Cyclic-RGDyC functionalized liposomes for dual-targeting of tumor vasculature and cancer cells in glioblastoma: An in vitro boron neutron capture therapy study

Enhancing anticancer treatment: Development of cRGD-Conjugated F-OH-Evo prodrugs for targeted delivery

Small molecule drugs sourced from natural products are pivotal for novel therapeutic discoveries. However, their clinical deployment is often impeded by non-specific activity and severe adverse effects. This study focused on 3-fluoro-10-hydroxy-Evodiamine (F-OH-Evo), a potent derivative of Evodiamine, whose development is curtailed due to suboptimal tumor selectivity and heightened cytotoxicity. By harnessing the remarkable stability, specificity, and αvβ3 integrin affinity of c(RGDFK), a novel prodrug by conjugating F-OH-Evo with cRGD was synthesized. This innovative prodrug substantially enhanced the tumor-specific targeting of F-OH-Evo and improved the anti-tumor activities. Among them, compound 3c demonstrated the best selective inhibitory activity toward U87 cancer cells in vitro. It selectively enterd U87 cells by binding to αvβ3 integrin, releasing the parent molecule under the dual response of ROS and GSH to exert inhibitory activity on topo I. The results highlight the potential of cRGD-conjugated prodrugs in targeted cancer therapy. This approach signifies a significant advancement in developing safer and more effective chemotherapy drugs, emphasizing the role of prodrug strategies in overcoming the limitations of traditional cancer treatments.

Targeted strategies to deliver boron agents across the blood-brain barrier for neutron capture therapy of brain tumors

Boron neutron capture therapy (BNCT), as an innovative radiotherapy technology, has demonstrated remarkable outcomes when compared to conventional treatments in the management of recurrent and refractory brain tumors. However, in BNCT of brain tumors, the blood-brain barrier is a main stumbling block for restricting the transport of boron drugs to brain tumors, while the tumor targeting and retention of boron drugs also affect the BNCT effect. This review focuses on the recent development of strategies for delivering boron drugs crossing the blood-brain barrier and targeting brain tumors, providing new insights for the development of efficient boron drugs for the treatment of brain tumors.

Laser-Synthesized Elemental Boron Nanoparticles for Efficient Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is one of the most appealing radiotherapy modalities, whose localization can be further improved by the employment of boron-containing nanoformulations, but the fabrication of biologically friendly, water-dispersible nanoparticles (NPs) with high boron content and favorable physicochemical characteristics still presents a great challenge. Here, we explore the use of elemental boron (B) NPs (BNPs) fabricated using the methods of pulsed laser ablation in liquids as sensitizers of BNCT. Depending on the conditions of laser-ablative synthesis, the used NPs were amorphous (a-BNPs) or partially crystallized (pc-BNPs) with a mean size of 20 nm or 50 nm, respectively. Both types of BNPs were functionalized with polyethylene glycol polymer to improve colloidal stability and biocompatibility. The NPs did not initiate any toxicity effects up to concentrations of 500 µg/mL, based on the results of MTT and clonogenic assay tests. The cells with BNPs incubated at a 10B concentration of 40 µg/mL were then irradiated with a thermal neutron beam for 30 min. We found that the presence of BNPs led to a radical enhancement in cancer cell death, namely a drop in colony forming capacity of SW-620 cells down to 12.6% and 1.6% for a-BNPs and pc-BNPs, respectively, while the relevant colony-forming capacity for U87 cells dropped down to 17%. The effect of cell irradiation by neutron beam uniquely was negligible under these conditions. Finally, to estimate the dose and regimes of irradiation for future BNCT in vivo tests, we studied the biodistribution of boron under intratumoral administration of BNPs in immunodeficient SCID mice and recorded excellent retention of boron in tumors. The obtained data unambiguously evidenced the effect of a neutron therapy enhancement, which can be attributed to efficient BNP-mediated generation of α-particles.

A state-of-the-art liposome technology for glioblastoma treatment

Glioblastoma (GBM) is a challenging problem due to the poor BBB permeability of cancer drugs, its recurrence after the treatment, and high malignancy and is difficult to treat with the currently available therapeutic strategies. Furthermore, the prognosis and survival rate of GBM are still poor after surgical removal via conventional combination therapy. Owing to the existence of the formidable blood-brain barrier (BBB) and the aggressive, infiltrating nature of GBM growth, the diagnosis and treatment of GBM are quite challenging. Recently, liposomes and their derivatives have emerged as super cargos for the delivery of both hydrophobic and hydrophilic drugs for the treatment of glioblastoma because of their advantages, such as biocompatibility, long circulation, and ease of physical and chemical modification, which facilitate the capability of targeting specific sites, circumvention of BBB transport restrictions, and amplification of the therapeutic efficacy. Herein, we provide a timely update on the burgeoning liposome-based drug delivery systems and potential challenges in these fields for the diagnosis and treatment of brain tumors. Furthermore, we focus on the most recent liposome-based drug delivery cargos, including pH-sensitive, temperature-sensitive, and biomimetic liposomes, to enhance the multimodality in imaging and therapeutics of glioblastoma. Furthermore, we highlight the future difficulties and directions for the research and clinical translation of liposome-based drug delivery. Hopefully, this review will trigger the interest of researchers to expedite the development of liposome cargos and even their clinical translation for improving the prognosis of glioblastoma.

Surface modification strategies in translocating nano-vesicles across different barriers and the role of bio-vesicles in improving anticancer therapy

Nanovesicles and bio-vesicles (BVs) have emerged as promising tools to achieve targeted cancer therapy due to their ability to overcome many of the key challenges currently being faced with conventional chemotherapy. These challenges include the diverse and often complex pathophysiology involving the progression of cancer, as well as the various biological barriers that circumvent therapeutic molecules reaching their target site in optimum concentration. The scientific evidence suggests that surface-functionalized nanovesicles and BVs camouflaged nano-carriers (NCs) both can bypass the established biological barriers and facilitate fourth-generation targeting for the improved regimen of treatment. In this review, we intend to emphasize the role of surface-functionalized nanovesicles and BVs camouflaged NCs through various approaches that lead to an improved internalization to achieve improved and targeted oncotherapy. We have explored various strategies that have been employed to surface-functionalize and biologically modify these vesicles, including the use of biomolecule functionalized target ligands such as peptides, antibodies, and aptamers, as well as the targeting of specific receptors on cancer cells. Further, the utility of BVs, which are made from the membranes of cells such as mesenchymal stem cells (MSCs), white blood cells (WBCs), red blood cells (RBCs), platelets (PLTs) as well as cancer cells also been investigated. Lastly, we have discussed the translational challenges and limitations that these NCs can encounter and still need to be overcome in order to fully realize the potential of nanovesicles and BVs for targeted cancer therapy. The fundamental challenges that currently prevent successful cancer therapy and the necessity of novel delivery systems are in the offing.

Next generation of boron neutron capture therapy (BNCT) agents for cancer treatment

Boron neutron capture therapy (BNCT) is one of the most promising treatments among neutron capture therapies due to its long-term clinical application and unequivocally obtained success during clinical trials. Boron drug and neutron play an equivalent crucial role in BNCT. Nevertheless, current clinically used l-boronophenylalanine (BPA) and sodium borocaptate (BSH) suffer from large uptake dose and low blood to tumor selectivity, and that initiated overwhelm screening of next generation of BNCT agents. Various boron agents, such as small molecules and macro/nano-vehicles, have been explored with better success. In this featured article, different types of agents are rationally analyzed and compared, and the feasible targets are shared to present a perspective view for the future of BNCT in cancer treatment. This review aims at summarizing the current knowledge of a variety of boron compounds, reported recently, for the application of BCNT.

Synthesis of Novel Carborane-Containing Derivatives of RGD Peptide

Short peptides containing the Arg-Gly-Asp (RGD) fragment can selectively bind to integrins on the surface of tumor cells and are attractive transport molecules for the targeted delivery of therapeutic and diagnostic agents to tumors (for example, glioblastoma). We have demonstrated the possibility of obtaining the N- and C-protected RGD peptide containing 3-amino-closo-carborane and a glutaric acid residue as a linker fragment. The resulting carboranyl derivatives of the protected RGD peptide are of interest as starting compounds in the synthesis of unprotected or selectively protected peptides, as well as building blocks for preparation of boron-containing derivatives of the RGD peptide of a more complex structure.

Functionalisation of extracellular vesicles with cyclic-RGDyC potentially for glioblastoma targeted intracellular drug delivery

With the intrinsic ability to cross the blood-brain barrier, small extracellular vesicles (sEVs) hold promise as endogenous brain-targeted drug delivery nano-platforms for glioblastoma (GBM) treatment. To increase GBM targetability, this study aimed to functionalise sEVs with cyclic arginine-glycine-aspartic acid-tyrosine-cysteine (cRGDyC), a ligand for integrin (α_vβ₃) that is overexpressed in GBM cells. Firstly, the intrinsic cellular uptake of sEVs derived from GBM U87 and pancreatic cancer MIA PaCa-2 cells was investigated on the donor cells. To obtain functionalised sEVs (cRGDyC-sEVs), DSPE-mPEG₂₀₀₀-maleimide was incubated with the selected (U87) sEVs, and cRGDyC was subsequently conjugated to the maleimide groups via a thiol-maleimide coupling reaction. The GBM cell targetability and intracellular trafficking of cRGDyC-sEVs were evaluated on U87 cells by fluorescence and confocal microscopy, using unmodified sEVs as a reference. The cytotoxicity of doxorubicin-loaded vesicles (Dox@sEVs, Dox@cRGDyC-sEVs) was compared with a standard liposome formulation (Dox@Liposomes) and free Dox. Both U87 and MIA PaCa-2 cell-derived sEVs displayed tropism with the former being >4.9-fold more efficient to be internalised into U87. Therefore, the U87-derived sEVs were chosen for GBM-targeting. Approximately 4000 DSPE-mPEG₂₀₀₀-maleimide were inserted onto each sEV with cRGDyC conjugated to the maleimide group. The cell targetability of cRGDyC-sEVs to U87 cells improved 2.4-fold than natural sEVs. Despite their proneness to be colocalised with endosomes/lysosomes, both Dox@sEVs and Dox@cRGDyC-sEVs showed superior cytotoxicity to U87 GBM cells compared to Dox@Liposomes, particularly Dox@cRGDyC-sEVs. Overall, U87-derived sEVs were successufully conjugated with cRGDyC via a PEG linker, and cRGDyC-sEVs were demonstrated to be a potnetial integrin-targeting drug delivery vehicle for GBM treatment. Graphic abstract.

Peptide-assembled nanoparticles targeting tumor cells and tumor microenvironment for cancer therapy

Tumor cells and corrupt stromal cells in the tumor microenvironment usually overexpress cancer-specific markers that are absent or barely detectable in normal cells, providing available targets for inhibiting the occurrence and development of cancers. It is noticeable that therapeutic peptides are emerging in cancer therapies and playing more and more important roles. Moreover, the peptides can be self-assembled and/or incorporated with polymeric molecules to form nanoparticles via non-covalent bond, which have presented appealing as well as enhanced capacities of recognizing targeted cells, responding to microenvironments, mediating internalization, and achieving therapeutic effects. In this review, we will introduce the peptide-based nanoparticles and their application advances in targeting tumor cells and stromal cells, including suppressive immune cells, fibrosis-related cells, and angiogenic vascular cells, for cancer therapy.

Targeting Ultrasmall Gold Nanoparticles with cRGD Peptide Increases the Uptake and Efficacy of Cytotoxic Payload

Cyclic arginyl-glycyl-aspartic acid peptide (cRGD) peptides show a high affinity towards αVβ3 integrin, a receptor overexpressed in many cancers. We aimed to combine the versatility of ultrasmall gold nanoparticles (usGNP) with the target selectivity of cRGD peptide for the directed delivery of a cytotoxic payload in a novel design. usGNPs were synthesized with a modified Brust-Schiffrin method and functionalized via amide coupling and ligand exchange and their uptake, intracellular trafficking, and toxicity were characterized. Our cRGD functionalized usGNPs demonstrated increased cellular uptake by αVβ3 integrin expressing cells, are internalized via clathrin-dependent endocytosis, accumulated in the lysosomes, and when loaded with mertansine led to increased cytotoxicity. Targeting via cRGD functionalization provides a mechanism to improve the efficacy, tolerability, and retention of therapeutic GNPs.

Boron Neutron Capture Therapy: Clinical Application and Research Progress

Boron neutron capture therapy (BNCT) is a binary modality that is used to treat a variety of malignancies, using neutrons to irradiate boron-10 (¹⁰B) nuclei that have entered tumor cells to produce highly linear energy transfer (LET) alpha particles and recoil ⁷Li nuclei (¹⁰B [n, α] ⁷Li). Therefore, the most important part in BNCT is to selectively deliver a large number of ¹⁰B to tumor cells and only a small amount to normal tissue. So far, BNCT has been used in more than 2000 cases worldwide, and the efficacy of BNCT in the treatment of head and neck cancer, malignant meningioma, melanoma and hepatocellular carcinoma has been confirmed. We collected and collated clinical studies of second-generation boron delivery agents. The combination of different drugs, the mode of administration, and the combination of multiple treatments have an important impact on patient survival. We summarized the critical issues that must be addressed, with the hope that the next generation of boron delivery agents will overcome these challenges.

Importance of radiobiological studies for the advancement of boron neutron capture therapy (BNCT)

Boron neutron capture therapy (BNCT) is a tumour selective particle radiotherapy, based on the administration of boron carriers incorporated preferentially by tumour cells, followed by irradiation with a thermal or epithermal neutron beam. BNCT clinical results to date show therapeutic efficacy, associated with an improvement in patient quality of life and prolonged survival. Translational research in adequate experimental models is necessary to optimise BNCT for different pathologies. This review recapitulates some examples of BNCT radiobiological studies for different pathologies and clinical scenarios, strategies to optimise boron targeting, enhance BNCT therapeutic effect and minimise radiotoxicity. It also describes the radiobiological mechanisms induced by BNCT, and the importance of the detection of biomarkers to monitor and predict the therapeutic efficacy and toxicity of BNCT alone or combined with other strategies. Besides, there is a brief comment on the introduction of accelerator-based neutron sources in BNCT. These sources would expand the clinical BNCT services to more patients, and would help to make BNCT a standard treatment modality for various types of cancer. Radiobiological BNCT studies have been of utmost importance to make progress in BNCT, being essential to design novel, safe and effective clinical BNCT protocols.

Polymer-Stabilized Elemental Boron Nanoparticles for Boron Neutron Capture Therapy: Initial Irradiation Experiments

Sufficient boron-10 isotope (10B) accumulation by tumor cells is one of the main requirements for successful boron neutron capture therapy (BNCT). The inability of the clinically registered 10B-containing borophenylalanine (BPA) to maintain a high boron tumor concentration during neutron irradiation after a single injection has been partially solved by its continuous infusion; however, its lack of persistence has driven the development of new compounds that overcome the imperfections of BPA. We propose using elemental boron nanoparticles (eBNPs) synthesized by cascade ultrasonic dispersion and destruction of elemental boron microparticles and stabilized with hydroxyethylcellulose (HEC) as a core component of a novel boron drug for BNCT. These HEC particles are stable in aqueous media and show no apparent influence on U251, U87, and T98G human glioma cell proliferation without neutron beam irradiation. In BNCT experiments, cells incubated with eBNPs or BPA at an equivalent concentration of 40 µg 10B/mL for 24 h or control cells without boron were irradiated at an accelerator-based neutron source with a total fluence of thermal and epithermal neutrons of 2.685, 5.370, or 8.055 × 1012/cm2. The eBNPs significantly reduced colony-forming capacity in all studied cells during BNCT compared to BPA, verified by cell-survival curves fit to the linear-quadratic model and calculated radiobiological parameters, though the effect of both compounds differed depending on the cell line. The results of our study warrant further tumor targeting-oriented modifications of synthesized nanoparticles and subsequent in vivo BNCT experiments.

Liposomes loaded with polyphenol-rich grape pomace extracts protect from neurodegeneration in a rotenone-based in vitro model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with no satisfactory therapy options. Similar to other neurodegenerative conditions, such as Alzheimer's and Huntington's diseases, oxidative stress plays a key factor in the neurodegeneration process. To counteract the uncontrolled increase of reactive oxygen species (ROS) and oxidative stress-dependent cell death, several preclinical and clinical tests exploit natural-derived organic antioxidants, such as polyphenols. Despite some promising results, free antioxidants show scarce brain accumulation and may exhaust their scavenging activity before reaching the brain. In this work, we developed an antioxidant therapeutic nanoplatform consisting of nano-sized functionalized liposomes loaded with selected polyphenol-rich vegetal extracts with high blood-brain barrier crossing capabilities. The antioxidant extracts were obtained from the grape seeds and skins as a byproduct of wine production (i.e., pomace), following a sustainable circular approach with reduced environmental impact. The antioxidant nanoplatform was successfully tested in a relevant in vitro model of PD, where it completely rescued the ROS levels, prevented the aggregation of α-synuclein fibrils, and restored cell viability, paving the way for preclinical translation of the approach.

Nanoparticles modified with vasculature-homing peptides for targeted cancer therapy and angiogenesis imaging

The two major challenges in cancer treatment include lack of early detection and ineffective therapies with various side effects. Angiogenesis is the key process in the growth, survival, invasiveness, and metastasis of many of cancerous tumors. Imaging of the angiogenesis could lead to diagnosis of tumors in the early stage and evaluation of the therapeutic responses. Angiogenic blood vessels express specific molecular markers different from normal blood vessels (in level or kind). This fact would make the tumor vasculature a suitable site to target therapeutics and imaging agents within the tumor. Surface modified nanoparticles using peptide ligands with high binding affinity to the vasculature markers, provide efficient delivery of therapeutic and imaging agents, while avoiding undesirable side effects. In this review, we discuss discoveries of various tumor targeting peptides useful for tumor angiogenesis imaging and targeted therapy with emphasis on surface modified nanomedicines using vasculature targeting peptides.

Application of Non-Viral Vectors in Drug Delivery and Gene Therapy

Vectors and carriers play an indispensable role in gene therapy and drug delivery. Non-viral vectors are widely developed and applied in clinical practice due to their low immunogenicity, good biocompatibility, easy synthesis and modification, and low cost of production. This review summarized a variety of non-viral vectors and carriers including polymers, liposomes, gold nanoparticles, mesoporous silica nanoparticles and carbon nanotubes from the aspects of physicochemical characteristics, synthesis methods, functional modifications, and research applications. Notably, non-viral vectors can enhance the absorption of cargos, prolong the circulation time, improve therapeutic effects, and provide targeted delivery. Additional studies focused on recent innovation of novel synthesis techniques for vector materials. We also elaborated on the problems and future research directions in the development of non-viral vectors, which provided a theoretical basis for their broad applications.

A Critical Review of Radiation Therapy: From Particle Beam Therapy (Proton, Carbon, and BNCT) to Beyond

In this paper, we discuss the role of particle therapy—a novel radiation therapy (RT) that has shown rapid progress and widespread use in recent years—in multidisciplinary treatment. Three types of particle therapies are currently used for cancer treatment: proton beam therapy (PBT), carbon-ion beam therapy (CIBT), and boron neutron capture therapy (BNCT). PBT and CIBT have been reported to have excellent therapeutic results owing to the physical characteristics of their Bragg peaks. Variable drug therapies, such as chemotherapy, hormone therapy, and immunotherapy, are combined in various treatment strategies, and treatment effects have been improved. BNCT has a high dose concentration for cancer in terms of nuclear reactions with boron. BNCT is a next-generation RT that can achieve cancer cell-selective therapeutic effects, and its effectiveness strongly depends on the selective ¹⁰B accumulation in cancer cells by concomitant boron preparation. Therefore, drug delivery research, including nanoparticles, is highly desirable. In this review, we introduce both clinical and basic aspects of particle beam therapy from the perspective of multidisciplinary treatment, which is expected to expand further in the future.

Peptide functionalized liposomes for receptor targeted cancer therapy

Most clinically approved cancer therapies are potent and toxic small molecules that are limited by severe off-target toxicities and poor tumor-specific localization. Over the past few decades, attempts have been made to load chemotherapies into liposomes, which act to deliver the therapeutic agent directly to the tumor. Although liposomal encapsulation has been shown to decrease toxicity in human patients, reliance on passive targeting via the enhanced permeability and retention (EPR) effect has left some of these issues unresolved. Recently, investigations into modifying the surface of liposomes via covalent and/or electrostatic functionalization have offered mechanisms for tumor homing and subsequently controlled chemotherapeutic delivery. A wide variety of biomolecules can be utilized to functionalize liposomes such as proteins, carbohydrates, and nucleic acids, which enable multiple directions for cancer cell localization. Importantly, when nanoparticles are modified with such molecules, care must be taken as not to inactivate or denature the ligand. Peptides, which are small proteins with <30 amino acids, have demonstrated the exceptional ability to act as ligands for transmembrane protein receptors overexpressed in many tumor phenotypes. Exploring this strategy offers a method in tumor targeting for cancers such as glioblastoma multiforme, pancreatic, lung, and breast based on the manifold of receptors overexpressed on various tumor cell populations. In this review, we offer a comprehensive summary of peptide-functionalized liposomes for receptor-targeted cancer therapy.

Strategies to better treat glioblastoma: antiangiogenic agents and endothelial cell targeting agents

Glioblastoma multiforme (GBM) is the most prevalent and aggressive form of glioma, with poor prognosis and high mortality rates. As GBM is a highly vascularized cancer, antiangiogenic therapies to halt or minimize the rate of tumor growth are critical to improving treatment. In this review, antiangiogenic therapies, including small-molecule drugs, nucleic acids and proteins and peptides, are discussed. The authors further explore biomaterials that have been utilized to increase the bioavailability and bioactivity of antiangiogenic factors for better antitumor responses in GBM. Finally, the authors summarize the current status of biomaterial-based targeting moieties that target endothelial cells in GBM to more efficiently deliver therapeutics to these cells and avoid off-target cell or organ side effects.

In Vitro and In Vivo Evaluation of Fluorescently Labeled Borocaptate-Containing Liposomes

Boron neutron capture therapy (BNCT), a binary cancer therapeutic modality, has moved to a new phase since development of accelerator-based neutron sources and establishment of BNCT centers in Finland and Japan. That stimulated efforts for better boron delivery agent development. As liposomes have shown effective boron delivery properties and sufficient tumor retention, fluorescent liposome labelling may serve as a rapid method to study initial ability of newly synthesized liposomes to be captured by tumor cells prior to experiments on boron accumulation and neutron irradiation. In this work, we studied the accumulation and biodistribution of pegylated liposomes with encapsulated borocaptate (BSH) and a fluorescent label (Nile Red) in U87 (human glioblastoma), SW-620 (human colon carcinoma), SK-MEL-28 (human melanoma), FetMSC (mesenchymal human embryo stem cells), and EMBR (primary embryocytes) cell lines as well as an orthotopic xenograft model of U87 glioma in SCID mice. Results indicate that fluorescent microscopy is effective at determining the intracellular localization of the liposomes using a fluorescent label. The synthesized, pegylated liposomes showed higher accumulation in tumors compared to normal cells, with characteristic concentration peaks in SW-620 and U87 cell lines, and provided in vivo tumor selectivity with several-fold higher tumor tissue fluorescence at the 6-h timepoint. Graphical abstract Fluorescent images of U-87 glioma cells after 24 hours of incubation with BSH-containing liposomes labeled with lipophilic Nile Red (red color)and water-soluble FITC-Dextran (green color); cell nuclei in blue color (DAPI-staining) (×400). Scale bar is 50 μm. Fluorescent labelling serves as anexpress method to study liposome delivery efficiency prior to boron accumulation evaluation and BNCT irradiation experiments.

Boron neutron capture therapy: Current status and future perspectives

The development of new accelerators has given a new impetus to the development of new drugs and treatment technologies using boron neutron capture therapy (BNCT). We analyzed the current status and future directions of BNCT for cancer treatment, as well as the main issues related to its introduction. This review highlights the principles of BNCT and the key milestones in its development: new boron delivery drugs and different types of charged particle accelerators are described; several important aspects of BNCT implementation are discussed. BCNT could be used alone or in combination with chemotherapy and radiotherapy, and it is evaluated in light of the outlined issues. For the speedy implementation of BCNT in medical practice, it is necessary to develop more selective boron delivery agents and to generate an epithermal neutron beam with definite characteristics. Pharmacological companies and research laboratories should have access to accelerators for large-scale screening of new, more specific boron delivery agents.

A treatise on endothelial biology and exosomes: homage to Theresa Maria Listowska Whiteside

Exosomes are the current primary research focus of Dr. Theresa L. Whiteside. They are key mediators of intercellular communication in the head and neck, as well as other sites. Their effects in the tumor microenvironment are manifold and include suppression of immunity, promotion of angiogenesis, enabling of metastasis, as well as reprogramming of fibroblasts and mesenchymal stromal cells. The aim of this communication is to summarize Dr. Whiteside's contribution to the field of exosome research and details the interactions of exosomes with endothelial cells leading to recent findings on how to target endothelial cells using exosomes as a therapeutic approach.

Liposomes modified with bio-substances for cancer treatment

In recent years, liposomes have been used in the field of biomedicine and have achieved many significant results.

Ultrasmall PEGylated and Targeted Core-Shell Silica Nanoparticles Carrying Methylene Blue Photosensitizer

Photodynamic therapy (PDT) presents an alternative noninvasive therapeutic modality for the treatment of cancer and other diseases. PDT relies on cytotoxic singlet oxygen (reactive oxygen species or ROS) that is locally generated through energy transfer between a photosensitizer (PS) and molecularly dissolved triplet oxygen. While a number of nanoparticle-based PS vehicles have been described, because of their beneficial and proven biodistribution and pharmacokinetic profiles, ultrasmall nanoparticles with diameters below 10 nm are particularly promising. Here, we investigate two different particle designs deviating from ultrasmall poly(ethylene glycol)-coated (PEGylated) fluorescent core-shell silica nanoparticles referred to as Cornell prime dots (C' dots) by replacing the fluorescent dye with a photosensitizer (psC' dots), here the methylene blue (MB) derivate MB2. In the first approach (design 1), MB2 is encapsulated into the matrix of the silica core, while in the second approach (design 2), MB2 is grafted onto the silica core surface in between chains of the sterically stabilizing poly(ethylene glycol) (PEG) corona. We compare both cases with regard to their singlet oxygen quantum yields, Φ_Δ, with the effective Φ_Δ^eff per particle reaching 111 ± 3 and 161 ± 5% for designs 1 and 2, respectively, substantially exceeding single MB2 molecule performance. Encapsulation significantly improves PS photostability, while surface conjugation diminishes it, relative to free MB2. Finally, we show that both particle designs allow functionalization with a targeting peptide, cyclo(Arg-Gly-Asp-D-Tyr-Cys) [c(RGDyC)]. Results suggest that psC' dots are a promising targeted platform for PDT applications, e.g. in oncology, that may combine colloidal stability, efficient renal clearance limiting off-target accumulation, targeted delivery to sites of disease, and effective ROS generation maximizing therapeutic efficacy.

Targeting Tumor Endothelial Cells with Nanoparticles

Because angiogenesis is a major contributor to cancer progression and metastasis, it is an attractive target for cancer therapy. Although a diverse number of small compounds for anti-angiogenic therapy have been developed, severe adverse effects commonly occur, since small compounds can affect not only tumor endothelial cells (TECs), but also normal endothelial cells. This low selectivity for TECs has motivated researchers to develop alternate types of drug delivery systems (DDSs). In this review, we summarize the current state of knowledge concerning the delivery of nano DDSs to TECs. Their payloads range from small compounds to nucleic acids. Perspectives regarding new therapeutic targets are also mentioned.

Peptide-Conjugated Nanoparticles as Targeted Anti-angiogenesis Therapeutic and Diagnostic in Cancer

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Targeting angiogenesis in the microenvironment of a tumor can enable suppression of tumor angiogenesis and delivery of anticancer drugs into the tumor. Anti-angiogenesis targeted delivery systems utilizing passive targeting such as Enhanced Permeability and Retention (EPR) and specific receptor-mediated targeting (active targeting) should result in tumor-specific targeting. One targeted anti-angiogenesis approach uses peptides conjugated to nanoparticles, which can be loaded with anticancer agents. Anti-angiogenesis agents can suppress tumor angiogenesis and thereby affect tumor growth progression (tumor growth arrest), which may be further reduced with the targetdelivered anticancer agent. This review provides an update of tumor vascular targeting for therapeutic and diagnostic applications, with conventional or long-circulating nanoparticles decorated with peptides that target neovascularization (anti-angiogenesis) in the tumor microenvironment.

BNCT induced immunomodulatory effects contribute to mammary tumor inhibition

In the United States, breast cancer is one of the most common and the second leading cause of cancer-related death in women. Treatment modalities for mammary tumor are surgical removal of the tumor tissue followed by either chemotherapy or radiotherapy or both. Radiation therapy is a whole body irradiation regimen that suppresses the immune system leaving hosts susceptible to infection or secondary tumors. Boron neutron capture therapy (BNCT) in that regard is more selective, the cells that are mostly affected are those that are loaded with 109 or more 10B atoms. Previously, we have described that liposomal encapsulation of boron-rich compounds such as TAC and MAC deliver a high payload to the tumor tissue when injected intravenously. Here we report that liposome-mediated boron delivery to the tumor is inversely proportional to the size of the murine mammary (EMT-6) tumors. The plausible reason for the inverse ratio of boron and EMT-6 tumor size is the necrosis in these tumors, which is more prominent in the large tumors. The large tumors also have receding blood vessels contributing further to poor boron delivery to these tumors. We next report that the presence of boron in blood is essential for the effects of BNCT on EMT-6 tumor inhibition as direct injection of boron-rich liposomes did not provide any added advantage in inhibition of EMT-6 tumor in BALB/c mice following irradiation despite having a significantly higher amount of boron in the tumor tissue. BNCT reaction in PBMCs resulted in the modification of these cells to anti-tumor phenotype. In this study, we report the immunomodulatory effects of BNCT when boron-rich compounds are delivered systemically.

Multitargeted Nanoparticles Deliver Synergistic Drugs across the Blood-Brain Barrier to Brain Metastases of Triple Negative Breast Cancer Cells and Tumor-Associated Macrophages

Patients with brain metastases of triple negative breast cancer (TNBC) have a poor prognosis owing to the lack of targeted therapies, the aggressive nature of TNBC, and the presence of the blood-brain barrier (BBB) that blocks penetration of most drugs. Additionally, infiltration of tumor-associated macrophages (TAMs) promotes tumor progression. Here, a terpolymer-lipid hybrid nanoparticle (TPLN) system is designed with multiple targeting moieties to first undergo synchronized BBB crossing and then actively target TNBC cells and TAMs in microlesions of brain metastases. In vitro and in vivo studies demonstrate that covalently bound polysorbate 80 in the terpolymer enables the low-density lipoprotein receptor-mediated BBB crossing and TAM-targetability of the TPLN. Conjugation of cyclic internalizing peptide (iRGD) enhances cellular uptake, cytotoxicity, and drug delivery to brain metastases of integrin-overexpressing TNBC cells. iRGD-TPLN with coloaded doxorubicin (DOX) and mitomycin C (MMC) (iRGD-DMTPLN) exhibits higher efficacy in reducing metastatic burden and TAMs than nontargeted DMTPLN or a free DOX/MMC combination. iRGD-DMTPLN treatment reduces metastatic burden by 6-fold and 19-fold and increases host median survival by 1.3-fold and 1.6-fold compared to DMTPLN or free DOX/MMC treatments, respectively. These findings suggest that iRGD-DMTPLN is a promising multitargeted drug delivery system for the treatment of integrin-overexpressing brain metastases of TNBC.

Glioblastoma Treatment Modalities besides Surgery

Glioblastoma multiforme (GBM) is commonly known as the most aggressive primary CNS tumor in adults. The mean survival of it is 14 to 15 months, following the standard therapy from surgery, chemotherapy, to radiotherapy. Efforts in recent decades have brought many novel therapies to light, however, with limitations. In this paper, authors reviewed current treatments for GBM besides surgery. In the past decades, only radiotherapy, temozolomide (TMZ), and tumor treating field (TTF) were approved by FDA. Though promising in preclinical experiments, therapeutic effects of other novel treatments including BNCT, anti-angiogenic therapy, immunotherapy, epigenetic therapy, oncolytic virus therapy, and gene therapy are still either uncertain or discouraging in clinical results. In this review, we went through current clinical trials, underlying causes, and future therapy designs to present neurosurgeons and researchers a sketch of this field.

Targeting integrins for cancer management using nanotherapeutic approaches: Recent advances and challenges

Integrins are the main cell surface receptors and execute multifaceted functions such as the bidirectional transmission of signals (i.e., inside-out and outside-in) and provide communication between cells and their microenvironments. Integrins are the key regulators of critical biological functions and contribute significantly to the promotion of cancer at almost every stage of disease progression from initial tumor formation to metastasis. Integrin expressions are frequently altered in different cancers, and consequently, several therapeutic strategies targeting integrins have been developed. Furthermore, nanotechnology-based approaches have been devised to overcome the intrinsic limitations of conventional therapies for cancer management, and have been shown to more precise, safer, and highly effective therapeutic tools. Although nanotechnology-based approaches have achieved substantial success for the management of cancer, certain obstacles remain such as inadequate knowledge of nano-bio interactions and the challenges associated with the three stages of clinical trials. This review highlights the different roles of integrins and of integrin-dependent signaling in various cancers and describes the applications of nanotherapeutics targeting integrins. In addition, we discuss RGD-based approaches and challenges posed to cancer management.

Electroporation optimizes the uptake of boron-10 by tumor for boron neutron capture therapy (BNCT) mediated by GB-10: a boron biodistribution study in the hamster cheek pouch oral cancer model

Boron neutron capture therapy (BNCT) is a promising cancer binary therapy modality that utilizes the nuclear capture reaction of thermal neutrons by boron-10 resulting in a localized release of high- and low-linear energy transfer (LET) radiation. Electrochemotherapy (ECT) is based on electroporation (EP) that induces opening of pores in cell membranes, allowing the entry of compounds. Because EP is applied locally to a tumor, the compound is incorporated preferentially by tumor cells. Based on the knowledge that the therapeutic success of BNCT depends centrally on the boron content in tumor and normal tissues and that EP has proven to be an excellent facilitator of tumor biodistribution of an anti-tumor agent, the aim of this study was to evaluate if EP can optimize the delivery of boronated compounds. We performed biodistribution studies and qualitative microdistribution analyses of boron employing the boron compound sodium decahydrodecaborate (GB-10) + EP in the hamster cheek pouch oral cancer model. Syrian hamsters with chemically induced exophytic squamous cell carcinomas were used. A typical EP treatment was applied to each tumor, varying the moment of application with respect to the administration of GB-10 (early or late). The results of this study showed a significant increase in the absolute and relative tumor boron concentration and optimization of the qualitative microdistribution of boron by the use of early EP + GB-10 versus GB-10 without EP. This strategy could be a tool to improve the therapeutic efficacy of BNCT/GB-10 in vivo.

Multimerization Increases Tumor Enrichment of Peptide⁻Photosensitizer Conjugates

Photodynamic therapy (PDT) is an established therapeutic modality for the management of cancers. Conjugation with tumor-specific small molecule ligands (e.g., short peptides or peptidomimetics) could increase the tumor targeting of PDT agents, which is very important for improving the outcome of PDT. However, compared with antibody molecules, small molecule ligands have a much weaker affinity to their receptors, which means that their tumor enrichment is not always ideal. In this work, we synthesized multimeric RGD ligand-coupled conjugates of pyropheophorbide-a (Pyro) to increase the affinity through multivalent and cluster effects to improve the tumor enrichment of the conjugates. Thus, the dimeric and trimeric RGD peptide-coupled Pyro conjugates and the monomeric one for comparison were efficiently synthesized via a convergent strategy. A short polyethylene glycol spacer was introduced between two RGD motifs to increase the distance required for multivalence. A subsequent binding affinity assay verified the improvement of the binding towards integrin α_vβ₃ receptors after the increase in the valence, with an approximately 20-fold improvement in the binding affinity of the trimeric conjugate compared with that of the monomeric conjugate. In vivo experiments performed in tumor-bearing mice also confirmed a significant increase in the distribution of the conjugates in the tumor site via multimerization, in which the trimeric conjugate had the best tumor enrichment compared with the other two conjugates. These results indicated that the multivalence interaction can obviously increase the tumor enrichment of RGD peptide-conjugated Pyro photosensitizers, and the prepared trimeric conjugate can be used as a novel antitumor photodynamic agent with high tumor enrichment.

Paclitaxel-loaded multifunctional nanoparticles for the targeted treatment of glioblastoma

INTRODUCTION

We hypothesised that the active targeting of αvβ3 integrin overexpressed in neoangiogenic blood vessels and glioblastoma (GBM) cells combined with magnetic targeting of paclitaxel- and SPIO-loaded PLGA-based nanoparticles could improve accumulation of nanoparticles in the tumour and therefore improve the treatment of GBM.

METHODS

PTX/SPIO PLGA nanoparticles with or without RGD-grafting were characterised. Their in vitro cellular uptake and cytotoxicity was evaluated by fluorospectroscopy and MTT assay. In vivo safety and anti-tumour efficacy of different targeting strategies were evaluated in orthotopic U87MG tumour model over multiple intravenous injections.

RESULTS

The nanoparticles of 250 nm were negatively charged. RGD targeted nanoparticles showed a specific and higher cellular uptake than untargeted nanoparticles by activated U87MG and HUVEC cells. In vitro IC50 of PTX after 48 h was ∼1 ng/mL for all the PTX-loaded nanoparticles. The median survival time of the mice treated with magnetic targeted nanoparticles was higher than the control (saline) mice or mice treated with other evaluated strategies. The 6 doses of PTX did not induce any detectable toxic effects on liver, kidney and heart when compared to Taxol.

CONCLUSION

The magnetic targeting strategy resulted in a better therapeutic effect than the other targeting strategies (passive, active).

The Current Status and Perspectives of Delivery Strategy for Boron-based Drugs

Boron-containing compounds are essential micronutrients for animals and plants despite their low-level natural occurrence. They can strengthen the cell walls of the plants and they play important role in supporting bone health. However, surprisingly, boron-containing compounds are seldom found in pharmaceutical drugs. In fact, there are no inherent disadvantages reported so far in terms of the incorporation of boron into medicines. Indeed, drugs based on boron-containing compounds, such as tavaborole (marked name Kerydin) and bortezomib (trade name Velcade) have been investigated and they are used in clinical treatment. In addition, following the advanced development of boron neutron capture therapy and a new emerging proton boron fusion therapy, more boron-containing medicinals are to be expected. This review discusses the current status and perspectives of delivery strategy for boron-containing drugs.

Optical in vivo imaging detection of preclinical models of gut tumors through the expression of integrin αVβ3

Optical imaging and Fluorescent Molecular Tomography (FMT) are becoming increasingly important for the study of different preclinical models of cancer, providing a non-invasive method for the evaluation of tumor progression in a relatively simple and fast way. Intestinal tumors, in particular colorectal cancer (CRC), represent a major cause of cancer-related death in Western countries: despite the presence of a number of preclinical models of intestinal carcinogenesis, there is a paucity of information about the possibility to detect intestinal tumors using fluorescent probes and optical in vivo imaging. Herein, we identify the detection of integrin αvβ3 by FMT and optical imaging as an effective approach to assess the occurrence and progression of intestinal carcinogenesis in genetic and chemically-induced mouse models. For this purpose, a commercially available probe (IntegriSense), recognizing integrin αvβ3, was injected in APC^+/min mice bearing small intestinal adenomas or CRC: FMT analysis allowed a specific tumor detection, further confirmed by subsequent ex vivo imaging or conventional histology. In addition, IntegriSense detection by FMT allowed the longitudinal monitoring of tumor growth. Taken together, our data indicate the possibility to use integrin αvβ3 for the visualization of intestinal tumors in preclinical models.

P1c peptide decorated liposome targeting αvβ3-expressing tumor cellsin vitroandin vivo

Integrin αvβ3 is a promising target for integrin-rich tumor and neovascular. In the present study, we prepared a doxorubicin (DOX)-loaded liposome of which the surface was decorated with PEG and a novel αvβ3 targeting peptide of P1c. The in vitro targeting efficiency was evaluated in αvβ3-positive (U87MG) and -negative (MCF-7) tumor cells by flow cytometry and laser confocal scanning microscopy. The in vivo therapeutic effects were evaluated in the glioblastoma U87MG-tumor bearing mouse model. The results indicated that the prepared liposomes showed mean sizes of 131.2 and 128.4 nm in diameter for P1c-modified targeting liposomes (P1c-DOXL) and non-targeting liposomes (DOXL), respectively. The DOX encapsulation efficiencies were more than 95% in both types of liposomes. The conjugation ratio for P1c decoration was 66.8%. The flow cytometry and confocal laser-scanning microscopy experiments consistently showed that the intracellular fluorescence intensity of the P1c-modified targeted liposome group was stronger than that of the non-targeted liposome group (P < 0.05) in U87MG cells. In vivo results revealed that compared with DOX or DOXL treatment, P1c-DOXL dramatically reduced tumor growth (P < 0.05) and tumor angiogenesis while much lower hepatotoxicity was observed. P1c-modified targeting liposome exhibited sustained release, enhancing the antitumor effect of DOX through targeting tumor cells and neovascular where integrin αvβ3 was overexpressed. The results indicated that P1c might be promising for active targeting delivery in cancer therapy.

A novel peptide of P1c decorated liposomes targets an integrin αvβ3 expressed tumor.

Hypoxia-mediated translational activation of ITGB3 in breast cancer cells enhances TGF-β signaling and malignant features in vitro and in vivo

Breast cancer is the most prevalent malignancy in women and there is an urgent need for new therapeutic drugs targeting aggressive and metastatic subtypes, such as hormone-refractory triple-negative breast cancer (TNBC). Control of protein synthesis is vital to cell growth and tumour progression and permits increased resistance to therapy and cellular stress. Hypoxic cancer cells attain invasive and metastatic properties and chemotherapy resistance, but the regulation and role of protein synthesis in this setting is poorly understood. We performed a polysomal RNA-Seq screen in non-malignant breast epithelial (MCF10A) and TNBC (MDA-MB-231) cells exposed to normoxic or hypoxic conditions and/or treated with an mTOR pathway inhibitor. Analysis of both the transcriptome and the translatome identified mRNA transcripts translationally activated or repressed by hypoxia in an mTOR-dependent or -independent manner. Integrin beta 3 (ITGB3) was translationally activated in hypoxia and its knockdown increased apoptosis and reduced survival and migration, particularly under hypoxic conditions. Moreover, ITGB3 was required for sustained TGF-β pathway activation and for the induction of Snail and associated epithelial-mesenchymal transition markers. ITGB3 downregulation significantly reduced lung metastasis and improved overall survival in mice. Collectively, these data suggest that ITGB3 is translationally activated in hypoxia and regulates malignant features, including epithelial-mesenchymal transition and cell migration, through the TGF-β pathway, revealing a novel angle for the treatment of therapy-resistant hypoxic tumours.

Nanostructured boron compounds for cancer therapy

Nanostructured boron compounds have emerged as one of the promising frontiers in boron chemistry. These species possess unique physical and chemical properties in comparison with classical small boron compounds. The nanostructured boron composites generally have large amounts of boron contents and thus have the potential to deliver significant amount of boron to the tumor cells, that is crucial for boron neutron capture therapy (BNCT). In theory, BNCT is based on a nuclear capture reaction with the 10B isotope absorbing a slow neutron to initiate a nuclear fission reaction with the release of energetic particles, such as lithium and helium (α particles), which travel the distance of around nine microns within the cell DNA or RNA to destroy it. The recent studies have demonstrated that the nanostructured boron composites can be combined with the advanced targeted drug delivery system and drug detection technology. The successful combination of these three areas should significantly improve the BNCT in cancer treatment. This mini review summarizes the latest developments in this unique area of cancer therapy.

Nano-sized and other improved reporters for magnetic resonance imaging of angiogenesis

Magnetic Resonance Imaging (MRI) enables to provide anatomical, functional and molecular information of pathological angiogenesis when used with properly tailored imaging probes. Functional studies have been the domain of Dynamic Contrast Enhancement (DCE) -MRI protocols from which it is possible to extract quantitative estimations on key parameters such as the volumes of vascular and extracellular compartments and the rates of the bidirectional exchange of the imaging reporters across the endothelial barrier. Whereas paramagnetic Gd-complexes able to reversibly bind to serum albumin act better than the clinically used small-sized, hydrophilic species, new findings suggest that an accurate assessment of the vascular volume is possible by analyzing images acquired upon the i.v. administration of Gd-labelled Red Blood Cells (RBCs). As far as it concerns molecular MRI, among the many available biomarkers, α_vβ₃ integrins are the most investigated ones. The low expression of these targets makes mandatory the use of nano-sized systems endowed with the proper signal enhancing capabilities. A number of targeted nano-particles have been investigated including micelles, liposomes, iron oxides and perfluorocarbon containing systems. Finally, a growing attention is devoted to the design and testing of "theranostic" agents based on the exploitation of MRI to monitor drug delivery processes and therapeutic outcome.