Endogenous lectins and drug targeting

Preliminary efficacy of [90Y]DOTA-biotin-avidin radiotherapy against non-muscle invasive bladder cancer

PURPOSE

Bladder cancer represents 3% of all new cancer diagnoses per year. We propose intravesical radionuclide therapy using the β-emitter ⁹⁰Y linked to DOTA-biotin-avidin ([⁹⁰Y]DBA) to deliver short-range radiation against non-muscle invasive bladder cancer (NMIBC).

MATERIAL AND METHODS

Image-guided biodistribution of intravesical DBA was investigated in an animal model by radiolabeling DBA with the ⁶⁸Ga and dynamic microPET imaging following intravesical infusion of [⁶⁸Ga]DBA for up to 4 h and post-necropsy γ-counting of organs. The antitumor activity of [⁹⁰Y]DBA was investigated using an orthotopic MB49 murine bladder cancer model. Mice were injected with luciferase-expressing MB49 cells and treated via intravesical administration with 9.2 MBq of [⁹⁰Y]DBA or unlabeled DBA 3 days after the tumor implantation. Bioluminescence imaging was conducted after tumor implantation to monitor the bladder tumor growth. In addition, we investigated the effects of [⁹⁰Y]DBA radiation on urothelial histology with immunohistochemistry analysis of bladder morphology.

RESULTS

Our results demonstrated that DBA is contained in the bladder for up to 4 h after intravesical infusion. A single dose of [⁹⁰Y]DBA radiation treatment significantly reduced growth of MB49 bladder carcinoma. Attaching ⁹⁰Y-DOTA-biotin to avidin prevents its re-absorption into the blood and distribution throughout the rest of the body. Furthermore, immunohistochemistry demonstrated that [⁹⁰Y]DBA radiation treatment did not cause short-term damage to urothelium at day 10, which appeared similar to the normal urothelium of healthy mice.

CONCLUSION

Our data demonstrates the potential of intravesical [⁹⁰Y]DBA as a treatment for non-muscle invasive bladder cancer.

Targeted and ultrasound-triggered cancer cell injury using perfluorocarbon emulsion-loaded liposomes endowed with cancer cell-targeting and fusogenic capabilities

This study investigated the targeting and ultrasound-triggered injury of cancer cells using anticancer drug-free liposomes that contained an emulsion of perfluoropentane (ePFC5) and were co-modified with avidin as a targeting ligand for cancer cells and the hemagglutinating virus of Japan (HVJ) envelope to promote liposome fusion with the cells. These liposomes are designated as ePFC5-loaded avidin/HVJ liposomes. ePFC5-loaded liposomes were sensitized to ultrasound irradiation. Liposomes modified with avidin alone (avidin liposomes) showed binding to MCF-7 human breast cancer cells, and liposomes modified with HVJ envelope alone (HVJ liposomes) were found to fuse with MCF-7 cells. The irradiation of MCF-7 cells with 1 MHz ultrasound (30s, 1.2 W/cm(2), duty ratio 30%) combined with ePFC5-loaded avidin/HVJ liposomes resulted in a decrease in cell viability at 1h after irradiation to 43% of that of controls without ultrasound irradiation or liposomes. The cell viability was lower than that of cells treated with ultrasound irradiation with ePFC5-loaded avidin liposomes or ePFC5-loaded HVJ liposomes. This indicates that co-modification of liposome with avidin and HVJ envelope could enhance ultrasound-induced cell injury in the presence of ePFC5-loaded liposomes.

Targeted sonocatalytic cancer cell injury using avidin-conjugated titanium dioxide nanoparticles

In this study, we applied sonodynamic therapy to cancer cells based on the delivery of titanium dioxide (TiO2) nanoparticles (NPs) modified with avidin protein, which preferentially discriminated cancerous cells from healthy cells. Subsequently, hydroxyl radicals were generated from the TiO2 NPs after activation by external ultrasound irradiation (TiO2/US treatment). Although 30% of the normal breast cells (human mammary epithelial cells) exhibited the uptake of avidin-modified TiO2 NPs, over 80% of the breast cancer cells (MCF-7) exhibited the uptake of avidin-TiO2 NPs. Next the effect of the TiO2/US treatment on MCF-7 cell growth was examined for up to 96 h after 1-MHz ultrasound was applied (0.1 W/cm(2), 30 s) to cells that incorporated the TiO2 NPs. No apparent cell injury was observed until 24h after the treatment, but the viable cell concentration declined to 68% compared with the control at 96 h.

Effect of ultrasound irradiation on bacterial internalization and bacteria-mediated gene transfer to cancer cells

The present study demonstrates that ultrasound irradiation can facilitate bacteria-mediated gene delivery (bactofection). Escherichia coli modified with avidin were employed as a vehicle for delivery of the green fluorescent protein (GFP) gene, a model heterologous gene, into the breast cancer cell line MCF-7. Avidin-mediated binding of E. coli to MCF-7 cells enhanced the internalization of E. coli by approximately 17%, irrespective of the use of ultrasound irradiation. Furthermore, the use of ultrasound irradiation increased the internalization by approximately 5%, irrespective of the presence of avidin on the E. coli cell surface. The percentages of GFP-expressing MCF-7 cells at 24h after bactofection were below 0.5% and 2% for the case with only avidin-modification of E. coli cell surface and only ultrasound irradiation, respectively. However, combining avidin modification with the ultrasound treatment increased this value to 8%. Thus, the use of avidin-modified bacteria in conjunction with ultrasound irradiation has potential as an effective strategy for tumor-targeted bactofection.

Induction of apoptosis and cell cycle arrest in A549 human lung adenocarcinoma cells by surface-capping selenium nanoparticles: an effect enhanced by polysaccharide-protein complexes from Polyporus rhinocerus

Surface-capping agents play key roles in cellular uptake and biological activity of functional nanomaterials. In the present study, functionalized selenium nanoparticles (SeNPs) have been successfully synthesized using Polyporus rhinocerus water-soluble polysaccharide-protein complexes (PRW) as the capping agent during the reduction of selenium salts. The acquired monodisperse, spherical PRW-SeNPs presented desirable size distribution and stability in the solution. Moreover, PRW surface decoration significantly enhanced the cellular uptake of SeNPs via endocytosis. Exposure to PRW-SeNPs significantly inhibited the growth of A549 cells through induction of apoptosis and G2/M phase arrest (IC50 = 4.06 ± 0.25 μM) supported by an increase of sub-G1 and G2/M phase cell populations, DNA fragmentation, and chromatin condensation. Caspase-3/8 activation induced by PRW-SeNPs indicated that the activation of death receptors was the main cause of PRW-SeNP-induced apoptosis. Collectively, the results suggest that it is highly efficient to use PRW as a surface decorator of SeNPs to enhance cellular uptake and anticancer efficacy, and the PRW-SeNPs are potential chemopreventive agents for lung cancer therapy.

Trans-resveratrol loaded chitosan nanoparticles modified with biotin and avidin to target hepatic carcinoma

Conventional liver targeted system focuses on delivering drugs to liver, bringing toxicity on hepatic normal tissues. The purpose of this study is to construct a new system capable of specially targeting to hepatic carcinoma instead of the whole liver. Based on the fact that nanoparticles (NPs) bound with either biotin or avidin tend to accumulate in tumors and avidin-attached reagents were quickly eliminated from blood circulation and assembled in liver, trans-resveratrol loaded chitosan nanoparticles (CS-NPs), CS-NPs with the surface modified either by biotin (B-CS-NPs) or by both biotin and avidin (A-B-CS-NPs) were prepared and their physiochemical properties were investigated. The in vitro release profiles of the three NPs all conformed to bioexponential equation. Pharmacokinetic experiment indicated that A-B-CS-NPs rapidly assembled in liver after injection, with the highest liver targeting index of 2.70, while the modification of biotin attenuated the liver targeting ability of NPs. Inhibitory study on HepG2 cells declared that compared to trans-resveratrol solution and CS-NPs, both B-CS-NPs and A-B-CS-NPs significantly improved the anticancer activity. When incubated with HepG2 cells at high concentration for longer time, A-B-CS-NPs exhibited superior cytotoxicity than B-CS-NPs. This study exclaims that A-B-CS-NPs may be a potent drug delivery vector specially targeting to hepatic carcinoma.

Effect of cholesterol and sugar on the penetration of glycodendrimeric phenylporphyrins into biomimetic models of retinoblastoma cells membranes

Photodynamic therapy (PDT) is considered one efficient treatment against retinoblastoma. The specificity of a photosensitizer and its penetration into cancerous cells are crucial for achieving tumor necrosis. The selection of photosensitizers such as porphyrin derivatives by tumor cells thus depends to a large extent on their ability to interact with the biological membrane. In this work, we have studied by surface pressure measurements and fluorescence spectroscopy the interaction between three newly synthesized dendrimeric phenylporphyrins and monolayers or liposomes with increasing cholesterol content mimicking the retinoblastoma cell membrane. The morphology of phospholipid-cholesterol-porphyrin mixed monolayers was also analyzed by Brewster angle microscopy. The results showed that the increase in cholesterol content in the model membranes had almost no effect on the effective penetration of the drugs into the lipid layers. Conversely, the chemical structure of the glycodendrimeric phenylporphyrins and the presence of sugar moieties especially appeared to play a crucial role. Although the non-glycoconjugated phenylporphyrin penetrated to a greater extent than glycodendrimeric ones into the liposome membrane, this could be achieved at a high lipid/porphyrin ratio only. Glycodendrimeric porphyrins exhibited improved surface properties compared to the non-glycoconjugated derivative and could penetrate into lipid layers even at low lipid/porphyrin ratios and high surface pressures. Our work highlights the role in the passive diffusion of porphyrins into biomimetic cancer cell membranes, of complex interactions among the lipid molecules, the sugar moieties, and the hydrophobic macrocycle of the porphyrins.

Carbohydrate recognition by boronolectins, small molecules, and lectins

Carbohydrates are known to mediate a large number of biological and pathological events. Small and macromolecules capable of carbohydrate recognition have great potentials as research tools, diagnostics, vectors for targeted delivery of therapeutic and imaging agents, and therapeutic agents. However, this potential is far from being realized. One key issue is the difficulty in the development of "binders" capable of specific recognition of carbohydrates of biological relevance. This review discusses systematically the general approaches that are available in developing carbohydrate sensors and "binders/receptors," and their applications. The focus is on discoveries during the last 5 years.

Drug delivery of oligonucleotides by peptides

Oligonucleotides are promising tools for in vitro studies where specific downregulation of proteins is required. In addition, antisense oligonucleotides have been studied in vivo and have entered clinical trials as new chemical entities with various therapeutic targets such as antiviral drugs or for tumour treatments. The formulation of these substances were widely studied in the past. With this review we will focus on peptides used as drug delivery vehicles for oligonucleotides. Different strategies are summarised. Cationically charged peptides from different origins were used e.g. as cellular penetration enhancers or nuclear localisation tool. Examples are given for Poly-L-lysine alone or in combination with receptor specific targeting ligands such as asialoglycoprotein, galactose, growth factors or transferrin. Another large group of peptides are those with membrane translocating properties. Fusogenic peptides rich in lysine or arginine are reviewed. They have been used for DNA complexation and condensation to form transport vehicles. Some of them, additionally, have so called nuclear localisation properties. Here, DNA sequences, which facilitate intracellular trafficking of macromolecules to the nucleus were explored. Summarizing the present literature, peptides are interesting pharmaceutical excipients and it seems to be feasible to combine the specific properties of peptides to improve drug delivery devices for oligonucleotides in the future.

Polyfection as Nonviral Gene Transfer Method —Design of Novel Nonviral Vector Using α-Cyclodextrin—

Due to the growing concerns over the toxicity and immunogenicity of viral DNA delivery systems, DNA delivery via nonviral routes has become more desirable and advantageous. In particular, polycation complexes with DNA (polyplex) are attractive nonviral vectors. To design novel polycationic vectors, we prepared polyamidoamine starburst dendrimer (dendrimer) conjugates with three cyclodextrins (CDE conjugates) and three generations (G2, G3, and G4) of dendrimers. Of seven CDE conjugates, an alpha-CDE conjugate (G3) with an average degree of substitution (DS) of alpha-CyD of 2.4 [alpha-CDE conjugate (G3, DS 2.4)] showed greater gene transfer activity than dendrimers and other alpha-CDE conjugates with less cytotoxicity. These results suggest the potential use of alpha-CDE conjugate (G3, DS 2.4) as a polycationic vector in vitro and in vivo. Herein, I review a recent polyfection method, with special focus on alpha-CDE conjugate (G3, DS 2.4).

Imaging of intraperitoneal tumors with technetium-99m GSA

99mTc labeled galactosyl serum albumin (GSA) has been used clinically as a receptor-binding agent for the assessment of liver function. The aim of this study was to investigate the usefulness of 99mTc-GSA in intraperitoneal (i.p.) tumor imaging. A tumor model was established by i.p. inoculating nude mice with human ovarian cancer cell SHIN-3, or colon cancer cell LS 180. Radiolabels were i.p. injected into the tumor-bearing mice and the biodistribution of radioactivity was examined. After administration, 99mTc-GSA rapidly accumulated in the tumor. The tumor uptake was 5.82-8.46 %ID/g from 30 min to 6 h after the injection. Radioactivity in the blood was very low, less than 0.3 %ID/g, resulting in high tumor-to-blood ratio. Tumors could be clearly seen by scintigraphic imaging. Accumulation of i.p.-injected 99mTc labeled human serum albumin (HSA) in i.p. tumors was similar to that of 99mTc-GSA, but radioactivity of 99mTc-HSA in the circulation was high, resulting in a significantly lower tumor-to-blood ratio. In conclusion, 99mTc-GSA, when i.p. injected, accumulated in i.p. tumors and cleared from circulation rapidly, which would make it useful for the imaging of i.p. tumors.

Glycotargeting: the preparation of glyco-amino acids and derivatives from unprotected reducing sugars

Lectins are present on the surface of many cells. Many lectins actively recycle from membrane to endosomes and efficiently take up glycoconjugates in a sugar-dependent manner. On this basis, glycoconjugates, specially those obtained by chemical means, are good candidates as carriers of drugs, oligonucleotides or genes. In this paper, we present a panel of methods suitable to transform unprotected reducing oligosaccharides into glycosynthons designed to be easily linked to therapeutic agents. All the glycosynthons presented here are glycosylamines or derivatives, mainly glyco-amino acids or glycopeptides. Glycosylamines are easy to obtain, but they are very labile in slightly acidic or neutral medium; they must be stabilized, by acylation for instance. The coupling efficiency of a reducing sugar with ammonia as well as an alkylamine or an arylamine is higher at high temperature, however, because of the Amadori rearrangement, special conditions have to be selected to prepare the expected glycosylamine derivative with a high yield. Glycosylamines are easily acylated by N-protected amino acids, or by halogeno acids which can then be transformed into amino acids. Alternatively, unprotected reducing oligosaccharides may very efficiently be transformed into N-glycosyl-amino acids and then protected by N-acylation. With a glutamyl derivative having both the alpha-amino and the gamma-carboxylic groups free, the coupling and the acylation, which is intramolecular, are roughly quantitative. N-oligosaccharyl-amino acid derivatives are interesting glycosynthons, because their sugar moiety bears the specificity towards membrane lectins while the amino acid part has the capacity to easily substitute a therapeutic agent.

Avidin targeting of intraperitoneal tumor xenografts

BACKGROUND

Lectins (proteins that bind specific sugar molecules on glycoproteins and glycolipids) are expressed at various levels on the surface of tumor cells. Conjugation of cytotoxic agents to glycoproteins recognized by lectins could be useful in the treatment of tumors. Avidin (a highly glycosylated, positively charged protein found in egg white) contains terminal N-acetylglucosamine and mannose residues that bind to some lectins. In this study, we tested the ability of avidin, labeled through conjugation to radioactive biotin (a B vitamin), to target intraperitoneal tumors.

METHODS

Biotin was radioactively labeled with 111In. Four tumor models (one ovarian, one lung, and two colon) were established in nude mice by intraperitoneal injection of cultured cancer cells. The following two approaches were used in the intraperitoneal administration of avidin: 1) radioactive biotin-avidin conjugates were injected and 2) avidin was injected 1-24 hours before the injection of radioactive biotin (avidin pretargeting; avidin-biotin conjugates formed in vivo). The distribution of injected radioactivity in the tissues of treated animals was assessed.

RESULTS

Radiolabeled avidin localized highly and rapidly in the tumors. More than 50% of the administered dose of avidin-biotin conjugate accumulated per gram of tumor tissue 2 hours after injection; high tumor uptake of radioactivity was observed up to 24 hours after conjugate injection. In contrast, accumulation of radioactivity in normal tissues was low, yielding high tumor to nontumor ratios. With avidin pretargeting, accumulation of radioactivity in the liver, kidney, and spleen was reduced to a greater extent than that in the tumor, and tumor to nontumor ratios were increased.

CONCLUSIONS

Avidin may be a promising vehicle for the delivery of radioisotopes, drugs, toxins, or therapeutic genes to intraperitoneal tumors.

Evaluation of the efficiency of targeting of antitumor drugs: simulation analysis based on pharmacokinetic/pharmacodynamic considerations

Antitumor drugs can be classified into two groups; cell cycle phase nonspecific (type I) and specific (type II) drugs. The cytotoxic activity of type I drugs depends on the time-concentration product (AUC), whereas that of type II drugs is time-dependent. Therefore, not only the AUC in the target organ, but also the exposure time is an important factor for evaluating the efficiency of any delivery system for antitumor drugs. In the present study, we examined the factors governing the cytotoxicity of drugs in tumors based on a hybrid perfusion model. It is suggested that the increase in tumor tissue binding of drug results in an increased unbound drug mean residence time (MRTT,U), leading to the increased activity of type II drugs. In contrast, the cytotoxic activity of type I drugs is unaffected by the alteration in the tissue binding since the intracellular AUC defined for unbound drugs (AUCT,U) is unaffected by the extent of drug binding. We also found that the symmetrical increase in the permeability-surface area products (PS) for drug influx (PSinf) and efflux (PSeff) across the tumor plasma membrane results in the unaltered and reduced antitumor activity for the type I and type II drugs, respectively, due to the unaltered AUCT,U and to the reduced MRTT,U. The kinetic analysis suggests that the increase in PSinf/PSeff ratio results in the increased cytotoxic activity of both type I and type II drugs. Collectively, optimization of the antitumor activity can be attained by increasing the tissue binding for type II drugs and by increasing PSinf and/or by decreasing PSeff type I and type II drugs. The present simulation study was carried out by considering the pharmacodynamic features of antitumor drugs and was a method of predicting how the antitumor activity may change on altering each process (tissue binding and membrane permeability for the influx and efflux processes) which governs the characteristics of drug distribution to tumors.

Use of lectins as diagnostic and therapeutic tools for cancer

Within the past few years, lectins have become a well-established means for understanding varied aspects of cancer and metastasis. Evidence is now emerging that lectins are dynamic contributors to tumor cell recognition (surface markers), cell adhesion and localization, signal transduction across membranes, mitogenic stimulation, augmentation of host immune defense, cytotoxicity, and apoptosis. To advance understanding of these lectin-dependent processes, attempts are being made to discover new lectins that have one or more of these functions and to develop lectin- (or glycoconjugate-) based tools that could be used to home in on tumor cells. This review will summarize current research on the lectins and recent advances in the development of lectin-based diagnostic and therapeutic tools for cancer. Additionally, the future potential of lectin-based diagnosis and therapy is discussed.

Receptor mediated glycotargeting

Glycotargeting relies on carrier molecules possessing carbohydrates that are recognized and internalized by cell surface mammalian lectins. Numerous types of glycotargeting vehicles have been designed based on the covalent attachment of saccharides to proteins, polymers and other aglycones. These carriers have found their major applications in antiviral therapy, immunoactivation, enzyme replacement therapy and gene therapy. This review compared different types of glycotargeting agents and the lectins which have been successfully targeted to treat both model and human diseases. It may be concluded that the discovery of new mammalian lectins which endocytose their ligands will lead to the rapid development of new glycotargeting agents founded on the principles of carbohydrate-protein interactions.

Solasodine glycosides. In vitro preferential cytotoxicity for human cancer cells

Solamargine [(22R,25R)-spiro-5-en-3 beta-yl-alpha-L-rhamnopyranosyl- (1----2glu)-O-alpha-L-rhamnopyranozyl (1----4glu)-beta-D-glucopyranoze], a glycoside of solasodine preferentially inhibits the uptake of tritiated thymidine by cancer cells. In contrast, solamargine at equivalent concentration, and the mono- and diglycosides of solasodine have a limited effect on the uptake of tritiated thymidine for other cell types, including unstimulated lymphocytes and lymphocytes stimulated with Con A. In contrast the solasodine glycosides do not inhibit the uptake of tritiated thymidine by lymphocytes stimulated with PHA or PWM. The inhibition of tritiated thymidine uptake by solamargine and the mono- and di-glycosides of solasodine are dependent upon their cellular uptake by endogenous endocytic lectins (EELs). The mode of action of the solasodine glycosides, in particular solamargine, appears to be the induction of cell lysis, as determined by morphological examination.

[Tumor lectinology--status and perspectives of clinical application]

A detailed knowledge of the mechanisms of molecular recognition is a prerequisite to rationally improved diagnostic and therapeutic procedures in diseases. In addition to sequences of amino acids, carbohydrate structures apparently store biological information that is thought to be relevant for physiologically important processes. Such ligands, namely the carbohydrate part of cellular glycoconjugates, can be recognized by specific endogenous binding proteins like lectins. If their presence can be reliably ascertained and correlated to the clinical course of the disease, e.g. in oncology, lectinology may help to define a yet undisclosed role for this class of proteins in tumor progression and spread.

Muramyl dipeptide bound to poly-L-lysine substituted with mannose and gluconoyl residues as macrophage activators

Poly-L-lysine modified with mannose derivatives, the residual cationic charges of which being neutralized by N-acylation, were synthesized and used as carriers of a macrophage activator (N-acetylmuramyl dipeptide, MDP). The influence of the acylating agent on the targeting efficiency was investigated: a hydrosolubilizing group such as a gluconoyl moiety led to very efficient carrier conjugates, while an acetyl group did not. The effect of sugar and acyl content of the polymers was assessed using these compounds as inhibitors of red blood cell agglutination by Concanavalin A. The binding and specific endocytosis of poly-L-lysine substituted with several mannose derivatives and gluconoyl residues (GlcAx-, Man(y)-PLK) have been determined by a quantitative flow cytometry analysis. MDP bound to these conjugates was much more efficient in vitro than free MDP in macrophage cytostasis assays.