Preventing Stem Cell Incorporation into Choroidal Neovascularization by Targeting Homing and Attachment Factors

Sphingosine-1-phospate (S1P) is a bioactive lysophospholipid signaling molecule that serves important roles in normal development and physiological processes, including modulating the immune, cardiovascular, and central nervous systems ( 1-4 ). S1P is a key player in the sphingolipid signaling cascade and is produced from ceramide (CER) and sphingosine (SPH) through the action of sphingosine kinase (SPHK). While CER and SPH are intracellular promoters of apoptosis, S1P has opposite action and, in general, protects cells from apoptotic stimuli. Several experimental fi ndings from independent research groups implicate S1P as a key mediator of multiple survival and growth-promoting pathways ( 5 ). The extracellular functions of S1P are initiated by the binding of the bioactive lipid to a set of fi ve G protein-coupled receptors (GPCRs) belonging to the S1P receptor family ( 6 ). The balance between CER/SPH levels versus S1P provides a rheostat that determines whether a cell is sent into the death Abstract Sphingosine-1-phosphate (S1P) is a pleiotropic bioactive lipid involved in multiple physiological processes. Importantly, dysregulated S1P levels are associated with several pathologies, including cardiovascular and infl ammatory diseases and cancer. This report describes the successful production and characterization of a murine monoclonal antibody, LT1002, directed against S1P, using novel immunization and screening methods applied to bioactive lipids. We also report the successful generation of LT1009, the humanized variant of LT1002, for potential clinical use. Both LT1002 and LT1009 have high affi nity and specifi city for S1P and do not cross-react with structurally related lipids. Using an in vitro bioassay, LT1002 and LT1009 were effective in blocking S1P-mediated release of the pro-angiogenic and prometastatic cytokine, interleukin-8, from human ovarian carcinoma cells, showing that both antibodies can outcompete S1P receptors in binding to S1P. In vivo anti-angiogenic activity of all antibody variants was demonstrated using the murine choroidal neovascularization model. Importantly, intravenous administration of the antibodies showed a marked effect on lymphocyte traffi cking. The resulting lead candidate, LT1009, has been formulated for Phase 1 clinical trials in cancer and age-related macular degeneration. The anti-S1P antibody shows promise as a novel, fi rst-in-class therapeutic acting as a "molecular sponge" to selectively deplete S1P from blood and other compartments where pathological S1P levels have been implicated in disease progression or in disorders where immune modulation may be benefi cial.

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“…CNV lesions were induced and quantifi ed as previously described ( 24,25 ), including the intravitreal injection of anti-S1P mAbs ( 18 ).…”

Section: Murine Cnv Modelmentioning

confidence: 99%

Production and characterization of monoclonal anti-sphingosine-1-phosphate antibodies

O’Brien

Jones

Williams

et al. 2009

Journal of Lipid Research

100

105

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“…The hypoxia-regulated factors VEGF and stromal-derived factor 1 (SDF1) induce hematopoietic stem cells (HSCs) to leave the BM and enter the circulation; they also induce the HSC progeny, endothelial precursor cells (EPCs), to leave the circulation at sites of ischemic injury to participate in vascular repair (16)(17)(18)(19)(22)(23)(24). Consequently, we asked whether IGFBP3, which is hypoxia-regulated, could act on HSC/EPC to stimulate migration and vessel formation and influence the participation of these cells in revascularization.…”

mentioning

confidence: 99%

IGF binding protein-3 regulates hematopoietic stem cell and endothelial precursor cell function during vascular development

Chang

Chan‐Ling

McFarland

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

128

106

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We asked whether the hypoxia-regulated factor, insulin-like growth factor binding protein-3 (IGFBP3), could modulate stem cell factor receptor (c-kit ؉ ), stem cell antigen-1 (sca-1 ؉ ), hematopoietic stem cell (HSC), or CD34 ؉ endothelial precursor cell (EPC) function. Exposure of CD34 ؉ EPCs to IGFBP3 resulted in rapid differentiation into endothelial cells and dose-dependent increases in cell migration and capillary tube formation. IGFBP3-expressing plasmid was injected into the vitreous of neonatal mice undergoing the oxygeninduced retinopathy (OIR) model. In separate studies, GFP-expressing HSCs were transfected with IGFBP3 plasmid and injected into the vitreous of OIR mice. Administering either IGFBP3 plasmid alone or HSCs transfected with the plasmid resulted in a similar reduction in areas of vasoobliteration, protection of the developing vasculature from hyperoxia-induced regression, and reduction in preretinal neovascularization compared to control plasmid or HSCs transfected with control plasmid. In conclusion, IGFBP3 mediates EPC migration, differentiation, and capillary formation in vitro. Targeted expression of IGFBP3 protects the vasculature from damage and promotes proper vascular repair after hyperoxic insult in the OIR model. IGFBP3 expression may represent a physiological adaptation to ischemia and potentially a therapeutic target for treatment of ischemic conditions. IGFBP3 ͉ angiogenesis ͉ retinopathy of prematurity V ascular damage associated with diabetic retinopathy and retinopathy of prematurity (ROP) results from tissue ischemia, and, subsequently, this ischemia leads to development of pathological neovascularization. Insulin-like growth factor 1 (IGF1) is required for normal retinal vascular development because vascular development is arrested in its absence despite the presence of VEGF (1). Development of ROP is associated with low levels of IGF1 (2) because the lack of IGF1 in the early neonatal period leads to the development of avascular retina, which results in ROP (3). However, unregulated IGF1 expression can lead to pathological neovascularization (4-13), and IGF1 receptor (IGF1R) antagonists are able to suppress retinal neovascularization in vivo by inhibiting VEGF signaling (1).The effects of IGF1 are mediated by IGF1R and modulated by complex interactions with IGF binding proteins (IGFBPs), which are also modulated at multiple levels. Six IGFBPs function as transporter proteins and storage pools for IGF1 in a tissue-and developmental stage-specific manner. Phosphorylation, proteolysis, polymerization (8), and cell or matrix association (9) regulates the functions of IGFBPs. Specific IGFBPs have been shown to either stimulate or inhibit IGF1 action (10).IGFBP3, the best studied and most abundant of these binding proteins, carries Ն75% of serum IGF1 and IGF2 in heterotrimeric complexes. Besides its endocrine effects, IGFBP3 has auto-and paracrine actions affecting cell mobility, adhesion, apoptosis, survival, and the cell cycle (14,15). Like the other IGFBPs, IGFBP3 has IGF1-in...

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“…Homing and adhesion of BM-derived cells to CNV could be targeted to prevent CNV. Blocking homing signals (through the antibody to stromal-derived factor-1 (SDF-1)) and endothelialspecific attachment factor (through the antibody to CD 144) has provided a proof of concept [73]. An alternative novel option for therapeutic intervention is a 'Trojan horse approach' that uses engineered BM-derived cells as a delivery vehicle for anti-angiogenic agents.…”

Section: Box 1: Outstanding Questionsmentioning

confidence: 99%

Anti-angiogenic therapy of exudative age-related macular degeneration: current progress and emerging concepts

Noël

Jost

Lambert³

et al. 2007

Trends in Molecular Medicine

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Age-related macular degeneration (AMD) is the leading cause of blindness in elderly patients. The more aggressive exudative form is characterized by abnormal bloodvessel development that occurs beneath the retina as a result of choroidal neovascularization (CNV). Vascular endothelial growth factor (VEGF) has emerged as the key mediator of CNV formation; this has led to intensive research on VEGF and the recent approval of anti-VEGF compounds by the US Food and Drug Administration. Despite this successful introduction of anti-angiogenic therapies into the clinical setting, there is still a lack of treatments that definitively reverse damaged vision. Here, we consider the importance of putative molecular targets other than VEGF that might have been underestimated. Emerging cellular mechanisms offer additional opportunities for innovative therapeutic approaches. GlossaryBruch's membrane: specialized basement membrane that separates the choroid from retinal pigmented epithelial cells. Choroid: a thin vascular layer between the sclera and the retina that supplies oxygen and nutrients to the retinal pigment epithelium and the photoreceptors. Endothelial cells: cells that line the inner lumen of blood vessels. Extracellular matrix: a three-dimensional network of macromolecules that form a structural scaffold and a signaling environment for cells. Matrix metalloproteinases (MMPs): a large family of proteolytic enzymes that degrade extracellular-matrix components and control the activity of important mediators of cell functions. Retinal pigment epithelium (RPE): a monolayer of cells that are specialized to serve the adjacent photoreceptors. Vascular endothelial growth factors (VEGFs): a family of powerful angiogenic proteins that control growth survival and the migration of endothelial cells. Age-related macular degenerationAge-related macular degeneration (AMD) is a leading cause of vision loss in the western world among people aged 50 or older [1]. Ninety per-cent of all vision loss due to AMD results from the exudative form, which is characterized by choroidal neovascularization (CNV), defined as newly formed blood vessels arising from choriocapillaries. The choroid is the vascular layer lying between the retina and the sclera. Exudation of fluid and hemorrhage into the sub-retinal space from hyperpermeable capillaries lead to retinal local detachment and retinal photoreceptor damage, which, in turn, lead to the formation of a disciform scar. The earliest clinically detectable abnormality in AMD, however, is not the consequence of pathological angiogenesis but is the accumulation of abnormal lipopro-teinaceous deposits ('drusen') in the extracellular matrix between the retinal pigment epithelium (RPE) and Bruch's membrane [2].Etiological research suggests that AMD is a complex disease caused by interactions of multiple gene products and environmental factors. Familial aggregation studies, twin studies and segregation analyses have provided strong evidence for AMD heritability [2]. Among several disease-causi...

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Preventing Stem Cell Incorporation into Choroidal Neovascularization by Targeting Homing and Attachment Factors

Abstract: These results indicate that homing and adhesion of progenitor cells to CNV may be targeted differentially or in combination to prevent CNV.

Cited by 62 publications

References 34 publications

Production and characterization of monoclonal anti-sphingosine-1-phosphate antibodies

Production and characterization of monoclonal anti-sphingosine-1-phosphate antibodies

IGF binding protein-3 regulates hematopoietic stem cell and endothelial precursor cell function during vascular development

Anti-angiogenic therapy of exudative age-related macular degeneration: current progress and emerging concepts

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