Yoav D. Livney

Nanomedicine for targeted cancer therapy: Towards the overcoming of drug resistance

Anticancer drug resistance almost invariably emerges and poses major obstacles towards curative therapy of various human malignancies. In the current review we will distinguish between mechanisms of chemoresistance that are predominantly mediated by ATP-driven multidrug resistance (MDR) efflux transporters, typically of the ATP-binding cassette (ABC) superfamily, and those that are independent of such drug efflux pumps. In recent years, multiple nanoparticle (NP)-based therapeutic systems have been developed that were rationally designed to overcome drug resistance by neutralizing, evading or exploiting various drug efflux pumps and other resistance mechanisms. NPs are being exploited for selective drug delivery to tumor cells, to cancer stem/tumor initiating cells and/or to the supportive cancer cell microenvironment, i.e. stroma or tumor vasculature. Some of these NPs are currently undergoing preclinical in vivo studies as well as advanced stages of clinical evaluation with promising results. Nanovehicles harboring a payload of therapeutic drug combinations for the selective targeting and elimination of tumor cells as well as the simultaneous overcoming of mechanisms of drug resistance are a subject of intense research efforts, some of which are expected to enter clinical trials in the near future. In the present review we highlight novel approaches to selectively target cancer cells and overcome drug resistance phenomena, through the use of various nanometric drug delivery systems. In the near future, it is anticipated that innovative theragnostic nanovehicles will be developed which will harbor four major components: (1) a selective targeting moiety, (2) a diagnostic imaging aid for the localization of the malignant tumor and its micro- or macrometastases, (3) a cytotoxic, small molecule drug(s) or novel therapeutic biological(s), and (4) a chemosensitizing agent aimed at neutralizing a resistance mechanism, or exploiting a molecular Achilles hill of drug resistant cells. We propose to name these envisioned four element-containing nanovehicle platform, quadrugnostic nanomedicine. This targeted strategy holds promise in paving the way for the introduction of highly effective nanoscopic vehicles for cancer therapeutics while overcoming drug resistance.

Beta-casein nanovehicles for oral delivery of chemotherapeutic drugs ,

UNLABELLEDnBovine beta-casein (beta-CN) is an abundant milk protein that is highly amphiphilic and self-assembles into stable micellar structures in aqueous solutions. Here we introduce a drug-delivery system comprising a model hydrophobic anticancer drug, mitoxantrone (MX), entrapped within beta-CN-based nanoparticles. This novel drug-delivery system allows hydrophobic drugs to be thermodynamically stable in aqueous solutions for oral-delivery applications aimed at treatment of various disorders. The gastric digestibility of beta-CN suggests possible targeting to stomach tumors. Dimethyl sulfoxide (DMSO)-dissolved MX was entrapped in beta-CN nanoparticles by stirring this solution into phosphate-buffered beta-CN solution. High-affinity MX-beta-CN association was found (K(a) = [2.15 +/- 0.30] x 10(6) M(-1)). The optimal nanovehicle formation conditions were 1 mg/mL beta-CN, <or=6% (vol/vol) DMSO in phosphate-buffer solution, 10 mM MX in DMSO, and a MX:beta-CN molar-ratio of approximately 4:1. Under these conditions, particles of 100 to 300-nm diameter were formed. beta-CN nanoparticles may serve as effective oral-delivery nanovehicles for solubilization and stabilization of hydrophobic drugs.nnnFROM THE CLINICAL EDITORnBovine beta-casein (beta-CN) is an abundant milk-protein that is highly amphiphilic and self-assembles into stable micellar-structures in aqueous solutions. beta-CN nanoparticles may serve as effective oral-delivery nanovehicles for solubilization and stabilization of hydrophobic drugs, as demonstrated in this study utilizing methotrexate.

β-Casein nanoparticle-based oral drug delivery system for potential treatment of gastric carcinoma: Stability, target-activated release and cytotoxicity

We studied a potential drug delivery system comprising the hydrophobic anticancer drug paclitaxel entrapped within β-casein (β-CN) nanoparticles and its cytotoxicity to human gastric carcinoma cells. Paclitaxel was entrapped by stirring its dimethyl sulfoxide (DMSO) solution into PBS containing β-CN. Cryo-TEM analysis revealed drug nanocrystals, the growth of which was blocked by β-CN. Entrapment efficiency was nearly 100%, and the nanovehicles formed were colloidally stable. Following encapsulation and simulated digestion with pepsin (2 hours at pH=2, 37 °C), paclitaxel retained its cytotoxic activity to human N-87 gastric cancer cells; the IC(50) value (32.5 ± 6.2 nM) was similar to that of non-encapsulated paclitaxel (25.4 ± 2.6 nM). Without prior simulated gastric digestion, β-CN-paclitaxel nanoparticles were non-cytotoxic, suggesting the lack of untoward toxicity to bucal and esophageal epithelia. We conclude that β-CN shows promise to be useful for target-activated oral delivery of hydrophobic chemotherapeutics in the treatment of gastric carcinoma, one of the leading causes of cancer mortality worldwide.

β-casein nanovehicles for oral delivery of chemotherapeutic Drug combinations overcoming P-glycoprotein-mediated multidrug resistance in human gastric cancer cells.

Multidrug resistance (MDR) is a primary obstacle to curative cancer therapy. We have previously demonstrated that β-casein (β-CN) micelles (β-CM) can serve as nanovehicles for oral delivery and target-activated release of hydrophobic drugs in the stomach. Herein we introduce a novel nanosystem based on β-CM, to orally deliver a synergistic combination of a chemotherapeutic drug (Paclitaxel) and a P-glycoprotein-specific transport inhibitor (Tariquidar) individually encapsulated within β-CM, for overcoming MDR in gastric cancer. Light microscopy, dynamic light scattering and zeta potential analyses revealed solubilization of these drugs by β-CN, suppressing drug crystallization. Spectrophotometry demonstrated high loading capacity and good encapsulation efficiency, whereas spectrofluorometry revealed high affinity of these drugs to β-CN. In vitro cytotoxicity assays exhibited remarkable synergistic efficacy against human MDR gastric carcinoma cells with P-glycoprotein overexpression. Oral delivery of β-CN - based nanovehicles carrying synergistic drug combinations to the stomach constitutes a novel efficacious therapeutic system that may overcome MDR in gastric cancer.

Rationally designed nanovehicles to overcome cancer chemoresistance

Drug resistance is a primary hindrance towards curative cancer chemotherapy. Nanotechnology holds great promise in establishing efficacious and innovative strategies to overcome chemoresistance, and markedly facilitate complementary treatments and cancer diagnostics. Various nanomedical devices are being introduced and evaluated, demonstrating encouraging results. While stealth liposomes serve as a benchmark, astonishing progress is witnessed in polymeric nanovehicles, sometimes combined with low molecular weight surfactants, some of which inhibit drug resistance in addition to solubilizing drugs. Cutting edge multifunctional or quadrugnostic nanoparticles currently developed offer simultaneous targeted delivery of chemotherapeutics and chemosensitizers or drug-resistance gene silencing cargo, along with diagnostic imaging agents, like metallic NPs. Viral and cellular components offer exciting new routes for cancer targeting and treatment. Targeting intracellular compartments is another challenging frontier spawning pioneering approaches and results. To further enhance rational design of nanomedicine for overcoming drug resistance, we review the latest thoughts and accomplishments in recent literature.

Arabinogalactan−Folic Acid−Drug Conjugate for Targeted Delivery and Target-Activated Release of Anticancer Drugs to Folate Receptor-Overexpressing Cells

Folic acid (FA) is a high affinity ligand (K(d) = 0.1-1 nM) of folate receptors (FRs) responsible for cellular uptake of folates via receptor-mediated endocytosis. FRs are frequently overexpressed in malignant epithelial cells including ovary, brain, kidney, breast, colon, and lung. FR has emerged as a target for the differential-delivery of anticancer chemotherapeutics with several FA-linked therapeutic agents currently undergoing clinical trials. Here we show that by tethering both FA and the anticancer drug methotrexate (MTX) to arabinogalactan (AG), a highly branched natural polysaccharide with unusual water solubility, a targeted biomacromolecular nanovehicle is formed, which can differentially deliver a cytotoxic cargo into FR-overexpressing cells. Moreover, by linking MTX via an endosomally cleavable peptide (GFLG), we demonstrate a target-activated release mechanism. This FA-AG-GFLG-MTX drug conjugate displayed 6.3-fold increased cytotoxic activity to FR-overexpressing cells compared to their FR-lacking counterparts. These findings establish a novel FA-tethered polymeric nanoconjugate for the targeted delivery of antitumor agents into cancer cells overexpressing FR.

Beta-casein Nanoparticles as an Oral Delivery System for Chemotherapeutic Drugs: Impact of Drug Structure and Properties on Co-assembly

ABSTRACTPurposeTo develop a novel oral drug delivery system comprising a hydrophobic chemotherapeutic drug entrapped within beta casein (β–CN), a major milk protein, which self-associates into micelles in aqueous solutions. The efficient gastric digestibility of β–CN suggests possible targeting to gastric cancers.MethodsAntitumor drug entrapment was performed by stirring its dimethyl-sulfoxide solution into a phosphate-buffered saline containing β–CN. The association of drugs to β–CN was characterized by spectrophotometry and Trp143 fluorescence quenching; particle-size by dynamic light scattering, and colloidal stability by zeta potential.ResultsThe optimal drug-to-β–CN molar loading-ratios for paclitaxel and vinblastine at 1xa0mg/ml β–CN were found to be 7.3u2009±u20091.2 and 5.3u2009±u20090.6 and the association constants were (6.3u2009±u20091.0)·103xa0M−1 and (2.0u2009±u20090.3)·104xa0M−1, respectively. Zeta potential analysis suggested that nanoencapsulation by β–CN stabilized all studied drugs in aqueous solution. The initial drug-β–CN association was apparently governed by hydrophobic interactions and at higher drug concentrations, also by electrostatic interactions. Up to the optimal drug:β–CN loading-ratio, ~80% of the particles were below 100xa0nm in diameter. At higher drug concentrations, particle diameter increased, and bi- or tri-modal particle distributions were observed.ConclusionsBeta–CN forms colloidally-stable nanovehicles of hydrophobic anticancer drugs, and may be used for oral-delivery of chemotherapeutics.

Influence of thermal processing on the properties of dairy colloids

This review describes some of the effects of heat on several food systems containing milk proteins. Much of the recent research effort has been directed towards understanding the extensive effects of the thermal denaturation of the whey proteins (WPs) on the functional properties of heated systems (WP solutions and gels, emulsions and milks) that contain these proteins. Caseins play a more passive part during heating, apart from their specific interaction with denaturing WPs during the heat treatment of milk.

β-casein-based nanovehicles for oral delivery of chemotherapeutic drugs: drug-protein interactions and mitoxantrone loading capacity

Beta-casein (beta-CN), a major milk protein, is amphiphilic and self-associates into micelles in aqueous solutions. We have recently introduced a novel oral drug delivery system based on beta-CN nanoparticles. The current research builds on and complements this work by studying the interactions of mitoxantrone (MX) and beta-CN as they co-assemble into nanoparticles, using absorption and emission spectra, static and dynamic light scattering, and fluorescent emission of both MX and tryptophan 143 (Trp143) of beta-CN. The optimal loading molar ratio was 3.3 MX/beta-CN at 1 mg/mL beta-CN, and the association constant was (2.45 +/- 1.76) x 10(5) M(-1) based on beta-CN Trp143 fluorescence; independent MX fluorescence results provided supporting values. In these conditions a bimodal particle distribution was obtained (174.4 nm, 45.9%; 485.1 nm, 54.1%). The gastric digestibility of beta-CN suggests possible targeting to stomach tumors. Hence, beta-CN nanoparticles have potential to serve as effective vehicles of hydrophobic drugs for oral delivery preparations. From the clinical editor: Beta-casein (b-CN) is an amphiphilic milk protein that self-associates into micelles in aqueous solutions and can be utilized as a novel oral drug delivery system. This study investigates the basic properties of a mitoxantrone delivery system based on the above principles.

Targeted Nanomedicine for Cancer Therapeutics: Towards Precision Medicine Overcoming Drug Resistance

Intrinsic anticancer drug resistance appearing prior to chemotherapy as well as acquired resistance due to drug treatment, remain the dominant impediments towards curative cancer therapy. Hence, novel targeted strategies to overcome cancer drug resistance constitute a key aim of cancer research. In this respect, targeted nanomedicine offers innovative therapeutic strategies to overcome the various limitations of conventional chemotherapy, enabling enhanced selectivity, early and more precise cancer diagnosis, individualized treatment as well as overcoming of drug resistance, including multidrug resistance (MDR). Delivery systems based on nanoparticles (NPs) include diverse platforms enabling a plethora of rationally designed therapeutic nanomedicines. Here we review NPs designed to enhance antitumor drug uptake and selective intracellular accumulation using strategies including passive and active targeting, stimuli-responsive drug activation or target-activated release, triggered solely in the cancer cell or in specific organelles, cutting edge theranostic multifunctional NPs delivering drug combinations for synergistic therapy, while facilitating diagnostics, and personalization of therapeutic regimens. In the current paper we review the recent findings of the past four years and discuss the advantages and limitations of the various novel NPs-based drug delivery systems. Special emphasis is put on in vivo study-based evidences supporting significant therapeutic impact in chemoresistant cancers. A future perspective is proposed for further research and development of complex targeted, multi-stage responsive nanomedical drug delivery systems for personalized cancer diagnosis and efficacious therapy.