Tumour-selective drug delivery via folate receptor-targeted liposomes

Nano-inspired smart medicines targeting brain cancer: diagnosis and treatment

Cancer, despite being the bull's eye for the research community, accounts for a large number of morbidity and mortality. Cancer of the brain is considered the most intractable, with the least diagnosis rates, hence treatment and survival. Despite the extensive development of therapeutic molecules, their targeting to the diseased site is a challenge. Specially tailored nanoparticles can efficiently deliver drugs and genes to the brain to treat tumours and diseases. These nanotechnology-based strategies target the blood-brain barrier, the local space, or a specific cell type. These nanoparticles are preferred over other forms of targeted drug delivery due to the chances for controlled delivery of therapeutic cargo to the intended receptor. Targeted cancer therapy involves using specific receptor-blocking compounds that block the spreading or growth of cancerous cells. This review presents an account of the recent applications of nano-based cancer theragnostic, which deal in conjunct functionalities of nanoparticles for effective diagnosis and treatment of cancer. It commences with an introduction to tumours of the brain and their grades, followed by hurdles in its conventional diagnosis and treatment. The characteristic mechanism of nanoparticles for efficiently tracing brain tumour grade and delivery of therapeutic genes or drugs has been summarised. Nanocarriers like liposomes have been widely used and commercialized for human brain cancer treatment. However, nano-inspired structures await their translational recognition. The green synthesis of nanomaterials and their advantages have been discussed. The article highlights the challenges in the nano-modulation of brain cancer and its future outlook.

Antiangiogenic Targets for Glioblastoma Therapy from a Pre-Clinical Approach, Using Nanoformulations

Glioblastoma (GBM) is the most aggressive tumor type whose resistance to conventional treatment is mediated, in part, by the angiogenic process. New treatments involving the application of nanoformulations composed of encapsulated drugs coupled to peptide motifs that direct drugs to specific targets triggered in angiogenesis have been developed to reach and modulate different phases of this process. We performed a systematic review with the search criterion (Glioblastoma OR Glioma) AND (Therapy OR Therapeutic) AND (Nanoparticle) AND (Antiangiogenic OR Angiogenesis OR Anti-angiogenic) in Pubmed, Scopus, and Cochrane databases, in which 312 articles were identified; of these, only 27 articles were included after selection and analysis of eligibility according to the inclusion and exclusion criteria. The data of the articles were analyzed in five contexts: the characteristics of the tumor cells; the animal models used to induce GBM for antiangiogenic treatment; the composition of nanoformulations and their physical and chemical characteristics; the therapeutic anti-angiogenic process; and methods for assessing the effects on antiangiogenic markers caused by therapies. The articles included in the review were heterogeneous and varied in practically all aspects related to nanoformulations and models. However, there was slight variance in the antiangiogenic effect analysis. CD31 was extensively used as a marker, which does not provide a view of the effects on the most diverse aspects involved in angiogenesis. Therefore, the present review highlighted the need for standardization between the different approaches of antiangiogenic therapy for the GBM model that allows a more effective meta-analysis and that helps in future translational studies.

Lipid-based nanoparticle formulations for small molecules and RNA drugs

Introduction: Liposomes and lipid-based nanoparticles (LNPs) effectively deliver cargo molecules to specific tissues, cells, and cellular compartments. Patients benefit from these nanoparticle formulations by altered pharmacokinetic properties, higher efficacy, or reduced side effects. While liposomes are an established delivery option for small molecules, Onpattro® (Sanofi Genzyme, Cambridge, MA) is the first commercially available LNP formulation of a small interfering ribonucleic acid (siRNA). Areas covered: This review article summarizes key features of liposomal formulations for small molecule drugs and LNP formulations for RNA therapeutics. We describe liposomal formulations that are commercially available or in late-stage clinical development and the most promising LNP formulations for ASOs, siRNAs, saRNA, and mRNA therapeutics. Expert opinion: Similar to liposomes, LNPs for RNA therapeutics have matured but still possess a niche application status. RNA therapeutics, however, bear an immense hope for difficult to treat diseases and fuel the imagination for further applications of RNA drugs. LNPs face similar challenges as liposomes including limitations in biodistribution, the risk to provoke immune responses, and other toxicities. However, since properties of RNA molecules within the same group are very similar, the entire class of therapeutic molecules would benefit from improvements in a few key parameters of the delivery technology.

Specific targeting cancer cells with nanoparticles and drug delivery in cancer therapy

Nanotechnology has been the latest approach for diagnosis and treatment for cancer, which opens up a new alternative therapeutic drug delivery option to treat disease. Nanoparticles (NPs) display a broad role in cancer diagnosis and has various advantages over the other conventional chemotherapeutic drug delivery. NPs possess more specific and efficient drug delivery to the targeted tissue, cell, or organs and minimize the risk of side effects. NPs undergo passive and active mode of drug targets to tumor area with less elimination of the drug from the system. Size and surface characteristics of nanoparticles play a crucial role in modulating nanocarrier efficiency and the biodistribution of chemo drugs in the body. Several types of nanocarriers, such as polymers, dendrimers, liposome-based, and carbon-based, are studied widely in cancer therapy. Although FDA approved very few nanotechnology drugs for cancer therapy, a large number of studies are undergoing for the development of novel nanocarriers for potent cancer therapy. In this review, we discuss the details of the nano-based therapeutics and diagnostics strategies, and the potential use of nanomedicines in cancer therapy and cancer drug delivery.

Improved drug targeting to liver tumor by sorafenib-loaded folate-decorated bovine serum albumin nanoparticles

Background: To prepare sorafenib-loaded folate-decorated bovine serum nanoparticles (FA-SRF-BSANPs) and investigate their effect on the tumor targeting.

Methods: The nanoparticles were characterized and evaluated by in vivo and in vitro experiments.

Results: SRF-loaded BSA nanoparticles (SRF-BSANPs) was first prepared and modified with folic acid by chemical coupling to obtain FA-SRF-BSANPs. The average particle size, zeta potential, entrapment efficiency, and drug loading of the optimized FA-SRF-BSANPs were 158.00 nm, −16.27 mV, 77.25%, and 7.73%, respectively. The stability test showed that FA-SRF-BSANPs remained stable for more than 1 month at room temperature. The TEM analysis showed that the surface of FA-SRF-BSANPs was nearly spherical. XRD analysis showed that the drug existed in. the nanoparticles in an amorphous state. FA-SRF-BSANPs can promote the intracellular uptake of hepatoma cells (SMMC-7721) with the strongest inhibitory effect compared with SRF-BSANPs and sorafenib solution. Furthermore, the tumor targeting of FA-SRF-BSANPs (C_tumor/C_blood, 0.666 ± 0.053) was significantly higher than those of SRF-BSANPs (C_tumor/C_blood, 0.560 ± 0.083) and sorafenib-solution (C_tumor/C_blood, 0.410 ± 0.038) in nude mice with liver cancer.

Conclusion: FA-modified albumin nanoparticles are good carriers for delivering SRF to the tumor tissue, which can improve the therapeutic effect and reduce the side effects of the drug.

Therapeutic nanomedicine surmounts the limitations of pharmacotherapy

Science always strives to find an improved way of doing things and nanoscience is one such approach. Nanomaterials are suitable for pharmaceutical applications mostly because of their size which facilitates absorption, distribution, metabolism and excretion of the nanoparticles. Whether labile or insoluble nanoparticles, their cytotoxic effect on malignant cells has moved the use of nanomedicine into focus. Since nanomedicine can be described as the science and technology of diagnosing, treating and preventing diseases towards ultimately improving human health, a lot of nanotechnology options have received approval by various regulatory agencies. Nanodrugs also have been discovered to be more precise in targeting the desired site, hence maximizing the therapeutic effects, while minimizing side-effects on the rest of the body. This unique property and more has made nanomedicine popular in therapeutic medicine employing nanotechnology in genetic therapy, drug encapsulation, enzyme manipulation and control, tissue engineering, target drug delivery, pharmacogenomics, stem cell and cloning, and even virus-based hybrids. This review highlights nanoproducts that are in development and have gained approval through one clinical trial stage or the other.

Antitumor activity of a folate receptor-targeted immunoglobulin G-doxorubicin conjugate

Development of antibody-drug conjugates (ADCs) is a promising therapeutic strategy for cancer therapy. In this study, folate was conjugated via a polyethyleneglycol (PEG) linker to immunoglobulin G (IgG), which was linked to doxorubicin (DOX), to form a novel ADC folate-PEG-IgG-DOX (FA-PEG-IgG-DOX). The FA-PEG-IgG-DOX showed high targeting efficiency in HeLa and KB cells and significantly improved the uptake and retention of DOX compared with IgG-DOX about 10-fold. Subsequently, FA-PEG-IgG-DOX was shown to have at least 8 times higher antitumor activity than IgG-DOX both in HeLa and KB cells and also induced more apoptosis in those cells than IgG-DOX. Moreover, FA-PEG-IgG-DOX had a 2 times longer circulating time than FA-IgG-DOX, but did not increase the DOX distribution in mouse hearts. Importantly, FA-PEG-IgG-DOX treatment significantly inhibited tumor growth in xenograft mice. Together, our results indicate that FA-PEG-IgG is an effective ADC carrier for delivery of chemotherapeutic agents and that conjugating tumor targeting ligands to antibodies is a promising strategy for producing ADC drugs.

Supramolecular cyclodextrin nanocarriers for chemo- and gene therapy towards the effective treatment of drug resistant cancers

A tumor active targeting β-cyclodextrin based nanocarrier β-NC-OEI-SS-FA was designed by the modification of star shaped cationic derivatives β-NC-OEI with folic acid through a disulfide bond, to co-deliver chemotherapeutic paclitaxel and the Nur77 gene for overcoming Bcl-2 mediated non-pump resistance by an "enemy to friend" strategy for potential drug resistant cancer therapy.

Aptamer-Functionalized Nanoparticles as "Smart Bombs": The Unrealized Potential for Personalized Medicine and Targeted Cancer Treatment

Conventional delivery of chemotherapeutic agents leads to multiple systemic side effects and toxicity, limiting the doses that can be used. The development of targeted therapies to selectively deliver anti-cancer agents to tumor cells without damaging neighboring unaffected cells would lead to higher effective local doses and improved response rates. Aptamers are single-stranded oligonucleotides that bind to target molecules with both high affinity and high specificity. The high specificity exhibited by aptamers promotes localization and uptake by specific cell populations, such as tumor cells, and their conjugation to anti-cancer drugs has been explored for targeted therapy. Advancements in the development of polymeric nanoparticles allow anti-cancer drugs to be encapsulated in protective nonreactive shells for controlled drug delivery with reduced toxicity. The conjugation of aptamers to nanoparticle-based therapeutics may further enhance direct targeting and personalized medicine. Here we present how the combinatorial use of aptamer and nanoparticle technologies has the potential to develop "smart bombs" for targeted cancer treatment, highlighting recent pre-clinical studies demonstrating efficacy for the direct targeting to particular tumor cell populations. However, despite these pre-clinical promising results, there has been little progress in moving this technology to the bedside.

D, L-Sulforaphane Loaded Fe3O4@ Gold Core Shell Nanoparticles: A Potential Sulforaphane Delivery System

A novel design of gold-coated iron oxide nanoparticles was fabricated as a potential delivery system to improve the efficiency and stability of d, l-sulforaphane as an anticancer drug. To this purpose, the surface of gold-coated iron oxide nanoparticles was modified for sulforaphane delivery via furnishing its surface with thiolated polyethylene glycol-folic acid and thiolated polyethylene glycol-FITC. The synthesized nanoparticles were characterized by different techniques such as FTIR, energy dispersive X-ray spectroscopy, UV-visible spectroscopy, scanning and transmission electron microscopy. The average diameters of the synthesized nanoparticles before and after sulforaphane loading were obtained ∼ 33 nm and ∼ 38 nm, respectively, when ∼ 2.8 mmol/g of sulforaphane was loaded. The result of cell viability assay which was confirmed by apoptosis assay on the human breast cancer cells (MCF-7 line) as a model of in vitro-cancerous cells, proved that the bare nanoparticles showed little inherent cytotoxicity, whereas the sulforaphane-loaded nanoparticles were cytotoxic. The expression rate of the anti-apoptotic genes (bcl-2 and bcl-xL), and the pro-apoptotic genes (bax and bak) were quantified, and it was found that the expression rate of bcl-2 and bcl-xL genes significantly were decreased when MCF-7 cells were incubated by sulforaphane-loaded nanoparticles. The sulforaphane-loaded into the designed gold-coated iron oxide nanoparticles, acceptably induced apoptosis in MCF-7 cells.

Field-actuated antineoplastic potential of smart and versatile PEO–bPEI electrospun scaffold by multi-staged targeted co-delivery of magnetite nanoparticles and niclosamide–bPEI complexes

A PEO–bPEI based composite nanofiber scaffold has been realized for field actuated targeted delivery of magnetite nanoparticles and bPEI–niclosamide complexes for efficient management of cancer prognosis.

Synergic therapy of melanoma using GNRs-MUA-PEI/siIDO2-FA through targeted gene silencing and plasmonic photothermia

IDO2 siRNA synergizes GNR-mediated anti-melanoma photothermal therapy.

Discovery of Peptide ligands for hepatic stellate cells using phage display

Regardless of its cause, liver fibrosis is characterized by the excessive accumulation of extracellular matrix (ECM) in the liver. Hepatic stellate cells (HSCs) are the main producers responsible for the excessive production of ECM and profibrogenic cytokines in fibrotic liver. Therefore, development of HSC-specific delivery systems is essential for the success of antifibrotic agents. The objective of this study is to identify peptide ligands targeting the insulin-like growth factor 2 receptor (IGF2R), which is overexpressed on HSCs. We expect to use the peptide ligands for the future development of HSC-targeted drug delivery system. Protein- and whole cell-based phage display biopannings were conducted to identify phage/peptide candidates. Phage ELISA, cellular uptake, and cell viability assay were employed to evaluate the binding affinity and specificity of these peptide ligands to recombinant human IGF2R and HSCs. IGF2R siRNA was used to silence the IGF2R protein expression in human hepatic stellate cells (LX-2) to confirm the specificity of the identified peptide ligands. Among the identified peptide candidates, peptide-431 shows the highest binding affinity and specificity to recombinant human IGF2R protein and HSCs. The equilibrium dissociation constant (Kd) of peptide-431 is 6.19 μM for LX-2 cells and 12.35 μM for rat hepatic stellate cells HSC-T6. Cellular uptake of peptide-431 in LX-2 cells is significantly reduced after silencing IGF2R with siRNA. Peptide-431 also enhances the uptake of a proapoptotic peptide (KLA peptide) in LX-2 and HSC-T6 cells, indicating that peptide-431 can be used as a targeting ligand to deliver antifibrotic agents into not only rat but also human HSCs. Dimerization of peptide-431 further increase its binding affinity to LX-2 cells by approximately 9-fold.

Multifunctional core/shell nanoparticles cross-linked polyetherimide-folic acid as efficient Notch-1 siRNA carrier for targeted killing of breast cancer

In gene therapy, how genetic therapeutics can be efficiently and safely delivered into target tissues/cells remains a major obstacle to overcome. To address this issue, nanoparticles consisting of non-covalently coupled polyethyleneimine (PEI) and folic acid (FA) to the magnetic and fluorescent core/shell of Fe3O4@SiO2(FITC) was tested for their ability to deliver Notch-1 shRNA. Our results showed that Fe3O4@SiO2(FITC)/PEI-FA/Notch-1 shRNA nanoparticles are 64 nm in diameter with well dispersed and superparamagnetic. These nanoparticles with on significant cytotoxicity are capable of delivering Notch-1 shRNA into human breast cancer MDA-MB-231 cells with high efficiency while effectively protected shRNA from degradation by exogenous DNaseI and nucleases. Magnetic resonance (MR) imaging and fluorescence microscopy showed significant preferential uptake of Fe3O4@SiO2(FITC)/PEI-FA/Notch-1 shRNA nanocomplex by MDA-MB-231 cells. Transfected MDA-MB-231 cells exhibited significantly decreased expression of Notch-1, inhibited cell proliferation, and increased cell apoptosis, leading to the killing of MDA-MB-231 cells. In light of the magnetic targeting capabilities of Fe3O4@SiO2(FITC)/PEI-FA, our results show that by complexing with a second molecular targeting therapeutic, such as Notch-1 shRNA in this report, Fe3O4@SiO2(FITC)/PEI-FA can be exploited as a novel, non-viral, and concurrent targeting delivery system for targeted gene therapy as well as for MR imaging in cancer diagnosis.

Plasma and cellular pharmacokinetic considerations for the development and optimization of antitumor block copolymer micelles

INTRODUCTION

Clinical application of anticancer drugs is often limited by poor pharmacokinetic profile. The biocompatible and/or biodegradable block copolymer micelles (BCMs) can improve the pharmacokinetic behavior of drugs, thus enhancing antitumor effect. However, there are still many problems that needed to be solved before there is a wide clinical application of BCMs.

AREAS COVERED

Micelles have been quickly developed recently to deliver hydrophobic antitumor drugs specifically. However, the final therapeutic effect of BCMs is often challenged by many factors in vivo from both plasma and cellular pharmacokinetic view: i) inefficient transport from administration site to tumor tissue; ii) poor penetration into tumor mass; iii) inadequate accumulation in tumor cell; and iv) insufficient intracellular/subcellular release in cells. This review emphasized on the newest methods and solutions based on the main challenges of BCMs application in vivo, and the new problems caused by these methods are also discussed.

EXPERT OPINION

Different strategies and designs of BCMs can help solve problems in each key step respectively. However, overemphasis on one aspect will result in problems on others. Therefore, a comprehensive consideration is urgently needed to integrate the advantages of each strategy and overcome the disadvantages. Only with thorough understanding and scientific assessments, the desired BCMs are expected to be applied in clinical treatments.

Antifolate-modified iron oxide nanoparticles for targeted cancer therapy: inclusion vs. covalent union

In this work four different iron oxide nanoparticles for the delivery of antitumoral drugs into cancer cells were synthesized and characterized.

Assessing the transport of receptor-mediated drug-delivery devices across cellular monolayers

Receptor-mediated endocytosis (RME) has been extensively studied as a method for augmenting the transport of therapeutic devices across monolayers. These devices range from simple ligand-therapeutic conjugates to complex ligand-nanocarrier systems. However, characterizing the uptake of these carriers typically relies on their comparisons to the native therapeutic, which provides no understanding of the ligand or cellular performance. To better understand the potential of the RME pathway, a model for monolayer transport was designed based on the endocytosis cycle of transferrin, a ligand often used in RME drug-delivery devices. This model established the correlation between apical receptor concentration and transport capability. Experimental studies confirmed this relationship, demonstrating an upper transport limit independent of the applied dose. This contrasts with the dose-proportional pathways that native therapeutics rely on for transport. Thus, the direct comparison of these two transport mechanisms can produce misleading results that change with arbitrarily chosen doses. Furthermore, transport potential was hindered by repeated use of the RME cycle. Future studies should base the success of this technology not on the performance of the therapeutic itself, but on the capabilities of the cell. Using receptor-binding studies, we were able to demonstrate how these capabilities can be predicted and potentially adopted for high-throughput screening methods.

Lipid-insertion enables targeting functionalization of erythrocyte membrane-cloaked nanoparticles

RBC membrane-cloaked polymeric nanoparticles represent an emerging nanocarrier platform with extended circulation in vivo. A lipid-insertion method is employed to functionalize these nanoparticles without the need for direct chemical conjugation. Insertion of both folate and the nucleolin-targeting aptamer AS1411 shows receptor-specific targeting against model cancer cell lines.

Prospects in folate receptor-targeted radionuclide therapy

Targeted radionuclide therapy is based on systemic application of particle-emitting radiopharmaceuticals which are directed toward a specific tumor-associated target. Accumulation of the radiopharmaceutical in targeted cancer cells results in high doses of absorbed radiation energy whereas toxicity to non-targeted healthy tissue is limited. This strategy has found widespread application in the palliative treatment of neuroendocrine tumors using somatostatin-based radiopeptides. The folate receptor (FR) has been identified as a target associated with a variety of frequent tumor types (e.g., ovarian, lung, brain, renal, and colorectal cancer). In healthy organs and tissue FR-expression is restricted to only a few sites such as for instance the kidneys. This demonstrates why FR-targeting is an attractive strategy for the development of new therapy concepts. Due to its high FR-binding affinity (K_D < 10⁻⁹ M) the vitamin folic acid has emerged as an almost ideal targeting agent. Therefore, a variety of folic acid radioconjugates for nuclear imaging have been developed. However, in spite of the large number of cancer patients who could benefit of a folate-based radionuclide therapy, a therapeutic concept with folate radioconjugates has not yet been envisaged for clinical application. The reason is the generally high accumulation of folate radioconjugates in the kidneys where emission of particle-radiation may result in damage to the renal tissue. Therefore, the design of more sophisticated folate radioconjugates providing improved tissue distribution profiles are needed. This review article summarizes recent developments with regard to a therapeutic application of folate radioconjugates. A new construct of a folate radioconjugate and an application protocol which makes use of a pharmacological interaction allowed the first preclinical therapy experiments with radiofolates. These results raise hope for future application of such new concepts also in the clinic.

Liposomal antibiotics for the treatment of infectious diseases

INTRODUCTION

Liposomal delivery systems have been utilized in developing effective therapeutics against cancer and targeting microorganisms in and out of host cells and within biofilm community. The most attractive feature of liposome-based drugs are enhancing therapeutic index of the new or existing drugs while minimizing their adverse effects.

AREAS COVERED

This communication provides an overview on several aspects of liposomal antibiotics including the most widely used preparation techniques for encapsulating different agents and the most important characteristic parameters applied for examining shape, size and stability of the spherical vesicles. In addition, the routes of administration, liposome-cell interactions and host parameters affecting the biodistribution of liposomes are highlighted.

EXPERT OPINION

Liposomes are safe and suitable for delivery of variety of molecules and drugs in biomedical research and medicine. They are known to improve the therapeutic index of encapsulated agents and reduce drug toxicity. Recent studies on liposomal formulation of chemotherapeutic and bioactive agents and their targeted delivery show liposomal antibiotics potential in the treatment of microbial infections.

Polymer-coated echogenic lipid nanoparticles with dual release triggers

Although lipid nanoparticles are promising drug delivery vehicles, passive release of encapsulated contents at the target site is often slow. Herein, we report contents release from targeted, polymer-coated, echogenic lipid nanoparticles in the cell cytoplasm by redox trigger and simultaneously enhanced by diagnostic frequency ultrasound. The lipid nanoparticles were polymerized on the external leaflet using a disulfide cross-linker. In the presence of cytosolic concentrations of glutathione, the lipid nanoparticles released 76% of encapsulated contents. Plasma concentrations of glutathione failed to release the encapsulated contents. Application of 3 MHz ultrasound for 2 min simultaneously with the reducing agent enhanced the release to 96%. Folic acid conjugated, doxorubicin-loaded nanoparticles showed enhanced uptake and higher cytotoxicity in cancer cells overexpressing the folate receptor (compared to the control). With further developments, these lipid nanoparticles have the potential to be used as multimodal nanocarriers for simultaneous targeted drug delivery and ultrasound imaging.

Folate receptor in adenocarcinoma and squamous cell carcinoma of the lung: potential target for folate-linked therapeutic agents

CONTEXT

Lung cancer is the number one cause of cancer deaths in the United States and globally. The advent of targeted therapies has offered a new treatment paradigm for lung cancer, but currently validated and emerging drugs are effective in only a small minority of lung cancers, predominantly adenocarcinomas. Folate receptors can serve as targets for drugs attached to folate and are overexpressed in many cancers.

OBJECTIVE

To determine the frequency of folate receptor overexpression in lung cancers of different cell types as potential targets for folate-linked therapy.

DESIGN

High-density tissue microarrays were constructed from archival formalin-fixed, paraffin-embedded resection specimens from 188 primary stage I or stage II adenocarcinomas or squamous cell carcinomas of the lung with three 0.1-cm cores from each tumor. Tissue microarrays were immunostained for folate receptor α with mAb343 and the results scored (0 to 1+ = weak expression, 2+ to 3+ = strong expression).

RESULTS

Eighty-four of 117 (72%) of the adenocarcinomas were strongly positive for the folate receptor, and 36 of 71 (51%) of the squamous cell carcinomas were strongly positive for the folate receptor.

CONCLUSIONS

Our data indicate that a large percentage of lung cancers, including squamous cell carcinomas in addition to adenocarcinomas, strongly express folate receptor. This suggests that folate-linked targeted therapy can potentially be used to treat the majority of lung cancers, both adenocarcinomas and, particularly, squamous cell carcinomas, that do not respond to current targeted therapies.

Differential expression of folate receptor-alpha, sodium-dependent multivitamin transporter, and amino acid transporter (B (0, +)) in human retinoblastoma (Y-79) and retinal pigment epithelial (ARPE-19) cell lines

PURPOSE

The overall objective of this study was to investigate the differential expression of folate receptor-alpha (FR-α), sodium-dependent multivitamin transporter (SMVT), and amino acid transporter [B ((0, +))] in retinoblastoma (Y-79) and retinal pigment epithelial (ARPE-19) cells.

METHODS

Polymerase chain reaction (PCR) analysis was performed to confirm the existence of FR-α, SMVT, and B ((0, +)) in Y-79 and ARPE-19 cell lines. Quantitative real-time PCR was also performed to determine the relative expression of FR-α, SMVT, and B ((0, +)) at mRNA level in these cell lines. Quantitative uptake of [(3)H] Folic acid, [(3)H] Biotin, and [(14)C] Arginine was studied in Y-79 and ARPE-19 cells. Further, saturation kinetics of [(3)H] Folic acid, [(3)H] Biotin, and [(14)C] Arginine was performed in the presence of various concentrations of respective cold substrates to determine the kinetic parameters (K(m) and V(max)) in Y-79 and ARPE-19 cells.

RESULTS

PCR analysis had confirmed the existence of FR-α, SMVT, and B ((0, +)) in Y-79 and ARPE-19 cells. Quantitative real-time PCR analysis had shown significantly higher expression of FR-α, SMVT, and B ((0, +)) mRNA levels in Y-79 cells compared with ARPE-19 cells. Quantitative uptake of [(3)H] Folic acid, [(3)H] Biotin, and [(14)C] Arginine was found to be significantly higher in Y-79 cells relative to ARPE-19 cells. [(3)H] Folic acid uptake process followed saturation kinetics with apparent K(m) of 8.29 nM and V(max) of 393.47 fmol/min/mg protein in Y-79 cells and K(m) of 80.55 nM and V(max) of 491.86 fmol/min/mg protein in ARPE-19 cells. [(3)H] Biotin uptake process also displayed saturation kinetics with K(m) of 8.53 μM and V(max) of 14.12 pmol/min/mg protein in Y-79 cells and K(m) of 138.25 μM and V(max) of 38.85 pmol/min/mg protein in ARPE-19 cells. [(14)C] Arginine uptake process followed saturation kinetics with K(m) of 16.77 μM and V(max) of 348.27 pmol/min/mg protein in Y-79 cells and K(m) of 52.03 μM and V(max) of 379.21 pmol/min/mg protein in ARPE-19 cells.

CONCLUSIONS

This work demonstrated for the first time the higher expression and affinity of FR-α, SMVT, and B ((0, +)) mRNA levels in retinoblastoma (Y-79) cells compared with retinal pigment epithelial (ARPE-19) cells.

Biophysical characterization of a riboflavin-conjugated dendrimer platform for targeted drug delivery

The present study describes the biophysical characterization of generation-five poly(amidoamine) (PAMAM) dendrimers conjugated with riboflavin (RF) as a cancer-targeting platform. Two new series of dendrimers were designed, each presenting the riboflavin ligand attached at a different site (isoalloxazine at N-3 and d-ribose at N-10) and at varying ligand valency. Isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) were used to determine the binding activity for riboflavin binding protein (RfBP) in a cell-free solution. The ITC data shows dendrimer conjugates have K(D) values of ≥ 465 nM on a riboflavin basis, an affinity ~93-fold lower than that of free riboflavin. The N-3 series showed greater binding affinity in comparison with the N-10 series. Notably, the affinity is inversely correlated with ligand valency. These findings are also corroborated by DSC, where greater protein-conjugate stability is achieved with the N-3 series and at lower ligand valency.

Dendrimer-based multivalent methotrexates as dual acting nanoconjugates for cancer cell targeting

Cancer-targeting drug delivery can be based on the rational design of a therapeutic platform. This approach is typically achieved by the functionalization of a nanoparticle with two distinct types of molecules, a targeting ligand specific for a cancer cell, and a cytotoxic molecule to kill the cell. The present study aims to evaluate the validity of an alternative simplified approach in the design of cancer-targeting nanotherapeutics: conjugating a single type of molecule with dual activities to nanoparticles, instead of coupling a pair of orthogonal molecules. Herein we investigate whether this strategy can be validated by its application to methotrexate, a dual-acting small molecule that shows cytotoxicity because of its potent inhibitory activity against dihydrofolate reductase and that binds folic acid receptor, a tumor biomarker frequently upregulated on the cancer cell surface. This article describes a series of dendrimer conjugates derived from a generation 5 polyamidoamine (G5 PAMAM) presenting a multivalent array of methotrexate and also demonstrates their dual biological activities by surface plasmon resonance spectroscopy, a cell-free enzyme assay, and cell-based experiments with KB cancer cells.

Thioaptamer conjugated liposomes for tumor vasculature targeting

Recent developments in multi-functional nanoparticles offer a great potential for targeted delivery of therapeutic compounds and imaging contrast agents to specific cell types, in turn, enhancing therapeutic effect and minimizing side effects. Despite the promise, site specific delivery carriers have not been translated into clinical reality. In this study, we have developed long circulating liposomes with the outer surface decorated with thioated oligonucleotide aptamer (thioaptamer) against E-selectin (ESTA) and evaluated the targeting efficacy and PK parameters. In vitro targeting studies using Human Umbilical Cord Vein Endothelial Cell (HUVEC) demonstrated efficient and rapid uptake of the ESTA conjugated liposomes (ESTA-lip). In vivo, the intravenous administration of ESTA-lip resulted in their accumulation at the tumor vasculature of breast tumor xenografts without shortening the circulation half-life. The study presented here represents an exemplary use of thioaptamer for targeting and opens the door to testing various combinations of thioaptamer and nanocarriers that can be constructed to target multiple cancer types and tumor components for delivery of both therapeutics and imaging agents.

Targeting human clonogenic acute myelogenous leukemia cells via folate conjugated liposomes combined with receptor modulation by all-trans retinoic acid

Our previous data demonstrated that folate receptor β (FR-β) targeted liposomal doxorubicin (FT-L-DOX) showed enhanced cytotoxicity relative to non-targeted liposomal doxorubicin (CON-L-DOX), and the effect was enhanced by selective FR-β upregulation by all-trans retinoic acid (ATRA) in AML blast cells. In this study, the enhanced cytotoxicity was investigated in the proliferating human AML clonogenic cells by combining FT-L-DOX with ATRA. Also, pharmacokinetic properties by pretreatment of ATRA were evaluated using FR-targeted liposomal calcein (FT-L-Calcein). Pharmacokinetic study showed that the area under the concentration curve (AUC) of FT-L-Calcein was decreased and total clearance was increased by pretreatment with ATRA. Meanwhile, the volume of distribution was significantly increased by pretreatment of ATRA. Moreover, calcein level in the liver, spleen and kidney was increased following intravenous administration of FT-L-Calcein by pretreatment of ATRA. In vitro cytotoxicity of FT-L-DOX was higher than that of CON-L-DOX and was increased by pretreatment with ATRA. Colony formation in AML cells was lower due to treatment with FT-L-DOX compared with CON-L-DOX and colony formation further decreased upon pretreatment with ATRA. Moreover, FT-L-DOX was more toxic to AML clonogenic cells than to AML blast cells. The results demonstrate that the efficiency of FR-mediated targeting of FT-L-DOX was preferentially enhanced by ATRA induced FR-β upregulation in AML clonogenic cells.

Targeting nanoparticles to cancer

Nanotechnology applications in medicine, termed as nanomedicine, have introduced a number of nanoparticles of variable chemistry and architecture for cancer imaging and treatment. Nanotechnology involves engineering multifunctional devices with dimensions at the nanoscale, similar dimensions as those of large biological vesicles or molecules in our body. These devices typically have features just tens to hundred nanometers across and they can carry one or two detection signals and/or therapeutic cargo(s). One unique class of nanoparticles is designed to do both, providing this way the theragnostic nanoparticles (therapy and diagnosis). Being inspired by physiologically existing nanomachines, nanoparticles are designed to safely reach their target and specifically release their cargo at the site of the disease, this way increasing the drug's tissue bioavailability. Nanoparticles have the advantage of targeting cancer by simply being accumulated and entrapped in tumours (passive targeting). The phenomenon is called the enhanced permeation and retention effect, caused by leaky angiogenetic vessels and poor lymphatic drainage and has been used to explain why macromolecules and nanoparticles are found at higher ratios in tumours compared to normal tissues. Although accumulation in tumours is observed cell uptake and intracellular drug release have been questioned. Polyethyleneglycol (PEG) is used to protect the nanoparticles from the Reticulo-Endothelial System (RES), however, it prevents cell uptake and the required intracellular drug release. Grafting biorecognition molecules (ligands) onto the nanoparticles refers to active targeting and aims to increase specific cell uptake. Nanoparticles bearing these ligands are recognised by cell surface receptors and this leads to receptor-mediated endocytosis. Several materials are suggested for the design of nanoparticles for cancer. Polymers, linear and dendrimers, are associated with the drug in a covalent or non-covalent way and have been used with or without a targeting ligand. Stealth liposomes are suggested to carry the drug in the aqueous core, and they are usually decorated by recognition molecules, being widely studied and applied. Inorganic nanoparticles such as gold and iron oxide are usually coupled to the drug, PEG and the targeting ligand. It appears that the PEG coating and ligand decoration are common constituents in most types of nanoparticles for cancer. There are several examples of successful cancer diagnostic and therapeutic nanoparticles and many of them have rapidly moved to clinical trials. Nevertheless there is still a room for optimisation in the area of the nanoparticle kinetics such as improving their plasma circulation and tumour bioavailability and understanding the effect of targeting ligands on their efficiency to treat cancer. The need to develop novel and efficient ligands has never been greater, and the use of proper conjugation chemistry is mandatory.

Frontiers in cancer nanomedicine: directing mass transport through biological barriers

The physics of mass transport within body compartments and across biological barriers differentiates cancers from healthy tissues. Variants of nanoparticles can be manufactured in combinatorially large sets, varying by only one transport-affecting design parameter at a time. Nanoparticles can also be used as building blocks for systems that perform sequences of coordinated actions, in accordance with a prescribed logic. We refer to these as Logic-Embedded Vectors (LEVs). Nanoparticles and LEVs are ideal probes for the determination of mass transport laws in tumors, acting as imaging contrast enhancers, and can be employed for lesion-selective delivery of therapy. Their size, shape, density and surface chemistry dominate convective transport in the bloodstream, margination, cell adhesion, selective cellular uptake, as well as sub-cellular trafficking and localization. As argued here, the understanding of transport differentials in cancer, termed 'transport oncophysics', reveals a promising new frontier in oncology: the development of lesion-specific delivery particulates that exploit mass transport differentials to deploy treatment of greater efficacy and reduced side effects.

Understanding and re-engineering nucleoprotein machines to cure human disease

The mammalian nucleus is filled with self-organizing, nanometer-scale nucleoprotein machines that carry out DNA replication, RNA biogenesis and DNA repair. We discuss, as a model, the nonhomologous end-joining (NHEJ) machine, which repairs DNA double-strand breaks. The NHEJ machine consists of six core polypeptides and 10-20 ancillary polypeptides. A full understanding of its design principles will require measuring the behavior of single NHEJ complexes in living cells, using a Nano Toolbox that includes bright, stable, biocompatible fluorophores, efficient protein and nucleic acid-tagging strategies, and sensitive, high-resolution imaging methods. Taking inspiration from natural examples, it might be possible to adapt and redesign the NHEJ machine to precisely correct mutations responsible for common human diseases, such as K-ras in lung cancer or human papillomavirus E6 and E7 genes in cervical and oral cancers.

pH-responsive nanoparticles for cancer drug delivery

Solid tumors have an acidic extracellular environment and an altered pH gradient across their cell compartments. Nanoparticles responsive to the pH gradients are promising for cancer drug delivery. Such pH-responsive nanoparticles consist of a corona and a core, one or both of which respond to the external pH to change their soluble/insoluble or charge states. Nanoparticles whose coronas become positively charged or become soluble to make their targeting groups available for binding at the tumor extracellular pH have been developed for promoting cellular targeting and internalization. Nanoparticles whose cores become soluble or change their structures to release the carried drugs at the tumor extracellular pH or lysosomal pH have been developed for fast drug release into the extracellular fluid or cytosol. Such pH-responsive nanoparticles have therapeutic advantages over the conventional pH-insensitive counterparts.

Role of formulation composition in folate receptor-targeted liposomal doxorubicin delivery to acute myelogenous leukemia cells

Targeted drug delivery has the potential to improve the efficacy of a therapeutic agent while reducing its side effects. The folate receptor type beta (FR-beta) is a cell surface marker selectively expressed in the leukemic cells of approximately 70% of acute myeloid leukemia (AML) patients. Upregulation of FR-beta may also be selectively induced in AML cells by treatment with all-trans-retinoic acid (ATRA). In this study, the role of formulation composition in FR-targeted liposomal doxorubicin (DOX) delivery to AML cells was investigated. Liposomal formulations with a variable percentage of folate-polyethylene glycol distearoyl phosphatidylethanolamine (f-PEG-DSPE) were synthesized and evaluated for FR-beta-targeted DOX delivery in MV4-11 AML cells in vitro and for their pharmacokinetic properties in vivo. The formulation containing 0.5 mol % f-PEG-DSPE exhibited the highest efficiency of cellular uptake and in vitro cytotoxicity, as well as a long systemic circulation time in mice. In MV4-11 cells, the binding and cytotoxicity of FR-targeted liposomal DOX based on this formulation was also enhanced by ATRA-induced FR-beta upregulation.

Construction of anti-EGFR immunoliposomes via folate–folate binding protein affinity

A novel method for synthesis of anti-EGFR immunoliposomes using folate-folate binding protein (FBP) affinity is described. An anti-EGFR antibody (cetuximab or C225) was covalently linked to FBP via a thioether bond. Liposomes incorporating a lipophilic folate derivative (folate-PEG-cholesterol) were prepared by polycarbonate membrane extrusion. Anti-EGFR immunoliposomes were then obtained by combining FBP-C225 and folate-liposomes and evaluated for uptake and cytotoxicity in EGFR-overexpressing U87 human glioblastoma cells. Anti-EGFR immunoliposomes constructed via folate-FBP affinity exhibited excellent stability under physiological pH, and quickly released the bound FBP-C225 upon low pH (pH 3.5) treatment. Flow cytometry and fluorescence microscopy showed similar receptor-specific binding and internalization for both folate-FBP affinity-coupled and covalently coupled C225-immunoliposomes, but not for the non-targeted IgG-immunoliposomes. C225-immunoliposomes loaded with anticancer drug doxorubicin were more cytotoxic than non-targeted immunoliposomes in EGFR-overexpressing U87 glioma cells. Folate-FBP affinity is a potential method for construction of immunoliposomes and may have applications in synthesis of targeted drug carriers in general.

Synthesis of cetuximab-immunoliposomes via a cholesterol-based membrane anchor for targeting of EGFR

The objective of the present study was to construct epidermal growth factor receptor (EGFR) targeting cetuximab-immunoliposomes (ILs) for targeted delivery of boron compounds to EGFR(+) glioma cells for neutron capture therapy. The ILs were synthesized by using a novel cholesterol-based membrane anchor, maleimido-PEG-cholesterol (Mal-PEG-Chol), to incorporate cetuximab into liposomes by either surface conjugation or a post-insertion method. For post-insertion, the transfer efficiency of MAb conjugates from micelles to liposome was examined at varying temperatures, mPEG2000-DSPE ratios, and micelle-to-liposome lipid ratios. Following this, the cetuximab-ILs were evaluated for targeted delivery of the encapsulated boron anion, dodecahydro-closo-dodecaborate (2-) (B12H122-), to human EGFR gene transfected F98EGFR glioma cells as potential delivery agents for boron neutron capture therapy (BNCT). In addition, cellular uptake of cetuximab-ILs, encapsulating a fluorescence dye, was analyzed by confocal fluorescence microscopy and flow cytometry, and boron content was quantified by ICP-MS. Much greater ( approximately 8-fold) cellular uptake of boron was obtained using cetuximab-ILs in EGFR(+) F98EGFR compared with nontargeted human IgG-ILs. On the basis of these observations, we have concluded that cholesterol can serve as an effective anchor for MAb in liposomes, and cetuximab-ILs are potentially useful delivery vehicles for BNCT of gliomas.

Targeting transcription factors in cancer: Challenges and evolving strategies

As investigators uncover the molecular pathways leading to cancer, an abundance of potential molecular targets is accumulating. Among these targets, transcription factors are especially promising. This review discusses the reasons for focusing targeting efforts on transcription factors and highlights some salient examples. The advantages and problems with current methods for targeting are summarized. Finally, we discuss the drug delivery technologies in development that may one day make transcription factor targeting a therapeutic reality.: