MicroRNA involvement in the pathogenesis of neuroblastoma: potential for microRNA mediated therapeutics

Unsaturated Fatty Acid Synthesis Is Associated with Worse Survival and Is Differentially Regulated by MYCN and Tumor Suppressor microRNAs in Neuroblastoma

MYCN amplification (MNA) and disruption of tumor suppressor microRNA (TSmiR) function are key drivers of poor outcomes in neuroblastoma (NB). While MYCN and TSmiRs regulate glucose metabolism, their role in de novo fatty acid synthesis (FAS) and unsaturated FAS (UFAS) remains poorly understood. Here, we show that FAS and UFAS (U/FAS) genes FASN, ELOVL6, SCD, FADS2, and FADS1 are upregulated in high-risk (HR) NB and that their expression is associated with lower overall survival. RNA-Seq analysis of human NB cell lines revealed parallel U/FAS gene expression patterns. Consistent with this, we found that NB-related TSmiRs were predicted to target these genes extensively. We further observed that both MYC and MYCN upregulated U/FAS pathway genes while suppressing TSmiR host gene expression, suggesting a possible U/FAS regulatory network between MYCN and TSmiRs in NB. NB cells are high in de novo synthesized omega 9 (ω9) unsaturated fatty acids and low in both ω6 and ω3, suggesting a means for NB to limit cell-autonomous immune stimulation and reactive oxygen species (ROS)-driven apoptosis from ω6 and ω3 unsaturated fatty acid derivatives, respectively. We propose a model in which MYCN and TSmiRs regulate U/FAS and play an important role in NB pathology, with implications for other MYC family-driven cancers.

TTF1 suppresses neuroblastoma growth and induces neuroblastoma differentiation by targeting TrkA and the miR-204/TrkB axis

Neuroblastoma (NB) is the most common extracranial malignant solid tumor in children. We found that TTF1, TrkA, and miR-204 were lowly expressed, whereas TrkB was highly expressed in undifferentiated NB tissues. Meanwhile, TTF1 expression correlated positively with TrkA and miR-204 expression but negatively with TrkB expression. The TTF1 promoter was hypermethylated in undifferentiated NB tissues and SK-N-BE cells, leading to TTF1 downregulation. We also identified miR-204, which directly targets TrkB, as a transcriptional target of TTF1. Functionally, TTF1 suppressed proliferation, migration, and invasion of NB cells, whereas induced cell cycle arrest, apoptosis, and autophagy of NB cells by regulating TrkA and the miR-204-TrkB axis. Furthermore, TTF1 suppressed tumor growth and promoted neurogenic differentiation in a NB xenograft mouse model. Our study demonstrates that TTF1 reduces tumor growth and induces neurogenic differentiation in NB by directly targeting TrkA and the miR-204/TrkB axis.

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TTF1, TrkA, and miR-204 were lowly expressed in undifferentiated NB tissues

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TTF1 promoter was hypermethylated in undifferentiated NB tissues and cells

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TTF1 suppressed proliferation of NB cells by regulating TrkA and the miR-204-TrkB axis

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TTF1 suppressed tumor growth and promoted neurogenic differentiation in vivo

MicroRNAs in neural crest development and neurocristopathies

The neural crest (NC) is a vertebrate-specific migratory population of multipotent stem cells that originate during late gastrulation in the region between the neural and non-neural ectoderm. This population of cells give rise to a range of derivatives, such as melanocytes, neurons, chondrocytes, chromaffin cells, and osteoblasts. Because of this, failure of NC development can cause a variety of pathologies, often syndromic, that are globally called neurocristopathies. Many genes are known to be involved in NC development, but not all of them have been identified. In recent years, attention has moved from protein-coding genes to non-coding genes, such as microRNAs (miRNA). There is increasing evidence that these non-coding RNAs are playing roles during embryogenesis by regulating the expression of protein-coding genes. In this review, we give an introduction to miRNAs in general and then focus on some miRNAs that may be involved in NC development and neurocristopathies. This new direction of research will give geneticists, clinicians, and molecular biologists more tools to help patients affected by neurocristopathies, as well as broadening our understanding of NC biology.

MicroRNA-323a-3p Negatively Regulates NEK6 in Colon Adenocarcinoma Cells

Objective. The activity of NEK6 is enhanced in several cancer cells, including colon adenocarcinoma (COAD) cells. However, there are few reports on the microRNA (miRNA/miR) regulation of NEK6. In this study, we aimed to investigate the effects of miRNAs targeting NEK6 in COAD cells. Methods. Public data and online analysis sites were used to analyze the expression levels of NEK6 and miR-323a-3p in COAD tissues as well as the relationship between NEK6 or miR-323a-3p levels and survival in patients with COAD and to predict miRNAs targeting NEK6. Real-time polymerase chain reaction and western blotting were performed to determine the levels of NEK6 and miR-323a-3p in COAD cells. The targeting of NEK6 by miR-323a-3p was verified using a dual-luciferase reporter assay. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, 5-ethynyl-2′-deoxyuridine assay, propidium iodide (PI) staining, annexin V-fluorescein isothiocyanate/PI staining, and transwell assay were employed to test the proliferation, apoptosis, migration ability, and invasiveness of COAD cells. Results. In COAD cells, NEK6 was highly expressed, whereas miR-323a-3p was expressed at low levels and negatively regulated NEK6. Upregulating the level of miR-323a-3p impaired the proliferation, migration, and invasion of COAD cells and promoted apoptosis, whereas supplementing NEK6 alleviated the damage of the proliferation, migration, and invasion of COAD cells caused by miR-323a-3p and inhibited miR-323a-3p-induced apoptosis. These findings indicate that miR-323a-3p regulates the proliferation, migration, invasion, and apoptosis of COAD cells by targeting NEK6. Conclusion. miR-323a-3p downregulates NEK6 in COAD cells; this provides a novel basis for further understanding the occurrence and development of COAD.

MYCN in Neuroblastoma: "Old Wine into New Wineskins"

MYCN Proto-Oncogene, BHLH Transcription Factor (MYCN) has been one of the most studied genes in neuroblastoma. It is known for its oncogenetic mechanisms, as well as its role in the prognosis of the disease and it is considered one of the prominent targets for neuroblastoma therapy. In the present work, we attempted to review the literature, on the relation between MYCN and neuroblastoma from all possible mechanistic sites. We have searched the literature for the role of MYCN in neuroblastoma based on the following topics: the references of MYCN in the literature, the gene's anatomy, along with its transcripts, the protein's anatomy, the epigenetic mechanisms regulating MYCN expression and function, as well as MYCN amplification. MYCN plays a significant role in neuroblastoma biology. Its functions and properties range from the forming of G-quadraplexes, to the interaction with miRNAs, as well as the regulation of gene methylation and histone acetylation and deacetylation. Although MYCN is one of the most primary genes studied in neuroblastoma, there is still a lot to be learned. Our knowledge on the exact mechanisms of MYCN amplification, etiology and potential interventions is still limited. The knowledge on the molecular mechanisms of MYCN in neuroblastoma, could have potential prognostic and therapeutic advantages.

Non-Coding RNAs Participate in the Pathogenesis of Neuroblastoma

Neuroblastoma is one of the utmost frequent neoplasms during the first year of life. This pediatric cancer is believed to be originated during the embryonic life from the neural crest cells. Previous studies have detected several types of chromosomal aberrations in this tumor. More recent studies have emphasized on expression profiling of neuroblastoma samples to identify the dysregulated genes in this type of cancer. Non-coding RNAs are among the mostly dysregulated genes in this type of cancer. Such dysregulation has been associated with a number of chromosomal aberrations that are frequently detected in neuroblastoma. In this study, we explain the role of non-coding transcripts in the malignant transformation in neuroblastoma and their role as biomarkers for this pediatric cancer.

An overview of neuroblastoma cell lineage phenotypes and in vitro models

This review was conducted to present the main neuroblastoma (NB) clinical characteristics and the most common genetic alterations present in these pediatric tumors, highlighting their impact in tumor cell aggressiveness behavior, including metastatic development and treatment resistance, and patients' prognosis. The distinct three NB cell lineage phenotypes, S-type, N-type, and I-type, which are characterized by unique cell surface markers and gene expression patterns, are also reviewed. Finally, an overview of the most used NB cell lines currently available for in vitro studies and their unique cellular and molecular characteristics, which should be taken into account for the selection of the most appropriate model for NB pre-clinical studies, is presented. These valuable models can be complemented by the generation of NB reprogrammed tumor cells or organoids, derived directly from patients' tumor specimens, in the direction toward personalized medicine.

Long non-coding RNA DLX6-AS1 regulates neuroblastoma progression by targeting YAP1 via miR-497-5p

AIMS

The lncRNA distal-less homeobox 6 antisense 1 (DLX6-AS1) has been reported to be an oncogenic lncRNA in diverse malignant cancers; however, whether it has oncogenic role in neuroblastoma(NB) remain largely unknown. This study explored the expression status, function and potential mechanism of DLX6-AS1 in NB.

MAIN METHOD

In the current study, a total of 70 human NB tissues and matched adjacent non-tumor tissues were collected. Quantitative PCR (qPCR) was performed to study the expression differences of DLX6-AS1 in tissues and NB cell lines. Proliferation, migration, invasion and EMT status of transfected NB cells were evaluated by WST-1 assay, colony formation unit assay, Transwell assay and qPCR, respectively. The interaction between DLX6-AS1 and its potential targets was confirmed by luciferase reporter assay. Xenograft models were established to evaluate tumor proliferation in vivo.

KEY FINDING

We found that the expression of DLX6-AS1 was significantly increased in both NB tissues and cell lines, and elevated DLX6AS1 expression was positively correlated with advanced stage and poor survival. Proliferation rate, migration and invasion ability, as well as EMT process of NB cells was inhibited after DLX6-AS1 knockdown, meanwhile, the tumor growth in vivo was impaired after DLX6-AS1 inhibition. Further analysis showed that DLX6-AS1 regulates the expression of YAP1 by sponging miR-497-5p. DLX6-AS1 directly interacts with miR-497-5p and reduces the binding of miR-497-5p to YAP1 3'UTR, thus inhibiting the degradation of YAP1 by miR-497-5p.

SIGNIFICANCE

This work demonstrates that DLX6-AS1 partially enhances the proliferation, migration and invasion abilities of NB cells through the miR-497-5p/YAP1 pathway, DLX6-AS1 might act as a promising therapeutic target for NB.

Up-regulation of MicroRNAs-21 and -223 in a Sprague-Dawley Rat Model of Traumatic Spinal Cord Injury

In this experimental animal study, we examined alterations in the degree of transcription of two microRNAs (miRs)—miR-21 and -223—in a Sprague-Dawley (SD) rat model of traumatic spinal cord injury (TSCI). Depending on the volume of the balloon catheter (V), a total of 75 male SD rats were divided into the three experimental groups: the sham group (n = 25; V = 0 μL), the mild group (n = 25; V = 20 μL), and the severe group (n = 25; V = 50 μL). Successful induction of TSCI was confirmed on both locomotor rating scale at 4 h and 1, 3 and 7 days post-lesion and histopathologic examinations. Then, RNA isolation and quantitative polymerase chain reaction (PCR) were performed. No differences in the level of miR-21 expression were found at the first time point studied (4 h post-lesion) between the three experimental groups, whereas such differences were significant at all the other time points (p < 0.05). Moreover, there were significant alterations in the level of miR-223 expression at all time points studied through all the experimental groups (p < 0.05). Furthermore, locomotor rating scale scores had a linear relationship with the level of miR-21 expression (R² = 0.4363, Y = 1.661X + 3.096) and that of miR-223 one (R² = 0.9104, Y = 0.8385X + 2.328). Taken together, we conclude that up-regulation of miR-21 and -223 might be closely associated with progression and the early course of TSCI, respectively.

MicroRNAs in neuroblastoma tumorigenesis, therapy resistance, and disease evolution

Neuroblastoma (NB) deriving from neural crest cells is the most common extra-cranial solid cancer at infancy. NB originates within the peripheral sympathetic ganglia in adrenal medulla and along the midline of the body. Clinically, NB exhibits significant heterogeneity stretching from spontaneous regression to rapid progression to therapy resistance. MicroRNAs (miRNAs, miRs) are small (19-22 nt in length) non-coding RNAs that regulate human gene expression at the post-transcriptional level and are known to regulate cellular signaling, growth, differentiation, death, stemness, and maintenance. Consequently, the function of miRs in tumorigenesis, progression and resistance is of utmost importance for the understanding of dysfunctional cellular pathways that lead to disease evolution, therapy resistance, and poor clinical outcomes. Over the last two decades, much attention has been devoted to understanding the functional roles of miRs in NB biology. This review focuses on highlighting the important implications of miRs within the context of NB disease progression, particularly miRs’ influences on NB disease evolution and therapy resistance. In this review, we discuss the functions of both the “oncomiRs” and “tumor suppressor miRs” in NB progression/therapy resistance. These are the critical components to be considered during the development of novel miR-based therapeutic strategies to counter therapy resistance.

Long noncoding RNA DLX6-AS1 promotes neuroblastoma progression by regulating miR-107/BDNF pathway

Background

Long noncoding RNAs (lncRNAs) play essential roles in tumor progression. However, the functions and targets of lncRNAs in neuroblastoma (NB) progression still remain to be determined. In this study, we aimed to investigate the effect of lncRNA DLX6 antisense RNA 1 (DLX6-AS1) on NB and the underlying mechanism involved.

Methods

Through mining of public microarray datasets, we identify aberrantly expressed lncRNAs in NB. The gene expression levels were determined by quantitative real-time PCR, and protein expression levels were determined by western blot assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, colony formation assay, wound-healing assay, transwell invasion assays and flow cytometry analysis were utilized to examine cell proliferation, migration, invasion and apoptosis. Luciferase reporter assay was performed to confirm the interaction between DLX6-AS1and its potential targets. Tumor xenograft assay was used to verify the role of DLX6-AS1 in NB in vivo.

Results

We identified DLX6-AS1 was upregulated in NB by using a public microarray dataset. The expression of DLX6-AS1 was increased in NB tissues and derived cell lines, and high expression of DLX6-AS1 was positively correlated with advanced TNM stage and poor differentiation. Knockdown of DLX6-AS1 induced neuronal differentiation, apoptosis and inhibited the growth, invasion, and metastasis of NB cells in vitro and impaired tumor growth in vivo. MiR-107 was the downstream target of DLX6-AS1. MiR-107 was found to target brain‐derived neurotrophic factor (BDNF) which is an oncogene in NB. Knockdown of miR-107 or overexpression of BDNF reversed the suppression of NB progression caused by DLX6-AS1 silence.

Conclusion

Overall, our finding supports that DLX6-AS1 promotes NB progression by regulating miR-107/BDNF pathway, acting as a novel therapeutic target for NB.

Nanotechnological based miRNA intervention in the therapeutic management of neuroblastoma

Neuroblastoma (NB) is a widely diagnosed cancer in children, characterized by amplification of the gene encoding the MYCN transcription factor, which is highly predictive of poor clinical outcome and metastatic disease. microRNAs (a class of small non-coding RNAs) are regulated by MYCN transcription factor in neuroblastoma cells. The current research is focussed on identifying differential role of miRNAs and their interactions with signalling proteins, which are intricately linked with cellular processes like apoptosis, proliferation or metastasis. However, the therapeutic success of miRNAs is limited by pharmaco-technical issues which are well counteracted by nanotechnological advancements. The nanoformulated miRNAs unload anti-cancer drugs in a controlled and prespecified manner at target sites, to influence the activity of target protein in amelioration of NB. Recent advances and developments in the field of miRNAs-based systems for clinical management of NBs and the role of nanotechnology to overcome challenges with drug delivery of miRNAs have been reviewed in this paper.

Functional high-throughput screening reveals miR-323a-5p and miR-342-5p as new tumor-suppressive microRNA for neuroblastoma

Current therapies for most non-infectious diseases are directed at or affect functionality of the human translated genome, barely 2% of all genetic information. By contrast, the therapeutic potential of targeting the transcriptome, ~ 70% of the genome, remains largely unexplored. RNA therapeutics is an emerging field that widens the range of druggable targets and includes elements such as microRNA. Here, we sought to screen for microRNA with tumor-suppressive functions in neuroblastoma, an aggressive pediatric tumor of the sympathetic nervous system that requires the development of new therapies. We found miR-323a-5p and miR-342-5p to be capable of reducing cell proliferation in multiple neuroblastoma cell lines in vitro and in vivo, thereby providing a proof of concept for miRNA-based therapies for neuroblastoma. Furthermore, the combined inhibition of the direct identified targets such as CCND1, CHAF1A, INCENP and BCL-XL could reveal new vulnerabilities of high-risk neuroblastoma.

Non-Coding RNA Networks in ALK-Positive Anaplastic-Large Cell Lymphoma

Non-coding RNAs (ncRNAs) are essential regulators of gene expression. In recent years, it has become more and more evident that the different classes of ncRNAs, such as micro RNAs, long non-coding RNAs and circular RNAs are organized in tightly controlled networks. It has been suggested that deregulation of these networks can lead to disease. Several studies show a contribution of these so-called competing-endogenous RNA networks in various cancer entities. In this review, we highlight the involvement of ncRNA networks in anaplastic-large cell lymphoma (ALCL), a T-cell neoplasia. A majority of ALCL cases harbor the molecular hallmark of this disease, a fusion of the anaplastic lymphoma kinase (ALK) gene with the nucleophosmin (NPM, NPM1) gene leading to a permanently active kinase that promotes the malignant phenotype. We have focused especially on ncRNAs that are regulated by the NPM-ALK fusion gene and illustrate how their deregulation contributes to the pathogenesis of ALCL. Lastly, we summarize the findings and point out potential therapeutic implications.

miR-34a inhibits progression of neuroblastoma by targeting autophagy-related gene 5

Neuroblastoma (NB) is a common pediatric malignancy with high mortality in childhood. Although many attentions have been gained, novel biomarkers for NB diagnosis and prognosis are still needed. microRNAs (miRNAs) played important roles in NB progression and miR-34a is a tumor suppressor in NB. However, the mechanism that underlies miR-34a regulating proliferation, migration, invasion and autophagy in NB remains poorly understood. In this study, cell proliferation was investigated by MTT and colony assay. Cell apoptosis was measured by caspase 3 activity assay. Cell migration and invasion were detected by trans-well analysis. Autophagy was measured via GFP-LC3 puncta fluorescence assay and western blots (WB). The expression of miR-34a was examined by quantitative real-time PCR (qRT-PCR). The regulatory effect of miR-34a on autophagy-related gene 5 (ATG5) was detected by qRT-PCR and WB. The interaction between miR-34a and ATG5 was probed by luciferase activity and RNA immunoprecipitation (RIP) assay. Results showed that miR-34a expression was inhibited in NB tissues and cells with low survival rate. Addition of miR-34a suppressed cell proliferation, migration, invasion and autophagy but promoted apoptosis in NB cells, whereas miR-34a deficiency played opposite roles in NB progression. Intriguingly, ATG5 was directly targeted by miR-34a. Moreover, ATG5 restoration attenuated miR-34a-mediated inhibitory effect on proliferation, apoptosis, migration, invasion and autophagy. These results indicated miR-34a suppressed proliferation, apoptosis, migration, invasion and autophagy in NB cells by targeting ATG5, providing a novel therapeutic avenue for NB treatment.

Exogenous expression of miRNA-3613-3p causes APAF1 downregulation and affects several proteins involved in apoptosis in BE(2)-C human neuroblastoma cells

MicroRNAs (miRNAs) are a class of small non‑coding RNAs involved in post‑transcriptional gene regulation. Furthermore, dysregulation of miRNA expression is an important factor in the pathogenesis of neuroblastoma. Our previous study identified that overexpression of monocyte chemoattractant protein‑induced protein 1 protein led to a significant downregulation of a novel miRNA molecule, miRNA‑3613‑3p. In the present study, the potential involvement of miRNA‑3613‑3p in the cell biology of neuroblastoma was investigated. It was identified that the expression of miRNA‑3613‑3p varies among a range of human neuroblastoma cell lines. As the delineation of the functions of a miRNA requires the identification of its target genes, seven putative mRNAs that may be regulated by miRNA‑3613‑3p were selected. Furthermore, it was identified that overexpression of miRNA‑3613‑3p causes significant downregulation of several genes exhibiting tumor suppressive potential [encoding apoptotic protease‑activating factor 1 (APAF1), Dicer, DNA fragmentation factor subunit β, von Hippel‑Lindau protein and neurofibromin 1] in BE(2)‑C human neuroblastoma cells. APAF1 mRNA was the most significantly decreased transcript in the cells with miRNA‑3613‑3p overexpression. In accordance with the aforementioned results, the downregulation of cleaved caspase-9 and lack of activation of executive caspases in BE(2)‑C cells following miRNA‑3613‑3p overexpression was observed. The results of the present study suggest a potential underlying molecular mechanism of apoptosis inhibition via APAF1 downregulation in human neuroblastoma BE(2)‑C cells with miRNA‑3613‑3p overexpression.

miRNA expression profile of bone marrow resident cells from children with neuroblastoma is not significantly different from that of healthy children

The miRNA expression profiles of bone marrow resident cells from children with neuroblastoma were compared to that of healthy children. No significant difference was found between localized and metastatic neuroblastoma, or between children with neuroblastoma and healthy children. By considering the fold change we identified six miRNAs over-expressed by more than 150 fold in neuroblastoma. Validation confirmed miR-221 over-expression in BM resident cells from children with neuroblastoma, regardless of localized or metastatic disease. MiR-221 over-expression was unlikely derived from neuroblastoma primary tumors or from bone marrow-infiltrating metastatic cells, since neuroblastoma cells expressed lower or similar amount of miR-221 than BM cells, respectively. To get insight on the genes potentially regulated by miR-221 we merged the list of miR-221 potential targets with the genes under-expressed by BM resident cells from children with neuroblastoma, as compared with healthy children. In silico analysis demonstrated that none of the miR-221 target genes belonged to heme biosynthetic processes found altered in children with neuroblastoma, whereas two genes associated with mitochondria. However, the encoded proteins were not under-expressed in children with neuroblastoma, making unlikely that altered erythrocyte maturation in children with neuroblastoma was mediated by miR-221. In conclusion, miRNA expression profiles of BM resident cells from children with localized and metastatic neuroblastoma were similar to that of BM resident cells from healthy children. Moreover, miRNAs expressed by neuroblastoma primary tumors or by BM-infiltrating NB cells do not appear to be involved in mediating the functional defect of erythrocyte maturation recently observed in children with neuroblastoma.

Altered expression of miRNAs and methylation of their promoters are correlated in neuroblastoma

Neuroblastoma is the most common human extracranial solid tumor during infancy. Involvement of several miRNAs in its pathogenesis has been ascertained. Interestingly, most of their encoding genes reside in hypermethylated genomic regions: thus, their tumor suppressor function is normally disallowed in these tumors. To date, the therapeutic role of the demethylating agent 5′-Aza-2 deoxycytidine (5'-AZA) and its effects on miRNAome modulation in neuroblastoma have not been satisfactorily explored. Starting from a high-throughput expression profiling of 754 miRNAs and based on a proper selection, we focused on miR-29a-3p, miR-34b-3p, miR-181c-5p and miR-517a-3p as candidate miRNAs for our analysis. They resulted downregulated in four neuroblastoma cell lines with respect to normal adrenal gland. MiRNAs 29a-3p and 34b-3p also resulted downregulated in vivo in a murine neuroblastoma progression model. Unlike the amount of methylation of their encoding gene promoters, all these miRNAs were significantly overexpressed following treatment with 5′-AZA. Transfection with candidate miRNAs mimics significantly decreased neuroblastoma cells proliferation rate. A lower expression of miR-181c was significantly associated to a worse overall survival in a public dataset of 498 neuroblastoma samples (http://r2.amc.nl). Our data strongly suggest that CDK6, DNMT3A, DNMT3B are targets of miR-29a-3p, while CCNE2 and E2F3 are targets of miR-34b-3p. Based on all these data, we propose that miR-29a-3p, miR-34b-3p, miR-181c-5p and miR-517a-3p are disallowed tumor suppressor genes in neuroblastoma and suggest them as new therapeutic targets in neuroblastoma.

microRNA-558 facilitates the expression of hypoxia-inducible factor 2 alpha through binding to 5'-untranslated region in neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood. Our previous studies have shown that hypoxia-inducible factor 2 alpha (HIF-2α), one member of the bHLH-PAS transcription factor family, facilitates the progression of NB under non-hypoxic conditions. However, the mechanisms underlying HIF-2α expression in NB still remain largely unknown. Herein, through analyzing the computational algorithm programs, we identified microRNA-558 (miR-558) as a crucial regulator of HIF-2α expression in NB. We demonstrated that miR-558 promoted the expression of HIF-2α at translational levels in NB cells through recruiting Argonaute 2 (AGO2). Mechanistically, miR-558 directly bound with its complementary site within 5′-untranslated region (5′-UTR) to facilitate the binding of AGO2 to eukaryotic translation initiation factor 4E (eIF4E) binding protein 1, resulting in increased eIF4E enrichment and HIF-2α translation. In addition, miR-558 promoted the growth, invasion, metastasis, and angiogenesis of NB cells in vitro and in vivo, and these biological features were rescued by knockdown of AGO2, eIF4E, or HIF-2α. In clinical NB specimens, miR-558, AGO2, and eIF4E were highly expressed and positively correlated with HIF-2α expression. Patients with high miR-558, HIF-2α, AGO2, or eIF4E levels had lower survival probability. Taken together, these results demonstrate that miR-558 facilitates the expression of HIF-2α through bindingto its 5′-UTR, thus promoting the tumorigenesis and aggressiveness of NB.

MiRNA Influences in Neuroblast Modulation: An Introspective Analysis

Neuroblastoma (NB) is the most common occurring solid paediatric cancer in children under the age of five years. Whether of familial or sporadic origin, chromosome abnormalities contribute to the development of NB and cause dysregulation of microRNAs (miRNAs). MiRNAs are small non-coding, single stranded RNAs that target messenger RNAs at the post-transcriptional levels by repressing translation within all facets of human physiology. Such gene 'silencing' activities by miRNAs allows the development of regulatory feedback loops affecting multiple functions within the cell, including the possible differentiation of neural stem cell (NSC) lineage selection. Neurogenesis includes stages of self-renewal and fate specification of NSCs, migration and maturation of young neurones, and functional integration of new neurones into the neural circuitry, all of which are regulated by miRNAs. The role of miRNAs and their interaction in cellular processes are recognised aspects of cancer genetics, and miRNAs are currently employed as biomarkers for prognosis and tumour characterisation in multiple cancer models. Consequently, thorough understanding of the mechanisms of how these miRNAs interplay at the transcriptomic level will definitely lead to the development of novel, bespoke and efficient therapeutic measures, with this review focusing on the influences of miRNAs on neuroblast modulations leading to neuroblastoma.

miR-205 Inhibits Neuroblastoma Growth by Targeting cAMP-Responsive Element-Binding Protein 1

Accumulating evidence indicates that microRNA-205 (miR-205) is involved in tumor initiation, development, and metastasis in various cancers. However, its functions in neuroblastoma (NB) remain largely unclear. Here we found that miR-205 was significantly downregulated in human NB tissue samples and cell lines. miR-205 expression was lower in poorly differentiated NB tissues and those of advanced International Neuroblastoma Staging System stage. In addition, restoration of miR-205 in NB cells suppressed proliferation, migration, and invasion and induced cell apoptosis in vitro, as well as impaired tumor growth in vivo. cAMP-responsive element-binding protein 1 (CREB1) was identified as a direct target gene of miR-205. Expression of an miR-205 mimic in NB cells significantly diminished expression of CREB1 and the CREB1 targets BCL-2 and MMP9. CREB1 was also found to be upregulated in human NB tissues, its expression being inversely correlated with miR-205 expression (r = −0.554, p = 0.003). Importantly, CREB1 upregulation partially rescued the inhibitory effects of miR-205 on NB cells. These findings suggest that miR-205 may function as a tumor suppressor in NB by targeting CREB1.

Influence of microRNAs and Long Non-Coding RNAs in Cancer Chemoresistance

Innate and acquired chemoresistance exhibited by most tumours exposed to conventional chemotherapeutic agents account for the majority of relapse cases in cancer patients. Such chemoresistance phenotypes are of a multi-factorial nature from multiple key molecular players. The discovery of the RNA interference pathway in 1998 and the widespread gene regulatory influences exerted by microRNAs (miRNAs) and other non-coding RNAs have certainly expanded the level of intricacy present for the development of any single physiological phenotype, including cancer chemoresistance. This review article focuses on the latest research efforts in identifying and validating specific key molecular players from the two main families of non-coding RNAs, namely miRNAs and long non-coding RNAs (lncRNAs), having direct or indirect influences in the development of cancer drug resistance properties and how such knowledge can be utilised for novel theranostics in oncology.

MicroRNA expression patterns and signalling pathways in the development and progression of childhood solid tumours

The development of childhood solid tumours is tied to early developmental processes. These tumours may be complex and heterogeneous, and elucidating the aberrant mechanisms that alter the early embryonic environment and lead to disease is essential to our understanding of how these tumours function. MicroRNAs (miRNAs) are vital regulators of gene expression at all stages of development, and their crosstalk via developmental signalling pathways is essential for orchestrating regulatory control in processes such as proliferation, differentiation and apoptosis of cells. Oncogenesis, from aberrant miRNA expression, can occur through amplification and overexpression of oncogenic miRNAs (oncomiRs), genetic loss of tumour suppressor miRNAs, and global miRNA reduction from genetic and epigenetic alterations in the components regulating miRNA biogenesis. While few driver mutations have been identified in many of these types of tumours, abnormal miRNA expression has been found in a number of childhood solid tumours compared to normal tissue. An exploration of the network of key developmental pathways and interacting miRNAs may provide insight into the development of childhood solid malignancies and how key regulators are affected. Here we present a comprehensive introduction to the roles and implications of miRNAs in normal early development and childhood solid tumours, highlighting several tumours in depth, including embryonal brain tumours, neuroblastoma, osteosarcoma, Wilms tumour, and hepatoblastoma. In light of recent literature describing newer classifications and subtyping of tumours based on miRNA profiling, we discuss commonly identified miRNAs, clusters or families associated with several solid tumours and future directions for improving therapeutic approaches.

miR-506 suppresses neuroblastoma metastasis by targeting ROCK1

Neuroblastoma is a complex form of cancer with highly heterogeneous clinical behavior that arises during childhood from precursor cells of the sympathetic nervous system. In patients with neuroblastoma, mortality often occurs as a result of metastasis. The disease predominantly spreads to bone marrow, with a survival rate of ~40%. The current study demonstrates that microRNA (miR)-506 directly targets and downregulates Rho-associated, coiled-coil containing protein kinase 1 (ROCK1) in transforming growth factor (TGF)-β non-canonical pathways. It may be concluded that ROCK1 contributes to the invasion and migration of neuroblastoma cells by directly downregulating miR-506; thus, leading to the upregulation of ROCK1, which promotes cell invasion and migration. The present results provide a novel understanding of how miR-506 directly regulates TGF-β non-canonical signaling.

Neuroblastoma (Peripheral neuroblastic tumours)

Peripheral neuroblastic tumours (PNTs), a family of tumours arising in the embryonal remnants of the sympathetic nervous system, account for 7-10% of all tumours in children. In two-thirds of cases, PNTs originate in the adrenal glands or the retroperitoneal ganglia. At least one third present metastases at onset, with bone and bone marrow being the most frequent metastatic sites. Disease extension, MYCN oncogene status and age are the most relevant prognostic factors, and their influence on outcome have been considered in the design of the recent treatment protocols. Consequently, the probability of cure has increased significantly in the last two decades. In children with localised operable disease, surgical resection alone is usually a sufficient treatment, with 3-year event-free survival (EFS) being greater than 85%. For locally advanced disease, primary chemotherapy followed by surgery and/or radiotherapy yields an EFS of around 75%. The greatest problem is posed by children with metastatic disease or amplified MYCN gene, who continue to do badly despite intensive treatments. Ongoing trials are exploring the efficacy of new drugs and novel immunological approaches in order to save a greater number of these patients.

Down-regulation of the Lamin A/C in neuroblastoma triggers the expansion of tumor initiating cells

Tumor-initiating cells constitute a population within a tumor mass that shares properties with normal stem cells and is considered responsible for therapy failure in many cancers. We have previously demonstrated that knockdown of the nuclear envelope component Lamin A/C in human neuroblastoma cells inhibits retinoic acid-mediated differentiation and results in a more aggressive phenotype. In addition, Lamin A/C is often lost in advanced tumors and changes in the nuclear envelope composition occur during tumor progression. Based on our previous data and considering that Lamin A/C is expressed in differentiated tissues, we hypothesize that the lack of Lamin A/C could predispose cells toward a stem-like phenotype, thus influencing the development of tumor-initiating cells in neuroblastoma. This paper demonstrates that knockdown of Lamin A/C triggers the development of a tumor-initiating cell population with self-renewing features in human neuroblastoma cells. We also demonstrates that the development of TICs is due to an increased expression of MYCN gene and that in neuroblastoma exists an inverse relationship between LMNA and MYCN expression.

MiR-204 inhibits the proliferation and invasion of renal cell carcinoma by inhibiting RAB22A expression

While miR-204 expression may be linked to renal cell carcinoma (RCC) progression, the detailed mechanisms remain unclear. In the present study, we demonstrated that miR-204 was differentially expressed in RCC tissues when compared with surrounding normal kidney tissues. Ectopic overexpression of miR-204 in human RCC cells suppressed cell proliferation and invasion in vitro and in vivo. Mechanism dissection revealed that miR-204 may function through RAB22A signals to inhibit RCC proliferation and invasion. Overexpression of RAB22A by oe-RAB22A was able to partially reverse the miR-204-mediated suppression of RCC tumor progression. Together, these results revealed that miR-204 suppressed RCC proliferation and invasion by directly targeting the RAB22A gene. Targeting newly identified RAB22A with miR-204 may aid in the suppression of RCC proliferation and invasion.

The tumor-suppressive and potential therapeutic functions of miR-34a in epithelial carcinomas

INTRODUCTION

Many RNA species have been identified as important players in the development of chronic diseases including cancer. Certain classes of regulatory RNAs such as microRNAs (miRNAs) have been investigated in such detail that bona fide tumor suppressive and oncogenic miRNAs have been identified. Because of this, there has been a major effort to therapeutically target these small RNAs. One in particular, a liposomal formulation of miR-34a (MRX34), has entered Phase I trials.

AREAS COVERED

This review aims to summarize miRNA biology, its regulation within normal versus disease states and how it can be targeted therapeutically, with a particular emphasis on miR-34a. Understanding the complexity of a single miRNA will aid in the development of future RNA-based therapeutics for a broader range of chronic diseases.

EXPERT OPINION

The potential of miRNAs to be developed into anti-cancer therapeutics has become an increasingly important area of research. miR-34a is a tumor suppressive miRNA across many tumor types through its ability to inhibit cellular proliferation, invasion and tumor sphere formation. miR-34a also shows promise within certain in vivo solid tumor models. Finally, as miR-34a moves into clinical trials it will be important to determine if it can further sensitize tumors to certain chemotherapeutic agents.

Chemoresistance, cancer stem cells, and miRNA influences: the case for neuroblastoma

Neuroblastoma is a type of cancer that develops most often in infants and children under the age of five years. Neuroblastoma originates within the peripheral sympathetic ganglia, with 30% of the cases developing within the adrenal medulla, although it can also occur within other regions of the body such as nerve tissue in the spinal cord, neck, chest, abdomen, and pelvis. MicroRNAs (miRNAs) regulate cellular pathways, differentiation, apoptosis, and stem cell maintenance. Such miRNAs regulate genes involved in cellular processes. Consequently, they are implicated in the regulation of a spectrum of signaling pathways within the cell. In essence, the role of miRNAs in the development of cancer is of utmost importance for the understanding of dysfunctional cellular pathways that lead to the conversion of normal cells into cancer cells. This review focuses on highlighting the recent, important implications of miRNAs within the context of neuroblastoma basic research efforts, particularly concerning miRNA influences on cancer stem cell pathology and chemoresistance pathology for this condition, together with development of translational medicine approaches for novel diagnostic tools and therapies for this neuroblastoma.

miRNA-584-5p exerts tumor suppressive functions in human neuroblastoma through repressing transcription of matrix metalloproteinase 14

Matrix metalloproteinase 14 (MMP-14) is a membrane-anchored MMP crucial for tumorigenesis and aggressiveness, and is highly expressed in neuroblastoma (NB), the most common extracranial solid tumor in childhood. Recent evidence shows the emerging roles of endogenous promoter-targeting microRNAs (miRNAs) in regulating gene transcription. However, the roles of miRNAs in the transcription of MMP-14 still remain largely unknown. In this study, through mining computational algorithm program and Argonaute-chromosome interaction dataset, we identified one binding site of miRNA-584-5p (miR-584-5p) within the MMP-14 promoter. In NB tissues, miR-584-5p was under-expressed and inversely correlated with MMP-14 expression, and was an independent prognostic factor for favorable outcome of patients. miR-584-5p precursor attenuated the expression of MMP-14 in a Dicer-dependent manner, resulting in decreased levels of vascular endothelial growth factor, in cultured NB cell lines. In addition, miR-584-5p suppressed the promoter activity of MMP-14, and mutation of miR-584-5p binding site abolished these effects. Mechanistically, miR-584-5p recruited Argonaute 2 to facilitate the enrichment of enhancer of zeste homolog 2, histone H3 lysine 27 trimethylation, and histone H3 lysine 9 dimethylation on MMP-14 promoter in NB cells, which was abolished by repressing the miR-584-5p-promoter interaction. Gain- and loss-of-function studies demonstrated that miR-584-5p suppressed the growth, invasion, metastasis, and angiogenesis of NB cells in vitro and in vivo. Moreover, restoration of MMP-14 expression rescued the NB cells from changes in these biological features. Taken together, these results indicate that promoter-targeting miR-584-5p exerts tumor suppressive functions in NB through repressing the transcription of MMP-14.

MicroRNA and pediatric tumors: Future perspectives

A better understanding of pediatric tumor biology is needed to allow the development of less toxic and more efficient therapies, as well as to provide novel reliable biomarkers for diagnosis and risk stratification. The emerging role of microRNAs in controlling key pathways implicated in tumorigenesis makes their use in diagnostics a powerful novel tool for the early detection, risk assessment and prognosis, as well as for the development of innovative anticancer therapies. This perspective would be more urgent for the clinical management of pediatric cancer. In this review, we focus on the involvement of microRNAs in the biology of the main childhood tumors, describe their clinical significance and discuss their potential use as novel therapeutic tools and targets.

Identification of miRNAs contributing to neuroblastoma chemoresistance

BACKGROUND

The emergence of the role of microRNAs (miRNAs) in exacerbating drug resistance of tumours is recently being highlighted as a crucial research field for future clinical management of drug resistant tumours. The purpose of this study was to identify dys-regulations in expression of individual and/or networks of miRNAs that may have direct effect on neuroblastoma (NB) drug resistance.

METHODS

Individual subcultures of chemosensitive SH-SY5Y and UKF-NB-3 cells were rendered chemoresistant to doxorubicin (SH-SY5Y, UKF-NB-3) or etoposide (SH-SY5Y). In each validated chemoresistance model, the parental and subcultured cell lines were analysed for miRNA expression profiling, using a high-throughput quantitative polymerase chain reaction (RT-qPCR) miRNA profiling platform for a total of 668 miRNAs.

RESULTS

A unique expression signature of miRNAs was found to be differentially expressed (higher than 2-fold change) within all three NB chemoresistance models. Four miRNAs were upregulated in the subcultured chemoresistant cell line. Three miRNAs were found to be downregulated in the chemoresistant cell lines for all models.

CONCLUSIONS

Based on the initial miRNA findings, this study elucidates the dys-regulation of four miRNAs in three separate NB chemoresistant cell line models, spanning two cell lines (SH-SY5Y and UKF-NB-3) and two chemotherapeutic agents (doxorubicin and etoposide). These miRNAs may thus be possibly linked to chemoresistance induction in NB. Such miRNAs are good candidates to be novel drug targets for future miRNA based therapies against aggressive tumours that are not responding to conventional chemotherapy.

Retinoic acid signaling and neuronal differentiation

The identification of neurological symptoms caused by vitamin A deficiency pointed to a critical, early developmental role of vitamin A and its metabolite, retinoic acid (RA). The ability of RA to induce post-mitotic, neural phenotypes in various stem cells, in vitro, served as early evidence that RA is involved in the switch between proliferation and differentiation. In vivo studies have expanded this "opposing signal" model, and the number of primary neurons an embryo develops is now known to depend critically on the levels and spatial distribution of RA. The proneural and neurogenic transcription factors that control the exit of neural progenitors from the cell cycle and allow primary neurons to develop are partly elucidated, but the downstream effectors of RA receptor (RAR) signaling (many of which are putative cell cycle regulators) remain largely unidentified. The molecular mechanisms underlying RA-induced primary neurogenesis in anamniote embryos are starting to be revealed; however, these data have been not been extended to amniote embryos. There is growing evidence that bona fide RARs are found in some mollusks and other invertebrates, but little is known about their necessity or functions in neurogenesis. One normal function of RA is to regulate the cell cycle to halt proliferation, and loss of RA signaling is associated with dedifferentiation and the development of cancer. Identifying the genes and pathways that mediate cell cycle exit downstream of RA will be critical for our understanding of how to target tumor differentiation. Overall, elucidating the molecular details of RAR-regulated neurogenesis will be decisive for developing and understanding neural proliferation-differentiation switches throughout development.

Neuroblastoma: molecular pathogenesis and therapy

Neuroblastoma is a developmental tumor of young children arising from the embryonic sympathoadrenal lineage of the neural crest. Neuroblastoma is the primary cause of death from pediatric cancer for children between the ages of one and five years and accounts for ∼13% of all pediatric cancer mortality. Its clinical impact and unique biology have made this aggressive malignancy the focus of a large concerted translational research effort. New insights into tumor biology are driving the development of new classification schemas. Novel targeted therapeutic approaches include small-molecule inhibitors as well as epigenetic, noncoding-RNA, and cell-based immunologic therapies. In this review, recent insights regarding the pathogenesis and biology of neuroblastoma are placed in context with the current understanding of tumor biology and tumor/host interactions. Systematic classification of patients coupled with therapeutic advances point to a future of improved clinical outcomes for this biologically distinct and highly aggressive pediatric malignancy.

Significance and therapeutic value of miRNAs in embryonal neural tumors

Embryonal tumors of the nervous system are the leading cause of childhood cancer-related morbidity and mortality. Medulloblastoma, supratentorial primitive neuroectodermal tumors, atypical teratoid/rhabdoid tumor and neuroblastoma account for more than 20% of childhood malignancies and typify the current neural embryonal tumor model in pediatric oncology. Mechanisms driving the formation of these tumors point towards impaired differentiation of neuronal and neuron-associated cells during the development of the nervous system as an important factor. The importance of microRNAs (miRNAs) for proper embryonic cell function has been confirmed and their aberrant expressions have been linked to tumor development. The role of miRNAs in controlling essential regulators of key pathways implicated in tumor development makes their use in diagnostics a powerful tool to be used for early detection of cancer, risk assessment and prognosis, as well as for the design of innovative therapeutic strategies. In this review we focus on the significance of miRNAs involved in the biology of embryonal neural tumors, delineate their clinical significance and discuss their potential as a novel therapeutic target.

MicroRNAs define distinct human neuroblastoma cell phenotypes and regulate their differentiation and tumorigenicity

Background

Neuroblastoma (NB) is the most common extracranial solid tumor in children. NB tumors and derived cell lines are phenotypically heterogeneous. Cell lines are classified by phenotype, each having distinct differentiation and tumorigenic properties. The neuroblastic phenotype is tumorigenic, has neuronal features and includes stem cells (I-cells) and neuronal cells (N-cells). The non-neuronal phenotype (S-cell) comprises cells that are non-tumorigenic with features of glial/smooth muscle precursor cells. This study identified miRNAs associated with each distinct cell phenotypes and investigated their role in regulating associated differentiation and tumorigenic properties.

Methods

A miRNA microarray was performed on the three cell phenotypes and expression verified by qRT-PCR. miRNAs specific for certain cell phenotypes were modulated using miRNA inhibitors or stable transfection. Neuronal differentiation was induced by RA; non-neuronal differentiation by BrdU. Changes in tumorigenicity were assayed by soft agar colony forming ability. N-myc binding to miR-375 promoter was assayed by chromatin-immunoprecipitation.

Results

Unsupervised hierarchical clustering of miRNA microarray data segregated neuroblastic and non-neuronal cell lines and showed that specific miRNAs define each phenotype. qRT-PCR validation confirmed that increased levels of miR-21, miR-221 and miR-335 are associated with the non-neuronal phenotype, whereas increased levels of miR-124 and miR-375 are exclusive to neuroblastic cells. Downregulation of miR-335 in non-neuronal cells modulates expression levels of HAND1 and JAG1, known modulators of neuronal differentiation. Overexpression of miR-124 in stem cells induces terminal neuronal differentiation with reduced malignancy. Expression of miR-375 is exclusive for N-myc-expressing neuroblastic cells and is regulated by N-myc. Moreover, miR-375 downregulates expression of the neuronal-specific RNA binding protein HuD.

Conclusions

Thus, miRNAs define distinct NB cell phenotypes. Increased levels of miR-21, miR-221 and miR-335 characterize the non-neuronal, non-malignant phenotype and miR-335 maintains the non-neuronal features possibly by blocking neuronal differentiation. miR-124 induces terminal neuronal differentiation with reduction in malignancy. Data suggest N-myc inhibits neuronal differentiation of neuroblastic cells possibly by upregulating miR-375 which, in turn, suppresses HuD. As tumor differentiation state is highly predictive of patient survival, the involvement of these miRNAs with NB differentiation and tumorigenic state could be exploited in the development of novel therapeutic strategies for this enigmatic childhood cancer.

MYCN gene expression is required for the onset of the differentiation programme in neuroblastoma cells

Neuroblastoma is an embryonic tumour of the sympathetic nervous system and is one of the most common cancers in childhood. A high differentiation stage has been associated with a favourable outcome; however, the mechanisms governing neuroblastoma cell differentiation are not completely understood. The MYCN gene is considered the hallmark of neuroblastoma. Even though it has been reported that MYCN has a role during embryonic development, it is needed its decrease so that differentiation can be completed. We aimed to better define the role of MYCN in the differentiation processes, particularly during the early stages. Considering the ability of MYCN to regulate non-coding RNAs, our hypothesis was that N-Myc protein might be necessary to activate differentiation (mimicking embryonic development events) by regulating miRNAs critical for this process. We show that MYCN expression increased in embryonic cortical neural precursor cells at an early stage after differentiation induction. To investigate our hypothesis, we used human neuroblastoma cell lines. In LAN-5 neuroblastoma cells, MYCN was upregulated after 2 days of differentiation induction before its expected downregulation. Positive modulation of various differentiation markers was associated with the increased MYCN expression. Similarly, MYCN silencing inhibited such differentiation, leading to negative modulation of various differentiation markers. Furthermore, MYCN gene overexpression in the poorly differentiating neuroblastoma cell line SK-N-AS restored the ability of such cells to differentiate. We identified three key miRNAs, which could regulate the onset of differentiation programme in the neuroblastoma cells in which we modulated MYCN. Interestingly, these effects were accompanied by changes in the apoptotic compartment evaluated both as expression of apoptosis-related genes and as fraction of apoptotic cells. Therefore, our idea is that MYCN is necessary during the activation of neuroblastoma differentiation to induce apoptosis in cells that are not committed to differentiate.

The roles of microRNAs in neuroblastoma

BACKGROUND

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood and displays remarkable heterogeneity in clinical behaviors, ranging from spontaneous regression to rapid progression or resistance to multimodal treatment. Recent evidence has shown that microRNAs (miRNAs), a class of small non-coding RNAs, are involved in tumor development and progression. This article aimed to review recent advances in investigating the roles of miRNAs in NB.

METHODS

We searched the PubMed/MEDLINE database for articles about the expression profile, functions and target genes of miRNAs in NB.

RESULTS

We reviewed the most recent evidence regarding the functional roles of oncogenic and tumor suppressive miRNAs in NB and application of novel miRNA-based methods for diagnostic, prognostic and therapeutic purposes.

CONCLUSIONS

Deregulation of miRNAs is associated with the development and progression of NB, suggesting that miRNAs may serve as novel targets for the treatment of high-risk NB patients. However, their precise functions and underlying mechanisms still warrant further studies.

miR-92a family and their target genes in tumorigenesis and metastasis

The miR-92a family, including miR-25, miR-92a-1, miR-92a-2 and miR-363, arises from three different paralog clusters miR-17-92, miR-106a-363, and miR-106b-25 that are highly conservative in the process of evolution, and it was thought as a group of microRNAs (miRNAs) correlated with endothelial cells. Aberrant expression of miR-92a family was detected in multiple cancers, and the disturbance of miR-92a family was related with tumorigenesis and tumor development. In this review, the progress on the relationship between miR-92a family and their target genes and malignant tumors will be summarized.

MicroRNA-145 inhibits the growth, invasion, metastasis and angiogenesis of neuroblastoma cells through targeting hypoxia-inducible factor 2 alpha

Recent evidence shows that hypoxia-inducible factor 2 alpha (HIF-2α) may have critical roles in the growth and progression of neuroblastoma (NB) under non-hypoxic conditions. However, the underlying mechanisms and clinical potentials of normoxic HIF-2α expression in NB still remain largely unknown. In this study, HIF-2α immunostaining was identified in 26/42 NB tissues, which was correlated with clinicopathological features. In subtotal 20 NB cases, microRNA-145 (miR-145) was downregulated and inversely correlated with HIF-2α expression. Bioinformatics analysis revealed a putative miR-145 binding site in the 3'-untranslated region (3'-UTR) of HIF-2α messenger RNA (mRNA). Overexpression or knockdown of miR-145 responsively altered both the mRNA and protein levels of HIF-2α and its downstream genes, cyclin D1, matrix metalloproteinase 14 and vascular endothelial growth factor, in normoxically cultured NB cell lines SH-SY5Y and SK-N-SH. In a luciferase reporter system, miR-145 downregulated the luciferase activity of HIF-2α 3'-UTR, and these effects were abolished by a mutation in the putative miR-145-binding site. Overexpression of miR-145 suppressed the growth, invasion, metastasis and angiogenesis of SH-SY5Y and SK-N-SH cells in vitro and in vivo, while restoration of HIF-2α expression rescued the tumor cells from miR-145-mediated defects in these biological features. Furthermore, anti-miR-145 inhibitor rescued the HIF-2α knockdown-mediated repression on the growth, migration, invasion and angiogenesis of NB cells. These data indicate that miR-145 suppresses HIF-2α expression via the binding site in the 3'-UTR under normoxic conditions, thus inhibiting the aggressiveness and angiogenesis of NB.

MicroRNA in aqueous humor from patients with cataract

MicroRNAs (miRNAs) are small non-coding RNA molecules with regulatory function and marked tissue specificity that can modulate multiple gene targets. They have been detected in body fluids and are associated with various physiologic and pathologic processes. We analyzed aqueous humor (AH) from human subjects undergoing cataract surgery to establish the presence and relative quantities of known miRNAs. AH was collected from patients without known ocular diseases other than cataract and a normal systemic history. Quantitative real-time PCR in an array platform was used to detect known miRNAs present in the AH. Among the 264 miRNAs tested, 110 were present in the AH. The top 5 abundant miRNAs identified were miR-202, miR-193b, miR-135a, miR-365, and miR-376a. The presence of miRNAs in AH suggests that they may have functional roles in regulating target genes in tissues lining the anterior chamber. Further analysis of the AH miRNA population may identify potential gene targets and provide insights regarding their roles in AH regulation, glaucoma and anterior segment disease processes.

Micro-RNA-21 regulates the sensitivity to cisplatin in human neuroblastoma cells

BACKGROUND/PURPOSE

Drug resistance often causes treatment failure in neuroblastomas. Increasing evidence has implicated that the micro-RNAs (miRNAs) are involved in the development of drug resistance. In this report, we aimed to investigate the role of miRNA in cisplatin resistance of neuroblastoma cells.

MATERIALS AND METHODS

The cell viability of the neuroblastoma cells after cisplatin treatment was analyzed. The expression of the miRNAs and phosphatase and tensin homolog (PTEN) messenger RNA in the neuroblastoma cells was studied by real-time polymerase chain reaction. Overexpression of miRNA or suppression of miRNA expression by antagomir was used to investigate the effects of miRNA on the cisplatin-induced cell death or proliferation.

RESULTS

The expression of miR-21 was increased in the cisplatin-resistant (CisR) neuroblastoma cells as compared with the parental cells, and the antagomir against miR-21 converted the resistant cells into sensitive ones. Ectopic expression of pre-miR-21 in parental cells resulted in decreased sensitivity to cisplatin treatment. In addition, overexpression of pre-miR-21 markedly increa sed the proliferation rate of neuroblastoma cells. The level of PTEN messenger RNA and protein in the CisR cells was lower than that in the parental cells. Transfection of pre-miR-21 into the parental cells reduced the PTEN expression, and transfection of anti-miR-21 into the CisR cells increased the PTEN expression.

CONCLUSION

Micro-RNA-21 regulated the drug resistance and proliferation in neuroblastoma cells.

New prognostic markers in neuroblastoma

INTRODUCTION

The hallmark of neuroblastoma is its clinical and biological heterogeneity, with the likelihood of cure varying widely according to age at diagnosis, extent of disease and tumor biology. We hope this review will be useful for understanding part of the unfamiliar neuroblastoma codex.

AREAS COVERED

In the first part of this review, the authors summarize the currently used prognostic factors for risk-adapted therapy, with the focus on clinical management of neuroblastoma patients. In the second part, the authors discuss the evolving prognostic factors for future treatment schemes. A search of online medical research databases was undertaken focusing especially on literature published in the last six years.

EXPERT OPINION

Harnessing the synergy of the various forms of data, including clinical variables and biomarker profiles, would allow mathematical predictive models to be built for the individual patient, which could eventually become molecular targets of specific therapies.

Inhibition of neuroblastoma tumor growth by targeted delivery of microRNA-34a using anti-disialoganglioside GD2 coated nanoparticles

Background

Neuroblastoma is one of the most challenging malignancies of childhood, being associated with the highest death rate in paediatric oncology, underlining the need for novel therapeutic approaches. Typically, patients with high risk disease undergo an initial remission in response to treatment, followed by disease recurrence that has become refractory to further treatment. Here, we demonstrate the first silica nanoparticle-based targeted delivery of a tumor suppressive, pro-apoptotic microRNA, miR-34a, to neuroblastoma tumors in a murine orthotopic xenograft model. These tumors express high levels of the cell surface antigen disialoganglioside GD2 (GD₂), providing a target for tumor-specific delivery.

Principal Findings

Nanoparticles encapsulating miR-34a and conjugated to a GD₂ antibody facilitated tumor-specific delivery following systemic administration into tumor bearing mice, resulted in significantly decreased tumor growth, increased apoptosis and a reduction in vascularisation. We further demonstrate a novel, multi-step molecular mechanism by which miR-34a leads to increased levels of the tissue inhibitor metallopeptidase 2 precursor (TIMP2) protein, accounting for the highly reduced vascularisation noted in miR-34a-treated tumors.

Significance

These novel findings highlight the potential of anti-GD₂-nanoparticle-mediated targeted delivery of miR-34a for both the treatment of GD₂-expressing tumors, and as a basic discovery tool for elucidating biological effects of novel miRNAs on tumor growth.

MiRNA-335 suppresses neuroblastoma cell invasiveness by direct targeting of multiple genes from the non-canonical TGF-β signalling pathway

Transforming growth factor-β (TGF-β) signaling regulates many diverse cellular activities through both canonical (SMAD-dependent) and non-canonical branches, which includes the mitogen-activated protein kinase (MAPK), Rho-like guanosine triphosphatase and phosphatidylinositol-3-kinase/AKT pathways. Here, we demonstrate that miR-335 directly targets and downregulates genes in the TGF-β non-canonical pathways, including the Rho-associated coiled-coil containing protein (ROCK1) and MAPK1, resulting in reduced phosphorylation of downstream pathway members. Specifically, inhibition of ROCK1 and MAPK1 reduces phosphorylation levels of the motor protein myosin light chain (MLC) leading to a significant inhibition of the invasive and migratory potential of neuroblastoma cells. Additionally, miR-335 targets the leucine-rich alpha-2-glycoprotein 1 (LRG1) messenger RNA, which similarly results in a significant reduction in the phosphorylation status of MLC and a decrease in neuroblastoma cell migration and invasion. Thus, we link LRG1 to the migratory machinery of the cell, altering its activity presumably by exerting its effect within the non-canonical TGF-β pathway. Moreover, we demonstrate that the MYCN transcription factor, whose coding sequence is highly amplified in a particularly clinically aggressive neuroblastoma tumor subtype, directly binds to a region immediately upstream of the miR-335 transcriptional start site, resulting in transcriptional repression. We conclude that MYCN contributes to neuroblastoma cell migration and invasion, by directly downregulating miR-335, resulting in the upregulation of the TGF-β signaling pathway members ROCK1, MAPK1 and putative member LRG1, which positively promote this process. Our results provide novel insight into the direct regulation of TGF-β non-canonical signaling by miR-335, which in turn is downregulated by MYCN.

miRNA expression profiling of the murine TH-MYCN neuroblastoma model reveals similarities with human tumors and identifies novel candidate miRNAs

BACKGROUND

MicroRNAs are small molecules which regulate gene expression post-transcriptionally and aberrant expression of several miRNAs is associated with neuroblastoma, a childhood cancer arising from precursor cells of the sympathetic nervous system. Amplification of the MYCN transcription factor characterizes the most clinically aggressive subtype of this disease, and although alteration of p53 signaling is not commonly found in primary tumors, deregulation of proteins involved in this pathway frequently arise in recurrent disease after pharmacological treatment. TH-MYCN is a well-characterized transgenic model of MYCN-driven neuroblastoma which recapitulates many clinicopathologic features of the human disease. Here, we evaluate the dysregulation of miRNAs in tumors from TH-MYCN mice that are either wild-type (TH-MYCN) or deficient (TH-MYCN/p53ER(TAM)) for the p53 tumor suppressor gene.

PRINCIPAL FINDINGS

We analyzed the expression of 591 miRNAs in control (adrenal) and neuroblastoma tumor tissues derived from either TH-MYCN or TH-MYCN/p53ER(TAM) mice, respectively wild-type or deficient in p53. Comparing miRNA expression in tumor and control samples, we identified 159 differentially expressed miRNAs. Using data previously obtained from human neuroblastoma samples, we performed a comparison of miRNA expression between murine and human tumors to assess the concordance between murine and human expression data. Notably, the miR-17-5p-92 oncogenic polycistronic cluster, which is over-expressed in human MYCN amplified tumors, was over-expressed in mouse tumors. Moreover, analyzing miRNAs expression in a mouse model (TH-MYCN/p53ER(TAM)) possessing a transgenic p53 allele that drives the expression of an inactive protein, we identified miR-125b-3p and miR-676 as directly or indirectly regulated by the level of functional p53.

SIGNIFICANCE

Our study represents the first miRNA profiling of an important mouse model of neuroblastoma. Similarities and differences in miRNAs expression between human and murine neuroblastoma were identified, providing important insight into the efficacy of this mouse model for assessing miRNA involvement in neuroblastoma and their potential effectiveness as therapeutic targets.

HIV-1 Tat protein promotes neuronal dysfunction through disruption of microRNAs

Over the last decade, small noncoding RNA molecules such as microRNAs (miRNAs) have emerged as critical regulators in the expression and function of eukaryotic genomes. It has been suggested that viral infections and neurological disease outcome may also be shaped by the influence of small RNAs. This has prompted us to suggest that HIV infection alters the endogenous miRNA expression patterns, thereby contributing to neuronal deregulation and AIDS dementia. Therefore, using primary cultures and neuronal cell lines, we examined the impact of a viral protein (HIV-1 Tat) on the expression of miRNAs due to its characteristic features such as release from the infected cells and taken up by noninfected cells. Using microRNA array assay, we demonstrated that Tat deregulates the levels of several miRNAs. Interestingly, miR-34a was among the most highly induced miRNAs in Tat-treated neurons. Tat also decreases the levels of miR-34a target genes such as CREB protein as shown by real time PCR. The effect of Tat was neutralized in the presence of anti-miR-34a. Using in situ hybridization assay, we found that the levels of miR-34a increase in Tat transgenic mice when compared with the parental mice. Therefore, we conclude that deregulation of neuronal functions by HIV-1 Tat protein is miRNA-dependent.

Deregulation of microRNAs by HIV-1 Vpr protein leads to the development of neurocognitive disorders

Studies have shown that HIV-infected patients develop neurocognitive disorders characterized by neuronal dysfunction. The lack of productive infection of neurons by HIV suggests that viral and cellular proteins, with neurotoxic activities, released from HIV-1-infected target cells can cause this neuronal deregulation. The viral protein R (Vpr), a protein encoded by HIV-1, has been shown to alter the expression of various important cytokines and inflammatory proteins in infected and uninfected cells; however the mechanisms involved remain unclear. Using a human neuronal cell line, we found that Vpr can be taken up by neurons causing: (i) deregulation of calcium homeostasis, (ii) endoplasmic reticulum-calcium release, (iii) activation of the oxidative stress pathway, (iv) mitochondrial dysfunction and v- synaptic retraction. In search for the cellular factors involved, we performed microRNAs and gene array assays using human neurons (primary cultures or cell line, SH-SY5Y) that we treated with recombinant Vpr proteins. Interestingly, Vpr deregulates the levels of several microRNAs (e.g. miR-34a) and their target genes (e.g. CREB), which could lead to neuronal dysfunctions. Therefore, we conclude that Vpr plays a major role in neuronal dysfunction through deregulating microRNAs and their target genes, a phenomenon that could lead to the development of neurocognitive disorders.