PDGF-B-mediated downregulation of miR-21: new insights into PDGF signaling in glioblastoma

miRNA in Molecular Diagnostics

MicroRNAs are a class of small non-coding RNA molecules that regulate gene expression on post-transcriptional level. Their biogenesis consists of a complex series of sequential processes, and they regulate expression of many genes involved in all cellular processes. Their function is essential for maintaining the homeostasis of a single cell; therefore, their aberrant expression contributes to development and progression of many diseases, especially malignant tumors and viral infections. Moreover, they can be associated with certain states of a specific disease, obtained in the least invasive manner for patients and analyzed with basic molecular methods used in clinical laboratories. Because of this, they have a promising potential to become very useful biomarkers and potential tools in personalized medicine approaches. In this review, miRNAs biogenesis, significance in cancer and infectious diseases, and current available test and methods for their detection are summarized.

Recent Trends of microRNA Significance in Pediatric Population Glioblastoma and Current Knowledge of Micro RNA Function in Glioblastoma Multiforme

Central nervous system tumors are a significant problem for modern medicine because of their location. The explanation of the importance of microRNA (miRNA) in the development of cancerous changes plays an important role in this respect. The first papers describing the presence of miRNA were published in the 1990s. The role of miRNA has been pointed out in many medical conditions such as kidney disease, diabetes, neurodegenerative disorder, arthritis and cancer. There are several miRNAs responsible for invasiveness, apoptosis, resistance to treatment, angiogenesis, proliferation and immunology, and many others. The research conducted in recent years analyzing this group of tumors has shown the important role of miRNA in the course of gliomagenesis. These particles seem to participate in many stages of the development of cancer processes, such as proliferation, angiogenesis, regulation of apoptosis or cell resistance to cytostatics.

PDGF/PDGFR axis in the neural systems

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) are expressed in several cell types including the brain cells such as neuronal progenitors, neurons, astrocytes, and oligodendrocytes. Emerging evidence shows that PDGF-mediated signaling regulates diverse functions in the central nervous system (CNS) such as neurogenesis, cell survival, synaptogenesis, modulation of ligand-gated ion channels, and development of specific types of neurons. Interestingly, PDGF/PDFGR signaling can elicit paradoxical roles in the CNS, depending on the cell type and the activation stimuli and is implicated in the pathogenesis of various neurodegenerative diseases. This review summarizes the role of PDGFs/PDGFRs in several neurodegenerative diseases such as Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, brain cancer, cerebral ischemia, HIV-1 and drug abuse. Understanding PDGF/PDGFR signaling may lead to novel approaches for the future development of therapeutic strategies for combating CNS pathologies.

miR-21 Is Overexpressed in Hydatidiform Mole Tissues and Promotes Proliferation, Migration, and Invasion in Choriocarcinoma Cells

OBJECTIVE

The aims of this study were to make clear whether miR-21 was dysregulated in hydatidiform mole (HM) tissues and choriocarcinoma (CCA) cells, to elucidate whether aberrant miR-21 expression would affect the function of CCA cells, and to find out whether there was a relationship between miR-21 and AKT, PDCD4, and PTEN in CCA cells.

METHODS

Fresh and formalin-fixed, paraffin-embedded trophoblastic tissues (normal first trimester placentas and HMs) were retrieved from the biobank in the International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University. Choriocarcinoma JAR and JEG-3 cells were cultured. Expression of miR-21 in trophoblast cells and tissues was examined by quantitative real-time polymerase chain reaction. Location and distribution of miR-21 in trophoblast tissues were determinated by in situ hybridization and fluorescent in situ hybridization. The effect of miR-21 on JAR and JEG-3 cells was tested by miR-21 mimics and inhibitor transfection, followed by cell viability assay, flow cytometric analysis, and Transwell analysis. Interaction between miR-21 and its target genes in CCA cells was verified by quantitative real-time polymerase chain reaction, Western blot, and luciferase report system.

RESULTS

We originally found miR-21 was markedly upregulated in HM tissues compared with normal first trimester placentas. The expression of miR-21 was exclusively confined in trophoblastic layers. Furthermore, we discovered miR-21 was significantly increased in JAR and JEG-3 cells compared with normal primary human trophoblastic cells. Moreover, we demonstrated miR-21 could promote proliferation, migration, and invasion of CCA cells. We furthermore proved miR-21 negatively regulated PDCD4 and PTEN in CCA cells and targeted to PDCD4 3'UTR directly. In addition, we confirmed that miR-21 could activate Akt pathway by phosphorylating Akt at Ser 473.

CONCLUSIONS

Our results suggested miR-21 was responsible for aggressive phenotype of gestational trophoblastic disease and had the potential diagnostic and therapeutic values for gestational trophoblastic neoplasm.

MicroRNA‑518b functions as a tumor suppressor in glioblastoma by targeting PDGFRB

Glioblastoma (GBM) is the most common and aggressive type of primary human brain tumor in China. Dysregulated microRNA (miRNA/miR) expression has been hypothesized to serve a role in the tumorigenesis and progression of human GBM. To explore the potential mechanisms affecting GBM tumorigenesis, the function of miR-518b in regulating GBM cell proliferation and angiogenesis was examined in vitro by CCK-8 and tube formation assay and in vivo by xenograft assay. The present study demonstrated that the expression of miR-518b was downregulated in GBM tissues and in GBM cell lines (U87 and U251). In addition, the expression levels of miR-518b were highly associated with tumor size, World Health Organization grade and prognosis. Furthermore, overexpression of miR-518b suppressed GBM cell proliferation and angiogenesis, and induced GBM cell apoptosis in vitro and in vivo. Overexpression of miR-518b also inhibited the expression of platelet-derived growth factor receptor β (PDGFRB), and the present study confirmed that the 3′ untranslated region (3′UTR) of PDGFRB was a direct target of miR-518b. In conclusion, to the best of our knowledge, the present study is the first to present evidence suggesting that miR-518b may serve as a potential marker and target in GBM treatment.

Current View of microRNA Processing

Small evolutionarily conserved noncoding RNAs, microRNAs (miRNAs), regulate gene expression either by translational repression or by mRNA degradation in mammals. miRNAs play functional roles in diverse physiological and pathological processes. miRNA processing is accurately regulated through multifarious factors. The canonical miRNA processing pathway consists of four sequential steps: (a) miRNA gene is transcribed into primary miRNA (pri-miRNA) mainly by RNA polymerase II; (b) pri-miRNA is processed into precursor miRNA (pre-miRNA) through microprocessor complex; (c) pre-miRNA is exported from the nucleus to the cytoplasm with the assistance of Exportin 5 (EXP5/XP05) protein; and (d) pre-miRNA is further processed into mature miRNA via Dicer. Emerging evidence has also demonstrated that some miRNAs undergo alternative processing pathways. Dysregulation of miRNA processing is closely related to tumorigenesis. Here, we review the current advances in the knowledge of miRNA processing and briefly discuss its impact on human cancers.

microRNAs as pharmacogenomic biomarkers for drug efficacy and drug safety assessment

Much evidence has documented that microRNAs (miRNAs) play an important role in the modulation of interindividual variability in the production of drug metabolizing enzymes and transporters (DMETs) and nuclear receptors (NRs) through multidirectional interactions involving environmental stimuli/stressors, the expression of miRNA molecules and genetic polymorphisms. MiRNA expression has been reported to be affected by drugs and miRNAs themselves may affect drug metabolism and toxicity. In cancer research, miRNA biomarkers have been identified to mediate intrinsic and acquired resistance to cancer therapies. In drug safety assessment, miRNAs have been found associated with cardiotoxicity, hepatotoxicity and nephrotoxicity. This review article summarizes published studies to show that miRNAs can serve as early biomarkers for the evaluation of drug efficacy and drug safety.

Glioblastoma: molecular pathways, stem cells and therapeutic targets

Glioblastoma (GBM), a WHO-defined Grade IV astrocytoma, is the most common and aggressive CNS malignancy. Despite current treatment modalities, the survival time remains dismal. The main cause of mortality in patients with this disease is reoccurrence of the malignancy, which is attributed to treatment-resistant cancer stem cells within and surrounding the primary tumor. Inclusion of novel therapies, such as immuno- and DNA-based therapy, may provide better means of treating GBM. Furthermore, manipulation of recently discovered non-coding microRNAs, some of which regulate tumor growth through the development and maintenance of GBM stem cells, could provide new prospective therapies. Studies conducted by The Cancer Genome Atlas (TCGA) also demonstrate the role of molecular pathways, specifically the activated PI3K/AKT/mTOR pathway, in GBM tumorigenesis. Inhibition of the aforementioned pathway may provide a more direct and targeted method to GBM treatment. The combination of these treatment modalities may provide an innovative therapeutic approach for the management of GBM.

Surprisal analysis of Glioblastoma Multiform (GBM) microRNA dynamics unveils tumor specific phenotype

Gliomablastoma multiform (GBM) is the most fatal form of all brain cancers in humans. Currently there are limited diagnostic tools for GBM detection. Here, we applied surprisal analysis, a theory grounded in thermodynamics, to unveil how biomolecule energetics, specifically a redistribution of free energy amongst microRNAs (miRNAs), results in a system deviating from a non-cancer state to the GBM cancer -specific phenotypic state. Utilizing global miRNA microarray expression data of normal and GBM patients tumors, surprisal analysis characterizes a miRNA system response capable of distinguishing GBM samples from normal tissue biopsy samples. We indicate that the miRNAs contributing to this system behavior is a disease phenotypic state specific to GBM and is therefore a unique GBM-specific thermodynamic signature. MiRNAs implicated in the regulation of stochastic signaling processes crucial in the hallmarks of human cancer, dominate this GBM-cancer phenotypic state. With this theory, we were able to distinguish with high fidelity GBM patients solely by monitoring the dynamics of miRNAs present in patients' biopsy samples. We anticipate that the GBM-specific thermodynamic signature will provide a critical translational tool in better characterizing cancer types and in the development of future therapeutics for GBM.

The nerve growth factor signaling and its potential as therapeutic target for glaucoma

Neuroprotective therapies which focus on factors leading to retinal ganglion cells (RGCs) degeneration have been drawing more and more attention. The beneficial effects of nerve growth factor (NGF) on the glaucoma have been recently suggested, but its effects on eye tissue are complex and controversial in various studies. Recent clinical trials of systemically and topically administrated NGF demonstrate that NGF is effective in treating several ocular diseases, including glaucoma. NGF has two receptors named high affinity NGF tyrosine kinase receptor TrkA and low affinity receptor p75NTR. Both receptors exist in cells in retina like RGC (expressing TrkA) and glia cells (expressing p75NTR). NGF functions by binding to TrkA or p75NTR alone or both together. The binding of NGF to TrkA alone in RGC promotes RGC's survival and proliferation through activation of TrkA and several prosurvival pathways. In contrast, the binding of NGF to p75NTR leads to apoptosis although it also promotes survival in some cases. Binding of NGF to both TrkA and p75NTR at the same time leads to survival in which p75NTR functions as a TrkA helping receptor. This review discusses the current understanding of the NGF signaling in retina and the therapeutic implications in the treatment of glaucoma.

Restoring TRAIL mediated signaling in ovarian cancer cells

Ovarian cancer has emerged as a multifaceted and genomically complex disease. Genetic/epigenetic mutations, suppression of tumor suppressors, overexpression of oncogenes, rewiring of intracellular signaling cascades and loss of apoptosis are some of the deeply studied mechanisms. In vitro and in vivo studies have highlighted different molecular mechanisms that regulate tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mediated apoptosis in ovarian cancer. In this review, we bring to limelight, expansion in understanding systematical characterization of ovarian cancer cells has led to the rapid development of new drugs and treatments to target negative regulators of TRAIL mediated signaling pathway. Wide ranging synthetic and natural agents have been shown to stimulate mRNA and protein expression of death receptors. This review is compartmentalized into programmed cell death protein 4, platelet-derived growth factor signaling and miRNA control of TRAIL mediated signaling to ovarian cancer. Mapatumumab and PRO95780 have been tested for efficacy against ovarian cancer. Use of high-throughput screening assays will aid in dissecting the heterogeneity of this disease and increasing a long-term survival which might be achieved by translating rapidly accumulating information obtained from molecular and cellular studies to clinic researches.

MicroRNA in Human Glioma

Glioma represents a serious health problem worldwide. Despite advances in surgery, radiotherapy, chemotherapy, and targeting therapy, the disease remains one of the most lethal malignancies in humans, and new approaches to improvement of the efficacy of anti-glioma treatments are urgently needed. Thus, new therapeutic targets and tools should be developed based on a better understanding of the molecular pathogenesis of glioma. In this context, microRNAs (miRNAs), a class of small, non-coding RNAs, play a pivotal role in the development of the malignant phenotype of glioma cells, including cell survival, proliferation, differentiation, tumor angiogenesis, and stem cell generation. This review will discuss the biological functions of miRNAs in human glioma and their implications in improving clinical diagnosis, prediction of prognosis, and anti-glioma therapy.

Tumor-targeted Chlorotoxin-coupled Nanoparticles for Nucleic Acid Delivery to Glioblastoma Cells: A Promising System for Glioblastoma Treatment

The present work aimed at the development and application of a lipid-based nanocarrier for targeted delivery of nucleic acids to glioblastoma (GBM). For this purpose, chlorotoxin (CTX), a peptide reported to bind selectively to glioma cells while showing no affinity for non-neoplastic cells, was covalently coupled to liposomes encapsulating antisense oligonucleotides (asOs) or small interfering RNAs (siRNAs). The resulting targeted nanoparticles, designated CTX-coupled stable nucleic acid lipid particles (SNALPs), exhibited excellent features for in vivo application, namely small size (<180 nm) and neutral surface charge. Cellular association and internalization studies revealed that attachment of CTX onto the liposomal surface enhanced particle internalization into glioma cells, whereas no significant internalization was observed in noncancer cells. Moreover, nanoparticle-mediated miR-21 silencing in U87 human GBM and GL261 mouse glioma cells resulted in increased levels of the tumor suppressors PTEN and PDCD4, caspase 3/7 activation and decreased tumor cell proliferation. Preliminary in vivo studies revealed that CTX enhances particle internalization into established intracranial tumors. Overall, our results indicate that the developed targeted nanoparticles represent a valuable tool for targeted nucleic acid delivery to cancer cells. Combined with a drug-based therapy, nanoparticle-mediated miR-21 silencing constitutes a promising multimodal therapeutic approach towards GBM.

Longitudinal expression analysis of αv integrins in human gliomas reveals upregulation of integrin αvβ3 as a negative prognostic factor

Integrin inhibitors targeting αv series integrins are being tested for their therapeutic potential in patients with brain tumors, but pathologic studies have been limited by lack of antibodies suitable for immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded specimens. We compared the expression of αv integrins by IHC in brain tumor and normal human brain samples with gene expression data in a public database using new rabbit monoclonal antibodies against αvβ3, αvβ5, αvβ6, and αvβ8 complexes using both manual and automated microscopy analyses. Glial tumors usually shared an αvβ3-positive/αvβ5-positive/αvβ8-positive/αvβ6-negative phenotype. In 94 WHO (World Health Organization) grade II astrocytomas, 85 anaplastic astrocytomas WHO grade III, and 324 glioblastomas from archival sources, expression of integrins generally increased with grade of malignancy. Integrins αvβ3 and αvβ5 were expressed in many glioma vessels; the intensity of vascular expression of αvβ3 increased with grade of malignancy, whereas αvβ8 was absent. Analysis of gene expression in an independent cohort showed a similar increase in integrin expression with tumor grade, particularly of ITGB3 and ITGB8; ITGB6 was not expressed, consistent with the IHC data. Parenchymal αvβ3 expression and ITGB3 gene overexpression in glioblastomas were associated with a poor prognosis, as revealed by survival analysis (Kaplan-Meier logrank, p = 0.016). Together, these data strengthen the rationale for anti-integrin treatment of glial tumors.

Comparison of microRNA expression levels between initial and recurrent glioblastoma specimens

Glioblastoma is the most frequent primary brain tumour in adults. Recent therapeutic advances increased patient's survival, but tumour recurrence inevitably occurs. The pathobiological mechanisms involved in glioblastoma recurrence are still unclear. MicroRNAs are small RNAs proposed o have important roles for cancer including proliferation, aggressiveness and metastases development. There exist only few data on the involvement of microRNAs in glioblastoma recurrence. We selected the following 7 microRNAs with potential relevance for glioblastoma pathobiology by means of a comprehensive literature search: microRNA-10b, microRNA-21, microRNA-181b, microRNA-181c, microRNA-195, microRNA-221 and microRNA-222. We further selected 15 primary glioblastoma patients, of whom formalin fixed and paraffin embedded tissue (FFPE) of the initial and recurrence surgery were available. All patients had received first line treatment consisting of postoperative combined radiochemotherapy with temozolomide (n = 15). Non-neoplastic brain tissue samples from 3 patients with temporal lobe epilepsy served as control. The expression of the microRNAs were analysed by RT-qPCR. These were correlated with each other and with clinical parameters. All microRNAs showed detectable levels of expressions in glioblastoma group, whereas microRNA-10b was not detectable in epilepsy patients. MicroRNAs except microRNA-21 showed significantly higher levels in epilepsy patients when compared to the levels of first resection of glioblastoma. Comparison of microRNA levels between first and second resections revealed no significant change. Cox regression analyses showed no significant association of microRNA expression levels in the tumor tissue with progression free survival times. Expression levels of microRNA-10b, microRNA-21, microRNA-181b, microRNA-181c, microRNA-195, microRNA-221 and microRNA-222 do not differ significantly between initial and recurrent glioblastoma.