Successful inhibition of intracranial human glioblastoma multiforme xenograft growth via systemic adenoviral delivery of soluble endostatin and soluble vascular endothelial growth factor receptor-2: laboratory investigation

Exploring the Past, Present, and Future of Anti-Angiogenic Therapy in Glioblastoma

Glioblastoma, a WHO grade IV astrocytoma, constitutes approximately half of malignant tumors of the central nervous system. Despite technological advancements and aggressive multimodal treatment, prognosis remains dismal. The highly vascularized nature of glioblastoma enables the tumor cells to grow and invade the surrounding tissue, and vascular endothelial growth factor-A (VEGF-A) is a critical mediator of this process. Therefore, over the past decade, angiogenesis, and more specifically, the VEGF signaling pathway, has emerged as a therapeutic target for glioblastoma therapy. This led to the FDA approval of bevacizumab, a monoclonal antibody designed against VEGF-A, for treatment of recurrent glioblastoma. Despite the promising preclinical data and its theoretical effectiveness, bevacizumab has failed to improve patients' overall survival. Furthermore, several other anti-angiogenic agents that target the VEGF signaling pathway have also not demonstrated survival improvement. This suggests the presence of other compensatory angiogenic signaling pathways that surpass the anti-angiogenic effects of these agents and facilitate vascularization despite ongoing VEGF signaling inhibition. Herein, we review the current state of anti-angiogenic agents, discuss potential mechanisms of anti-angiogenic resistance, and suggest potential avenues to increase the efficacy of this therapeutic approach.

Ameliorating Fibrosis in Murine and Human Tissues with END55, an Endostatin-Derived Fusion Protein Made in Plants

Organ fibrosis, particularly of the lungs, causes significant morbidity and mortality. Effective treatments are needed to reduce the health burden. A fragment of the carboxyl-terminal end of collagen XVIII/endostatin reduces skin and lung fibrosis. This fragment was modified to facilitate its production in plants, which resulted in the recombinant fusion protein, END55. We found that expression of END55 had significant anti-fibrotic effects on the treatment and prevention of skin and lung fibrosis in a bleomycin mouse model. We validated these effects in a second mouse model of pulmonary fibrosis involving inducible, lung-targeted expression of transforming growth factor β1. END55 also exerted anti-fibrotic effects in human lung and skin tissues maintained in organ culture in which fibrosis was experimentally induced. The anti-fibrotic effect of END55 was mediated by a decrease in the expression of extracellular matrix genes and an increase in the levels of matrix-degrading enzymes. Finally, END55 reduced fibrosis in the lungs of patients with systemic sclerosis (SSc) and idiopathic pulmonary fibrosis (IPF) who underwent lung transplantation due to the severity of their lung disease, displaying efficacy in human tissues directly relevant to human disease. These findings demonstrate that END55 is an effective anti-fibrotic therapy in different organs.

Brain Cancer Treatment; A Systematic Review

Context: One of the most common aggressive and primary brain tumors is glioma. The majority of diagnoses are referred to high-grade malignant glioblastoma, which carries the worst prognosis. Still, treatment of brain tumors remains a big challenge for clinicians. This study was designed to investigate the efficacy of gene therapy in the treatment of brain cancer. Methods: Studies use genes as a therapeutic agent in brain cancer treatment even alone or in combination with other treatment methods. Full-text papers, which met the inclusion criteria, were independently assessed by two reviewers. Disagreements were resolved by consultation with a third reviewer. Results: Statistical analysis showed that 50% of the papers used a virus, 36% used polymers, and 14% used cells as carriers to transfect the genes as a therapeutic agent in brain tumor models. Data showed that the estimated size of the brain tumor was reduced by using co-treatment of the gene with one of the conventional therapies. Conclusions: According to the results, co-treatment of the gene with conventional therapies could be more effective than the monotherapy methods.

Viral Gene Therapy for Glioblastoma Multiforme: A Promising Hope for the Current Dilemma

Glioblastoma multiforme (GBM), as one of the most common malignant brain tumors, was limited in its treatment effectiveness with current options. Its invasive and infiltrative features led to tumor recurrence and poor prognosis. Effective treatment and survival improvement have always been a challenge. With the exploration of genetic mutations and molecular pathways in neuro-oncology, gene therapy is becoming a promising therapeutic approach. Therapeutic genes are delivered into target cells with viral vectors to act specific antitumor effects, which can be used in gene delivery, play an oncolysis effect, and induce host immune response. The application of engineering technology makes the virus vector used in genetics a more prospective future. Recent advances in viral gene therapy offer hope for treating brain tumors. In this review, we discuss the types and designs of viruses as well as their study progress and potential applications in the treatment of GBM. Although still under research, viral gene therapy is promising to be a new therapeutic approach for GBM treatment in the future.

Intranasal delivery of Paclitaxel encapsulated nanoparticles for brain injury due to Glioblastoma

Brain injury is a common cause for physical and emotional effects to the large number of populations. Moreover, glioblastoma is the tumor in brain with no possible treatment leading to death. The blood-brain barrier's makes the treatment more difficult by preventing the drugs to reach central nervous system. Paclitaxel (PTX) encapsulated Poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), PTX-PLGA-NPs were developed using emulsification method. The PTX-PLGA-NPs were characterized using Malvern Zetasizer and Scanning Electron Microscopy and were evaluated for their cytotoxicity in U87MG cells. PTX-PLGA-NPs were prepared using single emulsion method having size of 154 ± 22.19 nm with zeta potential of -23.7 mV. The PTX-PLGA-NPs were spherical in shape and have dose dependent cytotoxicity on U87MG cells. The PTX was released from the particles with initial burst release followed by sustained release pattern. The biodistribution was studied in mice with glioblastoma model using ¹²⁵I radiolabeled PTX-PLGA-NPs and anti-glioblastoma was studied with PTX-PLGA-NPs. The biodistribution studies revealed PTX-PLGA-NPs after intranasal administration resulted in higher in vivo uptake with high anti-glioblastoma efficacy. The results suggest that PTX-PLGA-NPs administered through intranasal route have potential in the treatment of glioblastoma.

Heart-derived fibroblasts express LYPD-1 and negatively regulate angiogenesis in rat

Angiogenesis is regulated by a balance between promoting and inhibitory mechanisms. Although angiogenesis-promoting mechanisms have been well studied in ischemic heart diseases, angiogenesis-inhibitory mechanisms have not. Recently, we identified LYPD-1 as a novel anti-angiogenic factor derived from human heart-derived fibroblasts, which suppresses endothelial cell network formation in co-culture. However, it remains unclear whether the low angiogenicity of heart-derived fibroblasts with high expression of LYPD-1 is also observed in other mammalian species, and the properties of LYPD-1 under normal and pathological conditions remain elusive. Fibroblasts isolated from neonatal and adult rat heart also express LYPD-1 and inhibit endothelial network formation in co-culture. Moreover, immunohistochemical analysis revealed that LYPD-1 was predominantly observed in the interstitial tissues of rat heart and LYPD1 expression levels were identical from late developmental period to adult. Conversely, LYPD-1 mRNA expression was significantly downregulated temporally in myocardial infarction model rats, suggesting that angiogenesis-inhibitory mechanisms might not be sufficiently suppressed to promote angiogenesis in ischemic heart diseases. These findings suggest that heart has relatively low angiogenicity compared with other organs via the high expression of LYPD-1 by fibroblasts. Moreover, understanding the regulatory mechanisms of LYPD-1-mediated inhibition of angiogenesis might lead a novel angiogenic therapy for ischemic heart diseases and contribute to development of bioengineered cardiac tissue.

Glioblastoma Treatment Modalities besides Surgery

Glioblastoma multiforme (GBM) is commonly known as the most aggressive primary CNS tumor in adults. The mean survival of it is 14 to 15 months, following the standard therapy from surgery, chemotherapy, to radiotherapy. Efforts in recent decades have brought many novel therapies to light, however, with limitations. In this paper, authors reviewed current treatments for GBM besides surgery. In the past decades, only radiotherapy, temozolomide (TMZ), and tumor treating field (TTF) were approved by FDA. Though promising in preclinical experiments, therapeutic effects of other novel treatments including BNCT, anti-angiogenic therapy, immunotherapy, epigenetic therapy, oncolytic virus therapy, and gene therapy are still either uncertain or discouraging in clinical results. In this review, we went through current clinical trials, underlying causes, and future therapy designs to present neurosurgeons and researchers a sketch of this field.

A Critical Overview of Targeted Therapies for Glioblastoma

Over the past century, treatment of malignant tumors of the brain has remained a challenge. Refinements in neurosurgical techniques, discovery of powerful chemotherapeutic agents, advances in radiotherapy, applications of biotechnology, and improvements in methods of targeted delivery have led to some extension of length of survival of glioblastoma patients. Refinements in surgery are mentioned because most of the patients with glioblastoma undergo surgery and many of the other innovative therapies are combined with surgery. However, cure of glioblastoma has remained elusive because it requires complete destruction of the tumor. Radical surgical ablation is not possible in the brain and even a small residual tumor leads to rapid recurrence that eventually kills the patient. Blood-brain barrier (BBB) comprising brain endothelial cells lining the cerebral microvasculature, limits delivery of drugs to the brain. Even though opening of the BBB in tumor core occurs locally, BBB limits systemic chemotherapy especially at the tumor periphery, where tumor cells invade normal brain structure comprising intact BBB. Comprehensive approaches are necessary to gain maximally from promising targeted therapies. Common methods used for critical evaluation of targeted therapies for glioblastoma include: (1) novel methods for targeted delivery of chemotherapy; (2) strategies for delivery through BBB and blood-tumor barriers; (3) innovations in radiotherapy for selective destruction of tumor; (4) techniques for local destruction of tumor; (5) tumor growth inhibitors; (6) immunotherapy; and (7) cell/gene therapies. Suggestions for improvements in glioblastoma therapy include: (1) controlled targeted delivery of anticancer therapy to glioblastoma through the BBB using nanoparticles and monoclonal antibodies; (2) direct introduction of genetically modified bacteria that selectively destroy cancer cells but spare the normal brain into the remaining tumor after resection; (3) use of better animal models for preclinical testing; and (4) personalized/precision medicine approaches to therapy in clinical trials and translation into practice of neurosurgery and neurooncology. Advances in these techniques suggest optimism for the future management of glioblastoma.

Serum vascular endothelial growth factor receptor-2 and adropin levels in age-related macular degeneration

AIM

To investigate the serum levels of vascular endothelial growth factor receptor-2 (VEGFR-2) and adropin in age-related macular degeneration (AMD) patients.

METHODS

Ninety-eight AMD patients were included in the study. Seventy-eight age- and sex-matched healthy volunteers were recruited as the control group. Fundus florescein angiography and optical coherence tomography were performed to assess the posterior segment details. Serum VEGFR-2 and adropin levels were measured using enzyme-linked immunosorbent assays and compared between the study groups.

RESULTS

AMD group had significantly increased foveal retinal thickness, serum LDL and HDL levels and significantly decreased subfoveal choroidal thickness (P =0.01, 0.047, 0.025 and <0.001, respectively). Serum VEGFR-2 level revealed a significant decrease in AMD patients compared to controls (26.48±6.44 vs 30.42±7.92 ng/mL, P<0.001). There was an insignificant increase in serum adropin level in AMD patients (6.17±3.19 vs 5.79±2.71 ng/mL, P=0.4). Serum level of VEGFR-2 in AMD patients had a significant negative correlation with foveal retinal thickness (r=-0.226, P=0.025) and a significant positive correlation with subfoveal choroidal thickness (r=0.2, P=0.048).

CONCLUSION

The current study demonstrated that the decreased serum VEGFR-2 level may be considered in the development of AMD. Adropin does not seem to play a role in the pathogenesis of AMD.

Redirecting adenovirus tropism by genetic, chemical, and mechanical modification of the adenovirus surface for cancer gene therapy

INTRODUCTION

Despite remarkable advancements, clinical evaluations of adenovirus (Ad)-mediated cancer gene therapies have highlighted the need for improved delivery and targeting.

AREA COVERED

Genetic modification of Ad capsid proteins has been extensively attempted. Although genetic modification enhances the therapeutic potential of Ad, it is difficult to successfully incorporate extraneous moieties into the capsid and the engineering process is laborious. Recently, chemical modification of the Ad surface with nanomaterials and targeting moieties has been found to enhance Ad internalization into the target by both passive and active mechanisms. Alternatively, external stimulus-mediated targeting can result in selective accumulation of Ad in the tumor and prevent dissemination of Ad into surrounding nontarget tissues. In the present review, we discuss various genetic, chemical, and mechanical engineering strategies for overcoming the challenges that hinder the therapeutic efficacy of Ad-based approaches.

EXPERT OPINION

Surface modification of Ad by genetic, chemical, or mechanical engineering strategies enables Ad to overcome the shortcomings of conventional Ad and enhances delivery efficiency through distinct and unique mechanisms that unmodified Ad cannot mimic. However, although the therapeutic potential of Ad-mediated gene therapy has been enhanced by various surface modification strategies, each strategy still possesses innate limitations that must be addressed, requiring innovative ideas and designs.

Combinatorial anti-angiogenic gene therapy in a human malignant mesothelioma model

Anti-angiogenic gene therapy represents a promising strategy for cancer; however, it has rarely been tested in malignant mesothelioma, a highly aggressive tumor associated with asbestos with poor prognosis. In the present study, we investigated whether anti-angiogenic factors such as angiostatin, endostatin and the soluble form of vascular endothelial growth factor receptor 2 (sFlk1) were able to inhibit endothelial cell proliferation via lentivirus-mediated gene transfer into malignant mesothelioma cells in culture. We also assessed whether a dual-agent strategy had greater therapeutic benefit. Human malignant pleural mesothelioma MSTO-211H cells were transduced using lentiviral vectors that individually expressed angiostatin, endostatin and sFlk1 and linked to enhanced green fluorescent protein (EGFP) marker gene expression via an internal ribosome entry site. The lentivirus expressing EGFP alone was used as a control. The resultant cells designated as MSTO-A, MSTO-E, MSTO-F and MSTO-C were confirmed by western blot analysis and fluorescence microscopy to stably express the corresponding proteins. No differences were observed in the in vitro growth rates between any of these cells. However, co-culture of MSTO-A, MSTO-E and MSTO-F showed significant suppression of human umbilical endothelial cell growth in vitro compared with that of MSTO-C. Furthermore, a combination of any two among MSTO-A, MSTO-E and MSTO-F significantly enhanced efficacy. These results suggest that combinatorial anti-angiogenic gene therapy targeting different pathways of endothelial growth factor signaling has the potential for greater therapeutic efficacy than that of a single-agent regimen.

Combination therapy targeting integrins reduces glioblastoma tumor growth through antiangiogenic and direct antitumor activity and leads to activation of the pro-proliferative prolactin pathway

Background

Tumors may develop resistance to specific angiogenic inhibitors via activation of alternative pathways. Therefore, multiple angiogenic pathways should be targeted to achieve significant angiogenic blockade. In this study we investigated the effects of a combined application of the angiogenic inhibitors endostatin and tumstatin in a model of human glioblastoma multiforme.

Results

Inhibitors released by stably transfected porcine aortic endothelial cells (PAE) showed anti-angiogenic activity in proliferation and wound-healing assays with endothelial cells (EC). Interestingly, combination of endostatin and tumstatin (ES + Tum) also reduced proliferation of glioma cells and additionally induced morphological changes and apoptosis in vitro. Microencapsulated PAE-cells producing these inhibitors were applied for local therapy in a subcutaneous glioblastoma model. When endostatin or tumstatin were applied separately, in vivo tumor growth was inhibited by 58% and 50%, respectively. Combined application of ES + Tum, in comparison, resulted in a significantly more pronounced inhibition of tumor growth (83%). cDNA microarrays of tumors treated with ES + Tum revealed an up-regulation of prolactin receptor (PRLR). ES + Tum-induced up-regulation of PRLR in glioma cells was also found in in vitro. Moreover, exogenous PRLR overexpression in vitro led to up-regulation of its ligand prolactin and increased proliferation suggesting a functional autocrine growth loop in these cells.

Conclusion

Our data indicate that integrin-targeting factors endostatin and tumstatin act additively by inhibiting glioblastoma growth via reduction of vessel density but also directly by affecting proliferation and viability of tumor cells. Treatment with the ES + Tum-combination activates the PRLR pro-proliferative pathway in glioblastoma. Future work will show whether the prolactin signaling pathway represents an additional target to improve therapeutic strategies in this entity.

Strategies in gene therapy for glioblastoma

Glioblastoma (GBM) is the most aggressive form of brain cancer, with a dismal prognosis and extremely low percentage of survivors. Novel therapies are in dire need to improve the clinical management of these tumors and extend patient survival. Genetic therapies for GBM have been postulated and attempted for the past twenty years, with variable degrees of success in pre-clinical models and clinical trials. Here we review the most common approaches to treat GBM by gene therapy, including strategies to deliver tumor-suppressor genes, suicide genes, immunomodulatory cytokines to improve immune response, and conditionally-replicating oncolytic viruses. The review focuses on the strategies used for gene delivery, including the most common and widely used vehicles (i.e., replicating and non-replicating viruses) as well as novel therapeutic approaches such as stem cell-mediated therapy and nanotechnologies used for gene delivery. We present an overview of these strategies, their targets, different advantages, and challenges for success. Finally, we discuss the potential of gene therapy-based strategies to effectively attack such a complex genetic target as GBM, alone or in combination with conventional therapy.

Disruption of components of vascular endothelial growth factor angiogenic signalling system in metabolic syndrome. Findings from a study conducted in rural Bangladeshi women

Metabolic syndrome (MetS) is associated with impaired angiogenesis, a process that is chiefly regulated by vascular endothelial growth factor (VEGF) upon binding to its specific receptors, VEGF-R1 and VEGF-R2. The purpose of the present study was to assess trends or patterns in plasma levels of VEGF and its soluble receptors in subjects with (MetS) or without (non-MetS) MetS; and further examine their association with clinical or metabolic parameters using a subpopulation of South Asian country. A total of 1,802 rural Bangladeshi women aged ≥15 years were studied using a population-based cross-sectional survey. Plasma levels of VEGF were found to be significantly increased (MetS vs. non-MetS: 483.9 vs. 386.9, p<0.001), whereas, the soluble forms of VEGF receptors, sVEGF-R1 and sVEGF-R2, were significantly decreased in subjects with Mets (sVEGF-R1, MetS vs. non-MetS: 512.5 vs. 631.3, p<0.001; sVEGF-R2, MetS vs. non-MetS: 9,302.8 vs. 9,787.4, p=0.004). After adjustment for age and all potential variables, multiple regression analysis revealed that plasma levels of VEGF had significant positive association with blood glucose (p = 0.019) and body mass index (p = 0.007). We also found that mean plasma levels of VEGF increased in direct proportion to levels of MetS components. The present study is the first ever to demonstrate a positive association between trends in levels of plasma VEGF and MetS using a large sample size from South Asia. The association between plasma VEGF and MetS needs further investigations in order to clearly decipher the clinical predictive value and accuracy of plasma VEGF in MetS.

The metabolite 3-hydroxiglutaric acid effectively reduces glioblastoma growth in vivo by affecting the structural integrity of tumor vasculature

3-Hydroxiglutaric acid (3-OH-GA) is a disease-specific metabolite that accumulates in tissues and body fluids of patients with Glutaric aciduria type I (GAI) and has been associated with vascular abnormalities in these kindreds. Here, we demonstrate that 3-OH-GA also affects the integrity of tumor vessels leading to tumor growth inhibition in a subcutaneous model of human glioblastoma multiforme (GBM). This effect correlated with a marked decrease of VE-Cadherin expression in endothelium of 3-OH-GA-treated tumors. Furthermore, in vitro observations indicated also a direct effect of 3-OH-GA in glioma cells that showed defective mitosis and significant proliferation inhibition. In summary, the GAI-specific metabolite 3-OH-GA significantly inhibited growth of GBM xenografts by affecting the structural integrity of tumor blood vessels and in addition by causing defective mitosis and proliferation inhibition of tumor cells.

Anti-angiogenic gene therapy in the treatment of malignant gliomas

More than four decades ago, Dr. Judah Folkman hypothesized that angiogenesis was a critical process in tumor growth. Since that time, there have been significant advances in understanding tumor biology and groundbreaking research in cancer therapy that have validated his hypothesis. However, in spite of extensive research, glioblastoma multiforme (GBM), the most common and malignant primary brain tumor, has gained little in the way of improved median survival. There have been several angiogenesis targets that have resulted in drugs that are in clinical trials or FDA approved for clinical use in several cancers. GBM is a highly angiogenic tumor and several drugs are showing promise in clinical trials with one (bevacizumab), clinically approved for use. We will review several possible angiogenic targets in GBM as well as the vector methodologies used for delivery. In addition, GBMs present several therapeutic challenges related to structure, tumor immune microenvironment and resistance to angiogenesis. To overcome these challenges will require novel approaches to improve therapeutic gene expression and vector biodistribution in the glioma.

Regulation of soluble VEGFR-2 secreted by microvascular endothelial cells derived from human BPH

BACKGROUND

Recently, it was reported that the soluble vascular endothelial growth factor receptor-2 (sVEGFR-2) is secreted by microvascular endothelial cells from human BPH (HPECs). The purpose of this study was to investigate the modulation of sVEGFR-2 by common endothelial cell stimulators. In addition, the physiological role of sVEGFR-2 with regard to the VEGF-stimulated proliferation of HPEC was investigated.

METHODS

HPECs were isolated and cultured from fresh BPH tissue. After the incubation of HPECs either with adenosine triphosphate (ATP), interleukin (IL)-6, IL-8 or IL-12, the secretion of sVEGFR-2 was measured by enzyme-linked immunosorbent assay. For measurement of HPEC proliferation influenced by sVEGFR-2, VEGF-stimulated HPEC was cultured with/without sVEGFR-2. Cell proliferation was assessed with the Alamar Blue method.

RESULTS

The sVEGFR-2 secretion was increased by ATP and decreased by IL-12 and IL-8, respectively. IL-6 did not show any significant effect on sVEGFR-2 secretion of HPECs. HPEC proliferation was significantly inhibited by sVEGFR-2.

CONCLUSIONS

In this study, our data suggest that the secretion of sVEGFR-2 by microvascular endothelial cells from prostate origin is influenced by multiple endothelial cell stimulators. Furthermore, our data suggest that sVEGFR-2 acts as an antiangiogenic factor.

Gene therapy and targeted toxins for glioma

The most common primary brain tumor in adults is glioblastoma. These tumors are highly invasive and aggressive with a mean survival time of 15-18 months from diagnosis to death. Current treatment modalities are unable to significantly prolong survival in patients diagnosed with glioblastoma. As such, glioma is an attractive target for developing novel therapeutic approaches utilizing gene therapy. This review will examine the available preclinical models for glioma including xenographs, syngeneic and genetic models. Several promising therapeutic targets are currently being pursued in pre-clinical investigations. These targets will be reviewed by mechanism of action, i.e., conditional cytotoxic, targeted toxins, oncolytic viruses, tumor suppressors/oncogenes, and immune stimulatory approaches. Preclinical gene therapy paradigms aim to determine which strategies will provide rapid tumor regression and long-term protection from recurrence. While a wide range of potential targets are being investigated preclinically, only the most efficacious are further transitioned into clinical trial paradigms. Clinical trials reported to date are summarized including results from conditionally cytotoxic, targeted toxins, oncolytic viruses and oncogene targeting approaches. Clinical trial results have not been as robust as preclinical models predicted; this could be due to the limitations of the GBM models employed. Once this is addressed, and we develop effective gene therapies in models that better replicate the clinical scenario, gene therapy will provide a powerful approach to treat and manage brain tumors.

Inhibition of ovarian cancer by RGD-P125A-endostatin-Fc fusion proteins

Previous studies have shown that a single point mutation in endostatin at position 125 (P125A) can improve the biological activity of endostatin. Addition of an integrin-targeting moiety, R-G-D, resulted in better localization to tumor vasculature and improved the antiangiogenic activity of endostatin. Because endostatin has relatively shorter serum half-life, frequent dosing was required for inhibiting tumor growth. In our study, we have genetically fused RGD-P125A-endostatin to Fc of IgG4 isotype and evaluated its antiangiogenic and antitumor effects in athymic mice. Two genetic constructs were made, RGD-P125A-endostatin-Fc (RE-Fc) and P125A-endostatin-RGD-Fc (ER-Fc). Both constructs were cloned and expressed in mammalian cells. Purified fusion proteins inhibited endothelial cell migration and proliferation better than yeast-derived P125A-endostatin. Both RE-Fc and ER-Fc inhibited ovarian cancer growth and were found to be as effective as Bevacizumab treatment. Fusion protein showed marked increased half-life. Combination treatment with Bevacizumab and ER-Fc showed additive inhibition of ovarian cancer growth. These studies demonstrate that genetic fusion with human IgG4-Fc increases the half-life of P125A-endostatin and can be used along with Bevacizumab to improve antiangiogenic and antitumor activities.

Sitimagene ceradenovec: a gene-based drug for the treatment of operable high-grade glioma

The field of gene therapy for malignant glioma has made important advances since the first gene transfer studies were performed 20 years ago. Multiple Phase I/II trials and two Phase III trials have been performed and have demonstrated the feasibility and safety of intratumoral vector delivery in the brain. Sitimagene ceradenovec is an adenoviral vector encoding the herpes simplex thymidine kinase gene, developed by Ark Therapeutics Group plc (UK and Finland) for the treatment of patients with operable high-grade glioma. In preclinical and Phase I/II clinical studies, sitimagene ceradenovec exhibited a significant increase in survival. Although the preliminary results of a Phase III clinical study demonstrated a significant positive effect of sitimagene ceradenovec treatment on time to reintervention or death when compared with standard care treatment (hazard ratio: 1.43; 95% CI: 1.06-1.93; p < 0.05), the European Committee for Medicinal Products for Human Use did not consider the data to provide sufficient evidence of clinical benefit. Further clinical evaluation, powered to demonstrate a benefit on a robust end point, is required. This article focuses on sitimagene ceradenovec and provides an overview of the developments in the field of gene therapy for malignant glioma.

AAV-P125A-endostatin and paclitaxel treatment increases endoreduplication in endothelial cells and inhibits metastasis of breast cancer

Endostatin potentiates the antimitotic effects of paclitaxel (taxol) on endothelial cells (ECs). P125A-endostatin and taxol-treated ECs showed multipolar spindles and nuclear lobulation, leading to mitotic catastrophe and cell death. Induction of nuclear abnormalities was found to be dependent on β-catenin levels as wnt-mediated overexpression of β-catenin reversed the changes in nuclear morphology. These results prompted us to investigate whether antiangiogenic gene therapy and paclitaxel chemotherapy can synergistically inhibit angiogenesis and tumor growth. We first determined the effect of combination treatment in a transgenic mouse model of breast cancer. Intramuscular injection of recombinant adeno-associated virus type-2 virus induced sustained expression of P125A-endostatin. In vivo studies showed that combination therapy inhibited mammary cancer growth, delayed the onset of multifocal mammary adenocarcinomas, decreased tumor angiogenesis and increased survival in treated mice. In a second model, female athymic mice were orthotopically transplanted with a metastatic human breast cancer cell line. Antiangiogenic gene therapy in combination with paclitaxel inhibited tumor angiogenesis and lung/lymph-node metastasis in this model. These studies demonstrate cooperation between endostatin gene therapy and chemotherapy to inhibit tumor initiation, growth and metastasis.

Soluble forms of VEGF receptor-1 and -2 promote vascular maturation via mural cell recruitment

Two soluble forms of vascular endothelial growth factor (VEGF) receptors, sVEGFR-1 and sVEGFR-2, are physiologically released and overproduced in some pathologies. They are known to act as anti-VEGF agents. Here we report that these soluble receptors contribute to vessel maturation by mediating a dialogue between endothelial cells (ECs) and mural cells that leads to blood vessel stabilization. Through a multidisciplinary approach, we provide evidence that these soluble VEGF receptors promote mural cell migration through a paracrine mechanism involving interplay in ECs between VEGF/VEGFR-2 and sphingosine-1-phosphate type-1 (S1P)/S1P1 pathways that leads to endothelial nitric oxyde synthase (eNOS) activation. This new paradigm is supported by the finding that sVEGFR-1 and -2 perform the following actions: 1) induce an eNOS-dependent outgrowth of a mural cell network in an ex vivo model of angiogenesis, 2) increase the mural cell coverage of neovessels in vitro and in vivo, 3) promote mural cell migration toward ECs, and 4) stimulate endothelial S1P1 overproduction and eNOS activation that promote the migration and the recruitment of neighboring mural cells. These findings provide new insights into mechanisms regulating physiological and pathological angiogenesis and vessel stabilization.

Viruses, gene therapy and stem cells for the treatment of human glioma

Cancer gene therapy is based on the transfer of genetic material to cancer cells to modify a normal or abnormal cellular function, or to induce cell death. Modified viruses or stem cells have been used as carriers to transfer the genetic material to cancer cells avoiding trafficking through normal cells. However, although the current vectors have been successful in delivering genes in vitro and in vivo, little has been achieved with human cerebral gliomas. Poor transduction efficiency of viruses in human glioma cells and limited spread and distribution to the tumor limits our current expectations for successful gene therapy of central nervous system cancer until and if effective transfer vehicles are available. Nevertheless, continuing research in better vector development may overcome these limitations and offer a therapeutic advantage over the standard therapies for glioma.

Secretion of soluble VEGF receptor 2 by microvascular endothelial cells derived by human benign prostatic hyperplasia

Vascular endothelial growth factor (VEGF) is one of the most potent mitogenic factors stimulating both prostate endothelial and prostate epithelial cells. Recently, some studies reported on the endothelial secretion of a soluble VEGF receptor 2 (sVEGFR-2) that modifies the free VEGF concentration by binding VEGF. For the first time in this study, we report on the secretion and the regulation of the secretion of sVEGFR-2 by microvascular endothelial cells derived from the tissue of human benign prostatic hyperplasia (HPEC). HPEC were isolated and cultured from fresh prostate tissue. The prostate epithelial cell line BPH-1 was cultured with the supernatant of the HPEC cell culture (fractioned by fast protein liquid chromatography) and the VEGF concentration was subsequently measured. HPEC were incubated with VEGF or tumor necrosis factor alpha (TNF-alpha). Afterwards, the concentration of sVEGFR-2 in the supernatant of unstimulated and stimulated HPEC was measured by ELISA. HPEC showed a typical endothelial morphology. Under cell culture conditions sVEGFR-2 binds VEGF: The measured VEGF concentration in the supernatant of BPH-1 cells was reduced when the fractions of HPEC conditioned medium with the highest sVEGFR-2 concentration were incubated with the BPH-1 cells. The sVEGFR-2 secretion of HPEC was stimulated by VEGF and TNF-alpha. For the first time we report on the secretion of sVEGFR-2 by microvascular endothelial cells of prostate origin. The secretion of sVEGFR-2 by HPEC was stimulated by VEGF and TNF-alpha. Our data suggest that sVEGFR-2 secreted by prostate endothelial cells could modify the effect of VEGF on prostate endothelial and prostate epithelial cells.