Cytopenia: a report of haplo-cord transplantation in twin brothers caused by a novel germline GATA1 mutation and family survey.

Cytopenia due to the abnormal regulation of GATA1 could manifest as varying degrees of thrombocytopenia and/or anemia and more severely in male children than in female children. Here, we describe the case of pancytopenic and transfusion-dependent twin brothers at our center whose bone marrow puncture revealed low bone marrow hyperplasia. Whole-exome sequencing revealed that the twins had a new germline GATA1 mutation (nm_002049: exon 3:c.515 T >C:p.F172S), which confirmed the diagnosis of GATA1 mutation-related pancytopenia. The mutation was inherited from their mother, who was heterozygous for the mutation. Sanger sequencing verified the pathogenicity of the mutation. Further family morbidity survey confirmed that GATA1 mutation-related pancytopenia is an X-linked recessive genetic disorder. We developed haploid hematopoietic stem cell transplantation programs for twins, with the father as the only donor, and finally, the hematopoietic reconstruction was successful. Although they experienced acute graft-versus-host disease, hemorrhagic cystitis, and a viral infection in the early stage, no abnormal manifestations or transplant-related complications were observed 3 months after transplantation. Through hematopoietic stem cell transplantation technology for one donor and two receptors, we eventually cured the twins. The p.F172S variant in the new germline GATA1 mutation may play an essential role in the pathogenesis of GATA1 mutation-related cytopenia.

Residential Environment Pollution Monitoring System Based on Cloud Computing and Internet of Things.

In order to solve the problems of single monitoring factor, weak comprehensive analysis ability, and poor real time performance in traditional environmental monitoring systems, a research method of residential environment pollution monitoring system based on cloud computing and Internet of Things is proposed. The method mainly includes two parts: an environmental monitoring terminal and an environmental pollution monitoring and management platform. Through the Wi-Fi module, the data is sent to the environmental pollution monitoring and management platform in real time. The environmental monitoring management platform is mainly composed of environmental pollution monitoring server, web server, and mobile terminal. The results are as follows. The data measured by the system is close to the data measured by the instrument, and the overall error is small. The measurement error of harmful gases is about 6%. PM 2.5 is about 6.5%. Noise is about 1%. The average time for sensor data update is 0.762 s. The average alarm response time is 2 s. The average data transfer time is 2 s. Practice has proved that the environmental pollution monitoring and alarm system operates stably and can realize real-time collection and transmission of data such as noise, PM 2.5, harmful gas concentration, illumination, GPS, and video images, providing a reliable guarantee for timely environmental pollution control.

Human Health Risk Prediction Method of Regional Atmospheric Environmental Pollution Sources Based on PMF and PCA Analysis under Artificial Intelligence Cloud Model.

In order to solve the problem that atmospheric particulate matter has become the primary pollutant with serious harm and complex sources in recent years, this paper proposes an accurate identification method of pollution sources based on a receptor model to obtain the contribution rate of each pollution source category. This method takes the 75-day measured environmental receptor data of an area under the artificial intelligence cloud model as the basic data, uses the normrnd () function to expand the receptor data, and uses the positive definite matrix factor analysis (PMF) and principal component analysis (PCA) models to verify the rationality of the data expansion. The results are as follows: the number of extended simulated receptor component spectra has a certain effect on the PCA analysis results, but the effect is smaller than the extended range. All relative errors are less than 14%, and the relative error is the smallest when the six simulated receptor component spectra are expanded, that is, the PCA analysis results of the expanded data are most consistent with the measured data; the number of expanded simulated receptor component spectra has a certain influence on the PMF analysis results. But the relative error is less than 40%. When extending the spectrum of six simulated receptor components, the relative error is the smallest, that is, the PMF analysis results of the extended data are most consistent with the measured data. It is proven that this method provides a more direct basis for the targeted treatment of pollution sources that are more harmful to human health.

Synthesis of Site-Specific Dye-Labeled Polymer via Atom Transfer Radical Polymerization (ATRP) for Quantitative Characterization of the Well-Defined Interchain Distance.

Novel difunctional initiators that incorporate Förster/fluorescence resonance energy transfer (FRET) pairs are generated to carry out atom transfer radical polymerization of styrene, methyl methacrylate, and n-butyl methacrylate monomers by an efficient manner. Based on the chemical structures of the initiators, the locations of the fluorophore moiety are dictated to be in the center of the chain with accurately quantified chain functionality (>90% labeling ratio). The site-specific integration of FRET dyes into separate polymer chain centers allows for characterization of the well-defined interchain distance quantitatively based on the response between these fluorescent probes. The reliability of this technique is verified in bulk state, which is in well agreement with the theoretical ones. This well-defined FRET system is expected to be a promising candidate to provide a distinct physical image at a microscopic level regarding scaling chain dimension, chain interpenetration, and polymer compatibility.

Flow-Through Electroporation of HL-60 White Blood Cell Suspensions using Nanoporous Membrane Electrodes.

A flow-through electroporation system, based on a novel nanoporous membrane/electrode design, for the delivery of cell wall-impermeant molecules into model leukocytes, HL-60 promyelocytes, was demonstrated. The ability to apply low voltages to cell populations, with nm-scale concentrated electric field in a periodic array, contributes to high cell viability. With applied biases of 1-4V, delivery of target molecules was achieved with 90% viability and up to 65% transfection efficiency. More importantly, the system allowed electrophoretic pumping of molecules from a microscale reservoir across the membrane/electrode system into a microfluidic flow channel for transfection of cells, a design that can reduce reagent amount by eightfold compared to current strategies. The flow-through system, which forces intimate membrane/electrode contact by using a 10µm channel height, can be easily scaled-up by adjusting the microfluidic channel geometry and/or the applied voltage pulse frequency to control cell residence times at the cell membrane/electrode interface. The demonstrated system shows promise in clinical applications where low-cost, high cell viability and high volume transfection methods are needed without the risk of viral vectors. In particular genetic modification of freely mobile white blood cells to either target disease cells or to express desired protein/enzyme biomolecules is an important target platform enabled by this device system.

Dynamic Electrochemical Membranes for Continuous Affinity Protein Separation.

A membrane system with nm-scale thick electrodes is able to selectively bind genetically modified proteins and pump them across the membrane with sequential voltage pulses. The electrodes are located at the first 20nm of pore entrances to specifically capture targeted proteins and block non-specific protein transport through the pores during the binding cycle. During the release cycle, concentration of imidazole is controlled to keep the pore blocked while releasing proteins at the bottom edge of the electrode. A separation factor for GFP:BSA of 16 was achieved with observed GFP electrophoretic mobility of 2.54×10-6cm2v-1S-1. This non-optimized system with a membrane area of 0.75 cm2 has the same throughput as 1ml of commercially available chromatography columns showing viability as a continuous process. This system will enable continuous separation of expressed proteins directly from fermentation broths dramatically simplifying the separation process as well as reducing biopharmaceutical production costs.

Enhanced penetration into 3D cell culture using two and three layered gold nanoparticles.

Nano-scale particles sized 10-400 nm administered systemically preferentially extravasate from tumor vasculature due to the enhanced permeability and retention effect. Therapeutic success remains elusive, however, because of inhomogeneous particle distribution within tumor tissue. Insufficient tumor vascularization limits particle transport and also results in avascular hypoxic regions with non-proliferating cells, which can regenerate tissue after nanoparticle-delivered cytotoxicity or thermal ablation. Nanoparticle surface modifications provide for increasing tumor targeting and uptake while decreasing immunogenicity and toxicity. Herein, we created novel two layer gold-nanoshell particles coated with alkanethiol and phosphatidylcholine, and three layer nanoshells additionally coated with high-density-lipoprotein. We hypothesize that these particles have enhanced penetration into 3-dimensional cell cultures modeling avascular tissue when compared to standard poly(ethylene glycol) (PEG)-coated nanoshells. Particle uptake and distribution in liver, lung, and pancreatic tumor cell cultures were evaluated using silver-enhancement staining and hyperspectral imaging with dark field microscopy. Two layer nanoshells exhibited significantly higher uptake compared to PEGylated nanoshells. This multilayer formulation may help overcome transport barriers presented by tumor vasculature, and could be further investigated in vivo as a platform for targeted cancer therapies.

Enhanced drug delivery via hyperthermal membrane disruption using targeted gold nanoparticles with PEGylated Protein-G as a cofactor.

Gold nanoparticles (GNPs) with near infrared (NIR) plasmon resonance have been promisingly used in photothermal cancer therapy as a less invasive treatment. Recombinant Protein-G (ProG) was PEGylated to act as a cofactor to immobilize immunoglobulins (IgGs) on GNPs by the Fc region, resulting in optimal orientation of IgGs for efficient cancer targeting. In-vitro studies showed that HER-2 overexpressing breast cancer cells, SK-BR-3, were efficiently targeted and ablated at a laser power of 900 J/cm(2) (5 W/cm(2) for 3 min). However, as a means of enhancing treatment efficacy by increasing cellular sensitivity to chemotherapeutic agents, we showed that GNP exposure to lower power laser resulted in small disruptions of cell membrane due to localized hyperthermia. This did not lead to cell death but provided a mechanism for killing cancer cells by providing enhanced uptake of drug molecules thus leading to a new avenue for hyperthermia-anticancer drug combined cancer therapeutics. FROM THE CLINICAL EDITOR: PEGylated recombinant Protein-G was used as a cofactor to optimize the orientation of IgGs providing "target seeking" properties to gold nanoparticles used in photothermal cancer therapy. The system demonstrated excellent properties in cancer therapy, with the hope and expectation of future clinical translation.

Targeted cancer therapy by immunoconjugated gold-gold sulfide nanoparticles using Protein G as a cofactor.

Gold-gold sulfide nanoparticles (GGS-NPs) fabricated from chloroauric acid and sodium thiosulfate show unique near infrared (NIR) absorption that renders them as a promising candidate for photothermal cancer therapy. To improve targeting efficiency, we developed a versatile method to allow ordered immunoconjugation of antibodies on the surfaces of these nanoparticles via a PEGylated recombinant Protein G (ProG). The PEGylated ProG was prepared with orthopyridyldisulfide-polyethylene glycol-succinimidyl valerate, average MW 2000 (OPSS-PEG-SVA), to first allow the self-assembly of ProG on the nanoparticles, subsequently antibodies were added to this construct to enable active targeting. The bioconjugated GGS-NPs were characterized by TEM, NIR-spectra, dynamic light scattering and modified immunoassay. In in vitro studies, the ProG-conjugated GGS-NPs with bound mouse anti c-erbB-2 (HER-2) immunoglobulin G (IgG) successfully targeted the HER-2 overexpressing breast cancer cell, SK-BR-3. Extensive cell death was observed for the targeted SK-BR-3 line at a low laser power of 540 J (3 W cm(-2) for 3 min) while the control breast cancer cell (low expressing HER-2), HTB-22 survived. Using PEGylated ProG as a cofactor for immobilization of antibodies offers a promising strategy to functionalize various IgGs on nanoparticles for engineering their biomedical applications in cancer therapeutics.

Electrophoretic transport of biomolecules through carbon nanotube membranes.

Electrophoretic transport of proteins across electrochemically oxidized multi-walled carbon nanotube (MWCNT) membranes has been investigated. A small charged protein, lysozyme, was successfully pumped across MWCNT membranes by an electric field while rejecting larger bovine serum albumin (BSA). Transport of lysozome was reduced by a factor of about 30 in comparison to bulk mobility and consistent with the prediction for hindered transport. Mobilities between 0.33 and 1.4 × 10(-9) m(2) V(-1) s(-1) were observed and are approximately 10-fold faster than comparable ordered nanoporous membranes and consistent with continuum models. For mixtures of BSA and lysozyme, complete rejection of BSA is seen with electrophoretic separations.

[Effects of compound danshen dripping pill on the structure and functions of sternohyoid muscle in metabolic syndrome rats].

OBJECTIVE: To study the effects of Compound Danshen Dripping Pill (CDDP) on the structure and functions of sternohyoid muscle in metabolic syndrome (MS) rats, and to study whether it has therapeutic effects on obstructive sleep apnea-hypopnea syndrome (OSAHS). METHODS: Twenty-one healthy male SD rats were randomly divided into three groups, i.e., the normal control group (n = 6), the MS group (n = 8), and the CDDP group (n = 7). Rats in the normal control group were routinely fed. High lipid forage was given to rats in the rest two groups. Nine weeks later, CDDP (at the dose of 375 mg/kg) was additionally given to rats in the CDDP group by gastrogavage, and then rats in the CDDP group and the MS group were fed with the same high lipid forage for 12 successive weeks. The content of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) in the sternohyoid muscle were detected in the three groups. The capillary density, capillary-to-fiber ratio (C/F), the section area of type I muscle fiber were detected using myosin-ATPase histochemical assay. The contractile changes of isometric stemohyoid muscles were determined under electric stimulation by different frequencies. RESULTS: The contents of MDA were obviously lower in the CDDP group than in the MS group, while the activities of SOD, the capillary density, C/F, the section area of type I muscle fiber, the tension of stemohyoid muscle at 10 -60 Hz, and the 1-5 min tension percentages of the stemohyoid muscle were higher in the CDDP group than in the MS group (P < 0.05, P < 0.01). CONCLUSION: CDDP could improve oxidative stress induced intramuscularly microcirculation disturbance and changes of muscular fiber structures of the upper airway muscles, and elevate their contractile functions, thus possibly contributing to favorable effects on OSAHS.

[Effects of taurine on alterations in structure and function of sternohyoid muscle in metabolic syndrome rats].

OBJECTIVE: To investigate the alterations in structure and function of sternohyoid muscle of metabolic syndrome (MS) rats effects and the effects of taurine thereupon contractile properties. METHODS: Twenty-one healthy male SD rats were randomly assigned to three groups: control group (Group A, n=6) fed with normal food, MS group (Group B, n=8) fed with high-lipid forage for 9 weeks to induce MS and then fed with the same high-lipid forage for 12 weeks in addition, and taurine group (Group C, n=7), fed with high-lipid forage for 20 weeks and given gastric perfusion of taurine 50 mg x d(-1) x kg(-1) since the tenth week for 12 weeks. Venous blood samples were collected to undergo biochemical examination of plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and glucose (Glu). Radioimmunoassay was used to detect the plasma insulin. The sternohyoid muscles were collected. Muscle tissue homogenate was made. The superoxide dismutase (SOD) and malondialdehy (MDA) levels were measured. Myosin-ATPase histochemistry was used to assay the size and capillary density of the isolated sternohyoid muscles. Isometric contractile properties were determined by electrostimulating the strips of isolated sternohyoid muscles at different frequencies (from 10 Hz to 100 Hz) to observe the changes of the sternohyoid contractile properties in different conditions. RESULTS: (1) The levels of TG, LDL, Glu, PGI, and MDA of Group B were significantly higher than those of Groups A and C, while the HDL level of Group B was significantly lower than that of Group A (P < 0.01). The OD level of Group B was significantly lower than those of Groups A and C. (2) The capillary density, capillary-to-fiber ratio (C/F), and cross-sectional area of type I fiber in sternohyoid muscles of Group B were (140 +/- 5)/ nm2, 0.90 +/- 0.11, and (6119 +/- 165) microm2 respectively, all significantly higher than those of Group A [(278 +/- 17)/mm2, 1.43 +/- 0.05, and (9371 +/- 68) microm2 respectively, all P < 0.01] and Group C [(269 +/- 10)/mm2, 1.40 +/- 0.07, and (9007 +/- 136) microm2 respectively, all P < 0.01]. (3) The tensions of sternohyoid muscle of Group B at the frequencies from 10 Hz to 60 Hz were (29 +/- 6) g/cm2, (34 +/- 7) g/ cm2, (41 +/- 6)g/cm2, (47 +/- 6)g/cm2, (53 +/- 7)g/cm2, and (59 +/- 20)g/cm2 respectively, all significantly lower than those of Group A group[(40 +/- 3)g/cm2, (52 +/- 13)g/cm2, (60 +/- 17) g/cm2, (74 +/- 32) g/cm2, (80 +/- 29)g/cm2, and (96 +/- 24)g/cm2 respectively, all P < 0.05] and Group C [(43 +/- 26)g/cm2, (48 +/- 6)g/cm2,(55 +/- 9)g/cm2, (67 +/- 14)g/cm2, (75 +/- 15)g/cm2, and (80 +/- 15)g/cm2 respectively, all P < 0.05]. (4) In fatigue test, the tension percentages of sternohyoid muscle at the time intervals of 1 min, 2 min, 3 min, 4 min, and 5 min of Group B were (80.5 +/- 8.0)%, (64.1 +/- 1.2)%, (59.1 +/- 1.1)%, (56.4 +/- 10.9)%, and (53.5 +/- 9.1)% respectively, all significantly lower than those of Group A [(87.7 +/- 3.5)%, (78.5 +/- 1.5)%, (76.0 +/- 1.2)%, (72.3 +/- 15.0)%, and (68.7 +/- 17.2)% respectively, all P < 0.05] and Group C group [(87.4 +/- 2.4)%, (77.9 +/- 5.5)%, (73.6 +/- 1.1)%, (71.3 +/- 8.7)%, and (68.0 +/- 6.7) respectively, all P < 0.05]. CONCLUSION: With the development of MS, the capillary density, C/F, cross-sectional area of type I fiber of upper airway muscles decrease, in part via oxidative stress, which leads to reduction of the contractile function of upper airway muscles, thus contributing to the onset of obstructive sleep apnea-hypopnea syndrome.

Purification of equine IgG using membrane based enhanced hybrid bioseparation technique: a potential method for manufacturing hyperimmune antibody.

Hyperimmune equine IgG is widely used as antivenom and anti-rabies agents. This article discusses a membrane based enhanced hybrid bioseparation technique for efficient and scalable purification of equine immunoglobulin G (IgG) from horse serum. This technique is an improved version of a standard hybrid bioseparation technique developed within our group earlier for fractionation of human plasma proteins (Ghosh. 2004. J Membr Sci 237: 109-117). In the presence of a high antichaotropic salt concentration, equine IgG is selectively and reversibly captured within a stirred cell membrane module from horse serum, partly due to precipitation and microfiltration, and partly due to hydrophobic interaction based membrane adsorption, while the impurities are washed out from the device. The reversibly sequestered IgG is then released by lowering the salt concentration which favor both dissolution of the precipitated IgG and desorption of the membrane bound IgG. The enhanced hybrid bioseparation technique improves the IgG recovery from the membrane module by switching from a stirring to non-stirring mode during the IgG release phase. It also reduces membrane fouling by an appropriate pH switch. The effects of operating conditions on equine IgG capture were first systematically studied. The enhanced hybrid bioseparation technique was followed by an ultrafiltration step to remove ammonium sulfate and low molecular weight impurities. The equine IgG purity obtained under optimized conditions was 88% and its recovery was over 90%, both being significantly higher than corresponding values obtained using currently used purification techniques.

[Analysis of the relationship between pathology and recurrence of primary lacrimal epithelial tumors].

OBJECTIVE: To analyze the relationship between pathology and recurrence of primary lacrimal epithelial tumors. METHODS: 128 cases of primary lacrimal epithelial tumors including benign mixed tumor (74 cases, 57.8%), adenoid cystic carcinoma (22 cases, 17.2%) and malignant mixed tumor (18 cases, 14.1%) were subjected in the study. Pathological features were analyzed and compared with their recurrence. RESULTS: The recurrent rate of benign mixed tumor, adenoid cystic carcinoma and malignant mixed tumor was 23.0%, 18.2% and 27.8%, respectively. The recurrence of benign mixed tumor was statistically related to pathological classification and encapsulates. CONCLUSIONS: Primary lacrimal epithelial tumors show variant types and high recurrent rate. The pathological features were decisive in diagnosis, selection of treatment and the time of follow-up.

A rapid HPLC method for the measurement of ultra-low plasma methionine concentrations applicable to methionine depletion therapy.

A rapid, sensitive and specific high-performance liquid chromatographic (HPLC) method for the separation and quantification of L-methionine in plasma has been developed. After derivatization of plasma amino acids with o-phthalaldehyde (OPA), a 50 microl sample was loaded on a reversed-phase Supelcosil LC-18-DB column (particle size 5 microm, 25 cm x 4.6 mm, 120A pores). A customized gradient program using tetrahydrofuran/methanol/0.1 M sodium acetate, pH 7.0, v/v/v=5/95/900 and methanol was used with detection by fluorescence. The elution time was 15 minutes, a 3-fold improvement over existing methods. The linearity was 1-100 microM. The limit of detection was 0.5 micromol/L, a 10-fold improvement over existing methods. The inter-assay CVs were 2-5%, and the intra-assays CVs were 4-8%. The sensitivity and rapidity of this HPLC method is particularly applicable to determine the efficacy of methionine depletion therapy of cancer.

PEGylation confers greatly extended half-life and attenuated immunogenicity to recombinant methioninase in primates.

Methionine depletion by recombinant methioninase (rMETase) has been demonstrated previously to be highly effective in tumor-bearing mouse models. However, the therapeutic potential of rMETase has been limited by its short plasma half-life and immunologic effects, including high antibody production in mice and monkeys and anaphylactic reactions in monkeys. To overcome these limits of rMETase, the enzyme has been coupled to methoxypolyethylene glycol succinimidyl glutarate (MEGC-PEG-5000). In this study, we evaluated the pharmacokinetics, antigenicity and toxicity of MEGC-PEG-rMETase in Macaca fascicularis monkeys using an escalating-dose strategy. Dose ranging studies at 1,000, 4,000, and 8,000 units/kg i.v. determined that a single dose of 4,000 units/kg was sufficient to reduce plasma methionine to <5 micromol/L for 12 hours. Pharmacokinetic analysis with the single 4,000 units/kg dose showed that MEGC-PEG-rMETase holoenzyme activity was eliminated with a biological half-life of 1.3 hours, and the MEGC-PEG-rMETase apoenzyme was eliminated with a biological half-life of 90 hours, an approximately 36-fold increase compared with non-PEGylated rMETase. A single dose at 2,000 units/kg of MEGC-PEG-rMETase resulted in an apoenzyme half-life of 143 hours. A seven-day i.v. administration of 4,000 units/kg every 12 hours resulted in a steady-state depletion of plasma methionine to <5 micromol/L. The only manifest toxicity was decreased food intake and slight weight loss. Red cell values and hemoglobin declined transiently during treatment but recovered after cessation of treatment. Subsequent challenges on days 29, 50 and, 71 did not result in any immunologic reactions. This result is in contrast to non-PEGylated rMETase, which elicited anaphylactic reactions in monkeys. Anti-MEGC-PEG-rMETase antibodies (at 10(-2)) were found on day 29, and these increased to 10(-3) to 10(4) on day 71, 100 to 1,000-fold less than antibodies elicited by naked rMETase. Although anti-MEGC-PEG-rMETase antibodies were produced, no neutralizing antibody was identified, and each challenge dose was effective in depleting plasma methionine levels. The results of the present study demonstrate that PEGylation greatly prolongs serum half-life of the rMETase apoenzyme and eliminated anaphylactic reactions. The results indicate a profile with respect to serum half-life, toxicity, and antigenicity that suggest clinical potential of MEGC-PEG-rMETase.

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.

Protein carboxyl amidation increases the potential extent of protein polyethylene glycol conjugation.

Chemical coupling of polyethylene glycol (PEG) to therapeutic proteins reduces their immunogenicity and prolongs their circulating half-life. The limitation of this approach is the number and distribution of sites on proteins available for PEGylation (the N terminus and the -amino group of lysines). To increase the extent of PEGylation, we have developed a method to increase the number of PEGylation sites in a model protein, recombinant methionine alpha,gamma-lyase (recombinant methioninase; rMETase), an enzyme cancer therapeutic cloned from Pseudomonas putida. rMETase was first PEGylated with methoxypolyethylene glycol succinimidyl glutarate-5000 with a molar ratio of PEG:rMETase of 15:1. The carboxyl groups of the initially PEGylated protein were then conjugated with diaminobutane, resulting in carboxyl amidation. This reaction was catalyzed by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, a water-soluble carbodiimide. The steric hindrance provided by the PEG chains already coupled to the protein prevented cross-linking between rMETase molecules during the carboxyl amidation reaction. The carboxyl-amidated PEGylated rMETase was hyper-PEGylated at a molar ratio of PEG to PEG-rMETase of 60:1. Biochemical analysis indicated that 13 PEG chains were coupled to each subunit of rMETase after hyper-PEGylation compared with 6-8 PEG chains attached to the non-carboxyl-amidated PEG-rMETase. Approximately 15-20% of the non-PEGylated rMETase activity was retained in the hyper-PEGylated molecule. Immunogenicity of the hyper-PEG-rMETase was significantly reduced relative to PEG-rMETase and rMETase. Initial results suggest that hyper-PEGylation may become a new strategy for PEGylation of protein biologics.