Introduction: Glioblastoma (GBM) is the most common and lethal of the central nervous system (CNS) malignancies. The initiation, progression, and infiltration ability of GBMs are attributed in part to the dysregulation of microRNAs (miRNAs). Thus, targeting dysregulated miRNAs with RNA oligonucleotides (RNA interference, RNAi) has been proposed for GBM treatment. Despite promising results in the laboratory, RNA oligonucleotides have clinical limitations that include poor RNA stability and off-target effects. RNAi therapies against GBM confront an additional obstacle, as they need to cross the blood-brain barrier (BBB). Methods: Here, we developed gold-liposome nanoparticles conjugated with the brain targeting peptides apolipoprotein E (ApoE) and rabies virus glycoprotein (RVG). First, we functionalized gold nanoparticles with oligonucleotide miRNA inhibitors (OMIs), creating spherical nucleic acids (SNAs). Next, we encapsulated SNAs into ApoE, or RVG-conjugated liposomes, to obtain SNA-Liposome-ApoE and SNA-Liposome-RVG, respectively. We characterized each nanoparticle in terms of their size, charge, encapsulation efficiency, and delivery efficiency into U87 GBM cells in vitro. Then, they were administered intravenously (iv) in GBM syngeneic mice to evaluate their delivery efficiency to brain tumor tissue. Results: SNA-Liposomes of about 30-50 nm in diameter internalized U87 GBM cells and inhibited the expression of miRNA-92b, an aberrantly overexpressed miRNA in GBM cell lines and GBM tumors. Conjugating SNA-Liposomes with ApoE or RVG peptides increased their systemic delivery to the brain tumors of GBM syngeneic mice. SNA-Liposome-ApoE demonstrated to accumulate at higher extension in brain tumor tissues, when compared with non-treated controls, SNA-Liposomes, or SNA-Liposome-RVG. Discussion: SNA-Liposome-ApoE has the potential to advance the translation of miRNAbased therapies for GBM as well as other CNS disorders.

Glioblastoma multiforme (GBM) is the most common and deadliest type of primary brain tumor with a prognosis of 14 months after diagnosis. Current treatment for GBM patients includes “total” tumor resection, temozolomide-based chemotherapy, radiotherapy or a combination of these options. Although, several targeted therapies, gene therapy, and immunotherapy are currently in the clinic and/or in clinical trials, the overall survival of GBM patients has hardly improved over the last two decades. Therefore, novel multitarget modalities are urgently needed. Recently, RNA interference (RNAi) has emerged as a novel strategy for the treatment of most cancers, including GBM. RNAi-based therapies consist of using small RNA oligonucleotides to regulate protein expression at the post-transcriptional level. Despite the therapeutic potential of RNAi molecules, systemic limitations including short circulatory stability and low release into the tumor tissue have halted their progress to the clinic. The effective delivery of RNAi molecules through the blood-brain barrier (BBB) represents an additional challenge. This review focuses on connecting the translational process of RNAi-based therapies from in vitro evidence to pre-clinical studies. We delineate the effect of RNAi in GBM cell lines, describe their effectiveness in glioma mouse models, and compare the proposed drug carriers for the effective transport of RNAi molecules through the BBB to reach the tumor in the brain. Furthermore, we summarize the most important obstacles to overcome before RNAi-based therapy becomes a reality for GBM treatment.

Glioblastoma (GBM) is the most common and aggressive of all brain tumors, with a median survival of only 14 months after initial diagnosis. Novel therapeutic approaches are an unmet need for GBM treatment. MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression at the post-transcriptional level. Several dysregulated miRNAs have been identified in all cancer types including GBM. In this study, we aimed to uncover the role of miR-143 in GBM cell lines, patient samples, and mouse models. Quantitative real-time RT-PCR of RNA extracted from formalin-fixed paraffin-embedded (FFPE) samples showed that the relative expression of miR-143 was higher in GBM patients compared to control individuals. Transient transfection of GBM cells with a miR-143 oligonucleotide inhibitor (miR-143-inh) resulted in reduced cell proliferation, increased apoptosis, and cell cycle arrest. SLC30A8, a glucose metabolism-related protein, was identified as a direct target of miR-143 in GBM cells. Moreover, multiple injections of GBM tumor-bearing mice with a miR-143-inh-liposomal formulation significantly reduced tumor growth compared to control mice. The reduced in vitro cell growth and in vivo tumor growth following miRNA-143 inhibition suggests that miR-143 is a potential therapeutic target for GBM therapy.