Silencing of the miR-17~92 cluster family inhibits medulloblastoma progression

Sonic Hedgehog Medulloblastoma Cancer Stem Cells Mirnome and Transcriptome Highlight Novel Functional Networks

Molecular classification has improved the knowledge of medulloblastoma (MB), the most common malignant brain tumour in children, however current treatments cause severe side effects in patients. Cancer stem cells (CSCs) have been described in MB and represent a sub population characterised by self-renewal and the ability to generate tumour cells, thus representing the reservoir of the tumour. To investigate molecular pathways that characterise this sub population, we isolated CSCs from Sonic Hedgehog Medulloblastoma (SHH MB) arisen in Patched 1 (Ptch1) heterozygous mice, and performed miRNA- and mRNA-sequencing. Comparison of the miRNA-sequencing of SHH MB CSCs with that obtained from cerebellar Neural Stem Cells (NSCs), allowed us to obtain a SHH MB CSC miRNA differential signature. Pathway enrichment analysis in SHH MB CSCs mirnome and transcriptome was performed and revealed a series of enriched pathways. We focused on the putative targets of the SHH MB CSC miRNAs that were involved in the enriched pathways of interest, namely pathways in cancer, PI3k-Akt pathway and protein processing in endoplasmic reticulum pathway. In silico analysis was performed in SHH MB patients and identified several genes, whose expression was associated with worse overall survival of SHH MB patients. This study provides novel candidates whose functional role should be further investigated in SHH MB.

The emerging role of miR-19 in glioma

Glioma has been regarded as the most common, highly proliferative and invasive brain tumour. Advances in research of miRNAs in glioma are toward further understanding of the pathogenesis of glioma. MiR‐19, a member of miR‐17~92 cluster, was reported to play an oncogenic role in tumourigenesis. Here we review the identified data about the effect of miR‐19 on proliferation, apoptosis, migration and invasion of glioma cells, the target genes regulated by miR‐19, and correlation of miR‐19 with the sensitivity of glioma cells to chemotherapy and radiotherapy. It is concluded that miR‐19 plays an important role in the pathogenesis of glioma and can be a potential target for gene therapy of glioma.

Up-Regulation of miR-21, miR-25, miR-93, and miR-106b in Gastric Cancer

Background:

Differential expression profile of microRNAs (miRNAs) could be a diagnosis signature for monitoring gastric cancer (GC) progression. In this study, we focus on the comparison of expression levels of miR-21, miR-25, miR-93, miR-106b, and miR-375 during the sequential pattern of GC development, including normal gastric, gastric dysplasia, and GC sample.

Methods:

We used SYBR Green-based quantitative-PCR to quantify miRNAs expression.

Results:

Our analysis revealed the increased expression levels of miR-21 (p = 0.034), miR-25 (p = 0.0003), miR-93 (p = 0.0406), and miR-106b (p = 0.023) in GC samples. In addition, GC patients with positive lymph node metastasis showed the up-regulation of miR-25, miR-93, and miR-106b (p < 0.05).

Conclusion:

Our findings suggested that the expression of miR-21, miR-25, miR-93, and miR-106b altered in GC, and some of them may be further investigated as biomarkers for GC early detection and prognosis prediction.

MicroRNAs of the mir-17~92 cluster regulate multiple aspects of pancreatic tumor development and progression

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy characterized by resistance to currently employed chemotherapeutic approaches. Members of the mir-17~92 cluster of microRNAs (miRNAs) are upregulated in PDAC, but the precise roles of these miRNAs in PDAC are unknown. Using genetically engineered mouse models, we show that loss of mir-17~92 reduces ERK pathway activation downstream of mutant KRAS and promotes the regression of KRAS^G12D-driven precursor pancreatic intraepithelial neoplasias (PanINs) and their replacement by normal exocrine tissue. In a PDAC model driven by concomitant KRAS^G12D expression and Trp53 heterozygosity, mir-17~92 deficiency extended the survival of mice that lacked distant metastasis. Moreover, mir-17~92-deficient PDAC cell lines display reduced invasion activity in transwell assays, form fewer invadopodia rosettes than mir-17~92-competent cell lines and are less able to degrade extracellular matrix. Specific inhibition of miR-19 family miRNAs with antagomirs recapitulates these phenotypes, suggesting that miR-19 family miRNAs are important mediators of PDAC cell invasion. Together these data demonstrate an oncogenic role for mir-17~92 at multiple stages of pancreatic tumorigenesis and progression; specifically, they link this miRNA cluster to ERK pathway activation and precursor lesion maintenance in vivo and identify a novel role for miR-19 family miRNAs in promoting cancer cell invasion.

The miR-139-5p regulates proliferation of supratentorial paediatric low-grade gliomas by targeting the PI3K/AKT/mTORC1 signalling

AIMS

Paediatric low-grade gliomas (pLGGs) are a heterogeneous group of brain tumours associated with a high overall survival: however, they are prone to recur and supratentorial lesions are difficult to resect, being associated with high percentage of disease recurrence. Our aim was to shed light on the biology of pLGGs.

METHODS

We performed microRNA profiling on 45 fresh-frozen grade I tumour samples of various histological classes, resected from patients aged ≤16 years. We identified 93 microRNAs specifically dysregulated in tumours as compared to non-neoplastic brain tissue. Pathway analysis of the microRNAs signature revealed PI3K/AKT signalling as one of the centrally enriched oncogenic signalling. To date, activation of the PI3K/AKT pathway in pLGGs has been reported, although activation mechanisms have not been fully investigated yet.

RESULTS

One of the most markedly down-regulated microRNAs in our supratentorial pLGGs cohort was miR-139-5p, whose targets include the gene encoding the PI3K's (phosphatidylinositol 3-kinase) catalytic unit, PIK3CA. We investigated the role of miR-139-5p in regulating PI3K/AKT signalling by the use of human cell cultures derived from supratentorial pLGGs. MiR-139-5p overexpression inhibited pLGG cell proliferation and decreased the phosphorylation of PI3K target AKT and phosphorylated-p70 S6 kinase (p-p70 S6K), a hallmark of PI3K/AKT/mTORC1 signalling activation. The effect of miR-139-5p was mediated by PI3K inhibition, as suggested by the decrease in proliferation and phosphorylation of AKT and p70 S6K after treatment with the direct PI3K inhibitor LY294002.

CONCLUSIONS

These findings provide the first evidence that down-regulation of miR-139-5p in supratentorial pLGG drives cell proliferation by derepressing PI3K/AKT signalling.

The Oncogenic Relevance of miR-17-92 Cluster and Its Paralogous miR-106b-25 and miR-106a-363 Clusters in Brain Tumors

The fundamental function of ribonucleic acids is to transfer genetic information from DNA to protein during translation process, however, this is not the only way connecting active RNA sequences with essential biological processes. Up until now, many RNA subclasses of different size, structure, and biological function were identified. Among them, there are non-coding single-stranded microRNAs (miRNAs). This subclass comprises RNAs of 19–25 nucleotides in length that modulate the activity of well-defined coding RNAs and play a crucial role in many physiological and pathological processes. miRNA genes are located both in exons, introns, and also within non-translated regions. Several miRNAs that are transcribed from the adjacent miRNA genes are called cluster. One of the largest ones is miR-17-92 cluster known as OncomiR-1 due to its strong link to oncogenesis. Six miRNAs from the OncomiR-1 have been shown to play important roles in various physiological cellular processes but also through inhibition of cell death in many cancer-relevant processes. Due to the origin and similarity of the sequence, miR-17-92 cluster and paralogs, miR-106b-25 and miR-106a-363 clusters were defined. Here we discuss the oncogenic function of those miRNA subgroups found in many types of cancers, including brain tumors.

Ex vivo miRNome analysis in Ptch1+/- cerebellum granule cells reveals a subset of miRNAs involved in radiation-induced medulloblastoma

It has historically been accepted that incorrectly repaired DNA double strand breaks (DSBs) are the principal lesions of importance regarding mutagenesis, and long-term biological effects associated with ionizing radiation. However, radiation may also cause dysregulation of epigenetic processes that can lead to altered gene function and malignant transformation, and epigenetic alterations are important causes of miRNAs dysregulation in cancer.

Patched1 heterozygous (Ptch1^+/−) mice, characterized by aberrant activation of the Sonic hedgehog (Shh) signaling pathway, are a well-known murine model of spontaneous and radiation-induced medulloblastoma (MB), a common pediatric brain tumor originating from neural granule cell progenitors (GCPs). The high sensitivity of neonatal Ptch1^+/− mice to radiogenic MB is dependent on deregulation of the Ptch1 gene function. Ptch1 activates a growth and differentiation programme that is a strong candidate for regulation through the non-coding genome. Therefore we carried out miRNA next generation sequencing in ex vivo irradiated and control GCPs, isolated and purified from cerebella of neonatal WT and Ptch1^+/− mice. We identified a subset of miRNAs, namely let-7 family and miR-17∼92 cluster members, whose expression is altered in GCPs by radiation alone, or by synergistic interaction of radiation with Shh-deregulation. The same miRNAs were further validated in spontaneous and radiation-induced MBs from Ptch1^+/− mice, confirming persistent deregulation of these miRNAs in the pathogenesis of MB.

Our results support the hypothesis that miRNAs dysregulation is associated with radiosensitivity of GCPs and their neoplastic transformation in vivo.

MicroRNA-mRNA expression profiles associated with medulloblastoma subgroup 4

Purpose

Medulloblastoma (MB), the most common malignant brain tumor in children, is divided into four tumor subgroups: wingless-type (WNT), sonic hedgehog (SHH), Group 3, and Group 4. Ideally, clinical practice and treatment design should be subgroup specific. While WNT and SHH subgroups have well-defined biomarkers, distinguishing Group 3 from Group 4 is not straightforward. MicroRNAs (miRNAs), which regulate posttranscriptional gene expression, are involved in MB tumorigenesis. However, the miRNA–messenger RNA (mRNA) regulatory network in MB is far from being fully understood. Our aims were to investigate miRNA expression regulation in MB subgroups, to assess miRNA target relationships, and to identify miRNAs that can distinguish Group 3 from Group 4.

Patients and methods

With these aims, integrated transcriptome mRNA and miRNA expression analysis was performed on primary tumor samples collected from 18 children with MB, using miRNA sequencing (miRNA-seq), RNA sequencing (RNA-seq), and quantitative PCR.

Results

Of all the expressed miRNAs, 19 appeared to be significantly differentially expressed (DE) between Group 4 and non-Group 4 subgroups (false discovery rate [FDR] <0.05), including 10 miRNAs, which, for the first time, are reported to be in conjunction with MB. RNA-seq analysis identified 165 genes that were DE between Group 4 and the other subgroups (FDR <0.05), among which seven are predicted targets of five DE miRNAs and exhibit inverse expression pattern.

Conclusion

This study identified miRNA molecules that may be involved in Group 4 etiology, in general, and can distinguish between Group 3 and Group 4, in particular. In addition, understanding the involvement of miRNAs and their targets in MB may improve diagnosis and advance the development of targeted treatment for MB.

Nanog-driven cell-reprogramming and self-renewal maintenance in Ptch1 +/- granule cell precursors after radiation injury

Medulloblastoma (MB) is the most common pediatric brain tumor, comprising four distinct molecular variants, one of which characterized by activation of the Sonic Hedgehog (SHH) pathway, driving 25–30% of sporadic MB. SHH-dependent MBs arise from granule cell precursors (GCPs), are fatal in 40–70% of cases and radioresistance strongly contributes to poor prognosis and tumor recurrence. Patched1 heterozygous (Ptch1^+/−) mice, carrying a germ-line heterozygous inactivating mutation in the Ptch1 gene, the Shh receptor and negative regulator of the pathway, are uniquely susceptible to MB development after radiation damage in neonatal cerebellum. Here, we irradiated ex-vivo GCPs isolated from cerebella of neonatal WT and Ptch1^+/− mice. Our results highlight a less differentiated status of Ptch1-mutated cells after irradiation, influencing DNA damage response. Increased expression levels of pluripotency genes Nanog, Oct4 and Sal4, together with greater clonogenic potential, clearly suggest that radiation induces expansion of the stem-like cell compartment through cell-reprogramming and self-renewal maintenance, and that this mechanism is strongly dependent on Nanog. These results contribute to clarify the molecular mechanisms that control radiation-induced Shh-mediated tumorigenesis and may suggest Nanog as a potential target to inhibit for adjuvant radiotherapy in treatment of SHH-dependent MB.

Expression, regulation and mechanism of action of the miR-17-92 cluster in tumor cells (Review)

MicroRNAs (miRNAs), a class of short, single-stranded non-coding RNAs, regulate and control gene expression in eukaryotes by degrading mRNA at the post-transcriptional level. Regulation by miRNAs involves a plethora of biological processes, such as cell differentiation, proliferation, metastasis, metabolism, apoptosis, tumorigenesis and others. miRNAs also represent a powerful tool in disease diagnosis and prognosis. The miR-17-92 cluster, one of the most extensively investigated microRNA clusters, comprises six mature miRNA members, including miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a. Originally identified as being involved in tumorigenesis, it is currently evident that the expression of the miR-17-92 cluster is upregulated in a wide range of tumor cells and cancer types; thus, this cluster has been identified as a potential oncogene. Considering the growing interest in the field of miR-17-92 research, we herein review recent advances in the expression and regulation of this cluster in various cancer cells, discuss the proposed mechanism of action for tumorigenesis and tumor development, and propose clinical and therapeutic applications for miR-17-92 cluster members, such as potential cancer biomarkers.

Dicer1 Ablation Impairs Responsiveness of Cerebellar Granule Neuron Precursors to Sonic Hedgehog and Disrupts Expression of Distinct Cell Cycle Regulator Genes

Granule neuron precursors (GNPs) proliferate under the influence of Sonic hedgehog (Shh) that is secreted by Purkinje neurons during early postnatal cerebellar development. To investigate microRNA (miRNA) function in this developmental process, we conditionally deleted the Dicer1 gene under the activity of human glial fibrillary acidic protein (hGFAP) promoter. We report that Dicer1-ablated GNPs display decreased proliferation and survival at early postnatal stages and that the proliferation defect of mutant GNPs cannot be rescued by treatment of an Shh agonist in vitro as assayed by 5-bromo-2'-deoxyuridine (BrdU) pulse labeling and Shh target gene expression detection. Further analysis reveals that the expression of distinct cell cycle regulator genes including cell cycle inhibitor, CDKN1a (p21), selectively increases in Dicer1-ablated GNPs. Subsequently, we demonstrate that miR-17-5p exhibits high expression level in the developing cerebellum and that transfection of a synthetic miR-17-5p mimic downregulates p21 protein expression in GNPs and promotes proliferation of GNPs in culture. Therefore, Dicer1 ablation impairs Shh-induced GNP proliferation by disrupting the expression of distinct cell cycle regulator genes that are targets of miR-17∼92 cluster members. This study establishes a molecular link between miRNAs and cell cycle progression in the proliferating GNPs during normal cerebellar development and may facilitate miRNA application in treating medulloblastoma.

Novel MYC-driven medulloblastoma models from multiple embryonic cerebellar cells

Group3 medulloblastoma (MBG3) that predominantly occur in young children are usually associated with MYC amplification and/or overexpression, frequent metastasis and a dismal prognosis. Physiologically relevant MBG3 models are currently lacking, making inferences related to their cellular origin thus far limited. Using in utero electroporation, we here report that MBG3 mouse models can be developed in situ from different multipotent embryonic cerebellar progenitor cells via conditional expression of Myc and loss of Trp53 function in several Cre driver mouse lines. The Blbp-Cre driver that targets embryonic neural progenitors induced tumors exhibiting a large-cell/anaplastic histopathology adjacent to the fourth ventricle, recapitulating human MBG3. Enforced co-expression of luciferase together with Myc and a dominant-negative form of Trp53 revealed that GABAergic neuronal progenitors as well as cerebellar granule cells give rise to MBG3 with their distinct growth kinetics. Cross-species gene expression analysis revealed that these novel MBG3 models shared molecular characteristics with human MBG3, irrespective of their cellular origin. We here developed MBG3 mouse models in their physiological environment and we show that oncogenic insults drive this MB subgroup in different cerebellar lineages rather than in a specific cell of origin.

miR-140-5p suppresses the proliferation, migration and invasion of gastric cancer by regulating YES1

BACKGROUND

The aberrant expression of microRNA-140-5p (miR-140-5p) has been described in gastric cancer (GC). However, the role of miR-140-5p in GC remains unclear. In this study, the prognostic relevance of miR-140-5p in GC was investigated and YES1 was identified as a novel target of miR-140-5p in regulating tumor progression.

METHODS

miR-140-5p level was determined in 20 paired frozen specimens through quantitative real-time PCR, and analyzed in tissue microarrays through in situ hybridization. The target of miR-140-5p was verified through a dual luciferase reporter assay, and the effects of miR-140-5p on phenotypic changes in GC cells were investigated in vitro and in vivo.

RESULTS

Compared with that in adjacent normal tissues, miR-140-5p expression decreased in cancerous tissues. The downregulated miR-140-5p in 144 patients with GC was significantly correlated with the reduced overall survival of these patients. miR-140-5p could inhibit GC cell proliferation, migration and invasion by directly targeting 3'-untranlated region of YES1. miR-140-5p could also remarkably reduce the tumor size in GC xenograft mice.

CONCLUSIONS

miR-140-5p serves as a potential prognostic factor in patients with GC, and miR-140-5p mediated YES1 inhibition is a novel mechanism behind the suppressive effects of miR-140-5p in GC.

Animal Models to Study MicroRNA Function

The discovery of the microRNAs, lin-4 and let-7 as critical mediators of normal development in Caenorhabditis elegans and their conservation throughout evolution has spearheaded research toward identifying novel roles of microRNAs in other cellular processes. To accurately elucidate these fundamental functions, especially in the context of an intact organism, various microRNA transgenic models have been generated and evaluated. Transgenic C. elegans (worms), Drosophila melanogaster (flies), Danio rerio (zebrafish), and Mus musculus (mouse) have contributed immensely toward uncovering the roles of multiple microRNAs in cellular processes such as proliferation, differentiation, and apoptosis, pathways that are severely altered in human diseases such as cancer. The simple model organisms, C. elegans, D. melanogaster, and D. rerio, do not develop cancers but have proved to be convenient systesm in microRNA research, especially in characterizing the microRNA biogenesis machinery which is often dysregulated during human tumorigenesis. The microRNA-dependent events delineated via these simple in vivo systems have been further verified in vitro, and in more complex models of cancers, such as M. musculus. The focus of this review is to provide an overview of the important contributions made in the microRNA field using model organisms. The simple model systems provided the basis for the importance of microRNAs in normal cellular physiology, while the more complex animal systems provided evidence for the role of microRNAs dysregulation in cancers. Highlights include an overview of the various strategies used to generate transgenic organisms and a review of the use of transgenic mice for evaluating preclinical efficacy of microRNA-based cancer therapeutics.

MiR-93 Promotes Tumorigenesis and Metastasis of Non-Small Cell Lung Cancer Cells by Activating the PI3K/Akt Pathway via Inhibition of LKB1/PTEN/CDKN1A

BACKGROUND

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of clinical lung cancer cases. MicroRNA-93 (miR-93) is an oncomiR in many types of human cancer, exerting pivotal effects in the development and progression of malignancies, including NSCLC. However, the mechanism underlying miR-93 involvement in NSCLC is unknown. Our purpose was to reveal and explain this mechanism, with the goal of contributing to the development of new diagnostic biomarkers and individualized therapeutic tools.

METHODS

The expression of miR-93 was determined in NSCLC cell lines A549, H1975, and H1299. The cells were transfected with control plasmids (Mock group), miR-93 overexpression plasmids (miR-93 Up group), or miR-93 inhibitor plasmids (miR-93 Down group) to generate stable miR-93-overexpressing or -depleted cells. The effects of miR-93 on proliferation, migration, and invasion of these cells were determined. The in vivo effects of miR-93 on tumor metastasis were determined in an NSCLC xenograft mouse model. The molecular mechanisms underlying these effects were investigated via dual luciferase reporter assay and western blotting.

RESULTS

MiR-93 expression levels were significantly greater in the NSCLC cell lines than in normal lung epithelial cells. Cell proliferation, migration, and invasion were significantly stimulated by miR-93 upregulation (all P<0.05) and inhibited by miR-93 downregulation. Dual luciferase reporter assay demonstrated that miR-93 directly bound with the 3'-untranslated region of the tumor suppressor gene LKB1. Western blotting analysis indicated that miR-93 activated the PI3K/Akt pathway by inhibiting LKB1, PTEN, and p21. Increased expression of miR-93 induced significant hepatic metastasis of lung cancer in the xenograft mouse model.

CONCLUSION

Overexpression of miR-93 facilitates tumorigenesis and metastasis of NSCLC. These findings provide novel insight into the mechanism of miR-93 involvement in NSCLC, suggesting that miR-93 may serve as a potential therapeutic target.

Disturbance of the let-7/LIN28 double-negative feedback loop is associated with radio- and chemo-resistance in non-small cell lung cancer

Radio- and chemo-resistance represent major obstacles in the therapy of non-small-cell lung cancer (NSCLC) and the underlying molecular mechanisms are not known. In the present study, during induction of radio- or chemo-resistance in NSCLC cells, dynamic analyses revealed that decreased expression of let-7 induced by irradiation or cisplatin resulted in increased expression of its target gene LIN28, and increased expression of LIN28 then contributed to further decreased expression of let-7 by inhibiting its maturation and biogenesis. Moreover, we showed that down-regulation of let-7 and up-regulation of LIN28 expression promoted resistance to irradiation or cisplatin by regulating the single-cell proliferative capability of NSCLC cells. Consequently, in NSCLC cells, let-7 and LIN28 can form a double-negative feedback loop through mutual inhibition, and disturbance of the let-7/LIN28 double-negative feedback loop induced by irradiation or chemotherapeutic drugs can result in radio- and chemo-resistance. In addition, low expression of let-7 and high expression of LIN28 in NSCLC patients was associated significantly with resistance to radiotherapy or chemotherapy. Therefore, our study demonstrated that disturbance of the let-7/LIN28 double-negative feedback loop is involved in the regulation of radio- and chemo-resistance, and that let-7 and LIN28 could be employed as predictive biomarkers of response to radiotherapy or chemotherapy in NSCLC patients.

The role of miR-17-92 cluster in the expression of tumor suppressor genes in unrestricted somatic stem cells

The miR-17-92 cluster consisted of seven miRNAs (mir-17-5p, -17-3p, -18a, -19a, -20a, -19b-1, and -92a-1). Previous studies have shown this cluster has been over-expressed in several cancers. The aim of this study was to evaluate the over-expression impacts of miR-17-92 on stem cells. In the current work, the effect of miR-17-92 cluster which was cloned in Lentiviral vector has been investigated on unrestricted somatic stem cells (USSCs). Tumor suppressor genes (p53, p15, RBL1, SMAD2, SMAD4, and MAPK-1) expression, especially p53, was considerably reduced. These data show the potential of miR-17-92 for oncogenesis regulation in stem cells. In conclusion, the role of miR-17-92 in USSCs may provide a better understanding of its function in tumorigenesis and for the possible use in cell therapy of the anti-mir-17-92 cluster.

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.

Roles of miR-17-92 Cluster in Cardiovascular Development and Common Diseases

MicroRNAs (miRNAs and miRs) are a large class of noncoding, single-stranded, small RNA molecules. The precise control of their expression is essential for keeping tissue homeostasis and normal development of organisms. Thus, unbalanced expression of miRNAs is a hallmark of many diseases. Two to dozens of miRNAs can form into a miRNA cluster, and the miR-17-92 cluster is one of them. Although firstly described as an oncogenic miRNA cluster, the miR-17-92 cluster has also been found to play critical role in normal cardiac development and cardiovascular disease. This review focuses on the characteristics and functions of miR-17-92 cluster in heart.

MicroRNAs in Oncogenesis and Tumor Suppression

MicroRNAs (MiRNAs) have emerged in the last 15 years as central players in the biology of cancer. Increasing lines of evidence have supported their regulatory role in the expression of both oncogenes and tumor-suppressor genes, progressively clarifying which genes are modulated by specific MiRNAs dysregulated in cancer. Intriguingly, a "target-specific" understanding of MiRNA function in oncology has been replaced by a more "pathway-specific" vision of their involvement in cancer biology. This work provides a state-of-the-art knowledge of the role of MiRNAs in the most frequently altered signaling pathways in cancer cells and provides an updated overview on some of the most relevant findings trying to decode the complex molecular mechanisms of cancer.

Integrative analysis of signaling pathways and diseases associated with the miR-106b/25 cluster and their function study in berberine-induced multiple myeloma cells

Berberine (BBR), a traditional Chinese herbal medicine compound, has emerged as a novel class of anti-tumor agent. Our previous microRNA (miRNA) microarray demonstrated that miR-106b/25 was significantly down-regulated in BBR-treated multiple myeloma (MM) cells. Here, systematic integration showed that miR-106b/25 cluster is involved in multiple cancer-related signaling pathways and tumorigenesis. MiREnvironment database revealed that multiple environmental factors (drug, ionizing radiation, hypoxia) affected the miR-106b/25 cluster expression. By targeting the seed region in the miRNA, tiny anti-mir106b/25 cluster (t-anti-mir106b/25 cluster) significantly induced suppression in cell viability and colony formation. Western blot validated that t-anti-miR-106b/25 cluster effectively inhibited the expression of P38 MAPK and phospho-P38 MAPK in MM cells. These findings indicated the miR-106b/25 cluster functioned as oncogene and might provide a novel molecular insight into MM.

MicroRNAs Promote Granule Cell Expansion in the Cerebellum Through Gli2

MicroRNAs (miRNAs) are important regulators of cerebellar function and homeostasis. Their deregulation results in cerebellar neuronal degeneration and spinocerebellar ataxia type 1 and contributes to medulloblastoma. Canonical miRNA processing involves Dicer, which cleaves precursor miRNAs into mature double-stranded RNA duplexes. In order to address the role of miRNAs in cerebellar granule cell precursor development, loxP-flanked exons of Dicer1 were conditionally inactivated using the granule cell precursor-specific Atoh1-Cre recombinase. A reduction of 87% in Dicer1 transcript was achieved in this conditional Dicer knockdown model. Although knockdown resulted in normal survival, mice had disruptions to the cortical layering of the anterior cerebellum, which resulted from the premature differentiation of granule cell precursors in this region during neonatal development. This defect manifested as a thinner external granular layer with ectopic mature granule cells, and a depleted internal granular layer. We found that expression of the activator components of the Hedgehog-Patched pathway, the Gli family of transcription factors, was perturbed in conditional Dicer knockdown mice. We propose that loss of Gli2 mRNA mediated the anterior-restricted defect in conditional Dicer knockdown mice and, as proof of principle, were able to show that miR-106b positively regulated Gli2 mRNA expression. These findings confirm the importance of miRNAs as positive mediators of Hedgehog-Patched signalling during granule cell precursor development.

microRNAs with AAGUGC seed motif constitute an integral part of an oncogenic signaling network

microRNA (miRNA) dysregulation is a common feature of cancer cells, but the complex roles of miRNAs in cancer are not fully elucidated. Here, we used functional genomics to identify oncogenic miRNAs in non-small cell lung cancer and evaluate their impact on response to epidermal growth factor (EGFR)-targeting therapy. Our data demonstrate that miRNAs with an AAGUGC motif in their seed sequence increase both cancer cell proliferation and sensitivity to EGFR inhibitors. Global transcriptomics, proteomics and target prediction resulted in the identification of several tumor suppressors involved in the G1/S transition as AAGUGC-miRNA targets. The clinical implications of our findings were evaluated by analysis of AAGUGC-miRNA expression in multiple cancer types, supporting the link between this miRNA seed family, their tumor suppressor targets and cancer cell proliferation. In conclusion, we propose the AAGUGC seed motif as an oncomotif and that oncomotif-miRNAs promote cancer cell proliferation. These findings have potential therapeutic implications, especially in selecting patients for EGFR-targeting therapy.

MicroRNA-17/20a impedes migration and invasion via TGF-β/ITGB6 pathway in esophageal squamous cell carcinoma

Patients with esophageal squamous cell carcinoma (ESCC) have an overall poor prognosis due to invasion and metastasis. Although it has been studied extensively, the metastatic mechanisms of ESCC remains largely unclear. Here, we evaluated microRNA expression in ESCC cell sublines with distinct motility and found that microRNA-17 and microRNA-20a (miR-17/20a) dramatically impeded cell migration and invasion of ESCC in vitro and decreased pulmonary arrest in vivo. Furthermore, we identified that TGF-β receptor 2 (TGFBR2) and Smad anchor for receptor activation (SARA) served as genuine miR-17/20a targets, which are both implicated in TGF-β pathway. TGF-β treatment promoted the motility of ESCC cells, and miR-17/20a could attenuate the activation of TGF-β pathway by weakening the phosphorylation of Smad2/3 to reduce the expression of ITGB6, which was crucial in migration and invasion of ESCC cells. Moreover, evaluation of ESCC specimens revealed a close correlation between miR-17/20a, TGFBR2, SARA and lymph node metastasis. Together, our findings demonstrate that miR-17/20a suppresses cell migration and invasion of ESCC by modulating TGF-β/ITGB6 pathway, suggesting a promising strategy for diagnosis and therapy of ESCC invasion and metastasis.

miR-135a Inhibits Cancer Stem Cell-Driven Medulloblastoma Development by Directly Repressing Arhgef6 Expression

microRNAs (miRNAs) are short noncoding RNAs, which regulate gene expression post-transcriptionally and play crucial roles in relevant biological and pathological processes. Here, we investigated the putative role of miRNAs in modulating the tumor-initiating potential of mouse medulloblastoma (MB)-derived cancer stem cells (CSCs). We first subjected bona fide highly tumorigenic (HT) CSCs as well as lowly tumorigenic MB CSCs and normal neural stem cells to miRNA profiling, which identified a HT CSC-specific miRNA signature. Next, by cross-checking CSC mRNA/miRNA profiles, we pinpointed miR-135a as a potential tumor suppressor gene, which was strongly downregulated in HT CSCs as well as in the highly malignant experimental tumors derived from them. Remarkably, enforced expression of miR-135a in HT CSCs strongly inhibited tumorigenesis by repressing the miR-135a direct target gene Arhgef6. Considering the upregulation of Arhgef6 in human MBs and its involvement in mediating experimental medulloblastomagenesis, its efficient suppression by miR-135a might make available an effective therapeutic strategy to selectively impair the tumorigenic potential of MB CSCs. Stem Cells 2015;33:1377-1389.

General hallmarks of microRNAs in brain evolution and development

MicroRNAs (miRNAs) are endogenous, small non-coding RNA molecules that mediate post-transcriptional gene suppression by incomplete matches with their host mRNAs. In the central nervous system, miRNAs that functionally interact with their target genes constitute a flexible, robust and buffered regulatory network, exerting diverse roles in brain evolution and development. However, distinct variation either in hub miRNA expression levels or patterns may initiate and/or progress various adult-onset nerve-related diseases. In this review, we will summarize the current knowledge about the general hallmarks of brain miRNAs that act as vital determinants in increasingly complicated neural activities. We endeavor to provide a constructive insight into the neuroscience research in the quest to comprehend molecular underpinnings of physiological functions and pathological disorders in central nervous system.

Inhibition of miR-154 Protects Against Cardiac Dysfunction and Fibrosis in a Mouse Model of Pressure Overload

Expression of miR-154 is upregulated in the diseased heart and was previously shown to be upregulated in the lungs of patients with pulmonary fibrosis. However, the role of miR-154 in a model of sustained pressure overload-induced cardiac hypertrophy and fibrosis had not been assessed. To examine the role of miR-154 in the diseased heart, adult male mice were subjected to transverse aortic constriction for four weeks, and echocardiography was performed to confirm left ventricular hypertrophy and cardiac dysfunction. Mice were then subcutaneously administered a locked nucleic acid antimiR-154 or control over three consecutive days (25 mg/kg/day) and cardiac function was assessed 8 weeks later. Here, we demonstrate that therapeutic inhibition of miR-154 in mice with pathological hypertrophy was able to protect against cardiac dysfunction and attenuate adverse cardiac remodelling. The improved cardiac phenotype was associated with attenuation of heart and cardiomyocyte size, less cardiac fibrosis, lower expression of atrial and B-type natriuretic peptide genes, attenuation of profibrotic markers, and increased expression of p15 (a miR-154 target and cell cycle inhibitor). In summary, this study suggests that miR-154 may represent a novel target for the treatment of cardiac pathologies associated with cardiac fibrosis, hypertrophy and dysfunction.

The miR-130 family promotes cell migration and invasion in bladder cancer through FAK and Akt phosphorylation by regulating PTEN

Bladder cancer causes an estimated 150,000 deaths per year worldwide. Although 15% of the recurrent bladder cancer becomes an invasive type, currently used targeted therapy for malignant bladder cancer is still not efficient. We focused on the miR-130 family (miR-130b, miR-301a, and miR-301b) that was significantly upregulated in bladder cancer specimens than that of the normal urothelial specimens. We analyzed the functional significance of miR-130 family using a 5637 bladder cancer cell line and revealed that miR-130 family of inhibitors suppressed cell migration and invasion by downregulating focal adhesion kinase (FAK) and Akt phosphorylation. Mechanistic analyses indicate that the miR-130 family directly targets phosphatase and tensin homolog deleted from chromosome 10 (PTEN), resulting in the upregulation of FAK and Akt phosphorylation. In clinical bladder cancer specimens, downregulation of PTEN was found to be closely correlated with miR-130 family expression levels. Overall, the miR-130 family has a crucial role in malignant progression of bladder cancer and thus the miR-130 family could be a promising therapeutic target for invasive bladder cancer.

The biomarker and therapeutic potential of miRNA in Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia. Currently, a clinical diagnosis of AD is based on evidence of both cognitive and functional decline. Progression is monitored by detailed clinical evaluations over many months to years. It is increasingly clear that to advance disease-modifying therapies for AD, patients must be identified and treated early, before obvious cognitive and functional changes. In addition, better methods are needed to sensitively monitor progression of disease and therapeutic efficacy. Therefore, considerable research has focused on characterizing biomarkers that can identify the disease early as well as accurately monitor disease progression. miRNA offer a unique opportunity for biomarker development. Here, we review research focused on characterizing miRNA as potential biomarkers and as a treatment for disease.

The Three Paralogous MicroRNA Clusters in Development and Disease, miR-17-92, miR-106a-363, and miR-106b-25

MicroRNAs (miRNAs) form a class of noncoding RNA genes whose products are small single-stranded RNAs that are involved in the regulation of translation and degradation of mRNAs. There is a fine balance between deregulation of normal developmental programs and tumor genesis. An increasing body of evidence suggests that altered expression of miRNAs is entailed in the pathogenesis of human cancers. Studies in mouse and human cells have identified the miR-17-92 cluster as a potential oncogene. The miR-17-92 cluster is often amplified or overexpressed in human cancers and has recently emerged as the prototypical oncogenic polycistron miRNA. The functional analysis of miR-17-92 is intricate by the existence of two paralogues: miR-106a-363 and miR-106b-25. During early evolution of vertebrates, it is likely that the three clusters commenced via a series of duplication and deletion occurrences. As miR-106a-363 and miR-106b-25 contain miRNAs that are very similar, and in some cases identical, to those encoded by miR-17-92, it is feasible that they regulate a similar set of genes and have overlapping functions. Further understanding of these three clusters and their functions will increase our knowledge about cancer progression. The present review discusses the characteristics and functions of these three miRNA clusters.

miR-106b is overexpressed in medulloblastomas and interacts directly with PTEN

AIMS

MicroRNAs (miRNAs) are an abundant group of small non-coding RNAs that have been implicated in tumorigenesis. They regulate expression of target genes by complementary base pairing. The purposes of this study were to delineate miR-106b expression in medulloblastoma (MB) and to explore its functional contributions to MB pathogenesis.

METHODS

We analysed expression of miR-106b in 32 MB samples by quantitative RT-PCR. We applied gain- and loss-of-function strategies to delineate the functional roles of miR-106b in MB. Luciferase reporter assay was conducted to confirm target gene of miR-106b.

RESULTS

Expression of miR-106b was overexpressed in MB, and was significantly associated with its host gene MCM7 (P = 0.020). Transfection of miR-106b inhibitor in MB cell lines markedly reduced cell proliferation, migration and invasion potential, and tumour sphere formation. Cell cycle analysis indicated that miR-106b inhibition induced G1 arrest and apoptosis. The cell cycle regulators, p21 and cyclin D1, and apoptotic marker cleaved PARP were differentially expressed in miR-106b inhibitor-transfected cells. PTEN was identified as a direct target gene of miR-106b. Luciferase reporter assay confirmed miR-106b directly interacted with the 3' UTR of PTEN. We found miR-106b directly targeted PTEN at transcriptional and translational levels. Immunohistochemistry revealed a trend between PTEN and miR-106b in MB tumours (P = 0.07).

CONCLUSIONS

These data suggested the upregulation of miR-106b in MB and the involvement of miR-106b in MB biology.

The regulatory and predictive functions of miR-17 and miR-92 families on cisplatin resistance of non-small cell lung cancer

Background

Chemotherapy is an important therapeutic approach for non-small cell lung cancer (NSCLC). However, a successful long-term treatment can be prevented by the occurring of chemotherapy resistance frequently, and the molecular mechanisms of chemotherapy resistance in NSCLC remain unclear. In this study, abnormal expressions of miR-17 and miR-92 families are observed in cisplatin-resistant cells, suggesting that miR-17 and miR-92 families are involved in the regulation of cisplatin resistance in NSCLC.

Methods

miRNA microarray shows that miR-17 and miR-92 families are all down-regulated in cisplatin-resistant A549/DDP cells compared with cisplatin-sensitive A549 cells. The aim of this study is to investigate the regulatory functions of miR-17 and miR-92 families on the formation of cisplatin resistance and the predictive functions of them as biomarkers of platinum-based chemotherapy resistance in NSCLC.

Results

The low expressions of miR-17 and miR-92 families can maintain cisplatin resistance through the regulation of CDKN1A and RAD21. As a result of high expressions of CDKN1A and RAD21, the inhibition of DNA synthesis and the repair of DNA damage are achieved and these may be two major contributing factors to cisplatin resistance. Moreover, we demonstrate that the expressions of miR-17 and miR-92 families in NSCLC tissues are significantly associated with platinum-based chemotherapy response.

Conclusion

Our study indicates that miR-17 and miR-92 families play important roles in cisplatin resistance and can be used as potential biomarkers for better predicting the clinical response to platinum-based chemotherapy in NSCLC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1713-z) contains supplementary material, which is available to authorized users.

ncRNA-regulated immune response and its role in inflammatory lung diseases

Despite the greatly expanded knowledge on the regulation of immune response by protein molecules, there is increasing understanding that noncoding RNAs (ncRNAs) are also an integral component of this regulatory network. Abnormal immune response serves a central role in the initiation, progression, and exacerbation of inflammatory lung diseases, such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, and acute respiratory distress syndrome/acute lung injury. Dysregulation of ncRNAs has been linked to various immunopathologies. In this review, we highlighted the role of ncRNAs in the regulation of innate and adaptive immunity and summarized recent findings that ncRNAs participate in the pathogenesis of inflammatory lung diseases via their regulation of pulmonary immunity. We also discussed therapeutic potentials for targeting ncRNAs to treat these lung disorders.

miRNA therapeutics: a new class of drugs with potential therapeutic applications in the heart

miRNAs are small non-coding RNAs (ncRNAs), which regulate gene expression. Here, the authors describe the contribution of miRNAs to cardiac biology and disease. They discuss various strategies for manipulating miRNA activity including antisense oligonucleotides (antimiRs, blockmiRs), mimics, miRNA sponges, Tough Decoys and miRNA mowers. They review developments in chemistries (e.g., locked nucleic acid) and modifications (sugar, 'ZEN', peptide nucleic acids) and miRNA delivery tools (viral vectors, liposomes, nanoparticles, pHLIP). They summarize potential miRNA therapeutic targets for heart disease based on preclinical studies. Finally, the authors review current progress of miRNA therapeutics in clinical development for HCV and cancer, and discuss challenges that will need to be overcome for similar therapies to enter the clinic for patients with cardiac disease.

Insights into Regulation of the miR-17-92 Cluster of miRNAs in Cancer

Overexpression of the miR-17-92 cluster is a key oncogenic event in various cancer types. The oncogenic effect of the miR-17-92 cluster is enhanced by cooperation between its members in targeting tumor-suppressive proteins and pathways such as PTEN and TGFβ signaling. However, in the case of miR-19a and miR-19b, these have been shown to have a preponderant role in the cluster’s oncogenicity. Important studies have revealed the influence of the Myc proto-oncogene family in the transcriptional regulation of miR-17-92. Recent findings show that other oncogenic signaling pathways, such as those of Notch and Sonic Hedgehog, activate miR-17-92 in cancer. Notwithstanding, another layer of complexity has been added by the influence of the relevant primary miR-17-92 tertiary structure during processing to mature miRNA. In this review, we attempt to integrate current transcriptional and post-transcriptional knowledge to enhance our global understanding of the coordinated up-regulation of miR-17-92 in cancer.

ABCG2 Transporter Expression Impacts Group 3 Medulloblastoma Response to Chemotherapy

While a small number of plasma membrane ABC transporters can export chemotherapeutic drugs and confer drug resistance, it is unknown whether these transporters are expressed or functional in less therapeutically tractable cancers such as Group 3 (G3) medulloblastoma. Herein we show that among this class of drug transporters, only ABCG2 was expressed at highly increased levels in human G3 medulloblastoma and a mouse model of this disease. In the mouse model, Abcg2 protein was expressed at the plasma membrane where it functioned as expected on the basis of export of prototypical substrates. By screening ABC substrates against mouse G3 medulloblastoma tumorspheres in vitro, we found that Abcg2 inhibition could potentiate responses to the clinically used drug topotecan, producing a more than 9-fold suppression of cell proliferation. Extended studies in vivo in this model confirmed that Abcg2 inhibition was sufficient to enhance antiproliferative responses to topotecan, producing a significant survival advantage compared with subjects treated with topotecan alone. Our findings offer a preclinical proof of concept for blockade of ABCG2 transporter activity as a strategy to empower chemotherapeutic responses in G3 medulloblastoma.

Inhibition of Gastric Tumor Cell Growth Using Seed-targeting LNA as Specific, Long-lasting MicroRNA Inhibitors

MicroRNAs regulate eukaryotic gene expression upon pairing onto target mRNAs. This targeting is influenced by the complementarity between the microRNA “seed” sequence at its 5′ end and the seed-matching sequences in the mRNA. Here, we assess the efficiency and specificity of 8-mer locked nucleic acid (LNA)-modified oligonucleotides raised against the seeds of miR-372 and miR-373, two embryonic stem cell-specific microRNAs prominently expressed in the human gastric adenocarcinoma AGS cell line. Provided that the pairing is perfect over all the eight nucleotides of the seed and starts at nucleotide 2 or 1 at the microRNA 5′ end, these short LNAs inhibit miR-372/373 functions and derepress their common target, the cell cycle regulator LATS2. They decrease cell proliferation in vitro upon either transfection at nanomolar concentrations or unassisted delivery at micromolar concentrations. Subcutaneously delivered LNAs reduce tumor growth of AGS xenografts in mice, upon formation of a stable, specific heteroduplex with the targeted miR-372 and -373 and LATS2 upregulation. Their therapeutic potential is confirmed in fast-growing, miR-372-positive, primary human gastric adenocarcinoma xenografts in mice. Thus, microRNA silencing by 8-mer seed-targeting LNAs appears a valuable approach for both loss-of-function studies aimed at elucidating microRNA functions and for microRNA-based therapeutic strategies.

MicroRNA-17-92 controls T-cell responses in graft-versus-host disease and leukemia relapse in mice

MicroRNAs (miRs) play important roles in orchestrating many aspects of the immune response. The miR-17-92 cluster, which encodes 6 miRs including 17, 18a, 19a, 20a, 19b-1, and 92-1, is among the best characterized of these miRs. The miR-17-92 cluster has been shown to regulate a variety of immune responses including infection, tumor, and autoimmunity, but the role of this cluster in T-cell response to alloantigens has not been previously explored. By using major histocompatibility complex (MHC)-matched, -mismatched, and haploidentical murine models of allogeneic bone marrow transplantation (allo-BMT), we demonstrate that the expression of miR-17-92 on donor T cells is essential for the induction of graft-versus-host disease (GVHD), but dispensable for the graft-versus-leukemia (GVL) effect. The miR-17-92 plays a major role in promoting CD4 T-cell activation, proliferation, survival, and Th1 differentiation, while inhibiting Th2 and iTreg differentiation. Alternatively, miR-17-92 may promote migration of CD8 T cells to GVHD target organs, but has minimal impact on CD8 T-cell proliferation, survival, or cytolytic function, which could contribute to the preserved GVL effect mediated by T cells deficient for miR-17-92. Furthermore, we evaluated a translational approach and found that systemic administration of antagomir to block miR-17 or miR-19b in this cluster significantly inhibited alloreactive T-cell expansion and interferon-γ (IFNγ) production, and prolonged the survival in recipients afflicted with GVHD while preserving the GVL effect. Taken together, the current work provides a strong rationale and demonstrates the feasibility to target miR-17-92 for the control of GVHD while preserving GVL activity after allo-BMT.

Dicer Is Required for Normal Cerebellar Development and to Restrain Medulloblastoma Formation

Dicer, a ribonuclease III enzyme, is required for the maturation of microRNAs. To assess its role in cerebellar and medulloblastoma development, we genetically deleted Dicer in Nestin-positive neural progenitors and in mice lacking one copy for the Sonic Hedgehog receptor, Patched 1. We found that conditional loss of Dicer in mouse neural progenitors induced massive Trp53-independent apoptosis in all proliferative zones of the brain and decreased proliferation of cerebellar granule progenitors at embryonic day 15.5 leading to abnormal cerebellar development and perinatal lethality. Loss of one copy of Dicer significantly accelerated the formation of mouse medulloblastoma of the Sonic Hedgehog subgroup in Patched1-heterozygous mice. We conclude that Dicer is required for proper cerebellar development, and to restrain medulloblastoma formation.

Short antisense-locked nucleic acids (all-LNAs) correct alternative splicing abnormalities in myotonic dystrophy

Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder caused by expansion of CTG triplet repeats in 3′-untranslated region of DMPK gene. The pathomechanism of DM1 is driven by accumulation of toxic transcripts containing expanded CUG repeats (CUG^exp) in nuclear foci which sequester several factors regulating RNA metabolism, such as Muscleblind-like proteins (MBNLs). In this work, we utilized very short chemically modified antisense oligonucleotides composed exclusively of locked nucleic acids (all-LNAs) complementary to CUG repeats, as potential therapeutic agents against DM1. Our in vitro data demonstrated that very short, 8- or 10-unit all-LNAs effectively bound the CUG repeat RNA and prevented the formation of CUG^exp/MBNL complexes. In proliferating DM1 cells as well as in skeletal muscles of DM1 mouse model the all-LNAs induced the reduction of the number and size of CUG^exp foci and corrected MBNL-sensitive alternative splicing defects with high efficacy and specificity. The all-LNAs had low impact on the cellular level of CUG^exp-containing transcripts and did not affect the expression of other transcripts with short CUG repeats. Our data strongly indicate that short all-LNAs complementary to CUG repeats are a promising therapeutic tool against DM1.

Sphingosine-1-phosphate induces the migration of thyroid follicular carcinoma cells through the microRNA-17/PTK6/ERK1/2 pathway

Sphingosine-1-phosphate (S1P) is a bioactive lipid known to play a role in tumorigenesis and cancer progression. However, the molecular mechanisms of S1P regulated migration of papillary thyroid cancer cells are still unknown. In this study, we showed that S1P induced PTK6 mRNA and protein expression in two thyroid follicular cancer cell lines (ML-1 and FTC-133). Further studies demonstrated that induced PTK6 and its downstream signal component (ERK1/2) are involved in S1P-induced migration. Upon investigating the mechanisms behind this event, we found that miR-17 inhibited the expression of PTK6 through direct binding to its 3’-UTR. Through overexpression and knockdown studies, we found that miR-17 can significantly inhibit S1P-induced migration in thyroid follicular cancer cells. Interestingly, overexpression or knockdown of PTK6 or ERK1/2 effectively removed the inhibition of S1P-induced migration by miR-17. Furthermore, we showed that S1P decreased miR-17 expression levels. Meanwhile, in papillary thyroid cancers, miR-17 is downregulated and negatively associated with clinical staging, whereas PTK6 is upregulated and positively associated with clinical stages. Collectively, our work defines a novel signaling pathway implicated in the control of thyroid cancer migration.

MicroRNAs in pediatric central nervous system embryonal neoplasms: the known unknown

MicroRNAs (miRNAs) are endogenous short non-coding RNAs that repress post-transcriptional regulation of gene expression, while embryonal central nervous system tumors are the foremost cause of mortality in children suffering from a neoplasm. MiRNAs and their regulatory mechanisms are new to understand, while pediatric CNS tumors are difficult to comprehend. Therefore, identification of the link between them composes a major scientific challenge. The present study, reviewed the current knowledge on the role of miRNA in pediatric CNS embryonal tumors, attempting to collect the existing information in one piece of work that could ideally be used as a guide for future reference and research.

MicroRNA-19a functions as an oncogenic microRNA in non-small cell lung cancer by targeting the suppressor of cytokine signaling 1 and mediating STAT3 activation

MicroRNA‑19a (miR‑19a) has been found to be overexpressed in lung cancers. However, the underlying molecular mechanisms of miR‑19a in tumorigenesis and the development of lung cancer remain poorly understood. In the present study, we aimed to delineate the role and mechanisms of action of miR‑19a in non‑small cell lung cancer (NSCLC). miR‑19a was found to be overexpressed in both NSCLC tumor tissues and cell lines, as shown by RT-PCR. The enforced expression of miR‑19a by transfection with miR-19a mimics significantly enhanced cell growth and viability, cell invasion and the migration of NSCLC cells, as shown by cell invasion and migration assays, and promoted the growth of xenograft tumors in a mouse xenograft tumor model. Conversely, the inhibition of miR‑19a by transfection of the cells with miR‑19a inhibitor displayed the opposite effects. More importantly, we found that miR‑19a directly interacted with the 3'‑untranslated region (3'‑UTR) of the suppressor of cytokine signaling 1 (SOCS1) by dual‑luciferase reporter assay. miR‑19a was found to be capable of regulating the expression of SOCS1 in NSCLC cells. Thus, by modulating SOCS1 expression, miR‑19a regulated the expression of the signal transducer and activator of transcription 3 (STAT3). Taken together, our data provide a possible underlying mechanism of action of miR‑19a in the development of NSCLC and suggest that miR‑19a may be a novel and promising target for therapeutic intervention in NSCLC.

Small molecule compounds targeting miRNAs for cancer therapy

One of the most fascinating discoveries in molecular oncology has been that cancer represents a disease in which genetic alterations in protein-coding, but also in non-coding genes complement each other. MicroRNAs (miRNAs) are a type of non-coding RNA (ncRNA) transcripts that can regulate gene expression primarily by disrupting messenger RNA (mRNA) translation and/or stability, or alternatively by modulating the transcription of target mRNAs. For the last decade, miRNAs have shown to be pivotal characters of every single one of the cancer hallmarks. Profiling studies have proven the significance of identifying over-expressed miRNAs (oncomiRs) causative of the activation of oncogenic pathways that lead to malignancy. Due to their crucial role in cancer, it has become a challenge to develop efficient miRNA-inhibiting strategies such as antagomiRs, locked nucleic acids or antisense oligonucleotides. However, to this date, the accessible delivery agents and their pharmacokinetic/pharmacodynamic properties are not ideal. Thus there is an urgent, unmet need to develop miRNA-based inhibitory therapeutics. Herein we present a novel therapeutic strategy that is only at the tip of the iceberg: the use of small molecule inhibitors to target specific miRNAs (SMIRs). Furthermore we describe several high-throughput techniques to screen for SMIRs both in vitro and in silico. Finally we take you through the journey that has led to discovering the handful of SMIRs that have been validated to this date.

Molecular signatures of mRNAs and miRNAs as prognostic biomarkers in pancreatobiliary and intestinal types of periampullary adenocarcinomas

Periampullary adenocarcinomas include four anatomical sites of origin (the pancreatic duct, bile duct, ampulla and duodenum) and most of them fall into two histological subgroups (pancreatobiliary and intestinal). Determining the exact origin of the tumor is sometimes difficult, due to overlapping histopathological characteristics. The prognosis depends on the histological subtype, as well as on the anatomical site of origin, the former being the more important. The molecular basis for these differences in prognosis is poorly understood. Whole-genome analyses were used to investigate the association between molecular tumor profiles, pathogenesis and prognosis. A total of 85 periampullary adenocarcinomas were characterized by mRNA and miRNA expressions profiling. Molecular profiles of the tumors from the different anatomical sites of origin as well as of the different histological subtypes were compared. Differentially expressed mRNAs and miRNAs between the two histopathological subtypes were linked to specific molecular pathways. Six miRNA families were downregulated and four were upregulated in the pancreatobiliary type as compared to the intestinal type (P < 0.05). miRNAs and mRNAs associated with improved overall and recurrence free survival for the two histopathological subtypes were identified. For the pancreatobiliary type the genes ATM, PTEN, RB1 and the miRNAs miR-592 and miR-497, and for the intestinal type the genes PDPK1, PIK3R2, G6PC and the miRNAs miR-127-3p, miR-377* were linked to enriched pathways and identified as prognostic markers. The molecular signatures identified may in the future guide the clinicians in the therapeutic decision making to an individualized treatment, if confirmed in other larger datasets.

Blocking the maturation of OncomiRNAs using pri-miRNA-17∼92 aptamer in retinoblastoma

The miR-17∼92. or oncomiR-1, cluster encodes oncogenic microRNAs (miRNAs), and it also promotes retinoblastoma (RB) tumor formation. Antagomir and miRNA mimics based approaches are widely tried against oncogenic and tumor suppressive miRNAs. Other methods for targeting cancer related miRNAs are still under development. In the current study, we focused on the pri-miRNA-17∼92 aptamer (pri-apt), which can potentially replace the mix of five antagomirs by one aptamer that function to abrogate the maturation of miR-17, miR-18a, and miR-19b (P<0.05) for targeting RB. We used RB cell lines WERI-Rb1 and Y79 as an in vitro model. Cellular changes upon transfecting the pri-apt led to S-phase arrest in WERI-Rb1 cells and onset of apoptosis in both Y79 and WERI-Rb1 cell lines. There was increased cytotoxicity as measured by lactate dehydrogenase activity in pri-apt treated Y79 cells (P<0.05), and significant inhibition of cell proliferation was observed in both of the cell lines. Thus we showed the antiproliferative property of pri-apt in RB cell lines, which can be readily modified by developing appropriate vectors for the delivery of the aptamer specifically to cancer cells.

Antitumor mechanisms when pRb and p53 are genetically inactivated

pRb and p53 are the two major tumor suppressors. Their inactivation is frequent when cancers develop and their reactivation is rationale of most cancer therapeutics. When pRb and p53 are genetically inactivated, cells irreparably lose the antitumor mechanisms afforded by them. Cancer genome studies document recurrent genetic inactivation of RB1 and TP53, and the inactivation becomes more frequent in more advanced cancers. These findings may explain why more advanced cancers are more likely to resist current therapies. Finding successful treatments for more advanced and multi-therapy resistant cancers will depend on finding antitumor mechanisms that remain effective when pRb and p53 are genetically inactivated. Here, we review studies that have begun to make progress in this direction.

MicroRNA signatures as biomarkers and therapeutic target for CNS embryonal tumors: the pros and the cons

Embryonal tumors of the central nervous system represent a heterogeneous group of childhood cancers with an unknown pathogenesis; diagnosis, on the basis of histological appearance alone, is controversial and patients’ response to therapy is difficult to predict. They encompass medulloblastoma, atypical teratoid/rhabdoid tumors and a group of primitive neuroectodermal tumors. All are aggressive tumors with the tendency to disseminate throughout the central nervous system. The large amount of genomic and molecular data generated over the last 5–10 years encourages optimism that new molecular targets will soon improve outcomes. Recent neurobiological studies have uncovered the key role of microRNAs (miRNAs) in embryonal tumors biology and their potential use as biomarkers is increasingly being recognized and investigated. However the successful use of microRNAs as reliable biomarkers for the detection and management of pediatric brain tumors represents a substantial challenge. This review debates the importance of miRNAs in the biology of central nervous systemembryonal tumors focusing on medulloblastoma and atypical teratoid/rhabdoid tumors and highlights the advantages as well as the limitations of their prospective application as biomarkers and candidates for molecular therapeutic targets.