GRP78 enabled micelle-based glioma targeted drug delivery

Recent progress in stimuli-responsive polymeric micelles for targeted delivery of functional nanoparticles

Stimuli-responsive polymeric micelles have emerged as a revolutionary approach for enhancing the in vivo stability, biocompatibility, and targeted delivery of functional nanoparticles (FNPs) in biomedicine. This article comprehensively reviews the preparation methods of these polymer micelles, detailing the innovative strategies employed to introduce stimulus responsiveness and surface modifications essential for precise targeting. We delve into the breakthroughs in utilizing these micelles to selectively deliver various FNPs including magnetic nanoparticles, upconversion nanoparticles, gold nanoparticles, and quantum dots, highlighting their transformative impact in the biomedical realm. Concluding, we present an insight into the current research landscape, addressing the challenges at hand, and envisioning the future trajectory in this burgeoning domain. Join us as we navigate the exciting confluence of polymer science and nanotechnology in reshaping biomedical solutions.

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.

New insights into targeted therapy of glioblastoma using smart nanoparticles

In recent times, the intersection of nanotechnology and biomedical research has given rise to nanobiomedicine, a captivating realm that holds immense promise for revolutionizing diagnostic and therapeutic approaches in the field of cancer. This innovative fusion of biology, medicine, and nanotechnology aims to create diagnostic and therapeutic agents with enhanced safety and efficacy, particularly in the realm of theranostics for various malignancies. Diverse inorganic, organic, and hybrid organic-inorganic nanoparticles, each possessing unique properties, have been introduced into this domain. This review seeks to highlight the latest strides in targeted glioblastoma therapy by focusing on the application of inorganic smart nanoparticles. Beyond exploring the general role of nanotechnology in medical applications, this review delves into groundbreaking strategies for glioblastoma treatment, showcasing the potential of smart nanoparticles through in vitro studies, in vivo investigations, and ongoing clinical trials.

Synthesis and Evaluation of [18F]AlF-NOTA-c-DVAP: A Novel PET Probe for Imaging GRP78 in Cancer

GRP78, a member of the HSP70 superfamily, is an endoplasmic reticulum chaperone protein overexpressed in various cancers, making it a promising target for cancer imaging and therapy. Positron emission tomography (PET) imaging offers unique advantages in real time, noninvasive tumor imaging, rendering it a suitable tool for targeting GRP78 in tumor imaging to guide targeted therapy. Several studies have reported successful tumor imaging using PET probes targeting GRP78. However, existing PET probes face challenges such as low tumor uptake, inadequate in vivo distribution, and high abdominal background signal. Therefore, this study introduces a novel peptide PET probe, [18F]AlF-NOTA-c-DVAP, for targeted tumor imaging of GRP78. [18F]AlF-NOTA-c-DVAP was radiolabeled with fluoride-18 using the aluminum-[18F]fluoride ([18F]AlF) method. The study assessed the partition coefficients, stability in vitro, and metabolic stability of [18F]AlF-NOTA-c-DVAP. Micro-PET imaging, pharmacokinetic analysis, and biodistribution studies were carried out in tumor-bearing mice to evaluate the probe's performance. Docking studies and pharmacokinetic analyses of [18F]AlF-NOTA-c-DVAP were also performed. Immunohistochemical and immunofluorescence analyses were conducted to confirm GRP78 expression in tumor tissues. The probe's binding affinity to GRP78 was analyzed by molecular docking simulation. [18F]AlF-NOTA-c-DVAP was radiolabeled in just 25 min with a high yield of 51 ± 16%, a radiochemical purity of 99%, and molar activity within the range of 20-50 GBq/μmol. [18F]AlF-NOTA-c-DVAP demonstrated high stability in vitro and in vivo, with a logD value of -3.41 ± 0.03. Dynamic PET imaging of [18F]AlF-NOTA-c-DVAP in tumors showed rapid uptake and sustained retention, with minimal background uptake. Biodistribution studies revealed rapid blood clearance and excretion through the kidneys following a single-compartment reversible metabolic model. In PET imaging, the T/M ratios for A549 tumors (high GRP78 expression), MDA-MB-231 tumors (medium expression), and HepG2 tumors (low expression) at 60 min postintravenous injection were 10.48 ± 1.39, 6.25 ± 0.47, and 3.15 ± 1.15% ID/g, respectively, indicating a positive correlation with GRP78 expression. This study demonstrates the feasibility of using [18F]AlF-NOTA-c-DVAP as a PET tracer for imaging GRP78 in tumors. The probe shows promising results in terms of stability, specificity, and tumor targeting. Further research may explore the clinical utility and potential therapeutic applications of this PET tracer for cancer diagnosis.

A novel peptide-drug conjugate for glioma-targeted drug delivery

The existence of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) greatly limits the application of chemotherapy in glioma. To address this challenge, an optimal drug delivery system must efficiently cross the BBB/BBTB and specifically deliver therapeutic drugs into glioma cells while minimizing systemic toxicity. Here we demonstrated that glucose-regulated protein 78 (GRP78) and dopamine receptor D2 were highly expressed in patient-derived glioma tissues, and dopamine receptors were highly expressed on the BBB. Subsequently, we synthesized a novel "Y"-shaped peptide and compared the effects of different linkers on the receptor affinity and targeting ability of the peptide. A peptide-drug conjugate (pHA-AOHX-VAP-doxorubicin conjugate, pHA-AOHX-VAP-DOX) with a better affinity for glioma cells and higher solubility was derived for glioma treatment. pHA-AOHX-VAP-DOX could cross both BBB and BBTB via dopamine receptor and GRP78 receptor, and finally target glioma cells, significantly prolonging the survival time of nude mice bearing intracranial glioma. Furthermore, pHA-AOHX-VAP-DOX significantly reduced the toxicity of DOX and increased the maximum tolerated dose (MTD). Collectively, this work paves a new avenue for overcoming multiple barriers and effectively delivering chemotherapeutic agents to glioma cells while providing key evidence to identify potential receptors for glioma-targeted drug delivery.

All-stage targeted red blood cell membrane-coated docetaxel nanocrystals for glioma treatment

Challenges for glioma treatment with nanomedicines include physio-anatomical barriers (the blood-brain barrier and blood-brain tumor barrier), low drug loading capacity, and limited circulation time. Here, a red blood cell membrane-coated docetaxel drug nanocrystal (pV-RBCm-NC(DTX)), modified with pHA-VAP (pV) for all-stage targeting of glioma, was designed. The NC(DTX) core exhibited a high drug loading capacity but low in vivo stability, and the RBCm coating significantly enhanced the stability and prolonged in vivo circulation. Moreover, the Y-shaped targeting ligand pV was modified by a mild avidin-biotin interaction, which endowed RBCm-NC(DTX) with superior barrier-crossing ability and therapeutic efficacy. The integration of nanocrystal technology, cell membrane coating, and the avidin-biotin insertion method into this active targeting biomimetic formulation represents a promising drug delivery strategy for glioma.

A Universal and Programmable Platform based on Fluorescent Peptide-Conjugated Probes for Detection of Proteins in Organelles of Living Cells

Realizing protein analysis in organelles of living cells is of great significance for developing diagnostic and therapeutic methods of diseases. Fluorescent-labeled antibodies with well imaging performance and high affinity are classical biochemical tools for protein analysis, while due to the inability to effectively enter into cells, not to mention organelles and the uncontrollable reaction sites that might cause antibodies inactivation when chemically modification, they are hard to apply to living cells. Inspired by the structure of fluorescent-labeled antibodies, we designed as a universal detection platform that was based on the peptide-conjugated probes (PCPs) and consisted of three parts: a) a rotor type fluorescent molecular scaffold for conjugation and signal output; b) the cell penetration protein recognition unit; c) the subcellular organelle targeting unit. In living cells, PCPs could firstly localize at organelles and then proceed protein specific recognition, thus jointly leading to the restriction of twisted intramolecular charge transfer and activation of fluorescence signal. As a proof-of-concept, six different proteins in three typical intracellular organelles could be detected by our platform through simply replacing the recognition sequence of proteins and matching organelle targeting units. The position and intensity of fluorescence signals demonstrated specificity of PCPs and universality of the platform.

Metabolism investigation of the peptide-drug conjugate LN005 in rats using UHPLCHRMS

LN005, as a peptide-drug conjugate (PDC), is a conjugate of the homing peptide VAP and doxorubicin (DOX). The exceptional targeting ability of the homing peptide VAP is directed toward glucose-regulated protein (GRP78), a highly expressed protein primarily found in the endoplasmic reticulum of various solid tumors. However, there are limited reports regarding the metabolism of peptide-drug conjugates (PDCs), and the in vivo metabolism of LN005 has yet to be investigated. After intravenous injection of 18 mg/kg LN005 in SD rats, biological samples including plasma, urine, fecal, and bile samples, were collected and analyzed by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). A total of 11 possible metabolites of LN005 were identified. Unchanged LN005 was found to be the main component in rat blood and urine, accounting for 46.46% and 63.79% of the total peak areas, respectively. M1057 was the most abundant metabolite in feces, accounting for 57.65% of the total peak area. Only one metabolite, M398, was identified in rat bile. The metabolism of LN005 is closely related to DOX, and the primary metabolic pathways involved oxidative deamination or hydrolysis, reductive glycosidic cleavage, hydrolytic glycosidic cleavage, and dehydrogenation.

Glucose-Regulated Protein 78 Targeting ICG and DOX Loaded Hollow Fe3O4 Nanoparticles for Hepatocellular Carcinoma Diagnosis and Therapy

Purpose

Liver cancer is considered as the third leading cause of cancer-related deaths, with hepatocellular carcinoma (HCC) accounting for approximately 90% of liver cancers. Improving the treatment of HCC is a serious challenge today. The primary objective of this study was to construct SP94-Fe3O4@ICG&DOX nanoparticles and investigate their potential diagnosis and treatment effect benefits on HCC.

Methods

Firstly, we synthesized and characterized SP94-Fe3O4@ICG&DOX nanoparticles and confirmed their in vitro release behavior, photothermal and photodynamic performance. Moreover, the in vivo imaging capability was also observed. Finally, the inhibitory effects on Hepa1-6 in vitro and in vivo were observed as well as biosafety.

Results

SP94-Fe3O4@ICG&DOX nanoparticles have a size of ~22.1 nm, with an encapsulation efficiency of 45.2% for ICG and 42.7% for DOX, showing excellent in vivo MPI and fluorescence imaging capabilities for precise tumor localization, and synergistic photo-chemotherapy (pH- and thermal-sensitive drug release) against tumors under irradiation. With the assistance of a fluorescence molecular imaging system or MPI scanner, the location and contours of the tumor were clearly visible. Under a constant laser irradiation (808 nm, 0.6 W/cm2) and a set concentration (50 µg/mL), the temperature of the solution could rapidly increase to ~45 °C, which could effectively kill the tumor cells. It could be effectively uptaken by HCC cells and significantly inhibit their proliferation under the laser irradiation (100% inhibition rate for HCC tumors). And most importantly, our nanoparticles exhibited favorable biocompatibility with normal tissues and cells.

Conclusion

This versatile agent can serve as an intelligent and promising nanoplatform that integrates multiple accurate diagnoses, precise positioning of cancer tissue, and effective coordination with synergistic tumor photodynamic therapy.

Metabolite characterisation of the peptide-drug conjugate LN005 in liver S9s by UHPLC-Orbitrap-HRMS

LN005 is a peptide-drug conjugate (PDC) targeting glucose-regulated protein 78 (GRP78) to treat several types of cancer, such as breast, colon, and prostate cancer.As a new drug modality, understanding its metabolism and elimination pathways will help us to have a whole picture of it. Currently, there are no metabolic studies on LN005; therefore, this study aimed to investigate the metabolism of LN005, clarify its metabolic profile in the liver S9s of different species, and identify the major metabolic pathways and differences between species.The incubation samples were measured by ultra-high performance liquid chromatography combined with orbitrap tandem mass spectrometry (UHPLC-Orbitrap-HRMS).The results showed that LN005 was metabolised by liver S9s, and four metabolites were identified. The main metabolic pathway of LN005 in liver S9s was oxidative deamination to ketone or hydrolysis. Similar metabolic profiles were observed in mouse, rat, dog, monkey, and human liver S9s, indicating no differences between these four animal species and humans.This study provides information for the structural modification and optimisation of LN005 and affords a reference for subsequent animal experiments and human metabolism of other PDCs.

Molecular View on the iRGD Peptide Binding Mechanism: Implications for Integrin Activity and Selectivity Profiles

Receptor-selective peptides are widely used as smart carriers for specific tumor-targeted delivery. A remarkable example is the cyclic nonapeptide iRGD (CRGDKPGDC, 1) that couples intrinsic cytotoxic effects with striking tumor-homing properties. These peculiar features are based on a rather complex multistep mechanism of action, where the primary event is the recognition of RGD integrins. Despite the high number of preclinical studies and the recent success of a phase I trial for the treatment of pancreatic ductal adenocarcinoma (PDAC), there is little information available about the iRGD three-dimensional (3D) structure and integrin binding properties. Here, we re-evaluate the peptide's affinity for cancer-related integrins including not only the previously known targets αvβ3 and αvβ5 but also the αvβ6 isoform, which is known to drive cell growth, migration, and invasion in many malignancies including PDAC. Furthermore, we use parallel tempering in the well-tempered ensemble (PT-WTE) metadynamics simulations to characterize the in-solution conformation of iRGD and extensive molecular dynamics calculations to fully investigate its binding mechanism to integrin partners. Finally, we provide clues for fine-tuning the peptide's potency and selectivity profile, which, in turn, may further improve its tumor-homing properties.

Topoisomeric Membrane-Active Peptides: A Review of the Last Two Decades

In recent decades, bioactive peptides have been gaining recognition in various biomedical areas, such as intracellular drug delivery (cell-penetrating peptides, CPPs) or anti-infective action (antimicrobial peptides, AMPs), closely associated to their distinct mode of interaction with biological membranes. Exploiting the interaction of membrane-active peptides with diverse targets (healthy, tumoral, bacterial or parasitic cell membranes) is opening encouraging prospects for peptides in therapeutics. However, ordinary peptides formed by L-amino acids are easily decomposed by proteases in biological fluids. One way to sidestep this limitation is to use topoisomers, namely versions of the peptide made up of D-amino acids in either canonic (enantio) or inverted (retroenantio) sequence. Rearranging peptide sequences in this fashion provides a certain degree of native structure mimicry that, in appropriate contexts, may deliver desirable biological activity while avoiding protease degradation. In this review, we will focus on recent accounts of membrane-active topoisomeric peptides with therapeutic applications as CPP drug delivery vectors, or as antimicrobial and anticancer candidates. We will also discuss the most common modes of interaction of these peptides with their membrane targets.

Chimeric antigen receptor T cells targeting cell surface GRP78 efficiently kill glioblastoma and cancer stem cells

BACKGROUND

Glioblastoma (GBM) is recognized as among the most aggressive forms of brain tumor. Patients typically present with a five-year survival rate of less than 6% with traditional surgery and chemoradiotherapy, which calls for novel immunotherapies like chimeric antigen receptor T (CAR-T) cells therapy. In response to endoplasmic reticulum (ER) stress in multiple tumor cells including GBM, the glucose-regulated protein 78 (GRP78) expression increases and the protein is partially translocated to the cell surface, while it is restricted to the cytoplasm and the nucleus in normal cells.

METHODS

In this study, to target the cell surface GRP78 (csGRP78), CAR-T cells based on its binding peptide were generated. In vitro two GBM cell lines and glioma stem cells (GSCs) were used to confirm the localization of csGRP78 and the cytotoxicity of the CAR-T cells. In vivo a GBM xenograft model was used to assess the killing activity and the safety of the CAR-T cells.

RESULTS

We confirmed the localization of csGRP78 at the cell surface of two GBM cell lines (U-251MG and U-87MG) and in GSCs. Co-culture experiments revealed that the CAR-T cells could specifically kill the GBM tumor cells and GSCs with specific IFN-γ release. Furthermore, in the tumor xenograft model, the CAR-T cells could decrease the number of GSCs and significantly suppress tumor cell growth. Importantly, we found no obvious off-target effects or T cell infiltration in major organs following systemic administration of these cells.

CONCLUSIONS

The csGRP78 targeted CAR-T cells efficiently kill GBM tumor cells and GSCs both in vitro and in vivo, and ultimately suppress the xenograft tumors growth without obvious tissue injuries. Therefore, our study demonstrates that csGRP78 represents a valuable target and the csGRP78-targeted CAR-T cells strategy is an effective immunotherapy against GBM.

How Nanotherapeutic Platforms Play a Key Role in Glioma? A Comprehensive Review of Literature

Glioblastoma (GBM), a highly aggressive form of brain cancer, is considered one of the deadliest cancers, and even with the most advanced medical treatments, most affected patients have a poor prognosis. However, recent advances in nanotechnology offer promising avenues for the development of versatile therapeutic and diagnostic nanoplatforms that can deliver drugs to brain tumor sites through the blood-brain barrier (BBB). Despite these breakthroughs, the use of nanoplatforms in GBM therapy has been a subject of great controversy due to concerns over the biosafety of these nanoplatforms. In recent years, biomimetic nanoplatforms have gained unprecedented attention in the biomedical field. With advantages such as extended circulation times, and improved immune evasion and active targeting compared to conventional nanosystems, bionanoparticles have shown great potential for use in biomedical applications. In this prospective article, we endeavor to comprehensively review the application of bionanomaterials in the treatment of glioma, focusing on the rational design of multifunctional nanoplatforms to facilitate BBB infiltration, promote efficient accumulation in the tumor, enable precise tumor imaging, and achieve remarkable tumor suppression. Furthermore, we discuss the challenges and future trends in this field. Through careful design and optimization of nanoplatforms, researchers are paving the way toward safer and more effective therapies for GBM patients. The development of biomimetic nanoplatform applications for glioma therapy is a promising avenue for precision medicine, which could ultimately improve patient outcomes and quality of life.

Super-enhancer-driven lncRNA LIMD1-AS1 activated by CDK7 promotes glioma progression

Long non-coding RNAs (lncRNAs) are tissue-specific expression patterns and dysregulated in cancer. How they are regulated still needs to be determined. We aimed to investigate the functions of glioma-specific lncRNA LIMD1-AS1 activated by super-enhancer (SE) and identify the potential mechanisms. In this paper, we identified a SE-driven lncRNA, LIMD1-AS1, which is expressed at significantly higher levels in glioma than in normal brain tissue. High LIMD1-AS1 levels were significantly associated with a shorter survival time of glioma patients. LIMD1-AS1 overexpression significantly enhanced glioma cells proliferation, colony formation, migration, and invasion, whereas LIMD1-AS1 knockdown inhibited their proliferation, colony formation, migration, and invasion, and the xenograft tumor growth of glioma cells in vivo. Mechanically, inhibition of CDK7 significantly attenuates MED1 recruitment to the super-enhancer of LIMD1-AS1 and then decreases the expression of LIMD1-AS1. Most importantly, LIMD1-AS1 could directly bind to HSPA5, leading to the activation of interferon signaling. Our findings support the idea that CDK7 mediated-epigenetically activation of LIMD1-AS1 plays a crucial role in glioma progression and provides a promising therapeutic approach for patients with glioma.

Cell surface GRP78: a potential mechanism of therapeutic resistant tumors

GRP78 is a protein that acts as a chaperone within the endoplasmic reticulum (ER) and has multiple functions. It is induced by stress and abets cells from survival. Despite, multiple Stress conditions like ER, chronic psychological and nutritional stress, hypoxia, chemotherapy, radiation therapy, and drug resistance induce cell surface GRP78 (CS-GRP78) expression in cancer cells. Further, CS-GRP78 is associated with increased malignancy and resistance to anti-cancer therapies and is considered a high-value druggable target. Recent preclinical research suggests that targeting CS-GRP78 with anti-GRP78 monoclonal antibodies (Mab) in combination with other agents may be effective in reversing the failure of chemotherapy, radiotherapy, or targeted therapies and increasing the efficacy of solid tumors treatment. This article will review recent evidence on the role of CS-GRP78 in developing resistance to anti-cancer treatments and the potential benefits of combining anti-GRP78 Mab with other cancer therapies for specific patient populations. Furthermore, our limited understanding of how CS-GRP78 regulated in human studies is a major drawback for designing effective CS-GRP78-targeted therapies. Hence, more research is still warranted to translate these potential therapies into clinical applications.

Advances in nanotechnology for the treatment of GBM

Glioblastoma (GBM), a highly malignant glioma of the central nervous system, is the most dread and common brain tumor with a high rate of therapeutic resistance and recurrence. Currently, the clinical treatment methods are surgery, radiotherapy, and chemotherapy. However, owning to the highly invasive nature of GBM, it is difficult to completely resect them due to the unclear boundary between the edges of GBM and normal brain tissue. Traditional radiotherapy and the combination of alkylating agents and radiotherapy have significant side effects, therapeutic drugs are difficult to penetrate the blood brain barrier. Patients receiving treatment have a high postoperative recurrence rate and a median survival of less than 2 years, Less than 5% of patients live longer than 5 years. Therefore, it is urgent to achieve precise treatment through the blood brain barrier and reduce toxic and side effects. Nanotechnology exhibit great potential in this area. This article summarizes the current treatment methods and shortcomings of GBM, and summarizes the research progress in the diagnosis and treatment of GBM using nanotechnology.

Biological evaluation of a novel stable peptide PET molecular probe [18F]AlF-NOTA-DVAP targeting to tumor cell surface GRP78

BACKGROUNDS

Glucose-Regulated Protein 78 (GRP78) is an attractive anticancer target for its selective anchoring on the surface of tumor cells and cancer endothelial cells rather than normal cells. Cell-surface GRP78 overexpression of tumor indicates that GRP78 is a crucial target for relative tumor imaging and clinical treatment. Herein, we report the design and preclinical evaluation of a new D peptide ligand [¹⁸F]AlF-NOTA-^DVAP recognizing GRP78 expressed on the cell surface of breast cancer.

METHODS

Radiochemical synthesis of [¹⁸F]AlF-NOTA-^DVAP was achieved via a one-pot labeling process by heating NOTA-^DVAP in the presence of in situ prepared [¹⁸F]AlF for 15 min at 110 °C and purified through HPLC.

RESULTS

The radiotracer showed high in vitro stability in rat serum at 37 °C over 3 h. Both biodistribution studies and in vivo micro-PET/CT imaging studies in BALB/c mice bearing 4 T1 tumor showed [¹⁸F]AlF-NOTA-^DVAP had a rapid and high uptake in tumor, as well as a long residence time. The high hydrophilicity of the radiotracer enables its fast clearance from most normal tissues and thus improves the tumor-to-normal tissue ratios (4.40 at 60 min) which is better than [¹⁸F]FDG (1.31 at 60 min). Pharmacokinetic studies showed the average in vivo mean residence time of the radiotracer was just 0.6432 h and indicated that this hydrophilic radiotracer was quickly eliminated from the body to reduce the distribution of non-target tissues.

CONCLUSIONS

These results suggest that [¹⁸F]AlF-NOTA-^DVAP is a very promising PET probe for tumor-specific imaging of cell-surface GRP78-positive tumor.

Nanomedicines Targeting Glioma Stem Cells

Glioblastoma (GBM), classified as a grade IV glioma, is a rapidly growing, aggressive, and most commonly occurring tumor of the central nervous system. Despite the therapeutic advances, it carries an ominous prognosis, with a median survival of 14.6 months after diagnosis. Accumulating evidence suggests that cancer stem cells in GBM, termed glioma stem cells (GSCs), play a crucial role in tumor propagation, treatment resistance, and tumor recurrence. GSCs, possessing the capacity for self-renewal and multilineage differentiation, are responsible for tumor growth and heterogeneity, leading to primary obstacles to current cancer therapy. In this respect, increasing efforts have been devoted to the development of anti-GSC strategies based on targeting GSC surface markers, blockage of essential signaling pathways of GSCs, and manipulating the tumor microenvironment (GSC niches). In this review, we will discuss the research knowledge regarding GSC-based therapy and the underlying mechanisms for the treatment of GBM. Given the rapid progression in nanotechnology, innovative nanomedicines developed for GSC targeting will also be highlighted from the perspective of rationale, advantages, and limitations. The goal of this review is to provide broader understanding and key considerations toward the future direction of GSC-based nanotheranostics to fight against GBM.

All-stage targeted therapy for the brain metastasis from triple-negative breast cancer

Brain metastasis is a common and serious complication of breast cancer, which is commonly associated with poor survival and prognosis. In particular, the treatment of brain metastasis from triple-negative breast cancer (BM-TNBC) has to face the distinct therapeutic challenges from tumor heterogeneity, circulating tumor cells (CTCs), blood-brain barrier (BBB) and blood-tumor barrier (BTB), which is in unmet clinical needs. Herein, combining with the advantages of synthetic and natural targeting moieties, we develop a "Y-shaped" peptide pVAP-decorated platelet-hybrid liposome drug delivery system to address the all-stage targeted drug delivery for the whole progression of BM-TNBC. Inherited from the activated platelet, the hybrid liposomes still retain the native affinity toward CTCs. Further, the peptide-mediated targeting to breast cancer cells and transport across BBB/BTB are demonstrated in vitro and in vivo. The resultant delivery platform significantly improves the drug accumulation both in orthotopic breast tumors and brain metastatic lesions, and eventually exhibits an outperformance in the inhibition of BM-TNBC compared with the free drug. Overall, this work provides a promising prospect for the comprehensive treatment of BM-TNBC, which could be generalized to other cell types or used in imaging platforms in the future.

Peptides as Pharmacological Carriers to the Brain: Promises, Shortcomings and Challenges

Central nervous system (CNS) diseases are among the most difficult to treat, mainly because the vast majority of the drugs fail to cross the blood-brain barrier (BBB) or to reach the brain at concentrations adequate to exert a pharmacological activity. The obstacle posed by the BBB has led to the in-depth study of strategies allowing the brain delivery of CNS-active drugs. Among the most promising strategies is the use of peptides addressed to the BBB. Peptides are versatile molecules that can be used to decorate nanoparticles or can be conjugated to drugs, with either a stable link or as pro-drugs. They have been used to deliver to the brain both small molecules and proteins, with applications in diverse therapeutic areas such as brain cancers, neurodegenerative diseases and imaging. Peptides can be generally classified as receptor-targeted, recognizing membrane proteins expressed by the BBB microvessels (e.g., Angiopep2, CDX, and iRGD), "cell-penetrating peptides" (CPPs; e.g. TAT_47-57, SynB1/3, and Penetratin), undergoing transcytosis through unspecific mechanisms, or those exploiting a mixed approach. The advantages of peptides have been extensively pointed out, but so far few studies have focused on the potential negative aspects. Indeed, despite having a generally good safety profile, some peptide conjugates may display toxicological characteristics distinct from those of the peptide itself, causing for instance antigenicity, cardiovascular alterations or hemolysis. Other shortcomings are the often brief lifetime in vivo, caused by the presence of peptidases, the vulnerability to endosomal/lysosomal degradation, and the frequently still insufficient attainable increase of brain drug levels, which remain below the therapeutically useful concentrations. The aim of this review is to analyze not only the successful and promising aspects of the use of peptides in brain targeting but also the problems posed by this strategy for drug delivery.

Hydra-Elastin-like Polypeptides Increase Rapamycin Potency When Targeting Cell Surface GRP78

Rapalogues are powerful therapeutic modalities for breast cancer; however, they suffer from low solubility and dose-limiting side effects. To overcome these challenges, we developed a long-circulating multiheaded drug carrier called 5FA, which contains rapamycin-binding domains linked with elastin-like polypeptides (ELPs). To target these "Hydra-ELPs" toward breast cancer, we here linked 5FA with four distinct peptides which are reported to engage the cell surface form of the 78 kDa glucose-regulated protein (csGRP78). To determine if these peptides affected the carrier solubility, this library was characterized by light scattering and mass spectrometry. To guide in vitro selection of the most potent functional carrier for rapamycin, its uptake and inhibition of mTORC1 were monitored in a ductal breast cancer model (BT474). Using flow cytometry to track cellular association, it was found that only the targeted carriers enhanced cellular uptake and were susceptible to proteolysis by SubA, which specifically targets csGRP78. The functional inhibition of mTOR was monitored by Western blot for pS6K, whereby the best carrier L-5FA reduced mTOR activity by 3-fold compared to 5FA or free rapamycin. L-5FA was further visualized using super-resolution confocal laser scanning microscopy, which revealed that targeting increased exposure to the carrier by ∼8-fold. This study demonstrates how peptide ligands for GRP78, such as the L peptide (RLLDTNRPLLPY), may be incorporated into protein-based drug carriers to enhance targeting.

All-stage targeted therapy for glioblastoma based on lipid membrane coated cabazitaxel nanocrystals

Glioblastoma (GBM) is the most aggressive brain tumor with poor prognosis and frequent recurrence. The blood-brain barrier (BBB), blood-brain tumor barrier (BBTB) hinder the entry of therapeutics into the glioma region. Vasculogenic mimicry (VM) formed by invasive glioma cells is also related to recurrence of GBM. VAP is a D-peptide ligand of GRP78 protein overexpressed on BBTB, VM, and glioma cells but not on normal tissues. Besides, p-hydroxybenzoic acid (pHA) can effectively traverse the BBB. Herein we developed an all-stage glioma-targeted cabazitaxel (CBZ) nanocrystal loaded liposome modified with a "Y" shaped targeting ligand composed of pHA and VAP (pV-Lip/cNC). The pure drug nanocrystal core provided high drug loading, while lipid membrane promoted the stability and circulation time. pV-Lip/cNC exhibited excellent glioma homing, barriers crossing, and tumor spheroid penetrating capability in vitro. Treatment of pV-Lip/cNC displayed enhanced CBZ accumulation in glioma and anti-glioma effect with a median survival time (53 days) significantly longer than that of cNC loaded liposomes modified with either single ligand (42 days for VAP and 45 days for pHA) in the murine orthotopic GBM model. These results indicated pV-Lip/cNC could traverse the BBB and BBTB, destruct VM, and finally kill glioma cells to realize all-stage glioma therapy.

Enhanced BBB and BBTB penetration and improved anti-glioma behavior of Bortezomib through dual-targeting nanostructured lipid carriers

The effective treatment of glioma through conventional chemotherapy is proved to be a great challenge in clinics. The main reason is due to the existence of two physiological and pathological barriers respectively including the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) that prevent most of the chemotherapeutics from efficient delivery to the brain tumors. To address this challenge, an ideal drug delivery system would efficiently traverse the BBB and BBTB and deliver the therapeutics into the glioma cells with high selectivity. Herein, a targeted delivery system was developed based on nanostructured lipid carriers (NLCs) modified with two proteolytically stable D-peptides, D8 and RI-VAP (Dual NLCs). D8 possesses high affinity towards nicotine acetylcholine receptors (nAChRs), overexpressed on brain capillary endothelial cells (BCECs), and can penetrate through BBB with high efficiency. RI-VAP is a specific ligand of cell surface GRP78 (csGRP78), a specific angiogenesis and cancer cell-surface marker, capable of circumventing the BBTB with superior glioma-homing property. Dual NLCs could internalize into BCECs, tumor neovascular endothelial cells, and glioma cells with high specificity and could penetrate through in vitro BBB and BBTB models with excellent efficiency compared to non-targeted or mono-targeted NLCs. In vivo whole-animal imaging and ex vivo imaging further confirmed the superior targeting capability of Dual NLCs towards intracranial glioma. When loaded with Bortezomib (BTZ), Dual NLCs attained the highest therapeutic efficiency by means of in vitro cytotoxicity and apoptosis and prolonged survival rate and anti-glioma behavior in intracranial glioma bearing mice. Collectively, the designed targeting platform in this study could overcome multiple barriers and effectively deliver BTZ to glioma cells, which represent its potential for advanced brain cancer treatment with promising therapeutic outcomes.

Synthetic polymer material modified by d-peptide and its targeted application in the treatment of non-small cell lung cancer

Liposomes functionalized with targeted material offer a breakthrough compared with passive drug delivery. Here, we designed a polymer material, VAP-PEG₃₃₅₀-DSPE (VAP-PEG-DSPE), modified with a d-peptide VAP ligand that combines tumor-homing VAP with GRP78 receptor, a cancer marker on the membranes of many cancer cells. This paper establishes a docetaxel-loaded lipid nanodisk modified with multifunctional material to evaluate its anti-NSCLC efficacy in vivo. Additionally, the present study verified that VAP-conjugated nanodisks adapt to the developed tumor vasculature of the lung cancer microenvironment, making it a promising nanocarrier for NSCLC-targeting therapy. Moreover, in vitro and in vivo experiments demonstrated the targeting ability of VAP-DISK/DTX to tumor cells. Lung slices of mice also demonstrated the safety of VAP-DISK/DTX. The encapsulation efficiency of docetaxel-disks (VAP-DISK/DTX) was as high as 92.46±4.48%. Encapsulating anti-cancer drugs in lipid nanoparticles is thus an effective mechanism to change the pharmacokinetic and pharmacodynamic characteristics of drugs.

Nanoscale Drug Delivery Systems in Glioblastoma

Glioblastoma is the most aggressive cerebral tumor in adults. However, the current pharmaceuticals in GBM treatment are mainly restricted to few chemotherapeutic drugs and have limited efficacy. Therefore, various nanoscale biomaterials that possess distinct structure and unique property were constructed as vehicles to precisely deliver molecules with potential therapeutic effect. In this review, nanoparticle drug delivery systems including CNTs, GBNs, C-dots, MOFs, Liposomes, MSNs, GNPs, PMs, Dendrimers and Nanogel were exemplified. The advantages and disadvantages of these nanoparticles in GBM treatment were illustrated.

Recent Applications of Retro-Inverso Peptides

Natural and de novo designed peptides are gaining an ever-growing interest as drugs against several diseases. Their use is however limited by the intrinsic low bioavailability and poor stability. To overcome these issues retro-inverso analogues have been investigated for decades as more stable surrogates of peptides composed of natural amino acids. Retro-inverso peptides possess reversed sequences and chirality compared to the parent molecules maintaining at the same time an identical array of side chains and in some cases similar structure. The inverted chirality renders them less prone to degradation by endogenous proteases conferring enhanced half-lives and an increased potential as new drugs. However, given their general incapability to adopt the 3D structure of the parent peptides their application should be careful evaluated and investigated case by case. Here, we review the application of retro-inverso peptides in anticancer therapies, in immunology, in neurodegenerative diseases, and as antimicrobials, analyzing pros and cons of this interesting subclass of molecules.

Noninvasive Classification of Human Triple Negative Breast Cancer by PET Imaging with GRP78-Targeted Molecular Probe [68Ga]DOTA-VAP

PURPOSE

There is currently no effective noninvasive method for accurate molecular typing of triple negative breast cancer (TNBC) except needle biopsy. Glucoregulated Protein 78 (GRP78) is overexpressed in TNBC cells and tumors which closely related to the invasion, metastasis, and drug resistance of cancer. Meanwhile, it has been verified that VAP peptide bind specifically to GRP78 in vitro and in vivo. In this study, we constructed a GRP78-targeted molecular probe Ga-68-radiolabeled DOTA-VAP conjugate ([⁶⁸Ga]DOTA-VAP) based on VAP peptide, and evaluated its potential to distinguish TNBC from non-TNBC tumors.

PROCEDURES

DOTA-VAP was synthesized and then radiolabeled with Ga-68 to obtain [⁶⁸Ga]DOTA-VAP. The expression of GRP78 in TNBC MDA-MB-231 and non-TNBC MCF-7 cells was validated by Western Blot, and cell binding or uptake experiments with both [⁶⁸Ga]DOTA-VAP and 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) were also performed. Biodistribution analysis and positron emission tomography (PET) imaging of [⁶⁸Ga]DOTA-VAP were carried out in subcutaneous MDA-MB-231 and MCF-7 human breast cancer tumor models with [¹⁸F]FDG PET imaging as comparison.

RESULTS

[⁶⁸Ga]DOTA-VAP was prepared with high radiochemical purity which showed excellent stability in vitro. The MDA-MB-231 tumors were clearly visualized by [⁶⁸Ga]DOTA-VAP PET imaging with a low background, except for the relatively high liver uptake. Cells and tumors of MDA-MB-231 could be distinguished from MCF-7 by [⁶⁸Ga]DOTA-VAP instead of [¹⁸F]FDG. Biodistribution results were consistent with the imaging results. The blocking study with excess cold peptide showed significantly reduced tumor uptake, which indicated the specificity of [⁶⁸Ga]DOTA-VAP targeting MDA-MB-231 tumors in vivo.

CONCLUSIONS

GRP78-targeted PET imaging with [⁶⁸Ga]DOTA-VAP provided an effective approach for the noninvasive accurate classification of TNBC from other breast cancer subtypes comparing with [¹⁸F]FDG. GRP78 may be a potential target for the diagnosis and treatment of TNBC. For clinical transformation, efforts should be made to overcome deficiencies of [⁶⁸Ga]DOTA-VAP such as relative high uptake in normal tissues.

An update on actively targeted liposomes in advanced drug delivery to glioma

High-grade glioma is one of the most aggressive types of cancer with a low survival rate ranging from 12 to 15 months after the first diagnosis. Though being the most common strategy for glioma therapy, conventional chemotherapy suffers providing the therapeutic dosage of common therapeutics mostly because of limited permeability of blood-brain barrier (BBB), and blood-brain tumor barrier (BBTB) to anticancer agents. Among various nanoformulations, liposomes are considered as the most popular carriers aimed for glioma therapy. However, non-targeted liposomes which passively accumulate in most of the cancer tissues mainly through the enhanced permeation and retention effect (EPR), may not be applicable for glioma therapy due to BBB tight junctions. In the recent decade, the surface modification of liposomes with different active targeting ligands has shown promising results by getting different chemotherapeutics across the BBB and BBTB and leading them into the glioma cells. The present review discusses the major barriers for drug delivery systems to glioma, elaborates the existing mechanisms for liposomes to traverse across the BBB, and explores the main strategies for incorporation of targeting ligands onto the liposomes. It subsequently investigates the most recent and relevant studies of actively targeted liposomes modified with antibodies, aptamers, monosaccharides, polysaccharides, proteins, and peptides applied for effective glioma therapy, and highlights the common challenges facing this area. Finally, the actively targeted liposomes undergoing preclinical and clinical studies for delivery of different anticancer agents to glioma cells will be reviewed.

LINC00665/miR-379-5p/GRP78 regulates cisplatin sensitivity in gastric cancer by modulating endoplasmic reticulum stress

Acquired resistance to cisplatin (DDP)-based chemotherapy greatly hinders the treatment of gastric cancer (GC). LINC00665 serves as an oncogene in GC. Hence, the current study was designed to investigate the regulatory effects of LINC00665 on DDP-resistance of GC. LINC00665 and miR-379-5p expression levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and Glucose regulated protein 78 (GRP78) protein level was measured by western blot assay. Interactions between LINC00665 and miR-379-5p or between miR-379-5p and GRP78 were verified by dual luciferase reporter assay. Cell counting kit 8 (CCK-8) assay and flow cytometry assay respectively determine the proliferative ability and apoptosis of GC cells. Western blot analysis was also performed to detect the protein levels of C/EBP-homologous protein (CHOP), X box binding protein (XBP1) and apoptosis-related proteins. In addition, GRP78 expression was evaluated by immunofluorescence. It was observed that the expression levels of LINC00665 and GRP78 were upregulated, and the expression level of miR-379-5p was downregulated in DDP-sensitive and DDP-resistant GC cell lines. What's more, GRP78 expression and the cell growth inhibition rates of DDP-sensitive and DDP-resistant GC cells had a negative correlation. Additionally, miR-379-5p was a target miRNA of LINC00665, and GRP78 was a target mRNA of miR-379-5p. Functional studies revealed that knockdown of LINC00665 inhibited DDP-resistant GC cell proliferation, induced apoptosis as well as suppressed Endoplasmic reticulum (ER) stress. Mechanistically, knockdown of LINC00665 downregulated GRP78 expression by strengthening miR-379-5p. LINC00665 silencing could overcome DPP-resistance of GC cells by downregulating GRP78 via sponging miR-379-5p, indicating that LINC00665 might be a potential therapeutic target for DDP- resistant GC patients.

GRP78 targeting: Hitting two birds with a stone

BACKGROUND

Glucose regulating protein 78 (GRP78) is one member of the Heat Shock Protein family of chaperone proteins (HSPA5) found in eukaryotes. It acts as the master of the Unfolded Protein Response (UPR) process in the lumen of the Endoplasmic Reticulum (ER).

SCOPE

Under the stress of unfolded proteins, GRP78 binds to the unfolded proteins to prevent misfolding, while under the load of the unfolded protein, it drives the cell to autophagy or apoptosis. Several attempts reported the overexpression of GRP78 on the cell membrane of cancer cells and cells infected with viruses or fungi.

MAJOR CONCLUSIONS

Cell-surface GRP78 is used as a cancer cell target in previous studies. Additionally, GRP78 is used as a drug target to stop the progression of cancer cells by different compounds, including peptides, antibodies, and some natural compounds. Additionally, it can be used as a protein target to reduce the infectivity of different viruses, including the pandemic SARS-CoV-2. Besides, GRP78 targeting is used in diagnosis and imaging modalities using radionuclides.

GENERAL SIGNIFICANCE

This review summarizes the various attempts that used GRP78 both in therapy (fighting cancer, viral and fungal infections) and diagnosis (imaging).

Advances and Prospects of Vasculogenic Mimicry in Glioma: A Potential New Therapeutic Target?

Vasculogenic mimicry (VM) is the formation of a “vessel-like” structure without endothelial cells. VM exists in vascular-dependent solid tumors and is a special blood supply source involved in the highly invasive tumor progression. VM is observed in a variety of human malignant tumors and is closely related to tumor proliferation, invasion, and recurrence. Here, we review the mechanism, related signaling pathways, and molecular regulation of VM in glioma and discuss current research problems and the potential future applications of VM in glioma treatment. This review may provide a new viewpoint for glioma therapy.

ɑvβ3-targeted liposomal drug delivery system with attenuated immunogenicity enabled by linear pentapeptide for glioma therapy

Owing to the binding capacity to ɑ_vβ₃ integrin overexpressed on glioma, vasculogenic mimicry and neovasculature, the peptide c(RGDyK) has been exploited pervasively to functionalize nanocarriers for targeted delivery of bioactives. The former study in our group substantiated the immunotoxicity of c(RGDyK)-modified liposome, and this unfavorable immunogenicity is known to compromise blood circulation, targeting efficacy and therapeutic outcome. Therefore, we need to find a superior alternative ligand in order to evade the exquisite immuno-sensitization. We developed mn by structure-guided peptide design and retro-inverso isomerization technique, which was experimentally substantiated to have exceptional binding affinity to ɑ_vβ₃ integrin. Besides mn does not have affinity toward normal liver cells and kidney cells, which c(RGDyK) possesses in a certain degree. Warranting that mn and c(RGDyK) anchored ɑ_vβ₃, we formulated peptide-tethered liposomes and investigated in vivo bio-fate. Compared with c(RGDyK)-modified liposome, mn-modified liposome presented longer blood circulation and reduced ingestion by Kupffer cells with decreased retention in liver accordingly, benefitting from attenuated anti-liposome IgG and IgM response elicited by multiple sequential doses. Those merits strengthened the anti-glioma efficacy of ɑ_vβ₃-targeted doxorubicin-loaded liposomes, proving the importance of immunocompatibility in process of targeted drug delivery.

Nano-Therapies for Glioblastoma Treatment

Traditional anti-cancer treatments are inefficient against glioblastoma, which remains one of the deadliest and most aggressive cancers. Nano-drugs could help to improve this situation by enabling: (i) an increase of anti-glioblastoma multiforme (GBM) activity of chemo/gene therapeutic drugs, notably by an improved diffusion of these drugs through the blood brain barrier (BBB), (ii) the sensibilization of radio-resistant GBM tumor cells to radiotherapy, (iii) the removal by surgery of infiltrating GBM tumor cells, (iv) the restoration of an apoptotic mechanism of GBM cellular death, (v) the destruction of angiogenic blood vessels, (vi) the stimulation of anti-tumor immune cells, e.g., T cells, NK cells, and the neutralization of pro-tumoral immune cells, e.g., Treg cells, (vii) the local production of heat or radical oxygen species (ROS), and (viii) the controlled release/activation of anti-GBM drugs following the application of a stimulus. This review covers these different aspects.

An iRGD-conjugated prodrug micelle with blood-brain-barrier penetrability for anti-glioma therapy

Various obstacles impede the chemotherapy efficiency of glioma in clinic, such as blood brain barrier (BBB) and blood brain tumor barrier (BBTB). Ligand-mediated polymeric micelles have shown great potential for improving the efficiency of glioma treatment. Herein, we developed a disulfide bond-conjugated prodrug polymer consisted of camptothecin (CPT) and polyethylene glycol (PEG) with further modification of iRGD peptide. The polymer of CPT-S-S-PEG-COOH could self-assemble into nanosized polymeric micelles with diameter around 100 nm, and loaded with photosensitizer IR780 for combination therapy. The micelles displayed good stability with controlled drug release under physiological environment. Importantly, the iRGD modified polymeric micelles demonstrated favorable ability to cross the BBB and target glioma cells via αv β integrin and neuropilin-1-mediated ligand transportation in vitro and in vivo. The whole synthesis process is simple and the drug loading content of CPT in the CPT-S-S-PEG-iRGD@IR780 micelles was higher than 10%. Moreover, CPT-S-S-PEG-iRGD@IR780 micelles combined chemotherapy with photodynamic therapy (PDT) displayed more excellent tumor-killing capability than the other groups. Thus, both in vitro and in vivo studies suggested that the targeting prodrug system could not only effectively cross various barriers to reach at glioma site, but also significantly enhance the antitumor effect with laser irradiation. Our findings consequently suggested that CPT-S-S-PEG-iRGD@IR780 micelles with laser irradiation are a promising drug delivery system for glioma therapy.

Expression of glucose-regulated protein 78 as prognostic biomarkers for triple-negative breast cancer

INTRODUCTION

Glucose-regulated protein78(GRP78) is a stress - induced endoplasmic reticulum chaperone protein. it is closely related to the occurrence, development, proliferation, differentiation and drug resistance of breast cancer. However, the association and clinicopathological features between GRP78 and triple negative breast cancer (TNBC) remain to be studied.

MATERIAL AND METHODS

Clinical and pathological characteristics and overall survival were analysed retrospectively in 179 surgically resected TNBC patients. GRP78 was detected by immunohistochemistry (IHC) using breast cancer tissue microarrays (TMAs), and the association between GRP78 levels and clinicopathological factors and prognosis was analyzed. Furthermore, GRP78 expression in human TNBC and NTNBC cell lines was detected by Western blot and qRT-PCR. After Si-GRP78 knocked-down GRP78 in MDA-MB-231 and BT549 cell lines, cell proliferation was detected using Cell Counting Kit-8 (CCK-8) and cell colony formation was detected by crystal violet staining, respectively.

RESULTS

GRP78 was expressed in triple negative breast cancer (TNBC). GRP78 expression was significantly associated with invasive, distant metastasis and proliferation of TNBC (P<0.05). In addition, patients with positive GRP78 expression had shorter overall survival (OS) and disease-free survival (DFS). And the high expression of GRP78 was significantly associated with disease-free survival (DFS) in patients with TNBC (P<0.001).

CONCLUSIONS

These findings improve our understanding of the expression pattern of GRP78 in TNBC and clarify the role of GRP78 as promising prognostic biomarkers for triple-negative breast cancer.

Non-immunogenic, low-toxicity and effective glioma targeting MTI-31 liposomes

Liposomes with peptide motifs have been successfully used in glioma-targeted delivery of various general chemotherapy agents. However, their use for the encapsulation of low-toxicity molecularly targeted anticancer agents has been limited. In the present study, we aimed to assess the efficacy and safety of a novel low-toxicity mTORC1/mTORC2 inhibitor (MTI-31) as a treatment for glioma when encapsulated in appropriate liposomes. Since some of the peptide-modified liposomes have been determined to be immunogenic and may have life-threatening consequences in mice, an immunogenicity-based investigation with candidate liposomal carriers was conducted. Following this study, ^DVAP (^DP^DA^DV^DR^DT^DN^DS) modified liposomes (^DVAP-liposomes) were identified as an immunologically safe carrier and therefore utilized for MTI-31 encapsulation. ^DVAP is a tumor homing peptide exhibiting high binding affinity to glucose regulated protein 78 (GRP78) overexpressed in glioma, glioma stem cells, vasculogenic mimicry and neovasculature. Modification of liposomes with ^DVAP imparts a glioma-directing property. In vitro, the developed ^DVAP-liposomes/MTI-31 were efficiently internalized by U87 cells and consequently showed a potent antiproliferation effect. In vivo, the safety and anti-glioma efficiency of ^DVAP-liposomes/MTI-31 were validated in intracranial glioma bearing BALB/c nude mice. While showing both systemic and immunological safety, ^DVAP-liposome/MTI-31 treatment resulted in a significant improvement in the median survival time (24.5 days for saline, 26 days for free MTI-31, 25 days for liposomes/MTI-31 and 36 days for ^DVAP-liposome/MTI-31). The results highlight MTI-31 as an effective anti-glioma agent when encapsulated in non-immunogenic glioma-targeted liposomes, which may contribute to the development of better anti-glioma treatment.

A window into the brain: Tools to assess pre-clinical efficacy of biomaterials-based therapies on central nervous system disorders

Therapeutic conveyance into the brain is a cardinal requirement for treatment of diverse central nervous system (CNS) disorders and associated pathophysiology. Effectual shielding of the brain by the blood-brain barrier (BBB) sieves out major proportion of therapeutics with the exception of small lipophilic molecules. Various nano-delivery systems (NDS) provide an effective solution around this obstacle owing to their small size and targeting properties. To date, these systems have been used for several pre-clinical disease models including glioma, neurodegenerative diseases and psychotic disorders. An efficacy screen for these systems involves a test battery designed to probe into the multiple facets of therapeutic delivery. Despite their wide application in redressing various disease targets, the efficacy evaluation strategies for all can be broadly grouped into four modalities, namely: histological, bio-imaging, molecular and behavioural. This review presents a comprehensive insight into all of these modalities along with their strengths and weaknesses as well as perspectives on an ideal design for a panel of tests to screen brain nano-delivery systems.

Dynamic urinary proteomic analysis in a Walker 256 intracerebral tumor model

Background

Patients with primary and metastatic brain cancer have an extremely poor prognosis, mostly due to the late diagnosis of disease. Urine, which lacks homeostatic mechanisms, is an ideal biomarker source that accumulates early and highly sensitive changes to provide information about the early stage of disease.

Methods

A rat model mimicking the local tumor growth process in the brain was established with intracerebral Walker 256 (W256) cell injection. Urine samples were collected on days 3, 5, and 8 after injection, and then analyzed by liquid chromatography coupled with tandem mass spectrometry.

Results

In the intracerebral W256 model, no obvious clinical manifestations or abnormal magnetic resonance imaging (MRI) signals were found on days 3 or 5; at these time points, 9 proteins were changed significantly in the urine of all eight tumor rats. On day 8, when tumors were detected by MRI, 25 differential proteins were identified, including 10 that have been reported to be closely related to brain metastasis or primary tumors. The differential urinary proteome was compared with those from the subcutaneous W256 model and the intracerebral C6 model. Few differential proteins overlapped, and specific differential protein patterns were observed among the three models.

Conclusions

These findings demonstrate that early changes in the urine proteome can be detected in the intracerebral W256 model. The urinary proteome can reflect the difference when tumor cells with different growth characteristics are inoculated into the brain and when identical tumor cells are inoculated into different areas, specifically, the subcutis and the brain.

Pharmacological effectors of GRP78 chaperone in cancers

The protein chaperone GRP78 is a master regulator of endoplasmic reticulum (ER) functions and is frequently over-expressed at the surface of cancer cells where it contributes to chemo-resistance. It represents a well-studied ER stress marker but an under-explored target for new drug development. This review aims to untangle the structural and functional diversity of GRP78 modulators, covering over 130 natural products, synthetic molecules, specific peptides and monoclonal antibodies that target GRP78. Several approaches to promote or to incapacitate GRP78 are presented, including the use of oligonucleotides and specific cell-delivery peptides often conjugated to cytotoxic payloads to design GRP78-targeted therapeutics. A repertoire of drugs that turn on/off GRP78 is exposed, including molecules which bind directly to GRP78, principally to its ATP site. There exist many options to regulate positively or negatively the expression of the chaperone, or to interfere with its cellular trafficking. This review provides a molecular cartography of GRP78 pharmacological effectors and adds weight to the notion that GRP78 repressors could represent promising anticancer therapeutics, notably as regards limiting chemo-resistance of cancer cells. The potential of GRP78-targeting drugs in other therapeutic modalities is also evoked.

Nanoparticle-based diagnostic and therapeutic systems for brain tumors

Many theranostic nanoparticles have been tailored for high-efficiency diagnostic or therapeutic agents or applied as carriers and might provide new possibilities for brain tumor diagnosis and treatment.

Myristic Acid-Modified DA7R Peptide for Whole-Process Glioma-Targeted Drug Delivery

The clinical treatment of aggressive glioma has been a great challenge, mainly because of the complexity of the glioma microenvironment and the existence of the blood-brain tumor barrier (BBTB)/blood-brain barrier (BBB), which severely hampers the effective accumulation of most therapeutic agents in the glioma region. Additionally, vasculogenic mimicry (VM), angiogenesis, and glioma stem cells (GSC) in malignant glioma also lead to the failure of clinical therapy. To address the aforementioned issues, a whole-process glioma-targeted drug delivery strategy was proposed. The ^DA7R peptide has effective BBTB-penetrating and notable glioma-, angiogenesis-, and VM-targeting abilities. Herein, we designed a myristic acid modified ^DA7R ligand (MC-^DA7R), which combines tumor-homing ^DA7R with BBB-penetrable MC. MC-^DA7R was then immobilized to PEGylated liposomes (MC-^DA7R-LS) to form a whole-process glioma-targeting system. MC-^DA7R-LS exhibited exceptional internalization in glioma, tumor neovascular, and brain capillary endothelial cells. Enhanced BBTB- and BBB-traversing efficiencies were also observed on MC-^DA7R-LS. Ex vivo imaging on brain tumors also demonstrated the feasibility of MC-^DA7R-LS in intracranial glioma-homing, whereas the immunofluorescence studies demonstrated its GSC and angiogenesis homing. Furthermore, doxorubicin-loaded MC-^DA7R-LS accomplished a remarkable therapeutic outcome, as a result of a synergistic improvement on the glioma microenvironment. Our study highlights the potential of the MC-modified ^DA7R peptide as a great candidate for the whole-process glioma-targeted drug delivery.

A novel peptide ligand RAP12 of LRP1 for glioma targeted drug delivery

The receptor associated protein (RAP) is a 39 kDa chaperone protein, binding tightly to low-density lipoprotein receptor-related protein-1 (LRP1) that is overexpressed in glioma, tumor neovasculature, vasculogenic mimicry (VM), the blood-brain barrier (BBB) and the blood-brain tumor barrier (BBTB). Herein, we miniaturized the RAP protein into a short peptide RAP12 (EAKIEKHNHYQK) aiding by computer-aided peptide design technique. RAP12 contained the essential lysines at the positions 253 and 256. The binding affinity of RAP12 to LRP1 was theoretically and experimentally evaluated. In cellular level, RAP12 could effectively internalize into U87, HUVEC and bEnd.3 cells. When modified on the surface of PEG-PLA micelles (RAP12-PEG-PLA), RAP12 could effectively facilitate the penetration of micelles through the BBB/BBTB in vitro/vivo. Paclitaxel-loaded RAP12-PEG-PLA could remarkably inhibit the growth of glioma cells and the formation of tumor neovasculature and VM, significantly prolong the median survival time of nude mice bearing intracranial glioma in comparison to model mice treated with plain micelles or Taxol. These results suggested that the RAP12 held the potential for multifunctional glioma-targeted drug delivery.

Enhanced glioma-targeting and stability of LGICP peptide coupled with stabilized peptide DA7R

Malignant glioma is usually accompanied by vigorous angiogenesis to provide essential nutrients. An effective glioma targeting moiety should include excellent tumor-cell homing ability as well as good neovasculature-targeting efficiency, and should be highly resistant to enzyme degradation in the bloodstream. The phage display-selected heptapeptide, the glioma-initiating cell peptide (GICP), was previously reported as a ligand for the VAV3 protein (a Rho-GTPase guanine nucleotide exchange factor), which is mainly expressed on glioma cells; the stabilized heptapeptide ^DA7R has been shown to be the ligand of both vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin-1 (NRP-1), and has demonstrated good neovasculature-targeting ability. By linking ^DA7R and GICP, a multi-receptor targeting molecule was obtained. The stability of these three peptides was evaluated and their targeting efficiency on tumor-related cells and models was compared. The ability of these peptides to cross the blood--tumor barrier (BTB) was also determined. The results indicate that the coupled Y-shaped peptide ^DA7R–GICP exhibited improved tumor and neovasculature targeting ability and had higher efficiency in crossing the BTB than either individual peptide.

Zebrafish: A Visual Model To Evaluate the Biofate of Transferrin Receptor-Targeted 7Peptide-Decorated Coumarin 6 Micelles

In the present study, the zebrafish was explored as an in vivo model to assess the biofate of transferrin receptor (TfR)-targeted coumarin 6 (C6) micelles across various biological barriers. Three 7peptide (7pep)-decorated poly(ethylene glycol)-block-poly(ε-caprolactone) micelles loaded with fluorescence coumarin 6 (7pep-M-C6) with different ligand densities were constructed with particle sizes between 30 and 40 nm. Whole-mount immunostaining revealed that the expression level of TfR in the retina, brain, and intestine increased along with development stage. Compared to unmodified micelles, 7pep-M-C6 demonstrated higher uptake efficiency in the larval zebrafish. Preinhibition of TfR with 7pep implicated the TfR-mediated endocytosis pathway in the uptake of 7pep-M-C6. Confocal images of the larval zebrafish eye and brain showed the efficient delivery of C6 across the retinal pigment epithelial to the ganglion cell layer and the significant accumulation of C6 in all brain tissues, respectively, which plateaued when the ligand density was 10%. To investigate the intestinal distribution of C6, micelles were administered to adult zebrafish via gavaging. Notably, 7pep-M-C6 enhanced the transport of C6 across the villi and increased its aggregation into the basolateral membrane of the intestine. After the oral administration of 7pep-M-C6, C6 accumulated in the eye and brain. Förster resonance energy transfer analysis suggested that intact 7pep-modified micelles could enter the epithelial cells of the intestine, brain, and eye after oral administration in adult zebrafish. In conclusion, zebrafish could be used as a model for in vivo visual assessment of the biofate of TfR-targeted drug delivery systems.