Modulation of microRNA editing, expression and processing by ADAR2 deaminase in glioblastoma.

Background: ADAR enzymes convert adenosines to inosines within double-stranded RNAs, including microRNA (miRNA) precursors, with important consequences on miRNA retargeting and expression. ADAR2 activity is impaired in glioblastoma and its rescue has anti-tumoral effects. However, how ADAR2 activity may impact the miRNome and the progression of glioblastoma is not known. Results: By integrating deep-sequencing and array approaches with bioinformatics analyses and molecular studies, we show that ADAR2 is essential to edit a small number of mature miRNAs and to significantly modulate the expression of about 90 miRNAs in glioblastoma cells. Specifically, the rescue of ADAR2 activity in cancer cells recovers the edited miRNA population lost in glioblastoma cell lines and tissues, and rebalances expression of onco-miRNAs and tumor suppressor miRNAs to the levels observed in normal human brain. We report that the major effect of ADAR2 is to reduce the expression of a large number of miRNAs, most of which act as onco-miRNAs. ADAR2 can edit miR-222/221 and miR-21 precursors and decrease the expression of the corresponding mature onco-miRNAs in vivo and in vitro, with important effects on cell proliferation and migration. Conclusions: Our findings disclose an additional layer of complexity in miRNome regulation and provide information to better understand the impact of ADAR2 editing enzyme in glioblastoma. We propose that ADAR2 is a key factor for maintaining edited-miRNA population and balancing the expression of several essential miRNAs involved in cancer

MiRNAs as novel adipokines : obesity-related circulating MiRNAs influence chemosensitivity in cancer patients

Adipose tissue is an endocrine organ, capable of regulating distant physiological processes in other tissues via the release of adipokines into the bloodstream. Recently, circulating adipose-derived microRNAs (miRNAs) have been proposed as a novel class of adipokine, due to their capacity to regulate gene expression in tissues other than fat. Circulating levels of adipokines are known to be altered in obese individuals compared with typical weight individuals and are linked to poorer health outcomes. For example, obese individuals are known to be more prone to the development of some cancers, and less likely to achieve event-free survival following chemotherapy. The purpose of this review was twofold; first to identify circulating miRNAs which are reproducibly altered in obesity, and secondly to identify mechanisms by which these obesity-linked miRNAs might influence the sensitivity of tumors to treatment. We identified 8 candidate circulating miRNAs with altered levels in obese individuals (6 increased, 2 decreased). A second literature review was then performed to investigate if these candidates might have a role in mediating resistance to cancer treatment. All of the circulating miRNAs identified were capable of mediating responses to cancer treatment at the cellular level, and so this review provides novel insights which can be used by future studies which aim to improve obese patient outcomes

miRNAs link metabolic reprogramming to oncogenesis

The most profound biochemical phenotype of cancer cells is their ability to metabolize glucose to lactate, even under aerobic conditions. This alternative metabolic circuitry is sufficient to support the biosynthetic and energy requirements for cancer cell proliferation and metastasis. Alterations in oncogenes and tumor suppressor genes are involved in the metabolic switch of cancer cells to aerobic glycolysis, increased glutaminolysis and fatty acid biosynthesis. MiRNAs mediate fine-tuning of genes involved directly or indirectly in cancer metabolism. In this review, we discuss the regulatory role of miRNAs on enzymes, signaling pathways and transcription factors involved in glucose and lipid metabolism. We further consider the therapeutic potential of metabolism-related miRNAs in cancer

New insights into the biological role of mammalian ADARs; the RNA editing proteins

The ADAR proteins deaminate adenosine to inosine in double-stranded RNA which is one of the most abundant modifications present in mammalian RNA. Inosine can have a profound effect on the RNAs that are edited, not only changing the base-pairing properties, but can also result in recoding, as inosine behaves as if it were guanosine. In mammals there are three ADAR proteins and two ADAR-related proteins (ADAD) expressed. All have a very similar modular structure; however, both their expression and biological function differ significantly. Only two of the ADAR proteins have enzymatic activity. However, both ADAR and ADAD proteins possess the ability to bind double-strand RNA. Mutations in ADARs have been associated with many diseases ranging from cancer, innate immunity to neurological disorders. Here, we will discuss in detail the domain structure of mammalian ADARs, the effects of RNA editing, and the role of ADARs in human diseases

Advances in the design and development of oncolytic measles viruses.

A successful oncolytic virus is one that selectively propagates and destroys cancerous tissue without causing excessive damage to the normal surrounding tissue. Oncolytic measles virus (MV) is one such virus that exhibits this characteristic and thus has rapidly emerged as a potentially useful anticancer modality. Derivatives of the Edmonston MV vaccine strain possess a remarkable safety record in humans. Promising results in preclinical animal models and evidence of biological activity in early phase trials contribute to the enthusiasm. Genetic modifications have enabled MV to evolve from a vaccine agent to a potential anticancer therapy. Specifically, alterations of the MV genome have led to improved tumor selectivity and delivery, therapeutic potency, and immune system modulation. In this article, we will review the advancements that have been made in the design and development of MV that have led to its use as a cancer therapy. In addition, we will discuss the evidence supporting its use, as well as the challenges associated with MV as a potential cancer therapeutic

Differential MicroRNA Expression in Glioblastoma as a Therapeutic Target or Potential Biomarker

MicroRNA (miRNA) is an epigenetic factor that plays an important role in the post-transcriptional regulation of gene and protein expression. Recent research has shown that in many types of cancer, differentially expressed levels of certain types of miRNA are significantly correlated with the transformation of and ongoing issues caused by cancer cells. Specifically, in Glioblastoma, one of the most lethal and aggressive human cancers, differential levels of miRNAs contribute to the cell’s lack of pro-apoptotic gene presence and its high resistance to current treatments. Results from current studies could provide information about which microRNAs are differentially expressed in glioblastoma when compared to normal astrocytes. Differentially expressed microRNAs may be used as a biomarker for diagnosis or a potential therapeutic target for Glioblastoma treatment

miRNAs as Influencers of Cell-Cell Communication in Tumor Microenvironment

microRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level, inducing the degradation of the target mRNA or translational repression. MiRNAs are involved in the control of a multiplicity of biological processes, and their absence or altered expression has been associated with a variety of human diseases, including cancer. Recently, extracellular miRNAs (ECmiRNAs) have been described as mediators of intercellular communication in multiple contexts, including tumor microenvironment. Cancer cells cooperate with stromal cells and elements of the extracellular matrix (ECM) to establish a comfortable niche to grow, to evade the immune system, and to expand. Within the tumor microenvironment, cells release ECmiRNAs and other factors in order to influence and hijack the physiological processes of surrounding cells, fostering tumor progression. Here, we discuss the role of miRNAs in the pathogenesis of multicomplex diseases, such as Alzheimer's disease, obesity, and cancer, focusing on the contribution of both intracellular miRNAs, and of released ECmiRNAs in the establishment and development of cancer niche. We also review growing evidence suggesting the use of miRNAs as novel targets or potential tools for therapeutic applications

Tumor targeting gold nanoparticles for delivery of RNA and DNA oligonucleotide therapies for glioblastoma.

Glioblastoma (GBM) brain tumors are highly aggressive gliomas due to genetic and cellular heterogeneity. Current GBM treatment consists of surgical resection of the tumor combined with radio- or chemo-therapies. While these treatments have increased the life expectancy for GBM patients up to 20 months, they have had little effect on the 5-year survival rate. The complex cellular and genetic composition of the tumor makes current treatments less effective long term. One approach to developing more effective GBM treatments is to customize nanoparticle-based drug delivery systems that can directly target the aberrant gene expression patterns within a particular GBM tumor. Delivery systems that include oligonucleotide therapies are ideal for this approach due to their ease of synthesis and ability to tailor the oligonucleotide base sequence to allow the targeting of specific gene sequences and proteins. Two therapeutically relevant classes of oligonucleotides, DNA aptamers (e.g., AS1411) and RNA-interfering anti-sense microRNAs (anti-miRs), have exhibited anti-GBM properties. However, their use as standalone therapies is hindered by instability within in vitro and in vivo environments and the inability to cross some biological barriers. The conjugation of individual oligonucleotides to the surface of gold nanoparticles (GNPs) has been shown to help overcome these difficulties to make AS1411 and anti-miRs viable therapeutics for GBM; however, the conjugation of both oligonucleotides to GNPs has not been investigated. This dissertation presents a novel GNP therapy incorporating AS1411 and an anti-miR as a multi-faceted therapy against GBM. Anti-miR-21 (A21) targets miR-21, a microRNA implicated in the increased aggressiveness of GBM tumors. U-87 MG GBM cells treated with GNPs coated with AS1411 and the polymer poly (ethylene glycol) (PEG/AS1411 GNPs) displayed decreased cellular metabolic activity and growth with altered cell morphology. The GNPs were optimized based on the PEG to AS1411 ratio to maximize these bioactive effects against GBM cells. An optimal ratio of 1:3 PEG to AS1411 conjugated GNPs exhibited ~ 72% inhibition of cellular metabolic activity, reduced growth by 75%, and profoundly affected cellular morphology. The effects of AS1411 were enhanced upon conjugation to GNPs. Additionally, using a base-substituted analog of AS1411 showed that the effects on U-87 MG cells were specific to the sequence of AS1411. In addition, this dissertation details the synthesis of AS1411 GNPs coated with A21 (PEG/AS1411/A21 GNPs) and investigates the benefit of A21 addition to PEG/AS1411 GNPs. Treatment of U-87 MG cells with PEG/AS1411/A21 GNPs retained the effects seen from PEG/AS1411 GNPs and significantly lowered the motility rate of U-87 MG cells. PEG/AS1411/A21 GNPs showed additional effects on gene expression patterns of U-87 MG cells due to A21 addition. PEG/AS1411/A21 GNPs reduced miR-21 expression 3-fold in U-87 MG cells. The ability of PEG/AS1411/A21 GNPs to influence the expression of miR-21-associated proteins PTEN and STAT3 within U-87 MG cells was also investigated. The in vivo performance of PEG/AS1411 GNPs, with or without A21, was investigated within a mouse orthotopic xenograft model of GBM. Both GNP types were shown to cross the blood-brain barrier and influence tumor progression. Mice treated with PEG/AS1411 GNPs ultimately survived longer (47 days post-tumor implantation) than untreated mice (37.5 days

Prognostic microRNAs in high-grade glioma reveal a link to oligodendrocyte precursor differentiation.

MicroRNA expression can be exploited to define tumor prognosis and stratification for precision medicine. It remains unclear whether prognostic microRNA signatures are exclusively tumor grade and/or molecular subtype-specific, or whether common signatures of aggressive clinical behavior can be identified. Here, we defined microRNAs that are associated with good and poor prognosis in grade III and IV gliomas using data from The Cancer Genome Atlas. Pathway analysis of microRNA targets that are differentially expressed in good and poor prognosis glioma identified a link to oligodendrocyte development. Notably, a microRNA expression profile that is characteristic of a specific oligodendrocyte precursor cell type (OP1) correlates with microRNA expression from 597 of these tumors and is consistently associated with poor patient outcome in grade III and IV gliomas. Our study reveals grade-independent and subtype-independent prognostic molecular signatures in high-grade glioma and provides a framework for investigating the mechanisms of brain tumor aggressiveness