The Experts below are selected from a list of 27 Experts worldwide ranked by ideXlab platform
Nicholas P.j. Brindle - One of the best experts on this subject based on the ideXlab platform.
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Vascular Endothelial Growth Factor Modulates the Tie-2:Tie-1 Receptor Complex
Microvascular research, 2002Co-Authors: Achilleas C. Tsiamis, Paul N. Morris, Marie B. Marron, Nicholas P.j. BrindleAbstract:The Receptor tyrosine kinase Tie-1 is expressed predominantly in endothelial cells where it physically associates with the related Receptor Tie-2. Positive signalling through Tie-2 is associated with microvessel stability and suppression of this signal is thought to be required for vascular endothelial growth factor (VEGF)-induced microvessel remodelling or growth. Here we examine the effects of VEGF on Tie-1 and the Tie-2:Tie-1 complex. We show that VEGF induces generation of the Tie-1 endodomain and loss of the full-length Receptor. The effects of VEGF on endodomain formation are not suppressed by inhibitors of protein kinase C and do not involve the nitric oxide signalling pathway. Tyrosine kinase inhibitors, in contrast, do abolish endodomain generation in response to the endothelial growth factor. VEGF stimulation of cells does not cause dissociation of the Tie-2:Tie-1 complex; rather the complex is converted to a form comprising the full-length-Tie-2 and Tie-1 endodomain. VEGF can therefore switch the Tie-2:Tie-1 complex between two different forms in endothelial cells. The ability of VEGF to modulate Tie-1 and the Tie-2:Tie-1 complex provides a mechanism whereby this initiator of vessel growth and remodelling can directly modulate Receptors involved in vessel stabilization. Such cross-talk is likely to be important in the coordinate control of blood vessel formation during development and in postnatal angiogenesis.
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Characterization and regulation of the Receptor tyrosine kinase Tie-1 in platelets.
Journal of vascular research, 2000Co-Authors: Achilleas C. Tsiamis, Paul D. Hayes, Helen Box, Alison H. Goodall, Peter R.f. Bell, Nicholas P.j. BrindleAbstract:The Receptor tyrosine kinase Tie-1 is expressed predominantly on endothelial cells where it has an essential role in blood vessel formation. Targeted disruption of the Tie-1 gene results in a lethal phenotype with severe disruption to the normal integrity of the vasculature. In an examination of Tie-1 in vivo, we observed a significant pool of the Receptor present in the circulation associated with the platelet fraction. Western blotting reveals the platelet form of Tie-1 to be a protein of approximately 110 kDa, this contrasts with the 135/125-kDa doublet found in endothelial cells. Platelet activation results in increased surface expression of Tie-1. The closely related Receptor tyrosine kinase Tie-2/Tek is not present in platelets. Endothelial Tie-1 undergoes metalloprotease-mediated ectodomain cleavage in response to phorbol ester and other agonists. Tie-1 cleavage leads to release of the extracellular domain and generation of a cell-associated intracellular domain with signalling capacity. The potential for cleavage was investigated in platelets. In contrast to endothelial Tie-1, phorbol ester does not stimulate truncation of the platelet Receptor, suggesting these cells lack one or more components of the regulated metalloprotease system controlling Tie-1. These data demonstrate the Tie-1 Receptor tyrosine kinase is present on platelets and its surface expression is regulated. Furthermore, platelet Tie-1 differs significantly from the endothelial Receptor. Platelet Tie-1 has the potential to modulate endothelial function by competing for any Tie ligands and may have signalling roles important in controlling aspects of platelet behaviour.
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Tie-1 Receptor tyrosine kinase endodomain interaction with SHP2: potential signalling mechanisms and roles in angiogenesis.
Advances in experimental medicine and biology, 2000Co-Authors: Marie B. Marron, Nicholas P.j. Brindle, David P. Hughes, M.j. Mccarthy, Eleanor R. BeaumontAbstract:The endothelial Receptor tyrosine kinase plays an essential role in vascular development where it is thought to be required for vessel maturation and stabilization. The ligands responsible for activating Tie-1, its signalling pathways and specific cellular functions are however not known. As with some other Receptor tyrosine kinases, Tie-1 is subject to extracellular proteolytic cleavage generating a membrane bound Receptor fragment comprising the intracellular and transmembrane domains. Here we examine the signalling potential of this Tie-1 endodomain. We show that the Tie-1 endodomain has poor ability to induce tyrosine phosphorylation. However, on formation the endodomain physically associates with a number of tyrosine phosphorylated signalling intermediates including the tyrosine phosphatase and adaptor protein SHP2. The assembly of this multimolecular complex is consistent with the endodomain having a ligand-independent signalling role in the endothelial cell. The potential roles of ectodomain cleavage and cleavage activated signalling in regulating microvessel stability in angiogenesis, vessel remodelling and regression are considered.
Achilleas C. Tsiamis - One of the best experts on this subject based on the ideXlab platform.
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Vascular Endothelial Growth Factor Modulates the Tie-2:Tie-1 Receptor Complex
Microvascular research, 2002Co-Authors: Achilleas C. Tsiamis, Paul N. Morris, Marie B. Marron, Nicholas P.j. BrindleAbstract:The Receptor tyrosine kinase Tie-1 is expressed predominantly in endothelial cells where it physically associates with the related Receptor Tie-2. Positive signalling through Tie-2 is associated with microvessel stability and suppression of this signal is thought to be required for vascular endothelial growth factor (VEGF)-induced microvessel remodelling or growth. Here we examine the effects of VEGF on Tie-1 and the Tie-2:Tie-1 complex. We show that VEGF induces generation of the Tie-1 endodomain and loss of the full-length Receptor. The effects of VEGF on endodomain formation are not suppressed by inhibitors of protein kinase C and do not involve the nitric oxide signalling pathway. Tyrosine kinase inhibitors, in contrast, do abolish endodomain generation in response to the endothelial growth factor. VEGF stimulation of cells does not cause dissociation of the Tie-2:Tie-1 complex; rather the complex is converted to a form comprising the full-length-Tie-2 and Tie-1 endodomain. VEGF can therefore switch the Tie-2:Tie-1 complex between two different forms in endothelial cells. The ability of VEGF to modulate Tie-1 and the Tie-2:Tie-1 complex provides a mechanism whereby this initiator of vessel growth and remodelling can directly modulate Receptors involved in vessel stabilization. Such cross-talk is likely to be important in the coordinate control of blood vessel formation during development and in postnatal angiogenesis.
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Characterization and regulation of the Receptor tyrosine kinase Tie-1 in platelets.
Journal of vascular research, 2000Co-Authors: Achilleas C. Tsiamis, Paul D. Hayes, Helen Box, Alison H. Goodall, Peter R.f. Bell, Nicholas P.j. BrindleAbstract:The Receptor tyrosine kinase Tie-1 is expressed predominantly on endothelial cells where it has an essential role in blood vessel formation. Targeted disruption of the Tie-1 gene results in a lethal phenotype with severe disruption to the normal integrity of the vasculature. In an examination of Tie-1 in vivo, we observed a significant pool of the Receptor present in the circulation associated with the platelet fraction. Western blotting reveals the platelet form of Tie-1 to be a protein of approximately 110 kDa, this contrasts with the 135/125-kDa doublet found in endothelial cells. Platelet activation results in increased surface expression of Tie-1. The closely related Receptor tyrosine kinase Tie-2/Tek is not present in platelets. Endothelial Tie-1 undergoes metalloprotease-mediated ectodomain cleavage in response to phorbol ester and other agonists. Tie-1 cleavage leads to release of the extracellular domain and generation of a cell-associated intracellular domain with signalling capacity. The potential for cleavage was investigated in platelets. In contrast to endothelial Tie-1, phorbol ester does not stimulate truncation of the platelet Receptor, suggesting these cells lack one or more components of the regulated metalloprotease system controlling Tie-1. These data demonstrate the Tie-1 Receptor tyrosine kinase is present on platelets and its surface expression is regulated. Furthermore, platelet Tie-1 differs significantly from the endothelial Receptor. Platelet Tie-1 has the potential to modulate endothelial function by competing for any Tie ligands and may have signalling roles important in controlling aspects of platelet behaviour.
Marie B. Marron - One of the best experts on this subject based on the ideXlab platform.
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Vascular Endothelial Growth Factor Modulates the Tie-2:Tie-1 Receptor Complex
Microvascular research, 2002Co-Authors: Achilleas C. Tsiamis, Paul N. Morris, Marie B. Marron, Nicholas P.j. BrindleAbstract:The Receptor tyrosine kinase Tie-1 is expressed predominantly in endothelial cells where it physically associates with the related Receptor Tie-2. Positive signalling through Tie-2 is associated with microvessel stability and suppression of this signal is thought to be required for vascular endothelial growth factor (VEGF)-induced microvessel remodelling or growth. Here we examine the effects of VEGF on Tie-1 and the Tie-2:Tie-1 complex. We show that VEGF induces generation of the Tie-1 endodomain and loss of the full-length Receptor. The effects of VEGF on endodomain formation are not suppressed by inhibitors of protein kinase C and do not involve the nitric oxide signalling pathway. Tyrosine kinase inhibitors, in contrast, do abolish endodomain generation in response to the endothelial growth factor. VEGF stimulation of cells does not cause dissociation of the Tie-2:Tie-1 complex; rather the complex is converted to a form comprising the full-length-Tie-2 and Tie-1 endodomain. VEGF can therefore switch the Tie-2:Tie-1 complex between two different forms in endothelial cells. The ability of VEGF to modulate Tie-1 and the Tie-2:Tie-1 complex provides a mechanism whereby this initiator of vessel growth and remodelling can directly modulate Receptors involved in vessel stabilization. Such cross-talk is likely to be important in the coordinate control of blood vessel formation during development and in postnatal angiogenesis.
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Tie-1 Receptor tyrosine kinase endodomain interaction with SHP2: potential signalling mechanisms and roles in angiogenesis.
Advances in experimental medicine and biology, 2000Co-Authors: Marie B. Marron, Nicholas P.j. Brindle, David P. Hughes, M.j. Mccarthy, Eleanor R. BeaumontAbstract:The endothelial Receptor tyrosine kinase plays an essential role in vascular development where it is thought to be required for vessel maturation and stabilization. The ligands responsible for activating Tie-1, its signalling pathways and specific cellular functions are however not known. As with some other Receptor tyrosine kinases, Tie-1 is subject to extracellular proteolytic cleavage generating a membrane bound Receptor fragment comprising the intracellular and transmembrane domains. Here we examine the signalling potential of this Tie-1 endodomain. We show that the Tie-1 endodomain has poor ability to induce tyrosine phosphorylation. However, on formation the endodomain physically associates with a number of tyrosine phosphorylated signalling intermediates including the tyrosine phosphatase and adaptor protein SHP2. The assembly of this multimolecular complex is consistent with the endodomain having a ligand-independent signalling role in the endothelial cell. The potential roles of ectodomain cleavage and cleavage activated signalling in regulating microvessel stability in angiogenesis, vessel remodelling and regression are considered.
Luis A. G. Da Cruz - One of the best experts on this subject based on the ideXlab platform.
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Preclinical development of huARH460-16-2, a humanized antibody to the CD44 cancer stem cell target
Cancer Research, 2008Co-Authors: Luis A. G. Da Cruz, Ningping Feng, Daad Sayegh, Susan Hahn, Nadine Chouinard, Daniel S. Pereira, Daniel B. Rubinstein, David YoungAbstract:3975 CD44 has been identified on cancer stem cells in several solid and liquid tumors (breast, colon, prostate, pancreatric cancer and AML) where it is thought to play key roles in tumor maintenance, adhesion, migration and invasion. A monoclonal antibody targeting CD44, ARH460-16-2, was generated using the ARIUS’ FunctionFIRST™ platform. Murine and chimeric ARH460-16-2 (chARH460-16-2) demonstrated potent anti-tumor efficacy in models of human breast (CD44+CD24-/lo), liver and prostate cancer as well as AML. With respect to mechanism of action, chARH460-16-2 induced apoptosis and suppressed phosphorylation of the Tie-1 Receptor tyrosine kinase in breast cancer cells. Immunohistochemistry showed that the epitope for ARH460-16-2 is present on the majority of human adenocarcinomas including breast, prostate, colon, and liver cancers. Limited binding to normal human tissues was observed, predominantly to myeloid cells in bone marrow, with no binding observed to erythroid cells, megakaryocytes, endothelium, fibroblasts, smooth muscle, eye, heart, liver, ovary and colon epithelium. The binding pattern was not substantially different in cynomolgus monkey tissues, although some differences in intensity were seen. A dose-ranging toxicology study was carried out in cynomolgus monkeys with chARH460-16-2. In the first phase, monkeys (2 per group) were given a single 1 hr infusion of 10, 30 or 95 (high dose) mg/kg chARH460-16-2. A second cohort of 3 monkeys was infused with 25 mg/kg chARH460-16-2 once per week for 2 doses. There were no drug related effects on clinical chemistry parameters, coagulation, or hematology (blood cell counts or morphology). In one of the high-dose treated monkeys, and in 3 monkeys of the second cohort there was transient reddening of the skin which resolved after a few days. Histopathology of the second cohort, sacrificed 15 days after the first dose, revealed no findings in the skin of 2 tested animals, while the third had a crusting dermatitis. In all cases there no findings in bone marrow smears or in lung sections. A CHO cell line producing the humanized version of the antibody (huARH460-16-2) has been developed. huARH460-16-2 is equivalent to chARH460-16-2 using the following criteria: affinity to recombinant CD44 by BiaCore and ELISA, FACS binding to cancer cell lines, ability to induce apoptosis, and ability to induce tumor regression in the established MDA-MB-231 breast cancer model. In addition, the EC50 of huARH460-16-2 binding to lymphocytes, monocytes and granulocytes of human and cynomolgus monkeys was similar as assessed by FACS. Taken together, these results support the clinical development of a humanized therapeutic monoclonal antibody targeting the cancer stem cell antigen CD44
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Chimeric and humanized versions of the anti-CD44 monoclonal antibody ARH460-16-2 have potent anti-tumor efficacy in established models of human breast and metastatic liver cancer
Molecular Cancer Therapeutics, 2007Co-Authors: Luis A. G. Da Cruz, Ningping Feng, Terence Lee, Daad Sayegh, Baldwin Mak, Ming Wang, Mitra Amoozgar, Susan Hahn, Daniel Pereira, Helen FindlayAbstract:A74 CD44 is a widely distributed protein implicated in multiple normal physiological and pathological events including co-stimulation of T-lymphocytes, leukocyte re-circulation and tumor metastasis. CD44 interacts with hyaluronic acid and other extracellular matrix components and metalloproteases, and recently has been shown to be expressed in tumor cancer stem cells from several cancer types, including breast, colon, prostate, pancreas and AML. The association of CD44 with cancer makes it a very interesting candidate molecule for targeted therapy. The anti-CD44 monoclonal antibody ARH460-16-2, that was generated and identified with Arius’ FunctionFirst™ platform, has significant tumor growth inhibitory activity in in vivo animal models of breast, prostate and liver cancer. A chimeric version of the antibody (chARH460-16-2) demonstrated potent dose-dependent tumor growth inhibitory efficacy in an in vivo established subcutaneous model of breast cancer and in an established orthotopic model of metastatic liver cancer at all doses (20, 2 and 0.2mg/kg). In the MDA-MB-231 breast cancer model it was associated with tumor regression and with increased survival (time-to-endpoint) at all doses. IHC staining of colon tumor tissue sections revealed specific binding of ARH460-16-2 to tumor cells in 47% of paTient samples (28/59), therefore extending the potential therapeutic benefit to human colon cancer. Previous work, carried out to elucidate mechanisms of action by which the ARH460-16-2 antibody mediates its tumor growth inhibitory activity, demonstrated its ability to induce tumor cell apoptosis in vitro and blocking of tumor cell binding to HA-coated surfaces. Early results from an in vitro kinase profiler screening study, carried out to address the direct impact of the antibody on intracellular signaling pathways, revealed suppression of phosphorylation of Tie-1 Receptor tyrosine kinase upon stimulation of MDA-MB-231 cells with serum, after pre-incubation with chARH460-16-2. This result could lead to the identification of potential biomarkers for activity and efficacy of anti-CD44 targeted therapy to be used in clinical trials. Two humanized versions of the ARH460-16-2 antibody were generated and their affinity was comparable to those of the chimeric version and parent murine monoclonal antibody, as determined by Biacore (KD ranged from 3-6 nM). The tumor growth inhibitory potency of the two humanized variants of huARH460-16-2 is currently being assessed in established tumor models. Analysis of the binding of ARH460-16-2, by FACS and by IHC, to tissues from various species, including non-human primates, led to the selection of cynomolgus monkeys as a model for the in vivo toxicology studies with this antibody.
Helen Findlay - One of the best experts on this subject based on the ideXlab platform.
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Chimeric and humanized versions of the anti-CD44 monoclonal antibody ARH460-16-2 have potent anti-tumor efficacy in established models of human breast and metastatic liver cancer
Molecular Cancer Therapeutics, 2007Co-Authors: Luis A. G. Da Cruz, Ningping Feng, Terence Lee, Daad Sayegh, Baldwin Mak, Ming Wang, Mitra Amoozgar, Susan Hahn, Daniel Pereira, Helen FindlayAbstract:A74 CD44 is a widely distributed protein implicated in multiple normal physiological and pathological events including co-stimulation of T-lymphocytes, leukocyte re-circulation and tumor metastasis. CD44 interacts with hyaluronic acid and other extracellular matrix components and metalloproteases, and recently has been shown to be expressed in tumor cancer stem cells from several cancer types, including breast, colon, prostate, pancreas and AML. The association of CD44 with cancer makes it a very interesting candidate molecule for targeted therapy. The anti-CD44 monoclonal antibody ARH460-16-2, that was generated and identified with Arius’ FunctionFirst™ platform, has significant tumor growth inhibitory activity in in vivo animal models of breast, prostate and liver cancer. A chimeric version of the antibody (chARH460-16-2) demonstrated potent dose-dependent tumor growth inhibitory efficacy in an in vivo established subcutaneous model of breast cancer and in an established orthotopic model of metastatic liver cancer at all doses (20, 2 and 0.2mg/kg). In the MDA-MB-231 breast cancer model it was associated with tumor regression and with increased survival (time-to-endpoint) at all doses. IHC staining of colon tumor tissue sections revealed specific binding of ARH460-16-2 to tumor cells in 47% of paTient samples (28/59), therefore extending the potential therapeutic benefit to human colon cancer. Previous work, carried out to elucidate mechanisms of action by which the ARH460-16-2 antibody mediates its tumor growth inhibitory activity, demonstrated its ability to induce tumor cell apoptosis in vitro and blocking of tumor cell binding to HA-coated surfaces. Early results from an in vitro kinase profiler screening study, carried out to address the direct impact of the antibody on intracellular signaling pathways, revealed suppression of phosphorylation of Tie-1 Receptor tyrosine kinase upon stimulation of MDA-MB-231 cells with serum, after pre-incubation with chARH460-16-2. This result could lead to the identification of potential biomarkers for activity and efficacy of anti-CD44 targeted therapy to be used in clinical trials. Two humanized versions of the ARH460-16-2 antibody were generated and their affinity was comparable to those of the chimeric version and parent murine monoclonal antibody, as determined by Biacore (KD ranged from 3-6 nM). The tumor growth inhibitory potency of the two humanized variants of huARH460-16-2 is currently being assessed in established tumor models. Analysis of the binding of ARH460-16-2, by FACS and by IHC, to tissues from various species, including non-human primates, led to the selection of cynomolgus monkeys as a model for the in vivo toxicology studies with this antibody.