Biomedical subjects

Zhenping Zhu

Publications and source records attributed to Zhenping Zhu.

At least 19 recordsLinked to original sources

PubMed2006

Particle-wire-tube mechanism for carbon nanotube evolution.

The synthesis of carbon nanotubes (CNTs) has been proved to be greatly promoted by vapor metal catalysts, but the fast reaction feature and the required high-temperature environment involved in CNT evolution usually make it difficult for an insight into the evolution mechanism. Here, we successfully freeze the synthetic reaction at intermediary stages and observe the detailed morphologies and structures of the obtained intermediates and various objects related to carbon nanotubes. It is unveiled that there is a kindred evolution linkage among carbon nanoparticles, nanowires, and nanotubes in the vapor catalyst-involved synthetic processes: tiny carbon nanoparticles first form from a condensation of gaseous carbon species and then self-assemble into nanowires driven by an anisotropic interaction, and the nanowires finally develop into nanotubes, as a consequence of particle coalescence and structural crystallization. The function of metals is to promote the anisotropic interactions between the nanoparticles and the structural crystallization. An annealing transformation of carbon nanoparticles into nanotubes is also achieved, which gives further evidence for the evolution mechanism.

Journal Article↗

PubMed2006

Single variable domain antibody as a versatile building block for the construction of IgG-like bispecific antibodies.

Bispecific antibodies (BsAb) have been traditionally utilized to redirect cytotoxic effector cells and agents to kill tumor cells expressing the target antigens. Recently a new concept is emerging to develop BsAb that simultaneously block the functions of two tumor-associated targets, eg., growth factor receptors, for enhanced antitumor efficacies. Broad clinical applications of BsAb have been, and still are, significantly hampered by the difficulty in producing the materials in sufficient quantity and quality by traditional approaches. Here we describe a recombinant approach for the production of an Fc domain-containing, IgG-like tetravalent BsAb, using a single variable domain (sVD) antibody as a versatile building block. In this method, a sVD of a defined specificity is genetically fused to either the N-terminus of the light chain or the C-terminus of the heavy chain of a functional IgG antibody of a different specificity. A model BsAb was constructed using a sVD to mouse platelet derived growth factor receptor alpha and a conventional IgG antibody to mouse platelet derived growth factor receptor beta. The BsAb were expressed in mammalian cells and purified to homogeneity by a one-step Protein A affinity chromatography. Further, the BsAb retained the antigen binding specificity and the receptor neutralizing activity of both of its parent antibodies. Importantly, the BsAb inhibited the activation of both its target receptors in tumor cells stimulated by both platelet derived growth factor AA and BB, whereas the parent monospecific antibody only inhibited the activation of a single receptor stimulated by its cognate ligand. This format of BsAb should be readily applicable to the production of other BsAb recognizing any pairs of antigens.

Animals↗

PubMed2006

Discovery of small molecule inhibitors of integrin alphavbeta3 through structure-based virtual screening.

Inhibitors of integrin alphavbeta3 have been implicated in the treatment of a variety of diseases, including tumor metastasis, neovascularization, osteoporosis, and rheumatoid arthritis. It is therefore desirable to develop new types of small molecule inhibitors of integrin alphavbeta3. Here we describe the discovery of novel classes of small molecule inhibitors, via structure-based virtual screening, that target the ligand binding site of integrin alphavbeta3. Application of the docking procedure for screening of a commercially available compound database resulted in a 1774-fold reduction in the size of the screening set (88695 to 50 compounds) and gave a hit-rate of 14% upon biological evaluation (IC50 value ranging from 30 to 200 microM). The best hit, compound 37, 3,4-dichloro-phenylbiguanide, showed inhibitory activity, in a time- and dose-dependent manner, in both cell motility and angiogenesis assays. Based on the best hit, compound 37, a more effective derivative compound 62 has been identified. Furthermore, molecular graphics analyses of a series of substituted phenylbiguanides were carried out to predict the binding mode between the active compounds and integrin alphavbeta3. Our results indicate that the substituted phenylbiguanides might be involved in the inhibition of bivalent cation-mediated ligand binding of integrin alphavbeta3.

Biguanides↗

PubMed2006

Therapeutic implications of a human neutralizing antibody to the macrophage-stimulating protein receptor tyrosine kinase (RON), a c-MET family member.

RON is a member of the c-MET receptor tyrosine kinase family. Like c-MET, RON is expressed by a variety of epithelial-derived tumors and cancer cell lines and it is thought to play a functional role in tumorigenesis. To date, antagonists of RON activity have not been tested in vivo to validate RON as a potential cancer target. In this report, we used an antibody phage display library to generate IMC-41A10, a human immunoglobulin G1 (IgG1) antibody that binds with high affinity (ED50 = 0.15 nmol/L) to RON and effectively blocks interaction with its ligand, macrophage-stimulating protein (MSP; IC50 = 2 nmol/L). We found IMC-41A10 to be a potent inhibitor of receptor and downstream signaling, cell migration, and tumorigenesis. It antagonized MSP-induced phosphorylation of RON, mitogen-activated protein kinase (MAPK), and AKT in several cancer cell lines. In HT-29 colon, NCI-H292 lung, and BXPC-3 pancreatic cancer xenograft tumor models, IMC-41A10 inhibited tumor growth by 50% to 60% as a single agent, and in BXPC-3 xenografts, it led to tumor regressions when combined with Erbitux. Western blot analyses of HT-29 and NCI-H292 xenograft tumors treated with IMC-41A10 revealed a decrease in MAPK phosphorylation compared with control IgG-treated tumors, suggesting that inhibition of MAPK activity may be required for the antitumor activity of IMC-41A10. To our knowledge, this is the first demonstration that a RON antagonist and specifically an inhibitory antibody of RON negatively affects tumorigenesis. Another major contribution of this report is an extensive analysis of RON expression in approximately 100 cancer cell lines and approximately 300 patient tumor samples representing 10 major cancer types. Taken together, our results highlight the potential therapeutic usefulness of RON activity inhibition in human cancers.

Animals↗

PubMed2006

Overexpression of sorcin in multidrug resistant human leukemia cells and its role in regulating cell apoptosis.

In an attempt to identify novel proteins involved in the emergence of multidrug resistance (MDR) in leukemia cells, we adopted a proteomics approach to analyze protein expression patterns in leukemia cell lines, K562, and its MDR counterpart, K562/A02. Combining high-resolution two-dimensional gel electrophoresis and mass spectrometry, we compared the protein expression profiles between K562 and K562/A02. A total number of 22 protein spots with altered abundances of more than 2-fold were detected and 14 proteins were successfully identified. Consistent with our previous observations by cDNA microarray, sorcin, a 22-kDa calcium-binding protein, was also identified by this proteomic approach with a 10.4-fold up-regulation in K562/A02 cells. Overexpression of sorcin protein in K562 cells by gene transfection led to significantly reduced cytosolic calcium level and increased resistance to cell apoptosis. Further, leukemia cell lines over-expressing sorcin also showed up-regulation of Bcl-2, along with decreased level of Bax. Taken together, our results suggest that sorcin plays an important role in the emergence of MDR in leukemia cells via regulating cell apoptosis pathways, thus may represent both a new MDR marker for prognosis and a good target for anti-MDR drug development.

Antineoplastic Agents, Phytogenic↗

PubMed2006

Potent neutralization of VEGF biological activities with a fully human antibody Fab fragment directed against VEGF receptor 2.

Compelling evidence suggest that vascular endothelial growth factor (VEGF) and its receptors, especially receptor 2 (VEGFR2, or kinase insert domain-containing receptor, KDR), play a critical role in angiogenesis under both physiological and pathological conditions, including cancer and angiogenic retinopathies such as age-related macular degeneration (AMD). To this end, inhibition of angiogenesis with antagonists to either VEGF or KDR has yielded significant therapeutic efficacy both in preclinical studies in animal models and in clinical trials in patients with cancer and AMD. We previously reported the identification of a high affinity, fully human anti-KDR antibody fragment, 1121B Fab, through a highly stringent affinity maturation process with a Fab originally isolated from a naïve human antibody phage display library. In this study, we demonstrate that 1121B Fab is able to strongly block KDR/VEGF interaction, resulting in potent inhibition of an array of biological activities of VEGF, including activation of the receptor and its signaling pathway, intracellular calcium mobilization, and migration and proliferation of endothelial cells. Taken together, our data lend strong support to the further development of 1121B Fab fragment as an anti-angiogenesis agent in both cancer and angiogenic retinopathies.

Animals↗

PubMed2006

Cytokine-mediated deployment of SDF-1 induces revascularization through recruitment of CXCR4+ hemangiocytes.

The mechanisms through which hematopoietic cytokines accelerate revascularization are unknown. Here, we show that the magnitude of cytokine-mediated release of SDF-1 from platelets and the recruitment of nonendothelial CXCR4+ VEGFR1+ hematopoietic progenitors, 'hemangiocytes,' constitute the major determinant of revascularization. Soluble Kit-ligand (sKitL), thrombopoietin (TPO, encoded by Thpo) and, to a lesser extent, erythropoietin (EPO) and granulocyte-macrophage colony-stimulating factor (GM-CSF) induced the release of SDF-1 from platelets, enhancing neovascularization through mobilization of CXCR4+ VEGFR1+ hemangiocytes. Although revascularization of ischemic hindlimbs was partially diminished in mice deficient in both GM-CSF and G-CSF (Csf2-/- Csf3-/-), profound impairment in neovascularization was detected in sKitL-deficient Mmp9-/- as well as thrombocytopenic Thpo-/- and TPO receptor-deficient (Mpl-/-) mice. SDF-1-mediated mobilization and incorporation of hemangiocytes into ischemic limbs were impaired in Thpo-/-, Mpl-/- and Mmp9-/- mice. Transplantation of CXCR4+ VEGFR1+ hemangiocytes into Mmp9-/- mice restored revascularization, whereas inhibition of CXCR4 abrogated cytokine- and VEGF-A-mediated mobilization of CXCR4+ VEGFR1+ cells and suppressed angiogenesis. In conclusion, hematopoietic cytokines, through graded deployment of SDF-1 from platelets, support mobilization and recruitment of CXCR4+ VEGFR1+ hemangiocytes, whereas VEGFR1 is essential for their angiogenic competency for augmenting revascularization. Delivery of SDF-1 may be effective in restoring angiogenesis in individuals with vasculopathies.

Animals↗

PubMed2006

Single variable domain-IgG fusion. A novel recombinant approach to Fc domain-containing bispecific antibodies.

Both laboratory and early clinical studies to date have demonstrated that bispecific antibodies (BsAb) may have potentially significant application in cancer therapy. The clinical development of BsAb as therapeutics has been hampered, however, by the difficulty in preparing the materials in sufficient quantity and quality by traditional methods. In recent years, a variety of recombinant methods has been developed for efficient production of BsAb, both as antibody fragments and as full-length IgG-like molecules. Here we describe a novel recombinant approach for the production of an Fc domain-containing, IgG-like tetravalent BsAb, with two antigen-binding sites to each of its target antigens, by genetically fusing a single variable domain antibody to the N terminus of the light chain of a functional IgG antibody of different specificity. A model BsAb was constructed using a single variable domain antibody to mouse platelet-derived growth factor receptor alpha and a conventional IgG antibody to mouse vascular endothelial growth factor receptor 2. The BsAb was expressed in mammalian cells and purified to homogeneity by one-step protein A affinity chromatography. Furthermore, the BsAb retains the antigen binding specificity and the receptor neutralizing activity of both of its parent antibodies. This design and expression of Fc domain-containing, IgG-like BsAb should be applicable to the construction of similar BsAb from antibodies recognizing any pair of antigens.

Amino Acid Sequence↗

PubMed2006

Intrabody-based approaches to cancer therapy: status and prospects.

Continuing developments from the study of cancer at the molecular level are yielding increasing numbers of targets that may be used for therapeutic intervention. Advances in the field of antibody engineering over the past several decades have given scientists the capability of directing the highly specific interaction of antibodies with antigens inward, to the intracellular compartments of living cells. These intracellular antibodies, i.e., intrabodies, are being developed to bind to, neutralize, or modify the function or localization of cancer-related targets and thereby affect the malignant phenotype. This has resulted in a promising new tool for the study and treatment of cancer. Due to recent advances in the development of the antibody engineering technologies, increasing numbers of intrabodies are being exploited to a growing list of cancer-related, as well as other disease targets. There are still, however, many technical issues, particularly related to clinical applications of the intrabodies, that must be addressed before the full promise of this class of therapeutic agent is realized. This review will focus on the recent progress in the generation and use of intrabodies in the field of oncology. The technical issues associated with their further development will also be discussed.

Animals↗

PubMed2006

Development of heparanase inhibitors for anti-cancer therapy.

Heparanase is an endo-beta-D-glucuronidase that degrades heparan sulfate glycosaminoglycan side chains of the proteoglycans in extracellular matrix and basement membrane. Heparanase enzymatic activity is important in the promotion of tumor angiogenesis, primary tumor growth, invasion, and metastasis. Expression of heparanase in many tumor types conversely correlates with prognosis. Much progress has been made in studying the regulation of heparanase expression, processing and activation. The interaction between heparanase and its substrate heparan sulfate has been well characterized. The fact that heparanase was identified as the single predominant heparan sulfate-degrading enzyme in human cancer sparked considerable interest in developing heparanase inhibitors for potential therapeutic applications. Recent progress in drug development led to several classes of heparanase inhibitors, including chemically modified natural products, small molecule inhibitors, and antibodies. Some of these inhibitors have demonstrated potent activities to inhibit tumor angiogenesis, tumor progress, or tumor metastasis. A leading compound, PI-88, is currently being evaluated in clinical phase II trials in patients with melanoma, liver, or lung cancers. This review summarizes the recent progress in heparanase biochemical research and the development of heparanase antagonists as novel anti-cancer therapeutics.

Biomarkers↗

PubMed2006

Bispecific antibodies for dual-modality cancer therapy: killing two signaling cascades with one stone.

The additive and synergistic therapeutic effects derived from combinations of chemotherapeutic drugs and radiation have established an indispensable paradigm: cancer must be attacked on multiple fronts. However, the increased antitumor efficacy of such combinational regimens is also associated with severe systemic toxicity, as these drugs cannot selectively target tumor cells. Monoclonal antibodies (mAbs), which have exquisite specificity for their antigens, are becoming an increasingly important class of antitumor agents, as they enhance the efficacy of various therapeutic regimens without significantly increasing systemic toxicity. Furthermore, preclinical and early clinical evidence indicate that combinations of antibody-based drugs provide even greater efficacy with minimal side effects. Unfortunately, the research, manufacturing and regulatory costs of mAb development pose a significant barrier to the use of antibody-based combination therapies. An emerging alternative is the use of dual-targeting bispecific antibodies (BsAbs). BsAbs are derived from the recombination of variable domains of two antibodies with different specificities; BsAbs are thus capable of binding both antigens of their parental antibodies. With the recent progress that has been made in antibody engineering technology, BsAbs that simultaneously target two tumor-associated molecules (eg, growth factor receptors) are being heralded for their potential to deliver two therapeutic moieties in a single molecule.

Animals↗

PubMed2005

VEGFR1-positive haematopoietic bone marrow progenitors initiate the pre-metastatic niche.

The cellular and molecular mechanisms by which a tumour cell undergoes metastasis to a predetermined location are largely unknown. Here we demonstrate that bone marrow-derived haematopoietic progenitor cells that express vascular endothelial growth factor receptor 1 (VEGFR1; also known as Flt1) home to tumour-specific pre-metastatic sites and form cellular clusters before the arrival of tumour cells. Preventing VEGFR1 function using antibodies or by the removal of VEGFR1(+) cells from the bone marrow of wild-type mice abrogates the formation of these pre-metastatic clusters and prevents tumour metastasis, whereas reconstitution with selected Id3 (inhibitor of differentiation 3)-competent VEGFR1+ cells establishes cluster formation and tumour metastasis in Id3 knockout mice. We also show that VEGFR1+ cells express VLA-4 (also known as integrin alpha4beta1), and that tumour-specific growth factors upregulate fibronectin--a VLA-4 ligand--in resident fibroblasts, providing a permissive niche for incoming tumour cells. Conditioned media obtained from distinct tumour types with unique patterns of metastatic spread redirected fibronectin expression and cluster formation, thereby transforming the metastatic profile. These findings demonstrate a requirement for VEGFR1+ haematopoietic progenitors in the regulation of metastasis, and suggest that expression patterns of fibronectin and VEGFR1+VLA-4+ clusters dictate organ-specific tumour spread.

Animals↗

PubMed2005

Self-catalytic behavior of carbon nanotubes.

Self-catalytic behavior of multi-walled carbon nanotubes is proposed and validated experimentally under the conditions in which metal catalysis was previously figured to work only. The self-catalysis could support the nanotube nucleation and radial and axial developing processes. This result should lead to a new and better understanding of the growth mechanism of carbon nanotubes in a metal catalytic process.

Journal Article↗

PubMed2005

VEGFR-1 (FLT-1) activation modulates acute lymphoblastic leukemia localization and survival within the bone marrow, determining the onset of extramedullary disease.

The presence of persistent circulating leukemia cells, or engrafted into extramedullary tissues, is a bad prognostic factor for patients with acute leukemia. However, little is known about the mechanisms that regulate the exit of leukemia cells from the bone marrow (BM) microenvironment. We reveal that vascular endothelial growth factor receptor 1 (FLT-1) modulates acute leukemia distribution within the BM, along VEGF and PlGF gradients, regulating leukemia survival and exit into the peripheral circulation. FLT-1 activation on acute lymphoblastic leukemia (ALL) cells results in cell migration and proliferation in vitro, whereas in vivo FLT-1-overexpressing cells accumulate in the BM epiphysis of nonobese diabetic-severe combined immunodeficient (NOD-SCID) recipients and are detected in circulation 2 weeks after inoculation. In turn, FLT-1 neutralization affects leukemia localization (now in the BM diaphysis), increases leukemia apoptosis, and impedes the exit of ALL cells, prolonging the survival of inoculated mice. We demonstrate further that FLT-1-induced cell migration involves actin polymerization and lipid raft formation. Taken together, we show that FLT-1 regulates the BM localization of ALL cells, determining their survival and exit into the circulation and ultimately the survival of inoculated recipients. FLT-1 targeting on subsets of acute leukemias may delay the onset of extramedullary disease, which may be advantageous in combinatorial therapeutic settings.

Apoptosis↗

PubMed2005

Granulocyte colony-stimulating factor promotes neovascularization by releasing vascular endothelial growth factor from neutrophils.

The granulocyte colony-stimulating factor (G-CSF) promotes angiogenesis. However, the exact mechanism is not known. We demonstrate that vascular endothelial growth factor (VEGF) was released by Gr-1+CD11b- neutrophils but not Gr-1-CD11b+ monocytes prestimulated with G-CSF in vitro and in vivo. Similarly, in vivo, concomitant with an increase in neutrophil numbers in circulation, G-CSF augmented plasma VEGF level in vivo. Local G-CSF administration into ischemic tissue increased capillary density and provided a functional vasculature and contributed to neovascularization of ischemic tissue. Blockade of the VEGF pathway abrogated G-CSF-induced angiogenesis. On the other hand, as we had shown previously, VEGF can induce endothelial progenitor cell (EPC) mobilization. Here, we show that G-CSF also augmented the number of circulating VEGF receptor-2 (VEGFR2) EPCs as compared with untreated controls. Blocking the VEGF/VEGFR1, but to a much lesser extent, the VEGF/VEGFR2 pathway in G-CSF-treated animals delayed tissue revascularization in a hindlimb model. These data clearly show that G-CSF modulates angiogenesis by increasing myelomonocytic cells (VEGFR1+ neutrophils) and their release of VEGF. Our results indicated that administration of G-CSF into ischemic tissue provides a novel and safe therapeutic strategy to improve neovascularization.

Analysis of Variance↗

PubMed2005

Combretastatin A4 phosphate induces rapid regression of tumor neovessels and growth through interference with vascular endothelial-cadherin signaling.

The molecular and cellular pathways that support the maintenance and stability of tumor neovessels are not well defined. The efficacy of microtubule-disrupting agents, such as combretastatin A4 phosphate (CA4P), in inducing rapid regression of specific subsets of tumor neovessels has opened up new avenues of research to identify factors that support tumor neoangiogenesis. Herein, we show that CA4P selectively targeted endothelial cells, but not smooth muscle cells, and induced regression of unstable nascent tumor neovessels by rapidly disrupting the molecular engagement of the endothelial cell-specific junctional molecule vascular endothelial-cadherin (VE-cadherin) in vitro and in vivo in mice. CA4P increases endothelial cell permeability, while inhibiting endothelial cell migration and capillary tube formation predominantly through disruption of VE-cadherin/beta-catenin/Akt signaling pathway, thereby leading to rapid vascular collapse and tumor necrosis. Remarkably, stabilization of VE-cadherin signaling in endothelial cells with adenovirus E4 gene or ensheathment with smooth muscle cells confers resistance to CA4P. CA4P synergizes with low and nontoxic doses of neutralizing mAbs to VE-cadherin by blocking assembly of neovessels, thereby inhibiting tumor growth. These data suggest that the microtubule-targeting agent CA4P selectively induces regression of unstable tumor neovessels, in part through disruption of VE-cadherin signaling. Combined treatment with anti-VE-cadherin agents in conjunction with microtubule-disrupting agents provides a novel synergistic strategy to selectively disrupt assembly and induce regression of nascent tumor neovessels, with minimal toxicity and without affecting normal stabilized vasculature.

Animals↗

PubMed2005

Sorcin, an important gene associated with multidrug-resistance in human leukemia cells.

Sorcin, or soluble resistance-related calcium-binding protein, is a 22kD calcium-binding protein initially identified in many mutli-drug resistant (MDR) cell lines. We previously observed by gene profiling that sorcin is significantly up-regulated in a doxorubicin-induced MDR leukemia cell line, K562/A02, over its parent cells. We have also demonstrated that the level of sorcin expression in leukemia patients correlates not only directly with that of the mdr1 gene, but also inversely with patients' response to chemotherapies and overall prognosis. In this report, we have carried out experiments to dissect out the contribution of sorcin by itself to drug resistant phenotype in K562 cells. Overexpression of sorcin protein by gene transfection in K562 cells resulted in increased drug resistance, from 4.1- to 22.5-fold, to a variety of chemotherapeutic agents, including doxorubicin, etoposide, homoharringtonine and vincristine. On the other hand, inhibition of sorcin expression in both MDR K562/A02 and the sorcin-transfected K562 cells with sorcin-targeting small interfering RNA led to varying extent of reversal of drug resistance. These results confirm that sorcin is an important gene associated with the development of MDR in leukemia cells.

Base Sequence↗

PubMed2005

Low-dose irradiation promotes tissue revascularization through VEGF release from mast cells and MMP-9-mediated progenitor cell mobilization.

Mast cells accumulate in tissues undergoing angiogenesis during tumor growth, wound healing, and tissue repair. Mast cells can secrete angiogenic factors such as vascular endothelial growth factor (VEGF). Ionizing irradiation has also been shown to have angiogenic potential in malignant and nonmalignant diseases. We observed that low-dose irradiation fosters mast cell-dependent vascular regeneration in a limb ischemia model. Irradiation promoted VEGF production by mast cells in a matrix metalloproteinase-9 (MMP-9)-dependent manner. Irradiation, through MMP-9 up-regulated by VEGF in stromal and endothelial cells, induced the release of Kit-ligand (KitL). Irradiation-induced VEGF promoted migration of mast cells from the bone marrow to the ischemic site. Irradiation-mediated release of KitL and VEGF was impaired in MMP-9-deficient mice, resulting in a reduced number of tissue mast cells and delayed vessel formation in the ischemic limb. Irradiation-induced vasculogenesis was abrogated in mice deficient in mast cells (steel mutant, Sl/Sl(d) mice) and in mice in which the VEGF pathway was blocked. Irradiation did not induce progenitor mobilization in Sl/Sl(d) mice. We conclude that increased recruitment and activation of mast cells following irradiation alters the ischemic microenvironment and promotes vascular regeneration in an ischemia model. These data show a novel mechanism of neovascularization and suggest that low-dose irradiation may be used for therapeutic angiogenesis to augment vasculogenesis in ischemic tissues.

Animals↗