Tumor Endothelial Cell Targeted Cyclic RGD-modified Heparin Derivative: Inhibition of Angiogenesis and Tumor Growth

A review on multifaceted biomedical applications of heparin nanocomposites: Progress and prospects

Advances in polymer-based nanocomposites have revolutionized biomedical applications over the last two decades. Heparin (HP), being a highly bioactive polymer of biological origin, provides strong biotic competence to the nanocomposites, broadening the horizon of their applicability. The efficiency, biocompatibility, and biodegradability properties of nanomaterials significantly improve upon the incorporation of heparin. Further, inclusion of structural/chemical derivatives, fractionates, and mimetics of heparin enable fabrication of versatile nanocomposites. Modern nanotechnological interventions have exploited the inherent biofunctionalities of heparin by formulating various nanomaterials, including inorganic/polymeric nanoparticles, nanofibers, quantum dots, micelles, liposomes, and nanogels ensuing novel functionalities targeting diverse clinical applications involving drug delivery, wound healing, tissue engineering, biocompatible coatings, nanosensors and so on. On this note, the present review explicitly summarises the recent HP-oriented nanotechnological developments, with a special emphasis on the reported successful engagement of HP and its derivatives/mimetics in nanocomposites for extensive applications in the laboratory and health-care facility. Further, the advantages and limitations/challenges specifically associated with HP in nanocomposites, undertaken in this current review are quintessential for future innovations/discoveries pertaining to HP-based nanocomposites.

Biological aspects in controlling angiogenesis: current progress

All living beings continue their life by receiving energy and by excreting waste products. In animals, the arteries are the pathways of these transfers to the cells. Angiogenesis, the formation of the arteries by the development of pre-existed parental blood vessels, is a phenomenon that occurs naturally during puberty due to certain physiological processes such as menstruation, wound healing, or the adaptation of athletes' bodies during exercise. Nonetheless, the same life-giving process also occurs frequently in some patients and, conversely, occurs slowly in some physiological problems, such as cancer and diabetes, so inhibiting angiogenesis has been considered to be one of the important strategies to fight these diseases. Accordingly, in tissue engineering and regenerative medicine, the highly controlled process of angiogenesis is very important in tissue repairing. Excessive angiogenesis can promote tumor progression and lack of enough angiogensis can hinder tissue repair. Thereby, both excessive and deficient angiogenesis can be problematic, this review article introduces and describes the types of factors involved in controlling angiogenesis. Considering all of the existing strategies, we will try to lay out the latest knowledge that deals with stimulating/inhibiting the angiogenesis. At the end of the article, owing to the early-reviewed mechanical aspects that overshadow angiogenesis, the strategies of angiogenesis in tissue engineering will be discussed.

In Vitro and In Vivo Evaluation of Novel DTX-Loaded Multifunctional Heparin-Based Polymeric Micelles Targeting Folate Receptors and Endosomes

BACKGROUND

The development of biocompatible tumor-targeting delivery systems for anticancer agents is essential for efficacious cancer chemotherapy. Nanoparticles, as drug delivery cargoes for cancer therapy, are rapidly improving to overcome the limitations of conventional chemotherapeutic agents. Heparin-modified nanoparticles are currently being considered as one of the favorable carriers for the delivery of chemotherapeutics to cancer tissues.

OBJECTIVE

This study was aimed at evaluating the in vitro and in vivo antitumor activity of a novel targeted, pH-sensitive, heparin-based polymeric micelle loaded with the poorly water-soluble anticancer drug, docetaxel (DTX). The micelles could overcome the limited water solubility, non-specific distribution, and insufficient drug concentration in tumor tissues.

METHODS

DTX-loaded folate targeted micelles were prepared and evaluated for physicochemical properties, drug release, in vitro cellular uptake and cytotoxicity in folate receptor-positive and folate receptor-negative cells. Furthermore, the antitumor activity of DTX-loaded micelles was evaluated in the tumor-bearing mice. Some related patents were also studied in this research.

RESULTS

The heparin-based targeted micelles exhibited higher in vitro cellular uptake and cytotoxicity against folate receptor over-expressed cells due to the specific receptor-mediated endocytosis. DTX-loaded micelles displayed greater antitumor activity, higher anti-angiogenesis effects, and lower systemic toxicity compared with free DTX in a tumor-induced mice model as confirmed by tumor growth monitoring, immunohistochemical evaluation, and body weight shift. DTX-loaded targeting micelles demonstrated no considerable toxicity on major organs of tumor-bearing mice compared with free DTX.

CONCLUSION

Our results indicated that DTX-loaded multifunctional heparin-based micelles with desirable antitumor activity and low toxicity possess great potential as a targeted drug delivery system in the treatment of cancer.

Nanotechnology for angiogenesis: opportunities and challenges

Angiogenesis plays a critical role within the human body, from the early stages of life (i.e., embryonic development) to life-threatening diseases (e.g., cancer, heart attack, stroke, wound healing). Many pharmaceutical companies have expended huge efforts on both stimulation and inhibition of angiogenesis. During the last decade, the nanotechnology revolution has made a great impact in medicine, and regulatory approvals are starting to be achieved for nanomedicines to treat a wide range of diseases. Angiogenesis therapies involve the inhibition of angiogenesis in oncology and ophthalmology, and stimulation of angiogenesis in wound healing and tissue engineering. This review aims to summarize nanotechnology-based strategies that have been explored in the broad area of angiogenesis. Lipid-based, carbon-based and polymeric nanoparticles, and a wide range of inorganic and metallic nanoparticles are covered in detail. Theranostic and imaging approaches can be facilitated by nanoparticles. Many preparations have been reported to have a bimodal effect where they stimulate angiogenesis at low dose and inhibit it at higher doses.

cRGD-functionalized nanoparticles for combination therapy of anti-endothelium dependent vessels and anti-vasculogenic mimicry to inhibit the proliferation of ovarian cancer

Accumulating evidence has disclosed effective anti-angiogenic strategies should simultaneously inhibit endothelium-dependent vessels (EDV) and tumor cell-mediated vasculogenic mimicry (VM). The α_vβ₃ integrin-targeting peptide cRGD has the ability to inhibit EDV and we have found cRGD can also suppress the formation of VM in ovarian cancer cells. Herein, a cRGD-based combination strategy was developed to suppress the proliferation of tumor cells by anti-EDV and anti-VM. We firstly engineered two cRGD functionalized nanoparticles (cRGD-NPs1 and cRGD-NPs2) by self-assembly using heparin conjugated with cRGD and folate. In vitro experiments demonstrated cRGD-NPs2 exhibited more significant cytotoxicity and higher intracellular uptake ability than cRGD-NPs1. Also, cRGD-NPs2 could efficiently discourage EDV, VM and proliferation in HUVECs and SKOV3 (VM+) cells. In vivo studies showed cRGD-NPs2 could specifically accumulate in ovarian cancer tissues and exerted a superior anti-tumor effect in SKOV3 xenografts. The mechanisms responsible for creating anti-EDV and anti-VM action of cRGD-NPs2 related to combined effects of cRGD, heparin and folate. The results demonstrated cRGD-NPs2 represented a versatile anti-angiogenic medicine via their combined inhibitory effect. STATEMENT OF SIGNIFICANCE: Accumulating documents indicate tumor cell-mediated vasculogenic mimicry (VM) is positively correlated with poor prognosis, occurrence of distant metastasis and low survival rate in cancer patients, suggesting VM is a potential therapeutic target for cancer treatment. Thus, effective anti-angiogenic strategies should simultaneously inhibit VM as well as endothelium-dependent vessels (EDV). Integrin α_vβ₃ is a crucial inducer involved in the formation of both EDV and VM. In this study, we engineered α_vβ₃ integrin-targeting peptide cRGD functionalized nanoparticles (cRGD-NPs) by self-assembly using heparin conjugated with cRGD and folate. The prepared cRGD-NPs represent a promising anti-angiogenic medicine in that they are able to inhibit endothelial sprouting angiogenesis and tumor cell-mediated VM. This work may provide useful information with which to construct effective anti-angiogenic nanomedicines.

pH-activatable polymeric nanodrugs enhanced tumor chemo/antiangiogenic combination therapy through improving targeting drug release

It was widely accepted that polymeric nanodrugs held superiority in enhancing antitumor efficacy, reducing side effect and achieving better long-term prognosis. However, there still existed disputes that whether their therapeutic efficiency was closely related to insure effective release of hydrophobic drug located in their hydrophobic core in tumor site. In order to investigate this controversy, we constructed two polymeric nanodrugs (pH-activatable sLMWH-UOA and non-sensitive LMWH-UOA) with low molecular weight heparin (LMWH) and ursolic acid (UOA) for chemo-and anti-angiogenic combination therapy in hepatocellular carcinoma. The degradation ratio of pH-activatable sLMWH-UOA increased by 33% compared with non-sensitive LMWH-UOA in in vitro degradation study. Besides, confocal microscopy captured that sLMWH-UOA could effectively release drug in acidic microenvironment of lysosome while LMWH-UOA nearly could not. More importantly, in contrast with LMWH-UOA, sLMWH-UOA presented pH-dependent cytotoxicity, indicating that promoting drug release played a key role in enhancing the cytotoxicity of polymeric nanodrugs. Additionally, in vivo pharmacodynamic evaluation showed that although non-sensitive LMWH-UOA had benefited from enhanced tumor targeting drug delivery ability to achieve absolute advantage over free drug combination therapy in antitumor combination therapy, sLMWH-UOA could acquire further optimized combined therapeutic effect with better drug release in tumor. All above, application of tumor-triggered chemical bonds to construct polymeric nanodrugs held vast prospect for improving the therapeutic efficiency for tumor cells.

A targeted nanoplatform co-delivering chemotherapeutic and antiangiogenic drugs as a tool to reverse multidrug resistance in breast cancer

Several obstacles are currently impeding the successful treatment of breast cancer, namely impaired drug accumulation into the tumor site, toxicity to normal cells and narrow therapeutic index of chemotherapy, multidrug resistance (MDR) and the metastatic spread of cancer cells through the blood and lymphatic vessels. In this regard, we designed a novel multifunctional nano-sized drug delivery system based on LyP-1 peptide-modified low-molecular-weight heparin-quercetin conjugate (PLQ). This nanosystem was developed for targeted co-delivery of multiple anticancer drugs to p32-overexpressing tumor cells and peritumoral lymphatic vessels, using LyP-1 peptide as active targeting ligand, with the aim to achieve a targeted combinatorial chemo/angiostatic therapy and MDR reversal. The cellular uptake of PLQ nanoparticles by p32-overexpressing breast cancer cells was significantly higher than nonfunctionalized nanoparticles. Besides, the anti-angiogenic activity of PLQ nanoparticles was proven by the effective inhibition of the bFGF-induced neovascularization in subcutaneous Matrigel plugs. More importantly, PLQ/GA nanoparticles with better targeting ability toward p32-positive tumors, displayed a high antitumor outcome by inhibition of tumor cells proliferation and angiogenesis. Immunohistochemistry and western blot assay showed that PLQ/GA nanoparticles significantly disrupted the lymphatic formation of tumor, and inhibited the P-glycoprotein (P-gp) expression in MCF-7 tumor cells, respectively. In conclusion, PLQ/GA nanoparticles provide a synergistic strategy for effective targeted co-delivery of chemotherapeutic and antiangiogenic agents and reversing MDR and metastasis in breast cancer.

STATEMENT OF SIGNIFICANCE

Herein, we successfully developed a novel amphiphilic nanomaterial, LyP-1-LMWH-Qu (PLQ) conjugate, consisting of a tumor-targeting moiety LyP-1, a hydrophobic quercetin (a multidrug resistance [MDR]-reversing drug) inner core, and a hydrophilic low-molecular-weight heparin (an antiangiogenic agent) outer shell for encapsulating and delivering a hydrophobic chemotherapeutic agent (gambogic acid). This versatile nanoplatform with multiple targeted features, i.e., dual chemo/angiostatic effects, destruction ability of the peritumoral lymphatic vessels, and reversal of MDR, resulted in a significantly stronger antitumor efficacy and lower toxic side effect than those of nontargeted nanoparticles and the free drug solution. Therefore, this versatile nanosystem might provide a novel insight for the treatment and palliation of breast cancer by targeted co-delivery of chemo/antiangiogenic agents and reversing MDR and metastasis.

Sigma receptor-mediated targeted delivery of anti-angiogenic multifunctional nanodrugs for combination tumor therapy

The potential of low molecular weight heparin (LMWH) in anti-angiogenic therapy has been tempered by poor in vivo delivery to the tumor cell and potentially harmful side effects, such as the risk of bleeding due to heparin's anticoagulant activity. In order to overcome these limitations and further improve the therapeutic effect of LMWH, we designed a novel combination nanosystem of LMWH and ursolic acid (UA), which is also an angiogenesis inhibitor for tumor therapy. In this system, an amphiphilic LMWH-UA (LHU) conjugate was synthesized and self-assembled into core/shell nanodrugs with combined anti-angiogenic activity and significantly reduced anticoagulant activity. Furthermore, DSPE-PEG-AA-modified LHU nanodrugs (A-LHU) were developed to facilitate the delivery of nanodrugs to the tumor. The anti-angiogenic activity of A-LHU was investigated both in vitro and in vivo. It was found that A-LHU significantly inhibited the tubular formation of human umbilical vein endothelial cells (HUVECs) (p<0.01) and the angiogenesis induced by basic fibroblast growth factor (bFGF) in a Matrigel plug assay (p<0.001). More importantly, A-LHU displayed significant inhibition on the tumor growth in B16F10-bearing mice in vivo. The level of CD31 and p-VEGFR-2 expression has demonstrated that the excellent efficacy of antitumor was associated with a decrease in angiogenesis. In conclusion, A-LHU nanodrugs are a promising multifunctional antitumor drug delivery system.

Design and strategies for bile acid mediated therapy and imaging

Bioinspired materials have received substantial attention across biomedical, biological, and drug delivery research because of their high biocompatibility and lower toxicity compared with synthetic materials.

Designing polymers with sugar-based advantages for bioactive delivery applications

Sugar-based polymers have been extensively explored as a means to increase drug delivery systems' biocompatibility and biodegradation. Here,we review he use of sugar-based polymers for drug delivery applications, with a particular focus on the utility of the sugar component(s) to provide benefits for drug targeting and stimuli responsive systems. Specifically, numerous synthetic methods have been developed to reliably modify naturally-occurring polysaccharides, conjugate sugar moieties to synthetic polymer scaffolds to generate glycopolymers, and utilize sugars as a multifunctional building block to develop sugar-linked polymers. The design of sugar-based polymer systems has tremendous implications on both the physiological and biological properties imparted by the saccharide units and are unique from synthetic polymers. These features include the ability of glycopolymers to preferentially target various cell types and tissues through receptor interactions, exhibit bioadhesion for prolonged residence time, and be rapidly recognized and internalized by cancer cells. Also discussed are the distinct stimuli-sensitive properties of saccharide-modified polymers to mediate drug release under desired conditions. Saccharide-based systems with inherent pH- and temperature-sensitive properties, as well as enzyme-cleavable polysaccharides for targeted bioactive delivery, are covered. Overall, this work emphasizes inherent benefits of sugar-containing polymer systems for bioactive delivery.

Selective interaction of heparin with the variable region 3 within surface glycoprotein of laboratory-adapted feline immunodeficiency virus

Heparan sulfate proteoglycans (HSPG) can act as binding receptors for certain laboratory-adapted (TCA) strains of feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV). Heparin, a soluble heparin sulfate (HS), can inhibit TCA HIV and FIV entry mediated by HSPG interaction in vitro. In the present study, we further determined the selective interaction of heparin with the V3 loop of TCA of FIV. Our current results indicate that heparin selectively inhibits infection by TCA strains, but not for field isolates (FS). Heparin also specifically interferes with TCA surface glycoprotein (SU) binding to CXCR4, by interactions with HSPG binding sites on the V3 loop of the FIV envelope protein. Peptides representing either the N- or C-terminal side of the V3 loop and containing HSPG binding sites were able to compete away the heparin block of TCA SU binding to CXCR4. Heparin does not interfere with the interaction of SU with anti-V3 antibodies that target the CXCR4 binding region or with the interaction between FS FIV and anti-V3 antibodies since FS SU has no HSPG binding sites within the HSPG binding region. Our data show that heparin blocks TCA FIV infection or entry not only through its competition of HSPG on the cell surface interaction with SU, but also by its interference with CXCR4 binding to SU. These studies aid in the design and development of heparin derivatives or analogues that can inhibit steps in virus infection and are informative regarding the HSPG/SU interaction.

Bioreducible heparin-based nanogel drug delivery system

Bioreducible heparin (HEP)-based nanogels were prepared by derivatizing HEP with vinyl group followed by copolymerizing with cystamine bisacrylamide in aqueous medium in the absence of surfactant. The hydrodynamic diameter of the HEP nanogels could be tuned in the range from 80 to 200 nm. Doxorubicin (DOX) was loaded into the HEP nanogels, and high drug loading content (30%) and efficiency (90%) were achieved. In vitro drug release test revealed that this drug delivery system exhibited strongly redox-sensitive drug release behavior that would greatly favor the in vivo drug delivery performance of the nanogels. After injected into tumor-bearing mice through tail vein, the DOX-loaded HEP nanogels showed remarkable accumulation in tumors as demonstrated by in vivo near infared fluorescence imaging and ex vivo DOX concentration measurements. The doxorubicin accumulation at tumor site goes beyond 9% injected dose per gram of tumor through such delivery system, making that DOX-loaded HEP nanogels have significantly superior in vivo antitumor activity.

Application of polysaccharides for surface modification of nanomedicines

Polysaccharides have been used in various biomedical applications due to availability and biocompatibility. In particular, polysaccharides have gained increasing interest in the development of functional nanomedicines as a component to provide a stealth function, improve interactions with target tissues or enable environment-responsive drug release. This review discusses recent advances in nanomedicine engineering based on polysaccharides with a specific emphasis on the rationale, applications and the remaining challenges.

Dendronized heparin-doxorubicin conjugate based nanoparticle as pH-responsive drug delivery system for cancer therapy

Heparin drug conjugates are currently investigated as excellent candidates for drug delivery vehicles. In this study, we report the preparation and characterization of dendronized heparin-doxorubicin (heparin-DOX) conjugate as pH-sensitive drug delivery vehicle by combination of the features of dendrimer and heparin. Dynamic light scattering (DLS) and transmission electron microscope (TEM) studies demonstrated the dendronized heparin-DOX conjugate self-assembled into compact nanoparticles with negatively charged surface. The nanoparticles with 9.0 wt% (weight percent) of doxorubicin (DOX) showed pH-sensitive property due to the faster drug release rate at pH 5.0 and slow release rate at pH 7.4 aqueous. The nanoparticles were shown to effectively kill cancer cells in vitro. Notablely, the nanoparticles resulted in strong antitumor activity, high antiangiogenesis effects and induced apoptosis on the 4T1 breast tumor model due to the evidences from mice weight shifts, tumor weights, tumor growth curves, immunohistochemical assessment and histological analysis. It's also noteworthy that dendronized heparin and its nanoparticle with drug demonstrated no significant toxicity to healthy organs of both tumor-bearing and healthy mice, which was confirmed by histological analysis compared with free drug DOX. The dendronized heparin-DOX conjugate based nanopatilce with high antitumor activity and low side effects may be therefore a potential nanoscale drug delivery vehicle for breast cancer therapy.

Cancer treatment using peptides: current therapies and future prospects

This paper discusses the role of peptides in cancer therapy with special emphasis on peptide drugs which are already approved and those in clinical trials. The potential of peptides in cancer treatment is evident from a variety of different strategies that are available to address the progression of tumor growth and propagation of the disease. Use of peptides that can directly target cancer cells without affecting normal cells (targeted therapy) is evolving as an alternate strategy to conventional chemotherapy. Peptide can be utilized directly as a cytotoxic agent through various mechanisms or can act as a carrier of cytotoxic agents and radioisotopes by specifically targeting cancer cells. Peptide-based hormonal therapy has been extensively studied and utilized for the treatment of breast and prostate cancers. Tremendous amount of clinical data is currently available attesting to the efficiency of peptide-based cancer vaccines. Combination therapy is emerging as an important strategy to achieve synergistic effects in fighting cancer as a single method alone may not be efficient enough to yield positive results. Combining immunotherapy with conventional therapies such as radiation and chemotherapy or combining an anticancer peptide with a nonpeptidic cytotoxic drug is an example of this emerging field.

Cyclic RGDyk-conjugated LMWH-taurocholate derivative as a targeting angiogenesis inhibitor

LMWH-taurocholate derivative (LHT7) has been reported as a novel angiogenesis inhibitor, due to its ability to bind to several kinds of growth factors, which play critical roles in tumor angiogenesis. In this study, we have highlighted the enhanced antiangiogenic activity of LHT7, by using cyclic RGDyk (cRGD), a targeting moiety that was chemically conjugated to LHT7 via amide bond. The SPR study revealed that cRGD-LHT7 bound to α(v)β(3) integrin as strongly as cRGD, and it bound to VEGF as strongly as LHT7. Importantly, in vitro anti-angiogenesis studies revealed that cRGD-LHT7 had a significant inhibition effect on HUVEC tubular formation. Finally, cRGD-LHT7 showed a greater inhibitory efficiency on the tumor growth in the U87MG xenograft model than the original LHT7, which was owed to its ability to target the tumor cells. All of these findings demonstrated that cRGD-LHT7 targeted α(v)β(3) integrin-positive cancer cells and endothelial cells, resulting in a greater anti-angiogenesis effect on the solid tumors.

Anti-angiogenic peptides for cancer therapeutics

Peptides have emerged as important therapeutics that are being rigorously tested in angiogenesis-dependent diseases due to their low toxicity and high specificity. Since the discovery of endogenous proteins and protein fragments that inhibit microvessel formation (thrombospondin, endostatin) several peptides have shown promise in pre-clinical and clinical studies for cancer. Peptides have been derived from thrombospondin, collagens, chemokines, coagulation cascade proteins, growth factors, and other classes of proteins and target different receptors. Here we survey recent developments for anti-angiogenic peptides with length not exceeding 50 amino acid residues that have shown activity in pre-clinical models of cancer or have been tested in clinical trials; some of the peptides have been modified and optimized, e.g., through L-to-D and non-natural amino acid substitutions. We highlight technological advances in peptide discovery and optimization including computational and bioinformatics tools and novel experimental techniques.

Integrin-assisted drug delivery of nano-scaled polymer therapeutics bearing paclitaxel

Angiogenesis plays a prominent role in cancer progression. Anti-angiogenic therapy therefore, either alone or in combination with conventional cytotoxic therapy, offers a promising therapeutic approach. Paclitaxel (PTX) is a widely-used potent cytotoxic drug that also exhibits anti-angiogenic effects at low doses. However, its use, at its full potential, is limited by severe side effects. Here we designed and synthesized a targeted conjugate of PTX, a polymer and an integrin-targeted moiety resulting in a polyglutamic acid (PGA)-PTX-E-[c(RGDfK)(2)] nano-scaled conjugate. Polymer conjugation converted PTX to a macromolecule, which passively targets the tumor tissue exploiting the enhanced permeability and retention effect, while extravasating via the leaky tumor neovasculature. The cyclic RGD peptidomimetic enhanced the effects previously seen for PGA-PTX alone, utilizing the additional active targeting to the α(v)β(3) integrin overexpressed on tumor endothelial and epithelial cells. This strategy is particularly valuable when tumors are well-vascularized, but they present poor vascular permeability. We show that PGA is enzymatically-degradable leading to PTX release under lysosomal acidic pH. PGA-PTX-E-[c(RGDfK)(2)] inhibited the growth of proliferating α(v)β(3)-expressing endothelial cells and several cancer cells. We also showed that PGA-PTX-E-[c(RGDfK)(2)] blocked endothelial cells migration towards vascular endothelial growth factor; blocked capillary-like tube formation; and inhibited endothelial cells attachment to fibrinogen. Orthotopic studies in mice demonstrated preferential tumor accumulation of the RGD-bearing conjugate, leading to enhanced anti-tumor efficacy and a marked decrease in toxicity as compared with free PTX-treated mice.

Cyclic RGD-poly(ethylene glycol)-polyethyleneimine is more suitable for glioblastoma targeting gene transfer in vivo

Arginine-glycine-aspartic acid (RGD) is a widely chosen ligand to improve the specific gene targeting transfection efficiency of polyethyleneimine (PEI) in vivo. However, the optimal RGD conjugating mode, RGD-poly(ethylene glycol)-PEI (RGD-PEG-PEI) or RGD-PEI-methoxyl poly(ethylene glycol) (RGD-PEI-mPEG) still remains controversial. In this study, RGD-PEG-PEI and RGD-PEI-mPEG were synthesized and compared with respects to their glioblastoma cell-binding capability and tumor-targeting ability of their complexes with plasmid DNA. These results demonstrated that RGD-PEG-PEI/plasmid enhanced green fluorescent protein (pEGFP)-N2 complexes had higher binding affinities with U87 cells than RGD-PEI-mPEG/pEGFP-N2 complexes. The gene transfection was also performed on U87 cells in vitro and in vivo. In vitro, both of the RGD-modified PEI derivatives enhanced the gene transfection efficiency to some extent. However, all of the complexes (with or without RGD modification) had high transfection efficiency. The biodistribution of RGD-PEG-PEI/pEGFP-N2 complexes in mice bearing subcutaneous glioblastomas were significantly greater than that of RGD-PEI-mPEG/pEGFP-N2 complexes, suggesting a more efficient gene transfection in vivo. In the RGD-PEG-PEI, the use of a PEG spacer was particularly important. These results indicated that RGD-PEG-PEI was more suitable for targeted gene transfer in vivo.

The use of low molecular weight heparin-pluronic nanogels to impede liver fibrosis by inhibition the TGF-β/Smad signaling pathway

Low molecular weight heparin (LH) has been reported to have anti-fibrotic and anti-cancer effects. To enhance the efficacy and minimize adverse effects of LH, a low molecular weight heparin-pluronic nanogel (LHP) was synthesized by conjugating carboxylated pluronic F127 to LH. The LHP reduced anti-coagulant activity by about 33% of the innate activity. Liver fibrosis was induced by the injection of 1% dimethylnitrosamine (DMN) in rats, and LH or LHP (1000 IU/kg body weight) was treated once daily for 4 weeks. LHP administration prevented DMN-mediated liver weight loss and decreased the values of aspartate transaminase, alanine transaminase, total bilirubin, and direct bilirubin. LHP markedly reduced the fibrotic area compared to LH. Also, LHP potently inhibited mRNA or protein expression of alpha-smooth muscle actin, collagen type I, matrix metalloproteinase-2, and tissue inhibitor of metalloproteinase-1 compared to LH, in DMN-induced liver fibrosis. In addition, LHP decreased the expression of transforming growth factor-β(1) (TGF-β(1)), p-Smad 2, and p-Smad 3, which are all important molecules of the TGF-β/Smad signaling pathway. The results support an LHP shows anti-fibrotic effect in the liver via inhibition of the TGF-β/Smad pathway as well as by the elimination of the extracellular matrix.

RGD-xyloside conjugates prime glycosaminoglycans

Glycosaminoglycans (GAG) play decisive roles in various cardio-vascular & cancer-associated processes. Changes in the expression of GAG fine structures, attributed to deregulation of their biosynthetic and catabolic enzymes, are hallmarks of vascular dysfunction and tumor progression. The wide spread role of GAG chains in blood clotting, wound healing and tumor biology has led to the development of modified GAG chains, GAG binding peptides and GAG based enzyme inhibitors as therapeutic agents. Xylosides, carrying hydrophobic aglycone, are known to induce GAG biosynthesis in various systems. Given the important roles of GAG chains in vascular and tumor biology, we envision that RGD-conjugated xylosides could be targeted to activated endothelial and cancer cells, which are known to express α(v)β(3) integrin, and thereby modulate the pathological processes. To accomplish this vision, xylose residue was conjugated to linear and cyclic RGD containing peptides using click chemistry. Our results demonstrate that RGD-conjugated xylosides are able to prime GAG chains in various cell types, and future studies are aimed toward evaluating potential utility of such xylosides in treating myocardial infarction as well as cancer-associated thrombotic complications.

A novel fragment derived from the beta chain of human fibrinogen, beta43-63, is a potent inhibitor of activated endothelial cells in vitro and in vivo

BACKGROUND

Angiogenesis and haemostasis are closely linked within tumours with many haemostatic proteins regulating tumour angiogenesis. Indeed we previously identified a fragment of human fibrinogen, fibrinogen E-fragment (FgnE) with potent anti-angiogenic properties in vitro and cytotoxic effects on tumour vessels in vivo. We therefore investigated which region of FgnE was mediating vessel cytotoxicity.

METHODS

Human dermal microvascular endothelial cells (ECs) were used to test the efficacy of peptides derived from FgnE on proliferation, migration, differentiation, apoptosis and adhesion before testing the efficacy of an active peptide on tumour vasculature in vivo.

RESULTS

We identified a 20-amino-acid peptide derived from the beta chain of FgnE, beta43-63, which had no effect on EC proliferation or migration but markedly inhibited the ability of activated ECs to form tubules or to adhere to various constituents of the extracellular matrix - collagen IV, fibronectin and vitronectin. Furthermore, our data show that beta43-63 interacts with ECs, in part, by binding to alpha(v)beta(3), so soluble alpha(v)beta(3) abrogated beta43-63 inhibition of tubule formation by activated ECs. Finally, when injected into mice bearing tumour xenografts, beta43-63 inhibited tumour vascularisation and induced formation of significant tumour necrosis.

CONCLUSIONS

Taken together, these data suggest that beta43-63 is a novel anti-tumour peptide whose anti-angiogenic effects are mediated by alpha(v)beta(3).