Neuroblastoma (NB) is one of the most common forms of cancer in children, accounting for 15% of pediatric cancer deaths. The clinical course of these tumors is highly variable and is dependent on such factors as age at presentation, stage, ploidy and genomic abnormalities. Hemizygous deletion of chromosome 1p occurs in approximately 30% of advanced stage tumors, is associated with a poor prognosis, and likely leads to the loss of one or more tumor suppressor genes. We show here that microRNA (miRNA)-34a (1p36.23) is generally expressed at lower levels in unfavorable primary NB tumors and cell lines relative to normal adrenal tissue and that reintroduction of this miRNA into three different NB cell lines causes a dramatic reduction in cell proliferation through the induction of a caspase-dependent apoptotic pathway. As a potential mechanistic explanation for this observation, we demonstrate that miR-34a directly targets the messenger ribonucleic acid (mRNA) encoding E2F3 and significantly reduces the levels of E2F3 protein, a potent transcriptional inducer of cell-cycle progression. Furthermore, miR-34a expression increases during retinoic acidinduced differentiation of the SK-N-BE cell line, whereas E2F3 protein levels decrease. Thus, adding to the increasing role of miRNAs in cancer, miR-34a may act as a suppressor of NB tumorgenesis.

Temporal lobe epilepsy is a common, chronic neurologic disorder characterized by recurrent spontaneous seizures. MicroRNAs (miRNAs) are small, non-coding RNAs that regulate posttranscriptional expression of protein-coding mRNAs, which may have important roles in the pathogenesis of neurologic disorders. In models of prolonged, injurious seizures (status epilepticus) and in experimental and human epilepsy, we found up-regulation of miR-134, a brainspecific, activity-regulated miRNA implicated in the control of dendritic spine morphology. Silencing of miR-134 expression in vivo using antagomirs reduced hippocampal CA3 pyramidal neuron dendrite spine density by 21%, and rendered mice refractory to seizures and hippocampal injury caused by status epilepticus. Depletion of miR-134 after status epilepticus reduced the later occurrence of spontaneous seizures by over 90% and mitigated attendant pathologic features of temporal lobe epilepsy. Thus, silencing miR-134 exerts prolonged seizure suppressant and Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

LIN28B regulates developmental processes by modulating microRNAs (miRNAs) of the let-7 family. A role for LIN28B in cancer has been proposed but has not been established in vivo. Here, we report that LIN28B showed genomic aberrations and extensive overexpression in high-risk neuroblastoma compared to several other tumor entities and normal tissues. High LIN28B expression was an independent risk factor for adverse outcome in neuroblastoma. LIN28B signaled through repression of the let-7 miRNAs and consequently resulted in elevated MYCN protein expression in neuroblastoma cells. LIN28B-let-7-MYCN signaling blocked differentiation of normal neuroblasts and neuroblastoma cells. These findings were fully recapitulated in a mouse model in which LIN28B expression in the sympathetic adrenergic lineage induced development of neuroblastomas marked by low let-7 miRNA levels and high MYCN protein expression. Interference with this pathway might offer therapeutic perspectives.

Neuroblastoma accounts for 15% of pediatric cancer deaths, and although a few protein-coding genes, such as MYCN, are involved with aggressive pathogenicity, the identification of novel biological targets for therapeutic intervention is still a necessary prerequisite for improving patient survival. Expression profiling of 157 microRNA (miRNA) loci in 35 primary neuroblastoma tumors indicates that 32 loci are differentially expressed in favorable and unfavorable tumor subtypes, indicating a potential role of miRNAs in neuroblastoma pathogenesis. Many of these loci are significantly underexpressed in tumors with MYCN amplification, which have particularly poor prognoses. Interestingly, we found that miRNA expression levels substantially change in a MYCNamplified cell line following exposure to retinoic acid, a compound which is well known for causing reductions in MYCN expression and for inducing neuroblastoma cell lines to undergo neuronal differentiation. We also show that small interfering RNA inhibition of MYCN by itself causes similar alterations in the expression of miRNA loci. In vitro functional studies of one locus, miR-184, indicate that it plays a significant role in apoptosis. The association of experimentally induced alterations of miRNA expression in neuroblastoma cell lines with differentiation or apoptosis leads us to conclude that these loci play important roles in neuroblastoma pathogenesis. We further suggest that MYCN may mediate a tumorigenic effect, in part, through directly or indirectly regulating the expression of miRNAs that are involved with neural cell differentiation and/or apoptosis, warranting substantial further studies of miRNAs as potential therapeutic targets. [Cancer Res 2007;67(3):976-83]

When an otherwise harmful insult to the brain is preceded by a brief, noninjurious stimulus, the brain becomes tolerant, and the resulting damage is reduced. Epileptic tolerance develops when brief seizures precede an episode of prolonged seizures (status epilepticus). MicroRNAs (miRNAs) are small, noncoding RNAs that function as post-transcriptional regulators of gene expression. We investigated how prior seizure preconditioning affects the miRNA response to status epilepticus evoked by intra-amygdalar kainic acid in mice. The miRNA was extracted from the ipsilateral CA3 subfield 24 hours after focal-onset status epilepticus in animals that had previously received either seizure preconditioning (tolerance) or no preconditioning (injury), and mature miRNA levels were measured using TaqMan low-density arrays. Expression of 21 miRNAs was increased, relative to control, after status epilepticus alone, and expression of 12 miRNAs was decreased. Increased miR-132 levels were matched with increased binding to Argonaute-2, a constituent of the RNA-induced silencing complex. In tolerant animals, expression responses of >40% of the injury-group-detected miRNAs differed, being either unchanged relative to control or down-regulated, and this included miR-132. In vivo microinjection of locked nucleic acid-modified oligonucleotides (antagomirs) against miR-132 depleted hippocampal miR-132 levels and reduced seizure-induced neuronal death. Thus, our data strongly suggest that miRNAs are important regulators of seizure-induced neuronal death.

Understanding the genes and genetic pathways targeted by recurrent chromosomal imbalances in malignancy, along with the molecular mechanisms that generate the imbalances, are important problems in cancer biology. In this report, we demonstrate that oligonucleotide array CGH (oaCGH) analysis can routinely map chromosomal imbalance breakpoints at exon-level resolution, including imbalances that are single copy number genomic alterations. Different tiling-path array designs were used in this study: a whole-genome array with a 6-kb median probe spacing and fine-tiling arrays for selected genomic regions with either 50- or 140-bp median probe spacing. In both array formats, oligonucleotide probes were of isothermal design and were tiled through genic and inter-genic regions. Whole-genome oaCGH analysis of two neuroblastoma cell lines and three primary tumors led to the identification of 58 chromosomal breakpoints that generated 45 large-scale partial chromosomal imbalances (> 2 Mb). An unexpectedly high proportion (34%) of these breakpoint intervals mapped to regions containing segmental duplications. In addition, 88 smaller-sized regions (< 2 Mb) of imbalance were detected, the majority of which mapped to segmentally duplicated regions and may reflect constitutional copy number polymorphisms. The chromosomal breakpoints for 12 recurrent abnormalities exhibited in neuroblastoma tumors and cell lines, including MYCN amplicon boundaries, loss of 3p, loss of 11q, and gain of 17q, could be mapped to intervals ranging from 50 bp to 10 kb in size using high-density fine-tiling oligonucleotide microarrays. Fine-tiling oaCGH analysis provides an unprecedented level of resolution, allowing detailed mapping of recurrent unbalanced chromosomal abnormalities. Supplementary material for this article can be found on the Genes, Chromosomes, and Cancer website at http://www.interscience.wiley.com/jpages/1045-2257/suppmat/index.html.

Material Supplementary 9.DC1http://www.jimmunol.org/content/suppl/2010/01/13/jimmunol.090266References

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