Frequent amplification of a chr19q13.41 microRNA polycistron in aggressive primitive neuroectodermal brain tumors

Embryonal brain tumors

Embryonal brain tumors are a heterogeneous group of neoplasms that primarily occur in infants and young children. They are highly cellular tumors with brisk mitotic activity, and they share a propensity for dissemination throughout the neuroaxis. Emerging molecular data enable improved diagnostic and prognostic discrimination for these tumors. Because of their aggressive potential, they are treated similarly with multimodality therapy including maximal safe resection, chemotherapy, and age- and risk-adapted radiotherapy. Craniospinal irradiation is commonly used in the treatment of these patients, especially in those older than 3 years. Because proton therapy allows for increased sparing of the anterior structures in craniospinal irradiation, there is a particular interest in using proton therapy to treat these young patients. For very young patients treated with focal fields only, proton therapy also decreases unnecessary radiation exposure to uninvolved intracranial structures. It is hoped that the use of proton therapy for these vulnerable patients will translate into decreased long-term neurocognitive, endocrine, vascular, and developmental effects, in addition to a decreased risk of second malignancies. This review describes the role of radiation in general and proton therapy in particular for the treatment of medulloblastoma, central nervous system primitive neuroectodermal tumors, atypical teratoid/rhabdoid tumors, and the recently described embryonal tumor with multilayered rosettes.

The academic productivity and impact of the University of Toronto Neurosurgery Program as assessed by manuscripts published and their number of citations

OBJECT

Recent works have assessed academic output across neurosurgical programs using various analyses of accumulated citations as a proxy for academic activity and productivity. These assessments have emphasized North American neurosurgical training centers and have largely excluded centers outside the United States. Because of the long tradition and level of academic activity in neurosurgery at the University of Toronto, the authors sought to compare that program's publication and citation metrics with those of established programs in the US as documented in the literature. So as to not rely on historical achievements that may be of less relevance, they focused on recent works, that is, those published in the most recent complete 5-year period.

METHODS

The authors sought to make their data comparable to existing published data from other programs. To this end, they compiled a list of published papers by neurosurgical faculty at the University of Toronto for the period from 2009 through 2013 using the Scopus database. Individual author names were disambiguated; the total numbers of papers and citations were compiled on a yearly basis. They computed a number of indices, including the ih(5)-index (i.e., the number of citations the papers received over a 5-year period), the summed h-index of the current faculty over time, and a number of secondary measures, including the ig(5), ie(5), and i10(5)-indices. They also determined the impact of individual authors in driving the results using Gini coefficients. To address the issue of author ambiguity, which can be problematic in multicenter bibliometric analyses, they have provided a source dataset used to determine the ih(5) index for the Toronto program.

RESULTS

The University of Toronto Neurosurgery Program had approximately 29 full-time surgically active faculty per year (not including nonneurosurgical faculty) in the 5-year period from 2009 to 2013. These faculty published a total of 1217 papers in these 5 years. The total number of citations from these papers was 13,434. The ih(5)-index at the University of Toronto was 50.

CONCLUSIONS

On the basis of comparison with published bibliometric data of US programs, the University of Toronto ranks first in terms of number of publications, number of citations, and ih(5)-index among neurosurgical programs in North America and most likely in the world.

Next-generation (epi)genetic drivers of childhood brain tumours and the outlook for targeted therapies

Arguably, nowhere has there been a greater advance in our understanding of biological mechanisms and potential translational targets during the next-generation sequencing era than in paediatric brain tumours. The so-called omics revolution, enabled by high-throughput sequencing, has empowered large consortia and independent groups alike to make major genetic discoveries, from dominant-negative histone mutations and hijacking of distal enhancer elements, to new oncogenic gene fusions and aberrantly active gene expression. Epigenetic deregulation has also been revealed as a common theme across several tumour subtypes. This Review focuses on key findings that have been transforming the landscape of paediatric neuro-oncology research and how these results are opening new avenues towards potential therapeutic translation.

Clinicopathology of diffuse intrinsic pontine glioma and its redefined genomic and epigenomic landscape

Diffuse intrinsic pontine glioma (DIPG) is one of the most lethal pediatric central nervous system (CNS) cancers. Recently, a surge in molecular studies of DIPG has occurred, in large part due to the increased availability of tumor tissue through donation of post-mortem specimens. These new discoveries have established DIPGs as biologically distinct from adult gliomas, harboring unique genomic aberrations. Mutations in histone encoding genes are shown to be associated with >70% of DIPG cases. However, the exact molecular mechanisms of the tumorigenicity of these mutations remain elusive. Understanding the driving mutations and genomic landscape of DIPGs can now guide the development of targeted therapies for this incurable childhood cancer.

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.

The Function of TrophomiRs and Other MicroRNAs in the Human Placenta

In eutherian organisms, the placenta interfaces the fetal and maternal environments. Located at the placental villous surface, in direct contact with maternal blood, is the trophoblast layer, which mediates the crucial maternal-fetal exchange of gases, nutrients, and waste products, produces hormones that support the pregnancy, and provides immunologic defense. Discovery of microRNAs (miRNAs) and their role in development, differentiation, and homeostatic resilience has increased our understanding of genomic and epigenomic networks that regulate placental function. Moreover, unique miRNA species, which are expressed by human trophoblasts and are termed "trophomiRs," may show specialized functions during normal and pathological pregnancies. Placental miRNAs, packaged within exosomes and other vesicles or bound in protein complexes, are capable of communicating distinctive signals to maternal and/or fetal tissues. Additional research may usher in the use of circulating miRNAs as pregnancy-related disease biomarkers, providing new diagnostic and therapeutic options during pregnancy.

MicroRNA deregulation in parathyroid tumours suggests an embryonic signature

Primary hyperparathyroidism is a common endocrine disorder caused by abnormal tumour parathyroid cell proliferation. Parathyroid tumours show a great variability both in clinical features, such as the severity of PTH secretion, the rate and the pattern of cell proliferation, and genetic background. Studies aiming to develop new diagnostic markers and therapeutic approaches need a deeper definition of this variability. Dysregulation of microRNAs (miRNAs) has been shown to play an essential role in the development and progression of cancer. MiRNAs are small noncoding RNAs that inhibit the translation and stability of messenger RNAs (mRNAs). Here, data about the miRNA expression pattern in parathyroid normal and tumour glands were reviewed. Though available data in parathyroid tumours are very limited, the expression pattern of a subset of specific miRNAs clearly discriminated parathyroid carcinomas from normal parathyroid glands and, more clinically relevant, from parathyroid adenomas. Investigation showed that parathyroid tumours were characterized by an embryonic expression pattern of miRNAs such as miR-296, or the miRNA clusters C19MC and miR-371-3, typically in stem cells committed to differentiation or during human embryonic development, respectively. Further, miRNA profiles were correlated with tumour aggressive behaviour. Moreover, the interaction with the oncosuppressor menin suggests that miRNAs might modulate the function of the known oncosuppressors or oncogenes involved in parathyroid tumourigenesis and thus overseeing the tumour phenotype. In conclusion, miRNAs might provide new diagnostic markers and new therapeutic approaches by developing molecular miRNA-targeted therapies for the cure of parathyroid tumours, whose unique option is surgery.

Tissue elasticity regulated tumor gene expression: implication for diagnostic biomarkers of primitive neuroectodermal tumor

Background

The tumor microenvironment consists of both physical and chemical factors. Tissue elasticity is one physical factor contributing to the microenvironment of tumor cells. To test the importance of tissue elasticity in cell culture, primitive neuroectodermal tumor (PNET) stem cells were cultured on soft polyacrylamide (PAA) hydrogel plates that mimics the elasticity of brain tissue compared with PNET on standard polystyrene (PS) plates. We report the molecular profiles of PNET grown on either PAA or PS.

Methodology/Principal Findings

A whole-genome microarray profile of transcriptional expression between the two culture conditions was performed as a way to probe effects of substrate on cell behavior in culture. The results showed more genes downregulated on PAA compared to PS. This led us to propose microRNA (miRNA) silencing as a potential mechanism for downregulation. Bioinformatic analysis predicted a greater number of miRNA binding sites from the 3' UTR of downregulated genes and identified as specific miRNA binding sites that were enriched when cells were grown on PAA—this supports the hypothesis that tissue elasticity plays a role in influencing miRNA expression. Thus, Dicer was examined to determine if miRNA processing was affected by tissue elasticity. Dicer genes were downregulated on PAA and had multiple predicted miRNA binding sites in its 3' UTR that matched the miRNA binding sites found enriched on PAA. Many differentially regulated genes were found to be present on PS but downregulated on PAA were mapped onto intron sequences. This suggests expression of alternative polyadenylation sites within intron regions that provide alternative 3' UTRs and alternative miRNA binding sites. This results in tissue specific transcriptional downregulation of mRNA in humans by miRNA. We propose a mechanism, driven by the physical characteristics of the microenvironment by which downregulation of genes occur. We found that tissue elasticity-mediated cytokines (TGFβ2 and TNFα) signaling affect expression of ECM proteins.

Conclusions

Our results suggest that tissue elasticity plays important roles in miRNA expression, which, in turn, regulate tumor growth or tumorigenicity.

The role of trophoblastic microRNAs in placental viral infection

During the past decade, various types of small non-coding RNAs were found to be expressed in all kingdoms and phyla of life. Intense research efforts have begun to shed light on their biological functions, although much remains to be determined in order to fully characterize their scope of biological action. Typically, small RNAs provide sequence specificity to a protein complex that is driven to silence a long target RNA. MicroRNAs (miRNAs) are small RNAs that are coded in the genome of most eukaryotes, and contribute to the cellular identity by regulating cell-specific gene networks by translational repression or degradation of mRNA. These effects commonly fine-tune gene expression associated with developmental or environmental cues. Different cell types can be characterized by their distinctive cellular miRNA landscape. The human placenta expresses a unique set of miRNAs, a high proportion of which is derived from a large cluster located on chromosome 19, (termed chromosome 19 miRNA cluster, or C19MC). Interestingly, a fraction of these placenta-enriched miRNAs are released to the extracellular environment through exosomes that were recently found to induce an antiviral immunity. In this review, we explore relevant placental viral infections and discuss the antiviral role of exosome-packaged placental C19MC miRNAs in this context.

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.

Epigenetic alterations in cancer and personalized cancer treatment

ABSTRACT 

Based on the pivotal importance of epigenetics for transcription regulation, it is not surprising that cancer is characterized by several epigenetic abnormalities. Conversely to genetic alterations, epigenetic changes are not permanent, thus represent opportunities for therapeutic strategies designed to reverse transcriptional abnormalities, and cancer is the first disease in which epigenetic therapies with chromatin remodeling agents were introduced. The role of miRNAs in gene regulation supports their potential as innovative therapeutic strategy. Recent evidences have proven that the environment can profoundly influence the epigenome: diet, smoking and alcohol consumption can negatively impact the expression profile. Given the plasticity of epigenetic marks, it is challenging the idea that the epigenetic alterations are ‘druggable’ sites using specific food components.

Practical molecular pathology and histopathology of embryonal tumors

There have been significant improvements in understanding of embryonal tumors of the central nervous system (CNS) in recent years. These advances are most likely to influence the diagnostic algorithms and methodology currently proposed by the World Health Organization (WHO) classification scheme. Molecular evidence suggests that the tumors presumed to be specific entities within the CNS/primitive neuroectodermal tumors spectrum are likely to be reclassified. All these developments compel reassessing current status and expectations from the upcoming WHO classification efforts. This review provides a synopsis of current developments and a practical algorithm for the work-up of these tumors in practice.

Non-coding RNAs: biological functions and applications

Analyses of the international human genome sequencing results in 2004 converged to a consensual number of ~20,000 protein-coding genes, spanning over <2% of the total genomic sequence. Therefore, the developmental and physiological complexity of human beings remains unaccounted if viewed only in terms of the number of protein-coding genes; the epigenetic influences involving chromatin remodelling and RNA interference and alternative precursor messenger RNA splicing of functional protein-coding transcripts as well as post-translational modifications of proteins increase the diversity and the functionality of the proteome and likely explain the increased complexity. In addition, there has been an explosion of research addressing possible functional roles for the other 98% of the human genome that does not encode proteins. In fact, >90% of the human genome is likely to be transcribed yielding a complex network of overlapping transcripts that include tens of thousands of long RNAs with little or no protein forming capacity; they are collectively called non-coding RNA. This review highlights the fundamental concepts of biological roles of non-coding RNA and their importance in regulation of cellular physiology under disease conditions like cancer.

MicroRNA-520g induces epithelial-mesenchymal transition and promotes metastasis of hepatocellular carcinoma by targeting SMAD7

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Aberrant expression of miRNAs contributes to HCC development. Here, we observed elevated miR-520g expression in tumor samples from HCC patients with relapse and metastasis, and this high miR-520g expression was correlated with poor survival. Through gain- and loss-of-function studies, miR-520g was demonstrated to facilitate HCC cell migration, invasion and epithelial-mesenchymal transition (EMT). SMAD7 was identified as a direct target of miR-520g. Accordingly, we conclude that high miR-520g expression promotes HCC cell mobility and EMT by targeting SMAD7, and this is correlated with reduced survival in HCC patients.

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.

Brain neoplasms and coagulation-lessons from heterogeneity

The coagulation system constitutes an important facet of the unique vascular microenvironment in which primary and metastatic brain tumors evolve and progress. While brain tumor cells express tissue factor (TF) and other effectors of the coagulation system (coagulome), their propensity to induce local and peripheral thrombosis is highly diverse, most dramatic in the case of glioblastoma multiforme (GBM), and less obvious in pediatric tumors. While the immediate medical needs often frame the discussion on current clinical challenges, the coagulation pathway may contribute to brain tumor progression through subtle, context-dependent, and non-coagulant effects, such as induction of inflammation, angiogenesis, or by responding to iatrogenic insults (e.g. surgery). In this regard, the emerging molecular diversity of brain tumor suptypes (e.g. in glioma and medulloblastoma) highlights the link between oncogenic pathways and the tumor repertoire of coagulation system regulators (coagulome). This relationship may influence the mechanisms of spontaneous and therapeutically provoked tumor cell interactions with the coagulation system as a whole. Indeed, oncogenes (EGFR, MET) and tumor suppressors (PTEN, TP53) may alter the expression, activity, and vesicular release of tissue factor (TF), and cause other changes. Conversely, the coagulant microenvironment may also influence the molecular evolution of brain tumor cells through selective and instructive cues. We suggest that effective targeting of the coagulation system in brain tumors should be explored through molecular stratification, stage-specific analysis, and more personalized approaches including thromboprophylaxis and adjuvant treatment aimed at improvement of patient survival.

DNMTs as potential therapeutic targets in high-risk pediatric embryonal brain tumors

Malignant brain tumors, which are the leading cause of cancer-related morbidity and mortality in children, span a wide spectrum of diseases with distinct clinical phenotypes but may share remarkably similar morphologic features. Until recently, few molecular markers of childhood brain tumors have been identified, which has limited therapeutic advances. Recent global genomic studies have enabled robust molecular classification of childhood brain tumors and the identification and consolidation of rare, seemingly disparate clinical entities. It is now increasingly evident that deregulation of epigenetic processes contributes substantially to heterogeneity in tumor phenotypes and comprise significant drivers of cancer initiation and progression. Specifically, DNA hypermethylation and silencing of critical tumor suppressor genes by DNA methyltransferases (DNMT) has emerged as an important and fundamental mechanism in brain tumor pathogenesis. These observations have been underscored by the recent discovery of TTYH1-C19MC gene fusions in an aggressive pediatric embryonal brain tumor, which results in deregulation and increased expression of a neural-specific DNMT3B isoform in C19MC-associated brain tumors. Our observations that pharmacological inhibitors of DNMTs and histone deacetylases significantly inhibit growth of cells derived from C19MC-associated tumors indicate targeting of epigenomic modifiers as a novel therapeutic approach for these highly treatment-resistant tumors.

CNS-PNETs with C19MC amplification and/or LIN28 expression comprise a distinct histogenetic diagnostic and therapeutic entity

Amplification of the C19MC oncogenic miRNA cluster and high LIN28 expression has been linked to a distinctly aggressive group of cerebral CNS-PNETs (group 1 CNS-PNETs) arising in young children. In this study, we sought to evaluate the diagnostic specificity of C19MC and LIN28, and the clinical and biological spectra of C19MC amplified and/or LIN28+ CNS-PNETs. We interrogated 450 pediatric brain tumors using FISH and IHC analyses and demonstrate that C19MC alteration is restricted to a sub-group of CNS-PNETs with high LIN28 expression; however, LIN28 immunopositivity was not exclusive to CNS-PNETs but was also detected in a proportion of other malignant pediatric brain tumors including rhabdoid brain tumors and malignant gliomas. C19MC amplified/LIN28+ group 1 CNS-PNETs arose predominantly in children <4 years old; a majority arose in the cerebrum but 24 % (13/54) of tumors had extra-cerebral origins. Notably, group 1 CNS-PNETs encompassed several histologic classes including embryonal tumor with abundant neuropil and true rosettes (ETANTR), medulloepithelioma, ependymoblastoma and CNS-PNETs with variable differentiation. Strikingly, gene expression and methylation profiling analyses revealed a common molecular signature enriched for primitive neural features, high LIN28/LIN28B and DNMT3B expression for all group 1 CNS-PNETs regardless of location or tumor histology. Our collective findings suggest that current known histologic categories of CNS-PNETs which include ETANTRs, medulloepitheliomas, ependymoblastomas in various CNS locations, comprise a common molecular and diagnostic entity and identify inhibitors of the LIN28/let7/PI3K/mTOR axis and DNMT3B as promising therapeutics for this distinct histogenetic entity.

Embryonal tumor with abundant neuropil and true rosettes (ETANTR), ependymoblastoma, and medulloepithelioma share molecular similarity and comprise a single clinicopathological entity

Three histological variants are known within the family of embryonal rosette-forming neuroepithelial brain tumors. These include embryonal tumor with abundant neuropil and true rosettes (ETANTR), ependymoblastoma (EBL), and medulloepithelioma (MEPL). In this study, we performed a comprehensive clinical, pathological, and molecular analysis of 97 cases of these rare brain neoplasms, including genome-wide DNA methylation and copy number profiling of 41 tumors. We identified uniform molecular signatures in all tumors irrespective of histological patterns, indicating that ETANTR, EBL, and MEPL comprise a single biological entity. As such, future WHO classification schemes should consider lumping these variants into a single diagnostic category, such as embryonal tumor with multilayered rosettes (ETMR). We recommend combined LIN28A immunohistochemistry and FISH analysis of the 19q13.42 locus for molecular diagnosis of this tumor category. Recognition of this distinct pediatric brain tumor entity based on the fact that the three histological variants are molecularly and clinically uniform will help to distinguish ETMR from other embryonal CNS tumors and to better understand the biology of these highly aggressive and therapy-resistant pediatric CNS malignancies, possibly leading to alternate treatment strategies.

Characterization of dual PTEN and p53-targeting microRNAs identifies microRNA-638/Dnm2 as a two-hit oncogenic locus

Tumor suppressor genes (TSGs) are often concomitantly lost or mutated in human cancers and have been shown to act synergistically to promote tumorigenesis. In addition to genomic alterations, posttranscriptional regulation by microRNAs (miRNAs) represents another mechanism by which TSG expression is dysregulated in cancers. Although miRNAs that target critical TSGs such as PTEN or p53 have been identified, little is known about miRNAs that concomitantly regulate both these key TSGs. In this study, we characterize microRNA 518c(∗) (miR-518c(∗)) and miR-638 as dual PTEN- and p53-targeting miRNAs that are upregulated in multiple human cancers. We focus on miR-638 and show that it associates independently with these two tumor suppressor transcripts as well as BRCA1, a known miR-638 target. We find that miR-638 overexpression promotes tumorigenesis and demonstrate cooperativity between miR-638 and its host gene Dnm2, suggesting that the Dnm2 locus encodes two distinct oncogenic components that play important roles in tumorigenesis.

Advances in managing medulloblastoma and intracranial primitive neuro-ectodermal tumors

Medulloblastoma and central nervous system (CNS)-primitive neuro-ectodermal tumors (PNETs) are a diverse group of entities which encompasses different pathological and clinical pictures. Initially divided based on histology and location, molecular insight is leading to new definitions and a change in the borders delineating these diseases, such that they become more divergent. Current treatment approaches consist of surgical resection, radiotherapy and intensive chemotherapy, dependent on age. Stratification is one risk factor shown to be prognostic and is divided into high- and average-risks. Outcomes with modern treatment regimens are good, particularly in average-risk medulloblastoma patients, but the cost of cure is high, with high rates of neurocognitive, endocrine and social dysfunction. The changing biological landscape, however, may allow for clearer prediction of tumor behavior, to better identify "good" and "bad" players within these groups. Discovery of subgroups with changes in dependent molecular pathways will also lead to the development of new specific targeted therapies. Presenting exciting opportunities, these advances may transform the treatment for some patients, revolutionizing therapy in the future. Several challenges, however, are yet to be faced and caution is needed not to abandon previously defined prognostic factors on the strength of thus far retrospective evidence. We are witnessing a new era of trials with biological stratification involving multiple subgroups and treatment arms, based on specific tumor-related targets. This review discusses the changing face of medulloblastoma and CNS-PNETs and how we move molecular advances into clinical trials that benefit patients.

Expression of two parental imprinted miRNAs improves the risk stratification of neuroblastoma patients

Age at diagnosis, stage, and MYCN amplification are the cornerstones of the risk-stratification score of neuroblastoma that enables defining patients at low- and high risk. Refinement of this stratification is needed to optimize standard treatment and to plan future clinical trials. We investigated whether two parental imprinted miRNAs (miR-487b and miR-516a-5p) may lead to a risk score with a better discrimination. Expression levels of maternal miR-487b and paternal miR-516a-5p were determined using quantitative RT-PCR both for 231 neuroblastoma tumors (derivation set) and 101 independent neuroblastoma tumors (validation set). Survival outcomes were overall survival (OS) and disease-free survival (DFS). Multivariable Cox models were developed from derivation set and their performance evaluated using Akaike's information criterion (AIC) (goodness-of-fit) and time-dependent area under curves (discrimination). The selected model was validated using internal and external validation. The prognostic model including current prognostic factors plus miR-487b, miR-516a-5p, and interaction between two miRNAs was selected. Performance of this model was better in terms of both predictive ability (smallest AIC) and discrimination power (AUC close to 0.70). This model identifies three risk groups: high (3), intermediate (2), and low (1). Hazard ratios (HR) across risk groups were HR_2/1 = 6.3 (2.7–14.6), HR_3/1 = 14.8 (7.2–30.2) for OS and HR_2/1 = 2.8 (1.5–5.4), HR_3/1 = 7.2 (3.9–13.4) for DFS. The rank between these three risk groups was maintained and validated when performing internal and external validation. Expression of maternal miR-487b and paternal miR-516a-5p improves the risk stratification. This better discrimination at diagnosis is of clinical utility both for current and future treatments of neuroblastoma patients.

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.

Diagnostic application of high resolution single nucleotide polymorphism array analysis for children with brain tumors

Single nucleotide polymorphism (SNP) array analysis is currently used as a first tier test for pediatric brain tumors at The Children's Hospital of Philadelphia. The results from 100 consecutive patients are summarized in the present report. Eighty-seven percent of the tumors had at least one pathogenic copy number alteration. Nineteen of 56 low grade gliomas (LGGs) demonstrated a duplication in 7q34, which resulted in a KIAA1549-BRAF fusion. Chromosome band 7q34 deletions, which resulted in a FAM131B-BRAF fusion, were identified in one pilocytic astrocytoma (PA) and one dysembryoplastic neuroepithelial tumor (DNT). One ganglioglioma (GG) demonstrated a 6q23.3q26 deletion that was predicted to result in a MYB-QKI fusion. Gains of chromosomes 5, 6, 7, 11, and 20 were seen in a subset of LGGs. Monosomy 6, deletion of 9q and 10q, and an i(17)(q10) were each detected in the medulloblastomas (MBs). Deletions and regions of loss of heterozygosity that encompassed TP53, RB1, CDKN2A/B, CHEK2, NF1, and NF2 were identified in a variety of tumors, which led to a recommendation for germline testing. A BRAF p.Thr599dup or p.V600E mutation was identified by Sanger sequencing in one and five gliomas, respectively, and a somatic TP53 mutation was identified in a fibrillary astrocytoma. No TP53 hot-spot mutations were detected in the MBs. SNP array analysis of pediatric brain tumors can be combined with pathologic examination and molecular analyses to further refine diagnoses, offer more accurate prognostic assessments, and identify patients who should be referred for cancer risk assessment.

A patient tumor-derived orthotopic xenograft mouse model replicating the group 3 supratentorial primitive neuroectodermal tumor in children

BACKGROUND

Supratentorial primitive neuroectodermal tumor (sPNET) is a malignant brain tumor with poor prognosis. New model systems that replicate sPNET's molecular subtype(s) and maintain cancer stem cell (CSC) pool are needed.

METHODS

A fresh surgical specimen of a pediatric sPNET was directly injected into the right cerebrum of Rag2/SCID mice. The xenograft tumors were serially sub-transplanted in mouse brains, characterized histopathologically, and subclassified into molecular subtype through qRT-PCR and immunohistochemical analysis. CSCs were identified through flow cytometric profiling of putative CSC markers (CD133, CD15, CD24, CD44, and CD117), functional examination of neurosphere forming efficiency in vitro, and tumor formation capacity in vivo. To establish a neurosphere line, neurospheres were propagated in serum-free medium.

RESULTS

Formation of intracerebral xenograft tumors was confirmed in 4 of the 5 mice injected with the patient tumor. These xenograft tumors were sub-transplanted in vivo 5 times. They replicated the histopathological features of the original patient tumor and expressed the molecular markers (TWIST1 and FOXJ1) of group 3 sPNET. CD133(+) and CD15(+) cells were found to have strong neurosphere-forming efficiency in vitro and potent tumor-forming capacity (with as few as 100 cells) in vivo. A neurosphere line BXD-2664PNET-NS was established that preserved stem cell features and expressed group 3 markers.

CONCLUSION

We have established a group 3 sPNET xenograft mouse model (IC-2664PNET) with matching neurosphere line (BXD-2664PNET-NS) and identified CD133(+) and CD15(+) cells as the major CSC subpopulations. This novel model system should facilitate biological studies and preclinical drug screenings for childhood sPNET.

Fusion of TTYH1 with the C19MC microRNA cluster drives expression of a brain-specific DNMT3B isoform in the embryonal brain tumor ETMR

Embryonal tumors with multilayered rosettes (ETMRs) are rare, deadly pediatric brain tumors characterized by high-level amplification of the microRNA cluster C19MC. We performed integrated genetic and epigenetic analyses of 12 ETMR samples and identified, in all cases, C19MC fusions to TTYH1 driving expression of the microRNAs. ETMR tumors, cell lines and xenografts showed a specific DNA methylation pattern distinct from those of other tumors and normal tissues. We detected extreme overexpression of a previously uncharacterized isoform of DNMT3B originating at an alternative promoter that is active only in the first weeks of neural tube development. Transcriptional and immunohistochemical analyses suggest that C19MC-dependent DNMT3B deregulation is mediated by RBL2, a known repressor of DNMT3B. Transfection with individual C19MC microRNAs resulted in DNMT3B upregulation and RBL2 downregulation in cultured cells. Our data suggest a potential oncogenic re-engagement of an early developmental program in ETMR via epigenetic alteration mediated by an embryonic, brain-specific DNMT3B isoform.

A developmental program drives aggressive embryonal brain tumors

Embryonal tumors with multilayered rosettes (ETMRs) are primitive neuroectodermal tumors arising in infants. A new study shows that these tumors are universally driven by fusion of the promoter of a gene with brain-specific expression, TTYH1, to C19MC, the largest human microRNA cluster, activating a fetal neural development program.

A novel C19MC amplified cell line links Lin28/let-7 to mTOR signaling in embryonal tumor with multilayered rosettes

BACKGROUND

Embryonal tumor with multilayered rosettes (ETMR) is an aggressive central nervous system primitive neuroectodermal tumor (CNS-PNET) variant. ETMRs have distinctive histology, amplification of the chromosome 19 microRNA cluster (C19MC) at chr19q13.41-42, expression of the RNA binding protein Lin28, and dismal prognosis. Functional and therapeutic studies of ETMR have been limited by a lack of model systems.

METHODS

We have established a first cell line, BT183, from a case of ETMR and characterized its molecular and cellular features. LIN28 knockdown was performed in BT183 to examine the potential role of Lin28 in regulating signaling pathway gene expression in ETMR. Cell line findings were corroborated with immunohistochemical studies in ETMR tissues. A drug screen of 73 compounds was performed to identify potential therapeutic targets.

RESULTS

The BT183 line maintains C19MC amplification, expresses C19MC-encoded microRNAs, and is tumor initiating. ETMRs, including BT183, have high LIN28 expression and low let-7 miRNA expression, and show evidence of mTOR pathway activation. LIN28 knockdown increases let-7 expression and decreases expression of IGF/PI3K/mTOR pathway components. Pharmacologic inhibition of the mTOR pathway reduces BT183 cell viability.

CONCLUSIONS

BT183 retains key genetic and histologic features of ETMR. In ETMR, Lin28 is not only a diagnostic marker but also a regulator of genes involved in growth and metabolism. Our findings indicate that inhibitors of the IGF/PI3K/mTOR pathway may be promising novel therapies for these fatal embryonal tumors. As the first patient-derived cell line of these rare tumors, BT183 is an important, unique reagent for investigating ETMR biology and therapeutics.

Evolving of therapeutic strategies for CNS-PNET

BACKGROUND

A protocol for the intensive treatment of non-cerebellar PNET (CNS-PNET) combining chemotherapy and radiotherapy was launched in 2000. Efforts were subsequently made to improve the prognosis and to de-escalate the treatment for selected patient groups.

PROCEDURE

Twenty-eight consecutive patients were enrolled for a high-dose drug schedule (methotrexate, etoposide, cyclophosphamide, and carboplatin ± vincristine), followed by hyperfractionated accelerated CSI (HART-CSI) at total doses of 31-39 Gy, depending on the patient's age, with two high-dose thiotepa courses following CSI. After the first 15 patients had been treated, craniospinal irradiation (CSI) was replaced with focal radiotherapy (RT) for selected cases (non-metastatic and not progressing during induction chemotherapy). Eight of the 28 children received the same chemotherapy but conventionally fractionated focal RT at 54 Gy.

RESULTS

The 5-year progression-free survival (PFS), event-free survival (EFS), and overall survival (OS) rates were 62%, 53%, and 52%, respectively, for the whole series, and 70%, 70%, and 87% for the eight focally irradiated children. Residual disease and metastases were not prognostically significant. In children with residual disease, response to RT was significant (5-year PFS 59% vs. 20%, P = 0.01), while the total dose of CSI was not. There were three treatment-related toxic events. Relapses were local in seven cases (including two of the eight focally irradiated patients), and both local and disseminated in 2.

CONCLUSIONS

This intensive schedule enabled treatment stratification for the purposes of radiation, thereby sparing some children full-dose CSI. Local control is the main goal of treatment for CNS-PNET.

Post-chemotherapy maturation in supratentorial primitive neuroectodermal tumors

Maturation in central nervous system embryonal tumors is an uncommon phenomenon that is mainly reported in the context of specific histological subgroups of medulloblastoma. In this report we describe two cases of histological maturation in patients with supratentorial primitive neuroectodermal tumor with strikingly different outcomes. We discuss the potential impact of such findings on treatment and outcome.

Review: placenta-specific microRNAs in exosomes - good things come in nano-packages

MicroRNAs (miRNAs) are small noncoding RNA gene products that commonly regulate mRNA expression by repression of translation and/or transcript decay. Whereas common and unique types of miRNAs are expressed by the placenta during pregnancy, the functions of most placental miRNA species are unknown. In addition to their intracellular silencing function, miRNAs are also released to the extracellular space and systemic circulation, where they can potentially target cells to regulate mRNA and protein expression, providing a non-hormonal means of intercellular communication that contributes to tissue homeostasis and disease pathophysiology. This review centers on extracellular miRNAs that originate in trophoblasts and that could mediate crosstalk between the feto-placental unit and the mother during pregnancy. We specifically detail the function of miRNAs from the primate-specific chromosome 19 miRNA cluster. These miRNAs are highly expressed in human placentas and in the serum of pregnant women. They are also packaged into extracellular vesicles of diverse sizes, including exosomes, and endow non-trophoblastic cells with resistance to a variety of viruses.

The role of CD133+ cells in a recurrent embryonal tumor with abundant neuropil and true rosettes (ETANTR)

Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is a recently described embryonal neoplasm of the central nervous system, consisting of a well-circumscribed embryonal tumor of infancy with mixed features of ependymoblastoma (multilayer ependymoblastic rosettes and pseudorosettes) and neuroblastoma (neuroblastic rosettes) in the presence of neuropil-like islands. We present the case of a young child with a very aggressive tumor that rapidly recurred after gross total resection, chemotherapy and radiation. Prominent vascular sclerosis and circumscribed tumor led to the diagnosis of malignant astroblastoma; however, rapid recurrence and progression of this large tumor after gross total resection prompted review of the original pathology. ETANTR is histologically distinct with focal glial fibrillary acid protein (GFAP) and synaptophysin expression in the presence of neuronal and ependymoblastic rosettes with focal neuropil islands. These architectural features, combined with unique chromosome 19q13.42 amplification, confirmed the diagnosis. In this report, we describe tumor stem cell (TSC) marker CD133, CD15 and nestin alterations in ETANTR before and after chemotherapy. We found that TSC marker CD133 was richly expressed after chemotherapy in recurrent ETANTR, while CD15 is depleted compared with that expressed in the original tumor, suggesting that CD133+ cells likely survived initial treatment, further contributing to formation of the recurrent tumor.

Comparative expression analysis reveals lineage relationships between human and murine gliomas and a dominance of glial signatures during tumor propagation in vitro

Brain tumors are thought to originate from stem/progenitor cell populations that acquire specific genetic mutations. Although current preclinical models have relevance to human pathogenesis, most do not recapitulate the histogenesis of the human disease. Recently, a large series of human gliomas and medulloblastomas were analyzed for genetic signatures of prognosis and therapeutic response. Using a mouse model system that generates three distinct types of intrinsic brain tumors, we correlated RNA and protein expression levels with human brain tumors. A combination of genetic mutations and cellular environment during tumor propagation defined the incidence and phenotype of intrinsic murine tumors. Importantly, in vitro passage of cancer stem cells uniformly promoted a glial expression profile in culture and in brain tumors. Gene expression profiling revealed that experimental gliomas corresponded to distinct subclasses of human glioblastoma, whereas experimental supratentorial primitive neuroectodermal tumors (sPNET) correspond to atypical teratoid/rhabdoid tumor (AT/RT), a rare childhood tumor.

The role of the WNT/β-catenin pathway in central nervous system primitive neuroectodermal tumours (CNS PNETs)

Background:

Central nervous system primitive neuroectodermal tumours (CNS PNETs) are embryonal tumours occurring predominantly in children. Current lack of knowledge regarding their underlying biology hinders development of more effective treatments. We previously identified WNT/β-catenin pathway activation in one-third of CNS PNETs, which was potentially linked to a better prognosis. In this study, we have extended our cohort, achieving a statistically significant correlation with prognosis. We additionally investigated the biological effects of WNT/β-catenin pathway activation in tumour pathogenesis.

Methods:

A total of 42 primary and 8 recurrent CNS PNETs were analysed for WNT/β-catenin pathway status using β-catenin immunohistochemistry. Genomic copy number and mRNA expression data were analysed to identify a molecular profile linked to WNT/β-catenin pathway activation.

Results:

Pathway activation was seen in 26% of CNS PNETs and was significantly associated with longer overall survival. Genes displaying a significant difference in expression levels, between tumours with and without WNT/β-catenin pathway activation, included several involved in normal CNS development suggesting aberrant pathway activation may be disrupting this process.

Conclusion:

We have identified WNT/β-catenin pathway status as a marker, which could potentially be used to stratify disease risk for patients with CNS PNET. Gene expression data suggest pathway activation is disrupting normal differentiation in the CNS.

A functional genomics screen for microRNA regulators of NF-kappaB signaling

BACKGROUND

The nuclear factor-KappaB (NF-κB) pathway is conserved from fruit flies to humans and is a key mediator of inflammatory signaling. Aberrant regulation of NF-κB is associated with several disorders including autoimmune disease, chronic inflammation, and cancer, making the NF-κB pathway an attractive therapeutic target. Many regulatory components of the NF-κB pathway have been identified, including microRNAs (miRNAs). miRNAs are small non-coding RNAs and are common components of signal transduction pathways. Here we present a cell-based functional genomics screen to systematically identify miRNAs that regulate NF-κB signaling.

RESULTS

We screened a library of miRNA mimics using a NF-κB reporter cell line in the presence and absence of tumor necrosis factor (+/- TNF). There were 9 and 15 hits in the -TNF and +TNF screens, respectively. We identified putative functional targets of these hits by integrating computational predictions with NF-κB modulators identified in a previous genome-wide cDNA screen. miR-517a and miR-517c were the top hits, activating the reporter 86- and 126-fold, respectively. Consistent with these results, miR-517a/c induced the expression of endogenous NF-κB targets and promoted the nuclear localization of p65 and the degradation of IκB. We identified TNFAIP3 interacting protein1 (TNIP1) as a target and characterized a functional SNP in the miR-517a/c binding site. Lastly, miR-517a/c induced apoptosis in vitro, which was phenocopied by knockdown of TNIP1.

CONCLUSIONS

Our study suggests that miRNAs are common components of NF-κB signaling and miR-517a/c may play an important role in linking NF-κB signaling with cell survival through TNIP1.

LIN28A immunoreactivity is a potent diagnostic marker of embryonal tumor with multilayered rosettes (ETMR)

Embryonal tumor with multilayered rosettes (ETMR, previously known as ETANTR) is a highly aggressive embryonal CNS tumor, which almost exclusively affects infants and is associated with a dismal prognosis. Accurate diagnosis is of critical clinical importance because of its poor response to current treatment protocols and its distinct biology. Amplification of the miRNA cluster at 19q13.42 has been identified previously as a genetic hallmark for ETMR, but an immunohistochemistry-based assay for clinical routine diagnostics [such as INI-1 for atypical teratoid rhabdoid tumor (AT/RT)] is still lacking. In this study, we screened for an ETMR-specific marker using a gene-expression profiling dataset of more than 1,400 brain tumors and identified LIN28A as a highly specific marker for ETMR. The encoded protein binds small RNA and has been implicated in stem cell pluripotency, metabolism and tumorigenesis. Using an LIN28A specific antibody, we carried out immunohistochemical analysis of LIN28A in more than 800 childhood brain-tumor samples and confirmed its high specificity for ETMR. Strong LIN28A immunoexpression was found in all 37 ETMR samples tested, whereas focal reactivity was only present in a small (6/50) proportion of AT/RT samples. All other pediatric brain tumors were completely LIN28A-negative. In summary, we established LIN28A immunohistochemistry as a highly sensitive and specific, rapid, inexpensive diagnostic tool for routine pathological verification of ETMR.

Small regulatory RNAs controlled by genomic imprinting and their contribution to human disease

More than a hundred protein-coding genes are controlled by genomic imprinting in humans. These atypical genes are organized in chromosomal domains, each of which is controlled by a differentially methylated "imprinting control region" (ICR). How ICRs mediate the parental allele-specific expression of close-by genes is now becoming understood. At several imprinted domains, this epigenetic mechanism involves the action of long non-coding RNAs. It is less well appreciated that imprinted gene domains also transcribe hundreds of microRNA and small nucleolar RNA genes and that these represent the densest clusters of small RNA genes in mammalian genomes. The evolutionary reasons for this remarkable enrichment of small regulatory RNAs at imprinted domains remain unclear. However, recent studies show that imprinted small RNAs modulate specific functions in development and metabolism and also are frequently perturbed in cancer. Here, we review our current understanding of imprinted small RNAs in the human genome and discuss how perturbation of their expression contributes to disease.

Identification of deregulated miRNAs and their targets in hepatitis B virus-associated hepatocellular carcinoma

AIM: To identify the differentially expressed miRNAs and their targets in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC).

METHODS: Six hundred and sixty seven human miRNAs were quantitatively analyzed by Taqman low-density miRNA array (TLDA) in HBV-HCC tissues. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were used to analyze the significant function and pathway of the differentially expressed miRNAs in HBV-HCC. TargetScan software was used to predict the targets of deregulated miRNAs. Western blotting and luciferase assay were performed to verify the targets of these miRNAs.

RESULTS: Ten up-regulated miRNAs (miR-217, miR-518b, miR-517c, miR-520g, miR-519a, miR-522, miR-518e, miR-525-3p, miR-512-3p, and miR-518a-3p) and 11 down-regulated miRNAs (miR-138, miR-214, miR-214#, miR-199a-5p, miR-433, miR-511, miR-592, miR-483-3p, miR-483-5p, miR-708 and miR-1275) were identified by Taqman miRNAs array and confirmed quantitatively by reverse transcription polymerase chain reaction in HCC and adjacent non-tumor tissues. GO and KEGG pathway analysis revealed that “regulation of actin cytoskeleton” and “pathway in cancer” are most likely to play critical roles in HCC tumorigenesis. MiR-519a and ribosomal protein S6 kinase polypeptide 3 (RPS6KA3) were predicted as the most significant candidates by miRNA-mRNA network. In addition, cyclin D3 (CCND3) and clathrin heavy chain (CHC), usually up-regulated in HCC tissues, were validated as the direct target of miR-138 and miR-199a-5p, respectively.

CONCLUSION: Our data suggest an importance of miR-138 and miR-199a-5p as well as their targets CCND3 and CHC in HCC tumorigenesis, and may provide more evidence for reliability of integrative bioinformatics analysis.

The microRNA cluster C19MC is deregulated in parathyroid tumours

A subset of over-expressed microRNAs (miRNAs) identified in parathyroid carcinomas (Ca) compared to normal glands belongs to C19MC, a cluster on chromosome 19q13.4 involved in stem cell biology and tumourigenesis. In this study, the expression of C19MC-MIR371-3 clusters and the molecular mechanisms presiding their modulation were investigated in a series of six normal parathyroids, 24 adenomas (Ad), 15 Ca and five matched metastases. The general expression levels of C19MC or MIR371-3 clusters in Ad lesions did not differ from normal glands, while they distinguished Ad from Ca at unsupervised hierarchical cluster analysis (P=0.0008). MIR517C showed the most significant difference in expression between Ca and Ad (P=0.0003) and it positively correlated with serum calcium, parathormone and tumour weight. In regard to the molecular mechanism determining C19MC cluster activation, we could detect C19MC copy number (CN) gain in ten Ca (67%) extending distal to the MIR371-3 cluster in almost all samples. Conversely, only four Ad (16%) showed C19MC amplification, with one case presenting distal genomic aberration to MIR371-3. Globally, CN variations of 19q13.4 loci were significantly associated with MIR517C up-regulation (P=0.006). Opposite to normal glands where C19MC promoter was methylated, hypomethylation occurred in 15 out of 30 analysed tumours. Though the epigenetic status did not correlate with C19MC miRNA expression levels, loss of C19MC promoter methylation was significantly associated with Ca and metastatic disease (P=0.01). In conclusion, C19MC cluster aberrations are a characteristic of Ca with respect to Ad. Altogether, these evidences point towards a role for 19q13.4 miRNA clusters as oncogenes in parathyroid tumourigenesis.

Multiple CDK/CYCLIND genes are amplified in medulloblastoma and supratentorial primitive neuroectodermal brain tumor

Embryonal brain tumors, which include medulloblastoma and the more aggressive supratentorial primitive neuroectodermal tumor (sPNET), comprise one of the largest group of malignant pediatric brain tumors. We observed in high resolution array comparative genomic hybridization and polymerase chain reaction analyses that several different components of the CDK/CYCLIND/pRB regulatory complex, including the CDK4/6 and CCND1/2 loci, are targets of gene amplification in medulloblastoma and sPNET. CDK6 and CCND1 gene amplification were respectively most common and robust, and overall CDK/CYCLIND gene amplification was more commonly observed in sPNET (25%) than medulloblastoma (1-5%). CDK6 overexpression enhanced in vitro and in vivo oncogenicity and endogenous CDK6 or CCND1 knockdown decreased pRB phosphorylation and impaired cell cycle progression in both medulloblastoma and sPNET cell lines. Although animal models implicate the pRB tumor suppressor pathway in medulloblastoma and sPNET, mutations of RB1 or the related INK4 tumor suppressor loci are rare in primary human tumors. Our data suggest that CDK/CYCLIND gene amplification may represent important mechanisms for functional inactivation of pRB in medulloblastoma and sPNET.

MicroRNA-520e suppresses growth of hepatoma cells by targeting the NF-κB-inducing kinase (NIK)

MicroRNAs (miRNAs) are small, non-coding RNAs that can act as oncogenes or tumor suppressor genes in human cancer. Emerging evidence indicates that deregulation of miRNAs contributes to the hepatocarcinogenesis. In the present study, we demonstrated that the levels of miR-520e were dramatically decreased in examined hepatoma cell lines and clinical hepatocellular carcinoma (HCC) tissues. Moreover, we found that DNA hypermethylation in the upstream region of miR-520e resulted in the downregulation of miR-520e. Next, we demonstrated that introduction of miR-520e dramatically suppressed the growth of hepatoma cells in vitro and in vivo, whereas silencing the expression of miR-520e by anti-miR-520e resulted in a promoted cell proliferation, suggesting that miR-520e may be a novel tumor suppressor. Further studies revealed that NF-κB-inducing kinase (NIK) was one of the direct target genes of miR-520e, as miR-520e directly bound to the 3'untranslated region of NIK, which reduced the expression of NIK at the levels of mRNA and protein. Moreover, silencing of NIK was able to inhibit the growth of hepatoma cells, similar to the effect of miR-520e overexpression on growth of hepatoma cells. Meanwhile, the knockdown of NIK expression reversed the enhanced proliferation mediated by anti-miR-520e. In addition, miR-520e significantly decreased the phosphorylation of ERK1/2 (p-ERK1/2) and depressed the transcriptional activity and nuclear translocation of nuclear factor κB (NF-κB) (p65). These results suggest that miR-520e suppresses the growth of hepatoma cells by targeting NIK involving the NIK/p-ERK1/2/NF-κB signaling pathway. Finally, we showed that the intratumoral injection with miR-520e was able to directly repress the growth of hepatoma cells in the nude mice. Thus, our finding provides new insight into the mechanism of hepatocarcinogenesis, indicating a therapeutic potential of miR-520e in the treatment of HCC.

Markers of survival and metastatic potential in childhood CNS primitive neuro-ectodermal brain tumours: an integrative genomic analysis

BACKGROUND

Childhood CNS primitive neuro-ectodermal brain tumours (PNETs) are very aggressive brain tumours for which the molecular features and best treatment approaches are unknown. We assessed a large cohort of these rare tumours to identify molecular markers to enhance clinical management of this disease.

METHODS

We obtained 142 primary hemispheric CNS PNET samples from 20 institutions in nine countries and examined transcriptional profiles for a subset of 51 samples and copy number profiles for a subset of 77 samples. We used clustering, gene, and pathway enrichment analyses to identify tumour subgroups and group-specific molecular markers, and applied immunohistochemical and gene-expression analyses to validate and assess the clinical significance of the subgroup markers.

FINDINGS

We identified three molecular subgroups of CNS PNETs that were distinguished by primitive neural (group 1), oligoneural (group 2), and mesenchymal lineage (group 3) gene-expression signatures with differential expression of cell-lineage markers LIN28 and OLIG2. Patients with group 1 tumours were most often female (male:female ratio 0·61 for group 1 vs 1·25 for group 2 and 1·63 for group 3; p=0·043 [group 1 vs groups 2 and 3]), youngest (median age at diagnosis 2·9 years [95% CI 2·4-5·2] for group 1 vs 7·9 years [6·0-9·7] for group 2 and 5·9 years [4·9-7·8] for group 3; p=0·005), and had poorest survival (median survival 0·8 years [95% CI 0·5-1·2] in group 1, 1·8 years [1·4-2·3] in group 2 and 4·3 years [0·8-7·8] in group 3; p=0·019). Patients with group 3 tumours had the highest incidence of metastases at diagnosis (no distant metastasis:metastasis ratio 0·90 for group 3 vs 2·80 for group 1 and 5·67 for group 2; p=0·037).

INTERPRETATION

LIN28 and OLIG2 are promising diagnostic and prognostic molecular markers for CNS PNET that warrant further assessment in prospective clinical trials.

FUNDING

Canadian Institute of Health Research, Brainchild/SickKids Foundation, and the Samantha Dickson Brain Tumour Trust.