Nuclear drug delivery to target tumour cells

Cu2WS4-PEG Nanozyme as Multifunctional Sensitizers for Enhancing Immuno-Radiotherapy by Inducing Ferroptosis

Unavoidable damage to normal tissues and tumor microenvironment (TME) resistance make it challenging to eradicate breast carcinoma through radiotherapy. Therefore, it is urgent to develop radiotherapy sensitizers that can effectively reduce radiation doses and reverse the suppressive TME. Here, a novel biomimetic PEGylated Cu2WS4 nanozyme (CWP) with multiple enzymatic activities is synthesized by the sacrificing template method to have physical radiosensitization and biocatalyzer-responsive effects on the TME. Experiment results show that CWP can improve the damage efficiency of radiotherapy on breast cancer cell 4T1 through its large X-ray attenuation coefficient of tungsten and nucleus-penetrating capacity. CWP also exhibit strong Fenton-like reactions that produced abundant ROS and GSH oxidase-like activity decreasing GSH. This destruction of redox balance further promotes the effectiveness of radiotherapy. Transcriptome sequencing reveals that CWP induced ferroptosis by regulating the KEAP1/NRF2/HMOX1/GPX4 molecules. Therefore, owing to its multiple enzymatic activities, high-atomic W elements, nucleus-penetrating, and ferroptosis-inducing capacities, CWP effectively improves the efficiency of radiotherapy for breast carcinoma in vitro and in vivo. Furthermore, CWP-mediated radiosensitization can trigger immunogenic cell death (ICD) to improve the anti-PD-L1 treatments to inhibit the growth of primary and distant tumors effectively. These results indicate that CWP is a multifunctional nano-sensitizers for radiotherapy and immunotherapy.

Targeting DNA topoisomerase IIα (TOP2A) in the hypoxic tumour microenvironment using unidirectional hypoxia-activated prodrugs (uHAPs)

The hypoxic tumour microenvironment (hTME), arising from inadequate and chaotic vascularity, can present a major obstacle for the treatment of solid tumours. Hypoxic tumour cells compromise responses to treatment since they can generate resistance to radiotherapy, chemotherapy and immunotherapy. The hTME impairs the delivery of a range of anti-cancer drugs, creates routes for metastasis and exerts selection pressures for aggressive phenotypes; these changes potentially occur within an immunosuppressed environment. Therapeutic strategies aimed at the hTME include targeting the molecular changes associated with hypoxia. An alternative approach is to exploit the prevailing lack of oxygen as a principle for the selective activation of prodrugs to target cellular components within the hTME. This review focuses on the design concepts and rationale for the use of unidirectional Hypoxia-Activated Prodrugs (uHAPs) to target the hTME as exemplified by the uHAPs AQ4N and OCT1002. These agents undergo irreversible reduction in a hypoxic environment to active forms that target DNA topoisomerase IIα (TOP2A). This nuclear enzyme is essential for cell division and is a recognised chemotherapeutic target. An activated uHAP interacts with the enzyme-DNA complex to induce DNA damage, cell cycle arrest and tumour cell death. uHAPs are designed to overcome the shortcomings of conventional HAPs and offer unique pharmacodynamic properties for effective targeting of TOP2A in the hTME. uHAP therapy in combination with standard of care treatments has the potential to enhance outcomes by co-addressing the therapeutic challenge presented by the hTME.

Harnessing the Immunogenic Potential of Gold Nanoparticle-Based Platforms as a Therapeutic Strategy in Breast Cancer Immunotherapy: A Mini Review

Breast cancer remains the most common malignancy among women worldwide. Although the implementation of mammography has dramatically increased the early detection rate, conventional treatments like chemotherapy, radiation therapy, and surgery, have significantly improved the prognosis for breast cancer patients. However, about a third of treated breast cancer patients are known to suffer from disease recurrences and progression to metastasis. Immunotherapy has recently gained traction due to its ability to establish long-term immune surveillance, and response for the prevention of disease recurrence and extension of patient survival. Current research findings have revealed that gold nanoparticles can enhance the safety and efficacy of cancer immunotherapy, through their unique intrinsic properties of good biocompatibility, durability, convenient surface modification, as well as enhanced permeability and retention effect. Gold nanoparticles are also able to induce innate immune responses through the process of immunogenic cell death, which can lead to the establishment of lasting adaptive immunity. As such gold nanoparticles are considered as good candidates for next generation immunotherapeutic strategies. This mini review gives an overview of gold nanoparticles and their potential applications in breast cancer immunotherapeutic strategies.

Aptamer Functionalized Upconversion Nanotheranostic Agent With Nuclear Targeting as the Highly Localized Drug-Delivery System of Doxorubicin

As a widely used anticancer drug, doxorubicin (DOX) could induce cell death mainly via interfering with DNA activity; thus, DOX could perform therapeutic effects mainly in the cell nucleus. However, most of the reported drug delivery systems lacked the well localization in the nucleus and released DOX molecules into the cytoplasm. Due to formidable barriers formed in the nuclear envelope, only around 1% of DOX could reach the nucleus and keep active. Therefore, DOX molecules were inevitably overloaded to achieve the desired therapeutic efficacy, which would induce serious side effects. Herein, we developed a highly localized drug nanocarrier for in situ release of DOX molecules to their action site where they could directly interfere with the DNA activity. In this work, we used cationic polymer-modified upconversion nanoparticles (UCNPs) as the luminescence core and gene carrier, while aptamers served as the DNA nanotrain to load DOX. Finally, the prepared nanotheranostic agent displayed good targetability, high cell apoptosis ratio (93.04%) with quite lower concentration than the LC50 of DOX, and obvious inhibition on tumor growth.

Surface-modified polymeric nanoparticles for drug delivery to cancer cells

INTRODUCTION

The utilization of polymeric nanoparticles, as drug payloads, has been extensively prevailed in cancer therapy. However, the precise distribution of these nanocarriers is restrained by various physiological and cellular obstacles. Nanoparticles must avoid nonspecific interactions with healthy cells and in vivo compartments to circumvent these barriers. Since in vivo interactions of nanoparticles are mainly dependent on surface properties of nanoparticles, efficient control on surface constituents is necessary for the determination of nanoparticles' fate in the body.

AREAS COVERED

In this review, the surface-modified polymeric nanoparticles and their utilization in cancer treatment were elaborated. First, the interaction of nanoparticles with numerous in vivo barriers was highlighted. Second, different strategies to overcome these obstacles were described. Third, some inspiring examples of surface-modified nanoparticles were presented. Later, fabrication and characterization methods of surface-modified nanoparticles were discussed. Finally, the applications of these nanoparticles in different routes of treatments were explored.

EXPERT OPINION

Surface modification of anticancer drug-loaded polymeric nanoparticles can enhance the efficacy, selective targeting, and biodistribution of the anticancer drug at the tumor site.

Internalized Functional DNA Aptamers as Alternative Cancer Therapies

Despite major advances, cancer remains one of the largest burdens of disease worldwide. One reason behind this is that killing tumor cells without affecting healthy surrounding tissue remains a largely elusive prospect, despite the widespread availability of cytotoxic chemotherapeutic agents. To meet these modern healthcare requirements, it is essential to develop precision therapeutics that minimise off-target side-effects for various cancer types. To this end, highly specific molecular targeting agents against cancer are of great interest. These agents may work by targeting intracellular signalling pathways following receptor binding, or via internalization and targeting to specific subcellular compartments. DNA aptamers represent a promising molecular tool in this arena that can be used for both specific cell surface targeting and subsequent internalization and can also elicit a functional effect upon internalization. This review examines various cancer targeting cell-internalizing aptamers, with a particular focus towards functional aptamers that do not require additional conjugation to nanoparticles or small molecules to elicit a biological response. With a deeper understanding and precise exploitation of cancer specific molecular pathways, functional intracellular DNA aptamers may be a powerful step towards more widespread development of precision therapeutics.

Design, synthesis, and biological evaluation of a multifunctional neuropeptide-Y conjugate for selective nuclear delivery of radiolanthanides

Background

Targeting G protein-coupled receptors on the surface of cancer cells with peptide ligands is a promising concept for the selective tumor delivery of therapeutically active cargos, including radiometals for targeted radionuclide therapy (TRT). Recently, the radiolanthanide terbium-161 (¹⁶¹Tb) gained significant interest for TRT application, since it decays with medium-energy β-radiation but also emits a significant amount of conversion and Auger electrons with short tissue penetration range. The therapeutic efficiency of radiometals emitting Auger electrons, like ¹⁶¹Tb, can therefore be highly boosted by an additional subcellular delivery into the nucleus, in order to facilitate maximum dose deposition to the DNA. In this study, we describe the design of a multifunctional, radiolabeled neuropeptide-Y (NPY) conjugate, to address radiolanthanides to the nucleus of cells naturally overexpressing the human Y₁ receptor (hY₁R).

By using solid-phase peptide synthesis, the hY₁R-preferring [F⁷,P³⁴]-NPY was modified with a fatty acid, a cathepsin B-cleavable linker, followed by a nuclear localization sequence (NLS), and a DOTA chelator (compound pb12). In this proof-of-concept study, labeling was performed with either native terbium-159 (^natTb), as surrogate for ¹⁶¹Tb, or with indium-111 (¹¹¹In).

Results

[^natTb]Tb-pb12 showed a preserved high binding affinity to endogenous hY₁R on MCF-7 cells and was able to induce receptor activation and internalization similar to the hY₁R-preferring [F⁷,P³⁴]-NPY. Specific internalization of the ¹¹¹In-labeled conjugate into MCF-7 cells was observed, and importantly, time-dependent nuclear uptake of ¹¹¹In was demonstrated. Study of metabolic stability showed that the peptide is insufficiently stable in human plasma. This was confirmed by injection of [¹¹¹In]In-pb12 in nude mice bearing MCF-7 xenograft which showed specific uptake only at very early time point.

Conclusion

The multifunctional NPY conjugate with a releasable DOTA-NLS unit represents a promising concept for enhanced TRT with Auger electron-emitting radiolanthanides. Our research is now focusing on improving the reported concept with respect to the poor plasmatic stability of this promising radiopeptide.

Polymer translocation through a hairy channel mimicking the inner plug of a nuclear pore complex

A microscopic transport model of a polymer translocating through a nuclear pore complex (NPC) is presented based on self-consistent field theory (SCFT), with the NPC and its nucleoporins mimicked by a hairy channel. Multiple cell environment effects (electrolyte effect, excluded volume effect, NPC drag effect, and hydrophobic effect) are all considered in this hairy channel model. The influence of various parameters (polymer chain length, length of NPC, strength of hydrophobic effect, and excluded volume effect) on translocation time is studied through theoretical analysis and numerical calculation. Numerical simulation results show that an area of low nucleoporin number density exists in the NPC, which facilitates the translocation of the polymer. The results also show that the translocation time curves with increasing NPC length and polymer charge number are concave. In addition, there are critical values for NPC length and polymer charge number for which the translocation time has a minimal value. The translocation time decreases with the increasing strength of the hydrophobic effect and excluded volume effect.

Dequalinium-based functional nanosomes show increased mitochondria targeting and anticancer effect

Mitochondria are targets with great potential for therapeutics for many human disorders. However, drug delivery systems for such therapeutics remain in need of more efficient mitochondrial-targeting carriers. In this study, we report that nanosomes composed of Dequalinium/DOTAP (1,2-dioleoyl-3-trimethylammonium-propane)/DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine), called DQA80s, can act in the dual role of mitochondrial-targeting carrier and anticancer agent for therapeutic interventions against mitochondrial diseases. In cytotoxicity assays, DQA80s were shown to be more toxic than DQAsomes. The DQA80s showed significantly increased cellular uptake as compared to that of DQAsomes, and DQA80s also showed more efficient escape from the endolysosome to the cytosol. We observed the efficient targeting of DQA80s to mitochondria in living cells using flow cytometry, confocal microscopy, and TEM imaging. We also found evidence of anticancer potential that mitochondrial-targeted DQA80s induced apoptosis by production of reactive oxygen species (ROS) via MAPK signaling pathways, loss of mitochondrial membrane potential, and the caspase-3 activation. The present study demonstrates that DQA80s have excellent dual potential both as a carrier and as an anticancer therapeutic for mitochondria-related disease therapy in vivo.

PTD4-apoptin induces Bcl-2-insensitive apoptosis in human cervical carcinoma in vitro and in vivo

Worldwide, cervix carcinoma is among the most dangerous cancer types, and novel therapies are under development. Cancer treatments are often hampered because of lack of specificity. The chicken anemia virus-derived apoptin induces apoptosis selectively in tumor cells and leaves normal cells unharmed. Here, we have carried out in-vitro and in-vivo studies on the cytotoxic effect of apoptin in a cervix carcinoma model. Apoptin was fused to the protein transduction domain 4 (PTD4), enabling delivery of the fusion protein across cellular membranes. PTD4-apoptin protein is located in the nuclei of human cervical carcinoma HeLa cells and in the cytoplasm of normal cells L02. By MTT and flow cytometry analysis, we have proven that PTD4-apoptin protein induced apoptosis in the cervical carcinoma cells. PTD4-apoptin enhanced the level of active executioner caspase-3. Neither caspase-3 activation nor apoptin-induced accumulation of the mitochondrial outer-membrane protein Mfn-2 was affected by ectopic Bcl-2 expression. In contrast, apoptin-mediated AKT activation was inhibited by Bcl-2. In vivo, cervix carcinoma xenografts were treated for 7 days with PTD4-apoptin protein. The PTD4-apoptin treatment induced a decrease in the cervix carcinoma, whereas the PTD4-GFP protein-treated controls expanded significantly. TUNEL analysis showed that PTD4-apoptin protein induced apoptosis in cervix carcinoma cells, in contrast to the control PTD-GFP-treated ones. Our results indicate that apoptin is a potential anticancer agent for treating cervix carcinoma.

Anti-cancer efficacy of biotinylated chitosan nanoparticles in liver cancer

The present study investigated the synthesis of biotinylated chitosan (Bio-CS) from chitosan using a nanomaterial skeleton with biotin and the successful targeting of the formulation in liver cancer cells. Bio-CS was validated by fourier transformed infrared spectroscopy and hydrogen^-1 nuclear magnetic resonance spectroscopy. Bio-CS and plasmid DNA were used to construct Bio-CS/plasmid DNA nanoparticles according to the optimal molar ratio of 1:1 and the optimal pH-value of 5.5. Under these conditions, the parameters mean particle size, potential, encapsulation rate and drug loading, were 82.9 nm, +21.8 mV, 85.7% and 35.4%, respectively. Bio-CS exhibited an apparent liver cancer targeting effect in vitro and in vivo, as demonstrated by confocal laser scanning, green fluorescent protein transfection, and in vivo imaging assays. In addition, the Bio-CS/plasmid DNA nanoparticles significantly increased the survival period of the orthotropic liver cancer mouse model compared with the plasmid DNA, with no apparent side effects on the cells. Bio-CS nanomaterials stimulated an immune response in hepatoma cells via increased expression of GM-CSF, IL-21 and Rae-1 markers. The data suggest that Bio-CS increased the inhibition of liver cancer cell proliferation in vitro and the activation of the cellular immunity in vivo.

Lipid rafts-mediated endocytosis and physiology-based cell membrane traffic models of doxorubicin liposomes

The clathrin-mediated endocytosis is likely a major mechanism of liposomes' internalization. A kinetic approach was used to assess the internalization mechanism of doxorubicin (Dox) loaded cationic liposomes and to establish physiology-based cell membrane traffic mathematic models. Lipid rafts-mediated endocytosis, including dynamin-dependent or -independent endocytosis of noncaveolar structure, was a dominant process. The mathematic models divided Dox loaded liposomes binding lipid rafts (B) into saturable binding (SB) and nonsaturable binding (NSB) followed by energy-driven endocytosis. The intracellular trafficking demonstrated early endosome-late endosome-lysosome or early/late endosome-cytoplasm-nucleus pathways. The three properties of liposome structures, i.e., cationic lipid, fusogenic lipid, and pegylation, were investigated to compare their contributions to cell membrane and intracellular traffic. The results revealed great contribution of cationic lipid DOTAP and fusogenic lipid DOPE to cell membrane binding and internalization. The valid Dox in the nuclei of HepG2 and A375 cells treated with cationic liposomes containing 40mol% of DOPE were 1.2-fold and 1.5-fold higher than that in the nuclei of HepG2 and A375 cells treated with liposomes containing 20mol% of DOPE, respectively, suggesting the dependence of cell type. This tendency was proportional to the increase of cell-associated total liposomal Dox. The mathematic models would be useful to predict intracellular trafficking of liposomal Dox.

Scintillating Nanoparticles as Energy Mediators for Enhanced Photodynamic Therapy

Achieving effective treatment of deep-seated tumors is a major challenge for traditional photodynamic therapy (PDT) due to difficulties in delivering light into the subsurface. Thanks to their great tissue penetration, X-rays hold the potential to become an ideal excitation source for activating photosensitizers (PS) that accumulate in deep tumor tissue. Recently, a wide variety of nanoparticles have been developed for this purpose. The nanoparticles are designed as carriers for loading various kinds of PSs and can facilitate the activation process by transferring energy harvested from X-ray irradiation to the loaded PS. In this review, we focus on recent developments of nanoscintillators with high energy transfer efficiency, their rational designs, as well as potential applications in next-generation PDT. Treatment of deep-seated tumors by using radioisotopes as an internal light source will also be discussed.

Delivery of cancer therapeutics to extracellular and intracellular targets: Determinants, barriers, challenges and opportunities

Advances in molecular medicine have led to identification of worthy cellular and molecular targets located in extracellular and intracellular compartments. Effectiveness of cancer therapeutics is limited in part by inadequate delivery and transport in tumor interstitium. Parts I and II of this report give an overview on the kinetic processes in delivering therapeutics to their intended targets, the transport barriers in tumor microenvironment and extracellular matrix (TME/ECM), and the experimental approaches to overcome such barriers. Part III discusses new concepts and findings concerning nanoparticle-biocorona complex, including the effects of TME/ECM. Part IV outlines the challenges in animal-to-human translation of cancer nanotherapeutics. Part V provides an overview of the background, current status, and the roles of TME/ECM in immune checkpoint inhibition therapy, the newest cancer treatment modality. Part VI outlines the development and use of multiscale computational modeling to capture the unavoidable tumor heterogeneities, the multiple nonlinear kinetic processes including interstitial and transvascular transport and interactions between cancer therapeutics and TME/ECM, in order to predict the in vivo tumor spatiokinetics of a therapeutic based on experimental in vitro biointerfacial interaction data. Part VII provides perspectives on translational research using quantitative systems pharmacology approaches.

Efficient Subcellular Targeting to the Cell Nucleus of Quantum Dots Densely Decorated with a Nuclear Localization Sequence Peptide

Organelle-targeted drug delivery can enhance the efficiency of the intracellularly acting drugs and reduce their toxicity. We generated core-shell type CdSe-ZnS quantum dots (QDs) densely decorated with NLS peptidic targeting residues using a 3-stage decoration approach and investigated their endocytosis and nuclear targeting efficiencies. The diameter of the generated QDs increased following the individual decoration stages (16.3, 18.9, and 21.9 nm), the ζ-potential became less negative (-33.2, -17.5, and -11.9 mV), and characteristic changes appeared in the FTIR spectra following decoration with the linker and NLS peptides. Quantitative analysis of the last decoration stage revealed that 37.9% and 33.2% of the alkyne-modified NLS groups that were added to the reaction mix became covalently attached or adsorbed to the QDs surface, respectively. These numbers correspond to 63.6 and 55.7 peptides conjugated or adsorbed to a single QD (the surface density of 42 and 37 conjugated and adsorbed peptides per 1000 nm(2) of the QDs surface), which is higher than in the majority of previous studies that reported decoration efficiencies of formulations intended for nuclear-targeted drug delivery. QDs decorated with NLS peptides undergo more efficient endocytosis, as compared to other investigated QDs formulations, and accumulated to a higher extent in the cell nucleus or in close vicinity to it (11.9%, 14.6%, and 56.1% of the QDs endocytosed by an average cell for the QD-COOH, QD-azide, and QD-NLS formulations, respectively). We conclude that dense decoration of QDs with NLS residues increased their endocytosis and led to their nuclear targeting (preferential accumulation in the cells nuclei or in close vicinity to them). The experimental system and research tools that were used in this study allow quantitative investigation of the mechanisms that govern the QDs nuclear targeting and their dependence on the formulation properties. These findings will contribute to the development of subcellularly targeted DDSs that will deliver specific drugs to the nuclei of the target cells and will enhance efficacy and reduce toxicity of these drugs.

Enhanced tumour cell nuclear targeting in a tumour progression model

BACKGROUND

There is an urgent need for new approaches to deliver bioactive molecules to cancer cells efficiently and specifically.

METHODS

Here we fuse the cancer cell nuclear targeting module of the Chicken Anaemia Virus Apoptin protein to the core histones H2B and H3 and utilise them in transfection, protein transduction and DNA binding assays.

RESULTS

We found subsequent nuclear accumulation of these proteins to be 2-3 fold higher in tumour compared to normal cells in transfected isogenic human osteosarcoma and breast tumour progression models. This represents the first demonstration of enhanced nuclear targeting by Apoptin in a tumour progression model, and its functionality in a heterologous protein context. Excitingly, we found that the innate transduction ability of histones could be exploited in combination with the Apoptin nuclear targeting module to effect an overall 13-fold higher delivery of protein to osteosarcoma cancer cell nuclei compared to their isogenic normal counterparts.

CONCLUSIONS

This is the first report of cancer-cell specificity by a cell penetrating protein, with important implications for the use of protein transduction as a vehicle for gene/drug delivery in the future, and in particular in the development of highly specific and effective anti-cancer agents.

Multifunctional non-viral gene vectors with enhanced stability, improved cellular and nuclear uptake capability, and increased transfection efficiency

We have developed a new multifunctional, non-viral gene delivery platform consisting of cationic poly(amine-co-ester) (PPMS) for DNA condensation, PEG shell for nanoparticle stabilization, poly(γ-glutamic acid) (γ-PGA) and mTAT (a cell-penetrating peptide) for accelerated cellular uptake, and a nuclear localization signal peptide (NLS) for enhanced intracellular transport of DNA to the nucleus. In vitro study showed that coating of the binary PPMS/DNA polyplex with γ-PGA promotes cellular uptake of the polyplex particles, particularly by γ-glutamyl transpeptidase (GGT)-positive cells through the GGT-mediated endocytosis pathway. Conjugating PEG to the γ-PGA led to the formation of a ternary PPMS/DNA/PGA-g-PEG polyplex with decreased positive charges on the surface of the polyplex particles and substantially higher stability in serum-containing aqueous medium. The cellular uptake rate was further improved by incorporating mTAT into the ternary polyplex system. Addition of the NLS peptide was designed to facilitate intracellular delivery of the plasmid to the nucleus--a rate-limiting step in the gene transfection process. As a result, compared with the binary PPMS/LucDNA polyplex, the new mTAT-quaternary PPMS/LucDNA/NLS/PGA-g-PEG-mTAT system exhibited reduced cytotoxicity, remarkably faster cellular uptake rate, and enhanced transport of DNA to the nucleus. All these advantageous functionalities contribute to the remarkable gene transfection efficiency of the mTAT-quaternary polyplex both in vitro and in vivo, which exceeds that of the binary polyplex and commercial Lipofectamine™ 2000/DNA lipoplex. The multifunctional mTAT-quaternary polyplex system with improved efficiency and reduced cytotoxicity represents a new type of promising non-viral vectors for the delivery of therapeutic genes to treat tumors.

Stepwise-acid-active multifunctional mesoporous silica nanoparticles for tumor-specific nucleus-targeted drug delivery

In this paper, a novel stepwise-acid-active multifunctional mesoporous silica nanoparticle (MSN-(SA)TAT&(DMA)K11) was developed as a drug carrier. The MSN-(SA)TAT&(DMA)K11 is able to reverse its surface charge from negative to positive in the mildly acidic tumor extracellular environment. Then, the fast endo/lysosomal escape and subsequent nucleus targeting as well as intranuclear drug release can be realized after cellular internalization. Because of the difference in acidity between the tumor extracellular environment and that of endo/lysosomes, this multifunctional MSN-(SA)TAT&(DMA)K11 exhibits a stepwise-acid-active drug delivery with a tumor-specific nucleus-targeted property.

Ultrasound-mediated drug delivery for cardiovascular disease

INTRODUCTION

Ultrasound (US) has been developed as both a valuable diagnostic tool and a potent promoter of beneficial tissue bioeffects for the treatment of cardiovascular disease. These effects can be mediated by mechanical oscillations of circulating microbubbles, or US contrast agents, which may also encapsulate and shield a therapeutic agent in the bloodstream. Oscillating microbubbles can create stresses directly on nearby tissue or induce fluid effects that effect drug penetration into vascular tissue, lyse thrombi or direct drugs to optimal locations for delivery.

AREAS COVERED

The present review summarizes investigations that have provided evidence for US-mediated drug delivery as a potent method to deliver therapeutics to diseased tissue for cardiovascular treatment. In particular, the focus will be on investigations of specific aspects relating to US-mediated drug delivery, such as delivery vehicles, drug transport routes, biochemical mechanisms and molecular targeting strategies.

EXPERT OPINION

These investigations have spurred continued research into alternative therapeutic applications, such as bioactive gas delivery and new US technologies. Successful implementation of US-mediated drug delivery has the potential to change the way many drugs are administered systemically, resulting in more effective and economical therapeutics, and less-invasive treatments.

Oral colon-specific therapeutic approaches toward treatment of inflammatory bowel disease

INTRODUCTION

Inflammatory bowel disease (IBD) is a chronic relapsing idiopathic disease. In clinical terms, most patients require lifelong medication associated with possible unpleasant adverse effects. Oral colon-specific drug delivery systems are designed to deliver therapeutic drugs to the inflamed colon to target pathophysiological manifestations of IBD. The aim is to maintain the drug with proper concentration in the inflamed colon, to enhance drug residence time and to minimize drug absorption by healthy tissues.

AREAS COVERED

This review addresses the main barriers for colon-specific drug delivery from organism, tissue and cell levels, respectively. It also summarizes novel colon-specific therapeutic strategies using microparticles and nanoparticles.

EXPERT OPINION

Oral colon-specific drug delivery represents a possible approach toward efficient treatment of IBD. As the environment of the gastrointestinal tract is harsh and intricate, this approach requires that drug carriers can respond to specific environmental factors of the inflamed colon, permitting stimulus-responsive release of loaded drugs to specific cells or even into specific organelles within cells.

Cancer therapy and vaccination

Cancer remains one of the leading causes of death worldwide, both in developed and in developing nations. It may affect people at all ages, even fetuses, but the risk for most varieties increases with age. Current therapeutic approaches which include surgery, chemotherapy and radiotherapy are associated with adverse side effects arising from lack of specificity for tumors. The goal of any therapeutic strategy is to impact on the target tumor cells with limited detrimental effect to normal cell function. Immunotherapy is cancer specific and can target the disease with minimal impact on normal tissues. Cancer vaccines are capable of generating an active tumor-specific immune response and serve as an ideal treatment due to their specificity for tumor cells and long lasting immunological memory that may safeguard against recurrences. Cancer vaccines are designed to either prevent (prophylactic) or treat established cancer (therapeutic). Identification of tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs) has led to increased efforts to develop vaccination strategies. Vaccines may be composed of whole cells or cell extracts, genetically modified tumor cells to express costimulatory molecules, dendritic cells (DCs) loaded with TAAs, immunization with soluble proteins or synthetic peptides, recombinant viruses or bacteria encoding tumor-associated antigens, and plasmid DNA encoding TSAs or TAAs in conjunction with appropriate immunomodulators. All of these antitumor vaccination approaches aim to induce specific immunological responses and localized to TAAs, destroying tumor cells alone and leaving the vast majority of other healthy cells of the body untouched.

Modeling of molecular interaction between apoptin, BCR-Abl and CrkL--an alternative approach to conventional rational drug design

In this study we have calculated a 3D structure of apoptin and through modeling and docking approaches, we show its interaction with Bcr-Abl oncoprotein and its downstream signaling components, following which we confirm some of the newly-found interactions by biochemical methods. Bcr-Abl oncoprotein is aberrantly expressed in chronic myelogenous leukaemia (CML). It has several distinct functional domains in addition to the Abl kinase domain. The SH3 and SH2 domains cooperatively play important roles in autoinhibiting its kinase activity. Adapter molecules such as Grb2 and CrkL interact with proline-rich region and activate multiple Bcr-Abl downstream signaling pathways that contribute to growth and survival. Therefore, the oncogenic effect of Bcr-Abl could be inhibited by the interaction of small molecules with these domains. Apoptin is a viral protein with well-documented cancer-selective cytotoxicity. Apoptin attributes such as SH2-like sequence similarity with CrkL SH2 domain, unique SH3 domain binding sequence, presence of proline-rich segments, and its nuclear affinity render the molecule capable of interaction with Bcr-Abl. Despite almost two decades of research, the mode of apoptin's action remains elusive because 3D structure of apoptin is unavailable. We performed in silico three-dimensional modeling of apoptin, molecular docking experiments between apoptin model and the known structure of Bcr-Abl, and the 3D structures of SH2 domains of CrkL and Bcr-Abl. We also biochemically validated some of the interactions that were first predicted in silico. This structure-property relationship of apoptin may help in unlocking its cancer-selective toxic properties. Moreover, such models will guide us in developing of a new class of potent apoptin-like molecules with greater selectivity and potency.

Delivery of nanomedicines to extracellular and intracellular compartments of a solid tumor

Advances in molecular medicines have led to identification of promising targets on cellular and molecular levels. These targets are located in extracellular and intracellular compartments. The latter include cytosol, nucleus, mitochondrion, Golgi apparatus and endoplasmic reticulum. This report gives an overview on the barriers to delivering nanomedicines to various target sites within a solid tumor, the experimental approaches to overcome such barriers, and the potential utility of nanotechnology.

Nuclear targeting dynamics of gold nanoclusters for enhanced therapy of HER2+ breast cancer

Recent advances in fluorescent metal nanoclusters have spurred tremendous interest in nanomedicine due to the ease of fabrication, excellent biocompatibility, and, more importantly, excellent wavelength-dependent tunability. Herein, we report our findings on fluorescent BSA-protected gold nanoclusters (AuNCs), ∼2 nm in size conjugated with Herceptin (AuNCs-Her), for specific targeting and nuclear localization in ErbB2 over-expressing breast cancer cells and tumor tissue as a novel fluorescent agent for simultaneous imaging and cancer therapy. More interestingly, we found that AuNCs-Her could escape the endolysosomal pathway and enter the nucleus of cancer cells to enhance the therapeutic efficacy of Herceptin. We elucidate the diffusion characteristics (diffusion time and number of diffusers) and concentration of the fluorescing clusters in the nucleus of live cells. Our findings also suggest that the nuclear localization effect of AuNCs-Her enhances the anticancer therapeutic efficacy of Herceptin as evidenced by the induction of DNA damage. This study not only discusses a new nanomaterial platform for nuclear delivery of drugs but also provides important insights on nuclear targeting for enhanced therapy.

Global enhancement of nuclear localization-dependent nuclear transport in transformed cells

Fundamental to eukaryotic cell function, nucleocytoplasmic transport can be regulated at many levels, including through modulation of the importin/exportin (Imp/Exp) nuclear transport machinery itself. Although Imps/Exps are overexpressed in a number of transformed cell lines and patient tumor tissues, the efficiency of nucleocytoplasmic transport in transformed cell types compared with nontransformed cells has not been investigated. Here we use quantitative live cell imaging of 3 isogenic nontransformed/transformed cell pairs to show that nuclear accumulation of nuclear localization signal (NLS)-containing proteins, but not their NLS-mutated derivatives, is increased up to 7-fold in MCF10CA1h human epithelial breast carcinoma cells and in simian virus 40 (SV40)-transformed fibroblasts of human and monkey origin, compared with their nontransformed counterparts. The basis for this appears to be a significantly faster rate of nuclear import in transformed cell types, as revealed by analysis using fluorescence recovery after photobleaching for the human MCF10A/MCF10CA1h cell pair. Nuclear accumulation of NLS/nuclear export signal-containing (shuttling) proteins was also enhanced in transformed cell types, experiments using the nuclear export inhibitor leptomycin B demonstrating that efficient Exp-1-mediated nuclear export was not impaired in transformed compared with nontransformed cells. Enhanced nuclear import and export efficiencies were found to correlate with 2- to 4-fold higher expression of specific Imps/Exps in transformed cells, as indicated by quantitative Western blot analysis, with ectopic expression of Imps able to enhance NLS nuclear accumulation levels up to 5-fold in nontransformed MCF10A cells. The findings indicate that transformed cells possess altered nuclear transport properties, most likely due to the overexpression of Imps/Exps. The findings have important implications for the development of tumor-specific drug nanocarriers in anticancer therapy.

The effect of environmental pH on polymeric transfection efficiency

Although polymers, polyplexes, and cells are exposed to various extracellular and intracellular pH environments during polyplex preparation and polymeric transfection, the impact of environmental pH on polymeric transfection has not yet been investigated. This study aims to understand the influence of environmental pH on polymeric transfection by modulating the pH of the transfection medium or the culture medium. Changes in the extracellular pH affected polymeric transfection by way of complex factors such as pH-induced changes in polymer characteristics (e.g., proton buffering capacity and ionization), polyplex characteristics (e.g., size, surface charge, and decomplexation), and cellular characteristics (e.g., cellular uptake, cell cycle phases, and intracellular pH environment). Notably, acidic medium delayed endocytosis, endosomal acidification, cytosolic release, and decomplexation of polyplexes, thereby negatively affecting gene expression. However, acidic medium inhibited mitosis and reduced dilution of gene expression, resulting in increased transfection efficiency. Compared to pH 7.4 medium, acidic transfection medium reduced gene expression 1.6-7.7-fold whereas acidic culture medium enhanced transfection efficiency 2.1-2.6-fold. Polymeric transfection was affected more by the culture medium than by the transfection medium. Understanding the effects of extracellular pH during polymeric transfection may stimulate new strategies for determining effective and safe polymeric gene carriers.

Gold nanoparticles in cancer therapy

The rapid advancement of nanotechnology in recent years has fuelled a burgeoning interest in the field of nanoparticle research, in particular, its application in the medical arena. A constantly expanding knowledge based on a better understanding of the properties of gold nanoparticles (AuNPs) coupled with relentless experimentation means that the frontiers of nanotechnology are constantly being challenged. At present, there seems to be heightened interest in the application of AuNPs to the management of cancer, encompassing diagnosis, monitoring and treatment of the disease. These efforts are undertaken in the hope of revolutionizing current methods of treatment and treatment strategies for a multifactorial disease such as cancer. This review will focus on the current applications of AuNPs in cancer management.

Targeted photodynamic therapy--a promising strategy of tumor treatment

Targeted therapy is a new promising therapeutic strategy, created to overcome growing problems of contemporary medicine, such as drug toxicity and drug resistance. An emerging modality of this approach is targeted photodynamic therapy (TPDT) with the main aim of improving delivery of photosensitizer to cancer tissue and at the same time enhancing specificity and efficiency of PDT. Depending on the mechanism of targeting, we can divide the strategies of TPDT into "passive", "active" and "activatable", where in the latter case the photosensitizer is activated only in the target tissue. In this review, contemporary strategies of TPDT are described, including new innovative concepts, such as targeting assisted by peptides and aptamers, multifunctional nanoplatforms with navigation by magnetic field or "photodynamic molecular beacons" activatable by enzymes and nucleic acid. The imperative of introducing a new paradigm of PDT, focused on the concepts of heterogeneity and dynamic state of tumor, is also called for.

Enhancement of vinorelbine-induced cytotoxicity and apoptosis by clomipramine and lithium chloride in human neuroblastoma cancer cell line SH-SY5Y

The aim of this work is to investigate whether clomipramine (CIM) and lithium chloride (LiCl) potentiate the cytotoxicity of vinorelbine (VNR) on SH-SY5Y human neuroblastoma cells in vitro and whether midkine (MK) can be a resistance factor for these treatments. Four groups of experiments were performed for 96 h using both monolayer and spheroid cultures of SH-SY5Y cells: (1) control group, (2) singly applied VNR, CIM, and LiCl, (3) VNR with CIM, and (4) VNR with LiCl. Their effects on monolayer and spheroid cultures were determined by evaluating cell proliferation, bromodeoxyuridine labeling index (BrdU-LI), apoptosis, cyclic adenosine monophosphate (cAMP) and midkine levels, colony-forming efficiency, spheroid size, and ultrastructure. In comparison with the control group, single and combination drug treatments significantly reduced the proliferation index (PI) for 96 h. The most potent reduction of PI was observed with VNR in combination with CIM and LiCl for all time intervals. VNR with CIM and LiCl seemed to be ineffective in reducing BrdU-LI of both monolayer cell and spheroid cultures, spheroid size, and cAMP level. VNR with LiCl increased apoptosis at 24 h, however VNR with CIM increased apoptosis at 96 h. VNR was the most potent drug in inhibiting colony-forming efficiency. The combination of VNR with CIM was the most potent in reducing midkine levels among all groups. Interestingly, the combination of VNR with LiCl led to both nuclear membrane breakdown and disappearance of the cellular membranes inside the spheroids. Both CIM and LiCl seemed to potentiate VNR-induced cytotoxicity, and MK was not a resistance factor for VNR, LiCl, and CIM.