RNA interference therapy for glioblastoma

Engineered smart materials for RNA based molecular therapy to treat Glioblastoma

Glioblastoma (GBM) is an aggressive malignancy of the central nervous system (CNS) that remains incurable despite the multitude of improvements in cancer therapeutics. The conventional chemo and radiotherapy post-surgery have only been able to improve the prognosis slightly; however, the development of resistance and/or tumor recurrence is almost inevitable. There is a pressing need for adjuvant molecular therapies that can successfully and efficiently block tumor progression. During the last few decades, non-coding RNAs (ncRNAs) have emerged as key players in regulating various hallmarks of cancer including that of GBM. The levels of many ncRNAs are dysregulated in cancer, and ectopic modulation of their levels by delivering antagonists or overexpression constructs could serve as an attractive option for cancer therapy. The therapeutic potential of several types of ncRNAs, including miRNAs, lncRNAs, and circRNAs, has been validated in both in vitro and in vivo models of GBM. However, the delivery of these RNA-based therapeutics is highly challenging, especially to the tumors of the brain as the blood-brain barrier (BBB) poses as a major obstacle, among others. Also, since RNA is extremely fragile in nature, careful considerations must be met while designing a delivery agent. In this review we have shed light on how ncRNA therapy can overcome the limitations of its predecessor conventional therapy with an emphasis on smart nanomaterials that can aide in the safe and targeted delivery of nucleic acids to treat GBM. Additionally, critical gaps that currently exist for successful transition from viral to non-viral vector delivery systems have been identified. Finally, we have provided a perspective on the future directions, potential pathways, and target areas for achieving rapid clinical translation of, RNA-based macromolecular therapy to advance the effective treatment of GBM and other related diseases.

The role of cell membrane-coated nanoparticles as a novel treatment approach in glioblastoma

Glioblastoma multiform (GBM) is the most prevalent and deadliest primary brain malignancy in adults, whose median survival rate does not exceed 15 months after diagnosis. The conventional treatment of GBM, including maximal safe surgery followed by chemotherapy and radiotherapy, usually cannot lead to notable improvements in the disease prognosis and the tumor always recurs. Many GBM characteristics make its treatment challenging. The most important ones are the impermeability of the blood-brain barrier (BBB), preventing chemotherapeutic drugs from reaching in adequate amounts to the tumor site, intratumoral heterogeneity, and roles of glioblastoma stem cells (GSCs). To overcome these barriers, the recently-developed drug-carrying approach using nanoparticles (NPs) may play a significant role. NPs are tiny particles, usually less than 100 nm showing various diagnostic and therapeutic medical applications. In this regard, cell membrane (CM)-coated NPs demonstrated several promising effects in GBM in pre-clinical studies. They benefit from fewer adverse effects due to their specific targeting of tumor cells, biocompatibility because of their CM surfaces, prolonged half-life, easy penetrating of the BBB, and escaping from the immune reaction, making them an attractive option for GBM treatment. To date, CM-coated NPs have been applied to enhance the effectiveness of major therapeutic approaches in GBM treatment, including chemotherapy, immunotherapy, gene therapy, and photo-based therapies. Despite the promising results in pre-clinical studies regarding the effectiveness of CM-coated NPs in GBM, significant barriers like high expenses, complex preparation processes, and unknown long-term effects still hinder its mass production for the clinic. In this regard, the current study aims to provide an overview of different characteristics of CM-coated NPs and comprehensively investigate their application as a novel treatment approach in GBM.

Multifunctional nanocarriers for delivering siRNA and miRNA in glioblastoma therapy: advances in nanobiotechnology-based cancer therapy

Glioblastoma multiforme (GBM) is one of the most lethal cancer due to poor diagnosis and rapid resistance developed towards the drug. Genes associated to cancer-related overexpression of proteins, enzymes, and receptors can be suppressed using an RNA silencing technique. This assists in obtaining tumour targetability, resulting in less harm caused to the surrounding healthy cells. RNA interference (RNAi) has scientific basis for providing potential therapeutic applications in improving GBM treatment. However, the therapeutic application of RNAi is challenging due to its poor permeability across blood-brain barrier (BBB). Nanobiotechnology has evolved the use of nanocarriers such as liposomes, polymeric nanoparticles, gold nanoparticles, dendrimers, quantum dots and other nanostructures in encasing the RNAi entities like siRNA and miRNA. The review highlights the role of these carriers in encasing siRNA and miRNA and promising therapy in delivering them to the glioma cells.

Nanoparticle designs for delivery of nucleic acid therapeutics as brain cancer therapies

Glioblastoma (GBM) is an aggressive central nervous system cancer with a dismal prognosis. The standard of care involves surgical resection followed by radiotherapy and chemotherapy, but five-year survival is only 5.6% despite these measures. Novel therapeutic approaches, such as immunotherapies, targeted therapies, and gene therapies, have been explored to attempt to extend survival for patients. Nanoparticles have been receiving increasing attention as promising vehicles for non-viral nucleic acid delivery in the context of GBM, though delivery is often limited by low blood-brain barrier permeability, particle instability, and low trafficking to target brain structures and cells. In this review, nanoparticle design considerations and new advances to overcome nucleic acid delivery challenges to treat brain cancer are summarized and discussed.

RNA Interference Nanotherapeutics for Treatment of Glioblastoma Multiforme

Nucleic acid therapeutics for RNA interference (RNAi) are gaining attention in the treatment and management of several kinds of the so-called "undruggable" tumors via targeting specific molecular pathways or oncogenes. Synthetic ribonucleic acid (RNAs) oligonucleotides like siRNA, miRNA, shRNA, and lncRNA have shown potential as novel therapeutics. However, the delivery of such oligonucleotides is significantly hampered by their physiochemical (such as hydrophilicity, negative charge, and instability) and biopharmaceutical features (in vivo serum stability, fast renal clearance, interaction with extracellular proteins, and hindrance in cellular internalization) that markedly reduce their biological activity. Recently, several nanocarriers have evolved as suitable non-viral vectors for oligonucleotide delivery, which are known to either complex or conjugate with these oligonucleotides efficiently and also overcome the extracellular and intracellular barriers, thereby allowing access to the tumoral micro-environment for the better and desired outcome in glioblastoma multiforme (GBM). This Review focuses on the up-to-date advancements in the field of RNAi nanotherapeutics utilized for GBM treatment.

The Impact of Nylon-3 Copolymer Composition on the Efficiency of siRNA Delivery to Glioblastoma Cells

Glioblastoma multiforme is a devastating disease that has attracted enormous attention due to poor prognosis and high recurrence. Small interfering RNA (siRNA) in principle offers a promising therapeutic approach by the downregulation of disease-related genes via RNA interference. For efficient siRNA delivery to target sites, cationic polymers are often used in preclinical studies for the protection of siRNA and complex formation based on electrostatic interactions. In an effort to develop biocompatible and efficient nanocarriers with a translational outlook for optimal gene silencing at reduced toxicity, we synthesized two sets of nylon-3 copolymers with variable cationic content (DM or NM monomer) and hydrophobic subunits (CP monomer) and evaluated their suitability for in vitro siRNA delivery into glioblastoma cells. DM_0.4/CP_0.6 and NM_0.4/CP_0.6 polymers with similar subunit ratios were synthesized to compare the effect of different cationic subunits. Additionally, we utilized NM_0.2/CP_0.8 polymers to evaluate the impact of the different hydrophobic content in the polymer chain. The siRNA condensation ability and polymer–siRNA complex stability was evaluated by unmodified and modified SYBR gold assays, respectively. Further physicochemical characteristics, e.g., particle size and surface charge, were evaluated by dynamic light scattering and laser Doppler anemometry, whereas a relatively new method for polyplex size distribution analysis—tunable resistive pulse sensing—was additionally developed and compared to DLS measurements. Transfection efficiencies, the route of cell internalization, and protein knockdown abilities in glioblastoma cells were investigated by flow cytometry. Furthermore, cellular tolerability was evaluated by MTT and LDH assays. All the polymers efficiently condensed siRNA at N/P ratios of three, whereas polymers with NM cationic subunits demonstrated smaller particle size and lower polyplex stability. Furthermore, NM_0.2/CP_0.8 polyplexes with the highest hydrophobic content displayed significantly higher cellular internalization in comparison to more cationic formulations and successful knockdown capabilities. Detailed investigations of the cellular uptake route demonstrated that these polyplexes mainly follow clathrin-mediated endocytotic uptake mechanisms, implying high interaction capacity with cellular membranes. Taken together with conducive toxicity profiles, highly hydrophobic nylon-3 polymers provide an appropriate siRNA delivery agent for the potential treatment of glioblastoma.

The protean world of non-coding RNAs in glioblastoma

Non-coding ribonucleic acids (ncRNAs) are a diverse group of RNA molecules that are mostly not translated into proteins following transcription. We review the role of ncRNAs in the pathobiology of glioblastoma (GBM), and their potential applications for GBM therapy. Significant advances in our understanding of the protean manifestations of ncRNAs have been made, allowing us to better decipher the molecular complexity of GBM. A large number of regulatory ncRNAs appear to have a greater influence on the molecular pathology of GBM than thought previously. Importantly, also, a range of therapeutic approaches are emerging whereby ncRNA-based systems may be used to molecularly target GBM. The most successful of these is RNA interference, and some of these strategies are being evaluated in ongoing clinical trials. However, a number of limitations exist in the clinical translation of ncRNA-based therapeutic systems, such as delivery mechanisms and cytotoxicity; concerted research endeavors are currently underway in an attempt to overcome these. Ongoing and future studies will determine the potential practical role for ncRNA-based therapeutic systems in the clinical management of GBM. These applications may be especially promising, given that current treatment options are limited and prognosis remains poor for this challenging malignancy.

Lentiviral Vectors as Tools for the Study and Treatment of Glioblastoma

Glioblastoma (GBM) has the worst prognosis among brain tumors, hence basic biology, preclinical, and clinical studies are necessary to design effective strategies to defeat this disease. Gene transfer vectors derived from the most-studied lentivirus-the Human Immunodeficiency Virus type 1-have wide application in dissecting GBM specific features to identify potential therapeutic targets. Last-generation lentiviruses (LV), highly improved in safety profile and gene transfer capacity, are also largely employed as delivery systems of therapeutic molecules to be employed in gene therapy (GT) approaches. LV were initially used in GT protocols aimed at the expression of suicide factors to induce GBM cell death. Subsequently, LV were adopted to either express small noncoding RNAs to affect different aspects of GBM biology or to overcome the resistance to both chemo- and radiotherapy that easily develop in this tumor after initial therapy. Newer frontiers include adoption of LV for engineering T cells to express chimeric antigen receptors recognizing specific GBM antigens, or for transducing specific cell types that, due to their biological properties, can function as carriers of therapeutic molecules to the cancer mass. Finally, LV allow the setting up of improved animal models crucial for the validation of GBM specific therapies.

MicroRNA-184 promotes proliferation ability of glioma cells by regulating FOXO3

OBJECTIVES

To investigate the effect of microRNA (miR-184) on regulating the genesis, development and proliferation of glioma cells.

METHODS

Lipidosome was used to transfect miR-184 mimic and inhibitor to glioma cell line, and the cell proliferation ability changes were determined by MTT and plate cloning experiment after the transfection. WB test was used to measure the levels of cyclinD1, p27 and FOXO3. Meanwhile, QPCR was used to detect miR-184 expression in glioma cell line, glioma tissues and adjacent tissues. Luciferase experiment was used to test 3'UTR gene targeting regulation of miR-184 and FOXO3.

RESULTS

QPCR results showed a significant lower miR-184 expression level in glioma cell line and glioma tissues than that in juxtacancerous tissue. MTT and plate cloning experiments have shown that after over-expressing of miR-184, the cell proliferation capacity of glioma U87 and T98G was significantly increased, which was significantly inhibited after the inhibition of miR-184. WB results showed a lower expression level of p27 in U87 and T98G cells, and a higher expression level of cyclinD1 after over-expressing of miR-184 was observed. However, a lower expression level of cyclinD1 and a higher expression level of p27 after the inhibition of miR-184. The luciferase activity was inhibited after the over-expressing of miR-184.

CONCLUSIONS

MiR-184 can affect the proliferation abilities of glioma cells and regulate the cell cycle related protein. It plays an important role in the occurrence and development of gliomas.

Toward an effective strategy in glioblastoma treatment. Part II: RNA interference as a promising way to sensitize glioblastomas to temozolomide

RNA interference (RNAi) is a strategy of gene regulation that has opened up many opportunities for the treatment of cancers, especially glioblastoma multiforme (GBM). This strategy reduced the expression of many proteins involved in the resistance of these tumors to anticancer drugs, particularly to temozolomide (TMZ). A significant research effort has gone into RNAi delivery and target selection for clinical application of this new discovery in the treatment of GBMs. However, some limitations must be resolved to enhance the safety of RNAi-based therapeutics and to reduce their immune response. In this review, the mechanism of RNAi will be described. Moreover, the opportunities offered by RNAi strategy to reverse the phenotype of these tumor cells as well as prospects and challenges ahead in the RNAi-based therapy will be discussed.

Current Therapeutic Advances Targeting EGFR and EGFRvIII in Glioblastoma

Epidermal growth factor receptor (EGFR) and EGFRvIII analysis is of current interest in glioblastoma – the most common malignant primary CNS tumor, because of new EGFRvIII vaccine trials underway. EGFR activation in glioblastoma promotes cellular proliferation via activation of MAPK and PI3K–Akt pathways, and EGFRvIII is the most common variant, leading to constitutively active EGFR. This review explains EGFR and EGFRvIII signaling in GBM; describes targeted therapy approaches to date including tyrosine kinase inhibitor, antibody-based therapies, vaccines and pre-clinical RNA-based therapies, and discusses the difficulties encountered with these approaches including pathway redundancy and intratumoral heterogeneity.

Glioblastoma multiforme - an overview

Glioblastoma multiforme is a central nervous system tumor of grade IV histological malignancy according to the WHO classification. Over 90% of diagnosed glioblastomas multiforme cases are primary gliomas, arising from normal glial cells through multistep oncogenesis. The remaining 10% are secondary gliomas originating from tumors of lower grade. These tumors expand distinctly more slowly. Although genetic alterations and deregulations of molecular pathways leading to both primary and secondary glioblastomas formation differ, morphologically they do not reveal any significant differences. Glioblastoma is a neoplasm that occurs spontaneously, although familial gliomas have also been noted. Caucasians, especially those living in industrial areas, have a higher incidence of glioblastoma. Cases of glioblastoma in infants and children are also reported. The participation of sex hormones and viruses in its oncogenesis was also suggested. Progression of glioblastoma multiforme is associated with deregulation of checkpoint G1/S of a cell cycle and occurrence of multiple genetic abnormalities of tumor cells. Metastases of glioblastoma multiforme are rarely described. Treatment of glioblastoma multiforme includes tumor resection, as well as radiotherapy and chemotherapy. Drugs inhibiting integrin signaling pathways and immunotherapy are also employed. Treatment modalities and prognosis depend on the tumor localization, degree of its malignancy, genetic profile, proliferation activity, patient's age and the Karnofsky performance scale score. Although the biology of glioblastoma multiforme has recently been widely investigated, the studies summarizing the knowledge of its development and treatment are still not sufficient in terms of comprehensive brain tumor analysis.

A peptide-mediated targeting gene delivery system for malignant glioma cells

Glioblastoma multiforme (GBM) is the most common and malignant glioma. Although there has been considerable progress in treatment strategies, the prognosis of many patients with GBM remains poor. In this work, polyethylenimine (PEI) and the VTWTPQAWFQWV (VTW) peptide were modified and synthesized into GBM-targeting nanoparticles. The transfection efficiency of U-87 (human glioblastoma) cells was evaluated using fluorescence microscopy and flow cytometry. Cell internalization was investigated to verify the nanoparticle delivery into the cytoplasm. Results showed that the methods of polymer conjugation and the amount of VTW peptide were important factors to polymer synthesis and transfection. The PEI-VTW₂₀ nanoparticles increased the transfection efficiency significantly. This report describes the use of VTW peptide-based PEI nanoparticles for intracellular gene delivery in a GBM cell-specific manner.

Current progress for the use of miRNAs in glioblastoma treatment

Glioblastoma (GBM) is a highly aggressive brain cancer with the worst prognosis of any central nervous system disease despite intensive multimodal therapy. Inevitably, glioblastoma is fatal, with recurrence of treatment-resistant tumour growth at distal sites leading to an extremely low median survival rate of 12-15 months from the time of initial diagnosis. With the advent of microarray and gene profiling technology, researchers have investigated trends in genetic alterations and, in this regard, the role of dysregulated microRNAs (highly conserved endogenous small RNA molecules) in glioblastoma has been studied with a view to identifying novel mechanisms of acquired drug resistance and allow for development of microRNA (miRNA)-based therapeutics for GBM patients. Considering the development of miRNA research from initial association to GBM to commercial development of miR-based therapeutics in less than a decade, it is not beyond reasonable doubt to anticipate significant advancements in this field of study, hopefully with the ultimate conclusion of improved patient outcome. This review discusses the recent advancements in miRNA-based therapeutic development for use in glioblastoma treatment and the challenges faced with respect to in vivo and clinical application.

Epidermal growth factor receptor as a therapeutic target in glioblastoma

Glioblastoma represents one of the most challenging problems in neurooncology. Among key elements driving its behavior is the transmembrane epidermal growth factor receptor family, with the first member epidermal growth factor receptor (EGFR) centered in most studies. Engagement of the extracellular domain with a ligand activates the intracellular tyrosine kinase (TK) domain of EGFR, leading to autophosphorylation and signal transduction that controls proliferation, gene transcription, and apoptosis. Oncogenic missense mutations, deletions, and insertions in the EGFR gene are preferentially located in the extracellular domain in glioblastoma and cause constitutive activation of the receptor. The mutant EGFR may also transactivate other cell surface molecules, such as additional members of the EGFR family and the platelet-derived growth factor receptor, which ignite signaling cascades that synergize with the EGFR-initiated cascade. Because of the cell surface location and increased expression of the receptor along with its important biological function, EGFR has triggered much effort for designing targeted therapy. These approaches include TK inhibition, monoclonal antibody, vaccine, and RNA-based downregulation of the receptor. Treatment success requires that the drug penetrates the blood-brain barrier and has low systemic toxicity but high selectivity for the tumor. While the blockade of EGFR-dependent processes resulted in experimental and clinical treatment success, cells capable of using alternative signaling ultimately escape this strategy. A combination of interventions targeting tumor-specific cell surface regulators along with convergent downstream signaling pathways will likely enhance efficacy. Studies on EGFR in glioblastoma have revealed much information about the complexity of gliomagenesis and also facilitated the development of strategies for targeting drivers of tumor growth and combination therapies with increasing complexity.

Nucleic acids in human glioma treatment: innovative approaches and recent results

Gliomas are the most common primary central nervous system tumors with a dismal prognosis. Despite recent advances in surgery, radiotherapy, and chemotherapy, current treatment regimens have a modest survival benefit. A crucial challenge is to deliver drugs effectively to invasive glioma cells residing in a sanctuary within the central nervous system. New therapies are essential, and oligonucleotide-based approaches, including antisense, microRNAs, small interfering RNAs, and nucleic acid aptamers, may provide a viable strategy. Thanks to their unique characteristics (low size, good affinity for the target, no immunogenicity, chemical structures that can be easily modified to improve their in vivo applications), these molecules may represent a valid alternative to antibodies particularly to overcome challenges presented by the blood-brain barrier. Here we will discuss recent results on the use of oligonucleotides that will hopefully provide new effective treatment for gliomas.

Shared molecular targets in pediatric gliomas and ependymomas

BACKGROUND

Recent advances in multidisciplinary treatment approaches have improved the overall prognosis of pediatric brain tumors, but some patients remain refractory to treatment and do poorly. Several molecularly targeted therapies are under development for the treatment of brain tumors, and high-grade gliomas in adults are a particular area of study.

PROCEDURE

To better understand if these new therapies can be used in pediatric populations, we examined the expression of the following seven marker genes involved in signaling pathways targeted by new therapies: β-catenin, suppressor of fused (SUFU), erythroblastic leukemia viral oncogene homolog (ERBB) 2, platelet-derived growth factor receptorα (PDGFRα), proliferating cell nuclear antigen (PCNA), secreted protein acid and rich in cysteine (SPARC), and granulocyte colony-stimulating factor receptor (G-CSFR). Samples from 27 patients with the primitive neuroectodermal tumor (PNET)/medulloblastomas (MBs) (n = 8), ependymomas (n = 5), or gliomas (n = 14) were assessed by quantitative real-time PCR. [Correction made here after initial online publication]. We assigned an EXP score to compare across samples and determined the levels of gene expression among tumor cell types.

RESULTS

Gene expression varied among the different tumors, but, within a tumor type, clear expression patterns were seen. The expression of SUFU, ERBB2, and PCNA in metastatic MBs were greater than that seen in non-metastatic MBs. Most glioma cases highly expressed PDGFRα and G-CSFR. Additionally, the expression patterns of gliomas and ependymomas were similar (r = 0.77, P = 0.04), but PNET/MBs substantially differed from gliomas (r = -0.37, P = 0.41) or ependymomas (r = 0.23, P = 0.62).

CONCLUSIONS

The development of new drugs targeting up-regulated pathways may be useful for the treatment of pediatric brain tumors. As new drugs are developed, gliomas and ependymomas may be treated with similar compounds.

Silencing IL-13Rα2 promotes glioblastoma cell death via endogenous signaling

Glioblastoma multiforme (GBM) is one of the most lethal forms of cancer, with a survival rate of only 13% to 27% within 2 years of diagnosis despite optimal medical treatment. We hypothesize that the presence of a unique IL-13Rα2 decoy receptor prevents GBM apoptosis. This receptor has a high affinity for interleukin-13 (IL-13), binds the cytokine, and competitively inhibits the intracellular signaling cascade initiated by IL-13. In cells lacking the IL-13Rα2 decoy receptor, IL-13 initiates the production of 15-lipoxygenase-1 (15-LOX-1), which has been implicated in cellular apoptosis. Our group and others have shown that induction of 15-LOX-1 correlates with tumor cell death in colorectal, pancreatic, and prostate cancer. How 15-LOX-1 induces apoptosis remains unclear. Preliminary evidence in GBM cells implicates an apoptotic process mediated by PPARγ. 15-LOX-1 metabolites can modulate PPARγ and activation of PPARγ can suppress tumor growth. We hypothesize that in GBM, IL-13 can induce 15-LOX-1, which regulates cell apoptosis via signaling through PPARγ and that expression of IL-13Rα2 prevents apoptosis and contributes to tumor growth. Our in vitro and in vivo data support this. Knocking down IL-13Rα2 with short interfering RNA dramatically induces 15-LOX-1 expression, promotes apoptosis, and reduces GBM tumor growth in vivo. These findings identify a mechanism for eliminating the blockade of endogenous IL-13 signaling and for promotion of apoptosis, and characterize a role for 15-LOX-1 in GBM apoptosis. Identifying a mechanistic pathway that can be targeted for pharmacologic intervention will have applied implications to developing novel and effective treatments of GBM.

Silencing of ferrochelatase enhances 5-aminolevulinic acid-based fluorescence and photodynamic therapy efficacy

Background:

Recurrence of glioma frequently occurs within the marginal area of the surgical cavity due to invading residual cells. 5-Aminolevulinic acid (5-ALA) fluorescence-guided resection has been used as effective therapeutic modalities to improve discrimination of brain tumour margins and patient prognosis. However, the marginal areas of glioma usually show vague fluorescence, which makes tumour identification difficult, and the applicability of 5-ALA-based photodynamic therapy (PDT) is hampered by insufficient therapeutic efficacy in glioma tissues.

Methods:

To overcome these issues, we assessed the expression of ferrochelatase (FECH) gene, which encodes a key enzyme that catalyses the conversion of protoporphyrin IX (PpIX) to heme, in glioma surgical specimens and manipulated FECH in human glioma cell lines.

Results:

Prominent downregulation of FECH mRNA expression was found in glioblastoma tissues compared with normal brain tissues, suggesting that FECH is responsible for PpIX accumulation in glioblastoma cells. Depletion of FECH by small interference RNA enhanced PpIX fluorescence after exposure to 5-ALA concomitant with increased intracellular PpIX accumulation in glioma cells. Silencing of FECH caused marked growth inhibition and apoptosis induction by PDT in glioma cells.

Conclusion:

These results suggest that knockdown of FECH is a potential approach to enhance PpIX fluorescent quality for optimising the subjective discrimination of vague fluorescence and improving the effect of 5-ALA-PDT.