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Nan Zhang

Publications and source records attributed to Nan Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2004

Role of donor-derived monocyte chemoattractant protein-1 in murine islet transplantation.

Monocyte chemoattractant protein-1 (CCL2/MCP-1) is a proinflammatory chemokine produced by several cell types, including pancreatic islets. High levels of donor-derived CCL2 have been associated with poor islet allograft outcome in patients with type 1 diabetes; however, the causal relationship is unknown. The constitutive and inducible expression of chemokines and their receptors by pancreatic islets in vitro were investigated, specifically the role of donor-derived CCL2 in marginal mass murine islet transplantation. The results showed that inflammatory cytokine stimulation of islets induced de novo expression of CCL2, CCL5/RANTES, CXCL9/MIG, and CXCL10/IP-10 and increased expression of CXCL2/macrophage-inflammatory protein-2. CCL2 mRNA and protein were highly expressed within 2 d in cultures. Transplantation of islets with high levels of CCL2 into syngeneic recipients led to a significantly greater influx of CCR2(+) cells and higher expression of monocyte/macrophage-associated inflammatory cytokines compared with low CCL2-donor islets. The level of pretransplantation CCL2 inversely correlated (P < 0.0001) with isograft function. In contrast, in CCR2-/- recipients, this correlation was not present. A direct toxic effect of CCL2 on islets was excluded by assessing cell viability and insulin release in vitro. In conclusion, CCL2 secreted by islets plays an important role in the immediate islet graft function. Strategies to decrease islet-derived CCL2 release may increase the success of islet transplantation.

Animals↗
PubMed2004

Circulating half-life of PEGylated recombinant methioninase holoenzyme is highly dose dependent on cofactor pyridoxal-5'-phosphate.

Recombinant methioninase (rMETase) has been shown to target the elevated methionine (MET) dependence of tumor cells and arrest their growth as well as make tumors more sensitive to standard chemotherapy agents. Polyethylene glycol (PEG)-modified rMETase (PEG-rMETase) has reduced antigenicity compared with unmodified rMETase. However, PEG-rMETase has a limited active circulating half-life due to rapid in vivo dissociation of its cofactor pyridoxal-5'-phosphate (PLP), a surprising finding, because PLP is tightly bound to PEG-rMETase in buffer. The question asked in the current study was on the effect of increasing doses of PLP to extend the circulating half-life of active PEG-rMETase holoenzyme in vivo. rMETase was conjugated with methoxypolyethylene glycol succinimidyl glutarate 5000 (MEGC-PEG). Miniosmotic pumps containing various concentrations of PLP were implanted in BALB-C mice. PLP-infused mice were then injected with a single dose of 4000 or 8000 units/kg PEG-rMETase. Mice infused with 5, 50, 100, 200, and 500 mg/ml PLP-containing miniosmotic pumps increased plasma PLP to 7, 24, 34, 60, and 95 microm, respectively, from the PLP baseline of 0.3 microm. PLP increased the half-life of MEGC-PEG-rMETase holoenzyme in a dose-dependent manner. Pumps containing 500 mg/ml PLP increased the half-life of MEGC-PEG-rMETase holoenzyme 4.5-fold from 1.5 to 7 h. Infused PLP did not extend the half-life of MEGC-PEG-rMETase apoenzyme. With a dose of 4000 units/kg MEGC-PEG-rMETase in the mice infused with 5, 50, 200, and 500 mg/ml PLP, plasma MET was depleted from 50 microm to < or = 5 microm for 8, 24, 72, and 72 h, respectively. Thus, PLP infusion could extend the period of MET depletion by MEGC-PEG-rMETase by approximately 10-fold in a dose-dependent manner. The mice given 8000 units/kg MEGC-PEG-rMETase showed a similar plasma MET depletion time course, indicating that the limiting factor for MEGC-PEG-rMETase-mediated MET depletion in vivo was PLP. The extended time of MET depletion by MEGC-PEG-rMETase was due to the maintenance of active MEGC-PEG-rMETase holoenzyme by infused PLP. The infused PLP either bound to apo-MEGC-PEG-rMETase and/or inhibited dissociation of PLP from holo-PEG-rMETase, thereby maintaining the holoenzyme form of MEGC-PEG-rMETase in vivo. The combination of MEGC-PEG-rMETase treatment with PLP infusion suggests an effective clinical strategy for long-term MET depletion to arrest cancer growth.

Animals↗
PubMed2004

Surgical treatment of portal vein cavernous transformation.

The aim of this study was to explore the treatment of portal cavernous transformation (PVCT). The surgical treatment of 18 patients with PVCT was studied retrospectively. Eight patients underwent mesocaval shunt with artificial grafts, two patients had splenectomy and disconnection, three patients had a central splenorenal shunt, and six patients had a distal splenorenal shunt. There were no deaths or hepatic encephalopathy after operation. Bleeding recurred in two patients (disconnection in one, mesocaval shunt in one). The individualized choice of shunt is ideal for treating PVCT, and the combined procedures of shunt and disconnection are useful. The Rex shunt will be the focus of PVCT surgery in the future.

Adolescent↗
PubMed2004

[Analysis of the results of gamma knife radiosurgery for hemangioblastomas of the brain and the factors related to the tumor recurrence].

OBJECTIVE: To assess the 5-year-result of leksell gamma knife (LGK) in controlling hemangioblastomas of the brain (HB) and to analyze the factors related to tumor recurrence or development of new tumors. METHODS: From November 1993 to September 2001, 35 patients, 28 males and 7 females, aged 36 (16 approximately 61), 18 with multiple tumors and 17 with solitary tumor, the number of tumors being 93 in total, were treated by LGK. Twenty-one patients with HBs were associated with von Hippel-Lindau disease (VHLD). The tumor size ranged 5 approximately 55 mm with a mean size of 13 mm. The mean maximum irradiation dose was 35.6 Gy (20.0 approximately 50.0 Gy) at tumor center and the mean minimum dose was 17.2 Gy (12.0 approximately 24.0 Gy) at tumor periphery. Fisher exact test, independent T test and Wilcoxon rank sum W test were used to analyze the results of LGK on solitary and multiple HBs, the recurrent time of the HBs, and the relation between minimum irradiation dose and tumor control. RESULTS: 35 patients had been followed for 24 - 114 months with a mean value of 66 months. 29 patients were alive and 6 died. Of the 29 patients 21 achieved satisfying tumor control, and 8 patients underwent open surgery because of tumor-associated cysts enlarging or development of new tumors after LGK. 21 patients had improvement or remained stable in neurological status. Of the 8 reopened patients, 2 had deteriorated symptoms and the other 6 remained neurologically stable. Of the 35 patients, 7 developed new tumor during the follow-up period, and 5 had second LGK. Tumor control: Of the 29 cases, solitary or multiple tumors in 23 patients decreased in volume or remained the same, although two developed new tumors. The result of LGK in controlling HBs showed no significant difference between the solitary and multiple HBs (P > 0.05), but the dose of long-term tumor control was significantly higher than that of uncontrolled tumors (W = 98, P < 0.01). The tumor control rate was 94% 1 year after; 85% 2 years after; 82% 3 years after; 79% 4 years after; and 71% 5 years after. For the patients with solitary tumor, the mean time of development of new tumor was 63 months, but for the patients with multiple HBs, the time was 25 months. There was a significant difference between the two groups (t = 3.987, P < 0.001). With margin dose of 18 Gy, histopathology showed that no tumor cell was found and there were coagulation necrosis, hyaline degeneration and fibrosis tissues in the tumor nodule 48 months after LGK. CONCLUSION: LGK is a good choice for small- or medium-sized, solid HB in long term, especially when tumor margin dose is 16 - 20 Gy. Although LGK can treat multiple tumors in one single treatment session, for HB in patients associated with VHLD, LGK faces the problem of tumor recurrence or development of new tumor.

Adolescent↗
PubMed2004

Lipid raft proteomics: analysis of in-solution digest of sodium dodecyl sulfate-solubilized lipid raft proteins by liquid chromatography-matrix-assisted laser desorption/ionization tandem mass spectrometry.

Lipid rafts are glycolipid- and cholesterol-enriched membrane microdomains implicated in membrane signaling and trafficking. The highly hydrophobic nature of lipid raft proteins pose significant problems of solubilization and recovery that hinder analysis by mass spectrometry (MS) and may under-report the composition of lipid rafts. In a previous investigation of the monocyte lipid raft in which proteins were digested with trypsin following polyacrylamide gel electrophoresis we identified 52 proteins. Here we report the development of a sodium dodecyl sulfate (SDS)-aided approach in which proteins are digested in solution and examined by high-performance liquid chromatography-matrix-assisted laser desorption/ionization-tandem mass spectrometry (HPLC-MALDI-MS/MS) using a novel LC-MALDI interface thereby circumventing the need to separate proteins on gels. Using this approach we identified 71 proteins in the lipid raft, 45 of which were not detected using in-gel digestion. Among the new proteins are alpha- and beta-tubulin, tubulinspecific chaperone A, a folding protein involved in tubulin dimer assembly, and KIF13, a microtubule motor protein indicating that proteins involved in microtubule assembly and trafficking are more readily detected using an in-solution approach. To investigate why tubulin was not identified by in-gel digestion, we compared the distribution of alpha-tubulin and the raft marker flotillin-2 in buoyant density gradients before and after separation on SDS-gels. Both proteins were present in the raft fractions, but tubulin was selectively lost following separation on SDS-gels. Assemblies of cytoskeletal proteins with lipid rafts may therefore be resolved using in-solution digestion that would be missed using gel-based approaches.

Biological Transport↗
PubMed2004

Effects of common surfactants on protein digestion and matrix-assisted laser desorption/ionization mass spectrometric analysis of the digested peptides using two-layer sample preparation.

While surfactants are commonly used in preparing protein samples, their presence in a protein sample can potentially affect the enzymatic digestion process and the subsequent analysis of the resulting peptides by mass spectrometry. The extent of the tolerance of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to surfactant interference in peptide analysis is very much dependent on the matrix/sample preparation method. In this work the effects of four commonly used surfactants, namely n-octyl glucoside (OG), Triton X-100 (TX-100), 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) and sodium dodecyl sulfate (SDS), for biological sample preparation on trypsin digestion and MALDI-MS of the resulting digest are examined in detail within the context of using a two-layer method for MALDI matrix/sample preparation. Non-ionic and mild surfactants, such as OG, TX-100 or CHAPS, are found to have no significant effect on trypsin digestion with surfactant concentrations up to 1%. However, TX-100 and CHAPS interfere with the subsequent peptide analysis by MALDI-MS and should be removed prior to peptide analysis. OG is an MS-friendly surfactant and no effect is observed for MALDI peptide analysis. The effect of SDS on trypsin digestion in terms of the number of peptides generated and the overall protein sequence coverage by these peptides is found to be protein dependent. The use of SDS to solubilize hydrophobic membrane proteins, followed by trypsin digestion in the presence of 0.1% SDS, results in a peptide mixture that can be analyzed directly by MALDI-MS. These peptides are shown to provide better sequence coverage compared with those obtained without the use of SDS in the case of bacteriorhodopsin, a very hydrophobic transmembrane protein. This work illustrates that MALDI-MS with the two-layer sample preparation method can be used for direct analysis of protein digests with no or minimum sample cleanup after proteins are digested in a solution containing surfactants.

Animals↗
PubMed2004

CD4+ CD25+ CD62+ T-regulatory cell subset has optimal suppressive and proliferative potential.

CD4+ CD25+ regulatory T cells (Treg) are potent suppressors, and play important roles in autoimmunity and transplantation. Recent reports suggest that CD4+ CD25+ Treg are not a homogeneous cell population, but the differences in phenotype, function, and mechanisms among different subsets are unknown. Here, we demonstrate CD4+ CD25+ Treg cells can be divided into subsets according to cell-surface expression of CD62L. While both subsets express foxp3 and are anergic, the CD62L+ population is more potent on a per cell basis, and proliferates and maintains suppressive function far better than the CD62L- population and unseparated CD4+ CD25+ Treg. The CD62L+ population preferentially migrates to CCL19, MCP-1 and FTY720. Both CD62L+ and CD62L- subsets prevent the development of autoimmune gastritis and colitis induced by CD4+ CD25-CD45RBhigh cells in severe combined immunodeficiency (SCID) mice. Overall, these results suggest CD4+ CD25+ Treg are not a homogenous cell population, but can be divided into at least two subsets according to CD62L expression. The CD62L+ subset is a more potent suppressor than the CD62L- population or unfractionated CD4+ CD25+ Treg cells, can be expanded far more easily in culture, and is more responsive to chemokine-driven migration to secondary lymphoid organs. These properties may have significant implications for the clinical manipulation of the CD4+ CD25+ CD62L+ cells.

Animals↗
PubMed2004

Differential expression of chemokines and chemokine receptors in murine islet allografts: the role of CCR2 and CCR5 signaling pathways.

Chemokines and their receptors play a pivotal role in the initiation and amplification of the immune response. Investigated was their differential expression after syngeneic and allogeneic islet transplantation. During the 7 d after transplantation, the chemokines MCP-1, MCP-2, RANTES, MIG, IP-10, I-TAC, and two CC chemokine receptors CCR2 and CCR5 were highly expressed in allografts when compared with isografts. Disrupting the CCR2 and CCR5 pathways individually resulted in prolongation of the survival time 16.1 +/- 0.4 and 15.8 +/- 0.9 d, respectively, of fully major histocompatibility complex-mismatched islet grafts compared with wild-type controls (11.2 +/- 1.0 d). Blockade of both receptors had no synergistic effect. Rapamycin-treated wild-type recipients rejected their grafts at 17.4 +/- 2.2 d, in contrast to rapamycin-treated CCR2-/- recipients at 38 +/- 8.6 d (P = 0.025). The disruption of the CCR2 and CCR5 signaling, alone or in combination, moderately prolong islet allograft survival. However, the combination of low-dose immunosuppression and targeting of CCR2 greatly augmented islet graft survival.

Animals↗
PubMed2004

TGF-beta induces Foxp3 + T-regulatory cells from CD4 + CD25 - precursors.

CD4 + CD25 + regulatory T cells (Tregs) are potent suppressors, playing important roles in autoimmunity and transplantation tolerance. Understanding the signals necessary for the generation and expansion of Tregs is important for clinical cellular therapy, but only limited progress has been made. Recent reports suggest a role for TGF-beta in the generation of Tregs from CD4 + CD25 - precursors, but the mechanism remains unknown. Here, we demonstrate that TGF-beta2 triggers Foxp3 expression in CD4 + CD25 - precursors, and these Foxp3 + cells act like conventional Tregs. The generation of Foxp3 + Tregs requires stimulation of the T-cell receptor, the IL-2R and the TGF-beta receptor. More importantly, strong costimulation through CD28 prevents Foxp3 expression and suppressive function in an IL-4-dependent manner. Furthermore, TGF-beta-driven Tregs inhibit innate inflammatory responses to syngeneic transplanted pancreatic islets and enhance islet transplant survival. Thus, TGF-beta is a key regulator of the signaling pathways that initiate and maintain Foxp3 expression and suppressive function in CD4 + CD25 - precursors. TGF-beta and signaling through TGF-beta receptor, CD28 costimulation and IL-4 may be key components for the manipulation of Treg. The de novo generation of Foxp3 + cells from CD4 + cells has the potential to be used for treatment of autoimmune diseases and induction of transplant tolerance.

Animals↗
PubMed2004

The roles of centrosome in cancer development.

The accumulation of a series of genetic alterations involving the activation of proto-oncogenes and inactivation of tumor suppressor genes has long been regarded as a major driving force in carcinogenesis. Therefore, cancer is currently considered a genetic disease induced by DNA damage. However, the molecular etiology remains enigmatic. In recent years, the centrosome, together with the embedded centrioles and connecting filaments (or microtubules), has come to be regarded as the "brain" of a cell, being a key in maintaining genetic stability and in coordinating other cellular activities. Abnormalities in the centrosome and/or microtubules may result in unequal chromosome segregation leading to genetic alterations. Therefore, cancer is appropriately interpreted primarily as a "brain illness" of a cell rather than a genetic disease. We provide a brief overview of the latest advances in the understanding of the roles of the centrosome in cancer development, and then we discuss the mechanisms causing centrosome abnormalities and the implications for future research.

Cell Nucleus↗
PubMed2004

Committing embryonic stem cells to early endocrine pancreas in vitro.

A panel of genetic markers was used to assess the in vitro commitment of murine embryonic stem (ES) cells toward the endoderm-derived pancreas and to distinguish insulin-expressing cells of this lineage from other lineages such as neuron, liver, and yolk sac. There are two nonallelic insulin genes in mice. Neuronal cells express only insulin II, whereas the pancreas expresses both insulin I and II. Yolk sac and fetal liver express predominately insulin II, small amounts of insulin I, and no glucagon. We found that ES-derived embryoid bodies cultured in the presence of stage-specific concentrations of monothio-glycerol and 15% fetal calf serum, followed by serum-free conditions, give rise to a population that expresses insulin I, insulin II, pdx-1 (a pancreas marker), and Sox17 (an endoderm marker). Immunohistochemical staining shows intracellular insulin particles, and its de novo production was confirmed by staining for C-peptide. Most, but not all, of the insulin+ or C-peptide+ cells coexpress glucagon, demonstrating a differentiation pathway to pancreas rather than yolk sac or fetal liver. Addition of beta-cell specification and differentiation factors activin beta B, nicotinamide, and exendin-4 to later-stage culture increased insulin-positive cells to 2.73% of the total population, compared with the control culture, which gave rise to less than 1% insulin-staining cells. These findings suggest that stepwise culture manipulations can direct ES cells to become early endocrine pancreas.

Animals↗
PubMed2004

Elevated vascular endothelial growth factor production in islets improves islet graft vascularization.

Successful islet transplantation depends on the infusion of sufficiently large quantities of islets, of which only approximately 30% become stably engrafted. Rapid and adequate revascularization of transplanted islets is important for islet survival and function. Delayed and insufficient revascularization can deprive islets of oxygen and nutrients, resulting in islet cell death and early graft failure. To improve islet revascularization, we delivered human vascular endothelial growth factor (VEGF) cDNA to murine islets, followed by transplantation under the renal capsule in diabetic mice. Diabetic animals receiving a marginal mass of 300 islets that were pretransduced with a VEGF vector exhibited near normoglycemia. In contrast, diabetic mice receiving an equivalent number of islets that were transduced with a control vector remained hyperglycemic. Immunohistochemistry with anti-insulin and anti-CD31 antibodies revealed a relatively higher insulin content and greater degree of microvasculature in the VEGF vector-transduced islet grafts, which correlated with significantly improved blood glucose profiles and enhanced insulin secretion in response to glucose challenge in this group of diabetic recipient mice. These results demonstrate that VEGF production in islets stimulates graft angiogenesis and enhances islet revascularization. This mechanism might be explored as a novel strategy to accelerate islet revascularization and improve long-term survival of functional islet mass posttransplantation.

Adenoviridae↗
PubMed2004

[Induction of differentiation of CD34+ cells in vitro and application in endothelialization of blood vessel prostheses].

OBJECTIVE: To induce differentiation of CD(34)+ cells from varying sources into epithelial cells for potential application of blood vessel prostheses. METHODS: CD(34)+ cells were isolated from canine peripheral blood and bone marrow or human umbilical cord blood by an immune magnetic cell sorting system. The isolated CD(34)+ cells were induced to differentiate into endothelial cells in a liquid culture with VEGF. Endothelial cells were evaluated by immunocytochemistry and transmission electron microscopy. CD(34)+ cells were seeded on PTFE prostheses, which were harvested and observed by electron microscopy. RESULTS: The average isolated CD(34)+ cells from peripheral blood, bone marrow and umbilical cord blood were (26.30+/-2.42)%,(41.84 +/-3.65)%and (74.62+/-4.46)%, respectively. The number of CD(34)+ cells increased with the culture duration and reached to the highest level at the 14th d. Immunostaining showed positive signal for CD31 in endothelial cells and positive for factor VIII in cell culture. Transmission electron microscopy found Weibel-Palade bodies in the cytoplasm. Scanning electron microscopy demonstrated a single- layer of flat cells in the innermost layer of PTFE prostheses, and the cells were not of tropism. CONCLUSION: CD(34)+ cells isolated from peripheral blood, bone marrow and umbilical cord blood can be induced into endothelial cells; bone marrow and umbilical cord blood can be used as the sources of seeding cells for endothelialization of prostheses.

Antigens, CD34↗
PubMed2004

[Study on the reperfusion rate of acute myocardial infarction affected by inspiring nitric oxide and resolving thrombus intravenously before admission].

OBJECTIVE: To observe the reperfusion rate of acute myocardial infarction (AMI) affected by inspiring nitric oxide (NO) and resolving thrombus through veins. METHODS: Sixty cases with AMI were randomly divided into test group (n=30) and control groups (n=30). Patients in test group were cured with NO (20+/-1)mg/L inspiration for 30 minutes at once before admission and urokinase (150x10(4) U) adding 0.9% sodium chloride intravenously injected within 30 minutes, while patients in control were treated with urokinase as the same method of the test group. RESULTS: The reperfusion and non-reperfusion patients were 25 and 5 cases in test group, and they were 19 and 11 cases in control group. The reperfusion rate of AMI in test group was significantly higher than that in control group 83.3% vs. 63.3% (P<0.05). No peak periods of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) appeared in test group, and the difference was significant compared to the control group (P<0.05). CONCLUSION: NO inspiration before urokinase is an effective method to treat AMI and advance the reperfusion rate.

Aged↗
PubMed2004

Identification of 4-anilino-3-quinolinecarbonitrile inhibitors of mitogen-activated protein/extracellular signal-regulated kinase 1 kinase.

A high-throughput screen for Ras-mitogen-activated protein kinase (MAPK) signaling inhibitors identified two series (class 1 and 2) of substituted 4-anilino-3-quinolinecarbonitriles as potent (IC(50)s <10 nmol/L) mitogen-activated protein/extracellular signal-regulated kinase 1 (MEK1) kinase inhibitors. These compounds had cyanoquinoline cores, but differed in their respective aniline groups [1a, 1b: 4-phenoxyphenylaniline; 2a, 2b: 3-chloro-4-(1-methylimidazol-2-sulfanyl)aniline]. These compounds were competitive inhibitors of ATP binding by MEK1 kinase, and they had minimal or no effect on Raf, epidermal growth factor receptor (EGFR), Akt, cyclin-dependent kinase 4 (CDK4), or MK2 kinases at concentrations >100-fold higher than those that inhibited MEK1 kinase. Both class 1 and 2 compounds inhibited in vitro growth of human tumor cell lines. A class 2 compound (2b) was the most potent inhibitor of human tumor cell growth in vitro, and this effect was linked to distinct suppression of MAPK phosphorylation in cells. Compound 2b did not affect phosphorylation status of other kinases, such as EGFR, Akt, and stress-activated protein (SAP)/c-jun-NH kinase (Jnk); nor did it affect overall tyrosine phosphorylation level in cells. However, compound 2b did inhibit MEK1 phosphorylation in cells. Inhibition of MEK1 phosphorylation by 2b was not due to a major effect on Raf kinase activity, because enzyme assays showed minimal Raf kinase inhibition. We believe compound 2b inhibits kinase activity upstream of Raf, and thereby affects MEK1 phosphorylation in cells. Even with the dual effect of 2b on MEK and MAPK phosphorylation, this compound was well tolerated and significantly inhibited growth of the human colon tumor cell line LoVo (at 50 and 100 mg/kg BID, i.p.) in a nude mouse xenograft model.

Adenosine Triphosphate↗
PubMed2003

In vivo efficacy of recombinant methioninase is enhanced by the combination of polyethylene glycol conjugation and pyridoxal 5'-phosphate supplementation.

Recombinant methioninase (rMETase) is an enzyme active in preclinical mouse models of human cancer. The efficacy of rMETase is due to depletion of plasma methionine, an amino acid for which tumors generally have an abnormally high methionine requirement. Furthermore, transient methionine depletion results in a markedly increased sensitivity of the tumors to several chemotherapeutic agents. This study characterized methods to prolong the half-life of rMETase to extend the in vivo period of depletion of plasma and tumor methionine. In the present study, rMETase was coupled to methoxypolyethylene glycol succinimidyl glutarate-5000 in order to prolong the half-life of rMETase and thus extend the in vivo period of depletion of plasma and tumor methionine. Matrix-assisted laser desorption ionization mass spectrometry indicated that one sub-unit of rMETase was modified by approximately 4, 6 and 8 PEG molecules when rMETase was PEGylated at molar ratios of PEG/rMETase of 30/1, 60/1, and 120/1, respectively. PEG-rMETase (120/1) had a serum half-life increase of 20-fold, and methionine depletion time increased 12-fold compared to unmodified rMETase. The increase in in vivo half-life depended on the extent of PEGylation of rMETase. In addition, a remarkable prolongation of in vivo activity and effective methionine depletion by the PEG-rMETase was achieved by the simultaneous administration of pyridoxal 5'-phosphate. PEGylation also reduced the immunogenicity of rMETase. The extent of reduction in immunogenicity depended on the number of residues PEGylated. PEG-rMETase 30/1 had a 10-fold decrease in IgG titer while PEG-rMETase 120/1 had a 10(4)-fold decreased titer compared to naked rMETase. Thus, the molecular modification of PEGylation confers critical new properties to rMETase for development as a cancer therapeutic.

Animals↗