Endostatin sensitizes p53-deficient non-small-cell lung cancer to genotoxic chemotherapy by targeting DNA-dependent protein kinase catalytic subunit.

Endostatin was discovered as an endogenous angiogenesis inhibitor with broad-spectrum antitumour activities. Although clinical efficacy was observed when endostatin was combined with standard chemotherapy for non-small cell lung cancer (NSCLC), as well as other cancer types, the specific mechanisms underlying the benefit of endostatin are not completely understood. Extensive investigations suggest that endostatin is a multifunctional protein possessing more than anti-angiogenic activity. Here, we found that endostatin exerts a direct chemosensitizing effect on p53-deficient tumour cells. Concomitant treatment with endostatin and genotoxic drugs resulted in therapeutic synergy in both cellular and animal models of p53-deficient NSCLC. Mechanistically, endostatin specifically interacts with DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in tumour cells and suppresses its DNA repair activity. Using isogenic NSCLC cells with different p53 statuses, we discovered that p53-deficient tumour cells show chemoresistance to genotoxic drugs, creating a synthetic dependence on DNA-PKcs-mediated DNA repair. In this setting, endostatin exerted inhibitory effects on DNA-PKcs activity, leading to accumulation of DNA lesions and promotion of the therapeutic effect of genotoxic chemotherapy. In contrast, p53-proficient tumour cells were more sensitive to genotoxic drugs so that DNA-PKcs could be cleaved by drug-activated caspase-3, making DNA-PKcs inhibition less effective during this ongoing apoptotic process. Therefore, our data demonstrate a novel mechanism for endostatin as a DNA-PKcs suppressor, and indicate that combination therapy of endostatin with genotoxic drugs could be a promising treatment strategy for cancer patients with p53-deficient tumours. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Production of a therapeutic protein by fusing it with two fragments of the carboxyl-terminal peptide of human chorionic gonadotropin ß-subunit in Pichia pastoris.

OBJECTIVE: To produce a therapeutic protein (endostatin) by fusion with two fragments of the carboxyl-terminal peptide (CTP) of the human chorionic gonadotropin ß-subunit in Pichia pastoris. RESULTS: Two CTP sequences were fused to the C-terminal of human endostatin, and the fusion protein (endo-CTP) was expressed by P. pastoris. Endo-CTP inhibited proliferation of endothelial cells with an IC50 of 7 µg ml(-1), and 30 % of cells were annexin V-positive after treatment with 20 µg endo-CTP ml(-1) for 48 h. Migration of endothelial cells was inhibited by endo-CTP in a concentration-dependent manner. The half-life of endo-CTP in Sprague-Dawley rats was much longer than that of its commercial counterpart (Endostar). CONCLUSION: A long-acting endostatin can be produced using CTP technology.

Pharmacokinetics of PEGylated recombinant human endostatin (M2ES) in rats.

AIM: M2ES is PEGylated recombinant human endostatin. In this study we investigated the pharmacokinetics, tissue distribution, and excretion of M2ES in rats. METHODS: (125)I-radiolabeled M2ES was administered to rats by intravenous bolus injection at 3 mg/kg. The pharmacokinetics, tissue distribution and excretion of M2ES were investigated using the trichloroacetic acid (TCA) precipitation method. RESULTS: The serum M2ES concentration-time curve after a single intravenous dose of 3 mg/kg in rats was fitted with a non-compartment model. The pharmacokinetic parameters were evaluated as follows: Cmax=28.3 µg·equ/mL, t1/2=71.5 h, AUC(0-∞)=174.6 µg·equ·h/mL, Cl=17.2 mL·h(-1)·kg(-1), MRT=57.6 h, and Vss=989.8 mL/kg for the total radioactivity; Cmax=30.3 µg·equ/mL, t1/2=60.1 h, AUC(0-∞)=146.2 µg·equ·h/mL, Cl=20.6 mL·h(-1)·kg(-1), MRT=47.4 h, and Vss=974.6 mL/kg for the TCA precipitate radioactivity. M2ES was rapidly and widely distributed in various tissues and showed substantial deposition in kidney, adrenal gland, lung, spleen, bladder and liver. The radioactivity recovered in the urine and feces by 432 h post-dose was 71.3% and 8.3%, respectively. Only 0.98% of radioactivity was excreted in the bile by 24 h post-dose. CONCLUSION: PEG modification substantially prolongs the circulation time of recombinant human endostatin and effectively improves its pharmacokinetic behavior. M2ES is extensively distributed in most tissues of rats, including kidney, adrenal gland, lung, spleen, bladder and liver. Urinary excretion was the major elimination route for M2ES.

Surface engineered dendrimers as antiangiogenic agent and carrier for anticancer drug: dual attack on cancer.

The present research work describes the formulation of arginine conjugated 3.0G Poly(propylene) imine (PPI) dendrimers, mimicking the surface structure of an endogenous angiogenesis-inhibitor endostatin; for tumor specific delivery of a model anticancer drug, doxorubicin hydrochloride (Dox). Synthesis of PPI dendrimers and conjugation of arginine to surface groups was confirmed by FTIR, NMR, TEM and mass spectrometry. Drug was loaded by equilibrium dialysis method and developed formulation was evaluated for entrapment efficiency, hemolytic toxicity, in vitro drug release, stability, anti-angiogenic activity via in vivo chick embryo chorioallantoic membrane (CAM) assay, and anticancer activity and cell uptake using MCF-7 cancer cell lines. The system exhibited the initial rapid release followed by sustained release of Dox with significant antiangiogenic activity in the CAM assay. Further, the arginine conjugated dendrimers was found to inhibit growth of cancer cells in ex vivo studies with MCF-7 cell lines. Cell uptake studies suggested that in comparison to free drug the formulation was preferably taken up by the tumor cells. Thus the two pronged attack on cancerous tissue i.e., inhibition of angiogenesis and killing of cancer cells by anticancer drug, might prove to be a promising approach in the treatment of fatal disease, cancer.

Pre-clinical toxicokinetics and safety study of M2ES, a PEGylated recombinant human endostatin, in rhesus monkeys.

PEGylated recombinant human endostatin (M2ES) exhibited prolonged serum half-life and enhanced antitumor activity when compared with endostatin. A non-clinical study was performed to evaluate the toxicokinetics and safety of M2ES in rhesus monkeys. After intravenous (IV) infusions of M2ES at a dose level of 3, 10, and 30mg/kg in rhesus monkeys, the concentration-time curves of M2ES were best fitted to a non-compartment model, and area under the curve (AUC) was positively correlated with the dosage. M2ES had a tendency to accumulate in vivo following successive IV infusions. Serum anti-M2ES IgG antibodies were generated quickly during IV administration, and the antibody level in serum did not significantly decrease after four-week recovery period. Animals administered IV infusions twice weekly (M2ES at 10 or 30mg/kg body weight per day) for 3months developed mild or moderate vacuolation of proximal tubule epithelial cell in proximal convoluted tubule of kidney, but this adverse-effect was reversible. In summary, M2ES was well tolerated and did not cause any serious toxicity. These pre-clinical safety data contribute to the initiation of the ongoing clinical study.

Cholesterol sequestration by nystatin enhances the uptake and activity of endostatin in endothelium via regulating distinct endocytic pathways.

Specific internalization of endostatin into endothelial cells has been proved to be important for its biologic functions. However, the mechanism of endostatin internalization still remains elusive. In this study, we report for the first time that both caveolae/lipid rafts and clathrin-coated pits are involved in endostatin internalization. Inhibition of either the caveolae pathway or the clathrin pathway with the use of chemical inhibitors, small interfering RNAs, or dominant-negative mutants alters endostatin internalization in vitro. Intriguingly, cholesterol sequestration by nystatin, a polyene antifungal drug, significantly enhances endostatin uptake by endothelial cells through switching endostatin internalization predominantly to the clathrin-mediated pathway. Nystatin-enhanced internalization of endostatin also increases its inhibitory effects on endothelial cell tube formation and migration. More importantly, combined treatment with nystatin and endostatin selectively enhances endostatin uptake and biodistribution in tumor blood vessels and tumor tissues but not in normal tissues of tumor-bearing mice, ultimately resulting in elevated antiangiogenic and antitumor efficacies of endostatin in vivo. Taken together, our data show a novel mechanism of endostatin internalization and support the potential application of enhancing the uptake and therapeutic efficacy of endostatin via regulating distinct endocytic pathways with cholesterol-sequestering agents.

Genetically engineered endostatin-lidamycin fusion proteins effectively inhibit tumor growth and metastasis.

BACKGROUND: Endostatin (ES) inhibits endothelial cell proliferation, migration, invasion, and tube formation. It also shows antiangiogenesis and antitumor activities in several animal models. Endostatin specifically targets tumor vasculature to block tumor growth. Lidamycin (LDM), which consists of an active enediyne chromophore (AE) and a non-covalently bound apo-protein (LDP), is a member of chromoprotein family of antitumor antibiotics with extremely potent cytotoxicity to cancer cells. Therefore, we reasoned that endostatin-lidamycin (ES-LDM) fusion proteins upon energizing with enediyne chromophore may obtain the combined capability targeting tumor vasculature and tumor cell by respective ES and LDM moiety. METHODS: In this study, we designed and obtained two new endostatin-based fusion proteins, endostatin-LDP (ES-LDP) and LDP-endostatin (LDP-ES). In vitro, the antiangiogenic effect of fusion proteins was determined by the wound healing assay and tube formation assay and the cytotoxicity of their enediyne-energized analogs was evaluated by CCK-8 assay. Tissue microarray was used to analyze the binding affinity of LDP, ES or ES-LDP with specimens of human lung tissue and lung tumor. The in vivo efficacy of the fusion proteins was evaluated with human lung carcinoma PG-BE1 xenograft and the experimental metastasis model of 4T1-luc breast cancer. RESULTS: ES-LDP and LDP-ES disrupted the formation of endothelial tube structures and inhibited endothelial cell migration. Evidently, ES-LDP accumulated in the tumor and suppressed tumor growth and metastasis. ES-LDP and ES show higher binding capability than LDP to lung carcinoma; in addition, ES-LDP and ES share similar binding capability. Furthermore, the enediyne-energized fusion protein ES-LDP-AE demonstrated significant efficacy against lung carcinoma xenograft in athymic mice. CONCLUSIONS: The ES-based fusion protein therapy provides some fundamental information for further drug development. Targeting both tumor vasculature and tumor cells by endostatin-based fusion proteins and their enediyne-energized analogs probably provides a promising modality in cancer therapy.

A tumor-penetrating peptide modification enhances the antitumor activity of endostatin in vivo.

Many antitumor drugs have a limited ability to penetrate more than a few cell diameters from blood vessels into solid tumors, which limits their effectiveness. In this study, we investigated whether the biological activity of endostatin can be enhanced by the addition of an integrin-targeting and permeability-enhancing sequence. The internalization RGD (CRGDKGPDC; iRGD) sequence was added at the carboxyl terminus of endostatin. Modification of endostatin with the iRGD motif showed specific and increased binding to endothelial cells; the increased binding correlated with an improved antiangiogenic property. iRGD-modified endostatin was more effective than human endostatin in inhibiting liver cancer growth in athymic mice. The finding indicates that addition of a vascular targeting and permeability sequence can enhance the biological activity of an antiangiogenic molecule and tumor targeting.

Tolerance and Pharmacokinetics of Recombinant Human Endostatin Administered as Single-Dose or Multiple-Dose Infusions in Patients With Advanced Solid Tumors: A Phase I Clinical Trial.

Objective: This study aimed to investigate the tolerance and pharmacokinetic characteristics of recombinant human endostatin (rh-endostatin) administered as single-dose or multiple-dose infusions in patients with advanced solid tumors. Methods: This phase I trial was designed as a single-center, single-arm, nonrandomized, open-label, dose-escalation study. The trial consisted of 2 parts: a single-dose part and a multiple-dose part, each with 3 dose comparison groups. Rh-endostatin was administered as an intravenous injection only once at a dose of 5 mg/m2, 7.5 mg/m2, or 10 mg/m2 in the single-dose part and as a daily intravenous injection for 14 days at the same doses in the multiple-dose part. The serum pharmacokinetics, toxicity and immunogenicity of rh-endostatin were evaluated. Results: Dose-limiting toxicity (DLT) was not observed in any group. A few patients developed cardiotoxicity, such as QT prolongation or narrow arrhythmia. Other adverse events were slight coagulation abnormalities and haematological abnormalities. For rh-endostatin doses of 5 mg/m2, 7.5 mg/m2, and 10 mg/m2, the mean Cmax values in the single-dose part were 344 ± 38.7 ng/mL, 524 ± 157 ng/mL, and 800 ± 201 ng/mL, respectively, and the average AUC0-t values were 3290 ± 3790 ng•h/mL, 4940 ± 4380 ng•h/mL, and 5050 ± 3980 ng•h/mL, respectively. The Cmax ss values of the 3 doses in the multiple-dose part were 575 ± 270 ng/mL, 531 ± 106 ng/mL, and 864 ± 166 ng/mL, respectively, and the AUC0-τ values were 3610 ± 1040 ng•h/mL, 3290 ± 1090 ng•h/mL, and 5180 ± 1210 ng•h/mL, respectively. The Cmax of a single-dose regimen showed linear kinetic characteristics. The patients in the single-dose group were negative for serum antibodies against rh-endostatin, while one patient in the multiple-dose group was positive. Conclusions: Rh-endostatin as a daily intravenous injection for 14 days in patients with advanced solid tumors is safe and well tolerated, without DLT, at doses of 5 mg/m2, 7.5 mg/m2, and 10 mg/m2. Serum antibodies against rh-endostatin were very low after multiple infusions. For phase II trials, the recommended rh-endostatin dose is 10 mg/m2 as a daily intravenous injection for 14 days.

Linking antibody Fc domain to endostatin significantly improves endostatin half-life and efficacy.

PURPOSE: The half-life of the antiangiogenic molecule endostatin that has been used in clinical trial is short ( approximately 2 h). In addition, approximately 50% of the clinical grade endostatin molecules lack four amino acids at their NH(2) termini. Lack of these amino acids gives rise to a molecule that is devoid of zinc, resulting in no antitumor activity. Our goal was to develop a new version of endostatin that does not show such deficiency. EXPERIMENTAL DESIGN: A recombinant human endostatin conjugated to the Fc domain of IgG was constructed and expressed in mammalian cell culture. The presence of Fc has been shown by previous investigators to play a major role in increasing the half-life of the molecule. Fc-endostatin was tested in tumor-bearing mice, and its half-life was compared with the clinical grade endostatin. RESULTS: The antitumor dose of Fc-endostatin was found to be approximately 100 times less than the clinical grade endostatin. The half-life of Fc-endostatin in the circulation was found to be weeks rather than hours, as observed for endostatin alone. In addition, a U-shaped curve was observed for antitumor activity of endostatin as a function of endostatin concentration delivered to the animals. CONCLUSION: Fc-endostatin is a superior molecule to the original clinical endostatin. Due to its long half-life, the amount of protein required is substantially reduced compared with the clinically tested endostatin. Furthermore, in view of the U-shaped curve of efficacy observed for endostatin, we estimate that the requirement for Fc-endostatin is approximately 700-fold less than endostatin alone. The half-life of endostatin is similar to that of vascular endothelial growth factor-Trap and Avastin, two other antiangiogenic reagents. We conclude that a new clinical trial of endostatin, incorporating Fc, may benefit cancer patients.

[Experimental research of endostatin microcapsules by periocular injection].

OBJECTIVE: To detect the release of endostatin in microcapsules of calcium alginate gel by emulsification-internal gelatification technology, to observe the distribution of Endostatin microcapsules in the eye by periocular injection and biocompatibility. METHODS: The calcium alginate gel microcapsules encapsulating endostatin were prepared by emulsification-internal gelatification technology, the release of endostatin in microcapsules in vitro was examined by uv-Spectrophotometry. 32 SD mice were divided into randomly four groups: group A, periocular injection of endostatin microcapsules 20 microl (2.4 g/L); group B, periocular injection of endostatin protein 20 microl (2.5 g/L); group C, periocular injection of null-Microcapsules 20 microl; group D, periocular injection of saline 20 microl. Western blot, immunohistochemical and enzyme-linked immunosorbent assay were used. Protein expression and pathology of the heart, liver, spleen, lung, kidney and periocular tissue were examined. Daily activities and eating condition were observed.t-test was used to analyze the data. RESULTS: SDS polyacrylamide gel electrophoresis showed strap of ES protein. Concentration of ES protein in superior schedule fluid gradually increased at 3, 7, 14, 21 days. A group: ES protein expression were observed in inner nuclear layer, outer nuclear layer and RPE lamina after periocular injection 7 or 14 days. B group: ES protein expression were observed in above tissues at 7 days, but not at 14 days. C and D group: ES protein expression were not observed in above tissues at 7 or 14 days. The results showed that Endostatin microcapsules was able to pass through the sclera and spread out in various retinal tissues. Concentration of endostatin in the homogenates of eyeball was (63.16 +/- 7.64) microg.L(-1).eye(-1) and (33.2 +/- 5.77) microg.L(-1).eye(-1) respectively after one and two weeks in A group, but (33.2 +/- 2.89) microg.L(-1).eye(-1) and (15.73 +/- 2.08) microg.L(-1).eye(-1). The concentration of endostatin was significant difference in two group, A group was obviously larger than B group (t = 6.364 and 4.920, P = 0.003 and 0.008 respectively). Periocular administration. Daily activities and eating condition were normal. The abnormality in important organs were not detected by pathologic examination. CONCLUSIONS: Endostatin microcapsules is able to release persistently, to pass through the sclera and spread out in various retinal tissues. There were good biocompatibility and not ill effect remarkably.

Pharmacokinetics of PEGylated recombinant human endostatin in rhesus monkeys.

To investigate the pharmacokinetics of PEGylated recombinant human endostatin (M2ES) in rhesus monkey. M2ES was administered to rhesus monkeys by intravenous bolus injection, and serum M2ES concentration was determined by a self-developed ELISA assay. Pharmacokinetic parameters were calculated using a non-compartmental model of WinNonlin V2.1A software. The standard curve of self-developed ELISA assay was fitted by four-parameter method. The limit of detection (LOD) and LOQ were 0.3050 ng/mL and 0.9140 ng/mL, respectively. Following IV infusions of M2ES at 0.3, 1, and 3 mg/kg in rhesus monkeys, the serum M2ES concentration-time curve was fitted with a non-compartment model. The pharmacokinetic parameters were evaluated as follows: Terminal elimination half-life (T1/2) of M2ES were 3.30 ±â€¯0.70, 29.50 ±â€¯18.80 and 24.60 ±â€¯8.90 h. Systemic clearance (CLsys) of M2ES were 339.60 ±â€¯66.30, 161.40 ±â€¯18.20 and 260.10 ±â€¯43.70 mL/h/kg. AUC(0-∞) values of M2ES were 909.30 ±â€¯199.60, 6251.00 ±â€¯739.60 and 11758.00 ±â€¯2010.10 ng∙h/mL. The dosage was positively correlated with AUC, and the correlation coefficient r2 = 0.9327. Self-developed ELISA assay could meet the requirements of serum M2ES concentration detection. PEGylation modification substantially expands the circulation time of recombinant human endostatin and effectively improves its pharmacokinetic behavior.

Characterization, bioactivity and pharmacokinetic study of a novel carbohydrate-peptide polymer: Glycol-split heparin-endostatin2 (GSHP-ES2).

Endostatin (ES) has attracted considerable attention for the treatment of anti-angiogenesis-related disorders. An 11-amino-acid peptide (ES2, IVRRADRAAVP) from the amino terminal of ES is of interest because it is the main active fragment of ES. However, both ES and ES2 have a poor stability and a short half-life, and other disadvantages need to be further resolved. Thus, we conjugated ES2 to glycol-split heparin derivatives (GSHPs) to yield the polymer-peptide conjugate, GSHP-ES2. This study showed that GSHP-ES2 exhibited increased stability, a wider pH activity range, better inhibition of endothelial cell proliferation, migration and tube formation in vitro, better anti-angiogenic activity and a longer half-life in vivo compared with ES2. These results also indicate that GSHP-ES2 has good potential for the treatment of angiogenesis-related diseases, either alone or in combination with other chemicals.

Pharmacokinetic and pharmacodynamic study of intratumoral injection of an adenovirus encoding endostatin in patients with advanced tumors.

Angiogenesis plays a pivotal role in tumor growth, tissue invasion and metastasis. Endostatin is an angiogenesis inhibitor and has been shown to reduce tumor growth in animal models. However, therapy with recombinant endostatin protein was hampered by its short half-life and very-low yield of bioactive protein. We performed a phase I dose-escalation clinical trial using intratumoral injection of an adenovirus containing human endostatin gene (Ad-rhE; E10A; 10(10)-10(12) virus particles (vp)) in 15 patients with advanced solid tumors. We observed intratumoral injections of E10A without dose-limiting toxicity. Most frequently reported E10A-related adverse events were transient fever and local response. Distribution studies revealed that the vector was detected in the blood, throat and injection site, but rarely in the urine and stool. An increased endostatin expression was detected using enzyme immunoassay in serum in 13 of 14 treated patients throughout the period of treatment despite the presence of neutralizing antiadenovirus antibody. Median serum basic fibroblast growth factor levels decreased from 32.4 pg ml(-1) at baseline to 24.9 pg ml(-1) after 28 days of first treatment. Thus, direct intratumoral injection of up to 10(12) vp of E10A to patients is well tolerated and further studies are necessary to define and increase clinical efficacy.

Early in vivo assessment of angiostatic therapy efficacy by molecular MRI.

Noninvasive diagnostic imaging methods to establish the efficacy of angiostatic therapies are becoming increasingly important with the first Food and Drug Administration approvals of such agents. Magnetic resonance molecular imaging is an imaging technique that allows the visualization of pathological processes in vivo with a better spatial resolution as compared with nuclear methods, such as photon emission tomography and single photon emission computed tomography. In this study, we used alpha(v)beta3 targeted bimodal liposomes to quantitate angiogenesis in a tumor mouse model with magnetic resonance imaging (MRI) and to evaluate the therapeutic efficacy of the angiogenesis inhibitors anginex and endostatin. The MRI findings were validated with fluorescence microscopy and showed a very good correlation with the microvessel density. In conclusion, this study provides evidence that molecular MRI can be used to noninvasively measure the efficacy of angiogenesis inhibitors during the course of therapy.

Bioactivity, pharmacokinetics, and immunogenicity assays in preclinical and clinical trials for recombinant human endostatin.

AIM: To determine the in vitro and in vivo bioactivity of recombinant human endostatin (rhEndostatin) and to analyze its pharmacokinetics and immunogenicity in rhesus monkeys and patients. METHODS: The physical chemical characteristics of rhEndostatin were detected according to Pharmacopoeia of the People's Republic of China (2005 edition, part III). Its in vitro and in vivo bioactivities were assayed via proliferation-inhibition on human umbilical vein endothelial cells and their inhibitory effect on tumor-bearing mice models. Serum concentrations of rhEndostatin in monkeys and patients were determined by an enzyme immunoassay method. RESULTS: The corresponding specific in vitro activities of rhEndostatin obtained from the cell counting method, 3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and lactate dehydrogenase assay, respectively, were 6.4 x 10(7), 6.7 x 10(7), and 3.8 x 10(8) U/mg, and the in vivo antitumoral potency was 4.04 x 10(7) U/mg. In rhesus monkeys, there were no gender differences in all pharmacokinetic parameters. Serum anti-rhEndostatin immunoglobulin (Ig)G antibodies were generated quickly after intravenous (iv) administration and decreased rapidly when therapy was stopped. In phase I clinical trials, linearity in the pharmacokinetics of rhEndostatin was indicated by dose-proportionate increases in the area under the curve and the maximum serum concentration. Serum rhEndostatin reached a steady-state level after 7 d of successive administration with the average concentration at a steady state of 272.44+/-91.98 ng/mL. Neither IgG nor IgM antibodies against rhEndostatin were observed in patients. CONCLUSION: RhEndostatin exhibited a definite proliferation- inhibition effect on HUVEC, and significant antitumoral activity in mice. The immunoreactivity of rhesus monkeys to rhEndostatin is common, and rhEndostatin showed no immunogenicity in patients in this trial. The results provide a basis for further clinical trials.

Higher Anti-angiogenesis Activity, Better Cellular Uptake and Longer Half-life of a Novel Glyco-modified Endostatin by Polysulfated Heparin.

BACKGROUND: Endostatin (ES) is a promising anti-angiogenesis protein and has been approved for the treatment of non-small cell lung cancer, but short half-life, poor stability and nonspecific delivery caused great pain to patients and produced unsatisfactory treatment effectiveness. OBJECTIVE: In this work, in order to overcome these disadvantages, ES was covalently modified by polysulfated heparin (PSH) with the expectancy of longer half-life, higher anti-angiogenesis activity and better cellular uptake. METHODS: To characterize the cellular uptake, flow cytometry and confocal laser scanning microscopy were used to study the intracellular localization of fluorescein isothiocyanate-labeled ES and PSH-ES in EAhy926 endothelial cells. Zebrafish model was used to study the anti-angiogenesis activities of ES and its derivatives in vivo. The 125I-radiolabeled ES and PSH-ES were administered to healthy BALC/c mice for the pharmacokinetics study. RESULTS: Compared with ES, better cellular uptake effects were detected in PSH-ES group. Both ES and PSH-ES showed inhibition on the intersegmental vessels formation, while PSH-ES displayed a higher one. The half-life of PSH-ES was lengthened and area under the curve (AUC) was increased. At the same time, ES and PSH-ES were both widely and rapidly distributed in the lungs, livers, kidneys and hearts with little difference. CONCLUSION: The results indicated that PSH displayed good properties as a novel glyco-modifier for protein and peptide. The results also showed that PSH-ES displayed better cellular uptake, higher antiangiogenesis activity and prolonged half-life, which would lead to better anti-tumour effects.

A LC-MS/MS method to monitor the concentration of HYD-PEP06, a RGD-modified Endostar mimetic peptide in rat blood.

HYD-PEP06 is a novel RGD-modified Endostar mimetic peptide with 30 amino acids that is intended to suppress the formation of neoplasm vessels. This assay was developed and validated to monitor the level of the peptide HYD-PEP06 in rat blood, using liquid chromatography tandem mass spectrometry (LC-MS/MS). HYD-PEP10, another peptide similar to the analyte, was used as an internal standard (IS). A triple quadrupole mass spectrometry in Multiple Reaction Monitoring (MRM) mode and an electrospray interface (ESI) in the positive mode were used for MS analysis. The analysis was optimized with addition of 0.3% formic acid (FA) into the mobile phase as well as with a needle washing solution to overcome the carryover effect. In addition, the carryover was reduced by optimizing the mobile phase gradient. Methanol was used as a diluent of working solutions to avoid any adsorption. Methanol:acetonitrile (1:1, v:v) containing 0.3% FA was employed to precipitate the blood samples. Unknown blood samples must be placed in ice bath immediately, and precipitating agents should be added within 30 min to ensure the stability of blood samples. The assay was established and validated. This method showed a good linear relationship for the HYD-PEP06 in the range of 10 ng·mL-1 to 2000 ng·mL-1, with R > 0.99. HYD-PEP06 was determined with accuracy values (RE%) of -5.06%-8.54%, intra- and inter-day precisions (RSD%) of 3.13%-4.87% and 4.81%-9.42%. The method was successfully in monitoring the concentration of HYD-PEP06 in rat blood.

A novel molecular agent for glioma angiogenesis imaging.

BACKGROUND: Gliomas are rich in blood vessels and are the most primary and malignant type of brain tumor affecting the central nervous system. A few fluorine-18 (F)-labeled imaging agents can be used for imaging of tumor angiogenesis. In the current study, F-labeled recombinant human endostatin (rh-endostatin) was developed and evaluated as a probe for PET imaging of tumor angiogenesis. MATERIALS AND METHODS: F-fluorobenzoyl-endostatin (F-FB-endostatin) was synthesized from radiolabeling of rh-endostatin with N-succinimidyl-4-F-fluorobenzoate produced by a facile module-assisted radiosynthesis procedure. Blocking studies were used to measure the relative affinities of F-FB-endostatin to human glioblastoma U87MG cells in tumor tissues rich with vessels. In addition, biodistribution, metabolic stability, and small-animal PET imaging studies were carried out with F-FB-endostatin using Institute of Cancer Research and U87MG tumor-bearing mice. RESULTS: Noninvasive small-animal PET imaging indicated that F-FB-endostatin showed rapid and good tumor uptake. The probe was rapidly cleared from the blood and most organs, resulting in excellent tumor-to-normal tissue contrasts. Tumor uptake and rapid clearance were further confirmed with biodistribution studies. Metabolite assays showed that the probe was highly stable, making it suitable for in-vivo applications. CONCLUSION: F-FB-endostatin shows promising in-vivo properties. Therefore, the promising properties of F-FB-endostatin indicate that this probe can be a powerful tool to evaluate the antiangiogenic therapy for gliomas and thus warrants further investigation as a novel PET probe for imaging of tumor angiogenesis.

Pharmacokinetics of recombinant human endostatin in rats.

The pharmacokinetics of recombinant human endostatin (rh-Endo) has not been established in the rat, although this species of animal is commonly used in the pharmacological studies of rh-Endo. This study aimed to investigate the pharmacokinetics, tissue distribution, and excretion of rh-Endo in rats. 125I-radiolabeled rh-Endo was administered to healthy rats by intravenous (i.v) bolus injection at 1.5, 4.5 and 13.5 mg/kg. The maximum plasma concentration (Cmax) and area under the plasma concentration versus time curve (AUC) of rh-Endo increased proportionally with the increase of the dosage. There were no significant differences in total body clearance (CL) and elimination half-life (t1/2beta) of rh-Endo among the three dosages used. A 93.5% and 2.2% of the radioactivity was recovered in the urine and feces, respectively, in bile-duct intact rats; whereas only 0.1% of the total radioactivity was excreted into the bile in bile-duct cannulated rats. rh-Endo was rapidly and widely distributed in the liver, kidneys, spleen and lungs. Furthermore, a significant allometric relationship between CL, but not volume of distribution (Vd) and t1/2beta of rh-Endo, and the body weight was observed across mouse, rat and monkey, with the predicted values in humans significantly lower than those observed in cancer patients. rh-Endo exhibited a linear pharmacokinetics in rats and it is mainly excreted through the urine.