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Abstract
Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are uniquely required to balance the formation of new blood vessels with the maintenance and remodelling of existing ones, during development and in adult tissues. Recent advances have greatly expanded our understanding of the tight and multi-level regulation of VEGFR2 signalling, which is the primary focus of this Review. Important insights have been gained into the regulatory roles of VEGFR-interacting proteins (such as neuropilins, proteoglycans, integrins and protein tyrosine phosphatases); the dynamics of VEGFR2 endocytosis, trafficking and signalling; and the crosstalk between VEGF-induced signalling and other endothelial signalling cascades. A clear understanding of this multifaceted signalling web is key to successful therapeutic suppression or stimulation of vascular growth.
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Endothelial Cell Response to Fusobacterium nucleatum. Infect Immun 2016; 84:2141-2148. [PMID: 27185790 DOI: 10.1128/iai.01305-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/06/2016] [Indexed: 12/19/2022] Open
Abstract
Vascular response is an essential aspect of an effective immune response to periodontal disease pathogens, as new blood vessel formation contributes to wound healing and inflammation. Gaining a greater understanding of the factors that affect vascular response may then contribute to future breakthroughs in dental medicine. In this study, we have characterized the endothelial cell response to the common bacterium Fusobacterium nucleatum, an important bridging species that facilitates the activity of late colonizers of the dental biofilm. Endothelial cells were infected with Fusobacterium nucleatum (strain 25586) for periods of 4, 12, 24, or 48 h. Cell proliferation and tube formation were analyzed, and expression of adhesion molecules (CD31 and CD34) and vascular endothelial growth factor (VEGF) receptors 1 and 2 was measured by fluorescence-activated cell sorter (FACS) analysis. Data indicate that F. nucleatum impaired endothelial cell proliferation and tube formation. The findings suggest that the modified endothelial cell response acts as a mechanism promoting the pathogenic progression of periodontal diseases and may potentially suggest the involvement of periodontopathogens in systemic diseases associated with periodontal inflammation.
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Noel S, Fortier C, Murschel F, Belzil A, Gaudet G, Jolicoeur M, De Crescenzo G. Co-immobilization of adhesive peptides and VEGF within a dextran-based coating for vascular applications. Acta Biomater 2016; 37:69-82. [PMID: 27039978 DOI: 10.1016/j.actbio.2016.03.043] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 02/11/2016] [Accepted: 03/30/2016] [Indexed: 11/25/2022]
Abstract
UNLABELLED Multifunctional constructs providing a proper environment for adhesion and growth of selected cell types are needed for most tissue engineering and regenerative medicine applications. In this context, vinylsulfone (VS)-modified dextran was proposed as a matrix featuring low-fouling properties as well as multiple versatile moieties. The displayed VS groups could indeed react with thiol, amine or hydroxyl groups, be it for surface grafting, crosslinking or subsequent tethering of biomolecules. In the present study, a library of dextran-VS was produced, grafted to aminated substrates and characterized in terms of degree of VS modification (%VS), cell-repelling properties and potential for the oriented grafting of cysteine-tagged peptides. As a bioactive coating of vascular implants, ECM peptides (e.g. RGD) as well as vascular endothelial growth factor (VEGF) were co-immobilized on one of the most suitable dextran-VS coating (%VS=ca. 50% of saccharides units). Both RGD and VEGF were efficiently tethered at high densities (ca. 1nmol/cm(2) and 50fmol/cm(2), respectively), and were able to promote endothelial cell adhesion as well as proliferation. The latter was enhanced to the same extent as with soluble VEGF and proved selective to endothelial cells over smooth muscle cells. Altogether, multiple biomolecules could be efficiently incorporated into a dextran-VS construct, while maintaining their respective biological activity. STATEMENT OF SIGNIFICANCE This work addresses the need for multifunctional coatings and selective cell response inherent to many tissue engineering and regenerative medicine applications, for instance, vascular graft. More specifically, a library of dextrans was first generated through vinylsulfone (VS) modification. Thoroughly selected dextran-VS provided an ideal platform for unbiased study of cell response to covalently grafted biomolecules. Considering that processes such as healing and angiogenesis require multiple factors acting synergistically, vascular endothelial growth factor (VEGF) was then co-immobilized with the cell adhesive RGD peptide within our dextran coating through a relevant strategy featuring orientation and specificity. Altogether, both adhesive and proliferative cues could be incorporated into our construct with additive, if not synergetic, effects.
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Arutyunyan IV, Kananykhina EY, Fatkhudinov TK, El'chaninov AV, Makarov AV, Raimova ES, Bol'shakova GB, Sukhikh GT. Angiogenic Potential of Multipotent Stromal Cells from the Umbilical Cord: an In Vitro Study. Bull Exp Biol Med 2016; 161:141-9. [PMID: 27265141 DOI: 10.1007/s10517-016-3365-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Indexed: 02/07/2023]
Abstract
The mechanisms of proangiogenic activity of multipotent stromal cells from human umbilical cord were analyzed in vitro. The absence of secreted forms of proangiogenic growth factor VEGF-A in the culture medium conditioned by umbilical cord-derived multipotent stromal cells was shown by ELISA. However, the possibility of paracrine stimulation of cell proliferation, mobility, and directed migration of endothelial EA.hy926 cells was demonstrated by using MTT test, Transwell system, and monolayer wound modeling. The capacity of multipotent stromal cells to acquire the phenotype of endothelium-like cells was analyzed using differentiation media of three types. It was found that VEGF-A is an essential but not sufficient inductor of differentiation of umbilical cord-derived multipotent stromal cells into CD31+ cells.
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Affiliation(s)
- I V Arutyunyan
- V. I. Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia
- Research Institute of Human Morphology, Moscow, Russia
| | - E Yu Kananykhina
- V. I. Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia
- Research Institute of Human Morphology, Moscow, Russia
| | - T Kh Fatkhudinov
- V. I. Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia.
- Research Institute of Human Morphology, Moscow, Russia.
- N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia.
| | - A V El'chaninov
- V. I. Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia
- Research Institute of Human Morphology, Moscow, Russia
- N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
| | - A V Makarov
- V. I. Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia
- Research Institute of Human Morphology, Moscow, Russia
- N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
| | - E Sh Raimova
- N. I. Pirogov Russian National Research Medical University, Ministry of Health of the Russian Federation, Moscow, Russia
| | | | - G T Sukhikh
- V. I. Kulakov Research Center of Obstetrics, Gynecology, and Perinatology, Ministry of Health of the Russian Federation, Moscow, Russia
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Sarabipour S, Ballmer-Hofer K, Hristova K. VEGFR-2 conformational switch in response to ligand binding. eLife 2016; 5:e13876. [PMID: 27052508 PMCID: PMC4829425 DOI: 10.7554/elife.13876] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/09/2016] [Indexed: 01/02/2023] Open
Abstract
VEGFR-2 is the primary regulator of angiogenesis, the development of new blood vessels from pre-existing ones. VEGFR-2 has been hypothesized to be monomeric in the absence of bound ligand, and to undergo dimerization and activation only upon ligand binding. Using quantitative FRET and biochemical analysis, we show that VEGFR-2 forms dimers also in the absence of ligand when expressed at physiological levels, and that these dimers are phosphorylated. Ligand binding leads to a change in the TM domain conformation, resulting in increased kinase domain phosphorylation. Inter-receptor contacts within the extracellular and TM domains are critical for the establishment of the unliganded dimer structure, and for the transition to the ligand-bound active conformation. We further show that the pathogenic C482R VEGFR-2 mutant, linked to infantile hemangioma, promotes ligand-independent signaling by mimicking the structure of the ligand-bound wild-type VEGFR-2 dimer.
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Affiliation(s)
- Sarvenaz Sarabipour
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, United States
| | - Kurt Ballmer-Hofer
- Laboratory of Biomolecular Research, Molecular Cell Biology, Paul Scherrer Institute, Villigen, Switzerland
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, United States
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Arutyunyan I, Fatkhudinov T, Kananykhina E, Usman N, Elchaninov A, Makarov A, Bolshakova G, Goldshtein D, Sukhikh G. Role of VEGF-A in angiogenesis promoted by umbilical cord-derived mesenchymal stromal/stem cells: in vitro study. Stem Cell Res Ther 2016; 7:46. [PMID: 27001300 PMCID: PMC4802928 DOI: 10.1186/s13287-016-0305-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 02/25/2016] [Accepted: 03/03/2016] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Mesenchymal stromal/stem cells derived from human umbilical cord (UC-MSCs) uniquely combine properties of embryonic and postnatal MSCs and may be the most acceptable, safe, and effective source for allogeneic cell therapy e.g. for therapeutic angiogenesis. In this report we describe pro-angiogenic properties of UC-MSCs as manifested in vitro. METHODS UC-MSCs were isolated from human Wharton's jelly by enzymatic digestion. Presence of soluble forms of VEGF-A in UC-MSC-conditioned media was measured by ELISA. Effects of the conditioned media on human umbilical vein-derived endothelial EA.hy926 cells proliferation were measured by MTT-assay; changes in cell motility and directed migration were assessed by scratch wound healing and transwell chamber migration assays. Angiogenesis was modeled in vitro as tube formation on basement membrane matrix. Progressive differentiation of MSCs to endothelioid progeny was assessed by CD31 immunostaining. RESULTS Although no detectable quantities of soluble VEGF-A were produced by UC-MSCs, the culture medium, conditioned by the UC-MSCs, effectively stimulated proliferation, motility, and directed migration of EA.hy926 cells. In 2D culture, UC-MSCs were able to acquire CD31(+) endothelial cell-like phenotype when stimulated by EA.hy926-conditioned media supplemented with VEGF-A165. UC-MSCs were capable of forming unstable 2D tubular networks either by themselves or in combinations with EA.hy926 cells. Active spontaneous sprouting from cell clusters, resulting from disassembling of such networks, was observed only in the mixed cultures, not in pure UC-MSC cultures. In 3D mode of sprouting experimentation, structural support of newly formed capillary-like structures was provided by UC-MSCs that acquired the CD31(+) phenotype in the absence of exogenous VEGF-A. CONCLUSION These data suggest that a VEGF-A-independent paracrine mechanism and at least partially VEGF-A-independent differentiation mechanism are involved in the pro-angiogenic activity of UC-MSCs.
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Affiliation(s)
- Irina Arutyunyan
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
- Scientific Research Institute of Human Morphology, 3 Tsurupa Street, Moscow, 117418 Russia
| | - Timur Fatkhudinov
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
- Pirogov Russian National Research Medical University, Ministry of Healthcare of the Russian Federation, 1 Ostrovitianov Street, Moscow, 117997 Russia
- Laboratory of Regenerative Medicine, Research Center for Obstetrics, Gynecology and Perinatology, 4 Oparin Street, Moscow, 117997 Russia
| | - Evgeniya Kananykhina
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
- Scientific Research Institute of Human Morphology, 3 Tsurupa Street, Moscow, 117418 Russia
| | - Natalia Usman
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
- Pirogov Russian National Research Medical University, Ministry of Healthcare of the Russian Federation, 1 Ostrovitianov Street, Moscow, 117997 Russia
| | - Andrey Elchaninov
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
- Scientific Research Institute of Human Morphology, 3 Tsurupa Street, Moscow, 117418 Russia
| | - Andrey Makarov
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
- Pirogov Russian National Research Medical University, Ministry of Healthcare of the Russian Federation, 1 Ostrovitianov Street, Moscow, 117997 Russia
| | - Galina Bolshakova
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
| | - Dmitry Goldshtein
- Research Center of Medical Genetics, 1 Moskvorechie Street, Moscow, 115478 Russia
| | - Gennady Sukhikh
- Research Center for Obstetrics, Gynecology and Perinatology of Ministry of Healthcare of the Russian Federation, 4 Oparina Street, Moscow, 117997 Russia
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Hayashi H, Al Mamun A, Sakima M, Sato M. Activator of G-protein signaling 8 is involved in VEGF-mediated signal processing during angiogenesis. J Cell Sci 2016; 129:1210-22. [PMID: 26826188 DOI: 10.1242/jcs.181883] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/26/2016] [Indexed: 01/13/2023] Open
Abstract
Activator of G-protein signaling 8 (AGS8, also known as FNDC1) is a receptor-independent accessory protein for the Gβγ subunit, which was isolated from rat heart subjected to repetitive transient ischemia with the substantial development of collaterals. Here, we report the role of AGS8 in vessel formation by endothelial cells. Knockdown of AGS8 by small interfering RNA (siRNA) inhibited vascular endothelial growth factor (VEGF)-induced tube formation, as well as VEGF-stimulated cell growth and migration. VEGF stimulated the phosphorylation of the VEGF receptor-2 (VEGFR-2, also known as KDR), ERK1/2 and p38 MAPK; however, knockdown of AGS8 inhibited these signaling events. Signal alterations by AGS8 siRNA were associated with a decrease of cell surface VEGFR-2 and an increase of VEGFR-2 in the cytosol. Endocytosis blockers did not influence the decrease of VEGFR-2 by AGS8 siRNA, suggesting the involvement of AGS8 in VEGFR-2 trafficking to the plasma membrane. VEGFR-2 formed a complex with AGS8 in cells, and a peptide designed to disrupt AGS8-Gβγ interaction inhibited VEGF-induced tube formation. These data suggest a potential role for AGS8-Gβγ in VEGF signal processing. AGS8 might play a key role in tissue adaptation by regulating angiogenic events.
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Affiliation(s)
- Hisaki Hayashi
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Abdullah Al Mamun
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Miho Sakima
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
| | - Motohiko Sato
- Department of Physiology, Aichi Medical University, Nagakute, Aichi 480-1195, Japan
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Lee-Montiel FT, Li P, Imoukhuede PI. Quantum dot multiplexing for the profiling of cellular receptors. NANOSCALE 2015; 7:18504-18514. [PMID: 26377627 DOI: 10.1039/c5nr01455g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The profiling of cellular heterogeneity has wide-reaching importance for our understanding of how cells function and react to their environments in healthy and diseased states. Our ability to interpret and model cell behavior has been limited by the difficulties of measuring cell differences, for example, comparing tumor and non-tumor cells, particularly at the individual cell level. This demonstrates a clear need for a generalizable approach to profile fluorophore sites on cells or molecular assemblies on beads. Here, a multiplex immunoassay for simultaneous detection of five different angiogenic markers was developed. We targeted angiogenic receptors in the vascular endothelial growth factor family (VEGFR1, VEGFR2 and VEGFR3) and Neuropilin (NRP) family (NRP1 and NRP2), using multicolor quantum dots (Qdots). Copper-free click based chemistry was used to conjugate the monoclonal antibodies with 525, 565, 605, 655 and 705 nm CdSe/ZnS Qdots. We tested and performed colocalization analysis of our nanoprobes using the Pearson correlation coefficient statistical analysis. Human umbilical vein endothelial cells (HUVEC) were tested. The ability to easily monitor the molecular indicators of angiogenesis that are a precursor to cancer in a fast and cost effective system is an important step towards personalized nanomedicine.
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Affiliation(s)
- Felipe T Lee-Montiel
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
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Finley SD, Angelikopoulos P, Koumoutsakos P, Popel AS. Pharmacokinetics of Anti-VEGF Agent Aflibercept in Cancer Predicted by Data-Driven, Molecular-Detailed Model. CPT Pharmacometrics Syst Pharmacol 2015; 4:641-9. [PMID: 26783500 PMCID: PMC4716581 DOI: 10.1002/psp4.12040] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 07/31/2015] [Accepted: 09/10/2015] [Indexed: 12/18/2022] Open
Abstract
Mathematical models can support the drug development process by predicting the pharmacokinetic (PK) properties of the drug and optimal dosing regimens. We have developed a pharmacokinetic model that includes a biochemical molecular interaction network linked to a whole-body compartment model. We applied the model to study the PK of the anti-vascular endothelial growth factor (VEGF) cancer therapeutic agent, aflibercept. Clinical data is used to infer model parameters using a Bayesian approach, enabling a quantitative estimation of the contributions of specific transport processes and molecular interactions of the drug that cannot be examined in other PK modeling, and insight into the mechanisms of aflibercept's antiangiogenic action. Additionally, we predict the plasma and tissue concentrations of unbound and VEGF-bound aflibercept. Thus, we present a computational framework that can serve as a valuable tool for drug development efforts.
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Affiliation(s)
- SD Finley
- Department of Biomedical EngineeringUniversity of Southern CaliforniaLos AngelesCaliforniaUSA
| | - P Angelikopoulos
- Computational Science and Engineering Laboratory, Department of Mechanical and Process Engineering, ETH ZurichSwitzerland
| | - P Koumoutsakos
- Computational Science and Engineering Laboratory, Department of Mechanical and Process Engineering, ETH ZurichSwitzerland
| | - AS Popel
- Department of Biomedical EngineeringJohns Hopkins University School of MedicineBaltimoreMarylandUSA
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Ansari A, Lee-Montiel FT, Amos JR, Imoukhuede PI. Secondary anchor targeted cell release. Biotechnol Bioeng 2015; 112:2214-27. [PMID: 26010879 DOI: 10.1002/bit.25648] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 05/11/2015] [Indexed: 01/11/2023]
Abstract
Personalized medicine offers the promise of tailoring therapy to patients, based on their cellular biomarkers. To achieve this goal, cellular profiling systems are needed that can quickly and efficiently isolate specific cell types without disrupting cellular biomarkers. Here we describe the development of a unique platform that facilitates gentle cell capture via a secondary, surface-anchoring moiety, and cell release. The cellular capture system consists of a glass surface functionalized with APTES, d-desthiobiotin, and streptavidin. Biotinylated mCD11b and hIgG antibodies are used to capture mouse macrophages (RAW 264.7) and human breast cancer (MCF7-GFP) cell lines, respectively. The surface functionalization is optimized by altering assay components, such as streptavidin, d-desthiobiotin, and APTES, to achieve cell capture on 80% of the functionalized surface and cell release upon biotin treatment. We also demonstrate an ability to capture 50% of target cells within a dual-cell mixture. This engineering advancement is a critical step towards achieving cell isolation platforms for personalized medicine.
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Affiliation(s)
| | | | - Jennifer R Amos
- Department of Bioengineering, University of Illinois at Urbana Champaign, Urbana, Illinois, 61801
| | - P I Imoukhuede
- Department of Bioengineering, University of Illinois at Urbana Champaign, Urbana, Illinois, 61801.
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Chen S, Guo X, Imarenezor O, Imoukhuede PI. Quantification of VEGFRs, NRP1, and PDGFRs on Endothelial Cells and Fibroblasts Reveals Serum, Intra-Family Ligand, and Cross-Family Ligand Regulation. Cell Mol Bioeng 2015. [DOI: 10.1007/s12195-015-0411-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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Clegg LW, Mac Gabhann F. Site-Specific Phosphorylation of VEGFR2 Is Mediated by Receptor Trafficking: Insights from a Computational Model. PLoS Comput Biol 2015; 11:e1004158. [PMID: 26067165 PMCID: PMC4466579 DOI: 10.1371/journal.pcbi.1004158] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 01/25/2015] [Indexed: 02/05/2023] Open
Abstract
Matrix-binding isoforms and non-matrix-binding isoforms of vascular endothelial growth factor (VEGF) are both capable of stimulating vascular remodeling, but the resulting blood vessel networks are structurally and functionally different. Here, we develop and validate a computational model of the binding of soluble and immobilized ligands to VEGF receptor 2 (VEGFR2), the endosomal trafficking of VEGFR2, and site-specific VEGFR2 tyrosine phosphorylation to study differences in induced signaling between these VEGF isoforms. In capturing essential features of VEGFR2 signaling and trafficking, our model suggests that VEGFR2 trafficking parameters are largely consistent across multiple endothelial cell lines. Simulations demonstrate distinct localization of VEGFR2 phosphorylated on Y1175 and Y1214. This is the first model to clearly show that differences in site-specific VEGFR2 activation when stimulated with immobilized VEGF compared to soluble VEGF can be accounted for by altered trafficking of VEGFR2 without an intrinsic difference in receptor activation. The model predicts that Neuropilin-1 can induce differences in the surface-to-internal distribution of VEGFR2. Simulations also show that ligated VEGFR2 and phosphorylated VEGFR2 levels diverge over time following stimulation. Using this model, we identify multiple key levers that alter how VEGF binding to VEGFR2 results in different coordinated patterns of multiple downstream signaling pathways. Specifically, simulations predict that VEGF immobilization, interactions with Neuropilin-1, perturbations of VEGFR2 trafficking, and changes in expression or activity of phosphatases acting on VEGFR2 all affect the magnitude, duration, and relative strength of VEGFR2 phosphorylation on tyrosines 1175 and 1214, and they do so predictably within our single consistent model framework. Vascular endothelial growth factor (VEGF) is an important regulator of blood vessel growth. To date, therapies attempting to harness the VEGF system to promote blood vessel growth (e.g. for wound healing or ischemic disease) have achieved only limited success. To improve VEGF-based therapies, we need to better understand how VEGF promotes development of functional blood vessels. We have developed a computational model of VEGF binding to the receptor VEGFR2, trafficking of VEGFR2 through endosomal compartments in the cell, and activation of VEGFR2 on several tyrosine residues. The pattern of tyrosines activated on VEGFR2 influences cell behavior, promoting cell survival, proliferation, or migration. The combination of these cues influences the diameter of vessels, degree of branching, and leakiness of the resultant vessel network. Our model shows that changes in VEGFR2 trafficking as a result of VEGF immobilization to the extracellular matrix are sufficient to describe observed changes in the pattern of VEGFR2 activation compared to stimulation with purely soluble VEGF. This model can be used to predict how VEGF immobilization, interactions with co-receptors or proteins that deactivate VEGFR2, and changes to VEGFR2 trafficking can be tuned to promote development of functional blood vessel networks for tissue engineering applications.
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Affiliation(s)
- Lindsay Wendel Clegg
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
| | - Feilim Mac Gabhann
- Institute for Computational Medicine and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
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Norton KA, Popel AS, Pandey NB. Heterogeneity of chemokine cell-surface receptor expression in triple-negative breast cancer. Am J Cancer Res 2015; 5:1295-1307. [PMID: 26101698 PMCID: PMC4473311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 01/24/2015] [Indexed: 06/04/2023] Open
Abstract
INTRODUCTION Tumor heterogeneity is a well-established concept in cancer research. In this paper, we examine an additional type of tumor cell heterogeneity - tumor cell-surface receptor heterogeneity. METHODS We use flow cytometry to measure the frequency and numbers of cell-surface receptors on triple negative breast cancer cell lines. RESULTS We find two distinct populations of human triple-negative breast cancer cells MDA-MB-231 when they are grown in culture, one with low surface levels of various chemokine receptors and a second with much higher levels. The population with high surface levels of these receptors is increased in the more metastatic MDA-MB-231-luc-d3h2ln cell line. CONCLUSION We hypothesize that this high cell-surface receptor population is involved in metastasis. We find that the receptor high populations can be modulated by tumor conditioned media and IL6 treatment indicating that the tumor microenvironment is important for the maintenance and sizes of these populations.
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Affiliation(s)
- Kerri-Ann Norton
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins UniversityBaltimore, MD 21205, USA
| | - Aleksander S Popel
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins UniversityBaltimore, MD 21205, USA
- Department of Oncology and The Sidney Kimmel Comprehensive Cancer Center, School of Medicine, Johns Hopkins UniversityBaltimore, MD, USA
| | - Niranjan B Pandey
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins UniversityBaltimore, MD 21205, USA
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Eggers C, Müller J, Schultze-Mosgau S. VEGF transfer based on gene-modified fibroblasts using a hypoxia-induced vector to modulate neoangiogenesis in ischaemic regions of myocutaneous transplants. Int J Oral Maxillofac Surg 2014; 44:267-76. [PMID: 25441860 DOI: 10.1016/j.ijom.2014.06.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 06/29/2014] [Accepted: 06/30/2014] [Indexed: 11/28/2022]
Abstract
The effect of a hypoxia-inducible VEGF-expressing on wound healing in an ischaemic hind leg rat model was evaluated in this study. 180 Wistar rats were assigned randomly to three groups. After ligation of the femoral artery, group 1 received pRTP801-VEGF165, group 2 untransfected fibroblasts, group 3 saline; injection was into the subcutaneous tissue, proximal and distal to the artery ligation. Biopsy specimens were obtained on days 3, 5, 7, 14 after implementation. VEGF transgene expression, vessel architecture, the amount and total area of vessel formation were investigated. Results showed a significantly higher level of VEGF protein expression in group 1 compared to group 2 (P≤0.001) throughout the investigational period. Group 1 exhibited a significant growth of CD31-positive blood vessels in the subcutaneous tissue on day 14 compared to groups 2 and 3 (P≤0.001) (group 1, 62.20±1.92; group 2, 20.60±1.67; group 3, 12.40±1.14). Alpha-SMA-positive staining also showed significant vessel growth in group 1 on day 5 (group 1, 27.00±1.87; group 2, 7.20±1.48; group 3, 10.00±1.73). These results were confirmed in the distal muscle tissue. No significant results were obtained for the proximal muscle tissue. The subcutaneous application of pRTP801-VEGF165 showed a long-lasting effect, with an increased expression of VEGF over the entire observation period. It appears that the use of fibroblasts transfected with VEGF is a promising way to increase early angiogenesis in ischaemic tissue.
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Affiliation(s)
- C Eggers
- Department of Oral and Cranio-Maxillofacial Surgery/Plastic Surgery, Friedrich-Schiller University, Jena, Germany.
| | - J Müller
- Department of Oral and Cranio-Maxillofacial Surgery/Plastic Surgery, Friedrich-Schiller University, Jena, Germany
| | - S Schultze-Mosgau
- Department of Oral and Cranio-Maxillofacial Surgery/Plastic Surgery, Friedrich-Schiller University, Jena, Germany
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Favia A, Desideri M, Gambara G, D'Alessio A, Ruas M, Esposito B, Del Bufalo D, Parrington J, Ziparo E, Palombi F, Galione A, Filippini A. VEGF-induced neoangiogenesis is mediated by NAADP and two-pore channel-2-dependent Ca2+ signaling. Proc Natl Acad Sci U S A 2014; 111:E4706-15. [PMID: 25331892 PMCID: PMC4226099 DOI: 10.1073/pnas.1406029111] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Vascular endothelial growth factor (VEGF) and its receptors VEGFR1/VEGFR2 play major roles in controlling angiogenesis, including vascularization of solid tumors. Here we describe a specific Ca(2+) signaling pathway linked to the VEGFR2 receptor subtype, controlling the critical angiogenic responses of endothelial cells (ECs) to VEGF. Key steps of this pathway are the involvement of the potent Ca(2+) mobilizing messenger, nicotinic acid adenine-dinucleotide phosphate (NAADP), and the specific engagement of the two-pore channel TPC2 subtype on acidic intracellular Ca(2+) stores, resulting in Ca(2+) release and angiogenic responses. Targeting this intracellular pathway pharmacologically using the NAADP antagonist Ned-19 or genetically using Tpcn2(-/-) mice was found to inhibit angiogenic responses to VEGF in vitro and in vivo. In human umbilical vein endothelial cells (HUVECs) Ned-19 abolished VEGF-induced Ca(2+) release, impairing phosphorylation of ERK1/2, Akt, eNOS, JNK, cell proliferation, cell migration, and capillary-like tube formation. Interestingly, Tpcn2 shRNA treatment abolished VEGF-induced Ca(2+) release and capillary-like tube formation. Importantly, in vivo VEGF-induced vessel formation in matrigel plugs in mice was abolished by Ned-19 and, most notably, failed to occur in Tpcn2(-/-) mice, but was unaffected in Tpcn1(-/-) animals. These results demonstrate that a VEGFR2/NAADP/TPC2/Ca(2+) signaling pathway is critical for VEGF-induced angiogenesis in vitro and in vivo. Given that VEGF can elicit both pro- and antiangiogenic responses depending upon the balance of signal transduction pathways activated, targeting specific VEGFR2 downstream signaling pathways could modify this balance, potentially leading to more finely tailored therapeutic strategies.
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Affiliation(s)
- Annarita Favia
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy
| | - Marianna Desideri
- Experimental Chemotherapy Laboratory, Regina Elena National Cancer Institute, 00128 Rome, Italy
| | - Guido Gambara
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy
| | - Alessio D'Alessio
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy; Institute of Histology and Embryology, Catholic University of the Sacred Heart, 00168 Rome, Italy; and
| | - Margarida Ruas
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Bianca Esposito
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy
| | - Donatella Del Bufalo
- Experimental Chemotherapy Laboratory, Regina Elena National Cancer Institute, 00128 Rome, Italy
| | - John Parrington
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Elio Ziparo
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy
| | - Fioretta Palombi
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom
| | - Antonio Filippini
- Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Unit of Histology and Medical Embryology, Sapienza University of Rome, 00161 Rome, Italy;
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66
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Norton KA, Han Z, Popel AS, Pandey NB. Antiangiogenic cancer drug sunitinib exhibits unexpected proangiogenic effects on endothelial cells. Onco Targets Ther 2014; 7:1571-82. [PMID: 25228815 PMCID: PMC4164292 DOI: 10.2147/ott.s65055] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Angiogenesis, the formation of new blood vessels, is an essential step for cancer progression, but antiangiogenic therapies have shown limited success. Therefore, a better understanding of the effects of antiangiogenic treatments on endothelial cells is necessary. In this study, we evaluate the changes in cell surface vascular endothelial growth factor receptor (VEGFR) expression on endothelial cells in culture treated with the antiangiogenic tyrosine kinase inhibitor drug sunitinib, using quantitative flow cytometry. We find that proangiogenic VEGFR2 cell surface receptor numbers are increased with sunitinib treatment. This proangiogenic effect might account for the limited effects of sunitinib as a cancer therapy. We also find that this increase is inhibited by brefeldin A, an inhibitor of protein transport from the endoplasmic reticulum to the Golgi apparatus. The complex dynamics of cell surface VEGFRs may be important for successful treatment of cancer with antiangiogenic therapeutics.
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Affiliation(s)
- Kerri-Ann Norton
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Zheyi Han
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Aleksander S Popel
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, USA ; Department of Oncology and the Sidney Kimmel Comprehensive Cancer Center, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Niranjan B Pandey
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
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67
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Abstract
Endothelial cells (ECs) exhibit dramatic plasticity of form at the single- and collective-cell level during new vessel growth, adult vascular homeostasis, and pathology. Understanding how, when, and why individual ECs coordinate decisions to change shape, in relation to the myriad of dynamic environmental signals, is key to understanding normal and pathological blood vessel behavior. However, this is a complex spatial and temporal problem. In this review we show that the multidisciplinary field of Adaptive Systems offers a refreshing perspective, common biological language, and straightforward toolkit that cell biologists can use to untangle the complexity of dynamic, morphogenetic systems.
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Affiliation(s)
- Katie Bentley
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
| | - Andrew Philippides
- Centre for Computational Neuroscience and Robotics, Department of Informatics, University of Sussex, Brighton BN1 9QJ, UK
| | - Erzsébet Ravasz Regan
- Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
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68
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Laminin promotes vascular network formation in 3D in vitro collagen scaffolds by regulating VEGF uptake. Exp Cell Res 2014; 327:68-77. [PMID: 24907654 PMCID: PMC4155934 DOI: 10.1016/j.yexcr.2014.05.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 04/15/2014] [Accepted: 05/20/2014] [Indexed: 11/20/2022]
Abstract
Angiogenesis is an essential neovascularisation process, which if recapitulated in 3D in vitro, will provide better understanding of endothelial cell (EC) behaviour. Various cell types and growth factors are involved, with vascular endothelial growth factor (VEGF) and its receptors VEGFR1 and VEGFR2 key components. We were able to control the aggregation pattern of ECs in 3D collagen hydrogels, by varying the matrix composition and/or having a source of cells signalling angiogenic proteins. These aggregation patterns reflect the different developmental pathways that ECs take to form different sized tubular structures. Cultures with added laminin and thus increased expression of α6 integrin showed a significant increase (p<0.05) in VEGFR2 positive ECs and increased VEGF uptake. This resulted in the end-to-end network aggregation of ECs. In cultures without laminin and therefore low α6 integrin expression, VEGFR2 levels and VEGF uptake were significantly lower (p<0.05). These ECs formed contiguous sheets, analogous to the 'wrapping' pathway in development. We have identified a key linkage between integrin expression on ECs and their uptake of VEGF, regulated by VEGFR2, resulting in different aggregation patterns in 3D.
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69
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Weddell JC, Imoukhuede PI. Quantitative characterization of cellular membrane-receptor heterogeneity through statistical and computational modeling. PLoS One 2014; 9:e97271. [PMID: 24827582 PMCID: PMC4020774 DOI: 10.1371/journal.pone.0097271] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 04/16/2014] [Indexed: 12/20/2022] Open
Abstract
Cell population heterogeneity can affect cellular response and is a major factor in drug resistance. However, there are few techniques available to represent and explore how heterogeneity is linked to population response. Recent high-throughput genomic, proteomic, and cellomic approaches offer opportunities for profiling heterogeneity on several scales. We have recently examined heterogeneity in vascular endothelial growth factor receptor (VEGFR) membrane localization in endothelial cells. We and others processed the heterogeneous data through ensemble averaging and integrated the data into computational models of anti-angiogenic drug effects in breast cancer. Here we show that additional modeling insight can be gained when cellular heterogeneity is considered. We present comprehensive statistical and computational methods for analyzing cellomic data sets and integrating them into deterministic models. We present a novel method for optimizing the fit of statistical distributions to heterogeneous data sets to preserve important data and exclude outliers. We compare methods of representing heterogeneous data and show methodology can affect model predictions up to 3.9-fold. We find that VEGF levels, a target for tuning angiogenesis, are more sensitive to VEGFR1 cell surface levels than VEGFR2; updating VEGFR1 levels in the tumor model gave a 64% change in free VEGF levels in the blood compartment, whereas updating VEGFR2 levels gave a 17% change. Furthermore, we find that subpopulations of tumor cells and tumor endothelial cells (tEC) expressing high levels of VEGFR (>35,000 VEGFR/cell) negate anti-VEGF treatments. We show that lowering the VEGFR membrane insertion rate for these subpopulations recovers the anti-angiogenic effect of anti-VEGF treatment, revealing new treatment targets for specific tumor cell subpopulations. This novel method of characterizing heterogeneous distributions shows for the first time how different representations of the same data set lead to different predictions of drug efficacy.
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Affiliation(s)
- Jared C. Weddell
- Department of Bioengineering, University of Illinois Urbana Champaign, Urbana, Illinois, United States of America
| | - P. I. Imoukhuede
- Department of Bioengineering, University of Illinois Urbana Champaign, Urbana, Illinois, United States of America
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70
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Roxworthy BJ, Johnston MT, Lee-Montiel FT, Ewoldt RH, Imoukhuede PI, Toussaint KC. Plasmonic optical trapping in biologically relevant media. PLoS One 2014; 9:e93929. [PMID: 24710326 PMCID: PMC3977964 DOI: 10.1371/journal.pone.0093929] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/11/2014] [Indexed: 12/14/2022] Open
Abstract
We present plasmonic optical trapping of micron-sized particles in biologically relevant buffer media with varying ionic strength. The media consist of 3 cell-growth solutions and 2 buffers and are specifically chosen due to their widespread use and applicability to breast-cancer and angiogenesis studies. High-precision rheological measurements on the buffer media reveal that, in all cases excluding the 8.0 pH Stain medium, the fluids exhibit Newtonian behavior, thereby enabling straightforward measurements of optical trap stiffness from power-spectral particle displacement data. Using stiffness as a trapping performance metric, we find that for all media under consideration the plasmonic nanotweezers generate optical forces 3–4x a conventional optical trap. Further, plasmonic trap stiffness values are comparable to those of an identical water-only system, indicating that the performance of a plasmonic nanotweezer is not degraded by the biological media. These results pave the way for future biological applications utilizing plasmonic optical traps.
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Affiliation(s)
- Brian J. Roxworthy
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Michael T. Johnston
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Felipe T. Lee-Montiel
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Randy H. Ewoldt
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Princess I. Imoukhuede
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Kimani C. Toussaint
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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71
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Imoukhuede PI, Popel AS. Quantitative fluorescent profiling of VEGFRs reveals tumor cell and endothelial cell heterogeneity in breast cancer xenografts. Cancer Med 2014; 3:225-44. [PMID: 24449499 PMCID: PMC3987073 DOI: 10.1002/cam4.188] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 10/30/2013] [Accepted: 11/13/2013] [Indexed: 12/25/2022] Open
Abstract
Plasma membrane-localized vascular endothelial growth factor receptors (VEGFR) play a critical role in transducing VEGF signaling toward pro and antiangiogenic outcomes and quantitative characterization of these receptors is critical toward identifying biomarkers for antiangiogenic therapies, understanding mechanisms of action of antiangiogenic drugs, and advancing predictive computational models. While in vitro analysis of cell surface-VEGFRs has been performed, little is known about the levels of cell surface-VEGFR on tumor cells. Therefore, we inoculate nude mice with the human triple-negative breast cancer, MDA-MB-231, cell line; isolate human tumor cells and mouse tumor endothelial cells from xenografts; and quantitatively characterize the VEGFR localization on these cells. We observe 15,000 surface-VEGFR1/tumor endothelial cell versus 8200 surface-VEGFR1/tumor endothelial cell at 3 and 6 weeks of tumor growth, respectively; and we quantify 1200-1700 surface-VEGFR2/tumor endothelial cell. The tumor cell levels of VEGFR1 and VEGFR2 are relatively constant between 3 and 6 weeks: 2000-2200 surface-VEGFR1/tumor cell and ~1000 surface-VEGFR2/tumor cell. Cell-by-cell analysis provides additional insight into tumor heterogeneity by identifying four cellular subpopulations based on size and levels of cell membrane-localized VEGFR. Furthermore, when these ex vivo data are compared to in vitro data, we observe little to no VEGFRs on MDA-MB-231 cells, and the MDA-MB-231 VEGFR surface levels are not regulated by a saturating dose of VEGF. Overall, the quantification of these dissimilarities for the first time in tumor provides insight into the balance of modulatory (VEGFR1) and proangiogenic (VEGFR2) receptors.
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Affiliation(s)
- Princess I Imoukhuede
- Department of Bioengineering, University of Illinois at Urbana ChampaignUrbana, Illinois, 61801
| | - Aleksander S Popel
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins UniversityBaltimore, Maryland, 21205
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72
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Jeynes JCG, Jeynes C, Merchant MJ, Kirkby KJ. Measuring and modelling cell-to-cell variation in uptake of gold nanoparticles. Analyst 2013; 138:7070-4. [PMID: 24102065 DOI: 10.1039/c3an01406a] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The cell-to-cell variation of gold nanoparticle (GNP) uptake is important for therapeutic applications. We directly counted the GNPs in hundreds of individual cells, and showed that the large variation from cell-to-cell could be directly modelled by assuming log-normal distributions of both cell mass and GNP rate of uptake. This was true for GNPs non-specifically bound to fetal bovine serum or conjugated to a cell penetrating peptide. Within a population of cells, GNP content varied naturally by a factor greater than 10 between individual cells.
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73
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Tan WH, Popel AS, Mac Gabhann F. Computational model of VEGFR2 pathway to ERK activation and modulation through receptor trafficking. Cell Signal 2013; 25:2496-510. [PMID: 23993967 DOI: 10.1016/j.cellsig.2013.08.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 08/24/2013] [Indexed: 01/09/2023]
Abstract
Vascular Endothelial Growth Factor (VEGF) signal transduction is central to angiogenesis in development and in pathological conditions such as cancer, retinopathy and ischemic diseases. We constructed and validated a computational model of VEGFR2 trafficking and signaling, to study the role of receptor trafficking kinetics in modulating ERK phosphorylation in VEGF-stimulated endothelial cells. Trafficking parameters were optimized and validated against four previously published in vitro experiments. Based on these parameters, model simulations demonstrated interesting behaviors that may be highly relevant to understanding VEGF signaling in endothelial cells. First, at moderate VEGF doses, VEGFR2 phosphorylation and ERK phosphorylation are related in a log-linear fashion, with a stable duration of ERK activation; but with higher VEGF stimulation, phosphoERK becomes saturated, and its duration increases. Second, a large endosomal fraction of VEGFR2 makes the ERK activation reaction network less sensitive to perturbations in VEGF dosage. Third, extracellular-matrix-bound VEGF binds and activates VEGFR2, but by internalizing at a slower rate, matrix-bound VEGF-induced intracellular ERK phosphorylation is predicted to be greater in magnitude and more sustained, in agreement with experimental evidence. Fourth, different endothelial cell types appear to have different trafficking rates, which result in different levels of endosomal receptor localization and different ERK response profiles.
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Affiliation(s)
- Wan Hua Tan
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Ave., Baltimore, MD 21205, USA
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74
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Tan WH, Popel AS, Mac Gabhann F. Computational Model of Gab1/2-Dependent VEGFR2 Pathway to Akt Activation. PLoS One 2013; 8:e67438. [PMID: 23805312 PMCID: PMC3689841 DOI: 10.1371/journal.pone.0067438] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 05/20/2013] [Indexed: 11/18/2022] Open
Abstract
Vascular endothelial growth factor (VEGF) signal transduction is central to angiogenesis in development and in pathological conditions such as cancer, retinopathy and ischemic diseases. However, no detailed mass-action models of VEGF receptor signaling have been developed. We constructed and validated the first computational model of VEGFR2 trafficking and signaling, to study the opposing roles of Gab1 and Gab2 in regulation of Akt phosphorylation in VEGF-stimulated endothelial cells. Trafficking parameters were optimized against 5 previously published in vitro experiments, and the model was validated against six independent published datasets. The model showed agreement at several key nodes, involving scaffolding proteins Gab1, Gab2 and their complexes with Shp2. VEGFR2 recruitment of Gab1 is greater in magnitude, slower, and more sustained than that of Gab2. As Gab2 binds VEGFR2 complexes more transiently than Gab1, VEGFR2 complexes can recycle and continue to participate in other signaling pathways. Correspondingly, the simulation results show a log-linear relationship between a decrease in Akt phosphorylation and Gab1 knockdown while a linear relationship was observed between an increase in Akt phosphorylation and Gab2 knockdown. Global sensitivity analysis demonstrated the importance of initial-concentration ratios of antagonistic molecular species (Gab1/Gab2 and PI3K/Shp2) in determining Akt phosphorylation profiles. It also showed that kinetic parameters responsible for transient Gab2 binding affect the system at specific nodes. This model can be expanded to study multiple signaling contexts and receptor crosstalk and can form a basis for investigation of therapeutic approaches, such as tyrosine kinase inhibitors (TKIs), overexpression of key signaling proteins or knockdown experiments.
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Affiliation(s)
- Wan Hua Tan
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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75
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D'Haene N, Sauvage S, Maris C, Adanja I, Le Mercier M, Decaestecker C, Baum L, Salmon I. VEGFR1 and VEGFR2 involvement in extracellular galectin-1- and galectin-3-induced angiogenesis. PLoS One 2013; 8:e67029. [PMID: 23799140 PMCID: PMC3684579 DOI: 10.1371/journal.pone.0067029] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 05/15/2013] [Indexed: 01/13/2023] Open
Abstract
AIM Accumulating evidence suggests that extracellular galectin-1 and galectin-3 promote angiogenesis. Increased expression of galectin-1 and/or galectin-3 has been reported to be associated with tumour progression. Thus, it is critical to identify their influence on angiogenesis. METHODS We examined the individual and combined effects of galectin-1 and galectin-3 on endothelial cell (EC) growth and tube formation using two EC lines, EA.hy926 and HUVEC. The activation of vascular endothelial growth factor receptors (VEGFR1 and VEGFR2) was determined by ELISA and Western blots. We evaluated the VEGFR1 and VEGFR2 levels in endosomes by proximity ligation assay. RESULTS We observed different responses to exogenous galectins depending on the EC line. An enhanced effect on EA.hy926 cell growth and tube formation was observed when both galectins were added together. Focusing on this enhanced effect, we observed that together galectins induced the phosphorylation of both VEGFR1 and VEGFR2, whereas galectin-1 and -3 alone induced VEGFR2 phosphorylation only. In the same way, the addition of a blocking VEGFR1 antibody completely abolished the increase in tube formation induced by the combined addition of both galectins. In contrast, the addition of a blocking VEGFR2 antibody only partially inhibited this effect. Finally, the addition of both galectins induced a decrease in the VEGFR1 and VEGFR2 endocytic pools, with a significantly enhanced effect on the VEGFR1 endocytic pool. These results suggest that the combined action of galectin-1 and galectin-3 has an enhanced effect on angiogenesis via VEGFR1 activation, which could be related to a decrease in receptor endocytosis.
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Affiliation(s)
- Nicky D'Haene
- Department of Pathology, Erasme Hospital, Brussels, Belgium
| | | | - Calliope Maris
- Department of Pathology, Erasme Hospital, Brussels, Belgium
| | - Ivan Adanja
- Laboratory of Image Synthesis and Analysis, Brussels School of Engineering/Ecole polytechnique de Bruxelles; Université Libre de Bruxelles (ULB), Brussels, Belgium
| | | | - Christine Decaestecker
- Laboratory of Image Synthesis and Analysis, Brussels School of Engineering/Ecole polytechnique de Bruxelles; Université Libre de Bruxelles (ULB), Brussels, Belgium
- DIAPATH – Center for Microscopy and Molecular Imaging (CMMI), ULB, Gosselies, Belgium
| | - Linda Baum
- Department of Pathology and Laboratory Medicine, UCLA School of Medicine, Los Angeles, California, United States of America
| | - Isabelle Salmon
- Department of Pathology, Erasme Hospital, Brussels, Belgium
- DIAPATH – Center for Microscopy and Molecular Imaging (CMMI), ULB, Gosselies, Belgium
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76
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Imoukhuede PI, Dokun AO, Annex BH, Popel AS. Endothelial cell-by-cell profiling reveals the temporal dynamics of VEGFR1 and VEGFR2 membrane localization after murine hindlimb ischemia. Am J Physiol Heart Circ Physiol 2013; 304:H1085-93. [PMID: 23376830 DOI: 10.1152/ajpheart.00514.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
VEGF receptor (VEGFR) cell surface localization plays a critical role in transducing VEGF signaling toward angiogenic outcomes, and quantitative characterization of these parameters is critical to advancing computational models for predictive medicine. However, studies to this point have largely examined intact muscle; thus, essential data on the cellular localization of the receptors within the tissue are currently unknown. Therefore, our aims were to quantitatively analyze VEGFR localization on endothelial cells (ECs) from mouse hindlimb skeletal muscles after the induction of hindlimb ischemia, an established model for human peripheral artery disease. Flow cytometry was used to measure and compare the ex vivo surface localization of VEGFR1 and VEGFR2 on CD31(+)/CD34(+) ECs 3 and 10 days after unilateral ligation of the femoral artery. We determined that 3 days after hindlimb ischemia, VEGFR2 surface levels were decreased by 80% compared with ECs from the nonischemic limb; 10 days after ischemia, we observed a twofold increase in surface levels of the modulatory receptor, VEGFR1, along with increased proliferating cell nuclear antigen, urokinase plasminogen activator, and urokinase plasminogen activator receptor mRNA expression compared with the nonischemic limb. The significant upregulation of VEGFR1 surface levels indicates that VEGFR1 indeed plays a critical role in the ischemia-induced perfusion recovery process, a process that includes both angiogenesis and arteriogenesis. The quantification of these dissimilarities, for the first time ex vivo, provides insights into the balance of modulatory (VEGFR1) and proangiogenic (VEGFR2) receptors in ischemia and lays the foundation for systems biology approaches toward therapeutic angiogenesis.
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Affiliation(s)
- P I Imoukhuede
- Department of Bioengineering, University of Illinois, Urbana, Illinois 61801, USA.
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77
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Lee-Montiel FT, Imoukhuede PI. Engineering quantum dot calibration standards for quantitative fluorescent profiling. J Mater Chem B 2013; 1:6434-6441. [DOI: 10.1039/c3tb20904k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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78
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Imoukhuede PI, Popel AS. Expression of VEGF receptors on endothelial cells in mouse skeletal muscle. PLoS One 2012; 7:e44791. [PMID: 22984559 PMCID: PMC3440347 DOI: 10.1371/journal.pone.0044791] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 08/13/2012] [Indexed: 01/01/2023] Open
Abstract
VEGFR surface localization plays a critical role in converting extracellular VEGF signaling towards angiogenic outcomes, and the quantitative characterization of these parameters is critical for advancing computational models; however the levels of these receptors on blood vessels is currently unknown. Therefore our aim is to quantitatively determine the VEGFR localization on endothelial cells from mouse hindlimb skeletal muscles. We contextualize this VEGFR quantification through comparison to VEGFR-levels on cells in vitro. Using quantitative fluorescence we measure and compare the levels of VEGFR1 and VEGFR2 on endothelial cells isolated from C57BL/6 and BALB/c gastrocnemius and tibialis anterior hindlimb muscles. Fluorescence measurements are calibrated using beads with known numbers of phycoerythrin molecules. The data show a 2-fold higher VEGFR1 surface localization relative to VEGFR2 with 2,000-3,700 VEGFR1/endothelial cell and 1,300-2,000 VEGFR2/endothelial cell. We determine that endothelial cells from the highly glycolytic muscle, tibialis anterior, contain 30% higher number of VEGFR1 surface receptors than gastrocnemius; BALB/c mice display ~17% higher number of VEGFR1 than C57BL/6. When we compare these results to mouse fibroblasts in vitro, we observe high levels of VEGFR1 (35,800/cell) and very low levels of VEGFR2 (700/cell), while in human endothelial cells in vitro, we observe that the balance of VEGFRs is inverted, with higher levels VEGFR2 (5,800/cell) and lower levels of VEGFR1 (1,800/cell). Our studies also reveal significant cell-to-cell heterogeneity in receptor expression, and the quantification of these dissimilarities ex vivo for the first time provides insight into the balance of anti-angiogenic or modulatory (VEGFR1) and pro-angiogenic (VEGFR2) signaling.
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Affiliation(s)
- Princess I. Imoukhuede
- Department of Bioengineering, University of Illinois Urbana Champaign, Urbana, Illinois, United States of America
| | - Aleksander S. Popel
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
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79
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The role of heterodimerization between VEGFR-1 and VEGFR-2 in the regulation of endothelial cell homeostasis. Nat Commun 2012; 3:972. [PMID: 22828632 DOI: 10.1038/ncomms1977] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 06/27/2012] [Indexed: 02/06/2023] Open
Abstract
VEGF-A activity is tightly regulated by ligand and receptor availability. Here we investigate the physiological function of heterodimers between VEGF receptor-1 (VEGFR-1; Flt-1) and VEGFR-2 (KDR; Flk-1) (VEGFR(1-2)) in endothelial cells with a synthetic ligand that binds specifically to VEGFR(1-2). The dimeric ligand comprises one VEGFR-2-specific monomer (VEGF-E) and a VEGFR-1-specific monomer (PlGF-1). Here we show that VEGFR(1-2) activation mediates VEGFR phosphorylation, endothelial cell migration, sustained in vitro tube formation and vasorelaxation via the nitric oxide pathway. VEGFR(1-2) activation does not mediate proliferation or elicit endothelial tissue factor production, confirming that these functions are controlled by VEGFR-2 homodimers. We further demonstrate that activation of VEGFR(1-2) inhibits VEGF-A-induced prostacyclin release, phosphorylation of ERK1/2 MAP kinase and mobilization of intracellular calcium from primary endothelial cells. These findings indicate that VEGFR-1 subunits modulate VEGF activity predominantly by forming heterodimer receptors with VEGFR-2 subunits and such heterodimers regulate endothelial cell homeostasis.
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Latham AM, Odell AF, Mughal NA, Issitt T, Ulyatt C, Walker JH, Homer-Vanniasinkam S, Ponnambalam S. A biphasic endothelial stress-survival mechanism regulates the cellular response to vascular endothelial growth factor A. Exp Cell Res 2012; 318:2297-311. [PMID: 22796052 DOI: 10.1016/j.yexcr.2012.06.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 06/01/2012] [Accepted: 06/28/2012] [Indexed: 01/10/2023]
Abstract
Vascular endothelial growth factor A (VEGF-A) is an essential cytokine that regulates endothelial function and angiogenesis. VEGF-A binding to endothelial receptor tyrosine kinases such as VEGFR1 and VEGFR2 triggers cellular responses including survival, proliferation and new blood vessel sprouting. Increased levels of a soluble VEGFR1 splice variant (sFlt-1) correlate with endothelial dysfunction in pathologies such as pre-eclampsia; however the cellular mechanism(s) underlying the regulation and function of sFlt-1 are unclear. Here, we demonstrate the existence of a biphasic stress response in endothelial cells, using serum deprivation as a model of endothelial dysfunction. The early phase is characterized by a high VEGFR2:sFlt-1 ratio, which is reversed in the late phase. A functional consequence is a short-term increase in VEGF-A-stimulated intracellular signaling. In the late phase, sFlt-1 is secreted and deposited at the extracellular matrix. We hypothesized that under stress, increased endothelial sFlt-1 levels reduce VEGF-A bioavailability: VEGF-A treatment induces sFlt-1 expression at the cell surface and VEGF-A silencing inhibits sFlt-1 anchorage to the extracellular matrix. Treatment with recombinant sFlt-1 inhibits VEGF-A-stimulated in vitro angiogenesis and sFlt-1 silencing enhances this process. In this response, increased VEGFR2 levels are regulated by the phosphatidylinositol-3-kinase and PKB/Akt signaling pathways and increased sFlt-1 levels by the ERK1/2 signaling pathway. We conclude that during serum withdrawal, cellular sensing of environmental stress modulates sFlt-1 and VEGFR2 levels, regulating VEGF-A bioavailability and ensuring cell survival takes precedence over cell proliferation and migration. These findings may underpin an important mechanism contributing to endothelial dysfunction in pathological states.
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Affiliation(s)
- Antony M Latham
- Endothelial Cell Biology Unit, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
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Finley SD, Popel AS. Predicting the effects of anti-angiogenic agents targeting specific VEGF isoforms. AAPS JOURNAL 2012; 14:500-9. [PMID: 22547351 DOI: 10.1208/s12248-012-9363-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 04/13/2012] [Indexed: 01/04/2023]
Abstract
Vascular endothelial growth factor (VEGF) is a key mediator of angiogenesis, whose effect on cancer growth and development is well characterized. Alternative splicing of VEGF leads to several different isoforms, which are differentially expressed in various tumor types and have distinct functions in tumor blood vessel formation. Many cancer therapies aim to inhibit angiogenesis by targeting VEGF and preventing intracellular signaling leading to tumor vascularization; however, the effects of targeting specific VEGF isoforms have received little attention in the clinical setting. In this work, we investigate the effects of selectively targeting a single VEGF isoform, as compared with inhibiting all isoforms. We utilize a molecular-detailed whole-body compartment model of VEGF transport and kinetics in the presence of breast tumor. The model includes two major VEGF isoforms, VEGF(121) and VEGF(165), receptors VEGFR1 and VEGFR2, and co-receptors Neuropilin-1 and Neuropilin-2. We utilize the model to predict the concentrations of free VEGF, the number of VEGF/VEGFR2 complexes (considered to be pro-angiogenic), and the receptor occupancy profiles following inhibition of VEGF using isoform-specific anti-VEGF agents. We predict that targeting VEGF(121) leads to a 54% and 84% reduction in free VEGF in tumors that secrete both VEGF isoforms or tumors that overexpress VEGF(121), respectively. Additionally, 21% of the VEGFR2 molecules in the blood are ligated following inhibition of VEGF(121), compared with 88% when both isoforms are targeted. Targeting VEGF(121) reduces tumor free VEGF and is an effective treatment strategy. Our results provide a basis for clinical investigation of isoform-specific anti-VEGF agents.
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Affiliation(s)
- Stacey D Finley
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA.
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Pharmacokinetics and pharmacodynamics of VEGF-neutralizing antibodies. BMC SYSTEMS BIOLOGY 2011; 5:193. [PMID: 22104283 PMCID: PMC3229549 DOI: 10.1186/1752-0509-5-193] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/21/2011] [Indexed: 12/20/2022]
Abstract
Background Vascular endothelial growth factor (VEGF) is a potent regulator of angiogenesis, and its role in cancer biology has been widely studied. Many cancer therapies target angiogenesis, with a focus being on VEGF-mediated signaling such as antibodies to VEGF. However, it is difficult to predict the effects of VEGF-neutralizing agents. We have developed a whole-body model of VEGF kinetics and transport under pathological conditions (in the presence of breast tumor). The model includes two major VEGF isoforms VEGF121 and VEGF165, receptors VEGFR1, VEGFR2 and co-receptors Neuropilin-1 and Neuropilin-2. We have added receptors on parenchymal cells (muscle fibers and tumor cells), and incorporated experimental data for the cell surface density of receptors on the endothelial cells, myocytes, and tumor cells. The model is applied to investigate the action of VEGF-neutralizing agents (called "anti-VEGF") in the treatment of cancer. Results Through a sensitivity study, we examine how model parameters influence the level of free VEGF in the tumor, a measure of the response to VEGF-neutralizing drugs. We investigate the effects of systemic properties such as microvascular permeability and lymphatic flow, and of drug characteristics such as the clearance rate and binding affinity. We predict that increasing microvascular permeability in the tumor above 10-5 cm/s elicits the undesired effect of increasing tumor interstitial VEGF concentration beyond even the baseline level. We also examine the impact of the tumor microenvironment, including receptor expression and internalization, as well as VEGF secretion. We find that following anti-VEGF treatment, the concentration of free VEGF in the tumor can vary between 7 and 233 pM, with a dependence on both the density of VEGF receptors and co-receptors and the rate of neuropilin internalization on tumor cells. Finally, we predict that free VEGF in the tumor is reduced following anti-VEGF treatment when VEGF121 comprises at least 25% of the VEGF secreted by tumor cells. Conclusions This study explores the optimal drug characteristics required for an anti-VEGF agent to have a therapeutic effect and the tumor-specific properties that influence the response to therapy. Our model provides a framework for investigating the use of VEGF-neutralizing drugs for personalized medicine treatment strategies.
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Abstract
Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis – the growth of new microvessels from existing microvasculature. Angiogenesis is a complex process involving numerous molecular species, and to better understand it, a systems biology approach is necessary. In vivo preclinical experiments in the area of angiogenesis are typically performed in mouse models; this includes drug development targeting VEGF. Thus, to quantitatively interpret such experimental results, a computational model of VEGF distribution in the mouse can be beneficial. In this paper, we present an in silico model of VEGF distribution in mice, determine model parameters from existing experimental data, conduct sensitivity analysis, and test the validity of the model. The multiscale model is comprised of two compartments: blood and tissue. The model accounts for interactions between two major VEGF isoforms (VEGF120 and VEGF164) and their endothelial cell receptors VEGFR-1, VEGFR-2, and co-receptor neuropilin-1. Neuropilin-1 is also expressed on the surface of parenchymal cells. The model includes transcapillary macromolecular permeability, lymphatic transport, and macromolecular plasma clearance. Simulations predict that the concentration of unbound VEGF in the tissue is approximately 50-fold greater than in the blood. These concentrations are highly dependent on the VEGF secretion rate. Parameter estimation was performed to fit the simulation results to available experimental data, and permitted the estimation of VEGF secretion rate in healthy tissue, which is difficult to measure experimentally. The model can provide quantitative interpretation of preclinical animal data and may be used in conjunction with experimental studies in the development of pro- and anti-angiogenic agents. The model approximates the normal tissue as skeletal muscle and includes endothelial cells to represent the vasculature. As the VEGF system becomes better characterized in other tissues and cell types, the model can be expanded to include additional compartments and vascular elements.
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Forsten-Williams K, Kurtagic E, Nugent MA. Complex receptor-ligand dynamics control the response of the VEGF system to protease injury. BMC SYSTEMS BIOLOGY 2011; 5:170. [PMID: 22014244 PMCID: PMC3253741 DOI: 10.1186/1752-0509-5-170] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 10/21/2011] [Indexed: 12/22/2022]
Abstract
BACKGROUND Vascular homeostasis and response to injury are dependent on the coordinated activity of growth factors such as vascular endothelial growth factor-A (VEGF). VEGF signaling is mediated by VEGF receptors 1 (VEGFR1) and 2 (VEGFR2). VEGF also binds to extracellular matrix (ECM) and neuropilin (NP), a cell surface glycoprotein that enhances VEGF binding to VEGFR2 while inhibiting VEGF-VEGFR1 interactions. Proteases such as neutrophil elastase release VEGF bound to ECM; however, this results in proteolytic processing of VEGF to a smaller species termed VEGF fragment (VEGFf). We hypothesized that the generation and presence of VEGFf would have significant effects on the binding distribution of VEGF. RESULTS We show that VEGFf, unlike VEGF, does not bind ECM, fibronectin, or NP-1. Using computational simulations, we find that excess VEGFf can lead to increased binding of VEGF to VEGFR2 through VEGFf binding to VEGFR1 and subsequent liberation of NP-1. We show experimentally that VEGF-induced migration has a biphasic response to conversion of VEGF to VEGFf. Simulations suggest that a simple change in VEGFR1 or VEGFR2 complexes are unlikely to be responsible and that a more complex integration of signals is more likely involved. CONCLUSIONS These findings suggest that proteolytic damage at sites of tissue injury and inflammation has the potential to modulate the VEGF system through a complex process and highlight the need for quantitative analysis to reveal mechanisms of growth factor control.
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Affiliation(s)
- Kimberly Forsten-Williams
- Department of Chemical Engineering, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA.
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