Gene Summary

Gene:DROSHA; drosha, ribonuclease type III
Summary:Members of the ribonuclease III superfamily of double-stranded (ds) RNA-specific endoribonucleases participate in diverse RNA maturation and decay pathways in eukaryotic and prokaryotic cells (Fortin et al., 2002 [PubMed 12191433]). The RNase III Drosha is the core nuclease that executes the initiation step of microRNA (miRNA) processing in the nucleus (Lee et al., 2003 [PubMed 14508493]).[supplied by OMIM, Mar 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:ribonuclease 3
Source:NCBIAccessed: 06 August, 2015


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 06 August 2015 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 06 August, 2015 using data from PubMed, MeSH and CancerIndex

Latest Publications: DROSHA (cancer-related)

Kurzynska-Kokorniak A, Koralewska N, Pokornowska M, et al.
The many faces of Dicer: the complexity of the mechanisms regulating Dicer gene expression and enzyme activities.
Nucleic Acids Res. 2015; 43(9):4365-80 [PubMed] Free Access to Full Article Related Publications
There is increasing evidence indicating that the production of small regulatory RNAs is not the only process in which ribonuclease Dicer can participate. For example, it has been demonstrated that this enzyme is also involved in chromatin structure remodelling, inflammation and apoptotic DNA degradation. Moreover, it has become increasingly clear that cellular transcript and protein levels of Dicer must be strictly controlled because even small changes in their accumulation can initiate various pathological processes, including carcinogenesis. Accordingly, in recent years, a number of studies have been performed to identify the factors regulating Dicer gene expression and protein activity. As a result, a large amount of complex and often contradictory data has been generated. None of these data have been subjected to an exhaustive review or critical discussion. This review attempts to fill this gap by summarizing the current knowledge of factors that regulate Dicer gene transcription, primary transcript processing, mRNA translation and enzyme activity. Because of the high complexity of this topic, this review mainly concentrates on human Dicer. This review also focuses on an additional regulatory layer of Dicer activity involving the interactions of protein and RNA factors with Dicer substrates.

Durieux E, Descotes F, Nguyen AM, et al.
Somatic DICER1 gene mutation in sporadic intraocular medulloepithelioma without pleuropulmonary blastoma syndrome.
Hum Pathol. 2015; 46(5):783-7 [PubMed] Related Publications
Germline DICER1 gene mutation has been described in ocular medulloepithelioma associated with pleuropulmonary blastoma family tumor and dysplasia syndrome. We present a case of sporadic ocular medulloepithelioma in an 18-year-old woman with D1709N somatic mutation in DICER1 gene, which has not been previously described. This case highlights the potential use of DICER1 gene sequencing to resolve the diagnostic challenge in recurrent and metastatic malignant medulloepithelioma, when morphology and immunohistochemistry are inconclusive. Further studies in larger series of this type of tumor are needed to confirm the relevance of this molecular abnormality in the tumorigenesis of this embryonic-type ocular tumor.

Wegert J, Ishaque N, Vardapour R, et al.
Mutations in the SIX1/2 pathway and the DROSHA/DGCR8 miRNA microprocessor complex underlie high-risk blastemal type Wilms tumors.
Cancer Cell. 2015; 27(2):298-311 [PubMed] Related Publications
Blastemal histology in chemotherapy-treated pediatric Wilms tumors (nephroblastoma) is associated with adverse prognosis. To uncover the underlying tumor biology and find therapeutic leads for this subgroup, we analyzed 58 blastemal type Wilms tumors by exome and transcriptome sequencing and validated our findings in a large replication cohort. Recurrent mutations included a hotspot mutation (Q177R) in the homeo-domain of SIX1 and SIX2 in tumors with high proliferative potential (18.1% of blastemal cases); mutations in the DROSHA/DGCR8 microprocessor genes (18.2% of blastemal cases); mutations in DICER1 and DIS3L2; and alterations in IGF2, MYCN, and TP53, the latter being strongly associated with dismal outcome. DROSHA and DGCR8 mutations strongly altered miRNA expression patterns in tumors, which was functionally validated in cell lines expressing mutant DROSHA.

Walz AL, Ooms A, Gadd S, et al.
Recurrent DGCR8, DROSHA, and SIX homeodomain mutations in favorable histology Wilms tumors.
Cancer Cell. 2015; 27(2):286-97 [PubMed] Related Publications
We report the most common single-nucleotide substitution/deletion mutations in favorable histology Wilms tumors (FHWTs) to occur within SIX1/2 (7% of 534 tumors) and microRNA processing genes (miRNAPGs) DGCR8 and DROSHA (15% of 534 tumors). Comprehensive analysis of 77 FHWTs indicates that tumors with SIX1/2 and/or miRNAPG mutations show a pre-induction metanephric mesenchyme gene expression pattern and are significantly associated with both perilobar nephrogenic rests and 11p15 imprinting aberrations. Significantly decreased expression of mature Let-7a and the miR-200 family (responsible for mesenchymal-to-epithelial transition) in miRNAPG mutant tumors is associated with an undifferentiated blastemal histology. The combination of SIX and miRNAPG mutations in the same tumor is associated with evidence of RAS activation and a higher rate of relapse and death.

Shen J, Hung MC
Signaling-mediated regulation of MicroRNA processing.
Cancer Res. 2015; 75(5):783-91 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
miRNAs are important regulatory elements for gene expression that are involved in diverse physiologic and pathologic processes. Canonical miRNA biogenesis consists of a two-step processing, from primary transcripts (pri-miRNA) to precursor miRNAs (pre-miRNA) mediated by Drosha in the nucleus and from pre-miRNAs to mature miRNAs mediated by Dicer in the cytoplasm. Various routes of miRNA maturation that are tightly regulated by signaling cascades and specific to an individual or a subclass of miRNAs have been recently identified. Here, we review the current findings in signaling-mediated miRNA processing as well as their potential clinical relevance in cancer.

Erler P, Keutgen XM, Crowley MJ, et al.
Dicer expression and microRNA dysregulation associate with aggressive features in thyroid cancer.
Surgery. 2014; 156(6):1342-50; discussion 1350 [PubMed] Related Publications
BACKGROUND: Altered miRNA expression and down-regulation of Dicer has been shown in various cancers. We investigated Dicer expression and global miRNA environment in correlation with malignant features of thyroid tumors.
METHODS: Dicer gene expression was assessed for 22 normal thyroids, 16 follicular adenomas, 28 papillary thyroid cancers (PTCs), 10 tall-cell variants of PTC, 11 follicular variants of PTC, as well as the four thyroid cell lines BCPAP, TPC1, KTC1, and TAD2 via quantitative polymerase chain reaction. BRAF((V600E)) mutation screening was completed for 31 neoplasms. Next-generation sequencing was performed on a subset of PTC and normal thyroid. Protein levels were assessed via Western blotting and immunohistochemistry.
RESULTS: Dicer mRNA was down-regulated in malignant thyroid samples and cell lines compared with normal tissues, benign neoplasms, and the fetal cell line TAD2. Decreased Dicer gene expression in malignant tissues was correlated greatly with aggressive features: extrathyroidal extension, angiolymphatic invasion, multifocality, lymph node and distant metastasis, recurrence, and BRAF((V600E)) mutation. Conversely, increased levels of Dicer protein were observed in malignant tissues and cell lines. Sequencing yielded 19 differentially expressed miRNAs. Eight samples had a nonsignificant a global down-regulation in malignant tissues.
CONCLUSION: Dysregulation of Dicer and possibly altered expression of miRNAs are associated with aggressive features in thyroid cancers. These findings suggest that disruption in normal miRNA processing involving Dicer may play a role in thyroid cancer progression.

Melo SA, Sugimoto H, O'Connell JT, et al.
Cancer exosomes perform cell-independent microRNA biogenesis and promote tumorigenesis.
Cancer Cell. 2014; 26(5):707-21 [PubMed] Article available free on PMC after 10/11/2015 Related Publications
Exosomes are secreted by all cell types and contain proteins and nucleic acids. Here, we report that breast cancer associated exosomes contain microRNAs (miRNAs) associated with the RISC-Loading Complex (RLC) and display cell-independent capacity to process precursor microRNAs (pre-miRNAs) into mature miRNAs. Pre-miRNAs, along with Dicer, AGO2, and TRBP, are present in exosomes of cancer cells. CD43 mediates the accumulation of Dicer specifically in cancer exosomes. Cancer exosomes mediate an efficient and rapid silencing of mRNAs to reprogram the target cell transcriptome. Exosomes derived from cells and sera of patients with breast cancer instigate nontumorigenic epithelial cells to form tumors in a Dicer-dependent manner. These findings offer opportunities for the development of exosomes based biomarkers and therapies.

Khan S, Greco D, Michailidou K, et al.
MicroRNA related polymorphisms and breast cancer risk.
PLoS One. 2014; 9(11):e109973 [PubMed] Article available free on PMC after 10/11/2015 Related Publications
Genetic variations, such as single nucleotide polymorphisms (SNPs) in microRNAs (miRNA) or in the miRNA binding sites may affect the miRNA dependent gene expression regulation, which has been implicated in various cancers, including breast cancer, and may alter individual susceptibility to cancer. We investigated associations between miRNA related SNPs and breast cancer risk. First we evaluated 2,196 SNPs in a case-control study combining nine genome wide association studies (GWAS). Second, we further investigated 42 SNPs with suggestive evidence for association using 41,785 cases and 41,880 controls from 41 studies included in the Breast Cancer Association Consortium (BCAC). Combining the GWAS and BCAC data within a meta-analysis, we estimated main effects on breast cancer risk as well as risks for estrogen receptor (ER) and age defined subgroups. Five miRNA binding site SNPs associated significantly with breast cancer risk: rs1045494 (odds ratio (OR) 0.92; 95% confidence interval (CI): 0.88-0.96), rs1052532 (OR 0.97; 95% CI: 0.95-0.99), rs10719 (OR 0.97; 95% CI: 0.94-0.99), rs4687554 (OR 0.97; 95% CI: 0.95-0.99, and rs3134615 (OR 1.03; 95% CI: 1.01-1.05) located in the 3' UTR of CASP8, HDDC3, DROSHA, MUSTN1, and MYCL1, respectively. DROSHA belongs to miRNA machinery genes and has a central role in initial miRNA processing. The remaining genes are involved in different molecular functions, including apoptosis and gene expression regulation. Further studies are warranted to elucidate whether the miRNA binding site SNPs are the causative variants for the observed risk effects.

Sioud M
RNA interference: mechanisms, technical challenges, and therapeutic opportunities.
Methods Mol Biol. 2015; 1218:1-15 [PubMed] Related Publications
The ability to inhibit gene expression via RNA interference (RNAi) has a broad therapeutic potential for various human diseases such as infections and cancers. Recent advances in mechanistic understanding of RNAi have improved the design of functional small interfering (si) RNAs with superior potency and specificity. With respect to delivery, new developments in delivery strategies have facilitated preclinical and clinical siRNA applications. This review provides valuable insights to guide the design and delivery of therapeutic siRNAs.

Molina-Pinelo S, Carnero A, Rivera F, et al.
MiR-107 and miR-99a-3p predict chemotherapy response in patients with advanced colorectal cancer.
BMC Cancer. 2014; 14:656 [PubMed] Article available free on PMC after 10/11/2015 Related Publications
BACKGROUND: MicroRNAs (miRNAs) are involved in numerous biological and pathological processes including colorectal cancer (CRC). The aim of our study was to evaluate the ability of miRNA expression patterns to predict chemotherapy response in a cohort of 78 patients with metastatic CRC (mCRC).
METHODS: We examined expression levels of 667 miRNAs in the training cohort and evaluated their potential association with relevant clinical endpoints. We identified a miRNA profile that was analysed by RT-qPCR in an independent cohort. For a set of selected miRNAs, bioinformatic target predictions and pathway analysis were also performed.
RESULTS: Eight miRNAs (let-7 g*, miR-107, miR-299-5p, miR-337-5p, miR-370, miR-505*, miR-889 and miR-99a-3p) were significant predictors of response to chemotherapy in the training cohort. In addition, overexpression of miR-107, miR-337-5p and miR-99a-3p, and underexpression of miR-889, were also significantly associated with improved progression-free and/or overall survival. MicroRNA-107 and miR-99a-3p were further validated in an independent cohort as predictive markers for chemotherapy response. In addition, an inverse correlation was confirmed in our study population between miR-107 levels and mRNA expression of several potential target genes (CCND1, DICER1, DROSHA and NFKB1).
CONCLUSIONS: MiR-107 and miR-99a-3p were validated as predictors of response to standard fluoropyrimidine-based chemotherapy in patients with mCRC.

Han C, Liu Y, Wan G, et al.
The RNA-binding protein DDX1 promotes primary microRNA maturation and inhibits ovarian tumor progression.
Cell Rep. 2014; 8(5):1447-60 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
Posttranscriptional maturation is a critical step in microRNA (miRNA) biogenesis that determines mature miRNA levels. In addition to core components (Drosha and DGCR8 [DiGeorge syndrome critical region gene 8]) in the microprocessor, regulatory RNA-binding proteins may confer the specificity for recruiting and processing of individual primary miRNAs (pri-miRNAs). Here, we identify DDX1 as a regulatory protein that promotes the expression of a subset of miRNAs, including five members in the microRNA-200 (miR-200) family and four miRNAs in an eight-miRNA signature of a mesenchymal ovarian cancer subtype. A majority of DDX1-dependent miRNAs are induced after DNA damage. This induction is facilitated by the ataxia telangiectasia mutated (ATM)-mediated phosphorylation of DDX1. Inhibiting DDX1 promotes ovarian tumor growth and metastasis in a syngeneic mouse model. Analysis of The Cancer Genome Atlas (TCGA) reveals that low DDX1 levels are associated with poor clinical outcome in patients with serous ovarian cancer. These findings suggest that DDX1 is a key modulator in miRNA maturation and ovarian tumor suppression.

Foulkes WD, Priest JR, Duchaine TF
DICER1: mutations, microRNAs and mechanisms.
Nat Rev Cancer. 2014; 14(10):662-72 [PubMed] Related Publications
Dicer is central to microRNA-mediated silencing and several other RNA interference phenomena that are profoundly embedded in cancer gene networks. Most recently, both germline and somatic mutations in DICER1 have been identified in diverse types of cancer. Although some of the mutations clearly reduce the dosage of this key enzyme, others dictate surprisingly specific changes in select classes of small RNAs. This Review reflects on the molecular properties of the Dicer enzymes in small RNA silencing pathways, and rationalizes the newly discovered mutations on the basis of the activities and functions of its determinants.

De Ruyck K, Duprez F, Ferdinande L, et al.
A let-7 microRNA polymorphism in the KRAS 3'-UTR is prognostic in oropharyngeal cancer.
Cancer Epidemiol. 2014; 38(5):591-8 [PubMed] Related Publications
INTRODUCTION: This study aimed to investigate the effect of genetic polymorphisms in miRNA sequences, miRNA target genes and miRNA processing genes as additional biomarkers to HPV for prognosis in oropharyngeal squamous cell carcinoma (OPSCC) patients. Secondarily, the prevalence of HPV-associated OPSCC in a European cohort was mapped.
METHODS: OPSCC patients (n=122) were genotyped for ten genetic polymorphisms in pre-miRNAs (pre-mir-146a, pre-mir-196a2), in miRNA biosynthesis genes (Drosha, XPO5) and in miRNA target genes (KRAS, SMC1B). HPV status was assessed by p16 immunohistochemistry (IHC) and high-risk HPV in situ hybridization (ISH) or by p16 IHC and PCR followed by enzyme-immunoassay (EIA). Overall and disease specific survival were analysed using Kaplan-Meier plots (log-rank test). Cox proportional hazard model was used to calculate hazard ratios (HR).
RESULTS: The overall HPV prevalence rate in our Belgian/Dutch cohort was 27.9%. Patients with HPV(+) tumours had a better 5-years overall survival (78% vs. 46%, p=0.001) and a better 5-years disease specific survival (90% vs. 70%, p=0.016) compared to patients with HPV(-) tumours. In multivariate Cox analysis including clinical, treatment and genetic parameters, HPV negativity (HR=3.89, p=0.005), advanced T-stage (HR=1.81, p=0.050), advanced N-stage (HR=5.86, p=0.001) and >10 pack-years of smoking (HR=3.45, p=0.012) were significantly associated with reduced overall survival. The variant G-allele of the KRAS-LCS6 polymorphism was significantly associated with a better overall survival (HR=0.40, p=0.031).
CONCLUSIONS: Our results demonstrate that OPSCC patients with the KRAS-LCS6 variant have a better outcome and suggest that this variant may be used as a prognostic biomarker for OPSCC.

Fletcher CE, Dart DA, Bevan CL
Interplay between steroid signalling and microRNAs: implications for hormone-dependent cancers.
Endocr Relat Cancer. 2014; 21(5):R409-29 [PubMed] Related Publications
Hormones are key drivers of cancer development. To date, interest has largely been focussed on the classical model of hormonal gene regulation, but there is increasing evidence for a role of hormone signalling pathways in post-translational regulation of gene expression. In particular, a complex and dynamic network of bi-directional interactions with microRNAs (miRs) at all stages of biogenesis and during target gene repression is emerging. miRs, which act mainly by negatively regulating gene expression through association with 3'-UTRs of mRNA species, are increasingly understood to be important in development, normal physiology and pathogenesis. Given recent demonstrations of altered miR profiles in a diverse range of cancers, their ability to function as oncogenes or tumour suppressors, and hormonal regulation of miRs, understanding mechanisms by which miRs are generated and regulated is vitally important. miRs are transcribed by RNA polymerase II and then processed in the nucleus by the Drosha-containing Microprocessor complex and in the cytoplasm by Dicer, before mature miRs are incorporated into the RNA-induced silencing complex. It is increasingly evident that multiple cellular signalling pathways converge upon the miR biogenesis cascade, adding further layers of regulatory complexity to modulate miR maturation. This review summarises recent advances in identification of novel components and regulators of the Microprocessor and Dicer complexes, with particular emphasis on the role of hormone signalling pathways in regulating their activity. Understanding hormone regulation of miR production and how this is perturbed in cancer are critical for the development of miR-based therapeutics and biomarkers.

Bandara V, Michael MZ, Gleadle JM
Hypoxia represses microRNA biogenesis proteins in breast cancer cells.
BMC Cancer. 2014; 14:533 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
BACKGROUND: Cancers are commonly characterised by hypoxia and also by global reductions in the levels of mature microRNAs. We have examined the hypothesis that hypoxia might mediate this reduction through repressive effects on microRNA biogenesis proteins.
METHODS: Breast cancer cell lines were exposed to hypoxia and manipulations of hypoxia inducible factor (HIF) and HIF hydroxylase activity. The effects of hypoxia on the mRNA and protein levels of enzymes involved in microRNA biogenesis (Dicer, Drosha, TARPB2, DCGR8, XPO5) was determined by RT PCR and immunoblotting. The effect of hypoxia on microRNAs was determined with microarray studies, RT PCR and reporter assays.
RESULTS: In breast cancer lines there was significant reduction of Dicer mRNA and protein levels in cells exposed to hypoxia. This effect was independent of HIF but dependent on the HIF hydroxylase PHD2 and was partly mediated by feedback effects via microRNAs. Furthermore, several other proteins with critical roles in microRNA biogenesis (Drosha, TARBP2 and DCGR8) also showed significant and co-ordinated repression under hypoxic conditions. Despite these substantial alterations no, or modest, changes were observed in mature microRNA production.
CONCLUSION: These observations provide further and important interfaces between oxygen availability and gene expression and a potential mechanistic explanation for the reduced levels of microRNAs observed in some cancers. They provide further support for the existence of feedback mechanisms in the regulation of the microRNA biogenesis pathway and the relative stability of microRNAs.

Boele J, Persson H, Shin JW, et al.
PAPD5-mediated 3' adenylation and subsequent degradation of miR-21 is disrupted in proliferative disease.
Proc Natl Acad Sci U S A. 2014; 111(31):11467-72 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
Next-generation sequencing experiments have shown that microRNAs (miRNAs) are expressed in many different isoforms (isomiRs), whose biological relevance is often unclear. We found that mature miR-21, the most widely researched miRNA because of its importance in human disease, is produced in two prevalent isomiR forms that differ by 1 nt at their 3' end, and moreover that the 3' end of miR-21 is posttranscriptionally adenylated by the noncanonical poly(A) polymerase PAPD5. PAPD5 knockdown caused an increase in the miR-21 expression level, suggesting that PAPD5-mediated adenylation of miR-21 leads to its degradation. Exoribonuclease knockdown experiments followed by small-RNA sequencing suggested that PARN degrades miR-21 in the 3'-to-5' direction. In accordance with this model, microarray expression profiling demonstrated that PAPD5 knockdown results in a down-regulation of miR-21 target mRNAs. We found that disruption of the miR-21 adenylation and degradation pathway is a general feature in tumors across a wide range of tissues, as evidenced by data from The Cancer Genome Atlas, as well as in the noncancerous proliferative disease psoriasis. We conclude that PAPD5 and PARN mediate degradation of oncogenic miRNA miR-21 through a tailing and trimming process, and that this pathway is disrupted in cancer and other proliferative diseases.

de Kock L, Sabbaghian N, Druker H, et al.
Germ-line and somatic DICER1 mutations in pineoblastoma.
Acta Neuropathol. 2014; 128(4):583-95 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
Germ-line RB-1 mutations predispose to pineoblastoma (PinB), but other predisposing genetic factors are not well established. We recently identified a germ-line DICER1 mutation in a child with a PinB. This was accompanied by loss of heterozygosity (LOH) of the wild-type allele within the tumour. We set out to establish the prevalence of DICER1 mutations in an opportunistically ascertained series of PinBs. Twenty-one PinB cases were studied: Eighteen cases had not undergone previous testing for DICER1 mutations; three patients were known carriers of germ-line DICER1 mutations. The eighteen PinBs were sequenced by Sanger and/or Fluidigm-based next-generation sequencing to identify DICER1 mutations in blood gDNA and/or tumour gDNA. Testing for somatic DICER1 mutations was also conducted on one case with a known germ-line DICER1 mutation. From the eighteen PinBs, we identified four deleterious DICER1 mutations, three of which were germ line in origin, and one for which a germ line versus somatic origin could not be determined; in all four, the second allele was also inactivated leading to complete loss of DICER1 protein. No somatic DICER1 RNase IIIb mutations were identified. One PinB arising in a germ-line DICER1 mutation carrier was found to have LOH. This study suggests that germ-line DICER1 mutations make a clinically significant contribution to PinB, establishing DICER1 as an important susceptibility gene for PinB and demonstrates PinB to be a manifestation of a germ-line DICER1 mutation. The means by which the second allele is inactivated may differ from other DICER1-related tumours.

Tian F, Yourek G, Shi X, Yang Y
The development of Wilms tumor: from WT1 and microRNA to animal models.
Biochim Biophys Acta. 2014; 1846(1):180-7 [PubMed] Related Publications
Wilms tumor recapitulates the development of the kidney and represents a unique opportunity to understand the relationship between normal and tumor development. This has been illustrated by the findings that mutations of Wnt/β-catenin pathway-related WT1, β-catenin, and WTX together account for about one-third of Wilms tumor cases. While intense efforts are being made to explore the genetic basis of the other two-thirds of tumor cases, it is worth noting that, epigenetic changes, particularly the loss of imprinting of the DNA region encoding the major fetal growth factor IGF2, which results in its biallelic over-expression, are closely associated with the development of many Wilms tumors. Recent investigations also revealed that mutations of Drosha and Dicer, the RNases required for miRNA generation, and Dis3L2, the 3'-5' exonuclease that normally degrades miRNAs and mRNAs, could cause predisposition to Wilms tumors, demonstrating that miRNA can play a pivotal role in Wilms tumor development. Interestingly, Lin28, a direct target of miRNA let-7 and potent regulator of stem cell self-renewal and differentiation, is significantly elevated in some Wilms tumors, and enforced expression of Lin28 during kidney development could induce Wilms tumor. With the success in establishing mice nephroblastoma models through over-expressing IGF2 and deleting WT1, and advances in understanding the ENU-induced rat model, we are now able to explore the molecular and cellular mechanisms induced by these genetic, epigenetic, and miRNA alterations in animal models to understand the development of Wilms tumor. These animal models may also serve as valuable systems to assess new treatment targets and strategies for Wilms tumor.

Cao JX, Li SY, An GS, et al.
E2F1-regulated DROSHA promotes miR-630 biosynthesis in cisplatin-exposed cancer cells.
Biochem Biophys Res Commun. 2014; 450(1):470-5 [PubMed] Related Publications
DNA damage may regulate microRNA (miRNA) biosynthesis at the levels of miRNA transcription, processing and maturation. Although involvement of E2F1 in the regulation of miRNA gene activation in response to DNA damage has been documented, little is known about the role of E2F1 in miRNA processing. In this study we demonstrate that E2F1 enhances miR-630 biosynthesis under cisplatin (CIS) exposure through promoting DROSHA-mediated pri-miR-630 processing. Northern blot and RT-qPCR revealed that CIS exposure caused not only an increase in pri-miR-630 but also much more increase in pre-miR-630 and mature miR-630. The increases in pri-miR-630 and pre-miR-630 expression in unmatched proportion indicated that primary transcript processing was involved in CIS-stimulated miR-630 biosynthesis. Furthermore, combination of reporter enzyme assay with mutation and over-expression of E2F1 showed that induction of DROSHA promoted miR-630 expression, in which CIS-induced E2F1 activated DROSHA gene expression by recognizing and binding two E2F1 sites at the positions -214/-207 and -167/-160 of the DROSHA promoter. The increased binding of E2F1 to the DROSHA promoter in CIS-exposed cells was further evidenced by chromatin immunoprecipitation assay. Together, E2F1-regulated DROSHA promotes pri-miR-630 processing, thereby, contributes to CIS-stimulated miR-630 expression. The involvement of E2F1-dependent DROSHA activation in pri-miRNA processing under DNA damage stress will provide further insight into the regulation of miRNA biosynthesis. These data also give us a deeper understanding of E2F1 role in response to DNA damage.

Pugh TJ, Yu W, Yang J, et al.
Exome sequencing of pleuropulmonary blastoma reveals frequent biallelic loss of TP53 and two hits in DICER1 resulting in retention of 5p-derived miRNA hairpin loop sequences.
Oncogene. 2014; 33(45):5295-302 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
Pleuropulmonary blastoma is a rare childhood malignancy of lung mesenchymal cells that can remain dormant as epithelial cysts or progress to high-grade sarcoma. Predisposing germline loss-of-function DICER1 variants have been described. We sought to uncover additional contributors through whole exome sequencing of 15 tumor/normal pairs, followed by targeted resequencing, miRNA analysis and immunohistochemical analysis of additional tumors. In addition to frequent biallelic loss  of TP53 and mutations of NRAS or BRAF in some cases, each case had compound disruption of DICER1: a germline (12 cases) or somatic (3 cases) loss-of-function variant plus a somatic missense mutation in the RNase IIIb domain. 5p-Derived microRNA (miRNA) transcripts retained abnormal precursor miRNA loop sequences normally removed by DICER1. This work both defines a genetic interaction landscape with DICER1 mutation and provides evidence for alteration in miRNA transcripts as a consequence of DICER1 disruption in cancer.

Geng L, Sun B, Gao B, et al.
MicroRNA-103 promotes colorectal cancer by targeting tumor suppressor DICER and PTEN.
Int J Mol Sci. 2014; 15(5):8458-72 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
MicroRNAs (miRNAs) are a class of small, noncoding RNAs that act as key regulators in various physiological and pathological processes. However, the regulatory mechanisms for miRNAs in colorectal cancer remain largely unknown. Here, we found that miR-103 is up-regulated in colorectal cancer and its overexpression is closely associated with tumor proliferation and migration. In addition, repressing the expression of miR-103 apparently inhibits colorectal cancer cell proliferation and migration in vitro and HCT-116 xenograft tumor growth in vivo. Subsequent software analysis and dual-luciferase reporter assay identified two tumor suppressor genes DICER and PTEN as direct targets of miR-103, and up-regulation of DICER and PTEN obtained similar results to that occurred in the silencing of miR-103. In addition, restoration of DICER and PTEN can inhibit miR-103-induced colorectal cancer cell proliferation and migration. Our data collectively demonstrate that miR-103 is an oncogene miRNA that promotes colorectal cancer proliferation and migration through down-regulation of the tumor suppressor genes DICER and PTEN. Thus, miR-103 may represent a new potential diagnostic and therapeutic target for colorectal cancer treatment.

Sahakitrungruang T, Srichomthong C, Pornkunwilai S, et al.
Germline and somatic DICER1 mutations in a pituitary blastoma causing infantile-onset Cushing's disease.
J Clin Endocrinol Metab. 2014; 99(8):E1487-92 [PubMed] Related Publications
CONTEXT: Pituitary blastoma causing Cushing's syndrome in infancy is very rare, and its molecular pathomechanism is not well understood.
OBJECTIVE: Our objective was to identify genetic changes of a pituitary blastoma causing infantile-onset Cushing's syndrome in a Thai girl without a family history of cancers.
METHODS: Genomic DNA from both leukocytes and tumor tissues was used for whole-exome sequencing (WES) and Sanger sequencing of DICER1. The cDNA reverse-transcribed from RNA extracted from both leukocytes and tumor tissues was used for Sanger sequencing, quantitative real-time PCR (qRT-PCR), and pyrosequencing of DICER1.
RESULTS: WES of leukocytes identified a novel heterozygous c.3046delA (p.S1016VfsX1065) mutation in the DICER1 gene. WES of the tumor tissues detected the same frameshift germline mutation and another novel somatic missense c.5438A→T (p.E1813V) mutation. Both mutations were validated by Sanger sequencing. Quantitative real-time PCR revealed that the DICER1 mRNA levels of the tumor tissues were 54% compared with those of her leukocytes. Pyrosequencing showed that the deletion allele constituted 12% and 0% of the DICER1 cDNA of the proband's leukocytes and tumor tissues, respectively.
CONCLUSION: Our study extends the phenotypic and mutational spectrum of DICER1 mutations to include infantile-onset Cushing's disease and 2 novel mutations. Loss of function of both DICER1 alleles appears to be crucial to initiate tumor development.

Banno K, Yanokura M, Iida M, et al.
Application of microRNA in diagnosis and treatment of ovarian cancer.
Biomed Res Int. 2014; 2014:232817 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
Ovarian cancer has a poor prognosis because early detection is difficult and recurrent ovarian cancer is usually drug-resistant. The morbidity and mortality of ovarian cancer are high worldwide and new methods of diagnosis and therapy are needed. MicroRNAs (miRNAs) are posttranscriptional regulators of gene expression that are involved in carcinogenesis, metastasis, and invasion. Thus, miRNAs are likely to be useful as diagnostic and prognostic biomarkers and for cancer therapy. Many miRNAs have altered expression in ovarian cancer compared to normal ovarian tissues and these changes may be useful for diagnosis and treatment. For example, deficiencies of enzymes including Dicer and Drosha that are required for miRNA biogenesis may be adverse prognostic factors; miRNAs such as miR-214 and miR-31, which are involved in drug resistance, and the miR-200 family, which is implicated in metastasis, may serve as biomarkers; and transfection of downregulated miRNAs and inhibition of upregulated miRNAs may be effective for treatment of ovarian cancer. Chemotherapy targeting epigenetic mechanisms associated with miRNAs may also be effective to reverse gene silencing.

Pyfferoen L, Mestdagh P, Vergote K, et al.
Lung tumours reprogram pulmonary dendritic cell immunogenicity at the microRNA level.
Int J Cancer. 2014; 135(12):2868-77 [PubMed] Related Publications
Lung cancer arises in a context of tumour-induced immune suppression. Dendritic cells (DCs) are central players in the induction of anti-tumoural immunity, providing critical signals that drive the induction of cytotoxic T-cell responses. Meanwhile, microRNAs are associated with tumour development as well as immune regulation. We postulated that lung tumours escape immune control by reprogramming DC immunogenicity at the microRNA level. Using an orthotopic model of lung cancer, we first identified the DC population responsible for transport and cross-presentation of lung tumour-derived antigens to naïve T cells in the draining mediastinal lymph nodes (LNs). Profiling the full microRNA repertoire of these DCs revealed a restricted set of microRNAs that was consistently dysregulated in the presence of lung tumours, with miR-301a as one of the top upregulated transcripts. Overexpression of miR-301a in DCs suppressed IL-12 secretion, decreased IFN-γ release from antigen-specific cytotoxic T cells, and shifted antigen-specific T helper cytokine profile away from IFN-γ towards IL-13 and IL-17A-secreting T cells. Strikingly, DC-selective Dicer1 gene deletion resulted in delayed lung tumour growth and a survival benefit. Taken together, our data reveal that lung tumours induce an immunosuppressive microRNA signature in pulmonary DCs. Interfering with the DC-intrinsic capacity to remodel microRNA repertoires affects lung tumour outcome.

He L, Wang HY, Zhang L, et al.
Prognostic significance of low DICER expression regulated by miR-130a in cervical cancer.
Cell Death Dis. 2014; 5:e1205 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
Dicer is crucial for the maturation of microRNAs (miRNAs) and its dysregulation may contribute to tumor initiation and progression. The study explored the clinical implications of Dicer and its post-transcriptional regulation by microRNAs in cervical cancer. qRT-PCR and immunohistochemistry investigated Dicer mRNA and protein levels in cervical cancer tissues. The relationship between Dicer expression and survival was analyzed. MiRNA target prediction identified miRNAs that might target Dicer. Luciferase reporter and gain- or loss-of-function assays were performed. The results showed that 36.7% of cervical cancer cases showed low expression of Dicer mRNA and 63.3% cases showed high expression. At the protein level, 51% cases showed negative expression and 49% cases showed positive expression. Dicer mRNA and protein expressions were significantly associated with distant metastasis and recurrence in cervical cancer (P=0.002 and P=0.012, respectively). Multivariate Cox analysis indicated that low Dicer expression (P=0.016) and tumor stage (P=0.047) were independent predictors. Among the miRNAs predicted to target Dicer, 10 were detected by RT-PCR; their expressions were significantly higher in cervical cancers with lower Dicer expression than in those with higher Dicer expression and were negatively correlated with Dicer expression level (P<0.05). In vitro experiments demonstrated that miR-130a directly targeted Dicer mRNA to enhance migration and invasion in SiHa cells. Finally, survival analysis indicated that higher expression of miR-130a was significantly associated with poor disease-free survival. Taken together, Dicer expression regulated by miR-130a is an important potential prognostic factor in cervical cancer.

Avery-Kiejda KA, Braye SG, Forbes JF, Scott RJ
The expression of Dicer and Drosha in matched normal tissues, tumours and lymph node metastases in triple negative breast cancer.
BMC Cancer. 2014; 14:253 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
BACKGROUND: Breast cancer is the most common malignancy in women world-wide. Triple negative breast cancer (TNBC) is a highly aggressive subtype that lacks expression of hormone receptors for estrogen, progesterone and human epidermal growth factor 2; and is associated with a high propensity for metastatic spread. Several studies have identified critical roles for microRNAs in breast cancer, but the role of two critical enzymes involved in microRNA biogenesis, Dicer and Drosha, is not well understood, particularly with respect to metastatic progression in this subtype.
METHODS: We examined the expression of Dicer and Drosha in a series of invasive 35 TNBCs with matched normal adjacent tissues (n = 18) and lymph node metastases (n = 15) using semi-quantitative real time RT-PCR. The relationship of their expression with clinical features including age at diagnosis, lymph node positivity and tumour size was analysed.
RESULTS: We report that Dicer was significantly decreased while Drosha was significantly increased in tumours when compared to normal adjacent tissues. While there was no difference in Drosha expression in lymph node metastases when compared to the primary tumour, Dicer was significantly increased. There was no correlation between the expression of either Dicer or Drosha to age at diagnosis, lymph node positivity and tumour size.
CONCLUSIONS: In conclusion, Dicer and Drosha are dysregulated in TNBC and matched lymph node metastases however, the clinical relevance of this is still not known. The altered expression of Dicer and Drosha may serve as markers for disrupted miRNA biogenesis in TNBC.

Zhao H, Jin X, Su H, et al.
Down-regulation of Dicer expression in cervical cancer tissues.
Med Oncol. 2014; 31(5):937 [PubMed] Related Publications
Dicer is a component of the MicroRNA-producing machinery. The altered expression of Dicer may play a role in oncogenesis. The purpose of this study was to evaluate the expression of Dicer in cervical cancer tissues and its significance. Cancer tissues, para-cancer tissues and corresponding normal tissues were obtained from 31 cervical cancer patients undergoing surgery. Expression levels of Dicer mRNA were evaluated in these tissues using the real-time reverse transcription PCR. The association of the Dicer expression levels with clinical characteristics was also examined. The expression levels of Dicer mRNA were decreased in 66.7% (18/27) and 76.9% (20/26) of cervical cancer and para-cancer specimens, respectively, compared with corresponding normal tissues. The lower expression levels of Dicer in cancer tissues were associated with advanced tumor stages (p = 0.03) and with metastasis (p = 0.01). The down-regulation of Dicer expression in cancer and para-cancer tissues was observed. The lower expression of Dicer in cancer tissues demonstrated to be associated with tumor stages and metastasis. Future studies with a greater number of tissues to more conclusively determine the extent of low-level expression of Dicer in cervical cancer are warranted.

Klein S, Lee H, Ghahremani S, et al.
Expanding the phenotype of mutations in DICER1: mosaic missense mutations in the RNase IIIb domain of DICER1 cause GLOW syndrome.
J Med Genet. 2014; 51(5):294-302 [PubMed] Article available free on PMC after 11/09/2015 Related Publications
BACKGROUND: Constitutional DICER1 mutations have been associated with pleuropulmonary blastoma, cystic nephroma, Sertoli-Leydig tumours and multinodular goitres, while somatic DICER1 mutations have been reported in additional tumour types. Here we report a novel syndrome termed GLOW, an acronym for its core phenotypic findings, which include Global developmental delay, Lung cysts, Overgrowth and Wilms tumour caused by mutations in the RNase IIIb domain of DICER1.
METHODS AND RESULTS: We performed whole exome sequencing on peripheral mononuclear blood cells of an affected proband and identified a de novo missense mutation in the RNase IIIb domain of DICER1. We confirmed an additional de novo missense mutation in the same domain of an unrelated case by Sanger sequencing. These missense mutations in the RNase IIIb domain of DICER1 are suspected to affect one of four metal binding sites located within this domain. Pyrosequencing was used to determine the relative abundance of mutant alleles in various tissue types. The relative mutation abundance is highest in Wilms tumour and unaffected kidney samples when compared with blood, confirming that the mutation is mosaic. Finally, we performed bioinformatic analysis of microRNAs expressed in murine cells carrying specific Dicer1 RNase IIIb domain metal binding site-associated mutations. We have identified a subset of 3p microRNAs that are overexpressed whose target genes are over-represented in mTOR, MAPK and TGF-β signalling pathways.
CONCLUSIONS: We propose that mutations affecting the metal binding sites of the DICER1 RNase IIIb domain alter the balance of 3p and 5p microRNAs leading to deregulation of these growth signalling pathways, causing a novel human overgrowth syndrome.

Seki M, Yoshida K, Shiraishi Y, et al.
Biallelic DICER1 mutations in sporadic pleuropulmonary blastoma.
Cancer Res. 2014; 74(10):2742-9 [PubMed] Related Publications
Pleuropulmonary blastoma (PPB) is a rare pediatric malignancy whose pathogens are poorly understood. Recent reports suggest that germline mutations in the microRNA-processing enzyme DICER1 may contribute to PPB development. To investigate the genetic basis of this cancer, we performed whole-exome sequencing or targeted deep sequencing of multiple cases of PPB. We found biallelic DICER1 mutations to be very common, more common than TP53 mutations also found in many tumors. Somatic ribonuclease III (RNase IIIb) domain mutations were identified in all evaluable cases, either in the presence or absence of nonsense/frameshift mutations. Most cases had mutated DICER1 alleles in the germline with or without an additional somatic mutation in the remaining allele, whereas other cases displayed somatic mutations exclusively where the RNase IIIb domain was invariably affected. Our results highlight the role of RNase IIIb domain mutations in DICER1 along with TP53 inactivation in PPB pathogenesis.

Gutierrez-Camino A, Lopez-Lopez E, Martin-Guerrero I, et al.
Noncoding RNA-related polymorphisms in pediatric acute lymphoblastic leukemia susceptibility.
Pediatr Res. 2014; 75(6):767-73 [PubMed] Related Publications
BACKGROUND: Evidence for an inherited genetic risk for pediatric acute lymphoblastic leukemia has been provided in several studies. Most of them focused on coding regions. However, those regions represent only 1.5% of the entire genome. In acute lymphoblastic leukemia (ALL), it has been suggested that the expression of microRNAs (miRNAs) is dysregulated, which suggests that they may have a role in ALL risk. Changes in miRNA function may occur through single-nucleotide polymorphisms (SNPs). Therefore, the aim of this study was to evaluate whether polymorphisms in pre-miRNAs, and/or miRNA-processing genes, contribute to a predisposition for childhood ALL.
METHODS: In this study, we analyzed 118 SNPs in pre-miRNAs and miRNA-processing genes in 213 B-cell ALL patients and 387 controls.
RESULTS: We found 11 SNPs significantly associated with ALL susceptibility. These included three SNPs present in miRNA genes (miR-612, miR-499, and miR-449b) and eight SNPs present in six miRNA biogenesis pathway genes (TNRC6B, DROSHA, DGCR8, EIF2C1, CNOT1, and CNOT6). Among the 118 SNPs analyzed, rs12803915 in mir-612 and rs3746444 in mir-499 exhibited a more significant association, with a P value <0.01.
CONCLUSION: The results of this study indicate that SNP rs12803915 located in pre-mir-612, and SNP rs3746444 located in pre-mir-499, may represent novel markers of B-cell ALL susceptibility.

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