Targeting liposomal chemotherapy via both tumor cell-specific and tumor vasculature-specific ligands potentiates therapeutic efficacy

Tumor-Homing and Penetrating Peptide-Functionalized Photosensitizer-Conjugated PEG-PLA Nanoparticles for Chemo-Photodynamic Combination Therapy of Drug-Resistant Cancer

The combination of photodynamic therapy (PDT) and chemotherapy holds great potential in combating drug-resistant cancers. However, the major challenge that lies ahead is how to achieve high coloading capacity for both photosensitizer and chemo-drugs and how to gain efficient delivery of drugs to the drug-resistant tumors. In this study, we prepared a nanovehicle for codelivery of photosensitizer (pyropheophorbide-a, PPa) and chemo-drugs (paclitaxel, PTX) based on the synthesis of PPa-conjugated amphiphilic copolymer PPa-PLA-PEG-PLA-PPa. The obtained nanoparticles (PP NP) exhibited a satisfactory high drug-loading capacity for both drugs. To achieve effective tumor-targeting therapy, the surface of PP NP was decorated with a tumor-homing and penetrating peptide F3. In vitro cellular experiments showed that F3-functionalized PP NP (F3-PP NP) exhibited higher cellular association than PP NP and resulted in the strongest antiproliferation effect. In addition, compared with the unmodified nanoparticles, F3-PP NP exhibited a more preferential enrichment at the tumor site. Pharmacodynamics evaluation in vivo demonstrated that a longer survival time was achieved by the tumor-bearing mice treated with PP NP (+laser) than those treated with chemotherapy only or PDT only. Such antitumor efficacy of combination therapy was further improved following the F3 peptide functionalization. Collectively, these results suggested that targeted combination therapy may pave a promising way for the therapy of drug-resistant tumor.

Therapeutic application of anti-angiogenic nanomaterials in cancers

Angiogenesis, the formation of new blood vessels from pre-existing vasculature, plays a vital role in physiological and pathological processes (embryonic development, wound healing, tumor growth and metastasis). The overall balance of angiogenesis inside the human body is maintained by pro- and anti-angiogenic signals. The processes by which drugs inhibit angiogenesis as well as tumor growth are called the anti-angiogenesis technique, a most promising cancer treatment strategy. Over the last couple of decades, scientists have been developing angiogenesis inhibitors for the treatment of cancers. However, conventional anti-angiogenic therapy has several limitations including drug resistance that can create problems for a successful therapeutic strategy. Therefore, a new comprehensive treatment strategy using antiangiogenic agents for the treatment of cancer is urgently needed. Recently researchers have been developing and designing several nanoparticles that show anti-angiogenic properties. These nanomedicines could be useful as an alternative strategy for the treatment of various cancers using anti-angiogenic therapy. In this review article, we critically focus on the potential application of anti-angiogenic nanomaterial and nanoparticle based drug/siRNA/peptide delivery systems in cancer therapeutics. We also discuss the basic and clinical perspectives of anti-angiogenesis therapy, highlighting its importance in tumor angiogenesis, current status and future prospects and challenges.

Lipid-Based Drug Delivery Systems in Cancer Therapy: What Is Available and What Is Yet to Come

Cancer is a leading cause of death in many countries around the world. However, the efficacy of current standard treatments for a variety of cancers is suboptimal. First, most cancer treatments lack specificity, meaning that these treatments affect both cancer cells and their normal counterparts. Second, many anticancer agents are highly toxic, and thus, limit their use in treatment. Third, a number of cytotoxic chemotherapeutics are highly hydrophobic, which limits their utility in cancer therapy. Finally, many chemotherapeutic agents exhibit short half-lives that curtail their efficacy. As a result of these deficiencies, many current treatments lead to side effects, noncompliance, and patient inconvenience due to difficulties in administration. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems known commonly as nanoparticles. Among these delivery systems, lipid-based nanoparticles, particularly liposomes, have shown to be quite effective at exhibiting the ability to: 1) improve the selectivity of cancer chemotherapeutic agents; 2) lower the cytotoxicity of anticancer drugs to normal tissues, and thus, reduce their toxic side effects; 3) increase the solubility of hydrophobic drugs; and 4) offer a prolonged and controlled release of agents. This review will discuss the current state of lipid-based nanoparticle research, including the development of liposomes for cancer therapy, different strategies for tumor targeting, liposomal formulation of various anticancer drugs that are commercially available, recent progress in liposome technology for the treatment of cancer, and the next generation of lipid-based nanoparticles.

In Vitro and Ex Vivo Evaluations of Lipid Anti-Cancer Nanoformulations: Insights and Assessment of Bioavailability Enhancement

Lipid-based nanoformulations have been extensively investigated for improving oral efficacy of plethora of drugs. Chemotherapeutic agents remain a preferred option for effective management of cancer; however, most chemotherapeutic agents suffer from limitation of poor oral bioavailability that is associated with their physicochemical properties. Drug delivery via lipid-based nanosystems possesses strong rational and potential for improving oral bioavailability of such anti-cancer molecules through various mechanisms, viz. improving their gut solubilisation owing to micellization, improving mucosal permeation, improving lymphatic uptake, inhibiting intestinal metabolism and/or inhibiting P-glycoprotein efflux of molecules in the gastrointestinal tract. Various in vitro characterization techniques have been reported in literature that aid in getting insights into mechanisms of lipid-based nanodevices in improving oral efficacy of anti-cancer drugs. The review focuses on different characterization techniques that can be employed for evaluation of lipid-based nanosystems and their role in effective anti-cancer drug delivery.

Improved drug delivery and therapeutic efficacy of PEgylated liposomal doxorubicin by targeting anti-HER2 peptide in murine breast tumor model

Targeted cancer therapy is a powerful therapeutic strategy to management of cancer. HER2 as an anticancer target has long been studied. Its overexpression plays an important role in the pathogenesis and progressiveness of breast and other cancers. To establish efficient and reliable drug delivery to HER2-overexpressing cells, the authors of this study have developed anti-HER2 (ErbB2) peptide-liposomal formulations of doxorubicin (DOX) by an engineered breast tumor-targeting peptide ligand, AHNP, Anti-HER2/neu peptide, (FCDGFYACYADV) with three glycine amino acids as spacer before its original sequencing. Towards this goal, PEGylated liposome doxorubicin (PLD) bearing different ligand densities of AHNP was prepared and characterized for their size, zeta potential and peptide conjugation. The AHNP functionalization and density effects on breast tumor cell uptake, selective cytotoxicity, prevention of tumor growth and the tissue biodistribution of encapsulated DOX were studied in mice bearing TUBO breast cancer tumor model. The findings demonstrated that increasing the ligand density of AHNP increases cytotoxicity and cell-uptake in SKBR3 and TUBO cells which overexpress HER2 but not in MDA-MB-231with low HER2 expression profile. The anticancer activity was also superior for targeted liposomal DOX with more AHNP densities. Overall, the results showed that optimum AHNP density functionalization of PLD can significantly improve selectivity and the therapeutic index of liposomal DOX in the treatment of HER2 positive breast cancer and merits further investigation.

Multi-targeting Peptide-Functionalized Nanoparticles Recognized Vasculogenic Mimicry, Tumor Neovasculature, and Glioma Cells for Enhanced Anti-glioma Therapy

Chemotherapy failure of glioma, the most aggressive and devastating cancer, might be ascribed to the physiologic barriers of the tumor mainly including heterogeneous tumor perfusion and vascular permeability, which result in a limited penetration of chemotherapeutics. Besides, the vasculogenic mimicry (VM) channels, which are highly resistant to anti-angiogenic therapy and serve as a complement of angiogenesis, were abound in glioma and always associated with tumor recurrence. In order to enhance the therapy effect of anti-glioma, we developed a PEG-PLA-based nanodrug delivery system (nanoparticles, NP) in this study and modified its surface with CK peptide, which was composed of a human sonic hedgehog (SHH) targeting peptide (CVNHPAFAC) and a KDR targeting peptide (K237) through a GYG linker, for facilitating efficient VM channels, tumor neovasculature, and glioma cells multi-targeting delivery of paclitaxel. In vitro cellular assay showed that CK-NP-PTX not only exhibited the strongest antiproliferation effect on U87MG cells and HUVEC cells but also resulted in the most efficient destruction of VM channels when compared with CVNHPAFAC-NP, K237-NP, and the unmodified ones. Besides, CK-NP accumulated more selectively at the glioma site as demonstrated by in vivo and ex vivo imaging. As expected, the glioma-bearing mice treated with CK-NP-PTX achieved the longest median survival time compared to those treated with CVNHPAFAC-NP-PTX and K237-NP-PTX. These findings indicated that the multi-targeting therapy mediated by CK peptide might provide a promising way for glioblastoma therapy.

Generation of new peptide-Fc fusion proteins that mediate antibody-dependent cellular cytotoxicity against different types of cancer cells

Antibody-dependent cellular cytotoxicity (ADCC), a key effector function for the clinical effectiveness of monoclonal antibodies, is triggered by the engagement of the antibody Fc domain with the Fcγ receptors expressed by innate immune cells such as natural killer (NK) cells and macrophages. Here, we fused cancer cell-binding peptides to the Fc domain of human IgG1 to engineer novel peptide-Fc fusion proteins with ADCC activity. The designed fusion proteins were expressed in human embryonic kidney 293T cells, followed by purification and characterization by western blots. One of the engineered variants (WN-Fc), bound with high affinity to a wide range of solid tumor cell lines (e.g., colon, lung, prostate, skin, ovarian, and mammary tumors). Treatment of cancer cells with the engineered peptide-Fc fusions in the presence of effector NK cells potentially enhanced cytotoxicity, degranulation, and interferon-γ production by NK cells when compared to cells treated with the Fc control. The presence of competing peptides inhibited NK cell activation. Furthermore, a bispecific peptide-Fc fusion protein activated NK cells against HER-1- and/or HER-2-expressing cancer cells. Collectively, the engineered peptide-Fc fusions constitute a new promising strategy to recruit and activate NK cells against tumor cells, a primary goal of cancer immunotherapy.

Neuroblastoma-targeted nanocarriers improve drug delivery and penetration, delay tumor growth and abrogate metastatic diffusion

Selective tumor targeting is expected to enhance drug delivery and to decrease toxicity, resulting in an improved therapeutic index. We have recently identified the HSYWLRS peptide sequence as a specific ligand for aggressive neuroblastoma, a childhood tumor mostly refractory to current therapies. Here we validated the specific binding of HSYWLRS to neuroblastoma cell suspensions obtained either from cell lines, animal models, or Schwannian-stroma poor, stage IV neuroblastoma patients. Binding of the biotinylated peptide and of HSYWLRS-functionalized fluorescent quantum dots or liposomal nanoparticles was dose-dependent and inhibited by an excess of free peptide. In animal models obtained by the orthotopic implant of either MYCN-amplified or MYCN single copy human neuroblastoma cell lines, treatment with HSYWLRS-targeted, doxorubicin-loaded Stealth Liposomes increased tumor vascular permeability and perfusion, enhancing tumor penetration of the drug. This formulation proved to exert a potent antitumor efficacy, as evaluated by bioluminescence imaging and micro-PET, leading to (i) delay of tumor growth paralleled by decreased tumor glucose consumption, and (ii) abrogation of metastatic spreading, accompanied by absence of systemic toxicity and significant increase in the animal life span. Our findings are functional to the design of targeted nanocarriers with potentiated therapeutic efficacy towards the clinical translation.

Examples of Tumor Growth Inhibition Properties of Liposomal Formulations of pH-Sensitive Histidinylated Cationic Amphiphiles

Herein we report on the unexpected cancer cell selective cytotoxicities of the liposomal formulations of aspartic and glutamic acid backbone-based four novel lipids with endosomal pH-sensitive head-groups and aliphatic n-hexadecyl & n-octadecyl hydrophobic tails. Surprisingly, although the formulations killed cancer cells efficiently, they were significantly less cytotoxic in non-cancerous healthy cells. Importantly, intratumoral administration of the liposomal formulations efficiently inhibited growth of melanoma in a syngeneic C57BL/6J mouse tumor model. Western Blotting experiments with the lysates of liposomes treated cancer cells revealed that liposomes of lipids 1-4 induce apoptosis selectively in cancer cells presumably by releasing cytochrome c from depolarized mitochondria and subsequent activation of caspases 3 & 9, upregulation of Bax and down regulation of Bcl-2. In summary, the present report describes for the first time tumor growth inhibition properties of the liposomal formulations of endosomal pH-sensitive histidinylated cationic lipids under both in vitro and systemic settings.

Enhanced delivery of liposomes to lung tumor through targeting interleukin-4 receptor on both tumor cells and tumor endothelial cells

A growing body of evidence suggests that pathological lesions express tissue-specific molecular targets or biomarkers within the tissue. Interleukin-4 receptor (IL-4R) is overexpressed in many types of cancer cells, including lung cancer. Here we investigated the properties of IL-4R-binding peptide-1 (IL4RPep-1), a CRKRLDRNC peptide, and its ability to target the delivery of liposomes to lung tumor. IL4RPep-1 preferentially bound to H226 lung tumor cells which express higher levers of IL-4R compared to H460 lung tumor cells which express less IL-4R. Mutational analysis revealed that C1, R2, and R4 residues of IL4RPep-1 were the key binding determinants. IL4RPep-1-labeled liposomes containing doxorubicin were more efficiently internalized in H226 cells and effectively delivered doxorubicin into the cells compared to unlabeled liposomes. In vivo fluorescence imaging of nude mice subcutaneously xenotransplanted with H226 tumor cells indicated that IL4RPep-1-labeled liposomes accumulate more efficiently in the tumor and inhibit tumor growth more effectively compared to unlabeled liposomes. Interestingly, expression of IL-4R was high in vascular endothelial cells of tumor, while little was detected in vascular endothelial cells of control organs including the liver. IL-4R expression in cultured human vascular endothelial cells was also up-regulated when activated by a pro-inflammatory cytokine tumor necrosis factor-α. Moreover, the up-regulation of IL-4R expression was observed in primary human lung cancer tissues. These results indicate that IL-4R-targeting nanocarriers may be a useful strategy to enhance drug delivery through the recognition of IL-4R in both tumor cells and tumor endothelial cells.

Single peptide ligand-functionalized uniform hollow mesoporous silica nanoparticles achieving dual-targeting drug delivery to tumor cells and angiogenic blood vessel cells

BACKGROUND

The purpose of this study was to construct hollow mesoporous silica nanoparticles (HMSN) decorated with tLyp-1 peptide (tHMSN) for dual-targeting drug delivery to tumor cells and angiogenic blood vessel cells.

METHODS

HMSN were synthesized de novo using a novel cationic surfactant-assisted selective etching strategy and were then modified with tLyp-1. Multiple methods, including transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, bicinchoninic acid assay, and nitrogen adsorption and desorption isotherms, were used to characterize the tHMSN. Doxorubicin were chosen as the model cargo, and the uptake of doxorubicin-loaded tHMSN into MDA-MB-231 cells and human umbilical vein endothelial cells (HUVECs), as models of tumor cells and tumor neovascular endothelial cells, respectively, were observed and detected by confocal laser scanning microscopy and flow cytometry. An in vitro pharmacodynamic study and a study of the mechanism via which the nanoparticles were endocytosed were also performed.

RESULTS

HMSN with a highly uniform size and well oriented mesopores were synthesized. After tHMSN were characterized, enhanced uptake of the cargo carried by tHMSN into MDA-MB-231 cells and HUVECs compared with that of their unmodified counterparts was validated by confocal laser scanning microscopy and flow cytometry at the qualitative and quantitative levels, respectively. Further, the pharmacodynamic study suggested that, compared with their unmodified counterparts, doxorubicin-loaded tHMSN had an enhanced inhibitory effect on MDA-MB-231 cells and HUVECs in vitro. Finally, a preliminary study on the mechanism by which the nanoparticles were endocytosed indicated that the clathrin-mediated endocytosis pathway has a primary role in the transport of tHMSN into the cytoplasm.

CONCLUSION

tHMSN might serve as an effective active targeting nanocarrier strategy for anti-mammary cancer drug delivery.

Development of cyclic NGR peptides with thioether linkage: structure and dynamics determining deamidation and bioactivity

NGR peptides that recognize CD13 receptors in tumor neovasculature are of high interest, in particular due to their potential applications in drug targeting. Here we report the synthesis and structural analysis of novel thioether bond-linked cyclic NGR peptides. Our results show that their chemostability (resistance against spontaneous decomposition forming isoAsp and Asp derivatives) strongly depends on both sample handling conditions and structural properties. A significant correlation was found between chemostability and structural measures, such as NH(Gly)-CO(Asn-sc) distances. The side-chain orientation of Asn is a key determining factor; if it is turned away from HN(Gly), the chemostability increases. Structure stabilizing factors (e.g., H-bonds) lower their internal dynamics, and thus biomolecules become even more resistant against spontaneous decomposition. The effect of cyclic NGR peptides on cell adhesion was examined in A2058 melanoma cell lines. It was found that some of the investigated peptides gradually increased cell adhesion with long-term characteristics, indicating time-dependent formation of integrin binding isoAsp derivatives that are responsible for the adhesion-inducing effect.

Polymeric nanoparticles for targeted treatment in oncology: current insights

Chemotherapy, a major strategy for cancer treatment, lacks the specificity to localize the cancer therapeutics in the tumor site, thereby affecting normal healthy tissues and advocating toxic adverse effects. Nanotechnological intervention has greatly revolutionized the therapy of cancer by surmounting the current limitations in conventional chemotherapy, which include undesirable biodistribution, cancer cell drug resistance, and severe systemic side effects. Nanoparticles (NPs) achieve preferential accumulation in the tumor site by virtue of their passive and ligand-based targeting mechanisms. Polymer-based nanomedicine, an arena that entails the use of polymeric NPs, polymer micelles, dendrimers, polymersomes, polyplexes, polymer–lipid hybrid systems, and polymer–drug/protein conjugates for improvement in efficacy of cancer therapeutics, has been widely explored. The broad scope for chemically modifying the polymer into desired construct makes it a versatile delivery system. Several polymer-based therapeutic NPs have been approved for clinical use. This review provides an insight into the advances in polymer-based targeted nanocarriers with focus on therapeutic aspects in the field of oncology.

Advances in an active and passive targeting to tumor and adipose tissues

INTRODUCTION

Data reported during the last decade of the twentieth century indicate that passive targeting is an efficient strategy for delivering nanocarrier systems to tumor tissues. The focus of this review is on active targeting as a next-generation strategy for extending the capacity of a drug delivery system (DDS).

AREAS COVERED

Tumor vasculature targeting was achieved using arginine- glycine-aspartic acid, asparagine-glycine-arginine and other peptides, which are well-known peptides, as ligand against tumor vasculature. An efficient system for delivering small interfering RNA to the tumor vasculature involved the use of a multifunctional envelope-type nanodevice based on a pH-modified cationic lipid and targeting ligands. The active-targeting system was extended from tumor delivery to adipose tissue delivery, where endothelial cells are tightly linked and are impermeable to nanocarriers. In mice, prohibitin-targeted nanoparticles can be used to successfully deliver macromolecules to induce anti-obese effects. Finally, the successful delivery of nanocarriers to adipose tissue in obese mice via the enhanced permeability and retention-effect is reported, which can be achieved in tumor tissue.

EXPERT OPINION

Unlike tumor tissues, only a few reports have appeared on how liposomal carriers accumulate in adipose tissues after systemic injection. This finding, as well as active targeting to the adipose vasculature, promises to extend the capacity of DDS to adipose tissue. Since the site of action of nucleic acids is the cytosol, the intracellular trafficking of carriers and their cargoes as well as cellular uptake must be taken into consideration.

A validated mathematical model of tumor growth including tumor-host interaction, cell-mediated immune response and chemotherapy

We consider a dynamical model of cancer growth including three interacting cell populations of tumor cells, healthy host cells and immune effector cells. The tumor-immune and the tumor-host interactions are characterized to reproduce experimental results. A thorough dynamical analysis of the model is carried out, showing its capability to explain theoretical and empirical knowledge about tumor development. A chemotherapy treatment reproducing different experiments is also introduced. We believe that this simple model can serve as a foundation for the development of more complicated and specific cancer models.

Monoclonal antibody-targeted, temperature-sensitive liposomes: in vivo tumor chemotherapeutics in combination with mild hyperthermia

The development of actively targeted, responsive delivery vectors holds great promise for cancer therapy. Here, we investigated whether enhanced therapeutic activity of temperature sensitive liposomes (TSL) could be obtained by mild hyperthermia-triggered release of the chemotherapeutic drug doxorubicin (DOX) after hCTMO1 monoclonal antibody (anti-MUC-1) binding and uptake into cancer cells. We showed that traditional TSL (TTSL) liposome systems maintained their physicochemical and thermal properties after conjugation to hCTMO1 full IgG. Receptor-mediated cellular uptake and cytotoxic efficacy of antibody-targeted TTSL (TTSL-Ab) were investigated using 2D and 3D cell culture models. Significant enhancement in cellular uptake and cytotoxic activity after 1h of heating at 42 °C was observed for TTSL-Ab compared to non-targeted liposomes in MUC-1 over-expressing breast cancer cells (MDA-MB-435). Tissue distribution and in vivo therapeutic activity were studied using different heating protocols to explore the effect of mild hyperthermia on the tumor accumulation of targeted TTSL and their therapeutic effect. Application of local, mild hyperthermia (42°C) significantly increased the tumor accumulation of targeted TSL compared to non-targeted liposomes, associated with a moderate improvement in therapeutic activity and survival.

The chicken chorioallantoic membrane model in biology, medicine and bioengineering

The chicken chorioallantoic membrane (CAM) is a simple, highly vascularized extraembryonic membrane, which performs multiple functions during embryonic development, including but not restricted to gas exchange. Over the last two decades, interest in the CAM as a robust experimental platform to study blood vessels has been shared by specialists working in bioengineering, development, morphology, biochemistry, transplant biology, cancer research and drug development. The tissue composition and accessibility of the CAM for experimental manipulation, makes it an attractive preclinical in vivo model for drug screening and/or for studies of vascular growth. In this article we provide a detailed review of the use of the CAM to study vascular biology and response of blood vessels to a variety of agonists. We also present distinct cultivation protocols discussing their advantages and limitations and provide a summarized update on the use of the CAM in vascular imaging, drug delivery, pharmacokinetics and toxicology.

Crosslinking liposomes/cells using cholesteryl group-modified tilapia gelatin

Cholesteryl group-modified tilapia gelatins (Chol-T-Gltns) with various Chol contents from 3 to 69 mol % per amino group of Gltn were prepared for the assembly of liposomes and cells. Liposomes were physically crosslinked by anchoring Chol groups of Chol-T-Gltns into lipid membranes. The resulting liposome gels were enzymatically degraded by addition of collagenase. Liposome gels prepared using Chol-T-Gltn with high Chol content (69Chol-T-Gltn) showed slower enzymatic degradation when compared with gels prepared using Chol-T-Gltn with low Chol content (3Chol-T-Gltn). The hepatocyte cell line HepG2 showed good assembly properties and no cytotoxic effects after addition of 69Chol-T-Gltns. In addition, the number of HepG2 cells increased with concentration of 69Chol-T-Gltns. Therefore, Chol-T-Gltn, particularly, 69Chol-T-Gltn, can be used as an assembling material for liposomes and various cell types. The resulting organization can be applied to various biomedical fields, such as drug delivery systems, tissue engineering and regenerative medicine.

sTRAIL coupled to liposomes improves its pharmacokinetic profile and overcomes neuroblastoma tumour resistance in combination with Bortezomib

Neuroblastoma (NB), the most common and deadly extracranial solid tumour of childhood, represents a challenging in paediatric oncology. Soluble tumour necrosis factor (TNF)-related apoptosis-inducing ligand (sTRAIL) is a cancer cell-specific molecule exerting remarkable anti-tumour activities against paediatric malignancies both in vitro and in preclinical settings. However, due to its too fast elimination and to the undesired related side effects, the improvement of sTRAIL in vivo bioavailability and the specific delivery to the tumour is mandatory for increasing its therapeutic efficacy. In this manuscript, we developed an innovative pegylated liposomal formulation carrying the sTRAIL at the outer surface (sTRAIL-SL) with the intent to improve its serum half-life and increase its efficacy in vivo, while reducing side effects. Furthermore, the possibility to combine sTRAIL-SL with the proteasome inhibitor Bortezomib (BTZ) was investigated, being BTZ able to sensitize tumour cells toward TRAIL-induced apoptosis. We demonstrated that sTRAIL preserved and improved its anti-tumour activity when coupled to nanocarriers. Moreover, sTRAIL-SL ameliorated its PK profile in blood allowing sTRAIL to exert a more potent anti-tumour activity, which led, upon BTZ priming, to a statistically significant enhanced life spans in two models of sTRAIL-resistant NB-bearing mice. Finally, mechanistic studies indicated that the combination of sTRAIL with BTZ sensitized sTRAIL-resistant NB tumour cells to sTRAIL-induced cell death, both in vitro and in vivo, through the Akt/GSK3/β-catenin axis-dependent mechanism. In conclusion, our results suggest that sTRAIL-SL might be an efficient vehicle for sTRAIL delivery and that its use in clinic, in combination with BTZ, might represent an adjuvant strategy for the treatment of stage IV, sTRAIL-resistant, NB patients.

Selection of pancreatic cancer cell-binding landscape phages and their use in development of anticancer nanomedicines

It is hypothesized that the use of targeted drug delivery systems can significantly improve the therapeutic index of small molecule chemotherapies by enhancing accumulation of the drugs at the site of disease. Phage display offers a high-throughput approach for selection of the targeting ligands. We have successfully isolated phage fusion proteins selective and specific for PANC-1 pancreatic cancer cells. Doxorubicin liposomes (Lipodox) modified with tumor-specific phage fusion proteins enhanced doxorubicin uptake specifically in PANC-1 cells as compared with unmodified Lipodox and also compared with normal breast epithelial cells. Phage protein-targeted Lipodox substantially increased the concentration of doxorubicin in the nuclei of PANC-1 cells in spite of P-glycoprotein-mediated drug efflux. The in vitro cytotoxic activity obtained with pancreatic cell-targeted Lipodox was greater than that of unmodified Lipodox. We present a novel and straightforward method for preparing pancreatic tumor-targeted nanomedicines by anchoring pancreatic cancer-specific phage proteins within the liposome bilayer.

The chick embryo chorioallantoic membrane as a model for tumor biology

Among the in vivo models, the chick embryo chorioallantoic membrane (CAM) has been used to implant several tumor types as well as malignant cell lines to study their growth rate, angiogenic potential and metastatic capability. This review article is focused on the major compelling literature data on the use of the CAM to investigate tumor growth and the metastatic process.

Nanomedicines in the future of pediatric therapy

Nanotechnology has become a key tool to overcome the main (bio)pharmaceutical drawbacks of drugs and to enable their passive or active targeting to specific cells and tissues. Pediatric therapies usually rely on the previous clinical experience in adults. However, there exists scientific evidence that drug pharmacokinetics and pharmacodynamics in children differ from those in adults. For example, the interaction of specific drugs with their target receptors undergoes changes over the maturation of the different organs and systems. A similar phenomenon is observed for toxicity and adverse effects. Thus, it is clear that the treatment of disease in children cannot be simplified to the direct adjustment of the dose to the body weight/surface. In this context, the implementation of innovative technologies (e.g., nanotechnology) in the pediatric population becomes extremely challenging. The present article overviews the different attempts to use nanotechnology to treat diseases in the pediatric population. Due to the relevance, though limited available literature on the matter, we initially describe from preliminary in vitro studies to preclinical and clinical trials aiming to treat pediatric infectious diseases and pediatric solid tumors by means of nanotechnology. Then, the perspectives of pediatric nanomedicine are discussed.

Multifunctional nanoparticles for brain tumor imaging and therapy

Brain tumors are a diverse group of neoplasms that often carry a poor prognosis for patients. Despite tremendous efforts to develop diagnostic tools and therapeutic avenues, the treatment of brain tumors remains a formidable challenge in the field of neuro-oncology. Physiological barriers including the blood-brain barrier result in insufficient accumulation of therapeutic agents at the site of a tumor, preventing adequate destruction of malignant cells. Furthermore, there is a need for improvements in brain tumor imaging to allow for better characterization and delineation of tumors, visualization of malignant tissue during surgery, and tracking of response to chemotherapy and radiotherapy. Multifunctional nanoparticles offer the potential to improve upon many of these issues and may lead to breakthroughs in brain tumor management. In this review, we discuss the diagnostic and therapeutic applications of nanoparticles for brain tumors with an emphasis on innovative approaches in tumor targeting, tumor imaging, and therapeutic agent delivery. Clinically feasible nanoparticle administration strategies for brain tumor patients are also examined. Furthermore, we address the barriers towards clinical implementation of multifunctional nanoparticles in the context of brain tumor management.

Synthesis, characterization, and evaluation of a novel amphiphilic polymer RGD-PEG-Chol for target drug delivery system

An amphiphilic polymer RGD-PEG-Chol which can be produced in large scale at a very low cost has been synthesized successfully. The synthesized intermediates and final products were characterized and confirmed by ¹H nuclear magnetic resonance spectrum (¹H NMR) and Fourier transform infrared spectrum (FT-IR). The paclitaxel- (PTX-) loaded liposomes based on RGD-PEG-Chol were then prepared by film formation method. The liposomes had a size within 100 nm and significantly enhanced the cytotoxicity of paclitaxel to B16F10 cell as demonstrated by MTT test (IC₅₀ = 0.079  μg/mL of RGD-modified PTX-loaded liposomes compared to 9.57  μg/mL of free PTX). Flow cytometry analysis revealed that the cellular uptake of coumarin encapsulated in the RGD-PEG-Chol modified liposome was increased for HUVEC cells. This work provides a reasonable, facile, and economic approach to prepare peptide-modified liposome materials with controllable performances and the obtained linear RGD-modified PTX-loaded liposomes might be attractive as a drug delivery system.

Heteromultivalent ligand-decoration for actively targeted nanomedicine

Active targeting has become an important component of nanomedicine design where nanovehicles are surface-decorated with cell receptor-specific or disease matrix-specific ligands to enable site-selective binding, retention and delivery of theranostic cargo. In this context, there have been numerous reports regarding surface-modification of nanovehicles with antibodies, antibody fragments, carbohydrates, aptamers and peptides as targeting ligands. However, majority of these reports have focused on using a single type of targeting moiety on the vehicle surface. In any disease development and progression, multiple receptors and proteins are often spatio-temporally upregulated simultaneously and heterogeneously. Rationalizing from this, a significant advantage can be envisioned in targeting multiple entities simultaneously using vehicle co-decoration with multiple types of ligands, to enhance binding activity and targeting specificity. To this end, we present a comprehensive up-to-date review on research endeavors in heteromultivalent ligand-modification of nanovehicles and provide a mechanistic rationale as well as an insightful discussion of this promising area, including findings from our own research.

Peptide-mediated liposomal Doxorubicin enhances drug delivery efficiency and therapeutic efficacy in animal models

Lung cancer ranks among the most common malignancies, and is the leading cause of cancer-related mortality worldwide. Chemotherapy for lung cancer can be made more specific to tumor cells, and less toxic to normal tissues, through the use of ligand-mediated drug delivery systems. In this study, we investigated the targeting mechanism of the ligand-mediated drug delivery system using a peptide, SP5-2, which specifically binds to non-small cell lung cancer (NSCLC) cells. Conjugation of SP5-2 to liposomes enhanced the amount of drug delivered directly into NSCLC cells, through receptor-mediated endocytosis. Functional SP5-2 improved the therapeutic index of Lipo-Dox by enhancing therapeutic efficacy, reducing side effects, and increasing the survival rate of tumor-bearing mice in syngenic, metastatic and orthotopic animal models. Accumulation of SP5-2-conjugated liposomal doxorubicin (SP5-2-LD) in tumor tissues was 11.2-fold higher than that of free doxorubicin, and the area under the concentration-time curve (AUC0-72 hours) was increased 159.2-fold. Furthermore, the experiment of bioavailability was assessed to confirm that SP5-2 elevates the uptake of the liposomal drugs by the tumor cells in vivo. In conclusion, the use of SP5-2-conjugated liposomes enhances pharmacokinetic properties, improves efficacy and safety profiles, and allows for controlled biodistribution and drug release.

CD13-positive bone marrow-derived myeloid cells promote angiogenesis, tumor growth, and metastasis

Angiogenesis is fundamental to tumorigenesis and an attractive target for therapeutic intervention against cancer. We have recently demonstrated that CD13 (aminopeptidase N) expressed by nonmalignant host cells of unspecified types regulate tumor blood vessel development. Here, we compare CD13 wild-type and null bone marrow-transplanted tumor-bearing mice to show that host CD13(+) bone marrow-derived cells promote cancer progression via their effect on angiogenesis. Furthermore, we have identified CD11b(+)CD13(+) myeloid cells as the immune subpopulation directly regulating tumor blood vessel development. Finally, we show that these cells are specifically localized within the tumor microenvironment and produce proangiogenic soluble factors. Thus, CD11b(+)CD13(+) myeloid cells constitute a population of bone marrow-derived cells that promote tumor progression and metastasis and are potential candidates for the development of targeted antiangiogenic drugs.

Phage protein-targeted cancer nanomedicines

Nanoencapsulation of anticancer drugs improves their therapeutic indices by virtue of the enhanced permeation and retention effect which achieves passive targeting of nanoparticles in tumors. This effect can be significantly enhanced by active targeting of nanovehicles to tumors. Numerous ligands have been proposed and used in various studies with peptides being considered attractive alternatives to antibodies. This is further reinforced by the availability of peptide phage display libraries which offer an unlimited reservoir of target-specific probes. In particular landscape phages with multivalent display of target-specific peptides which enable the phage particle itself to become a nanoplatform creates a paradigm for high throughput selection of nanoprobes setting the stage for personalized cancer management. Despite its promise, this conjugate of combinatorial chemistry and nanotechnology has not made a significant clinical impact in cancer management due to a lack of using robust processes that facilitate scale-up and manufacturing. To this end we proposed the use of phage fusion protein as the navigating modules of novel targeted nanomedicine platforms which are described in this review.

Bioengineering strategies for designing targeted cancer therapies

The goals of bioengineering strategies for targeted cancer therapies are (1) to deliver a high dose of an anticancer drug directly to a cancer tumor, (2) to enhance drug uptake by malignant cells, and (3) to minimize drug uptake by nonmalignant cells. Effective cancer-targeting therapies will require both passive- and active-targeting strategies and a thorough understanding of physiologic barriers to targeted drug delivery. Designing a targeted therapy includes the selection and optimization of a nanoparticle delivery vehicle for passive accumulation in tumors, a targeting moiety for active receptor-mediated uptake, and stimuli-responsive polymers for control of drug release. The future direction of cancer targeting is a combinatorial approach, in which targeting therapies are designed to use multiple-targeting strategies. The combinatorial approach will enable combination therapy for delivery of multiple drugs and dual ligand targeting to improve targeting specificity. Targeted cancer treatments in development and the new combinatorial approaches show promise for improving targeted anticancer drug delivery and improving treatment outcomes.

A liposomal drug platform overrides peptide ligand targeting to a cancer biomarker, irrespective of ligand affinity or density

One method for improving cancer treatment is the use of nanoparticle drugs functionalized with targeting ligands that recognize receptors expressed selectively by tumor cells. In theory such targeting ligands should specifically deliver the nanoparticle drug to the tumor, increasing drug concentration in the tumor and delivering the drug to its site of action within the tumor tissue. However, the leaky vasculature of tumors combined with a poor lymphatic system allows the passive accumulation, and subsequent retention, of nanosized materials in tumors. Furthermore, a large nanoparticle size may impede tumor penetration. As such, the role of active targeting in nanoparticle delivery is controversial, and it is difficult to predict how a targeted nanoparticle drug will behave in vivo. Here we report in vivo studies for α_vβ₆-specific H2009.1 peptide targeted liposomal doxorubicin, which increased liposomal delivery and toxicity to lung cancer cells in vitro. We systematically varied ligand affinity, ligand density, ligand stability, liposome dosage, and tumor models to assess the role of active targeting of liposomes to α_vβ₆. In direct contrast to the in vitro results, we demonstrate no difference in in vivo targeting or efficacy for H2009.1 tetrameric peptide liposomal doxorubicin, compared to control peptide and no peptide liposomes. Examining liposome accumulation and distribution within the tumor demonstrates that the liposome, and not the H2009.1 peptide, drives tumor accumulation, and that both targeted H2009.1 and untargeted liposomes remain in perivascular regions, with little tumor penetration. Thus H2009.1 targeted liposomes fail to improve drug efficacy because the liposome drug platform prevents the H2009.1 peptide from both actively targeting the tumor and binding to tumor cells throughout the tumor tissue. Therefore, using a high affinity and high specificity ligand targeting an over-expressed tumor biomarker does not guarantee enhanced efficacy of a liposomal drug. These results highlight the complexity of in vivo targeting.

Nanocarrier-mediated targeting of tumor and tumor vascular cells improves uptake and penetration of drugs into neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in children, accounting for about 8% of childhood cancers. Despite aggressive treatment, patients suffering from high-risk NB have very poor 5-year overall survival rate, due to relapsed and/or treatment-resistant tumors. A further increase in therapeutic dose intensity is not feasible, because it will lead to prohibitive short-term and long-term toxicities. New approaches with targeted therapies may improve efficacy and decrease toxicity. The use of drug delivery systems allows site specific delivery of higher payload of active agents associated with lower systemic toxicity compared to the use of conventional (“free”) drugs. The possibility of imparting selectivity to the carriers to the cancer foci through the use of a targeting moiety (e.g., a peptide or an antibody) further enhances drug efficacy and safety. We have recently developed two strategies for increasing local concentration of anti-cancer agents, such as CpG-containing oligonucleotides, small interfering RNAs, and chemotherapeutics in NB. For doing that, we have used the monoclonal antibody anti-disialoganglioside (GD₂), able to specifically recognize the NB tumor and the peptides containing NGR and CPRECES motifs, that selectively bind to the aminopeptidase N-expressing endothelial and the aminopeptidase A-expressing perivascular tumor cells, respectively. The review will focus on the use of tumor- and tumor vasculature-targeted nanocarriers to improve tumor targeting, uptake, and penetration of drugs in preclinical models of human NB.

Using functional nanomaterials to target and regulate the tumor microenvironment: diagnostic and therapeutic applications

Malignant tumors remain a major health burden throughout the world and effective therapeutic strategies are urgently needed. Cancer nanotechnology, as an integrated platform, has the potential to dramatically improve cancer diagnosis, imaging, and therapy, while reducing the toxicity associated with the current approaches. Tumor microenvironment is an ensemble performance of various stromal cells and extracellular matrix. The recent progress in understanding the critical roles and the underlying mechanisms of the tumor microenvironment on tumor progression has resulted in emerging diagnostic and therapeutic nanomaterials designed and engineered specifically targeting the microenvironment components. Meanwhile, the bio-physicochemical differences between tumor and normal tissues have recently been exploited to achieve specific tumor-targeting for cancer diagnosis and treatment. Here, the major players in the tumor microenvironment and their biochemical properties, which can be utilized for the design of multifunctional nanomaterials with the potential to target and regulate this niche, are summarized. The recent progress in engineering intelligent and versatile nanomaterials for targeting and regulating the tumor microenvironment is emphasized. Although further investigations are required to develop robust methods for more specific tumor-targeting and well-controlled nanomaterials, the applications of tumor microenvironment regulation-based nanotechnology for safer and more effective anticancer nanomedicines have been proven successful and will eventually revolutionize the current landscape of cancer therapy.

Enhanced anti-tumor and anti-angiogenic efficacy of a novel liposomal fenretinide on human neuroblastoma

Neuroblastoma is an embryonal tumor originating from the simpatico-adrenal lineage of the neural crest. It approximately accounts for about 15% of all pediatric oncology deaths. Despite advances in multimodal therapy, metastatic neuroblastoma tumors at diagnosis remain a clinical challenge. Retinoids are a class of compounds known to induce both terminal differentiation and apoptosis/necrosis of neuroblastoma cells. Among them, fenretinide (HPR) has been considered one of the most promising anti-tumor agent but it is partially efficacious due to both poor aqueous solubility and rapid metabolism. Here, we have developed a novel HPR formulation, by which the drug was encapsulated into sterically stabilized nanoliposomes (NL[HPR]) according to the Reverse Phase Evaporation method. This procedure led to a higher structural integrity of liposomes in organic fluids for a longer period of time, in comparison with our previous liposomal formulation developed by the film method. Moreover, NL[HPR] were further coupled with NGR peptides for targeting the tumor endothelial cell marker, aminopeptidase N (NGR-NL[HPR]). Orthotopically xenografted neuroblastoma-bearing mice treated with NGR-NL[HPR] lived statistically longer than mice untreated or treated with free HPR (NGR-NL[HPR] vs both control and HPR: P<0.0001). Also, NL[HPR] resulted in a statistically improved survival (NL[HPR] vs both control and HPR: P<0.001) but to a less extent if compared with that obtained with NGR-NL[HPR] (NGR-NL[HPR] vs NL[HPR]: P<0.01). Staining of tumor sections with antibodies specific for neuroblastoma and for either pericytes or endothelial cells evidenced that HPR reduced neuroblastoma growth through both anti-tumor and anti-angiogenic effects, mainly when delivered by NGR-NL[HPR]. Indeed, in this group of mice a marked reduction of tumor progression, of intra-tumoral vessel counts and VEGF expression, together with a marked down-modulation of matrix metalloproteinases MMP2 and MMP9, was observed. In conclusion, the use of this novel targeted delivery system for the apoptotic and antiangiogenic drug, fenretinide, could be considered as an adjuvant tool in the future treatment of neuroblastoma patients.

Novel phage display-derived neuroblastoma-targeting peptides potentiate the effect of drug nanocarriers in preclinical settings

Molecular targeting of drug delivery nanocarriers is expected to improve their therapeutic index while decreasing their toxicity. Here we report the identification and characterization of novel peptide ligands specific for cells present in high-risk neuroblastoma (NB), a childhood tumor mostly refractory to current therapies. To isolate such targeting moieties, we performed combined in vitro/ex-vivo phage display screenings on NB cell lines and on tumors derived from orthotopic mouse models of human NB. By designing proper subtractive protocols, we identified phage clones specific either for the primary tumor, its metastases, or for their respective stromal components. Globally, we isolated 121 phage-displayed NB-binding peptides: 26 bound the primary tumor, 15 the metastatic mass, 57 and 23 their respective microenvironments. Of these, five phage clones were further validated for their specific binding ex-vivo to biopsies from stage IV NB patients and to NB tumors derived from mice. All five clones also targeted tumor cells and vasculature in vivo when injected into NB-bearing mice. Coupling of the corresponding targeting peptides with doxorubicin-loaded liposomes led to a significant inhibition in tumor volume and enhanced survival in preclinical NB models, thereby paving the way to their clinical development.

The effect of liposomal size on the targeted delivery of doxorubicin to Integrin αvβ3-expressing tumor endothelial cells

Size of the liposomes (LPs) specially governs its biodistribution. In this study, LPs were developed with controlled sizes, where variation in LP size dictates the ligand-receptor interaction, cellular internalization and its distribution within the tumor microenvironment. The therapeutic efficacies of doxorubicin (DOX)-loaded RGD modified small size (~100 nm in diameter, dnm) and large size (~300 dnm) PEGylated LPs (RGD-PEG-LPs) were compared to that of Doxil (a clinically used DOX-loaded PEG-LP, ~100 dnm) in DOX resistant OSRC-2 (Renal cell carcinoma, RCC) tumor xenografts. Doxil, which accumulated in tumor tissue via the enhanced permeability and retention (EPR) effect, failed to suppress tumor growth. Small size RGD-PEG-LP, that targets the tumor endothelial cells (TECs) and extravasates to tumor cells, failed to provide anti-tumor effect. Large size RGD-PEG-LP preferentially targets the TECs via minimization of the EPR effect, and significantly reduced the tumor growth, which was exerted through its strong anti-angiogenic activity on the tumor vasculature rather than having a direct effect on DOX resistant RCC. The prepared large size RGD-PEG-LP that targets the TECs via interacting with Integrin αvβ3, is a potentially effective and alternate therapeutic strategy for the treatment of DOX resistant tumor cells by utilizing DOX, in cases where Doxil is ineffective.

Liposomal drug delivery systems: from concept to clinical applications

The first closed bilayer phospholipid systems, called liposomes, were described in 1965 and soon were proposed as drug delivery systems. The pioneering work of countless liposome researchers over almost 5 decades led to the development of important technical advances such as remote drug loading, extrusion for homogeneous size, long-circulating (PEGylated) liposomes, triggered release liposomes, liposomes containing nucleic acid polymers, ligand-targeted liposomes and liposomes containing combinations of drugs. These advances have led to numerous clinical trials in such diverse areas as the delivery of anti-cancer, anti-fungal and antibiotic drugs, the delivery of gene medicines, and the delivery of anesthetics and anti-inflammatory drugs. A number of liposomes (lipidic nanoparticles) are on the market, and many more are in the pipeline. Lipidic nanoparticles are the first nanomedicine delivery system to make the transition from concept to clinical application, and they are now an established technology platform with considerable clinical acceptance. We can look forward to many more clinical products in the future.

The therapeutic potential of nanoscale sphingolipid technologies

Nanotechnologies, while small in size, widen the scope of drug delivery options for compounds with problematic pharmacokinetics, such as bioactive sphingolipids. We describe the development of historical sphingolipid nanotechnologies, such as nanoliposomes, and project future uses for a broad repertoire of nanoscale sphingolipid therapy formulations. In particular, we describe sphingo-nanotherapies for treatment of cancer, inflammatory disease, and cardiovascular disease. We conclude with a discussion of the challenges associated with regulatory approval, scale-up, and development of these nanotechnology therapies for clinical applications.

Anti-angiogenesis in neuroblastoma

The nature of the angiogenic balance in neuroblastoma is complex, and a spectrum of angiogenesis stimulators and inhibitors have been detected in neuroblastoma tumours. The complex relationships between angiogenic cascade and anti-angiogenic agents in the tumour vascular phase have indicated that anti-angiogenesis can be considered as a strategy for the adjuvant therapy of neuroblastoma. The major goal is to establish if inhibition of angiogenesis is a realistic therapeutic strategy for inhibiting tumour cell dissemination and the formation of metastasis in neuroblastoma.

The use of therapeutic peptides to target and to kill cancer cells

Peptide therapeutics is a promising field for emerging anti-cancer agents. Benefits include the ease and rapid synthesis of peptides and capacity for modifications. An existing and vast knowledge base of protein structure and function can be exploited for novel peptide design. Current research focuses on developing peptides that can (1) serve as tumor targeting moieties and (2) permeabilize membranes with cytotoxic consequences. A survey of recent findings reveals significant trends. Amphiphilic peptides with clusters of hydrophobic and cationic residues are features of anti-microbial peptides that confer the ability to eradicate microbes and show considerable anti-cancer toxicity. Peptides that assemble and form pores can disrupt cell or organelle membranes and cause apoptotic or necrotic death. Cell permeable and tumor-homing peptides can carry biologically active cargo to tumors or tumor vasculature. The challenge lies in developing the clinical application of therapeutic peptides. Improving delivery to tumors, minimizing non-specific toxic effects and discerning pharmacokinetic properties are high among the needs to produce a powerful therapeutic peptide for cancer treatment.

RGD-based strategies to target alpha(v) beta(3) integrin in cancer therapy and diagnosis

The integrin α(v)β(3) plays an important role in angiogenesis. It is expressed on tumoral endothelial cells as well as on some tumor cells. RGD peptides are well-known to bind preferentially to the α(v)β(3) integrin. In this context, targeting tumor cells or tumor vasculature by RGD-based strategies is a promising approach for delivering anticancer drugs or contrast agents for cancer therapy and diagnosis. RGD-based strategies include antagonist drugs (peptidic or peptidomimetic) of the RGD sequence, RGD-conjugates, and the grafting of the RGD peptide or peptidomimetic, as targeting ligand, at the surface of nanocarriers. Although all strategies are overviewed, this review aims to particularly highlight the position of RGD-based nanoparticles in cancer therapy and imaging. This review is divided into three parts: the first one describes the context of angiogenesis, the role of the integrin α(v)β(3), and the binding of the RGD peptide to this integrin; the second one focuses on RGD-based strategies in cancer therapy; while the third one focuses on RGD-based strategies in cancer diagnosis.