Sequence variation among members of the miR-200 microRNA family is correlated with variation in the ability to induce hallmarks of mesenchymal-epithelial transition in ovarian cancer cells

Ascites in ovarian cancer: MicroRNA deregulations and their potential roles in ovarian carcinogenesis

Ovarian cancer comprises the most lethal gynecologic malignancy and is accompanied by the high potential for the incidence of metastasis, recurrence and chemotherapy resistance, often associated with a formation of ascitic fluid. The differentially expressed ascites-derived microRNAs may be linked to ovarian carcinogenesis. The article focuses on a number of miRNAs that share a common expression pattern as determined by independent studies using ascites samples and with regard to their functions and outcomes in experimental and clinical investigations.Let-7b and miR-143 have featured as tumor suppressors in ovarian cancer, which is in line with data on other types of cancer. Although two miRNAs, i.e. miR-26a-5p and miR-145-5p, act principally as tumor suppressor miRNAs, they occasionally exhibit oncogenic roles. The performance of miR-95-3p, upregulated in ascites, is open to debate given the current lack of supportive data on ovarian cancer; however, data on other cancers indicates its probable oncogenic role. Different findings have been reported for miR-182-5p and miR-200c-3p; in addition to their presumed oncogenic roles, contrasting findings have indicated their ambivalent functions. Further research is required for the identification and evaluation of the potential of specific miRNAs in the diagnosis, prediction, treatment and outcomes of ovarian cancer patients.

Double Insurance for OC: miRNA-Mediated Platinum Resistance and Immune Escape

Ovarian cancer (OC) is still the leading cause of death among all gynecological malignancies, despite the recent progress in cancer therapy. Immune escape and drug resistance, especially platinum-based chemotherapy, are significant factors causing disease progression, recurrence and poor prognosis in OC patients. MicroRNAs(miRNAs) are small noncoding RNAs, regulating gene expression at the transcriptional level. Accumulating evidence have indicated their crucial roles in platinum resistance. Importantly, they also act as mediators of tumor immune escape/evasion. In this review, we summarize the recent study of miRNAs involved in platinum resistance of OC and systematically analyses miRNAs involved in the regulation of OC immune escape. Further understanding of miRNAs roles and their possible mechanisms in platinum resistance and tumor escape may open new avenues for improving OC therapy.

The ability of miRNAs to induce mesenchymal-to-epithelial transition (MET) in cancer cells is highly dependent upon genetic background

Understanding of the molecular basis of host cell-miRNA interactions is prerequisite to the successful application of miRNAs as potential therapeutic agents. We studied the morphological and molecular consequences of over expression of three sequence divergent miRNAs previously implicated in the mesenchymal-to-epithelial transition process (MET) in three distinct mesenchymal-like cancer cell lines. The ability of miRNAs to induce morphological changes characteristic of MET positively correlated with induced changes in the expression of genes previously implicated in the process. Variability in the responses of different mesenchymal-like cells to over expression of the same miRNAs was attributable to inherent differences in trans-regulatory profiles pre-disposing these cells to miRNA-induced MET. Collectively our results indicate that miRNA-mediated regulation of MET is a highly integrated process that is significantly modulated by the molecular background of individual cells.

Stromal-induced downregulation of miR-1247 promotes prostate cancer malignancy

Cancer progression is strictly dependent on the relationship between tumor cells and the surrounding stroma, which supports cancer malignancy promoting several crucial steps of tumor progression, including the execution of the epithelial to mesenchymal transition (EMT) associated with enhancement in cell invasion, resistance to both anoikis and chemotherapeutic treatments. Recently it has been highlighted the central role of microRNAs (miRNAs) as regulators of tumor progression. Notably, in several tumors a strong deregulation of miRNAs is observed, supporting proliferation, invasion, and metabolic reprogramming of tumor cells. Here we demonstrated that cancer-associated fibroblasts induce a downregulation of miR-1247 in prostate cancer (PCa) cells. We proved that miR-1247 repression is functional for the achievement of EMT and increased cell invasion as well as stemness traits. These phenomena contribute to promote the metastatic potential of PCa cells as demonstrated by increased lung colonization in in vivo experiments. Moreover, as a consequence of miR-1247 downregulation, we observed a correlated increased expression level of neuropilin-1, a miR-1247 target involved as a coreceptor in the epidermal growth factor receptor signaling. Taken together, our data highlight miR-1247 as a potential target for molecular therapies aimed to block the progression and diffusion of PCa.

miRNA-199a-5p suppresses proliferation and invasion by directly targeting NF-κB1 in human ovarian cancer cells

The aberrant expression of microRNA (miRNA)-199a-5p has been frequently reported in a number of cancer types, but to the best of our knowledge, this has not been reported in ovarian cancer (OC). The role and the molecular mechanism of miR-199a-5p in OC have not been reported. Therefore, the present study investigated the effects of miR-199a-5p overexpression on the proliferation and invasion of OC cells. The level of miR-199a-5p in OC cell lines was determined by reverse transcription-quantitative polymerase chain reaction. The miR-199a-5p mimic was transiently transfected into OC cells using Lipofectamine^™ 2000 reagent. Subsequently, the BrdU-ELISA results indicated that the exogenous expression of miR-199a-5p inhibited cell proliferation. In addition, miR-199a-5p overexpression was able to inhibit the invasion of HO-8910 and ES-2 cells. RT-qPCR was performed to determine the expression of matrix metalloproteinase (MMP)-2 and -9 in OC cells. NF-κB1 expression was reduced by upregulation of miR-199a-5p. Bioinformatics analysis predicted that NF-κB1 was a potential target of miR-199a-5p. Luciferase reporter assay further confirmed that miR-199a-5p was able to directly target the 3'UTR of NF-κB1. In conclusion, miRNA-199a-5p may suppress the proliferation and invasion of human ovarian cancer cells by directly targeting NF-κB1.

Ascites-Derived Extracellular microRNAs as Potential Biomarkers for Ovarian Cancer

Ovarian cancer as the most fatal gynecological malignancy is often manifested by excessive fluid accumulation known as ascites or effusion. Ascites-derived microRNAs (miRNAs) may be closely associated with ovarian cancer progression. However, our knowledge of their roles, altered expression, and clinical outcomes remained limited. In this study, large-scale expression profiling of 754 human miRNAs was performed using real-time quantitative polymerase chain reaction and 384-well TaqMan array human miRNA A and B cards to identify differentially expressed miRNAs between extracellular fraction of the ascitic fluid associated with high-grade serous ovarian carcinomas and control plasma. Of the 754 miRNAs, 153 were significantly differentially expressed relative to the controls. Expression of 7 individual miRNAs (miR-200a, miR-200b, miR-200c, miR-141, miR-429, miR-1290, and miR-30a-5p) was further validated in extended sample sets, including serous, endometrioid, and mucinous subtypes. All miR-200 family members and miR-1290 were conspicuously overexpressed, while miR-30a-5p was only weakly overexpressed. The ability of miRNAs expression to discriminate the pathological samples from the controls was strong. Receiver operating characteristic curve analyses found area under the curve (AUC) values of 1.000 for miR-200a, miR-200c, miR-141, miR-429, and miR-1290 and of AUC 0.996 and 0.885 for miR-200b and miR-30a-5p, respectively. Preliminary survival analyses indicated low expression level of miR-200b as significantly related to longer overall survival (hazard ratio [HR]: 0.25, mean survival 44 months), while high expression level was related to poor overall survival (HR: 4.04, mean survival 24 months). Our findings suggested that ascites-derived miRNAs should be further explored and evaluated as potential diagnostic and prognostic biomarkers for ovarian cancer.

Time-course analysis of microRNA-induced mesenchymal-to-epithelial transition underscores the complexity of the underlying molecular processes

Expression levels of the miR-200 family of miRNAs are significantly reduced during the epithelial-to-mesenchymal transition (EMT) and consequent metastasis of ovarian and other cancers. Consistently, ectopic over-expression of miR-200 family miRNAs in mesenchymal-like cells reverses the process by converting treated cells to an epithelial phenotype, thereby reducing invasiveness and increasing sensitivity to chemotherapeutic drugs. To better understand the dynamics and molecular processes underlying miRNA-induced mesenchymal-to mesenchymal transition (MET), a time-course study was conducted where miRNA-induced morphological and molecular changes associated with MET were monitored over a period of 144 h. Morphological transition from an elongated mesenchymal-like to a cuboidal epithelial-like phenotype is maximized at 48 h with cells returning to the elongated phenotype by 144 h. Changes in the expression of >3000 genes, including many previously associated with epithelial-to-mesenchymal transition (EMT), are most pronounced at 48 h, and approach starting levels of expression by 144 h. The majority of these genes are not direct targets of miR-429. Targeted (siRNA) inhibition of key miR-429 regulated genes previously implicated as drivers of EMT/MET, do not recapitulate miR-429 induced MET indicating that the underlying molecular processes are complex.

MiR-200 Regulates Epithelial-Mesenchymal Transition in Anaplastic Thyroid Cancer via EGF/EGFR Signaling

This study was set to study the molecular mechanism underlying how miR-200 regulates EGF/EGFR signaling to involve in epithelial-mesenchymal transition (EMT) in anaplastic thyroid cancer (ATC) cells. Loss-of-function experiments of EGFR silencing by siRNA transfection was performed. Transfection of pre-miR-200s or anti-miR-200s was used to increase or decrease miR-200 transcripts. Real-time PCR, Western blot, immunohistochemistry, and transwell experiments were performed to determine the role of miR-200s in EMT and its role in EGF/EGFR-mediated EMT in vitro and in vivo. EGF/EGFR signaling activation increased the expression of mesenchymal marker vimentin in Nthy-ori 3-1 cells and decreased the expression of endothelial maker E-cadherin. EGF stimulation led to increased RhoA expression in Nthy-ori 3-1 cells. EGFR silencing resulted in decreased RhoA expression in SW1736 and ARO cells. EGF stimulation led to down-regulation of miR-200s and EMT. Restoration of miR-200 expression by pre-miR-200a/c transfection reversed the process, including increased E-cadherin and decreased vimentin. Down-regulation of miR-200 by anti-miR-200 effectively reduced miR-200. Matrigel invasion assay proved that restoration of miR-200 expression counteracted invasiveness. EGFR silencing decreased invasiveness in SW1736 cells, while down-regulation of miR-200s restored invasiveness. Xenograft tumors of SW1736 cells with cotransfection of anti-miR-200s and EGFR siRNA which kept the similar E-cadherin and vimentin expression with the untransfected controls. In ATC cells, miR-200s play a central role in EGF/EGFR-mediated invasiveness in vitro and EMT in vivo.

miRNAs and ovarian cancer: a miRiad of mechanisms to induce cisplatin drug resistance

Ovarian cancer is the most aggressive gynecological cancer. One reason for the low 5-year survival rate of under 40% is that ovarian tumors usually acquire resistance to the platinum-based compounds used to treat them. Resistance to one such compound, cisplatin, can arise via numerous mechanisms that can be categorized as pre-, post-, on- or off-target. Pre-target mechanisms prevent accumulation of cisplatin in the cell, on-target mechanisms allow DNA damage to be repaired more efficiently, post-target mechanisms prevent the damage from inducing apoptosis and off-target mechanisms increase resistance via unrelated compensatory mechanisms. miRNAs are short non-coding RNAs that influence cellular function by repressing gene expression. Here we describe how miRNAs can induce cisplatin resistance in ovarian cancer cells via pre-, post-, on- and off-target mechanisms. A better understanding of how miRNAs feed into the mechanisms of drug resistance will inform the rational design of combination therapies for ovarian cancer.

MiR-373 targeting of the Rab22a oncogene suppresses tumor invasion and metastasis in ovarian cancer

Metastasis is major cause of mortality in patients with ovarian cancer. MiR-373 has been shown to play pivotal roles in tumorigenesis and metastasis; however, a role for miR-373 in ovarian cancer has not been investigated. In this study, we show that the miR-373 expression is down-regulated in human epithelial ovarian cancer (EOC) and inversely correlated with clinical stage and histological grade. Ectopic overexpression of miR-373 in human EOC cells suppressed cell invasion in vitro and metastasis in vivo, and the epithelial–mesenchymal transition process. Silencing the expression of miR-373 resulted in an increased migration and invasion of EOC cells. Using integrated bioinformatics analysis, gene expression arrays, and luciferase assay, we identified Rab22a as a direct and functional target of miR-373 in EOC cells. Expression levels of miR-373 were inversely correlated with Rab22a protein levels in human EOC tissues. Rab22a knockdown inhibited invasion and migration of EOC cells, increased E-cadherin expression, and suppressed the expression of N-cadherin. Moreover, overexpression of Rab22a abrogated miR-373-induced invasion and migration of EOC cells. Taken together, these results demonstrate that miR-373 suppresses EOC invasion and metastasis by directly targeting Rab22a gene, a new potential therapeutic target in EOC.

The miR-200 Family: Versatile Players in Epithelial Ovarian Cancer

The role of microRNAs (miRNAs or miRs) in the pathology of epithelial ovarian cancer (EOC) has been extensively studied. Many miRNAs differentially expressed in EOC as compared to normal controls have been identified, prompting further inquiry into their role in the disease. miRNAs belonging to the miR-200 family have repeatedly surfaced over multiple profiling studies. In this review, we attempt to consolidate the data from different studies and highlight mechanisms by which these miRNAs influence progression of metastasis and chemo-resistance in EOC.

Functional and evolutionary significance of human microRNA seed region mutations

MicroRNAs have emerged in recent years as important regulators of cell function in both normal and diseased cells. MiRNAs coordinately regulate large suites of target genes by mRNA degradation and/or translational inhibition. The mRNA target specificities of miRNAs in animals are primarily encoded within a 7 nt “seed region” mapping to positions 2–8 at the molecule's 5′ end. We here combine computational analyses with experimental studies to explore the functional significance of sequence variation within the seed region of human miRNAs. The results indicate that a substitution of even a single nucleotide within the seed region changes the spectrum of mRNA targets by >50%. The high functional cost of even single nucleotide changes within seed regions is consistent with their high sequence conservation among miRNA families both within and between species and suggests processes that may underlie the evolution of miRNA regulatory control.

Epithelial-mesenchymal transition-associated miRNAs in ovarian carcinoma, with highlight on the miR-200 family: prognostic value and prospective role in ovarian cancer therapeutics

MicroRNAs (miRNAs) are a family of short ribonucleic acids found to play a pivotal role in cancer pathogenesis. MiRNAs are crucial in cellular differentiation, growth, stress response, cell death and other fundamental cellular processes, and their involvement in ovarian cancer has been recently shown. They can repress the expression of important cancer-related genes and they can also function both as oncogenes and tumour suppressor genes. During epithelial-mesenchymal transition (EMT), epithelial cells lose their cell polarity and cell-cell adhesion and gain migratory and invasive properties. In the ovarian surface epithelium, EMT is considered the key regulator of the post-ovulatory repair process and it can be triggered by a range of environmental stimuli. The aberrant expression of the miR-200 family (miR-200a, miR-200b, miR-200c, miR-141 and miR-429) in ovarian carcinoma and its involvement in ovarian cancer initiation and progression has been well-demonstrated. The miR-200 family members seem to be strongly associated with a pathologic EMT and to have a metastasis suppressive role. MiRNA signatures can accurately distinguish ovarian cancer from the normal ovary and can be used as diagnostic tools to predict the clinical response to chemotherapy. Recent evidence suggests a growing list of new miRNAs (miR-187, miR-34a, miR-506, miRNA-138, miR-30c, miR-30d, miR-30e-3p, miR-370 and miR-106a, among others) that are also implicated in ovarian carcinoma-associated EMT, either enhancing or suppressing it. MiRNA-based gene therapy provides a prospective anti-tumour approach for integrated cancer therapy. The aim of nanotechnology-based delivery approach for miRNA therapy is to overcome challenges in miRNA delivery and to effectively encourage the reprogramming of miRNA networks in cancer cells, which may lead to a clinically translatable miRNA-based therapy to benefit ovarian cancer patients.

Regulation of Metastasis by microRNAs in Ovarian Cancer

Ovarian cancer (OC) is the second most common and the most fatal gynecologic cancer in the United States. Over the last decade, various targeted therapeutics have been introduced but there has been no corresponding improvement in patient survival mainly because of the lack of effective early detection methods. microRNAs (miRs) are small, non-coding RNAs that regulate gene expression post-transcriptionally. Accumulating data suggest central regulatory roles of miRs in modulating OC initiation, progression, and metastasis. More recently, aberrant miR expression has been also associated with cancer stem cell (CSC) phenotypes and development of CSC chemo-resistance. Here, we review recent advances on miRs and OC metastasis and discuss the concept that miRs are involved in both CSC transformation and subsequent OC metastasis. Finally, we describe the prevalence of circulating miRs and assess their potential utilities as biomarkers for OC diagnosis, prognosis, and therapeutics.