DROSHA

Gene Summary

Gene:DROSHA; drosha ribonuclease III
Aliases: RN3, ETOHI2, RNASEN, RANSE3L, RNASE3L, HSA242976
Location:5p13.3
Summary:This gene encodes a ribonuclease (RNase) III double-stranded RNA-specific ribonuclease and subunit of the microprocessor protein complex, which catalyzes the initial processing step of microRNA (miRNA) synthesis. The encoded protein cleaves the stem loop structure from the primary microRNA (pri-miRNA) in the nucleus, yielding the precursor miRNA (pre-miRNA), which is then exported to the cytoplasm for further processing. In a human cell line lacking a functional copy of this gene, canonical miRNA synthesis is reduced. Somatic mutations in this gene have been observed in human patients with kidney cancer. [provided by RefSeq, Sep 2016]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:ribonuclease 3
Source:NCBIAccessed: 16 March, 2017

Ontology:

What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 16 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Latest Publications: DROSHA (cancer-related)

Meurgey A, Descotes F, Mery-Lamarche E, Devouassoux-Shisheboran M
Lack of mutation of DICER1 and FOXL2 genes in microcystic stromal tumor of the ovary.
Virchows Arch. 2017; 470(2):225-229 [PubMed] Related Publications
Microcystic stromal tumors (MCST), first described in 2009 by Irving et al., are rare ovarian neoplasms. The entity was introduced into the 2014 WHO classification of tumors of female reproductive organs in the group of sex cord-stromal tumors, which is rather heterogeneous. We studied three cases of ovarian tumor with the characteristic morphological features and immunohistochemical marker profiles of MCST. The three tumors showed micro, and macrocystic patterns with solid areas, and were composed of small round to spindle-shaped cells, without atypia. The tumors diffusely and strongly expressed CD10, FOXL2, and nuclear β-catenin, but without immmunoreactivity for hormone receptors, calretinin, or inhibin. Genome analyses showed no somatic mutation of exon 1 of the FOXL2 gene and of exons 24 and 25 of DICER1 gene, the latter not having been reported previously. The patients are well, without evidence of tumor progression 1 to 10 years after diagnosis.The absence of FOXL2 and DICER1 gene mutation, along with strong FOXL2 immunoreactivity provides additional evidence to place MCST within pure gonadal stromal rather than sex cord ovarian tumors.

Zhu Y, Cai L, Guo J, et al.
Depletion of Dicer promotes epithelial ovarian cancer progression by elevating PDIA3 expression.
Tumour Biol. 2016; 37(10):14009-14023 [PubMed] Related Publications
Dicer is an essential component of the microRNA (miRNA) processing machinery whose low expression is associated with advanced stage and poor clinical outcome in epithelial ovarian cancer. To investigate the functional relevance of Dicer in epithelial ovarian cancer and to identify its downstream effectors, two-dimensional gel electrophoresis combined with mass spectrometry was used for proteomic profiling. Dicer depletion promoted ovarian cancer cell proliferation and migration accompanied by a global upregulation of proteins. Twenty-six proteins, 7 upregulated and 19 downregulated, were identified. The functions of the identified proteins and their interactions were bioinformatically analyzed. Among them, protein disulfide-isomerase A3 (PDIA3) was considered to be a potential target protein of Dicer. PDIA3 repression by siRNA could significantly relieve the proliferation- and migration-promoting effect mediated by Dicer depletion in vitro and in vivo. Moreover, the miRNAs targeting PDIA3 were decreased in cells with Dicer depletion. In summary, low Dicer expression contributes to epithelial ovarian cancer progression by elevating PDIA3 expression.

Comino-Méndez I, Tejera ÁM, Currás-Freixes M, et al.
ATRX driver mutation in a composite malignant pheochromocytoma.
Cancer Genet. 2016; 209(6):272-7 [PubMed] Related Publications
Pheochromocytomas (PCCs) and paragangliomas (PGLs) are tumors arising from the adrenal medulla and sympathetic/parasympathetic paraganglia, respectively. Approximately 40% of PCCs/PGLs are due to germline mutations in one of 16 susceptibility genes, and a further 30% are due to somatic alterations in 5 main genes. Recently, somatic ATRX mutations have been found in succinate dehydrogenase (SDH)-associated hereditary PCCs/PGLs. In the present study we applied whole-exome sequencing to the germline and tumor DNA of a patient with metastatic composite PCC and no alterations in known PCC/PGL susceptibility genes. A somatic loss-of-function mutation affecting ATRX was identified in tumor DNA. Transcriptional profiling analysis classified the tumor within cluster 2 of PCCs/PGLs (without SDH gene mutations) and identified downregulation of genes involved in neuronal development and homeostasis (NLGN4, CD99 and CSF2RA) as well as upregulation of Drosha, an important gene involved in miRNA and rRNA processing. CpG island methylator phenotype typical of SDH gene-mutated tumors was ruled out, and SNP array data revealed a unique profile of gains and losses. Finally, we demonstrated the presence of alternative lengthening of telomeres in the tumor, probably associated with the failure of ATRX functions. In conclusion, somatic variants affecting ATRX may play a driver role in sporadic PCC/PGL.

Velagapudi SP, Cameron MD, Haga CL, et al.
Design of a small molecule against an oncogenic noncoding RNA.
Proc Natl Acad Sci U S A. 2016; 113(21):5898-903 [PubMed] Free Access to Full Article Related Publications
The design of precision, preclinical therapeutics from sequence is difficult, but advances in this area, particularly those focused on rational design, could quickly transform the sequence of disease-causing gene products into lead modalities. Herein, we describe the use of Inforna, a computational approach that enables the rational design of small molecules targeting RNA to quickly provide a potent modulator of oncogenic microRNA-96 (miR-96). We mined the secondary structure of primary microRNA-96 (pri-miR-96) hairpin precursor against a database of RNA motif-small molecule interactions, which identified modules that bound RNA motifs nearby and in the Drosha processing site. Precise linking of these modules together provided Targaprimir-96 (3), which selectively modulates miR-96 production in cancer cells and triggers apoptosis. Importantly, the compound is ineffective on healthy breast cells, and exogenous overexpression of pri-miR-96 reduced compound potency in breast cancer cells. Chemical Cross-Linking and Isolation by Pull-Down (Chem-CLIP), a small-molecule RNA target validation approach, shows that 3 directly engages pri-miR-96 in breast cancer cells. In vivo, 3 has a favorable pharmacokinetic profile and decreases tumor burden in a mouse model of triple-negative breast cancer. Thus, rational design can quickly produce precision, in vivo bioactive lead small molecules against hard-to-treat cancers by targeting oncogenic noncoding RNAs, advancing a disease-to-gene-to-drug paradigm.

Butkytė S, Čiupas L, Jakubauskienė E, et al.
Splicing-dependent expression of microRNAs of mirtron origin in human digestive and excretory system cancer cells.
Clin Epigenetics. 2016; 8:33 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: An abundant class of intronic microRNAs (miRNAs) undergoes atypical Drosha-independent biogenesis in which the spliceosome governs the excision of hairpin miRNA precursors, called mirtrons. Although nearly 500 splicing-dependent miRNA candidates have been recently predicted via bioinformatic analysis of human RNA-Seq datasets, only a few of them have been experimentally validated. The detailed mechanism of miRNA processing by the splicing machinery and the roles of mirtronic miRNAs in cancer are yet to be uncovered.
METHODS: We experimentally examined whether biogenesis of certain miRNAs is under a splicing control by analyzing their expression levels in response to alterations in the 5'- and 3'-splice sites of a series of intron-containing minigenes carrying appropriate miRNAs. The expression levels of the miRNAs processed from mirtrons were determined by quantitative real-time PCR in five digestive tract (pancreas PANC-1, SU.86.86, T3M4, stomach KATOIII, colon HCT116) and two excretory system (kidney CaKi-1, 786-O) carcinoma cell lines as well as in pancreatic, stomach, and colorectal tumors. Transiently expressed SRSF1 and SRSF2 splicing factors were quantified by western blotting in the nuclear fractions of HCT116 cells.
RESULTS: We found that biogenesis of the human hsa-miR-1227-3p, hsa-miR-1229-3p, and hsa-miR-1236-3p is splicing-dependent; therefore, these miRNAs can be assigned to the class of miRNAs processed by a non-canonical mirtron pathway. The expression analysis revealed a differential regulation of human mirtronic miRNAs in various cancer cell lines and tumors. In particular, hsa-miR-1229-3p is selectively upregulated in the pancreatic and stomach cancer cell lines derived from metastatic sites. Compared with the healthy controls, the expression of hsa-miR-1226-3p was significantly higher in stomach tumors but extensively downregulated in colorectal tumors. Furthermore, we provided evidence that overexpression of SRSF1 or SRSF2 can upregulate the processing of individual mirtronic miRNAs in HCT116 cells.
CONCLUSIONS: An interplay of different splicing factors, such as SRSF1 or SRSF2, may alter the levels of miRNAs of mirtron origin in a cell. Our findings underline the specific expression profiles of mirtronic miRNAs in colorectal, stomach, and pancreatic cancer.

Gu H, Liu M, Ding C, et al.
Hypoxia-responsive miR-124 and miR-144 reduce hypoxia-induced autophagy and enhance radiosensitivity of prostate cancer cells via suppressing PIM1.
Cancer Med. 2016; 5(6):1174-82 [PubMed] Free Access to Full Article Related Publications
Cancer cells in hypoxia usually make adaptive changes in cellular metabolism, such as altered autophagy. This might be a cause of enhanced radioresistance in some types of cancer. In this study, we investigated hypoxia-responsive miRNAs in two prostate cancer cell lines (DU145 and PC3). This study firstly reported that hypoxia induces further downregulation of miR-124 and miR-144, which might be a result of impaired dicer expression. These two miRNAs can simultaneously target 3'UTR of PIM1. Functional study showed that miR-124 or miR-144 overexpression can inhibit hypoxia-induced autophagy and enhance radiosensitivity at least via downregulating PIM1. Therefore, hypoxia induced miR-124 and miR-144 downregulation may contribute to a prosurvival mechanism of prostate cancer cells to hypoxia and irradiation at least through attenuated suppressing of PIM1. This finding presents a potential therapeutic target for prostate cancer.

Durieux E, Descotes F, Mauduit C, et al.
The co-occurrence of an ovarian Sertoli-Leydig cell tumor with a thyroid carcinoma is highly suggestive of a DICER1 syndrome.
Virchows Arch. 2016; 468(5):631-6 [PubMed] Related Publications
The DICER1 gene encodes an endoribonuclease involved in the production of mature microRNAs which regulates gene expression through several mechanisms. Carriers of germline DICER1 mutations are predisposed to a rare cancer syndrome, the DICER1 syndrome. Pleuropulmonary blastoma is the most frequent lesion seen in this syndrome. Thyroid abnormalities are also a common finding, essentially concerning multinodular goiter. However, differentiated thyroid carcinoma is infrequently seen in such pedigrees. In addition to germline DICER1 mutations, specific somatic mutations have been identified in the DICER1 RNase IIIb catalytic domain in several tumor types, including ovarian Sertoli-Leydig cell tumors. We report two cases of differentiated thyroid carcinoma associated with ovarian Sertoli-Leydig cell tumor and with a heterozygous DICER1 gene mutation, occurring in two unrelated young girls without pleuropulmonary blastoma. Both thyroid carcinomas showed an E1813 mutation in exon 25 while the ovarian tumors harboured a somatic mutation in E1705 in exon 24 and a D1709 mutation in exon 25. Our observations confirm that the occurrence of an ovarian Sertoli-Leydig cell tumor with a thyroid carcinoma is highly suggestive of a DICER1 syndrome. We contend that the possibility of a relationship between sporadic thyroid carcinoma in young patients and somatic DICER1 gene mutation needs further investigation.

Gurtner A, Falcone E, Garibaldi F, Piaggio G
Dysregulation of microRNA biogenesis in cancer: the impact of mutant p53 on Drosha complex activity.
J Exp Clin Cancer Res. 2016; 35:45 [PubMed] Free Access to Full Article Related Publications
A widespread decrease of mature microRNAs is often observed in human malignancies giving them potential to act as tumor suppressors. Thus, microRNAs may be potential targets for cancer therapy. The global miRNA deregulation is often the result of defects in the miRNA biogenesis pathway, such as genomic mutation or aberrant expression/localization of enzymes and cofactors responsible of miRNA maturation. Alterations in the miRNA biogenesis machinery impact on the establishment and development of cancer programs. Accumulation of pri-microRNAs and corresponding depletion of mature microRNAs occurs in human cancers compared to normal tissues, strongly indicating an impairment of crucial steps in microRNA biogenesis. In agreement, inhibition of microRNA biogenesis, by depletion of Dicer1 and Drosha, tends to enhance tumorigenesis in vivo. The p53 tumor suppressor gene, TP53, is mutated in half of human tumors resulting in an oncogene with Gain-Of-Function activities. In this review we discuss recent studies that have underlined a role of mutant p53 (mutp53) on the global regulation of miRNA biogenesis in cancer. In particular we describe how a new transcriptionally independent function of mutant p53 in miRNA maturation, through a mechanism by which this oncogene is able to interfere with the Drosha processing machinery, generally inhibits miRNA processing in cancer and consequently impacts on carcinogenesis.

Ren W, Shen S, Sun Z, et al.
Jak-STAT3 pathway triggers DICER1 for proteasomal degradation by ubiquitin ligase complex of CUL4A(DCAF1) to promote colon cancer development.
Cancer Lett. 2016; 375(2):209-20 [PubMed] Related Publications
Chronic intestinal inflammation is closely associated with colon cancer development and STAT3 seems to take center stage in bridging chronic inflammation to colon cancer progress. Here, we discovered that DICER1 was significantly downregulated in response to IL-6 or LPS stimulation and identified a novel mechanism for DICER1 downregulation via proteasomal degradation by ubiquitin ligase complex of CUL4A(DCAF1) in colon cancer cells. Meanwhile, PI3K-AKT signaling pathway phosphorylated DICER1 and contributed to its proteasomal degradation. The regulation of DICER1 by CUL4A(DCAF1) affected cell growth and apoptosis which is controlled by IL-6 activated Jak-STAT3 pathway. Intervention of CUL4A(DCAF1) ubiquitin ligase complex led to fluctuation in expression levels of DICER1 and microRNAs, and thus affected tumor growth in a mouse xenograft model. A panel of microRNAs that were downregulated by IL-6 stimulation was rescued by siRNA-CUL4A, and their predicated functions are involved in regulation of cell proliferation, apoptosis and motility. Furthermore, clinical specimen analysis revealed that decreased DICER1 expression was negatively correlated with STAT3 activation and cancer progression in human colon cancers. DICER1 and p-STAT3 expression levels correlated with 5-year overall survival of colon cancer patients. Consequently, this study proposes that inflammation-induced Jak-STAT3 signaling leads to colon cancer development through proteasomal degradation of DICER1 by ubiquitin ligase complex of CUL4A(DCAF1), which suggests a novel therapeutic opportunity for colon cancer.

Fan Y, Li H, Ma X, et al.
Dicer suppresses the malignant phenotype in VHL-deficient clear cell renal cell carcinoma by inhibiting HIF-2α.
Oncotarget. 2016; 7(14):18280-94 [PubMed] Free Access to Full Article Related Publications
Both the von Hippel-Lindau (VHL)/hypoxia-inducible factor (HIF) pathway and microRNA (miRNA) regulation are important mechanisms underlying the development and progression of clear cell renal cell carcinoma (ccRCC). Here we demonstrate that VHL deficiency leads to downregulation of Dicer and, in turn, defects in the miRNA biogenesis machinery in ccRCCs. Dicer inhibited expression of HIF-2α, which was a direct target of Dicer-dependent miR-182-5p in VHL-deficient ccRCCs. Ectopic Dicer expression in VHL-deficient ccRCCs suppressed tumor growth and angiogenesis by inhibiting HIF-2α both in vitro and in vivo. Reduced Dicer mRNA levels served as an independent prognostic factor for poor survival in patients with VHL-deficient ccRCC. Our results indicate that downregulation of Dicer in VHL-deficient ccRCCs contributes to high levels of HIF-2α and a malignant phenotype, which suggests Dicer could be a useful therapeutic target for managing this disease.

Deng C, Dai R, Li X, Liu F
Genetic variation frequencies in Wilms' tumor: A meta-analysis and systematic review.
Cancer Sci. 2016; 107(5):690-9 [PubMed] Free Access to Full Article Related Publications
Over the last few decades, numerous biomarkers in Wilms' tumor have been confirmed and shown variations in prevalence. Most of these studies were based on small sample sizes. We carried out a meta-analysis of the research published from 1992 to 2015 to obtain more precise and comprehensive outcomes for genetic tests. In the present study, 70 out of 5175 published reports were eligible for the meta-analysis, which was carried out using Stata 12.0 software. Pooled prevalence for gene mutations WT1, WTX, CTNNB1, TP53, MYCN, DROSHA, and DGCR8 was 0.141 (0.104, 0.178), 0.147 (0.110, 0.184), 0.140 (0.100, 0.190), 0.410 (0.214, 0.605), 0.071 (0.041, 0.100), 0.082 (0.048, 0.116), and 0.036 (0.026, 0.046), respectively. Pooled prevalence of loss of heterozygosity at 1p, 11p, 11q, 16q, and 22q was 0.109 (0.084, 0.133), 0.334 (0.295, 0.373), 0.199 (0.146, 0.252), 0.151 (0.129, 0.172), and 0.148 (0.108, 0.189), respectively. Pooled prevalence of 1q and chromosome 12 gain was 0.218 (0.161, 0.275) and 0.273 (0.195, 0.350), respectively. The limited prevalence of currently known genetic alterations in Wilms' tumors indicates that significant drivers of initiation and progression remain to be discovered. Subgroup analyses indicated that ethnicity may be one of the sources of heterogeneity. However, in meta-regression analyses, no study-level characteristics of indicators were found to be significant. In addition, the findings of our sensitivity analysis and possible publication bias remind us to interpret results with caution.

Zhang X, Gee H, Rose B, et al.
Regulation of the tumour suppressor PDCD4 by miR-499 and miR-21 in oropharyngeal cancers.
BMC Cancer. 2016; 16:86 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The rates of oropharyngeal cancers such as tonsil cancers are increasing. The tumour suppressor protein Programmed Cell Death Protein 4 (PDCD4) has been implicated in the development of various human cancers and small RNAs such as microRNAs (miRNAs) can regulate its expression. However the exact regulation of PDCD4 by multiple miRNAs in oropharyngeal squamous cell carcinoma (SCC) is not well understood.
RESULTS: Using two independent oropharyngeal SCC cohorts with a focus on the tonsillar region, we identified a miRNA profile differentiating SCC tissue from normal. Both miR-21 and miR-499 were highly expressed in tonsil SCC tissues displaying a loss of PDCD4. Interestingly, expression of the miRNA machinery, Dicer1, Drosha, DDX5 (Dead Box Helicase 5) and DGCR8 (DiGeorge Syndrome Critical Region Gene 8) were all elevated by greater than 2 fold in the tonsil SCC tissue. The 3'UTR of PDCD4 contains three binding-sites for miR-499 and one for miR-21. Using a wild-type and truncated 3'UTR of PDCD4, we demonstrated that the initial suppression of PDCD4 was mediated by miR-21 whilst sustained suppression was mediated by miR-499. Moreover the single miR-21 site was able to elicit the same magnitude of suppression as the three miR-499 sites.
CONCLUSION: This study describes the regulation of PDCD4 specifically in tonsil SCC by miR-499 and miR-21 and has documented the loss of PDCD4 in tonsil SCCs. These findings highlight the complex interplay between miRNAs and tumour suppressor gene regulation and suggest that PDCD4 loss may be an important step in tonsillar carcinogenesis.

Eide HA, Halvorsen AR, Bjaanæs MM, et al.
The MYCN-HMGA2-CDKN2A pathway in non-small cell lung carcinoma--differences in histological subtypes.
BMC Cancer. 2016; 16:71 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Extensive research has increased our understanding of the molecular alterations needed for non-small cell lung cancer (NSCLC) development. Deregulation of a pathway including MYCN, HMGA2 and CDKN2A, with the participation of DICER1, is of importance in several solid tumours, and may also be of significance in the pathogenesis of NSCLC.
METHODS: Gene expression of MYCN, HMGA2, CDKN2A and DICER1 were investigated with RT-qPCR in surgically resected NSCLC tumour tissue from 175 patients. Expression of the let-7 microRNA family was performed in 78 adenocarcinomas and 16 matching normal lung tissue samples using microarrays. The protein levels of HMGA2 were determined by immunohistochemistry in 156 tumour samples and the protein expression was correlated with gene expression. Associations between clinical data, including time to recurrence, and expression of mRNA, protein and microRNAs were analysed.
RESULTS: Compared to adenocarcinomas, squamous cell carcinomas had a median 5-fold increase in mRNA expression of HMGA2 (p = 0.003). A positive correlation (r = 0.513, p < 0.010) between HMGA2 mRNA expression and HMGA2 protein expression was seen. At the protein level, 90% of the squamous cell carcinomas expressed high levels of the HMGA2 protein compared to 47% of the adenocarcinomas (p < 0.0001). MYCN was positively correlated with HMGA2 (p < 0.010) and DICER1 mRNA expression (p < 0.010), and the expression of the let-7 microRNAs seemed to be correlated with the genes studied. MYCN expression was associated with time to recurrence in multivariate survival analyses (p = 0.020).
CONCLUSIONS: A significant difference in HMGA2 mRNA expression between the histological subtypes of NSCLC was seen with a higher expression in the squamous cell carcinomas. This was also found at the protein level, and we found a good correlation between the mRNA and the protein expression of HMGA2. Moreover, the expression of MYCN, HMGA2, and DICER1 seems to be correlated to each other and the expression of the let7-genes impacted by their expression. MYCN gene expression seems to be of importance in time to recurrence in this patient cohort with resected NSCLC.

Sahm F, Jakobiec FA, Meyer J, et al.
Somatic mutations of DICER1 and KMT2D are frequent in intraocular medulloepitheliomas.
Genes Chromosomes Cancer. 2016; 55(5):418-27 [PubMed] Related Publications
Intraocular medulloepithelioma (IO-MEPL) is an uncommon embryonal neuroepithelial neoplasm of the eye. Little is known about the cytogenetics, molecular biology, and pathogenesis of this tumor. In the present study we investigated the mutational landscape of 19 IO-MEPL using targeted next-generation sequencing. Routinely prepared paraffin-embedded samples were assessed with high-coverage genome sequencing on the Illumina NextSeq 500 platform using a customized gene panel set covering the coding region of 130 genes. This revealed several notable genomic alterations, including mutations of DICER1 (6 tumors) and KMT2D (also known as MLL2; 5 tumors)-which are frequently recurrent and mutually exclusive molecular events for IO-MEPL. Non-recurrent mutations in the cancer-associated genes BRCA2, BRCA1, NOTCH2, CDH1, and GSE1 were also identified. IO-MEPL samples harboring a DICER1 mutation disclosed few chromosomal alterations and formed a separate DNA methylation cluster, indicating potential differences in genetic and epigenetic events arising perhaps from the presence of this aberration in the tumor genome. The high proportion of recurrent somatic DICER1 and KMT2D mutations in this series of sporadic IO-MEPL points to their likely important roles in the molecular pathogenesis of these rare embryonal tumors, and perhaps suggests the existence of distinct molecular variants of IO-MEPL. Although the precise role of these recurrent mutations in the development of IO-MEPL, and their relationship to pro-oncogenic molecular mechanisms, have yet to be determined, unraveling their roles could eventually be exploited for nonsurgical therapies of these neoplasms.

Spreafico F, Ciceri S, Gamba B, et al.
Chromosomal anomalies at 1q, 3, 16q, and mutations of SIX1 and DROSHA genes underlie Wilms tumor recurrences.
Oncotarget. 2016; 7(8):8908-15 [PubMed] Free Access to Full Article Related Publications
Approximately half of children suffering from recurrent Wilms tumor (WT) develop resistance to salvage therapies. Hence the importance to disclose events driving tumor progression/recurrence. Future therapeutic trials, conducted in the setting of relapsing patients, will need to prioritize targets present in the recurrent lesions. Different studies identified primary tumor-specific signatures associated with poor prognosis. However, given the difficulty in recruiting specimens from recurrent WTs, little work has been done to compare the molecular profile of paired primary/recurrent diseases. We studied the genomic profile of a cohort of eight pairs of primary/recurrent WTs through whole-genome SNP arrays, and investigated known WT-associated genes, including SIX1, SIX2 and micro RNA processor genes, whose mutations have been recently proposed as associated with worse outcome. Through this approach, we sought to uncover anomalies characterizing tumor recurrence, either acquired de novo or already present in the primary disease, and to investigate whether they overlapped with known molecular prognostic signatures. Among the aberrations that we disclosed as potentially acquired de novo in recurrences, some had been already recognized in primary tumors as associated with a higher risk of relapse. These included allelic imbalances of chromosome 1q and of chromosome 3, and CN losses on chromosome 16q. In addition, we found that SIX1 and DROSHA mutations can be heterogeneous events (both spatially and temporally) within primary tumors, and that their co-occurrence might be positively selected in the progression to recurrent disease. Overall, these results provide new insights into genomic and genetic events underlying WT progression/recurrence.

Kubo T, Yanagihara K, Seyama T
In Vivo RNAi Efficacy of Palmitic Acid-Conjugated Dicer-Substrate siRNA in a Subcutaneous Tumor Mouse Model.
Chem Biol Drug Des. 2016; 87(6):811-23 [PubMed] Related Publications
Short interfering RNAs are used in RNA interference technology and are powerful tools for target gene silencing in a sequence-specific manner. In this study, we synthesized Dicer-substrate siRNAs consisting of 27-nt double-stranded RNAs conjugated with palmitic acid at the 5'-end of the sense strand and investigated their RNA interference efficacies in vitro and in vivo. The palmitic acid-conjugated 27-nt DsiRNAs (C16-Dsi27RNAs) were prepared by our simple synthesis strategy and achieved a good yield. C16-Dsi27RNAs showed enhanced in vitro RNA interference potency compared with not only non-modified Dsi27RNAs but also cholesterol-conjugated Dsi27RNAs against both an exogenous enhanced green fluorescent protein and the endogenous vascular endothelial growth factor gene in a human scirrhous-type gastric cancer cell line that stably expressed the enhanced green fluorescent protein gene (GCIY-eGFP). Additionally, C16-Dsi27RNAs had potent gene silencing activity against both enhanced green fluorescent protein and vascular endothelial growth factor as target genes in a subcutaneous tumor mouse model generated from GCIY-eGFP cells administered by intratumoral injection. These results suggest that the C16-Dsi27RNAs will be useful next-generation RNA interference molecules that can overcome the problems associated with RNA interference technology.

Hu J, Sun T, Wang H, et al.
MiR-215 Is Induced Post-transcriptionally via HIF-Drosha Complex and Mediates Glioma-Initiating Cell Adaptation to Hypoxia by Targeting KDM1B.
Cancer Cell. 2016; 29(1):49-60 [PubMed] Free Access to Full Article Related Publications
The hypoxic tumor microenvironment serves as a niche for maintaining the glioma-initiating cells (GICs) that are critical for glioblastoma (GBM) occurrence and recurrence. Here, we report that hypoxia-induced miR-215 is vital for reprograming GICs to fit the hypoxic microenvironment via suppressing the expression of an epigenetic regulator KDM1B and modulating activities of multiple pathways. Interestingly, biogenesis of miR-215 and several miRNAs is accelerated post-transcriptionally by hypoxia-inducible factors (HIFs) through HIF-Drosha interaction. Moreover, miR-215 expression correlates inversely with KDM1B while correlating positively with HIF1α and GBM progression in patients. These findings reveal a direct role of HIF in regulating miRNA biogenesis and consequently activating the miR-215-KDM1B-mediated signaling required for GIC adaptation to hypoxia.

Soares AR, Fernandes N, Reverendo M, et al.
Conserved and highly expressed tRNA derived fragments in zebrafish.
BMC Mol Biol. 2015; 16:22 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Small non-coding RNAs (sncRNAs) are a class of transcripts implicated in several eukaryotic regulatory mechanisms, namely gene silencing and chromatin regulation. Despite significant progress in their identification by next generation sequencing (NGS) we are still far from understanding their full diversity and functional repertoire.
RESULTS: Here we report the identification of tRNA derived fragments (tRFs) by NGS of the sncRNA fraction of zebrafish. The tRFs identified are 18-30 nt long, are derived from specific 5' and 3' processing of mature tRNAs and are differentially expressed during development and in differentiated tissues, suggesting that they are likely produced by specific processing rather than random degradation of tRNAs. We further show that a highly expressed tRF (5'tRF-Pro(CGG)) is cleaved in vitro by Dicer and has silencing ability, indicating that it can enter the RNAi pathway. A computational analysis of zebrafish tRFs shows that they are conserved among vertebrates and mining of publicly available datasets reveals that some 5'tRFs are differentially expressed in disease conditions, namely during infection and colorectal cancer.
CONCLUSIONS: tRFs constitute a class of conserved regulatory RNAs in vertebrates and may be involved in mechanisms of genome regulation and in some diseases.

Osuch-Wojcikiewicz E, Bruzgielewicz A, Niemczyk K, et al.
Association of Polymorphic Variants of miRNA Processing Genes with Larynx Cancer Risk in a Polish Population.
Biomed Res Int. 2015; 2015:298378 [PubMed] Free Access to Full Article Related Publications
Laryngeal cancer (LC) is one of the most prevalent types of head and neck cancer. An increasing interest has been focused on the role of microRNA (miRNAs) in LC development. The study group consisted of 135 larynx cancer patients and 170 cancer-free individuals. Nine polymorphisms of pre-miRNA processing genes, DROSHA (rs6877842), DGCR8 (rs3757, rs417309, and rs1640299), RAN (rs14035), XPO5 (rs11077), DICER1 (rs13078 and rs3742330) and TARBP2 (rs784567), were performed by TaqMan SNP Genotyping Assay. It was found that the frequency of the GT and the TT polymorphic variants of XPO5 gene were higher in LC patients than in controls (p < 0.0001 and p = 0.000183, resp.). In turn, the frequency of the CT genotype of RAN gene was higher in controls than in LC patients (p < 0.0001). The TT and the AG of DICER1 gene (p = 0.034697 for rs13078 and p = 0.0004 for rs3742330) as well as the AG and the GG genotypes of TARBP2 gene (p = 0.008335 and p < 0.0001, resp.) were associated with higher risk of LC occurrence. Our data suggested that polymorphisms of miRNA processing genes might be useful as predictive factors for the LC development.

Eisenberg I, Kotaja N, Goldman-Wohl D, Imbar T
microRNA in Human Reproduction.
Adv Exp Med Biol. 2015; 888:353-87 [PubMed] Related Publications
microRNAs constitute a large family of approximately 21-nucleotide-long, noncoding RNAs. They emerged more than 20 years ago as key posttranscriptional regulators of gene expression. The regulatory role of these small RNA molecules has recently begun to be explored in the human reproductive system. microRNAs have been shown to play an important role in control of reproductive functions, especially in the processes of oocyte maturation, folliculogenesis, corpus luteum function, implantation, and early embryonic development. Knockout of Dicer, the cytoplasmic enzyme that cleaves the pre-miRNA to its mature form, results in postimplantation embryonic lethality in several animal models, attributing to these small RNA vital functions in reproduction and development. Another intriguing characteristic of microRNAs is their presence in body fluids in a remarkably stable form that is protected from endogenous RNase activity. In this chapter we will describe the current knowledge on microRNAs, specifically relating to human gonadal cells. We will focus on their role in the ovarian physiologic process and ovulation dysfunction, regulation of spermatogenesis and male fertility, and putative involvement in human normal and aberrant trophoblast differentiation and invasion through the process of placentation.

Akpa MM, Iglesias D, Chu L, et al.
Wilms Tumor Suppressor, WT1, Cooperates with MicroRNA-26a and MicroRNA-101 to Suppress Translation of the Polycomb Protein, EZH2, in Mesenchymal Stem Cells.
J Biol Chem. 2016; 291(8):3785-95 [PubMed] Free Access to Full Article Related Publications
Hereditary forms of Wilms arise from developmentally arrested clones of renal progenitor cells with biallelic mutations of WT1; recently, it has been found that Wilms tumors may also be associated with biallelic mutations in DICER1 or DROSHA, crucial for miRNA biogenesis. We have previously shown that a critical role for WT1 during normal nephrogenesis is to suppress transcription of the Polycomb group protein, EZH2, thereby de-repressing genes in the differentiation cascade. Here we show that WT1 also suppresses translation of EZH2. All major WT1 isoforms induce an array of miRNAs, which target the 3' UTR of EZH2 and other Polycomb-associated transcripts. We show that the WT1(+KTS) isoform binds to the 5' UTR of EZH2 and interacts directly with the miRNA-containing RISC to enhance post-transcriptional inhibition. These observations suggest a novel mechanism through which WT1 regulates the transition from resting stem cell to activated progenitor cell during nephrogenesis. Our findings also offer a plausible explanation for the fact that Wilms tumors can arise either from loss of WT1 or loss of miRNA processing enzymes.

Cai L, Wang Z, Liu D
Interference with endogenous EZH2 reverses the chemotherapy drug resistance in cervical cancer cells partly by up-regulating Dicer expression.
Tumour Biol. 2016; 37(5):6359-69 [PubMed] Related Publications
Cervical cancer is one of the most common female malignancies in the world, and chemotherapeutic drug resistance is a major obstacle to cancer therapy. Enhancer of zeste homolog 2 (EZH2) is an enzymatic subunit of polycomb repressive complex 2 (PRC2) and catalyzes the repressive histone H3 lysine 27 trimethylation (H3K27me3). However, the role of EZH2 on the chemotherapy drug resistance in cervical cancers remains unclear. In the present study, the cervical carcinoma specimens and paired normal tissue specimens were obtained and the expression of EZH2 was detected by western blotting. The results showed that high levels of EZH2 were detected in cervical carcinoma tissues, compared with paired control tissues (**p < 0.01). Next, three pairs of shRNA specific to EZH2 were designed and used to interfere with endogenous EZH2 expression. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays following treatment with various concentrations of cisplatin in HeLa and HeLa/DDP cells. The MTT assay results showed that knockdown of EZH2 in HeLa/DDP cells caused a 2.29- or 1.83-fold decrease in the cisplatin IC50 values (for shRNA1-EZH2, 34.88 vs. 15.21 μg/mL; p < 0.01; for shRNA3-EZH2, 34.88 vs. 19.09 μg/mL; p < 0.01). The EZH2 activity was also suppressed by 3-deazaneplanocin A (DZNep), EZH2 inhibitor, and the results demonstrated that, meanwhile, DZNep potently inhibited cell viability of HeLa/DDP cells, partly by suppression the levels of EZH2 and H3K27me3, but not H3K27me2, which was detected by western blotting analysis. Moreover, cell migration assay results showed that knockdown of EZH2 decreased cell metastasis of cervical cancer cells. Furthermore, cell cycle was detected by fluorescence-activated cell sorting (FACS) assay and the results demonstrated that interference with EZH2 expression increased the percentage of cells at G0/G1 phase and the HeLa/DDP cells were blocked at G0/G1 phase. Interestingly, western blotting results revealed that higher expression of EZH2 was related with lower level of Dicer in HeLa/DDP cells. Finally, in vivo tumorigenicity experiments results demonstrated that interference with endogenous EZH2 by shRNA specific to EZH2 or inhibition EZH2 by DZNep could significantly increase antitumor effects in nude mice. Thus, inhibiting the levels of endogenous EZH2 effectively reversed the cisplatin resistance and increased the cisplatin sensitivity in cisplatin-resistant HeLa/DDP cells. EZH2 might be a potential target for treating chemotherapeutic drug-resistant cervical cancers.

Jiang FZ, He YY, Wang HH, et al.
Mutant p53 induces EZH2 expression and promotes epithelial-mesenchymal transition by disrupting p68-Drosha complex assembly and attenuating miR-26a processing.
Oncotarget. 2015; 6(42):44660-74 [PubMed] Free Access to Full Article Related Publications
The tumor suppressor p53 and the transcriptional repressor Enhancer of Zeste Homolog 2 (EZH2) have both been implicated in the regulation of epithelial-mesenchymal transition (EMT) and tumor metastasis via their impacts on microRNA expression. Here, we report that mutant p53 (mutp53) promotes EMT in endometrial carcinoma (EC) by disrupting p68-Drosha complex assembly. Overexpression of mutp53 has the opposite effect of wild-type p53 (WTp53), repressing miR-26a expression by reducing pri-miR-26a-1 processing in p53-null EC cells. Re-expression of miR-26a in mutp53 EC cells decreases cell invasion and promotes mesenchymal-epithelial transition (MET). Rescuing miR-26a expression also inhibits EZH2, N-cadherin, Vimentin, and Snail expression and induces E-cadherin expression both in vitro and in vivo. Moreover, patients with higher serum miR-26a levels have a better survival rate. These results suggest that p53 gain-of-function mutations accelerate EC tumor progression and metastasis by interfering with Drosha and p68 binding and pri-miR-26a-1 processing, resulting in reduced miR-26a expression and EZH2 overexpression.

Mehraein Y, Schmid I, Eggert M, et al.
DICER1 syndrome can mimic different genetic tumor predispositions.
Cancer Lett. 2016; 370(2):275-8 [PubMed] Related Publications
DICER1, a RNAse endonuclease involved in the processing of siRNA and microRNA, is known to play a pivotal role in the post-transcriptional regulation of gene expression. Germ line mutations in the DICER1 gene increase the risk for different types of tumors. At present, DICER1 syndrome is an established, though not well defined, member of the group of genetic tumor predisposition syndromes. Here, we report a DICER1 syndrome family with a medical history of different rare tumors mostly occurring at a young age. The tumor spectrum in this family included both DICER1 syndrome-typical forms, such as pleuropulmonary blastoma, multinodular goiter, and cystic nephroma, and not previously reported manifestations, such as pilomatrixoma, and juvenile basal cell carcinoma. The latter tumor types are usually considered to be indicators of familial adenomatous polyposis and basal cell nevus syndrome.

Zhu L, Gao J, Huang K, et al.
miR-34a screened by miRNA profiling negatively regulates Wnt/β-catenin signaling pathway in Aflatoxin B1 induced hepatotoxicity.
Sci Rep. 2015; 5:16732 [PubMed] Free Access to Full Article Related Publications
Aflatoxin-B1 (AFB1), a hepatocarcinogenic mycotoxin, was demonstrated to induce the high rate of hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) participate in the regulation of several biological processes in HCC. However, the function of miRNAs in AFB1-induced HCC has received a little attention. Here, we applied Illumina deep sequencing technology for high-throughout profiling of microRNAs in HepG2 cells lines after treatment with AFB1. Analysis of the differential expression profile of miRNAs in two libraries, we identified 9 known miRNAs and 1 novel miRNA which exhibited abnormal expression. KEGG analysis indicated that predicted target genes of differentially expressed miRNAs are involved in cancer-related pathways. Down-regulated of Drosha, DGCR8 and Dicer 1 indicated an impairment of miRNA biogenesis in response to AFB1. miR-34a was up-regulated significantly, down-regulating the expression of Wnt/β-catenin signaling pathway by target gene β-catenin. Anti-miR-34a can significantly relieved the down-regulated β-catenin and its downstream genes, c-myc and Cyclin D1, and the S-phase arrest in cell cycle induced by AFB1 can also be relieved. These results suggested that AFB1 might down-regulate Wnt/β-catenin signaling pathway in HepG2 cells by up-regulating miR-34a, which may involve in the mechanism of liver tumorigenesis.

Rutter MM, Jha P, Schultz KA, et al.
DICER1 Mutations and Differentiated Thyroid Carcinoma: Evidence of a Direct Association.
J Clin Endocrinol Metab. 2016; 101(1):1-5 [PubMed] Free Access to Full Article Related Publications
CONTEXT: DICER1 germline mutation carriers have an increased predisposition to cancer, such as pleuropulmonary blastoma (PPB) and Sertoli-Leydig cell tumor (SLCT), and a high prevalence of multinodular goiter (MNG). Although differentiated thyroid carcinoma (DTC) has been reported in some DICER1 mutation carriers with PPB treated with chemotherapy, the association of DTC with DICER1 mutations is not well established.
CASE DESCRIPTION: We report a family with DICER1 mutation and familial DTC without a history of chemotherapy. A 12-year-old female (patient A) and her 14-year-old sister (patient B) presented with MNG. Family history was notable for a maternal history of DTC and bilateral ovarian SLCT. Both sisters underwent total thyroidectomy. Pathological examination showed nodular hyperplasia and focal papillary thyroid carcinoma within hyperplastic nodules. Subsequently, patient A developed virilization secondary to a unilateral ovarian SLCT. During her evaluation, an incidental cystic nephroma was also found. Three other siblings had MNG on surveillance ultrasound examination; two had thyroidectomies, and one had two microscopic foci of papillary carcinoma. Patient A, her mother, and four affected siblings had a germline heterozygous pathogenic DICER1 mutation c.5441C>T in exon 25, resulting in an amino acid change from p.Ser1814Leu of DICER1. Somatic DICER1 RNase IIIb missense mutations were identified in thyroid nodules from three of the four siblings.
CONCLUSIONS: This family provides novel insight into an emerging phenotype for DICER1 syndrome, with evidence that germline DICER1 mutations are associated with an increased risk of developing familial DTC, even in the absence of prior treatment with chemotherapy.

Childs-Disney JL, Disney MD
Small Molecule Targeting of a MicroRNA Associated with Hepatocellular Carcinoma.
ACS Chem Biol. 2016; 11(2):375-80 [PubMed] Free Access to Full Article Related Publications
Development of precision therapeutics is of immense interest, particularly as applied to the treatment of cancer. By analyzing the preferred cellular RNA targets of small molecules, we discovered that 5"-azido neomycin B binds the Drosha processing site in the microRNA (miR)-525 precursor. MiR-525 confers invasive properties to hepatocellular carcinoma (HCC) cells. Although HCC is one of the most common cancers, treatment options are limited, making the disease often fatal. Herein, we find that addition of 5"-azido neomycin B and its FDA-approved precursor, neomycin B, to an HCC cell line selectively inhibits production of the mature miRNA, boosts a downstream protein, and inhibits invasion. Interestingly, neomycin B is a second-line agent for hepatic encephalopathy (HE) and bacterial infections due to cirrhosis. Our results provocatively suggest that neomycin B, or second-generation derivatives, may be dual functioning molecules to treat both HE and HCC. Collectively, these studies show that rational design approaches can be tailored to disease-associated RNAs to afford potential lead therapeutics.

Zou Y, Deng W, Wang F, et al.
A novel somatic MAPK1 mutation in primary ovarian mixed germ cell tumors.
Oncol Rep. 2016; 35(2):725-30 [PubMed] Related Publications
A recent exome-sequencing study revealed prevalent mitogen-activated protein kinase 1 (MAPK1) p.E322K mutation in cervical carcinoma. It remains largely unknown whether ovarian carcinomas also harbor MAPK1 mutations. As paralogous gene mutations co‑occur frequently in human malignancies, we analyzed here a total of 263 ovarian carcinomas for the presence of MAPK1 and paralogous MAPK3 mutations by DNA sequencing. A previously unreported MAPK1 p.D321N somatic mutation was identified in 2 out of 18 (11.1%) ovarian mixed germ cell tumors, while no other MAPK1 or MAPK3 mutation was detected in our samples. Of note, OCC‑115, the MAPK1‑mutated sample with bilateral cancerous ovaries affected, harbored MAPK1 mutation in the right ovary while retained the left ovary intact, implicating that the genetic alterations underlying ovarian mixed germ cell tumor may be different, even in patients with similar genetic backgrounds and tumor microenvironments. The results of evolutionary conservation and protein structure modeling analysis implicated that MAPK1 p.D321N mutation may be pathogenic. Additionally, mutations in protein phosphatase 2 regulatory subunit α (PPP2R1A), ring finger protein 43 (RNF43), DNA directed polymerase ε (POLE1), ribonuclease type III (DICER1), CCCTC‑binding factor (CTCF), ribosomal protein L22 (RPL22), DNA methyltransferase 3α (DNMT3A), transformation/transcription domain‑associated protein (TRRAP), isocitrate dehydrogenase (IDH)1 and IDH2 were not detected in ovarian mixed germ cell tumors, implicating these genetic alterations may be not associated with MAPK1 mutation in the development of this malignancy. The present study identified a previously unreported MAPK1 mutation in ovarian mixed germ cell tumors for the first time, and this mutation may be actively involved in the tumorigenesis of this disease.

Kuhlen M, Hönscheid A, Schemme J, et al.
Hodgkin lymphoma as a novel presentation of familial DICER1 syndrome.
Eur J Pediatr. 2016; 175(4):593-7 [PubMed] Related Publications
UNLABELLED: DICER1 germline mutations are associated with an inherited cancer syndrome, most commonly presenting with pleuropulmonary blastoma (PPB), ovarian sex cord tumors, thyroid cysts/goitre, and cystic nephroma. We describe the occurrence of a Hodgkin lymphoma (HL) of the T cell phenotype in a family with DICER1 syndrome. The patient presented with PPB Type I and HL. Immunohistochemical staining of the Hodgkin and Reed-Sternberg cells revealed CD30, TGP, CD2, CD3, CD15, and IRF4 positivity and weekly positivity of PAX5. T cell receptor repertoire analysis suggested HL of T cell origin, which is in contrast to common B cell-derived HL. The mother had been diagnosed with thyroid cysts, one sister had died from a primitive neuroectodermal tumor, and a brother had died from PPB Type III. Two mutational events were revealed in all affected family members; a single bp deletion, c.5299delC, leading to a frameshift and premature stop in exon 24 and a heterozygous variant (c.4616C>T; p.Thr1539Met) located in exon 23 of the DICER1 gene. This variant is predicted to be benign by in silico analysis.
CONCLUSION: Future studies looking for DICER1 mutations in HL cases of the T cell phenotype will be important to confirm its association with constitutional DICER1 syndrome.
WHAT IS KNOWN: • DICER1 germline mutations are associated with an inherited cancer syndrome, most commonly pleuropulmonary blastoma, ovarian sex cord tumors, thyroid cysts/goitre, and cystic nephroma. • Hodgkin lymphoma is one of the most frequent types of malignant lymphomas and typically arises sporadically. T cell-derived Hodgkin lymphomas are exceptionally rare. What is New: • DICER1 syndrome may have an even broader phenotypic spectrum and seems to be associated with rare forms of T cell Hodgkin lymphoma.

Hu S, Liu L, Chang EB, et al.
Butyrate inhibits pro-proliferative miR-92a by diminishing c-Myc-induced miR-17-92a cluster transcription in human colon cancer cells.
Mol Cancer. 2015; 14:180 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Compromised colonic butyrate production resulting from low dietary fiber or altered gut microbiota may promote colon neoplasia. Previous reports indicate these actions are mediated in part by altered levels of miRNAs, including suppressed expression of the oncogenic miR-17-92a cluster. Here, we sought to identify the mechanisms underlying these effects of butyrate in colon cancer.
METHODS: miR-92a levels were measured in archived human colon cancer and adjacent normal colon specimens by microarray and quantitative RT-PCR (qPCR). The effects of butyrate and other histone deacetylase inhibitors (suberoylanilide hydroxamic acid (SAHA) and valproic acid) on primary (pri-miR17-92a), precursor and mature miR-92a were analyzed in HCT-116 and HT-29 human colon cancer cells using qPCR. The effects of butyrate, SAHA and valproic acid on protein levels of c-Myc, Drosha and p57 were measured in HCT-116 cells using immunoblotting. Regulation of C13orf25 promoter activity by butyrate was analyzed by luciferase reporter assay using modified pGL3 constructs containing a wild-type or mutated c-Myc binding site. Expression of c-Myc was modulated using siRNA or adenovirus vectors. p57 mRNA and protein were measured before and after transfection with miR-92a-mimic molecules. Following butyrate treatment and miR-92a-mimic transfection, apoptosis was analyzed by TUNEL staining and caspase-3 immunoblotting.
RESULTS: Microarray, confirmed by qPCR, revealed a seven-fold increase in miR-92a levels in sporadic human colon cancer tissue compared to adjacent normal colon. Treating human colon cancer cells with butyrate reduced the levels of pri-miR17-92a, precursor and mature miR-92a, as well as c-Myc. SAHA and valproic acid had similar effects. Mutation of the c-Myc binding site diminished butyrate's inhibitory effects on C13orf25 promoter activity. Silencing c-Myc expression reduced miR-92a levels. c-Myc over-expression neutralized butyrate-induced attenuation of pri-miR17-92a. Exogenous miR-92a inhibited butyrate-induced p57 expression and reversed the beneficial actions of butyrate on colon cancer cell proliferation and apoptosis.
CONCLUSIONS: Our findings identify a novel cellular mechanism whereby butyrate inhibits miR-92a transcription by reducing c-Myc, thus augmenting p57 levels. These actions diminish colon cancer cell proliferation and stimulate apoptosis. This newly described regulation of oncogenic miRNA biogenesis expands our understanding of colon cancer cell biology and identifies novel therapeutic targets.

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