VEGF-VEGF receptor complexes as markers of tumor vascular endothelium

Baeckea frutescens L. Promotes wound healing by upregulating expression of TGF-β, IL-1 β, VEGF and MMP-2

Baeckea frutescens L. has been traditionally used for treating snakebites and is known to possess antifebrile and hemostatic properties. These properties are closely related to wound healing. This study aimed to evaluate the wound healing properties of B. frutescens leaves extract (BFLE) in vitro and in vivo. The in vitro study focused on proliferation, migration, and expression of TGF-β, IL-1β, VEGF, and MMP-2 genes and proteins. The in vivo study included excisional wound healing, histology, and tensile strength studies. The ethanolic extract of B. frutescens (BFLE) was tested for its effects on proliferation and migration using keratinocytes (HaCaT) and fibroblasts (BJ) cells. Gene and protein expression related to wound healing were analyzed using real-time PCR and Western blot assays. The wound healing properties of BFLE were evaluated in vivo using Wistar albino rats, focusing on excisional wound healing, histology, and tensile strength studies. The BFLE displayed significant proliferative and migratory effects on keratinocytes and fibroblasts cells, while upregulating the expression of TGF-β, IL-1β, VEGF, and MMP-2 genes and proteins. BFLE also exhibited significant wound healing effects on Wistar albino rats' excisional wounds and improved the overall tensile strength. The results suggest that BFLE has strong wound healing properties, as demonstrated by its ability to increase keratinocytes and fibroblasts proliferation and migration, upregulate genes and proteins involved in the wound healing process, and improve wound healing rates and tensile strength. The findings of this study provide important insights into the potential use of B. frutescens as a natural wound healing agent.

Updates on the use of liposomes for active tumor targeting in cancer therapy

In the development of cancer chemotherapy, besides the discovery of new anticancer drugs, a variety of nanocarrier systems for the delivery of previously developed and new chemotherapeutic drugs have currently been explored. Liposome is one of the most studied nanocarrier systems because of its biodegradability, simple preparation method, high efficacy and low toxicity. To make the best use of this vehicle, a number of multifunctionalized liposomal formulations have been investigated. The objective of this review is to summarize the current development of novel active targeting liposomal formulations, and to give insight into the challenges and future direction of the field. The recent studies in active targeting liposomes suggest the great potential of precise targeted anticancer drug delivery in cancer therapeutics.

Identification of the molecular mechanisms associated with acute type A aortic dissection through bioinformatics methods

Aortic dissection is characterized by the redirection of blood flow, which flows through an intimal tear into the aortic media. The purpose of this study was to find potential acute type A aortic dissection (AAAD)-related genes and molecular mechanisms by bioinformatics. The gene expression profiles of GSE52093 were obtained from Gene Expression Omnibus (GEO) database, including 7 AAAD samples and 5 normal samples. The differentially expressed genes (DEGs) were detected between AAAD and normal samples. The functional annotation and pathway enrichment analysis were conducted through the Database for Annotation, Visualization and Integration Discovery (DAVID). A protein-protein interaction network was established by the Search Tool for the Retrieval of Interacting Genes (STRING) software. The microRNAs (miRNAs) of these differentially expressed genes were predicted using <microRNA.org> database. Moreover, DEGs were analyzed in the comparative toxicogenomics (CTD) database to screen out the potential therapeutic small molecules. As a result, there were 172 DEGs identified in patients with AAAD. These DEGs were significantly enriched in 6 pathways, including cell cycle, oocyte meiosis, DNA replication, extracellular matrix-receptor interaction, and mineral absorption pathway. Notably, CDC20, CDK1, CHEK1, KIF20A, MCM10, PBK, PTTG1, RACGAP, and TOP2A were crucial genes with a high degree in the protein-protein interaction network. Furthermore, potential miRNAs (miR-301, miR-302 family, and miR-130 family) were identified. In addition, small molecules like azathioprine and zoledronic acid were identified to be potential drugs for AAAD.

Video-assisted thoracoscopic surgery lobectomy for lung cancer versus thoracotomy: a less decrease in sVEGFR2 level after surgery

BACKGROUND

Angiogenic and anti-angiogenic factors play an important role in tumor biology and tumor recurrence after surgical resection. Antiangiogenic factors such as vascular endothelial growth factor (VEGF)-receptor 1 (sVEGFR1) and sVEGFR2, two soluble form receptor proteins of VEGF, are critical for angiogenesis. VEGF can be sequestered by soluble forms of these receptors, which result in decreasing VEGF amount available to bind to its receptor on vascular endothelial cell surface. This study aimed to investigate the influences of video-assisted thoracoscopic surgery (VATS) lobectomy and open by thoracotomy for early stage non-small cell lung cancer (NSCLC) on postoperative circulating sVEGFR1 and sVEGFR2 levels.

METHODS

Forty-eight lung cancer patients underwent lobectomy through either VATS (n=26) or thoracotomy (n=22). Blood samples were collected from all patients preoperatively and postoperatively on days 1, 3 and 7. ELISA analysis was used to determine the plasma levels of sVEGFR1 and sVEGFR2. Data are reported as means and standard deviations, and were assessed with the Wilcoxon signed-Rank test (P<0.05).

RESULTS

For all patients undergoing lobectomy, postoperative sVEGFR1 levels on days 1 and 3 were markedly increased, while postoperative sVEGFR2 levels on days 1 and 3 were significantly decreased. Moreover, VATS group had significantly higher plasma level of sVEGFR2 postoperative in comparison with open thoracotomy (OT) on day 1 (VATS 6,953±1,535 pg/mL; OT 5,874±1,328 pg/mL, P<0.05).

CONCLUSIONS

Major pulmonary resection for early stage NSCLC resulted in the increased sVEGFR1 and decreased sVEGFR2 productions. VATS is associated with enhanced anti-angiogenic response with higher circulating sVEGFR2 levels compared with that with OT. Such differences in anti-angiogenic response may have an important effect on cancer biology and recurrence after surgery.

Microenvironment-Mediated Modeling of Tumor Response to Vascular-Targeting Drugs

The tumor-associated microvasculature is one of the key elements of the microenvironment that helps shape, and is shaped by, tumor progression. Given the important role of the vasculature in tumor progression, and the fact that tumor and normal vasculature are physiologically and molecularly distinct, much effort has gone into the development of vascular-targeting drugs that in theory should target tumors without significant risk to normal tissue. In this chapter, a multiscale hybrid mathematical model of tumor-vascular interactions is presented to provide a theoretical basis for assessing tumor response to vascular-targeting drugs. Model performance is calibrated to quantitative clinical data on tumor response to angiogenesis inhibitors (AIs), preclinical data on response to a cytotoxic chemotherapy, and qualitative preclinical data on response to vascular disrupting agents (VDAs). The calibrated model is then used to explore two questions of clinical interest. First, the hypothesis that AIs and VDAs are complementary treatments, rather than redundant, is explored. The model predicts a minimal increase in antitumor activity as a result of adding a VDA to an AI treatment regimen, and in fact at times the combination can exert less antitumor activity than stand-alone AI treatment. Second, the question of identifying an optimal dosing strategy for treating with an AI and a cytotoxic agent is addressed. Using a stochastic optimization scheme, an intermittent schedule for both chemotherapy and AI administration is identified that can eradicate the simulated tumors. We propose that this schedule may have increased clinical antitumor activity compared to currently used treatment protocols.

Recent developments in dynamic contrast-enhanced ultrasound imaging of tumor angiogenesis

Angiogenesis is a critical process for tumor growth and metastatic dissemination. There is tremendous interest in the development of noninvasive methods for imaging tumor angiogenesis, and ultrasound (US) is an emerging platform technology to address this challenge. The introduction of intravascular microbubble contrast agents not only allows real-time visualization of tumor perfusion during an US examination, but they can be functionalized with specific ligands to permit molecular US imaging of angiogenic biomarkers that are overexpressed on the tumor endothelium. In this article, we will review current concepts and developing trends for US imaging of tumor angiogenesis, including relevant preclinical and clinicsal findings.

Blood vessels as targets in tumor therapy

The landmark papers published by Judah Folkman in the early 1970s on tumor angiogenesis and therapeutic implications promoted the rapid development of a very dynamic field where basic scientists, oncologists, and pharmaceutical industry joined forces to determine the molecular mechanisms in blood vessel formation and find means to exploit this knowledge in suppressing tumor vascularization and growth. A wealth of information has been collected on angiogenic growth factors, and in 2004 the first specific blood vessel-targeted cancer therapy was introduced: a neutralizing antibody against vascular endothelial growth factor (VEGF). Now (2011) we know that suppression of tumor angiogenesis may be a double-edged sword and that the therapy needs to be further refined and individualized. This review describes the hallmarks of tumor vessels, how different angiogenic growth factors exert their function, and the perspectives for future development of anti-angiogenic therapy.

Optimization of vascular-targeting drugs in a computational model of tumor growth

A biophysical tool is introduced that seeks to provide a theoretical basis for helping drug design teams assess the most promising drug targets and design optimal treatment strategies. The tool is grounded in a previously validated computational model of the feedback that occurs between a growing tumor and the evolving vasculature. In this paper, the model is particularly used to explore the therapeutic effectiveness of two drugs that target the tumor vasculature: angiogenesis inhibitors (AIs) and vascular disrupting agents (VDAs). Using sensitivity analyses, the impact of VDA dosing parameters is explored, as is the effects of administering a VDA with an AI. Further, a stochastic optimization scheme is utilized to identify an optimal dosing schedule for treatment with an AI and a chemotherapeutic. The treatment regimen identified can successfully halt simulated tumor growth, even after the cessation of therapy.

Computational modeling of tumor response to vascular-targeting therapies--part I: validation

Mathematical modeling techniques have been widely employed to understand how cancer grows, and, more recently, such approaches have been used to understand how cancer can be controlled. In this manuscript, a previously validated hybrid cellular automaton model of tumor growth in a vascularized environment is used to study the antitumor activity of several vascular-targeting compounds of known efficacy. In particular, this model is used to test the antitumor activity of a clinically used angiogenesis inhibitor (both in isolation, and with a cytotoxic chemotherapeutic) and a vascular disrupting agent currently undergoing clinical trial testing. I demonstrate that the mathematical model can make predictions in agreement with preclinical/clinical data and can also be used to gain more insight into these treatment protocols. The results presented herein suggest that vascular-targeting agents, as currently administered, cannot lead to cancer eradication, although a highly efficacious agent may lead to long-term cancer control.

[Effects of Baihe Recipe on expressions of vascular endothelial growth factor and p53 proteins in tumor tissues of nude mice bearing orthotopically transplanted gastric carcinoma BGC-823]

OBJECTIVE

To investigate the effects of Baihe Recipe, a compound traditional Chinese herbal medicine, on growth and metastasis of orthotopically transplanted gastric carcinoma and the expressions of vascular endothelial growth factor (VEGF) and p53 proteins in the tumor tissues in nude mice.

METHODS

Forty-five nude mice orthotopically transplanted with BGC-823 human gastric cancer cells were randomly divided into three groups: Baihe Recipe group, 5-fluorouracil (5-FU) group and untreated group. The mice in the Baihe Recipe group received intragastric administration of 0.5 mL Baihe Recipe (crude drug content was 0.2 g/mL) for 6 weeks, and the mice in the untreated group received 0.5 mL normal saline. The mice in the 5-FU group received an intraperitoneal injection of 5-FU dilution (0.2 mL, 60 mg/kg per week, for 3 weeks). All mice were sacrificed after 6-week treatment. The weights of tumor and the growth-inhibiting rate were measured and the expressions of VEGF and p53 proteins were detected by immunohistochemical method.

RESULTS

The growth inhibition rates in the Baihe Recipe and 5-FU groups were 52.86% and 42.87% respectively. The incidence rates of metastasis to perigastric and hepatic portal lymph nodes, and to liver and peritoneum in the Baihe Recipe and 5-FU groups were lower than those in the untreated group. The metastasis rates in Baihe Recipe group, 5-FU group and untreated group were 33.33%, 35.71% and 80.00% respectively, with significant difference (P<0.05), and the expressions of VEGF and p53 proteins in tumor tissues in the Baihe Recipe group were lower than those in the untreated group and the 5-FU group (P<0.01, P<0.05).

CONCLUSION

Baihe Recipe has inhibitory effects on tumor growth and metastasis of gastric cancer orthotopically transplanted in nude mice by down-regulating the expressions of VEGF and p53 proteins.

Molecular ultrasound assessment of tumor angiogenesis

Angiogenesis, the growth of new blood vessels, plays a critical role in progression of tumor growth and metastasis, making it an attractive target for both cancer imaging and therapy. Several molecular markers, including those that are involved in the angiogenesis signaling pathway and those unique to tumor angiogenic vessels, have been identified and can be used as targets for molecular imaging of cancer. With the introduction of ultrasound contrast agents that can be targeted to those molecular markers, targeted contrast-enhanced ultrasound (molecular ultrasound) imaging has become an attractive imaging modality to non-invasively assess tumor angiogenesis at the molecular level. The advantages of molecular ultrasound imaging such as high temporal and spatial resolution, non-invasiveness, real-time imaging, relatively low cost, lack of ionizing irradiation and wide availability among the imaging community will further expand its roles in cancer imaging and drug development both in preclinical research and future clinical applications.

Methods for the identification of vascular markers in health and disease: from the bench to the clinic

Several diseases are characterized by changes in the molecular composition of vascular structures, thus offering the opportunity to use specific ligands (e.g., monoclonal antibodies) for imaging and therapy application. This novel pharmaceutical strategy, often referred to as "vascular targeting", promises to facilitate the discovery and development of selective biopharmaceuticals for the management of angiogenesis-related diseases. This article reviews novel biomedical applications based on vascular targeting strategies, as well as methodologies which have been used for the discovery of vascular markers of pathology.

Autocrine VEGF-VEGF-R loop on podocytes during glomerulonephritis in humans

BACKGROUND

Vascular endothelial growth factor (VEGF) is the most important and tightly regulated angiogenic cytokine in the kidney. Its activity is critical for capillary/glomerular preservation and repair, and recent studies have also demonstrated its relevance for the preservation of podocytes.

METHODS

The present study investigated a large number (n = 153) of renal biopsies from patients with glomerulonephritis (GN) and evaluated the expression and activity of the glomerular VEGF system [VEGF, VEGF-R1, VEGF-R2 and biologically active VEGF as identified by VEGF-VEGF receptor complexes (VEGF-VEGF-R)] in parallel with markers of renal function, injury and repair.

RESULTS

Whereas glomerular VEGF expression was clearly elevated, VEGF-R expression levels were widely unchanged. In parallel to the overall VEGF expression, the biological activity of VEGF on its receptors was uniformly significantly enhanced. Interestingly, the expression pattern of VEGF-R1 and VEGF-R2 significantly changed during GN where a very prominent podocytic pattern appeared, which was also detected for receptor-bound VEGF. VEGF expression and activity could be linked with indicators of renal injury such as glomerular proliferation and creatinine, respectively.

CONCLUSIONS

This study shows, for the first time, increased podocytic VEGF-VEGF-R binding during human GN, suggesting not only the existence of a glomerular paracrine proangiogenic, but also an autocrine role of the VEGF-VEGF-R system in diseased podocytes.

Antiangiogenic gene therapy of experimental pancreatic tumor by sFlt-1 plasmid DNA carried by RGD-modified crosslinked polyplex micelles

Disulfide crosslinked polyplex micelles with RGD peptides were formed through ion complexation of thiolated c(RGDfK)-poly(ethylene glycol)-block-poly(L-lysine) (c(RGDfK)-PEG-P(Lys-SH)) and plasmid DNA encoding sFlt-1 and tested for their therapeutic effect in BxPC3 pancreatic adenocarcinoma tumor bearing mice. These micelles, systemically injected, demonstrated significant inhibition of tumor growth up to day 18, as a result of the antiangiogenic effect that was confirmed by vascular density measurements. Significant therapeutic activity of the 15% crosslinked micelle (c(RGDfK)-PEG-P(Lys-SH15)) was achieved by combined effect of increased tumor accumulation, interaction with endothelial cells and enhanced intracellular uptake through receptor-mediated endocytosis. These results suggest that RGD targeted crosslinked polyplex micelles can be effective plasmid DNA carriers for antiangiogenic gene therapy.

Angiopoietin-2 levels are associated with disease progression in metastatic malignant melanoma

PURPOSE

The blood vessel-destabilizing Tie2 ligand angiopoietin-2 (Ang-2) acts in concert with the vascular endothelial growth factor/vascular endothelial growth factor receptor system to control vessel assembly during tumor progression. We hypothesized that circulating soluble Ang-2 (sAng-2) may be involved in melanoma progression.

EXPERIMENTAL DESIGN

Serum samples (n=98) from melanoma patients (American Joint Committee on Cancer stages I-IV), biopsies of corresponding patients, and human melanoma cell lines were analyzed for expression of Ang-2 and S100beta. Multiple sera of a subcohort of 33 patients were tested during progression from stage III to IV. Small interfering RNA-based loss-of-function experiments were done to assess effects of Ang-2 on melanoma cells.

RESULTS

Circulating levels of sAng-2 correlate with tumor progression in melanoma patients (P<0.0001) and patient survival (P=0.007). Analysis of serum samples during the transition from stage III to IV identified an increase of sAng-2 up to 400%. Comparative analyses revealed a 56% superiority of sAng-2 as predictive marker over the established marker S100beta. Immunohistochemistry and reverse transcription-PCR confirmed the prominent expression of Ang-2 by tumor-associated endothelial cells but identified Ang-2 also as a secreted product of melanoma cells themselves. Corresponding cellular experiments revealed that human melanoma-isolated tumor cells were Tie2 positive and that Ang-2 acted as an autocrine regulator of melanoma cell migration and invasion.

CONCLUSIONS

The experiments establish sAng-2 as a biomarker of melanoma progression and metastasis correlating with tumor load and overall survival. The identification of an autocrine angiopoietin/Tie loop controlling melanoma migration and invasion warrants further functional experiments and validate the angiopoietin/Tie system as a promising therapeutic target for human melanomas.

Antibody library-based tumor endothelial cells surface proteomic functional screen reveals migration-stimulating factor as an anti-angiogenic target

Angiogenesis is critical for cancer development and metastasis. Here we have employed a functional antibody library-based proteomic screen to identify proteins that participate in and might be used as therapeutic targets for tumor-related angiogenesis. Mice were immunized with human esophageal cancer endothelial cells (HECEC). The antibody library was established with the mouse spleen cells the serum of which had most anti-angiogenic effect. Monoclonal antibodies were subjected to an immunoreactive and functional screen and monoclonal antibodies that reacted strongly with cell surface antigens of HECECs and influenced their behavior were selected. Antigens that recognized by the antibodies were obtained by immunoprecipitation and then identified by mass spectrometry analysis. Migration-stimulating factor (MSF), the antigen of 1D2 antibody was identified using this approach. Further studies demonstrated that the 1D2 antibody suppressed MSF-effected migration and adhesion of HECECs on fibronectin matrix. Biodistribution assay showed that MSF targeting antibody 1D2 could specifically home to the xenograft with humanized blood vessel. Targeting treatment with 1D2 antibody significantly suppressed tumor growth through inhibition of human tumor-related angiogenesis. These results indicate that the functional antibody library-based proteomic screen can successfully identify proteins that involved in tumor-related angiogenesis and MSF may be a target for the anti-angiogenic treatment of the esophageal cancer.

Relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent and the level of VEGFR2 expression in an in vivo breast cancer model

OBJECTIVE

The aim of this study was to characterize the relationship between retention of a vascular endothelial growth factor receptor 2 (VEGFR2)-targeted ultrasonographic contrast agent (UCA) and VEGFR2 expression in tumor vasculature of breast cancer.

METHODS

67NR breast cancer tumors implanted in mice were evaluated in vivo with both VEGFR2-targeted and nontargeted UCAs, and a high-frequency ultrasound system. A bolus of the UCA was injected and allowed to circulate for 4 minutes to allow binding of targeted microbubbles. After that, 2 sets of images before and after a high-power ultrasonic destruction sequence were acquired. The average video intensity of predestruction and postdestruction images was measured and used as a relative measure of retention of the UCA in the tumor. Levels of VEGFR2 expression and tumor vascular density were quantified by immunohistochemical staining and compared with retention of the VEGFR2-targeted UCA.

RESULTS

Retention of VEGFR2-targeted microbubbles in tumors was significantly higher than retention of nontargeted microbubbles (mean +/- SD, 47.75+/-9.85 versus 18.5+/-5.46 dB; P< .001). Retention of the VEGFR2-targeted UCA was found to correlate with the level of VEGFR2 expression in the studied tumors (r(2)=0.41). In contrast, retention of the nontargeted UCA was not correlated with the level of VEGFR2 expression (r(2)=0.08). Furthermore, retention of the VEGFR2-targeted UCA was not correlated with the level of tumor vascularity.

CONCLUSIONS

The magnitude of the molecular ultrasonographic signal from a VEGFR2-targeted UCA retained by tissue correlates with VEGFR2 expression. These results validate the use of molecular ultrasonography for in vivo detection and quantification of VEGFR2 expression in this breast cancer model.

The preparation and characterization of anti-VEGFR2 conjugated, paclitaxel-loaded PLLA or PLGA microspheres for the systemic targeting of human prostate tumors

PURPOSE

The objective of this study was to manufacture paclitaxel (PTX) loaded polymeric microspheres, that were surface conjugated with antibodies to vascular endothelial growth factor receptor 2 (anti-VEGFR2), for systemic targeting to angiogenic sites in prostate tumors.

METHODS

Microspheres were manufactured in the 1-3 microm size range from poly (l-lactic acid) (PLLA) or poly (lactide-co-glycolide) (PLGA) by a modified solvent evaporation method using Polytron homogenization followed by high speed dispersion in poly vinyl alcohol. Antibodies were conjugated to the surface of these microspheres using cyanogen bromide activation of the polymer surface. Cell Binding was determined using human umbilical vein endothelial cells (HUVECs) in vitro. Efficacy determinations were made using human prostate tumors (PC-3) grown subcutaneously in mice.

RESULTS

Antibodies were effectively bound to the surface of PLLA and PLGA microspheres. Anti-VEGFR2 conjugated PLLA microspheres bound strongly to HUVEC's. Pilot efficacy studies in mice showed variability but demonstrated a significant inhibition of tumor growth following the systemic administration of a single dose of PTX-loaded anti-VEGFR2 conjugated PLLA microspheres as compared to non-antibody-conjugated PTX-loaded microspheres.

CONCLUSION

Anti-VEGFR2 conjugated PLLA microspheres containing PTX may offer an effective way of administering a controlled release formulation of the drug to target prostate tumors.

Systematic review: the application of molecular pathogenesis to prevention and treatment of oesophageal adenocarcinoma

BACKGROUND

Oesophageal adenocarcinoma is an increasingly common cancer with a poor prognosis. It develops in a stepwise progression from Barrett's metaplasia to dysplasia, and then adenocarcinoma followed by metastasis.

AIM

To outline the key molecular changes in oesophageal adenocarcinoma and to summarize the chemopreventative and therapeutic strategies proposed.

METHODS

A literature search was performed to identify appropriate research papers in the field. Search terms included: Barrett's (o)esophagus, intestinal metaplasia, (o)esophageal adenocarcinoma, molecular changes, genetic changes, pathogenesis, chemoprevention, therapeutic strategies and treatment. The search was restricted to English language articles.

RESULTS

A large number of molecular changes have been identified in the progression from Barrett's oesophagus to oesophageal adenocarcinoma although there does not appear to be an obligate order of events. Potential chemoprevention strategies include acid suppression, anti-inflammatory agents and antioxidants. In established adenocarcinoma, targeted treatments under evaluation include receptor tyrosine kinase inhibitors of EGFR and cyclin-dependent kinase inhibitors, which may benefit a subgroup of patients.

CONCLUSIONS

Advances in molecular methodology have led to a greater understanding of the oesophageal adenocarcinoma pathways, which provides opportunities for chemoprevention and therapeutic strategies with a mechanistic basis. More work is required to assess both the safety and efficacy of these new treatments.

Genetic alteration of endothelial heparan sulfate selectively inhibits tumor angiogenesis

To examine the role of endothelial heparan sulfate during angiogenesis, we generated mice bearing an endothelial-targeted deletion in the biosynthetic enzyme N-acetylglucosamine N-deacetylase/N-sulfotransferase 1 (Ndst1). Physiological angiogenesis during cutaneous wound repair was unaffected, as was growth and reproductive capacity of the mice. In contrast, pathological angiogenesis in experimental tumors was altered, resulting in smaller tumors and reduced microvascular density and branching. To simulate the angiogenic environment of the tumor, endothelial cells were isolated and propagated in vitro with proangiogenic growth factors. Binding of FGF-2 and VEGF(164) to cells and to purified heparan sulfate was dramatically reduced. Mutant endothelial cells also exhibited altered sprouting responses to FGF-2 and VEGF(164), reduced Erk phosphorylation, and an increase in apoptosis in branching assays. Corresponding changes in growth factor binding to tumor endothelium and apoptosis were also observed in vivo. These findings demonstrate a cell-autonomous effect of heparan sulfate on endothelial cell growth in the context of tumor angiogenesis.

Enhanced tumorigenicity of fibroblasts transformed with human herpesvirus 8 chemokine receptor vGPCR by successive passage in nude and immunocompetent mice

The human herpes virus 8 (HHV-8)-encoded G protein-coupled chemokine receptor (vGPCR) has been implicated in the pathogenesis of Kaposi's sarcoma (KS), particularly because of its high constitutive signaling activity. Here, we used retroviral transduction to generate vGPCR-expressing 3T3 fibroblasts that are tumorigenic in nude mice, but as expected fail to induce tumors in their immunocompetent counterparts. However, tumor fragments obtained from nude mice grow progressively in immunocompetent BALB/c mice. Unexpectedly, vGPCR-expressing cells established from grafted tumor fragments gave rise to tumors in immunocompetent mice. These tumors exhibit a striking histological resemblance to KS including plump spindle cell morphology, a high degree of vascularization and brisk mitotic activity. High expression of vGPCR was confirmed in the cell lines and tumors using a newly developed vGPCR-specific monoclonal antibody. Finally, short interfering RNA directed at vGPCR abrogated or significantly delayed tumorigenesis in mice, demonstrating that the tumor development is specifically driven by vGPCR. This novel model for vGPCR-mediated oncogenesis will contribute to our understanding of the role of vGPCR in the pathogenesis of HHV-8 and may even be important in identifying critical molecular and epigenetic changes during tumor progression in vivo.

Molecular optical imaging of therapeutic targets of cancer

Recent progress in discerning the molecular events that accompany carcinogenesis has led to development of new cancer therapies directly targeted against the molecular changes of neoplasia. Molecular-targeted therapeutics have shown significant improvements in response rates and decreased toxicity as compared to conventional cytotoxic therapies which lack specificity for tumor cells. In order to fully explore the potential of molecular-targeted therapy, a new set of tools is required to dynamically and quantitatively image and monitor the heterogeneous molecular profiles of tumors in vivo. Currently, molecular markers can only be visualized in vitro using complex immunohistochemical staining protocols. In this chapter, we discuss emerging optical tools to image in vivo a molecular profile of risk-based hallmarks of cancer for selecting and monitoring therapy. We present the combination of optically active, targeted nanoparticles for molecular imaging with advances in minimally invasive optical imaging systems, which can be used to dynamically image both a molecular and phenotypic profile of risk and to monitor changes in this profile during therapy.

Modeling the effects of vasculature evolution on early brain tumor growth

Mathematical modeling of both tumor growth and angiogenesis have been active areas of research for the past several decades. Such models can be classified into one of two categories: those that analyze the remodeling of the vasculature while ignoring changes in the tumor mass, and those that predict tumor expansion in the presence of a non-evolving vasculature. However, it is well accepted that vasculature remodeling and tumor growth strongly depend on one another. For this reason, we have developed a two-dimensional hybrid cellular automaton model of early brain tumor growth that couples the remodeling of the microvasculature with the evolution of the tumor mass. A system of reaction-diffusion equations has been developed to track the concentration of vascular endothelial growth factor (VEGF), Ang-1, Ang-2, their receptors and their complexes in space and time. The properties of the vasculature and hence of each cell are determined by the relative concentrations of these key angiogenic factors. The model exhibits an angiogenic switch consistent with experimental observations on the upregulation of angiogenesis. Particularly, we show that if the pathways that produce and respond to VEGF and the angiopoietins are properly functioning, angiogenesis is initiated and a tumor can grow to a macroscopic size. However, if the VEGF pathway is inhibited, angiogenesis does not occur and tumor growth is thwarted beyond 1-2mm in size. Furthermore, we show that tumor expansion can occur in well-vascularized environments even when angiogenesis is inhibited, suggesting that anti-angiogenic therapies may not be sufficient to eliminate a population of actively dividing malignant cells.

Phosphorylated KDR can be located in the nucleus of neoplastic cells

KDR (kinase insert domain receptor) phosphorylation induces several effects which lead eventually to cell proliferation and survival. The precise mechanisms by which KDR, once it is activated, communicates with the nucleus are starting to be understood but have not yet been completely unravelled. Two in vitro studies on animal cell lines reported in the literature have demonstrated that, following stimulation with VEGF, KDR is actually translocated within the nucleus. Our aim was to investigate whether this translocation occurs in human cells both in vitro and in vivo. Using laser scanning confocal microscopy, a variable nuclear localization of phosphorylated and total KDR in cell lines and tumour samples was found. In human neoplastic cell lines, hypoxic stimulation greatly increased the nuclear amount of total KDR but less so that of the phosphorylated form. Only after hypoxia and VEGF stimulation there was a comparably increased expression of phosphorylated and total KDR observed in the nuclei of these cells. We conclude that neoplastic cells show a variable expression of total and phosphorylated KDR in the nucleus. The precise functional meaning of nuclear location remains to be established.

Local VEGF activity but not VEGF expression is tightly regulated during diabetic nephropathy in man

Several studies have implicated the angiogenic cytokine vascular endothelial growth factor (VEGF) in the development of diabetic nephropathy, but no data are available about its local activity during human disease. Glomeruli from 52 archival biopsies from type II diabetics were evaluated and compared to 10 renal biopsies without kidney disease (controls). Glomerulosclerosis, capillary rarefaction, glomerular and endothelial cell proliferation, apoptosis, VEGF expression, as well as receptor-bound VEGF indicating local VEGF activity, and phosphorylation of the signal transduction molecule Akt were investigated. Owing to substantial heterogeneity of glomerular lesions in individual biopsies, these parameters were correlated with the degree of injury in individual glomeruli rather than biopsies. Severe glomerular capillary rarefaction was linked to the degree of glomerulosclerosis. While cellular apoptosis was detected independent of the stage of injury, endothelial cell proliferation indicating capillary repair was markedly increased only in mildly/moderately injured glomeruli. In controls, VEGF was predominantly expressed in podocytes, whereas receptor-bound VEGF was confined to the glomerular endothelium. VEGF expression was increased in all diabetic glomeruli by many different cell types. In contrast, VEGF receptor activation was increased predominantly in the endothelium of only mildly injured glomeruli, but significantly decreased in more severely injured glomeruli. Diabetic nephropathy is associated with glomerular capillary rarefaction. Despite overall increased glomerular VEGF, the decreased receptor-bound VEGF on the endothelium may be an indicator of an insufficient capillary repair reaction.

Ectopic expression of PTTG1/securin promotes tumorigenesis in human embryonic kidney cells

Background

Pituitary tumor transforming gene1 (PTTG1) is a novel oncogene that is expressed in most tumors. It encodes a protein that is primarily involved in the regulation of sister chromatid separation during cell division. The oncogenic potential of PTTG1 has been well characterized in the mouse, particularly mouse fibroblast (NIH3T3) cells, in which it induces cell proliferation, promotes tumor formation and angiogenesis. Human tumorigenesis is a complex and a multistep process often requiring concordant expression of a number of genes. Also due to differences between rodent and human cell biology it is difficult to extrapolate results from mouse models to humans. To determine if PTTG1 functions similarly as an oncogene in humans, we have characterized its effects on human embryonic kidney (HEK293) cells.

Results

We report that introduction of human PTTG1 into HEK293 cells through transfection with PTTG1 cDNA resulted in increased cell proliferation, anchorage-independent growth in soft agar, and formation of tumors after subcutaneous injection of nu/nu mice. Pathologic analysis revealed that these tumors were poorly differentiated. Both analysis of HEK293 cells transiently transfected with PTTG1 cDNA and analysis of tumors developed on injection of HEK293 cells that had been stably transfected with PTTG1 cDNA indicated significantly higher levels of secretion and expression of bFGF, VEGF and IL-8 compared to HEK293 cells transfected with pcDNA3.1 vector or uninvolved tissues collected from the mice. Mutation of the proline-rich motifs at the C-terminal of PTTG1 abolished its oncogenic properties. Mice injected with this mutated PTTG1 either did not form tumors or formed very small tumors. Taken together our results suggest that PTTG1 is a human oncogene that possesses the ability to promote tumorigenesis in human cells at least in part through the regulation of expression or secretion of bFGF, VEGF and IL-8.

Conclusions

Our results demonstrate that PTTG1 is a potent human oncogene and has the ability to induce cellular transformation of human cells. Overexpression of PTTG1 in HEK293 cells leads to an increase in the secretion and expression of bFGF, VEGF and IL-8. Mutation of C-terminal proline-rich motifs abrogates the oncogenic function of PTTG1. To our knowledge, this is the first study demonstrating the importance of PTTG1 in human tumorigenesis.

Targeted therapies for non–small-cell lung cancer: biology, rationale, and preclinical results from a radiation oncology perspective

The epidermal growth factor receptor (EGFR) is overexpressed in the majority of non-small-cell lung cancers (NSCLCs). This presents an opportune target for new treatment strategies designed to selectively interfere with the cancer cell growth cycle. Recent investigations into the biology of the EGFR and its downstream signaling pathways have reminded us of the complexity of cancer cell communications from the cytoplasm to the nucleus. Multiple pathways are activated with stimulation of the autocrine and paracrine EGFR loop, from the ras-raf-MEK activation of ERK 1/2 to the P13K-Akt pathway, each playing an important role in cancer cell survival, invasion, and angiogenesis. Preclinical studies have demonstrated that molecules targeting the EGFR, either through extracellular blockade or intracellular interference with the EGFR-associated tyrosine kinase, reversibly or irreversibly, inhibit cancer cell growth. Potent antitumor effects have been observed in human tumor xenograft models. Preclinical studies have also demonstrated cooperative effects when anti-EGFR agents are combined with radiation or chemotherapy. Many of these agents have now entered into advanced human clinical trials with modest dose-related toxicity despite chronic administration. Encouraging response rates with single-agent targeted therapy have been reported in heavily pretreated patients with advanced NSCLC. In addition, agents targeting the angiogenic pathway, which plays a key role in the regulation of angiogenesis, may play an important role in enhancing the efficacy of anti-EGFR agents. This article will focus on the biology, rationale, and preclinical studies with targeted anti-EGFR and antiangiogenic therapies for the management of NSCLC.

Tumor-targeting properties of antibody-vascular endothelial growth factor fusion proteins

A major problem of antibody-based targeting of solid tumors is the poor penetration of antibodies into tumor tissue. Vasoactive immunoconjugates have been proposed as a means of increasing antibody uptake in tumors. In principle, VEGF (also known as vascular permeability factor) could selectively alter vascular permeability, leading to improved tumor targeting. A possible role for VEGF in the targeting of tumor neovasculature has been postulated, based on the overexpression of VEGF receptors in tumor endothelial cells. However, quantitative biodistribution studies on this topic are not available. In this report, we describe the cloning, expression, characterization and biodistribution in tumor-bearing mice of antibodies fused to either VEGF(120) or VEGF(164) The MAb fragments chosen for analysis were scFv(L19), specific for the ED-B domain of fibronectin, a marker of angiogenesis, and scFv(HyHEL-10), a negative control antibody of irrelevant specificity in mice. Neither unconjugated VEGF nor scFv(HyHEL-10)-VEGF fusion proteins showed accumulation in the tumor (tumor:blood ratios approx. 1 at 4 hr and 24 hr postinjection). By contrast, scFv(L19)-VEGF(120) but not scFv(L19)-VEGF(164) showed significant accumulation in tumors (tumor:blood ratio = 9.3 at 24 hr) but was not superior to unconjugated scFv(L19). Preinjection of unlabeled scFv(L19)-VEGF(120) prior to administration of radiolabeled fusion protein led to increased accumulation of radiolabeled scFv(L19)-VEGF(120) in the tumor but only at very high concentrations (20 microg/mouse).

Vascular permeability factor/vascular endothelial growth factor: a critical cytokine in tumor angiogenesis and a potential target for diagnosis and therapy

Vascular endothelial growth factor A (VEGF-A), the founding member of the vascular permeability factor (VPF)/VEGF family of proteins, is an important angiogenic cytokine with critical roles in tumor angiogenesis. This article reviews the literature with regard to VEGF-A's multiple functions, the mechanisms by which it induces angiogenesis, and its current and projected roles in clinical oncology. VEGF-A is a multifunctional cytokine that is widely expressed by tumor cells and that acts through receptors (VEGFR-1, VEGFR-2, and neuropilin) that are expressed on vascular endothelium and on some other cells. It increases microvascular permeability, induces endothelial cell migration and division, reprograms gene expression, promotes endothelial cell survival, prevents senescence, and induces angiogenesis. Recently, VEGF-A has also been shown to induce lymphangiogenesis. Measurements of circulating levels of VEGF-A may have value in estimating prognosis, and VEGF-A and its receptors are potential targets for therapy. Recognized as the single most important angiogenic cytokine, VEGF-A has a central role in tumor biology and will likely have an important role in future approaches designed to evaluate patient prognosis. It may also become an important target for cancer therapy.