Combating Established Mouse Glioblastoma through Nicotinylated-Liposomes-Mediated Targeted Chemotherapy in Combination with Dendritic-Cell-Based Genetic Immunization

Drug Delivery to the Brain: Recent Advances and Unmet Challenges

Brain cancers and neurodegenerative diseases are on the rise, treatments for central nervous system (CNS) diseases remain limited. Despite the significant advancement in drug development technology with emerging biopharmaceuticals like gene therapy or recombinant protein, the clinical translational rate of such biopharmaceuticals to treat CNS disease is extremely poor. The blood-brain barrier (BBB), which separates the brain from blood and protects the CNS microenvironment to maintain essential neuronal functions, poses the greatest challenge for CNS drug delivery. Many strategies have been developed over the years which include local disruption of BBB via physical and chemical methods, and drug transport across BBB via transcytosis by targeting some endogenous proteins expressed on brain-capillary. Drug delivery to brain is an ever-evolving topic, although there were multiple review articles in literature, an update is warranted due to continued growth and new innovations of research on this topic. Thus, this review is an attempt to highlight the recent strategies employed to overcome challenges of CNS drug delivery while emphasizing the necessity of investing more efforts in CNS drug delivery technologies parallel to drug development.

In vivo targeting of a tumor-antigen encoded DNA vaccine to dendritic cells in combination with tumor-selective chemotherapy eradicates established mouse melanoma

Despite remarkable progress during the past decade, eradication of established tumors by targeted cancer therapy and cancer immunotherapy remains an uphill task. Herein, we report on a combination approach for eradicating established mouse melanoma. Our approach employs the use of tumor selective chemotherapy in combination with in vivo dendritic cell (DC) targeted DNA vaccination. Liposomes of a newly synthesized lipopeptide containing a previously reported tumor-targeting CGKRK-ligand covalently grafted in its polar head-group region were used for tumor selective delivery of cancer therapeutics. Liposomally co-loaded STAT3siRNA and WP1066 (a commercially available inhibitor of the JAK2/STAT3 pathway) were used as cancer therapeutics. In vivo targeting of a melanoma antigen (MART-1) encoded DNA vaccine (p-CMV-MART1) to dendritic cells was accomplished by complexing it with a previously reported mannose-receptor selective in vivo DC-targeting liposome. Liposomes of the CGKRK-lipopeptide containing encapsulated FITC-labeled siRNA, upon intravenous administration in B16F10 melanoma bearing mice, showed remarkably higher accumulation in tumors 24 h post i.v. treatment, compared to their degree of accumulation in other body tissues including the lungs, liver, kidneys, spleen and heart. Importantly, the findings in tumor growth inhibition studies revealed that only in vivo DC-targeted genetic immunization or only tumor-selective chemotherapy using the presently described systems failed to eradicate the established mouse melanoma. The presently described combination approach is expected to find future applications in combating various malignancies (with well-defined surface antigens).

Current Status of Research on Targeted Therapy Against Central Nervous System Tumors in Low- and Lower-Middle-Income Countries

OBJECTIVE

In recent decades, a significant body of research has focused on targeted therapies for the treatment of central nervous system (CNS) tumors to enhance the effectiveness of management strategies. However, most of these efforts have been centered in high-income countries, which renders the generalizability of their results to low- and middle-income countries questionable. Therefore, in this review, we systematically investigated the status of research conducted on targeted therapy for CNS tumors in low- and lower-middle-income countries to elucidate the contribution of these countries in advancing neuro-oncology.

METHODS

A systematic search of 3 databases was performed using a predefined search strategy. After screening the articles based on our inclusion/exclusion criteria, the data were extracted to a predesigned Excel worksheet.

RESULTS

A review of 44 included studies showed that India, Iran, and Lebanon were the only countries with a contribution to this field. All included studies were laboratory or animal experiments, and there were no clinical studies in this field. The most investigated CNS tumor was malignant glioma, and gene-targeted therapy was the most investigated category of targeted therapies in these countries.

CONCLUSIONS

Low- and lower-middle-income countries comprise more than half of the world population, but they are deprived of targeted therapies against CNS tumors. Although there are basic experiments performed on this subject, they originate in a limited number of these countries. Therefore, targeted therapy is in its preliminary stage in these countries.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

"Targeting Design" of Nanoparticles in Tumor Therapy

Tumor-targeted therapy based on nanoparticles is a popular research direction in the biomedical field. After decades of research and development, both the passive targeting ability of the inherent properties of NPs and the active targeting based on ligand receptor interaction have gained deeper understanding. Unfortunately, most targeted delivery strategies are still in the preclinical trial stage, so it is necessary to further study the biological fate of particles in vivo and the interaction mechanism with tumors. This article reviews different targeted delivery strategies based on NPs, and focuses on the physical and chemical properties of NPs (size, morphology, surface and intrinsic properties), ligands (binding number/force, activity and species) and receptors (endocytosis, distribution and recycling) and other factors that affect particle targeting. The limitations and solutions of these factors are further discussed, and a variety of new targeting schemes are introduced, hoping to provide guidance for future targeting design and achieve the purpose of rapid transformation of targeted particles into clinical application.

Nucleic acid-based therapy for brain cancer: Challenges and strategies

Nucleic acid-based therapy emerges as a powerful weapon for the treatment of tumors thanks to its direct, effective, and lasting therapeutic effect. Encouragingly, continuous nucleic acid-based drugs have been approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Despite the tremendous progress, there are few nucleic acid-based drugs for brain tumors in clinic. The most challenging problems lie on the instability of nucleic acids, difficulty in traversing the biological barriers, and the off-target effect. Herein, nucleic acid-based therapy for brain tumor is summarized considering three aspects: (i) the therapeutic nucleic acids and their applications in clinical trials; (ii) the various administration routes for nucleic acid delivery and the respective advantages and drawbacks. (iii) the strategies and carriers for improving stability and targeting ability of nucleic acid drugs. This review provides thorough knowledge for the rational design of nucleic acid-based drugs against brain tumor.

A Nanoparticle's Journey to the Tumor: Strategies to Overcome First-Pass Metabolism and Their Limitations

Simple Summary

Traditional cancer therapeutics suffer from off-target toxicity, limiting their effective dose and preventing patients’ tumors from being sufficiently treated by chemotherapeutics alone. Nanomedicine is an emerging class of therapeutics in which a drug is packaged into a nanoparticle that promotes uptake of the drug at a tumor site, shielding it from uptake by peripheral organs and enabling the safe delivery of chemotherapeutics that have poor aqueous solubility, short plasma half-life, narrow therapeutic window, and toxic side effects. Despite the advantages of nanomedicines for cancer, there remains significant challenges to improve uptake at the tumor and prevent premature clearance from the body. In this review, we summarize the effects of first-pass metabolism on a nanoparticle’s journey to a tumor and outline future steps that we believe will improve the efficacy of cancer nanomedicines.

Abstract

Nanomedicines represent the cutting edge of today’s cancer therapeutics. Seminal research decades ago has begun to pay dividends in the clinic, allowing for the delivery of cancer drugs with enhanced systemic circulation while also minimizing off-target toxicity. Despite the advantages of delivering cancer drugs using nanoparticles, micelles, or other nanostructures, only a small fraction of the injected dose reaches the tumor, creating a narrow therapeutic window for an otherwise potent drug. First-pass metabolism of nanoparticles by the reticuloendothelial system (RES) has been identified as a major culprit for the depletion of nanoparticles in circulation before they reach the tumor site. To overcome this, new strategies, materials, and functionalization with stealth polymers have been developed to improve nanoparticle circulation and uptake at the tumor site. This review summarizes the strategies undertaken to evade RES uptake of nanomedicines and improve the passive and active targeting of nanoparticle drugs to solid tumors. We also outline the limitations of current strategies and the future directions we believe will be explored to yield significant benefits to patients and make nanomedicine a promising treatment modality for cancer.

Recent Advances in the Use of Lipid-Based Nanoparticles Against Glioblastoma Multiforme

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor in adults. Although the overall incidence is less than 10 per 100,000 individuals, its poor prognosis and low survival rate make GBM a crucial public health issue. The main challenges for GBM treatment are related to tumor location and its complex and heterogeneous biology. In this sense, a broad range of nanoparticles with different sizes, architectures, and surface properties, have been engineered as brain drug delivery systems. Among them, lipid-based nanoparticles, such as liposomes, have been pointed out as promising materials to deliver antitumoral drugs to the central nervous system and thus, to improve brain drug targeting and therapeutic efficiency. Here, we describe the synthesis and general characteristics of lipid-based nanoparticles, as well as evidence in the past 5 years regarding their potential use to treat GBM.

Advances in histone deacetylase inhibitors in targeting glioblastoma stem cells

Glioblastoma multiforme (GBM) is a lethal grade IV glioma (WHO classification) and widely prevalent primary brain tumor in adults. GBM tumors harbor cellular heterogeneity with the presence of a small subpopulation of tumor cells, described as GBM cancer stem cells (CSCs) that pose resistance to standard anticancer regimens and eventually mediate aggressive relapse or intractable progressive GBM. Existing conventional anticancer therapies for GBM do not target GBM stem cells and are mostly palliative; therefore, exploration of new strategies to target stem cells of GBM has to be prioritized for the development of effective GBM therapy. Recent developments in the understanding of GBM pathophysiology demonstrated dysregulation of epigenetic mechanisms along with the genetic changes in GBM CSCs. Altered expression/activity of key epigenetic regulators, especially histone deacetylases (HDACs) in GBM stem cells has been associated with poor prognosis; inhibiting the activity of HDACs using histone deacetylase inhibitors (HDACi) has been promising as mono-therapeutic in targeting GBM and in sensitizing GBM stem cells to an existing anticancer regimen. Here, we review the development of pan/selective HDACi as potential anticancer agents in targeting the stem cells of glioblastoma as a mono or combination therapy.

Combating Glioblastoma by Codelivering the Small-Molecule Inhibitor of STAT3 and STAT3siRNA with α5β1 Integrin Receptor-Selective Liposomes

Glioblastoma multiforme (GBM) is one of the most aggressive tumors with a median survival of only 15 months. Effective therapeutics need to overcome the formidable challenge of crossing the blood-brain barrier (BBB). Receptors and transporters overexpressed on BCECs are being used for designing liposomes, polymers, polymeric micelles, peptides, and dendrimer-based drug carriers for combating brain tumors. Herein, using the orthotopic mouse glioblastoma model, we show that codelivering a small-molecule inhibitor of the JAK/STAT pathway (WP1066) and STAT3siRNA with nanometric (100-150 nm) α5β1 integrin receptor-selective liposomes of RGDK-lipopeptide holds therapeutic promise in combating glioblastoma. Rh-PE (red)-labeled liposomes of RGDK-lipopeptide were found to be internalized in GL261 cells via integrin α5β1 receptors. Intravenously administered near-infrared (NIR)-dye-labeled α5β1 integrin receptor-selective liposomes of RGDK-lipopeptide were found to be accumulated preferentially in the mouse brain tumor tissue. Importantly, we show that iv injection of WP1066 (a commercially sold small-molecule inhibitor of the JAK/STAT pathway) and STAT3siRNA cosolubilized within the liposomes of RGDK-lipopeptide leads to significant inhibition (>350% compared to the untreated mice group) of orthotopically growing mouse glioblastoma. The present strategy may find future use in combating GBM.

Amphetamine decorated cationic lipid nanoparticles cross the blood-brain barrier: therapeutic promise for combating glioblastoma

Combating brain tumors (glioblastoma multiforme or GBM) is a formidable challenge because of the existence of blood-brain barrier (BBB), a tight cellular junction that separates the central nervous system (CNS) and systemic circulation. Such a selectively permeable barrier prevents the entry of therapeutic molecules from blood circulation to brain parenchyma. Towards enhancing the efficacy of brain tumor-selective drug delivery without perturbing the BBB integrity, nanometric drug carriers are increasingly becoming an efficient therapeutic modality in preclinical studies. Psychostimulant drugs such as amphetamine and methylated amphetamine (METH) are known to penetrate the BBB. Still, little effort has been made to exploit them in nano-drug delivery, largely due to their toxicities. Herein, for the first time, we design, synthesize, and formulate three different β-amphetaminylated cationic lipid nanoparticles. We show that the β-amphetaminylated cationic lipid nanoparticles are nontoxic and can cross the BBB presumably through active transcytosis. The BBB penetrating ability also depends on the hydrophilic-hydrophobic balance of the lipids, with hexadecyl lipid (16-BACL) nanoparticle showing maximum accumulation in the brain. The lipid nanoparticle of 16-BACL can simultaneously encapsulate paclitaxel and PDL1-siRNA. The dual drug-loaded lipid nanoparticles showed apoptosis driven cellular cytotoxicity against GL261 cells and improved the overall survivability of orthotopic glioblastoma bearing mice compared to their non-targeting counterpart. The present work describes a new class of BBB-crossing lipid nanoparticles and delineates their therapeutic promise against glioblastoma.

Au-CGKRK Nanoconjugates for Combating Cancer through T-Cell-Driven Therapeutic RNA Interference

Numerous prior studies on fighting cancer have been based on using inhibitors of JAK-STAT pathway (signal transducer and activator of transcription 3 (STAT3) inhibitor in particular), a signaling pathway responsible for progression of many types of cancer cells. However, recent studies have shown that STAT3 activation leads to upregulation of program death receptor-ligand 1 (PD-L1, an immune checkpoint protein that plays a major role behind evasion of immune systems by growing tumors) expression levels in tumor cells, leading to enhanced immune suppression. This is why global efforts are being witnessed in combating cancer through use of immune checkpoint inhibitors. Herein, we report on the design, synthesis, physicochemical characterizations, and bioactivity evaluation of novel tumor- and tumor-vasculature-targeting noncytotoxic Au-CGKRK nanoconjugates (17-80 nm) for combating tumor. Using a syngeneic mouse tumor model, we show that intraperitoneal (i.p.) administration of the Au-CGKRK nanoparticles (NPs) complexed with both PD-L1siRNA (the immune checkpoint inhibitor) and STAT3siRNA (the JAK-STAT pathway inhibitor) results in significant (>70%) enhancement in overall survivability (OS) in melanoma-bearing mice (n = 5) when compared to the OS in the untreated mice group. The expression levels of CD8 and CD4 proteins in the tumor lysates of differently treated mice groups (by Western blotting) are consistent with the observed OS enhancement being a T-cell-driven process. Biodistribution study using near-infrared dye-loaded Au-CGKRK nanoconjugates revealed selective accumulation of the dye in mouse tumor. Notably, the overall survival benefits were significantly less (∼35%) when melanoma-bearing mice were treated (i.p.) with Au-CGKRK NPs complexed with only PD-L1siRNA or with STAT3siRNA alone. The presently described Au-CGKRK nanoconjugates are expected to find future use in therapeutic RNA-interference-based cancer immunotherapy.

Large Amino Acid Transporter 1 Selective Liposomes of l-DOPA Functionalized Amphiphile for Combating Glioblastoma

Despite significant progress in neurosurgery and radiation therapy during the past decade, overall survivability (OS) of glioblastoma patients continues to be less than 2 years. The scope of systemic chemotherapy is greatly limited by poor drug transport across the blood brain barrier (BBB) and, thereby, suboptimal drug accumulation in glioma tissue. To this end, use of large amino acid transporter-1 (LAT1) overexpressed both on brain capillary endothelial cells (BCECs) and glioma cells has begun. Prior reports on the use of LAT1 mediated delivery of model drugs showed their brain accumulations. However, in depth in vivo glioblastoma regression studies aimed at examining the therapeutic potential of LAT1 mediated delivery of potent chemotherapeutics to brain tumor tissues have not yet been undertaken. Herein, we report on the development of a nanometric (100-135 nm) promising LAT1 selective liposomal drug carrier prepared from a novel l-3,4-dihydroxyphenylalanine (l-DOPA) functionalized amphiphile (Amphi-DOPA). In vitro studies using Rh-PE labeled liposomes of Amphi-DOPA both in untreated glioma (GL261) cells and in GL261cells preincubated with LAT1 antibody revealed LAT1 mediated cellular uptake. Intravenously administered NIR-dye labeled liposomes of Amphi-DOPA in glioblastoma-bearing mice showed preferential accumulation of the dye in brain tissue. Notably iv administration of WP1066-loaded liposomes of Amphi-DOPA enhanced the overall survivability of C57BL/6J mice bearing orthotopically established mouse glioblastoma by ∼60% compared to that for the untreated mouse group. Furthermore, we show that the OS of established glioblastoma-bearing mice can be significantly enhanced (by >300% compared to that for the untreated mouse group) when the presently described LAT1 mediated targeted chemotherapy with WP1066-loaded liposomes of Amphi-DOPA is combined with in vivo DC-targeted DNA vaccination using a survivin (a glioblastoma antigen) encoded DNA vaccine. The present findings open a new door for LAT1 mediated systemic chemotherapy of glioblastoma.