diseases. Similar to the published models of other pathways, our model can potentially be used to identify important disease genes through sensitivity analysis of signalling components.

Novel therapies targeting endometriosis

Endometriosis is an often painful disorder in which the endometrial glands and stroma grow outside the uterus. The disease affects women's quality of life and is a common cause of infertility. In this review, we describe promising new developments in the field based on in vitro assays and rodent models, each of which has the potential to be beneficial in the treatment of this disease. We will specifically describe the role of anti-inflammatory drugs, selective estrogen, or progesterone modulators, statins, antiangiogenic agents, and the potential for targeting stem cells as likely methods to hone in and eliminate endometriosis. The most promising of these potential therapies are currently slated for further testing in both rodent and nonhuman primate trials.

Comparison of angiotensin converting enzyme inhibitors and angiotensin II type 1 receptor blockade for the prevention of premalignant changes in the liver

AIM

We investigate and compare the possible antitumor activity of clinically used angiotensin converting enzyme (ACE) inhibitors; captopril, perindopril and angiotensin II type 1 receptor (AT1R) blocker, losartan against hepatocarcinogenesis initiated by diethylnitrosoamines (DENA) and promoted by carbon tetrachloride (CCl(4)).

MAIN METHODS

Diethylnitrosamine (DENA) (200mg/kgi.p.) initiated and carbon tetrachloride (CCl(4)) (2ml/kgi.p.) promoted hepatocarcinogenesis in male Wistar rats after 8weeks.

RESULTS

Hepatocarcinogenesis was manifested biochemically by elevation of serum hepatic tumor markers tested; α-feto protein (AFP) and carcinoembryonic antigen (CEA). In addition, hepatic carcinogenesis was further confirmed by a significant increase in hepatic tissue growth factors; vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF). Moreover a marked increase in matrix metalloproteinase-2 and hydroxyproline content were also observed. Hepatocarcinogenesis was further confirmed by a significant decrease in hepatic endostatin and metallothonein level.

KEY FINDINGS

Long-term administration of the selected drugs for 2weeks before and throughout the experimental period produced a significant protection against hepatic carcinogenesis. The present results claimed that different doses of the selected drugs succeeded in normalization of serum tumor markers. Furthermore, the drugs reduced the elevated level in the hepatic growth factors, matrix metalloproteinase-2 and hydroxyproline induced by the hepatocarcinogen. Moreover, the amelioration was also accompanied by augmentation of hepatic content of metallothionein and endostatin. Histopathological examination of liver tissues of rats treated with DENA-CCl(4) correlated with the biochemical observations.

SIGNIFICANCE

These findings suggest a similar protective effect of ACE inhibitors; captopril; perindopril and AT1R blocker, losartan against premalignant stages of liver cancer in the DENA initiated and CCl(4) promoted hepatocarcinogenesis model in rats. Therefore, RAS especially angiotensin II (Ang II) and AT1R interaction plays a pivotal role hepatocarcinogenesis development.

Vascular endothelial growth factor and fibroblast growth factor 2 delivery from spinal cord bridges to enhance angiogenesis following injury

The host response to spinal cord injury can lead to an ischemic environment that can induce cell death and limits cell transplantation approaches to promote spinal cord regeneration. Spinal cord bridges that provide a localized and sustained release of vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF-2) were investigated for their ability to promote angiogenesis and nerve growth within the injury. Bridges were fabricated by fusion of poly(lactide-co-glycolide) microspheres using a gas foaming/particulate leaching technique, and proteins were incorporated by encapsulation into the microspheres and/or mixing with the microspheres before foaming. Compared to the mixing method, encapsulation reduced the losses during leaching and had a slower protein release, while VEGF was released more rapidly than FGF-2. In vivo implantation of bridges loaded with VEGF enhanced the levels of VEGF within the injury at 1 week, and bridges releasing VEGF and FGF-2 increased the infiltration of endothelial cells and the formation of blood vessel at 6 weeks postimplantation. Additionally, substantial neurofilament staining was observed within the bridge; however, no significant difference was observed between bridges with or without protein. Bridges releasing angiogenic factors may provide an approach to overcome an ischemic environment that limits regeneration and cell transplantation-based approaches.

Impaired expression of uncoupling protein 2 causes defective postischemic angiogenesis in mice deficient in AMP-activated protein kinase α subunits

OBJECTIVE

The aim of the present study was to determine whether mitochondrial uncoupling protein (UCP) 2 is required for AMPK-dependent angiogenesis in ischemia in vivo.

METHODS AND RESULTS

Angiogenesis was assayed by monitoring endothelial tube formation (a surrogate for angiogenesis) in human umbilical vein endothelial cells (ECs), isolated mouse aortic endothelial cells (MAECs), and pulmonary microvascular endothelial cells or in ischemic thigh adductor muscles from wild-type (WT) mice or mice deficient in either AMPKα1 or AMPKα2. AMPK inhibition with pharmacological inhibitor (compound C) or genetic means (transfection of AMPKα-specific small interfering RNA) significantly lowered the tube formation in human umbilical vein ECs. Consistently, compared with WT mice, tube formation in MAECs isolated from either AMPKα1(-/-) or AMPKα2(-/-) mice, which exhibited oxidative stress and reduced expression of UCP2, was significantly impaired. In addition, adenoviral overexpression of UCP2, but not adenoviruses encoding green fluorescent protein, normalized tube formation in MAECs from either AMPKα1(-/-) or AMPKα2(-/-) mice. Similarly, supplementation with sodium nitroprusside, a nitric oxide (NO) donor, restored tube formation. Furthermore, ischemia significantly increased angiogenesis, serine 1177 phosphorylation of endothelial NO synthase, and UCP2 in ischemic thigh adductor muscles from WT mice but not in those from either AMPKα1(-/-) or AMPKα2(-/-) mice.

CONCLUSIONS

We conclude that AMPK-dependent UCP2 expression in ECs promotes angiogenesis in vivo.

Adeno associated viral vector-delivered and hypoxia response element-regulated CD151 expression in ischemic rat heart

AIM

The aim of this study was to improve the delivery efficacy and target specificity of the pro-angiogenic gene CD151 to the ischemic heart.

METHODS

To achieve the inducible expression of adeno-associated viral (AAV)-delivered CD151 gene in only the ischemic myocardium, we generated an AAV construct in which CD151 expression can be controlled by the hypoxia response element (HRE) sequence from the human Enolase gene. The function of this vector was examined in rat H9C2 cardiac myoblasts and in ischemic rat myocardium. The expression of CD151 in the areas of ischemic myocardium was confirmed at the mRNA level by real-time PCR and on the protein level by Western blot, whereas the CD151 expression in the microvessels within the areas of ischemic myocardium was detected by immunohistochemistry.

RESULTS

HRE significantly enhances the expression of CD151 under hypoxic conditions or in the ischemic myocardium, and forced CD151 expression increases the number of microvessels in the ischemic myocardium.

CONCLUSION

The AAV-mediated, HRE regulated delivery of the CD151 gene shows higher expression in the ischemic myocardium and more efficiently targets CD151 to the hypoxic regions after myocardial infarction.

Grb-2-associated binder 1 (Gab1) regulates postnatal ischemic and VEGF-induced angiogenesis through the protein kinase A-endothelial NOS pathway

The intracellular signaling mechanisms underlying postnatal angiogenesis are incompletely understood. Herein we show that Grb-2-associated binder 1 (Gab1) plays a critical role in ischemic and VEGF-induced angiogenesis. Endothelium-specific Gab1 KO (EGKO) mice displayed impaired angiogenesis in the ischemic hindlimb despite normal induction of VEGF expression. Matrigel plugs with VEGF implanted in EGKO mice induced fewer capillaries than those in control mice. The vessels and endothelial cells (ECs) derived from EGKO mice were defective in vascular sprouting and tube formation induced by VEGF. Biochemical analyses revealed a substantial reduction of endothelial NOS (eNOS) activation in Gab1-deficient vessels and ECs following VEGF stimulation. Interestingly, the phosphorylation of Akt, an enzyme known to promote VEGF-induced eNOS activation, was increased in Gab1-deficient vessels and ECs whereas protein kinase A (PKA) activity was significantly decreased. Introduction of an active form of PKA rescued VEGF-induced eNOS activation and tube formation in EGKO ECs. Reexpression of WT or mutant Gab1 molecules in EGKO ECs revealed requirement of Gab1/Shp2 association for the activation of PKA and eNOS. Taken together, these results identify Gab1 as a critical upstream signaling component in VEGF-induced eNOS activation and tube formation, which is dependent on PKA. Of note, this pathway is conserved in primary human ECs for VEGF-induced eNOS activation and tube formation, suggesting considerable potential in treatment of human ischemic diseases.

Stereoselective synthesis of four possible isomers of streptopyrrolidine

The synthesis of (4R,5R)-streptopyrrolidine (1), (4S,5R)-streptopyrrolidine (2) (4R,5S)-streptopyrrolidine (3) and (4S,5S)-streptopyrrolidine (4) have been achieved in a concise and highly efficient manner via a highly stereoselective aldol type reaction with the trimethylsilyl enolate of ethyl acetate and Lewis acid mediated lactamization as the key reactions in ≈42% yield over six steps starting from D-phenylalanine and L-phenylalanine, respectively. The absolute configuration of the natural product was shown to be (4S,5S) by comparing its spectral and analytical data with the reported values.

Angiogenesis assays

The angiogenic process is central in the pathogenesis of various diseases. The in vitro and in vivo monitoring of the neovascular process is essential for the development and evaluation of angiogenesis inhibitors or stimulators. Since no single method exists that can assess angiogenesis in a robust, reliable, and reproducible fashion, researchers often use a combination of assays to circumvent this problem. The experimental details of the most commonly in vitro, ex vivo, and in vivo assays are presented here.

Antiangiogenic therapies in early-stage breast cancer

Angiogenesis, which is crucial for the growth and spread of cancer cells, has become an important target for antineoplastic therapies in a variety of malignant tumors. Vascular endothelial growth factor and its receptor promote formation of new blood vessels in tumors. Several drugs, most notably the monoclonal antibody bevacizumab, have been developed to inhibit this process. Clinical trials utilizing bevacizumab and other antiangiogenic drugs in metastatic breast cancer have demonstrated enhanced response rates and prolonged progression-free survival, though no overall survival benefit has been seen. Trials are now under way exploring the use of antiangiogenic agents in patients with early stage breast cancer. We performed a comprehensive review of the published literature (English language), US National Institutes of Health clinical trials registry (ClinicalTrials.gov), and established cooperative groups that revealed approximately 75 clinical trials, completed or ongoing, utilizing antiangiogenic drugs in early-stage breast cancer. A number of phase II trials in the neoadjuvant setting have reported preliminary results suggesting response rates similar to those seen with traditional anthracycline-plus-taxane combination regimens. Most of these early trials have not yet met any survival endpoints. Studies are also ongoing in the adjuvant setting, and these have not yet been reported. The toxicities associated with these agents are similar to those that have been reported in the metastatic trials. Most of these side effects are grade 1 or 2 and are easily manageable; however, there remain a small percentage of patients who sustain life-threatening vascular events, bleeding, or wound-healing complications. This number is significantly higher in patients receiving antiangiogenic drugs when compared with controls. While we eagerly await completion and results of this impressive portfolio of studies in early breast cancer with antiangiogenic agents, there is an urgent need for a more rational patient/antiangiogenic therapy selection with greater insight into predictive factors for toxicities, therapy efficacy, and clinical benefit.

Nanoparticle-induced vascular blockade in human prostate cancer

The tumor-homing pentapeptide CREKA (Cys-Arg-Glu-Lys-Ala) specifically homes to tumors by binding to fibrin and fibrin-associated clotted plasma proteins in tumor vessels. Previous results show that CREKA-coated superparamagnetic iron oxide particles can cause additional clotting in tumor vessels, which creates more binding sites for the peptide. We have used this self-amplifying homing system to develop theranostic nanoparticles that simultaneously serve as an imaging agent and inhibit tumor growth by obstructing tumor circulation through blood clotting. The CREKA nanoparticles were combined with nanoparticles coated with another tumor-homing peptide, CRKDKC, and nanoparticles with an elongated shape (nanoworms) were used for improved binding efficacy. The efficacy of the CREKA peptide was then increased by replacing some residues with nonproteinogenic counterparts, which increased the stability of the peptide in the circulation. Treatment of mice bearing orthotopic human prostate cancer tumors with the targeted nanoworms caused extensive clotting in tumor vessels, whereas no clotting was observed in the vessels of normal tissues. Optical and magnetic resonance imaging confirmed tumor-specific targeting of the nanoworms, and ultrasound imaging showed reduced blood flow in tumor vessels. Treatment of mice with prostate cancer with multiple doses of the nanoworms induced tumor necrosis and a highly significant reduction in tumor growth.

Gene therapy using genetically modified lymphocytes targeting VEGFR-2 inhibits the growth of vascularized syngenic tumors in mice

Immunotherapies based on adoptive cell transfer are highly effective in the treatment of metastatic melanoma, but the use of this approach in other cancer histologies has been hampered by the identification of appropriate target molecules. Immunologic approaches targeting tumor vasculature provide a means for the therapy of multiple solid tumor types. We developed a method to target tumor vasculature, using genetically redirected syngeneic or autologous T cells. Mouse and human T cells were engineered to express a chimeric antigen receptor (CAR) targeted against VEGFR-2, which is overexpressed in tumor vasculature and is responsible for VEGF-mediated tumor progression and metastasis. Mouse and human T cells expressing the relevant VEGFR-2 CARs mediated specific immune responses against VEGFR-2 protein as well as VEGFR-2-expressing cells in vitro. A single dose of VEGFR-2 CAR-engineered mouse T cells plus exogenous IL-2 significantly inhibited the growth of 5 different types of established, vascularized syngeneic tumors in 2 different strains of mice and prolonged the survival of mice. T cells transduced with VEGFR-2 CAR showed durable and increased tumor infiltration, correlating with their antitumor effect. This approach provides a potential method for the gene therapy of a variety of human cancers.

Expression of genes involved in rat liver angiogenesis after ischaemia and reperfusion: effects of ischaemic pre- and post-conditioning

BACKGROUND

During surgery, ischaemic pre- (IPC) and post-conditioning (IPO) protects the liver against ischaemia/reperfusion injuries (I/R-injuries). The impact of ischaemic conditioning on liver regeneration has been less well studied. Angiogenesis is an important part of liver regeneration after hepatectomy. The aim of the present study was to investigate the effect of ischaemia/reperfusion and ischaemic conditioning on the expression of genes with angiogenic potential in a model of rat liver ischaemia.

METHODS

A model of total liver ischaemia (30 min) and reperfusion (30 min) was employed using Wistar rats. Rats were randomized into five groups: (C) control (IRI) ischaemic, IPC, IPO and IPC + IPO. Liver enzymes were sampled at the end of reperfusion. Liver biopsies were analysed using cDNA microarrays.

RESULTS

Alanine aminotransferase (ALT) increased significantly in all the ischaemic groups compared with controls (P= 0.000). Searching databases 99 genes involved in rat liver angiogenesis were identified. Compared with group (C) the number of genes significantly up-regulated was as follows: IRI (n= 5), IPC (n= 24), IPO (n= 33) and IPC + IPO (n= 18). No genes were down-regulated in the four groups compared with controls.

CONCLUSION

Ischaemic conditioning, as demonstrated in the present study, seems to be potent activators of angiogenic genes. This might be favourable to the regenerating liver.

Nasal septum perforation: a side effect of bevacizumab chemotherapy in breast cancer patients

BACKGROUND

Bevacizumab is an anti-vascular endothelial growth factor approved in association with paclitaxel or docetaxel as first line in patients (pts) with metastatic breast cancer. Rare cases of nasal septum perforations have been reported. We report our experience of nasal perforation in breast cancer pts receiving bevacizumab and chemotherapy either in the adjuvant or in the metastatic settings.

METHODS

Between 1 January and 31 December 2009, 70 pts received bevacizumab together with chemotherapy. All the pts who had received bevacizumab were referred to the ENT specialist. Symptoms potentially related were looked for. Side effects were graded according to CTCAE.

RESULTS

Five nasal septum perforations were diagnosed (5 out of 70; 7.14%). Bevacizumab dose was 15 mg kg(-1) 3 weekly. Three pts were metastatic. Bevacizumab was associated with docetaxel (100 mg m(-2) every 3 weeks) in two pts and with weekly paclitaxel in one. The last two pts received bevacizumab in combination with anthracyclin and then taxanes in the adjuvant setting. In these two cases, nasal septum perforation occurred at the time of docetaxel treatment.

CONCLUSION

A high incidence of nasal septum perforation has been shown in pts with breast cancer receiving bevacizumab together with chemotherapy. Several mechanisms could be involved (mucositis, delayed tissue repair, antiangiogenic action of taxanes).

Current status of vascular endothelial growth factor inhibition in age-related macular degeneration

Angiogenesis, the process by which new vessels are created from pre-existing vasculature, has become the subject of intense research in recent years. Increased rates of angiogenesis are associated with several disease states, including cancer, age-related macular degeneration (AMD), psoriasis, rheumatoid arthritis, and diabetic retinopathy. Vascular endothelial growth factor (VEGF) is an important modulator of angiogenesis, and has been implicated in the pathology of a number of conditions, including AMD, diabetic retinopathy, and cancer. AMD is a progressive disease of the macula and the third major cause of blindness worldwide. If not treated appropriately, AMD can progress to involve both eyes. Until recently, the treatment options for AMD have been limited, with photodynamic therapy (PDT) the mainstay of treatment. Although PDT is effective at slowing disease progression, it rarely results in improved vision. Several therapies have been or are now being developed for neovascular AMD, with the goal of inhibiting VEGF. These VEGF inhibitors include the RNA aptamer pegaptanib, partial and full-length antibodies ranibizumab and bevacizumab, the VEGF receptor decoy aflibercept, small interfering RNA-based therapies bevasiranib and AGN 211745, sirolimus, and tyrosine kinase inhibitors, including vatalanib, pazopanib, TG 100801, TG 101095, AG 013958, and AL 39324. At present, established therapies have met with great success in reducing the vision loss associated with neovascular AMD, whereas those still under investigation offer the potential for further advances. In AMD patients, these therapies slow the rate of vision loss and in some cases increase visual acuity. Although VEGF-inhibitor therapies are a milestone in the treatment of these disease states, several concerns need to be addressed before their impact can be fully realized.

Tumor microvasculature and microenvironment: novel insights through intravital imaging in pre-clinical models

Intravital imaging techniques have provided unprecedented insight into tumor microcirculation and microenvironment. For example, these techniques allowed quantitative evaluations of tumor blood vasculature to uncover its abnormal organization, structure and function (e.g., hyper-permeability, heterogeneous and compromised blood flow). Similarly, imaging of functional lymphatics has documented their absence inside tumors. These abnormalities result in elevated interstitial fluid pressure and hinder the delivery of therapeutic agents to tumors. In addition, they induce a hostile microenvironment characterized by hypoxia and acidosis, as documented by intravital imaging. The abnormal microenvironment further lowers the effectiveness of anti-tumor treatments such as radiation therapy and chemotherapy. In addition to these mechanistic insights, intravital imaging may also offer new opportunities to improve therapy. For example, tumor angiogenesis results in immature, dysfunctional vessels--primarily caused by an imbalance in production of pro- and anti-angiogenic factors by the tumors. Restoring the balance of pro- and anti-angiogenic signaling in tumors can "normalize" tumor vasculature and thus, improve its function, as demonstrated by intravital imaging studies in preclinical models and in cancer patients. Administration of cytotoxic therapy during periods of vascular normalization has the potential to enhance treatment efficacy.

Advances in polymeric micelles for drug delivery and tumor targeting

A plethora of formulation techniques have been reported in the literature for targeting drugs to specific sites. Polymeric micelles (PMs) can be targeted to tumor sites by passive as well as active mechanisms. Some inherent properties of PMs, including size in the nanorange, stability in plasma, longevity in vivo, and pathological characteristics of tumor allow PMs to be targeted to the tumor site by a passive mechanism called the enhanced permeability and retention effect. PMs formed from an amphiphilic block copolymer are suitable for encapsulation of poorly water-soluble, hydrophobic anticancer drugs. Other characteristics of PMs such as separate functionality at the outer shell are useful for targeting the anticancer drug to tumor by active mechanisms. PMs can be conjugated with many ligands such as antibody fragments, epidermal growth factors, α(2)-glycoprotein, transferrin, and folate to target micelles to cancer cells. Application of heat or ultrasound are the alternative methods to enhance drug accumulation in tumoral cells. Targeting using micelles can also be directed toward tumor angiogenesis, which is a potentially promising target for anticancer drugs. PMs have been used for the delivery of many anticancer agents in preclinical and clinical studies. This review summarizes recently available information regarding targeting of anticancer drugs to the tumor site using PMs.

Effect of vascular endothelial growth factor and its receptor KDR on the transendothelial migration and local trafficking of human T cells in vitro and in vivo

In these studies, we find that the vascular endothelial growth factor (VEGF) receptor KDR is expressed on subsets of mitogen-activated CD4(+) and CD8(+) T cells in vitro. We also found that KDR colocalizes with CD3 on mitogen-activated T cells in vitro and on infiltrates within rejecting human allografts in vivo. To evaluate whether VEGF and KDR mediate lymphocyte migration across endothelial cells (ECs), we used an in vitro live-time transmigration model and observed that both anti-VEGF and anti-KDR antibodies inhibit the transmigration of both CD4(+) and CD8(+) T cells across tumor necrosis factor α (TNFα)-activated, but not unactivated ECs. In addition, we found that interactions among CD4(+) or CD8(+) T cells and TNFα-activated ECs result in the induction of KDR on each T cell subset, and that KDR-expressing lymphocytes preferentially transmigrate across TNFα-activated ECs. Finally, using a humanized severe combined immunodeficient mouse model of lymphocyte trafficking, we found that KDR-expressing lymphocytes migrate into human skin in vivo, and that migration is reduced in mice treated with a blocking anti-VEGF antibody. These observations demonstrate that induced expression of KDR on subsets of T cells, and locally expressed VEGF, facilitate EC-dependent lymphocyte chemotaxis, and thus, the localization of T cells at sites of inflammation.

Long-term blood vessel removal with combined laser and topical rapamycin antiangiogenic therapy: implications for effective port wine stain treatment

BACKGROUND AND OBJECTIVES

Complete blanching of port wine stain (PWS) birthmarks after laser therapy is rarely achieved for most patients. We postulate that the low therapeutic efficacy or treatment failure is caused by regeneration and revascularization of photocoagulated blood vessels due to angiogenesis associated with the skin's normal wound healing response. Rapamycin (RPM), an antiangiogenic agent, has been demonstrated to inhibit growth of pathological blood vessels. Our objectives were to (1) investigate whether topical RPM can inhibit reperfusion of photocoagulated blood vessels in an animal model and (2) determine the effective RPM concentration required to achieve this objective.

STUDY DESIGN/MATERIALS AND METHODS

For both laser-only and combined laser and RPM treated animals, blood vessels in the dorsal window chambers implanted on golden Syrian hamsters were photocoagulated with laser pulses. Structural and flow dynamics of blood vessels were documented with color digital photography and laser speckle imaging to evaluate photocoagulation and reperfusion. For the combined treatment group, topical RPM was applied to the epidermal side of the window daily for 14 days after laser exposure.

RESULTS

In the laser-only group, 23 out of 24 photocoagulated blood vessels reperfused within 5-14 days. In the combined treatment group with different RPM formulae and concentrations, the overall reperfusion rate of 36% was much lower as compared to the laser-only group. We also found that the reperfusion rate was not linearly proportional to the RPM concentration.

CONCLUSIONS

With topical RPM application, the frequency of vessel reperfusion was considerably reduced, which implies that combined light and topical antiangiogenic therapy might be a promising approach to improve the treatment efficacy of PWS birthmarks.

Polymorphisms in EGFR and VEGF contribute to non-small-cell lung cancer survival in a Chinese population

Over the last decades, combined chemotherapies that inhibit different signalling pathways together have been demonstrated to be more effective to treat the non-small-cell lung cancer (NSCLC). The epidermal growth factor receptor (EGFR) and the vascular endothelium growth factor (VEGF) are two key targets. Polymorphisms in EGFR and VEGF genes have been identified to be associated with therapy-response and cancer survival. In this study, we hypothesized that single-nucleotide polymorphisms (SNPs) of EGFR and VEGF genes are associated with NSCLC patients' survival in Chinese. Therefore, we screened and genotyped 54 potentially functional SNPs as well as tagging SNPs in these two genes using Illumina Golden Gate platform in 568 NSCLC patients. We found that subjects carrying EGFR rs3735061AA and rs6958497AG/GG genotypes survived significantly shorter time [median survival time (MST): 22.2 and 19.4 months, respectively] than those carrying rs3735061AG/GG (MST: 25.1 months) and rs6958497AA (MST: 25.9 months) (log-rank P = 0.015 for rs3735061 and log-rank P = 0.028 for rs6958497). However, subjects carrying EGFR rs759165AG/AA genotypes survived significantly longer (MST: 38.7 months) than those carrying rs759165GG genotype (MST: 24.7 months) (log-rank P = 0.024). Multivariate Cox regression analyses showed that the genotypes of rs3735061AA and rs6958497AG/GG were associated with a significantly increased risk of death for NSCLC [hazard ratio (HR) = 2.82, 95% confidence interval (CI) = 1.66-4.78 for rs3735061AA and HR = 1.69, 95% CI = 1.26-2.28 for rs6958497AG/GG], whereas the rs759165AG/AA were associated with a 44% significantly decreased risk of death of NSCLC (HR = 0.56, 95% CI = 0.39-0.83). Stepwise COX regression analyses suggested that EGFR rs373506, rs759165 and rs6958497 may be independent candidate biomarkers to predict NSCLC survival in this population.

Association of plasma VEGF-A, soluble VEGFR-1 and VEGFR-2 levels and clinical response and survival in advanced colorectal cancer patients receiving bevacizumab with modified FOLFOX6

For individualized bevacizumab-based therapy, non-invasive biomarkers are necessary. This study assessed the predictive value of plasma vascular endothelial growth factor (VEGF)-A, soluble VEGF receptor (sVEGFR)-1 and sVEGFR-2 levels as biomarkers for clinical response and survival in advanced colorectal cancer (CRC) patients treated with bevacizumab and modified FOLFOX6 (mFOLFOX6). Forty-six unresectable advanced CRC patients and 20 healthy controls were included in this study. CRC patients were treated with bevacizumab and mFOLFOX6. Pretreatment plasma VEGF-A, sVEGFR-1 and sVEGFR-2 levels were measured using the multiplex immunoassay. Plasma VEGF-A, sVEGFR-1 and sVEGFR-2 levels were significantly higher in CRC patients than in the healthy subjects. The plasma sVEGFR-1 levels in the responder patients [complete response (CR)/partial response (PR)] and stable disease (SD) patients were significantly lower than those in the progressive disease (PD) patients (CR/PR vs. PD, p=0.025; SD vs. PD, p=0.032), while the plasma VEGF-A and sVEGFR-2 levels did not show any significant differences between the two groups of patients. Patients with higher sVEGFR-1 levels showed a significantly poorer progression-free survival (PFS) and overall survival (OS) than those with lower VEGFR-1 levels. In contrast, VEGF-A and sVEGFR-2 did not show any significant relationship between PFS and OS according to the status of each level. In the multivariate Cox proportional hazard regression analysis, sVEGFR-1 levels showed a significant relationship between PFS and OS. These results suggest that plasma sVEGFR-1 levels have a predictive value for clinical response and survival in advanced CRC patients treated with bevacizumab and mFOLFOX6. Larger scale studies are needed to further validate our results.

Antiangiogenic drugs in ovarian cancer

BACKGROUND

There is a critical need to develop effective new strategies for the management of patients with advanced epithelial ovarian cancer.

OBJECTIVE

The purpose of this manuscript is to discuss the rationale for, and initial clinical results of, attempts to interfere with the process of tumor angiogenesis as a novel treatment paradigm in ovarian cancer.

RESULTS/CONCLUSION

Phase II clinical trial data provide strong support for the suggestion that antiangiogenic agents have the potential to play a major therapeutic role in this difficult malignancy. It is reasonable to acknowledge that the pending results of several ongoing evidence-based randomized Phase III trials that directly explore the clinical utility of this strategy may substantially alter the current standard management approaches in advanced ovarian cancer.