DNMT1-dependent suppression of microRNA424 regulates tumor progression in human bladder cancer

The aim of this study was to examine the role of miRNAs regulation by DNMT1 and its underlying mechanisms in bladder cancer. The choice of target miRNAs was based on the analysis of a TaqMan MicroRNA Panel assay. The role of target miRNA in tumor behavior and the related signaling pathways were assessed using the human bladder cancer cell lines. We also evaluated the predictive power of the target miRNA and its link to DNMT1 from 124 clinical bladder cancer specimens. Our results revealed that the miR-424 level is significantly increased when blocking DNMT1 in bladder cancer cells. From the clinical specimen analysis, the staining of miR-424 was inversely correlated with DNMT1 immunoreactivity. The lack of miR-424 expression was significantly linked to aggressive tumor growth, advanced clinical stage and poor prognosis in bladder cancer. Increased miR-424 suppressed the tumor growth rate and invasion ability determined in vitro and in vivo. Furthermore, the EGFR pathway plays a role in the transmission of the miR-424 signal that regulates cell growth and the epithelial-to-mesenchymal transition. These results highlight a potential role for miR-424 as a molecular predictor and therapeutic target in bladder cancer.     

MicroRNA-34b functions as a potential tumor suppressor in endometrial serous adenocarcinoma

Endometrial serous adenocarcinoma (ESC) is aggressive and carries a poor prognosis. p53 is frequently mutated in ESC. microRNAs (miRNAs) are a direct p53 target and have been implicated in cancer cell behavior. In this study, we compared miRNA expression levels in ESC with the levels in endometrial endometrioid adenocarcinoma (EEC) and normal endometria. Six miRNAs were identified as having aberrant down-regulation specific to ESC with miR-34b being most pronounced. miR-34b was found to have promoter hypermethylation, which when reversed, restored miR-34b expression in the cell lines treated with 5-aza-2' deoxycytidine (DAC). Ectopic expression of miR-34b in turn inhibited cell growth, migration and most notably invasion. Our findings suggest a relationship among p53 mutation, miR-34b promoter methylation and tumor cell behavior. These effects are likely mediated by the downstream target of miR-34b, the proto-oncogene mesenchymal-epithelial transition factor (MET), a known prognostic factor in endometrial carcinomas. The expression of MET was reduced following the restoration of miR-34b in cell lines. In summary, our data suggest that miR-34b plays a role in the molecular pathogenesis of endometrial cancer.     

Dual regulation by microRNA-200b-3p and microRNA-200b-5p in the inhibition of epithelial-to-mesenchymal transition in triple-negative breast cancer

Epithelial to mesenchymal transition (EMT) involves loss of an epithelial phenotype and activation of a mesenchymal one. Enhanced expression of genes associated with a mesenchymal transition includes ZEB1/2, TWIST, and FOXC1. miRNAs are known regulators of gene expression and altered miRNA expression is known to enhance EMT in breast cancer. Here we demonstrate that the tumor suppressive miRNA family, miR-200, is not expressed in triple negative breast cancer (TNBC) cell lines and that miR-200b-3p over-expression represses EMT, which is evident through decreased migration and increased CDH1 expression. Despite the loss of migratory capacity following re-expression of miR-200b-3p, no subsequent loss of the conventional miR-200 family targets and EMT markers ZEB1/2 was observed. Next generation RNA-sequencing analysis showed that enhanced expression of pri-miR-200b lead to ectopic expression of both miR-200b-3p and miR-200b-5p with multiple isomiRs expressed for each of these miRNAs. Furthermore, miR-200b-5p was expressed in the receptor positive, epithelial breast cancer cell lines but not in the TNBC (mesenchymal) cell lines. In addition, a compensatory mechanism for miR-200b-3p/200b-5p targeting, where both miRNAs target the RHOGDI pathway leading to non-canonical repression of EMT, was demonstrated. Collectively, these data are the first to demonstrate dual targeting by miR-200b-3p and miR-200b-5p and a previously undescribed role for microRNA processing and strand expression in EMT and TNBC, the most aggressive breast cancer subtype.     

miR-524-5p suppresses the growth of oncogenic BRAF melanoma by targeting BRAF and ERK2

It has been well documented that miRNAs can modulate the effectiveness of cancer-associated signaling pathways. Mitogen-activated protein kinase (MAPK/ERK) signaling plays an essential role in the progression of many cancers, including melanoma and colon cancers. However, no single miRNA is reported to directly target multiple components of the MAPK/ERK pathway. We performed a miRNA PCR array screening with various MAPK/ERK signaling activities. The miRNA array data revealed that the expression of miR-524-5p was decreased in cells with an active MAPK/ERK pathway and confirmed that the expression of miR-524-5p is inversely associated with the activity of the MAPK/ERK pathway. We demonstrated that miR-524-5p directly binds to the 3′-untranslated regions of both BRAFandERK2 and suppresses the expression of these proteins. Because BRAF and ERK2 are the main components of MAPK signaling, the overexpression of miR-524-5p effectively inhibits MAPK/ERK signaling, tumor proliferation, and melanoma cell migration. Moreover, tumors overexpressing miR-524-5p were significantly smaller than those of the negative control mice. Our findings provide new insight into the role of miR-524-5p as an important miRNA that negatively regulates the MAPK/ERK signaling pathway, suggesting that miR-524-5p could be a potent therapeutic candidate for melanoma treatment.     

A small piece in the cancer puzzle: microRNAs as tumor suppressors and oncogenes

The known classes of genes that function as tumor suppressors and oncogenes have recently been expanded to include the microRNA (miRNA) family of regulatory molecules. miRNAs negatively regulate the stability and translation of target messenger RNAs (mRNA) and have been implicated in diverse processes such as cellular differentiation, cell-cycle control and apoptosis. Examination of tumor-specific miRNA expression profiles has revealed widespread dysregulation of these molecules in diverse cancers. Although studies addressing their role in cancer pathogenesis are at an early stage, it is apparent that loss- or gain-of-function of specific miRNAs contributes to cellular transformation and tumorigenesis. The available evidence clearly demonstrates that these molecules are intertwined with cellular pathways regulated by classical oncogenes and tumor suppressors such as MYC, RAS and p53. Incorporation of miRNA regulation into current models of molecular cancer pathogenesis will be essential to achieve a complete understanding of this group of diseases.     

膀胱癌患者尿液外泌体中miRNA差异表达谱及其生物信息学分析

目的:通过检测及筛选膀胱癌患者及正常人尿液外泌体中差异性表达的miRNA,进行生物学分析,探讨miRNA在膀胱癌发病中的作用。方法:利用超高速离心法及Illumina高通量测序技术分离并检测5例膀胱癌患者及5例配对正常人尿液标本中外泌体miRNA的表达情况,构建其差异表达谱。对差异表达基因进行生物信息学分析,确定差异表达miRNA的主要生物学功能及其可能参与的信号通路。结果:与正常人相比,膀胱癌患者尿液外泌体中共有38个miRNA显著异常表达,其中上调34个,下调4个。通过GO富集及KEGG分析,上述差异表达的miRNA可能通过趋化因子信号通路、PI3K-Akt信号通路、MAPK信号通路及RAS信号通路等参与膀胱癌的发生和发展过程,分别涉及脂质代谢、多糖降解、RNA降解及碱基切除修复等多种生化代谢途径,并参与细胞的粘连、内吞作用、突触囊泡循环等生物学过程。结论:膀胱癌患者尿液外泌体中miRNA的表达谱发生了显著的变化,has-miR-486-5p、hsa-miR-199b-5p、hsa-miR-7704和has-miR-184等miRNA可能通过趋化因子信号通路、PI3K-Akt信号通路、MAPK信号通路及RAS信号通路等在膀胱癌的发生发展过程中发挥重要作用。     

PTEN: a new guardian of the genome

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor is a phosphatase that antagonizes the phosphoinositol-3-kinase/AKT signaling pathway and suppresses cell survival as well as cell proliferation. PTEN is the second most frequently mutated gene in human cancer after p53. Germline mutations of PTEN have been found in cancer susceptibility syndromes, such as Cowden syndrome, in which over 80% of patients have mutations of PTEN. Homozygous deletion of Pten causes embryonic lethality, suggesting that PTEN is essential for embryonic development. Mice heterozygous for Pten develop spontaneous tumors in a variety of organs comparable with the spectrum of its mutations in human cancer. The mechanisms of PTEN functions in tumor suppression are currently under intense investigation. Recent studies demonstrate that PTEN plays an essential role in the maintenance of chromosomal stability and that loss of PTEN leads to massive alterations of chromosomes. The tumor suppressor p53 is known as a guardian of the genome that mediates the cellular response to environmental stress, leading to cell cycle arrest or cell death. Through completely different mechanisms, PTEN also protects the genome from instability. Thus, we propose that PTEN is a new guardian of the genome. In this review, we will discuss new discoveries on the role of PTEN in tumor suppression and explore mechanisms by which PTEN maintains genomic stability.     

微小RNA与卵巢癌铂类耐药的研究进展

微小RNA(micmRNA,miBNA)是广泛存在于生物体内的一类非编码的小RNA,miRNA是细胞增殖、死亡、应激抗性和脂肪代谢的关键调节因素,体外实验已经证实miRNA在卵巢癌耐药中起重要作用.卵巢癌铂类耐药的产生与发展是十分复杂的过程,研究结果显示,miRNA的表达对卵巢癌细胞株的铂类药物敏感性有着重要作用,能够...     

The guardian's little helper: microRNAs in the p53 tumor suppressor network

Several microRNAs (miRNAs) have been implicated in tumor development based on both changes in their expression patterns and gene structural alterations in human tumors. However, we are only now beginning to see how miRNAs interact with classic oncogene and tumor suppressor mechanisms. Several recent studies have implicated the miR-34 family of miRNAs in the p53 tumor suppressor network. The expression of miR-34a, miR-34b, and miR-34c is robustly induced by DNA damage and oncogenic stress in a p53-dependent manner. When overexpressed, miR-34 leads to apoptosis or cellular senescence, whereas reduction of miR-34 function attenuates p53-mediated cell death. These findings, together with the fact that miR-34 is down-regulated in several types of human cancer, show that miRNAs can affect tumorigenesis by working within the confines of well-known tumor suppressor pathways.     

HITS-CLIP reveals key regulators of nuclear receptor signaling in breast cancer

miRNAs regulate the expression of genes in both normal physiology and disease. While miRNAs have been demonstrated to play a pivotal role in aspects of cancer biology, these reports have generally focused on the regulation of single genes. Such single-gene approaches have significant limitations, relying on miRNA expression levels and heuristic predictions of mRNA-binding sites. This results in only circumstantial evidence of miRNA–target interaction and typically leads to large numbers of false positive predictions. Here, we used a genome-wide approach (high-throughput sequencing of RNA isolated by crosslinking immunoprecipitation, HITS-CLIP) to define direct miRNA–mRNA interactions in three breast cancer subtypes (estrogen receptor positive, Her2 amplified, and triple negative). Focusing on steroid receptor signaling, we identified two novel regulators of the ER pathway (miR-9-5p and miR-193a/b-3p), which together target multiple genes involved in ER signaling. Moreover, this approach enabled the definition of miR-9-5p as a global regulator of steroid receptor signaling in breast cancer. We show that miRNA targets and networks defined by HITS-CLIP under physiologic conditions are predictive of patient outcomes and provide global insight into miRNA regulation in breast cancer.     

Circulating mir-320a promotes immunosuppressive macrophages M2 phenotype associated with lung cancer risk

miRNAs play a central role in the complex signaling network of cancer cells with the tumor microenvironment. Little is known on the origin of circulating miRNAs and their relationship with the tumor microenvironment in lung cancer. Here, we focused on the cellular source and relative contribution of different cell types to circulating miRNAs composing our risk classifier of lung cancer using in vitro/in vivo models and clinical samples. A cell-type specific expression pattern and topography of several miRNAs such as mir-145 in fibroblasts, mir-126 in endothelial cells, mir-133a in skeletal muscle cells was observed in normal and lung cancer tissues. Granulocytes and platelets are the major contributors of miRNAs release in blood. miRNAs modulation observed in plasma of lung cancer subjects was consistent with de-regulation of the same miRNAs observed during immunosuppressive conversion of immune cells. In particular, activated neutrophils showed a miRNA profile mirroring that observed in plasma of lung cancer subjects. Interestingly mir-320a secreted by neutrophils of high-risk heavy-smokers promoted an M2-like protumorigenic phenotype through downregulation of STAT4 when shuttled into macrophages. These findings suggest a multifactorial and nonepithelial cell-autonomous origin of circulating miRNAs associated with risk of lung cancer and that circulating miRNAs may act in paracrine signaling with causative role in lung carcinogenesis and immunosuppression.     

微小RNA与肿瘤耐药

 【摘要】　微小RNA （miRNA）是近年来在真核生物中发现的、在转录后水平负调控基因表达的一类长约22个核苷酸的非编码小分子RNA。miRNA生物学效应广泛,与细胞生长、凋亡、新陈代谢和信号转导等密切相关。已报道miRNA在各种肿瘤中表达失常,可能发挥着癌基因和抑癌基因的双重作用,同时越来越多的研究表明miRNA在调节肿瘤细胞对抗肿瘤药物耐药方面发挥着重要作用。系统深入地研究miRNA在肿瘤耐药中的机制,将为发展基于miRNA逆转肿瘤耐药的治疗策略提供重要的依据。     

微小RNA与肿瘤耐药

微小RNA(miRNA)是近年来在真核生物中发现的、在转录后水平负调控基因表达的一类长约22个核苷酸的非编码小分子RNA.miRNA生物学效应广泛,与细胞生长、凋亡、新陈代谢和信号转导等密切相关.已报道miRNA在各种肿瘤中表达失常,可能发挥着癌基因和抑癌基因的双重作用,同时越来越多的研究表明miRNA在调节肿瘤细胞对抗肿瘤药物耐药方面发挥着重要作用.系统深入地研究miRNA在肿瘤耐药中的机制,将为发展基于miRNA逆转肿瘤耐药的治疗策略提供重要的依据.     

微小RNA与肿瘤耐药

微小RNA(miRNA)是近年来在真核生物中发现的、在转录后水平负调控基因表达的一类长约22个核苷酸的非编码小分子RNA.miRNA生物学效应广泛,与细胞生长、凋亡、新陈代谢和信号转导等密切相关.已报道miRNA在各种肿瘤中表达失常,可能发挥着癌基因和抑癌基因的双重作用,同时越来越多的研究表明miRNA在调节肿瘤细胞对抗肿瘤药物耐药方面发挥着重要作用.系统深入地研究miRNA在肿瘤耐药中的机制,将为发展基于miRNA逆转肿瘤耐药的治疗策略提供重要的依据.     

Emerging role of Notch in stem cells and cancer

The Notch signaling pathway is known to be responsible for maintaining a balance between cell proliferation and death and, as such, plays important roles in the formation of many types of human tumors. Recently, Notch signaling pathway has been shown to control stem cell self-renewal and multi-potency. As many cancers are thought to be developed from a number of cancer stem-like cells, which are also known to be linked with the acquisition of epithelial-mesenchymal transition (EMT); and thus suggesting an expanding role of Notch signaling in human tumor progression.     

Let-7b-5p inhibits colon cancer progression by prohibiting APC ubiquitination degradation and the Wnt pathway by targeting NKD1

Naked cuticle homolog 1 (NKD1), which is expressed at low levels in many tumors, is considered an inhibitor of the Wnt/β-catenin pathway, but it is highly expressed in colon cancer and can promote colon cancer cell proliferation. miRNAs are involved in the occurrence and progression of many tumors. However, miRNAs that can regulate NKD1 and the mechanisms by which NKD1 regulates tumor progression remain ambiguous. This research aims to reveal the potential regulatory network of NKD1 in colon cancer. miRNA data downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were analyzed by bioinformatics to screen for potential miRNAs targeting NKD1. Let-7b-5p was found to inhibit proliferation, migration, and invasion of colon cancer cells targeting NKD1. Further studies suggested that let-7b-5p can modulate Wnt signaling activity, and the nuclear accumulation of β-catenin was significantly restrained by let-7b-5p through targeting NKD1. Moreover, NKD1 could prohibit the expression of the APC protein. Further studies manifested that NKD1 bound to APC and promoted the ubiquitination degradation of APC through restraining the expression of the deubiquitinating enzyme USP15 and blocking the combination between USP15 and APC. Functionally, NKD1 enhanced the proliferation and migration of colon cancer cells by inhibiting APC expression. This research revealed a novel mechanism by which the let-7b-5p-NKD1-APC-β-catenin signaling pathway inhibited colon cancer cell progression.