Small, Smart, and LDLR-Specific Micelles Augment Sorafenib Therapy of Glioblastoma

Bioresponsive Polymeric Nanoparticles: From Design, Targeted Therapy to Cancer Immunotherapy

Bioresponsive polymeric nanoparticles (NPs) that are capable of delivering and releasing therapeutics and biotherapeutics to target sites have attracted vivid interest in cancer therapy and immunotherapy. In contrast to enthusiastic evolution in the academic world, the clinical translation of these smart systems is scarce, partly due to concerns about safety, stability, complexity, and scalability. The moderate targetability, responsivity, and benefits are other concerns. In the past 17 years, we have devoted ourselves to exploring elegant strategies to address the above basic and translational problems by introducing diverse functional groups and/or targeting ligands to safe biomedical materials, such as biodegradable polymers and water-soluble polymers. This minimal modification is critical for further clinical translation. We have tailor-made various bioresponsive NPs including shell-sheddable and/or acid-sensitive biodegradable NPs, disulfide-cross-linked biodegradable micelles and polymersomes, and blood-brain barrier (BBB)-permeable NPs, to target different tumors. This perspective provides an overview of our work path toward targeted nanomedicines and personalized vaccines, which might inspire clinical translation and future research on cancer therapy.

The multifaceted therapeutical role of low-density lipoprotein receptor family in high-grade glioma

The diverse roles of the low-density lipoprotein receptor family (LDLR) have been associated with many processes critical to maintaining central nervous system (CNS) health and contributing to neurological diseases or cancer. In this review, we provide a comprehensive understanding of the LDLR's involvement in common brain tumors, specifically high-grade gliomas, emphasizing the receptors' critical role in the pathophysiology and progression of these tumors due to LDLR's high expression. We delve into LDLR's role in regulating cellular uptake and transport through the brain barrier. Additionally, we highlight LDLR's role in activating several signaling pathways related to tumor proliferation, migration, and invasion, engaging readers with an in-depth understanding of the molecular mechanisms at play. By synthesizing current research findings, this review underscores the significance of LDLR during tumorigenesis and explores its potential as a therapeutic target for high-grade gliomas. The collective insights presented here contribute to a deeper appreciation of LDLR's multifaceted roles and implications for physiological and pathological states, opening new avenues for tumor treatment.

Stimuli-Responsive Polymeric Nanocarriers Accelerate On-Demand Drug Release to Combat Glioblastoma

Glioblastoma multiforme (GBM) is a highly malignant brain tumor with a poor prognosis and limited treatment options. Drug delivery by stimuli-responsive nanocarriers holds great promise for improving the treatment modalities of GBM. At the beginning of the review, we highlighted the stimuli-active polymeric nanocarriers carrying therapies that potentially boost anti-GBM responses by employing endogenous (pH, redox, hypoxia, enzyme) or exogenous stimuli (light, ultrasonic, magnetic, temperature, radiation) as triggers for controlled drug release mainly via hydrophobic/hydrophilic transition, degradability, ionizability, etc. Modifying these nanocarriers with target ligands further enhanced their capacity to traverse the blood-brain barrier (BBB) and preferentially accumulate in glioma cells. These unique features potentially lead to more effective brain cancer treatment with minimal adverse reactions and superior therapeutic outcomes. Finally, the review summarizes the existing difficulties and future prospects in stimuli-responsive nanocarriers for treating GBM. Overall, this review offers theoretical guidelines for developing intelligent and versatile stimuli-responsive nanocarriers to facilitate precise drug delivery and treatment of GBM in clinical settings.

Current Non-Metal Nanoparticle-Based Therapeutic Approaches for Glioblastoma Treatment

The increase in the variety of nano-based tools offers new possibilities to approach the therapy of poorly treatable tumors, which includes glioblastoma multiforme (GBM; a primary brain tumor). The available nanocomplexes exhibit great potential as vehicles for the targeted delivery of anti-GBM compounds, including chemotherapeutics, nucleic acids, and inhibitors. The main advantages of nanoparticles (NPs) include improved drug stability, increased penetration of the blood-brain barrier, and better precision of tumor targeting. Importantly, alongside their drug-delivery ability, NPs may also present theranostic properties, including applications for targeted imaging or photothermal therapy of malignant brain cells. The available NPs can be classified into two categories according to their core, which can be metal or non-metal based. Among non-metal NPs, the most studied in regard to GBM treatment are exosomes, liposomes, cubosomes, polymeric NPs, micelles, dendrimers, nanogels, carbon nanotubes, and silica- and selenium-based NPs. They are characterized by satisfactory stability and biocompatibility, limited toxicity, and high accumulation in the targeted tumor tissue. Moreover, they can be easily functionalized for the improved delivery of their cargo to GBM cells. Therefore, the non-metal NPs discussed here, offer a promising approach to improving the treatment outcomes of aggressive GBM tumors.

CXCR4-Mediated Codelivery of FLT3 and BCL-2 Inhibitors for Enhanced Targeted Combination Therapy of FLT3-ITD Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is often associated with poor prognosis and survival. Small molecule inhibitors, though widening the treatment landscape, have limited monotherapy efficacy. The combination therapy, however, shows suboptimal clinical outcomes due to low bioavailability, overlapping systemic toxicity and drug resistance. Here, we report that CXCR4-mediated codelivery of the BCL-2 inhibitor venetoclax (VEN) and the FLT3 inhibitor sorafenib (SOR) via T22 peptide-tagged disulfide cross-linked polymeric micelles (TM) achieves synergistic treatment of FLT3-ITD AML. TM-VS with a VEN/SOR weight ratio of 1/4 and T22 peptide density of 20% exhibited an extraordinary inhibitory effect on CXCR4-overexpressing MV4-11 AML cells. TM-VS at a VEN/SOR dosage of 2.5/10 mg/kg remarkably reduced leukemia burden, prolonged mouse survival, and impeded bone loss in orthotopic MV4-11-bearing mice, outperforming the nontargeted M-VS and oral administration of free VEN/SOR. CXCR4-mediated codelivery of BCL-2 and FLT3 inhibitors has emerged as a prospective clinical treatment for FLT3-ITD AML.

Peptide-Hitchhiking for the Development of Nanosystems in Glioblastoma

Glioblastoma (GBM) remains the epitome of aggressiveness and lethality in the spectrum of brain tumors, primarily due to the blood-brain barrier (BBB) that hinders effective treatment delivery, tumor heterogeneity, and the presence of treatment-resistant stem cells that contribute to tumor recurrence. Nanoparticles (NPs) have been used to overcome these obstacles by attaching targeting ligands to enhance therapeutic efficacy. Among these ligands, peptides stand out due to their ease of synthesis and high selectivity. This article aims to review single and multiligand strategies critically. In addition, it highlights other strategies that integrate the effects of external stimuli, biomimetic approaches, and chemical approaches as nanocatalytic medicine, revealing their significant potential in treating GBM with peptide-functionalized NPs. Alternative routes of parenteral administration, specifically nose-to-brain delivery and local treatment within the resected tumor cavity, are also discussed. Finally, an overview of the significant obstacles and potential strategies to overcome them are discussed to provide a perspective on this promising field of GBM therapy.

Understanding the Role of Endothelial Cells in Glioblastoma: Mechanisms and Novel Treatments

Glioblastoma is a highly aggressive neoplasm and the most common primary malignant brain tumor. Endothelial tissue plays a critical role in glioblastoma growth and progression, facilitating angiogenesis, cellular communication, and tumorigenesis. In this review, we present an up-to-date and comprehensive summary of the role of endothelial cells in glioblastomas, along with an overview of recent developments in glioblastoma therapies and tumor endothelial marker identification.

Integrin-targeting disulfide-crosslinked micellar docetaxel eradicates lung and prostate cancer patient-derived xenografts

Actively targeted nanomedicines though conceptually attractive for tumor therapy are extremely hard to realize due to problems of premature drug leakage, excessive liver accretion, inadequate tumor uptake, and/or retarded drug release inside tumor cells. Here, we systemically studied the influence of disulfide crosslinking on the in vitro and in vivo performance of integrin-targeting micellar docetaxel (t-MDTX). Of note, t-M5DTX with a high disulfide content was clearly advantageous in terms of stability, intracellular drug release, anti-tumor activity toward αVβ3-overexpressing A549 cells, blood circulation and therapeutic efficacy in orthotopic A549-luc lung tumor-bearing mice. t-MDTX induced extraordinary tumor targetability with tumor-to-normal tissue ratios of 1.7-8.3. Further studies indicated that t-M5DTX could effectively eradicate αVβ3-overexpressing lung and prostate cancer patient-derived xenografts (PDX), in which ca. 80% mice became tumor-free. This integrin-targeting disulfide-crosslinked micellar docetaxel emerges as a promising actively targeted nanoformulation for tumor therapy. STATEMENT OF SIGNIFICANCE: Nanomedicines have a great potential in treating advanced tumor patients; however, their tumor-targeting ability and therapeutic efficacy remain unsatisfactory. In addition to PEGylation and ligand selection, particle size, stability and drug release behavior are also critical to their performance in vivo. In this paper, we find that small and cRGD-guided disulfide-crosslinked micellar docetaxel (t-MDTX) induces superior tumor uptake and retention but without increasing liver burden, leading to extraordinary selectivity and inhibition of αvβ3 overexpressing lung tumors. t-MDTX is further shown to effectively treat αvβ3-positive patient-derived tumor models, lending it a high potential for clinical translation.

RGD-directed 24 nm micellar docetaxel enables elevated tumor-liver ratio, deep tumor penetration and potent suppression of solid tumors

Nanomedicines while showing a great potential in improving the performance of chemotherapeutics like docetaxel (DTX) are distressed by a high liver deposition and poor tumor penetration, which might not only cause liver toxicity but also moderate therapeutic effect. Herein, we report that cRGD-directed 24 nm disulfide-crosslinked micellar docetaxel (cRGD-MDTX) presents low liver accumulation, high tumor uptake, and deep tumor penetration, leading to the potent suppression of different solid tumors. cRGD-MDTX was optimized with a cRGD density of 4% and DTX loading of 10 wt%. Interestingly, cRGD-MDTX enabled an extraordinary tumor-liver ratio of 2.8/1 with a DTX uptake of 8.3 %ID/g in αvβ3 over-expressing PC3 prostate tumor. The therapeutic studies demonstrated striking antitumor effects of cRGD-MDTX toward PC3 prostate tumor, prostate cancer patient-derived xenografts (PDX), orthotopic A549-Luc lung cancer and orthotopic SKOV3-Luc ovarian tumor models, in which tumor growth was effectually inhibited and 6-8 times better improvement of median survival time over free DTX was observed. This small disulfide-crosslinked micellar drug capable of relegating liver deposition opens a new avenue to nanomedicines for targeted therapy.

Functionalized nanoparticles crossing the brain-blood barrier to target glioma cells

Glioma is the most common tumor of the central nervous system (CNS), with a 5-year survival rate of <35%. Drug therapy, such as chemotherapeutic and immunotherapeutic agents, remains one of the main treatment modalities for glioma, including temozolomide, doxorubicin, bortezomib, cabazitaxel, dihydroartemisinin, immune checkpoint inhibitors, as well as other approaches such as siRNA, ferroptosis induction, etc. However, the filter function of the blood-brain barrier (BBB) reduces the amount of drugs needed to effectively target CNS tumors, making it one of the main reasons for poor drug efficacies in glioma. Thus, finding a suitable drug delivery platform that can cross the BBB, increase drug aggregation and retainment in tumoral areas and avoid accumulation in non-targeted areas remains an unsolved challenge in glioma drug therapy. An ideal drug delivery system for glioma therapy should have the following features: (1) prolonged drug life in circulation and effective penetration through the BBB; (2) adequate accumulation within the tumor (3) controlled-drug release modulation; (4) good clearance from the body without significant toxicity and immunogenicity, etc. In this regard, due to their unique structural features, nanocarriers can effectively span the BBB and target glioma cells through surface functionalization, providing a new and effective strategy for drug delivery. In this article, we discuss the characteristics and pathways of different nanocarriers for crossing the BBB and targeting glioma by listing different materials for drug delivery platforms, including lipid materials, polymers, nanocrystals, inorganic nanomaterials, etc.

Advances in antibody-based drugs and their delivery through the blood-brain barrier for targeted therapy and immunotherapy of gliomas

Gliomas are highly invasive and are the most common type of primary malignant brain tumor. The routine treatments for glioma include surgical resection, radiotherapy, and chemotherapy. However, glioma recurrence and patient survival remain unsatisfactory after employing these traditional treatment approaches. With the rapid development of molecular immunology, significant breakthroughs have been made in targeted glioma therapy and immunotherapy. Antibody-based therapy has excellent advantages in treating gliomas due to its high specificity and sensitivity. This article reviewed various targeted antibody drugs for gliomas, including anti-glioma surface marker antibodies, anti-angiogenesis antibodies, and anti-immunosuppressive signal antibodies. Notably, many antibodies have been validated clinically, such as bevacizumab, cetuximab, panitumumab, and anti-PD-1 antibodies. These antibodies can improve the targeting of glioma therapy, enhance anti-tumor immunity, reduce the proliferation and invasion of glioma, and thus prolong the survival time of patients. However, the existence of the blood-brain barrier (BBB) has caused significant difficulties in drug delivery for gliomas. Therefore, this paper also summarized drug delivery methods through the BBB, including receptor-mediated transportation, nano-based carriers, and some physical and chemical methods for drug delivery. With these exciting advancements, more antibody-based therapies will likely enter clinical practice and allow more successful control of malignant gliomas.

Tyrosine Kinase Inhibitors for Glioblastoma Multiforme: Challenges and Opportunities for Drug Delivery

Glioblastoma multiforme (GBM) is an aggressive brain tumor with high mortality rates. Due to its invasiveness, heterogeneity, and incomplete resection, the treatment is very challenging. Targeted therapies such as tyrosine kinase inhibitors (TKIs) have great potential for GBM treatment, however, their efficacy is primarily limited by poor brain distribution due to the presence of the blood-brain barrier (BBB). This review focuses on the potential of TKIs in GBM therapy and provides an insight into the reasons behind unsuccessful clinical trials of TKIs in GBM despite the success in treating other cancer types. The main section is dedicated to the use of promising drug delivery strategies for targeted delivery to brain tumors. Use of brain targeted delivery strategies can help enhance the efficacy of TKIs in GBM. Among various drug delivery approaches used to bypass or cross BBB, utilizing nanocarriers is a promising strategy to augment the pharmacokinetic properties of TKIs and overcome their limitations. This is because of their advantages such as the ability to cross BBB, chemical stabilization of drug in circulation, passive or active targeting of tumor, modulation of drug release from the carrier, and the possibility to be delivered via non-invasive intranasal route.

Near infrared-activatable biomimetic nanogels enabling deep tumor drug penetration inhibit orthotopic glioblastoma

Glioblastoma multiforme (GBM) is one of the most fatal malignancies due to the existence of blood-brain barrier (BBB) and the difficulty to maintain an effective drug accumulation in deep GBM lesions. Here we present a biomimetic nanogel system that can be precisely activated by near infrared (NIR) irradiation to achieve BBB crossing and deep tumor penetration of drugs. Synthesized by crosslinking pullulan and poly(deca-4,6-diynedioic acid) (PDDA) and loaded with temozolomide and indocyanine green (ICG), the nanogels are inert to endogenous oxidative conditions but can be selectively disintegrated by ICG-generated reactive oxygen species upon NIR irradiation. Camouflaging the nanogels with apolipoprotein E peptide-decorated erythrocyte membrane further allows prolonged blood circulation and active tumor targeting. The precisely controlled NIR irradiation on tumor lesions excites ICG and deforms the cumulated nanogels to trigger burst drug release for facilitated BBB permeation and infiltration into distal tumor cells. These NIR-activatable biomimetic nanogels suppress the tumor growth in orthotopic GBM and GBM stem cells-bearing mouse models with significantly extended survival.

Phenylboronic Acid-Functionalized Copolypeptides: Facile Synthesis and Responsive Dual Anticancer Drug Release

The incorporation of a phenylboronic acid group has appeared as an attractive strategy to build smart drug delivery systems. Here, we report novel synthesis of phenylboronic acid-functionalized copolypeptides based on an l-boronophenylalanine N-carboxyanhydride (BPA-NCA) monomer and their application for robust co-encapsulation and responsive release of dual anticancer drugs. By employing different poly(ethylene glycol) (PEG) initiators and copolymerizing with varying NCA monomers, linear and star PEG-poly(l-boronophenylalanine) copolymers (PEG-PBPA, star-PEG-PBPA), PEG-poly(l-tyrosine-co-l-boronophenylalanine) [PEG-P(Tyr-co-BPA)], PEG-poly(l-lysine-co-l-boronophenylalanine) [PEG-P(Lys-co-BPA)], and PEG-poly(β-benzyl-l-aspartate-co-l-boronophenylalanine) [PEG-P(BLA-co-BPA)] were obtained with controlled compositions. Interestingly, PEG-PBPA self-assembled into uniform micellar nanoparticles that mediated robust co-encapsulation and hydrogen peroxide (H₂O₂) and acid-responsive release of dual antitumor drugs, curcumin (Cur) and sorafenib tosylate (Sor). These dual drug-loaded nanoparticles (PBN-Cur/Sor) exhibited a greatly enhanced anticancer effect toward U87 MG-luciferase glioblastoma cells. The facile synthesis of phenylboronic acid-functionalized copolypeptides from BPA coupled with their robust drug loading and responsive drug release behaviors make them interesting for construction of smart cancer nanomedicines.

Introducing SuFEx click chemistry into aliphatic polycarbonates: a novel toolbox/platform for post-modification as biomaterials

As a biodegradable and biocompatible biomaterial, aliphatic polycarbonates (APCs) have attracted substantial attention in terms of post-polymerization modification (PPM) for functionalization. A strategy for the introduction of sulfur(VI)-fluoride exchange (SuFEx) click chemistry into APCs for PPM is proposed for the first time in this work. 4'-(Fluorosulfonyl)benzyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (FMC) was designed as a SuFEx clickable cyclic carbonate for APCs via ring-opening polymerization (ROP), and an operational and nontoxic synthetic route was achieved. FMC managed to undergo both ROP and PPM through the SuFEx click chemistry organocatalytically without constraining or antagonizing each other, using 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) as a co-organocatalyst here. Its ROP was systematically investigated, and density functional theory (DFT) calculations were performed to understand the acid-base catalytic mechanism in the anionic ROP. Exploratory investigations into PPM by SuFEx of poly(FMC) were conducted as biomaterials, and the one-pot strategies to achieve both ROP and SuFEx were confirmed.