r84, a Novel Therapeutic Antibody against Mouse and Human VEGF with Potent Anti-Tumor Activity and Limited Toxicity Induction

Vascular endothelial growth factor (VEGF) is critical for physiological and pathological angiogenesis. Within the tumor microenvironment, VEGF functions as an endothelial cell survival factor, permeability factor, mitogen, and chemotactic agent. The majority of these functions are mediated by VEGF-induced activation of VEGF receptor 2 (VEGFR2), a high affinity receptor tyrosine kinase expressed by endothelial cells and other cell types in the tumor microenvironment. VEGF can also ligate other cell surface receptors including VEGFR1 and neuropilin-1 and -2. However, the importance of VEGF-induced activation of these receptors in tumorigenesis is still unclear. We report the development and characterization of r84, a fully human monoclonal antibody that binds human and mouse VEGF and selectively blocks VEGF from interacting with VEGFR2 but does not interfere with VEGF∶VEGFR1 interaction. Selective blockade of VEGF binding to VEGFR2 by r84 is shown through ELISA, receptor binding assays, receptor activation assays, and cell-based functional assays. Furthermore, we show that r84 has potent anti-tumor activity and does not alter tissue histology or blood and urine chemistry after chronic high dose therapy in mice. In addition, chronic r84 therapy does not induce elevated blood pressure levels in some models. The ability of r84 to specifically block VEGF∶VEGFR2 binding provides a valuable tool for the characterization of VEGF receptor pathway activation during tumor progression and highlights the utility and safety of selective blockade of VEGF-induced VEGFR2 signaling in tumors

Appetite Enhancement and Weight Gain by Peripheral Administration of TrkB Agonists in Non-Human Primates

Loss of function mutations in the receptor tyrosine kinase TrkB pathway resulted in hyperphagia and morbid obesity in human and rodents. Conversely, peripheral or central stimulation of TrkB by its natural ligands BDNF or NT4 reduced body weight and food intake in mice, supporting the idea that TrkB is a key anorexigenic signal downstream of the melanocortin-4 receptor (Mc4r) system. Here we show that in non-human primates TrkB agonists were anorexigenic when applied centrally, but surprisingly orexigenic, leading to gain in appetite, body weight, fat deposits and serum leptin levels, when given peripherally. The orexigenic and pro-obesity effects of peripherally administered TrkB agonists appear to be dose dependent, not associated with fluid retention nor with evidence of receptor down regulation. Our findings revealed that TrkB signaling exerts dual control on energy homeostasis in the primates that could be targeted for the treatment of either wasting disorders or obesity

Phloroglucinol Inhibits the Bioactivities of Endothelial Progenitor Cells and Suppresses Tumor Angiogenesis in LLC-Tumor-Bearing Mice

Background: There is increasing evidence that phloroglucinol, a compound from Ecklonia cava, induces the apoptosis of cancer cells, eventually suppressing tumor angiogenesis. Methodology/Principal Findings: This is the first report on phloroglucinol’s ability to potentially inhibit the functional bioactivities of endothelial progenitor cells (EPCs) and thereby attenuate tumor growth and angiogenesis in the Lewis lung carcinoma (LLC)-tumor-bearing mouse model. Although Phloroglucinol did not affect their cell toxicity, it specifically inhibited vascular endothelial growth factor (VEGF) dependent migration and capillary-like tube formation of EPCs. Our matrigel plug assay clearly indicated that orally injected phloroglucinol effectively disrupts VEGF-induced neovessel formation. Moreover, we demonstrated that when phloroglucinol is orally administered, it significantly inhibits tumor growth and angiogenesis as well as CD45 2 /CD34 + progenitor mobilization into peripheral blood in vivo in the LLC-tumorbearing mouse model. Conclusions/Significance: These results suggest a novel role for phloroglucinol: Phloroglucinol might be a modulator of circulating EPC bioactivities, eventually suppressing tumorigenesis. Therefore, phloroglucinol might be a candidat

Centrally Administered Pertussis Toxin Inhibits Microglia Migration to the Spinal Cord and Prevents Dissemination of Disease in an EAE Mouse Model

Background: Experimental autoimmune encephalomyelitis (EAE) models are important vehicles for studying the effect of infectious elements such as Pertussis toxin (PTx) on disease processes related to acute demyelinating encephalomyelitis (ADEM) or multiple sclerosis (MS). PTx has pleotropic effects on the immune system. This study was designed to investigate the effects of PTx administered intracerebroventricularly (icv) in preventing downstream immune cell infiltration and demyelination of the spinal cord. Methods and Findings: EAE was induced in C57BL/6 mice with MOG35–55. PTx icv at seven days post MOG immunization resulted in mitigation of clinical motor symptoms, minimal T cell infiltration, and the marked absence of axonal loss and demyelination of the spinal cord. Integrity of the blood brain barrier was compromised in the brain whereas spinal cord BBB integrity remained intact. PTx icv markedly increased microglia numbers in the brain preventing their migration to the spinal cord. An in vitro transwell study demonstrated that PTx inhibited migration of microglia. Conclusion: Centrally administered PTx abrogated migration of microglia in EAE mice, limiting the inflammatory cytokine milieu to the brain and prevented dissemination of demyelination. The effects of PTx icv warrants further investigation and provides an attractive template for further study regarding the pleotropic effects of infectious elements such as PTx in th

In Vivo Evolution of Tumor-Derived Endothelial Cells

The growth of a malignant tumor beyond a certain, limited size requires that it first develop an independent blood supply. In addition to providing metabolic support, this neovasculature also allows tumor cells to access the systemic circulation, thus facilitating metastatic dissemination. The neovasculature may originate either from normal blood vessels in close physical proximity to the tumor and/or from the recruitment of bone marrow-derived endothelial cell (EC) precursors. Recent studies have shown that human tumor vasculature ECs may also arise directly from tumor cells themselves and that the two populations have highly similar or identical karyotypes. We now show that, during the course of serial in vivo passage, these tumor-derived ECs (TDECs) progressively acquire more pronounced EC-like properties. These include higher-level expression of EC-specific genes and proteins, a greater capacity for EC-like behavior in vitro, and a markedly enhanced propensity to incorporate into the tumor vasculature. In addition, both vessel density and size are significantly increased in neoplasms derived from mixtures of tumor cells and serially passaged TDECs. A comparison of early- and late-passage TDECs using whole-genome single nucleotide polymorphism profiling showed the latter cells to have apparently evolved by a process of clonal expansion of a population with a distinct pattern of interstitial chromosomal gains and losses affecting a relatively small number of genes. The majority of these have established roles in vascular development, tumor suppression or epithelial-mesenchymal transition. These studies provide direct evidence that TDECs have a strong evolutionary capacity as a result of their inherent genomic instability. Consequently such cells might be capable of escaping anti-angiogenic cancer therapies by generating resistant populations

Treatment in advanced colorectal cancer: what, when and how?

Treatment of advanced colorectal cancer (CRC) increasingly requires a multidisciplinary approach and multiple treatment options add to the complexity of clinical decision-making. Recently novel targeted therapy against angiogenesis and epidermal growth factor receptor completed a plethora of phase III studies. The addition of bevacizumab to chemotherapy improved the efficacy over chemotherapy alone in both first and second line settings, although the magnitude of benefit may not be as great when a more optimal chemotherapy platform is used. Studies performed thus far did not address conclusively whether bevacizumab should be continued in subsequent lines of treatment. Anti-angiogenesis tyrosine kinase inhibitors have not shown any additional benefit over chemotherapy alone so far. Although some benefits were seen with cetuximab in all settings of treating advanced CRC, K-ras mutation status provides an important determinant of who would not benefit from such a treatment. Caution should be exercised in combining anti-angiogenesis with anti-EGFR strategy until further randomised data become available. In this review, we have focused on the implications of these trial results on the everyday management decisions of treating advanced CRC

More is less -- combining targeted therapies in metastatic colorectal cancer.

Item does not contain fulltextTargeted agents directed at VEGF, such as bevacizumab, and EGFR, such as cetuximab and panitumumab, have become part of the standard treatment of metastatic colorectal cancer. Only a subset of patients seem to benefit from such treatment, and varying results have been observed when different lines of treatment are used in combination with different cytotoxic drugs. Preclinical and early clinical data have shown promising results for the combination of anti-VEGF and anti-EGFR treatment. However, two recent phase III trials, CAIRO2 and PACCE, have shown a detrimental effect of adding an anti-EGFR antibody to standard chemotherapy plus bevacizumab. We discuss issues that may explain these unexpected results