MicroRNAs and metastasis: little RNAs go a long way

Preparation of bufalin-loaded pluronic polyetherimide nanoparticles, cellular uptake, distribution, and effect on colorectal cancer

A large number of studies have shown that bufalin can have a significant antitumor effect in a variety of tumors. However, because of toxicity, insolubility in water, fast metabolism, short half-life, and other shortcomings, its application is limited in cancer therapy. In this study, we explored the anti-metastatic role of bufalin-loaded pluronic polyetherimide nanoparticles on HCT116 colon cancer-bearing mice. Nanoparticle size, shape, drug loading, encapsulation efficiency, and in vitro drug release were studied. Also, cellular uptake of nanoparticles, in vivo tumor targeting, and tumor metastasis were studied. The nanoparticles had a particle size of about 60 nm and an encapsulation efficiency of 75.71%, by weight. The in vitro release data showed that free bufalin was released faster than bufalin-loaded pluronic polyetherimide nanoparticles, and almost 80% of free bufalin was released after 32 hours. Nanoparticles had an even size distribution, were stable, and had a slow release and a tumor-targeting effect. Bufalin-loaded pluronic polyetherimide nanoparticles can significantly inhibit the growth and metastasis of colorectal cancer.

Microenvironmental Influences on Metastasis Suppressor Expression and Function during a Metastatic Cell's Journey

Metastasis is the process of primary tumor cells breaking away and colonizing distant secondary sites. In order for a tumor cell growing in one microenvironment to travel to, and flourish in, a secondary environment, it must survive a series of events termed the metastatic cascade. Before departing the primary tumor, cells acquire genetic and epigenetic changes that endow them with properties not usually associated with related normal differentiated cells. Those cells also induce a subset of bone marrow-derived stem cells to mobilize and establish pre-metastatic niches [1]. Many tumor cells undergo epithelial-to-mesenchymal transition (EMT), where they transiently acquire morphologic changes, reduced requirements for cell-cell contact and become more invasive [2]. Invasive tumor cells eventually enter the circulatory (hematogenous) or lymphatic systems or travel across body cavities. In transit, tumor cells must resist anoikis, survive sheer forces and evade detection by the immune system. For blood-borne metastases, surviving cells then arrest or adhere to endothelial linings before either proliferating or extravasating. Eventually, tumor cells complete the process by proliferating to form a macroscopic mass [3].Up to 90 % of all cancer related morbidity and mortality can be attributed to metastasis. Surgery manages to ablate most primary tumors, especially when combined with chemotherapy and radiation. But if cells have disseminated, survival rates drop precipitously. While multiple parameters of the primary tumor are predictive of local or distant relapse, biopsies remain an imperfect science. The introduction of molecular and other biomarkers [4, 5] continue to improve the accuracy of prognosis. However, the invasive procedure introduces new complications for the patient. Likewise, the heterogeneity of any tumor population [3, 6, 7] means that sampling error (i.e., since it is impractical to examine the entire tumor) necessitates further improvements.In the case of breast cancer, for example, women diagnosed with stage I diseases (i.e., no evidence of invasion through a basement membrane) still have a ~30 % likelihood of developing distant metastases [8]. Many physicians and patients opt for additional chemotherapy in order to "mop up" cells that have disseminated and have the potential to grow into macroscopic metastases. This means that ~ 70 % of patients receive unnecessary therapy, which has undesirable side effects. Therefore, improving prognostic capability is highly desirable.Recent advances allow profiling of primary tumor DNA sequences and gene expression patterns to define a so-called metastatic signature [9-11], which can be predictive of patient outcome. However, the genetic changes that a tumor cell must undergo to survive the initial events of the metastatic cascade and colonize a second location belie a plasticity that may not be adequately captured in a sampling of heterogeneous tumors. In order to tailor or personalize patient treatments, a more accurate assessment of the genetic profile in the metastases is needed. Biopsy of each individual metastasis is not practical, safe, nor particularly cost-effective. In recent years, there has been a resurrection of the notion to do a 'liquid biopsy,' which essentially involves sampling of circulating tumor cells (CTC) and/or cell free nucleic acids (cfDNA, including microRNA (miRNA)) present in blood and lymph [12-16].The rationale for liquid biopsy is that tumors shed cells and/or genetic fragments into the circulation, theoretically making the blood representative of not only the primary tumor but also distant metastases. Logically, one would predict that the proportion of CTC and/or cfDNA would be proportionate to the likelihood of developing metastases [14]. While a linear relationship does not exist, the information within CTC or cfDNA is beginning to show great promise for enabling a global snapshot of the disease. However, the CTC and cfDNA are present at extremely low levels. Nonetheless, newer technologies capture enough material to enrich and sequence the patient's DNA or quantification of some biomarkers.Among the biomarkers showing great promise are metastasis suppressors which, by definition, block a tumor cell's ability to complete the metastatic process without prohibiting primary tumor growth [17]. Since the discovery of the first metastasis suppressor, Nm23, more than 30 have been functionally characterized. They function at various stages of the metastatic cascade, but their mechanisms of action, for the most part, remain ill-defined. Deciphering the molecular interactions of functional metastasis suppressors may provide insights for targeted therapies when these regulators cease to function and result in metastatic disease.In this brief review, we summarize what is known about the various metastasis suppressors and their functions at individual steps of the metastatic cascade (Table 1). Some of the subdivisions are rather arbitrary in nature, since many metastasis suppressors affect more than one step in the metastatic cascade. Nonetheless what emerges is a realization that metastasis suppressors are intimately associated with the microenvironments in which cancer cells find themselves [18].

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.

miR-29a modulates neuronal differentiation through targeting REST in mesenchymal stem cells

OBJECTIVE

To investigate the modulation of microRNAs (miRNAs) upon the neuronal differentiation of mesenchymal stem cells (MSCs) through targeting RE-1 Silencing Factor (REST), a mature neuronal gene suppressor in neuronal and un-neuronal cells.

METHODS

Rat bone marrow derived-MSCs were induced into neuron-like cells (MSC-NCs) by DMSO and BHA in vitro. The expression of neuron specific enolase (NSE), microtubule-associated protein tau (Tau), REST and its target genes, including synaptosomal-associated protein 25 (SNAP25) and L1 cell adhesion molecular (L1CAM), were detected in MSCs and MSC-NCs. miRNA array analysis was conducted to screen for the upregulated miRNAs after neuronal differentiation. TargetScan was used to predict the relationship between these miRNAs and REST gene, and dual luciferase reporter assay was applied to validate it. Gain and loss of function experiments were used to study the role of miR-29a upon neuronal differentiation of MSCs. The knockdown of REST was conducted to show that miR-29a affected this process through targeting REST.

RESULTS

MSCs were induced into neuron-like cells which presented neuronal cell shape and expressed NSE and Tau. The expression of REST declined and the expression of SNAP25 and L1CAM increased upon the neuronal differentiation of MSCs. Among 14 upregulated miRNAs, miR-29a was validated to target REST gene. During the neuronal differentiation of MSCs, miR-29a inhibition blocked the downregulation of REST, as well as the upregulation of SNAP25, L1CAM, NSE and Tau. REST knockdown rescued the effect of miR-29a inhibition on the expression of NSE and Tau. Meanwhile, miR-29a knockin significantly decreased the expression of REST and increased the expression of SNAP25 and L1CMA in MSCs, but did not significantly affect the expression of NSE and Tau.

CONCLUSION

miR-29a regulates neurogenic markers through targeting REST in mesenchymal stem cells, which provides advances in neuronal differentiation research and stem cell therapy for neurodegenerative diseases.

MicroRNAs in pancreatic malignancy: progress and promises

Despite progress in recent years, pancreatic cancer still remains a major clinical challenge. Its incidence and mortality rates have been on consistent rise underscoring the critical need for novel diagnostic, prognostic and therapeutic tools for its effective management. Recent studies have demonstrated that microRNAs (miRNAs/miRs) are deregulated in a variety of malignancies, including pancreatic cancer, and play a significant role in the initiation, progression and metastasis. Furthermore, their vital involvement in the therapeutic resistance of cancer has also been established. Hence, there has been enormous interest worldwide in investigating the roles of miRNAs in pancreatic cancer pathogenesis and exploiting their utility for clinical benefit. In this review, we summarize current knowledge on the role of miRNAs in pancreatic cancer and discuss their potential use as diagnostic and prognostic biomarkers, and as novel targets for development of effective therapeutic strategies.

MicroRNAs: master regulators of drug resistance, stemness, and metastasis

MicroRNAs (miRNAs) are 20-22 nucleotides long small non-coding RNAs that regulate gene expression post-transcriptionally. Last decade has witnessed emerging evidences of active roles of miRNAs in tumor development, progression, metastasis, and drug resistance. Many factors contribute to their dysregulation in cancer, such as chromosomal aberrations, differential methylation of their own or host genes' promoters and alterations in miRNA biogenesis pathways. miRNAs have been shown to act as tumor suppressors or oncogenes depending on the targets they regulate and the tissue where they are expressed. Because miRNAs can regulate dozens of genes simultaneously and they can function as tumor suppressors or oncogenes, they have been proposed as promising targets for cancer therapy. In this review, we focus on the role of miRNAs in driving drug resistance and metastasis which are associated with stem cell properties of cancer cells. Furthermore, we discuss systems biology approaches to combine experimental and computational methods to study effects of miRNAs on gene or protein networks regulating these processes. Finally, we describe methods to target oncogenic or replace tumor suppressor miRNAs and current delivery strategies to sensitize refractory cells and to prevent metastasis. A holistic understanding of miRNAs' functions in drug resistance and metastasis, which are major causes of cancer-related deaths, and the development of novel strategies to target them efficiently will pave the way towards better translation of miRNAs into clinics and management of cancer therapy.

TGF-β upregulates miR-182 expression to promote gallbladder cancer metastasis by targeting CADM1

Transforming growth factor β (TGF-β) plays important roles in tumor metastasis by regulating miRNAs expression. miR-182 is an important molecule in the regulation of cancer progression. The aim of the study is to assess the role of miR-182 in TGF-β-induced cancer metastasis. In the present study, we found that miR-182 levels are significantly upregulated in GBC tissues compared with normal controls, and miR-182 expression is remarkably increased in primary tumors that subsequently metastasized, when compared to those primary tumors that did not metastasize. TGF-β induces miR-182 expression in GBC cells, and overexpression of miR-182 promotes GBC cell migration and invasion, whereas miR-182 inhibition suppresses TGF-β-induced cancer cell migration and invasion. The blockage of miR-182 by a specific inhibitor effectively inhibits pulmonary metastases in vivo. We further identified that the cell adhesion molecule1 (CADM1) is a new target gene of miR-182. miR-182 negatively regulates CADM1 expression in vitro and in vivo. Importantly, re-expression of CADM1 in GBC cells partially abrogates miR-182-induced cell invasion.

CONCLUSIONS

miR-182 is an important mediator of GBC metastasis, thus offering a new target for the development of therapeutic agents against GBC.

MicroRNA-135b promotes lung cancer metastasis by regulating multiple targets in the Hippo pathway and LZTS1

Dysregulation of microRNAs has a critical role in cancer progression. Here we identify an intronic microRNA, miR-135b that is upregulated in highly invasive non-small-cell lung cancer cells. Expression of miR-135b enhances cancer cell invasive and migratory abilities in vitro and promotes cancer metastasis in vivo, while specific inhibition of miR-135b by a miR-135b-specific molecular sponge and antagomirs suppresses cancer cell invasion, orthotopic lung tumour growth and metastasis in a mouse model. miR-135b targets multiple key components in the Hippo pathway, including LATS2, β-TrCP and NDR2, as well as LZTS1. Expression of miR-135b, LZTS1, LATS2 and nuclear TAZ predicts poor outcomes of non-small-cell lung cancer. We find that miR-135b is dually regulated by DNA demethylation and nuclear factor-kappaB signalling, implying that abnormal expression of miR-135b in cancer may result from inflammatory and epigenetic modulations. We conclude that miR-135b is an oncogenic microRNA and a potential therapeutic target for non-small-cell lung cancer.

microRNA-106a modulates cisplatin sensitivity by targeting PDCD4 in human ovarian cancer cells

microRNAs (miRNAs/miRs) are a cluster of short non-protein coding RNAs that negatively regulate gene expression, which is involved in fundamental cellular processes, including the response of tumor cells to chemotherapeutic agents. The present study investigated the role of miR-106a in the development of drug resistance in ovarian cancer cells. The expression of miR-106a in the ovarian cancer OVCAR3 cell line and the cisplatin (CDDP)-resistant ovarian cancer OVCAR3/CIS cell line was detected using stem-loop quantitative (q)PCR. The OVCAR3 and OVCAR3/CIS cells were transfected with mimics or inhibitors of miR-106a or with negative control (NC) RNA using lipofectamine 2000. Luciferase reporter assays were used to determine whether PDCD4 was a direct target of miR-106a in the OVCAR3 cells. The expression levels of the PDCD4 proteins were assessed using qRT-PCR and western blotting, respectively. Drug sensitivity was analyzed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, while apoptosis was determined by fluorescence-activating cell sorting analysis. The expression levels of miR-106a were upregulated in the CDDP-resistant ovarian cancer OVCAR3/CIS cell line compared with the parental OVCAR3 cell line. However, the PDCD4 protein levels were decreased in the OVCAR3/CIS cells compared with the OVCAR3 cells. The luciferase reporter assays revealed that PDCD4 was a direct miR-106a target in the OVCAR3 cells. Transfection of the OVCAR3/CIS cells with inhibitors of miR-106a enhanced the sensitivity of the OVCAR3/CIS cells to CDDP and increased CDDP-induced apoptosis. The expression of the PDCD4 protein and the sensitivity to CDDP was decreased in the OVCAR3 cells that were transfected with the mimics of miR-106a. The knockdown of PDCD4 expression using PDCD4-specific siRNAs in the OVCAR3 cells demonstrated that PDCD4 is a key signaling molecule in OVCAR3 cell CDDP-induced resistance. miR-106a may be involved in the development of drug resistance and the regulation of PDCD4 expression, at least in part, by modulating CDDP-induced apoptosis in ovarian cancer cells.

Post-transcriptional processing of genetic information and its relation to cancer

During the development, progression and dissemination of neoplastic lesions, cancer cells hijack normal pathways and mechanisms, especially those involved in repair and embryologic development. These pathways include those involved in intercellular communication, control of transcription, post-transcriptional regulation of protein production including translation of mRNAs, post-translational protein modifications, e.g., acetylation of proteins, and protein degradation. Small, non-translatable RNAs, especially microRNAs (miRs), are Important components of post-transcriptional control. MiRs are produced from areas of the genome that are not translated into proteins, but may be co-regulated with their associated genes. MiRs bind to the 3' untranslated regions of mRNAs and regulate the expression of genes in most cases by either promoting the degradation of mRNA and/or inhibiting the translation of mRNAs into proteins; thus, miRs usually cause a decrease in protein levels that would be expected if the mRNAs were translated normally. It is early in our understanding of how miRs affect neoplastic processes, but miRs are expressed differentially in most cancers and have been associated with tumor progression, chemoresistance and metastasis. MiRs are present in nanovesicles, such as exosomes, and thus are likely involved in intercellular communication, especially in neoplasia. MiRs are attractive targets for novel therapies of cancer as well as potential biomarkers that might be useful for early detection and diagnosis, and for prediction of therapeutic efficacy. MiRs also could aid and in determining prognosis, evaluating novel therapies, and developing preventive strategies by their use as surrogate end points.

RILES, a novel method for temporal analysis of the in vivo regulation of miRNA expression

Novel methods are required to investigate the complexity of microRNA (miRNA) biology and particularly their dynamic regulation under physiopathological conditions. Herein, a novel plasmid-based RNAi-Inducible Luciferase Expression System (RILES) was engineered to monitor the activity of endogenous RNAi machinery. When RILES is transfected in a target cell, the miRNA of interest suppresses the expression of a transcriptional repressor and consequently switch-ON the expression of the luciferase reporter gene. Hence, miRNA expression in cells is signed by the emission of bioluminescence signals that can be monitored using standard bioluminescence equipment. We validated this approach by monitoring in mice the expression of myomiRs-133, −206 and −1 in skeletal muscles and miRNA-122 in liver. Bioluminescence experiments demonstrated robust qualitative and quantitative data that correlate with the miRNA expression pattern detected by quantitative RT-PCR (qPCR). We further demonstrated that the regulation of miRNA-206 expression during the development of muscular atrophy is individual-dependent, time-regulated and more complex than the information generated by qPCR. As RILES is simple and versatile, we believe that this methodology will contribute to a better understanding of miRNA biology and could serve as a rationale for the development of a novel generation of regulatable gene expression systems with potential therapeutic applications.

Histone demethylase retinoblastoma binding protein 2 is overexpressed in hepatocellular carcinoma and negatively regulated by hsa-miR-212

Background

The H3K4 demethylase retinoblastoma binding protein 2 (RBP2) is involved in the pathogenesis of gastric cancer, but its role and regulation in hepatocellular carcinoma (HCC) is unknown. We determined the function of RBP2 and its regulation in HCC in vitro and in human tissues.

Methods

We analyzed gene expression in 20 specimens each of human HCC and normal liver tissue by quantitative real-time PCR and immunohistochemistry. Proliferation was analyzed by foci formation and senescence by β-galactosidase staining. Promoter activity was detected by luciferase reporter assay.

Results

The expression of RBP2 was stronger in cancerous than non-cancerous tissues, but that of its binding microRNA, Homo sapiens miR-212 (hsa-miR-212), showed an opposite pattern. SiRNA knockdown of RBP2 significantly upregulated cyclin-dependent kinase inhibitors (CDKIs), with suppression of HCC cell proliferation and induction of senescence. Overexpression of hsa-miR-212 suppressed RBP2 expression, with inhibited cell proliferation and induced cellular senescence, which coincided with upregulated CDKIs; with low hsa-miR-212 expression, CDKIs were downregulated in HCC tissue. Inhibition of hsa-miR-212 expression upregulated RBP2 expression. Luciferase reporter assay detected the direct binding of hsa-miR-212 to the RBP2 3′ UTR.

Conclusions

RBP2 is overexpressed in HCC and negatively regulated by hsa-miR-212. The hsa-miR-212–RBP2–CDKI pathway may be important in the pathogenesis of HCC.

MicroRNA-200a regulates Grb2 and suppresses differentiation of mouse embryonic stem cells into endoderm and mesoderm

The mechanisms by which microRNAs (miRNAs) affect cell fate decisions remain poorly understood. Herein, we report that miR-200a can suppress the differentiation of mouse embryonic stem (ES) cells into endoderm and mesoderm. Interestingly, miR-200a directly targets growth factor receptor-bound protein 2 (Grb2), which is a key adaptor in the Erk signaling pathway. Furthermore, high levels of miR-200a dramatically decrease Grb2 levels and suppress the appearance of mesoderm and endoderm lineages in embryoid body formation, as well as suppressing the activation of Erk. Finally, Grb2 supplementation significantly rescues the miR-200a-induced layer-formation bias and the Erk suppression. Collectively, our results demonstrate that miR-200a plays critical roles in ES cell lineage commitment by directly regulating Grb2 expression and Erk signaling.

Decreased miRNA-148a is associated with lymph node metastasis and poor clinical outcomes and functions as a suppressor of tumor metastasis in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide, and only 15% of lung cancer patients live more than 5 years. microRNAs (miRNAs) are endogenously expressed non-coding RNAs, and dysregulation of miRNAs is a common feature in human cancers including lung cancer. In this study, we describe the epigenetic regulation of miRNA-148a and its prognostic value in NSCLC. Due to hypermethylation of the miRNA‑148a encoding region, the expression levels of miRNA-148a were decreased in NSCLC tissues and cells. Decreased miRNA‑148a expression was associated with lymph node metastasis, advanced clinical stage and shortened disease-free survival and overall survival in NSCLC, and was an independent prognostic factor for overall survival in multivariate analysis. In vitro, overexpression of miRNA-148a significantly suppressed the migratory and invasive abilities of A549 and H1299 lung cancer cells. Enforced expression of miRNA-148a in lung cancer cell lines resulted in a significant reduction in the expression of DNMT1. This, in turn, led to a decrease in DNA methylation of the tumor-suppressor gene E-cadherin and induced an increase in the protein levels of E-cadherin. By understanding the function and molecular mechanism of miRNA-148a in NSCLC, miRNA-148a may have therapeutic potential to suppress lung cancer metastasis.

Targeted delivery of miR-200c/DOC to inhibit cancer stem cells and cancer cells by the gelatinases-stimuli nanoparticles

Cancer stem cells (CSCs) are recently discovered as vital obstacles for the successful cancer therapy. Emerging evidences suggest that miR-200c functions as an effective CSCs inhibitor and can restore sensitivity to microtubule-targeting drugs. In the present work, the intelligent gelatinases-stimuli nanoparticles (NPs) was set up to co-deliver miR-200c and docetaxel (DOC) to verify their synergetic effects on inhibition of CSCs and non-CSC cancer cells. After tumor cells were treated with miR-200c NPs, miR-200c and its targeted gene class III beta-tubulin (TUBB3)TUBB3 expression were evaluated. The effects of miR-200c/DOC NPs on tumor cell viability, migration and invasion as well as the expression of E-cadherin and CD44 were studied. The antitumor effects of miR-200c/DOC NPs were compared with DOC NPs in xenograft gastric cancer mice. Moreover, the residual tumors after treatment were subcutaneously seeded into nude mice to further investigate the effective maintenance of NPs. We found that the gelatinases-stimuli NPs facilitated miR-200c into cells, achieving sustained miR-200c expression in tumor cells during 9 days. The miR-200c/DOC NPs significantly enhanced cytotoxicity of DOC, possibly by decreasing TUBB3 level, and reversing EMT. The miR-200c NPs achieved high levels of in vivo accumulation and long retention in gastric cancer xenografts after intravenous administration. The miR-200c/DOC NPs prominently suppressed in vivo tumor growth with elevated miR-200c and E-cadherin levels and down-regulated TUBB3 and CD44 expressions. When the residual tumors after miR-200c/DOC NPs treatment were re-transplanted into nude mice, the tumors demonstrated the slowest growth speed. The miR-200c/DOC NPs may provide a promising modality for co-delivery of nucleic acid and drugs to simultaneously inhibit CSCs and non-CSC cancer cells.

MicroRNA-17/20a functions to inhibit cell migration and can be used a prognostic marker in oral squamous cell carcinoma

OBJECTIVES

Oral squamous cell carcinoma (OSCC) accounts for>90% oral cancer which is a leading cause of cancer death worldwide. Early diagnosis may well offer an opportunity to increase survival to this neoplasm. Micro(mi)RNA-interfered cancer progression is crucial, yet its migration machinery of OSCC is still unknown. To access whether the possible miRNA prognostic markers and underlying mechanisms, we developed a highly migratory TW2.6 MS-10 cells from TW2.6 cells to investigate the issue.

MATERIALS AND METHODS

miRNA profiling was performed on TW2.6 and TW2.6 MS-10. Target miRNA was correlated to pathological status in OSCC patients by real-time RT-PCR. A downstream effector was identified using a bioinformatics analysis, and a 3'-untranslated region (UTR) reporter assay was used.

RESULTS

An miRNA cluster, miR-17-92, including miR-17, miR-19b, miR-20a, and miR-92a, was found to be significantly down-regulated in TW2.6 MS-10 compared to TW2.6 cells. Overexpression of this cluster decreased the migratory ability of OSCC cell lines. We further demonstrated that miR-17 and miR-20a are the main miRNAs of miR-17-92 cluster which modulate OSCC migration. Clinically, miR-17/20a showed negative correlation with TNM stage and lymphatic metastasis. Through a bioinformatics screening analysis and 3'UTR reporter assay, we confirmed the integrin (ITG) β8 as a direct target of miR-17/20a, and knockdown of ITGβ8 reduced cell migratory capability of OSCC.

CONCLUSIONS

miR-17/20a acts as a prognostic predictor of OSCC patients' outcome and a tumor migration suppressor miRNA.

MicroRNA-497 is a potential prognostic marker in human cervical cancer and functions as a tumor suppressor by targeting the insulin-like growth factor 1 receptor

BACKGROUND

Increasing evidence has shown that microRNAs function as oncogenes or tumor suppressors in human malignancies, but the roles of microRNA (miR)-497 in human cervical cancer still remain unclear. Our aim was to analyze the clinicopathologic and prognostic significance of miR-497 in human cervical cancer and to investigate the effects of miR-497 on the malignant phenotype of cervical cancer cells.

METHODS

First, we detected miR-497 expression in the HPV-16-immortalized cervical epithelial cell lines and 4 other cervical cancer cell lines (HeLa, Caski, SiHa, and HeLa-S3). Then the expression of miR-497 was analyzed in cervical cancer tissues and paired nontumor tissues, and its correlation with clinicopathologic features and survival was analyzed. Finally, the roles of miR-497 in regulation of tumor proliferation, apoptosis, migration, invasion, and target gene expression were further investigated.

RESULTS

MiR-497 was downregulated in cervical cancer cells or tissues compared with HPV-16-immortalized cervical epithelial cell lines or the paired nontumor tissues. Also, the decrease in miR-497 correlated closely with the criteria of the International Federation of Gynaecology and Obstetrics stage and lymph node metastases in patients with cervical cancer. Multivariate Cox analysis showed that low miR-497 expression appeared to be an unfavorable prognostic factor. Transient forced expression of miR-497 decreased the growth and colony-formation capacity of HeLa and SiHa cells by inducing Caspase-3-dependent apoptosis. Forced expression of miR-497 suppressed the migration and invasiveness of cervical cancer cells. By computational miRNA target prediction and functional analysis, miR-497 was demonstrated to bind to the 3' untranslated regions of IGF-1R mRNA, and upregulation of miR-497 downregulated IGF-1R protein expression. Further investigation showed that small interfering RNA-mediated IGF-1R knockdown could mimic the effect of enforced miR-497 expression on the malignant phenotypes of cervical cancer cells.

CONCLUSION

MiR-497 may be a potential prognostic marker and functions as a tumor suppressor in human cervical cancer by post-transcriptionally targeting IGF-1R.

Survival of hypoxic human mesenchymal stem cells is enhanced by a positive feedback loop involving miR-210 and hypoxia-inducible factor 1

The use of mesenchymal stem cells (MSCs) has emerged as a potential new treatment for myocardial infarction. However, the poor viability of MSCs after transplantation critically limits the efficacy of this new strategy. The expression of microRNA-210 (miR-210) is induced by hypoxia and is important for cell survival under hypoxic conditions. Hypoxia increases the levels of hypoxia inducible factor-1 (HIF-1) protein and miR-210 in human MSCs (hMSCs). miR-210 positively regulates HIF-1α activity. Furthermore, miR-210 expression is also induced by hypoxia through the regulation of HIF-1α. To investigate the effect of miR-210 on hMSC survival under hypoxic conditions, survival rates along with signaling related to cell survival were evaluated in hMSCs over-expressing miR-210 or ones that lacked HIF-1α expression. Elevated miR-210 expression increased survival rates along with Akt and ERK activity in hMSCs with hypoxia. These data demonstrated that a positive feedback loop involving miR-210 and HIF-1α was important for MSC survival under hypoxic conditions.

A genetic variant in miR-146a modifies colorectal cancer susceptibility in a Chinese population

MicroRNAs (miRNAs) are a family of endogenous, small, noncoding RNA molecules that involved in a wide range of biological processes including differentiation, proliferation, and apoptosis. A polymorphism G>C (rs2910164) is located in the stem region opposite to the mature miR-146a sequence. In our study, we investigated whether rs2910164 is associated with the risk of colorectal cancer (CRC) in a Chinese population. We genotyped the rs2910164 polymorphism using TaqMan method and evaluated the association with CRC risk in a case-control study, including 1,147 CRC patients and 1,203 cancer-free controls. Logistic regression models were used to assess the genetic effects on the development of CRC. Overall, we found that rs2910164 was significantly associated with the reduced CRC risk [GC/CC versus GG: adjusted odds ratio (OR) = 0.78, 95 % confidence intervals (CIs) = 0.66-0.93]. In the stratification analysis, this decreased risk was also pronounced among non-smokers (0.75, 0.61-0.93), non-drinkers (0.77, 0.63-0.94), and no family history of cancer (0.79, 0.65-0.95). Furthermore, GC/CC genotypes were associated with reduced CRC susceptibility in intermediate differentiated CRC (0.75, 0.62-0.90), and similar effect was observed in patients with the advanced stage tumor (Dukes C and D) (0.76, 0.61-0.93). In conclusion, our results suggest that miR-146a rs2910164 may contribute to the susceptibility to CRC in a Chinese population. Further larger population-based prospective and functional studies are needed to validate our findings.

Genomic signatures of a global fitness index in a multi-ethnic cohort of women

The rates of obesity and sedentary lifestyle are on a dramatic incline, with associated detrimental health effects among women in particular. Although exercise prescriptions are useful for overcoming these problems, success can be hampered by differential responsiveness among individuals in cardiovascular fitness indices (i.e. improvements in strength, lipids, VO(2) max). Genomic factors appear to play an important role in determining this inter-individual variation. We performed microarray analyses on mRNA in whole blood from 60 sedentary women from a multi-ethnic cohort who underwent 12 weeks of exercise, to identify gene subsets that were differentially expressed between individuals who experienced the greatest and least improvements in fitness. We identified 43 transcripts in 39 unique genes (FDR<10%; FC>1.5) whose expression increased the most in "high" versus "low" pre-menopausal female responders. These 39 genes were enriched in six biological pathways, including oxidative phosphorylation (p = 8.08 × 10(-3)). Several of the 39 genes (i.e. TIGD7, UQCRH, PSMA6, WDR12, TFB2M, USP15) have previously reported associations with fitness-related phenotypes. In summary, we identified gene signatures based on mRNA analysis that define responsiveness to exercise in a largely minority-based female cohort. Importantly, this study validates several genes/pathways previously associated with exercise responsiveness and extends these findings with additional novel genes.

Oncolytic adenovirus co-expressing miRNA-34a and IL-24 induces superior antitumor activity in experimental tumor model

It has been demonstrated that numerous microRNAs (miRNAs) have potent tumor-suppressing effects on a variety of cancers, implicating a possible application of miRNA in tumor therapy. Oncolytic adenovirus is a suitable vector to deliver tumor suppressor genes for treatment of cancers. However, it remains unknown whether co-expression of tumor suppressor genes and miRNAs can contribute to a more potent antitumor capacity within an oncolytic adenovirus delivery system. In this study, we found that expression of miRNA-34a was reduced in hepatocellular carcinoma (HCC), and the reduced expression of miRNA-34a was associated with worse outcome of HCC patients. Thus, we developed an oncolytic adenoviral vector, AdCN205, to co-express miRNA-34a and IL-24 driven by an adenovirus endogenous E3 promoter in HCC cells. High levels of miRNA-34a and IL-24 expression were detected in AdCN205-IL-24-miR-34a-infected HCC cells. AdCN205-IL-24-miR-34a significantly induced dramatic antitumor activity, as compared with that induced by AdCN205-IL-24 or AdCN205-miR-34a alone. Transfer of miRNA-34a into HCC cells inhibited the expression of its target genes, Bcl-2 and SIRT1. Treatment of established xenograft HCC tumors with AdCN205-IL-24-miR-34a in a mouse model resulted in complete tumor regression without recurrence. Taken together, our data provide a promising and reasonable delivery strategy of double-aimed cancer therapy, in which miRNAs and tumor-suppressing genes are used simultaneously.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

The microRNA -23b/-27b cluster suppresses the metastatic phenotype of castration-resistant prostate cancer cells

MicroRNAs (miRs) are small, endogenous, non-coding RNAs that regulate the stability and/or translation of complementary mRNA targets. MiRs have emerged not only as critical modulators of normal physiologic processes, but their deregulation may significantly impact prostate and other cancers. The expression of miR-23b and miR-27b, which are encoded by the same miR cluster (miR-23b/-27b), are downregulated in metastatic, castration-resistant tumors compared to primary prostate cancer and benign tissue; however, their possible role in prostate cancer progression is unknown. We found that ectopic expression of miR-23b/-27b in two independent castration-resistant prostate cancer cell lines resulted in suppression of invasion and migration, as well as reduced survival in soft agar (a measure of anoikis). However, there was no effect of miR-23b/-27b on cell proliferation suggesting that these miRs function as metastasis (but not growth) suppressors in prostate cancer. Conversely, inhibition of miR-23b/-27b in the less aggressive androgen-dependent LNCaP prostate cancer cell line resulted in enhanced invasion and migration also without affecting proliferation. Mechanistically, we found that introduction of miR-23b/-27b in metastatic, castration-resistant prostate cancer cell lines resulted in a significant attenuation of Rac1 activity without affecting total Rac1 levels and caused increased levels of the tumor suppressor E-cadherin. Inhibition of these miRs had the opposite effect in androgen-dependent LNCaP cells. These results suggest that miR-23b/-27b are metastasis suppressors that might serve as novel biomarkers and therapeutic agents for castration-resistant disease.

TGF-β upregulates miR-181a expression to promote breast cancer metastasis

Late-stage breast cancer metastasis is driven by dysregulated TGF-β signaling, but the underlying molecular mechanisms have not been fully elucidated. We attempted to recapitulate tumor and metastatic microenvironments via the use of biomechanically compliant or rigid 3D organotypic cultures and combined them with global microRNA (miR) profiling analyses to identify miRs that were upregulated in metastatic breast cancer cells by TGF-β. Here we establish miR-181a as a TGF-β-regulated "metastamir" that enhanced the metastatic potential of breast cancers by promoting epithelial-mesenchymal transition, migratory, and invasive phenotypes. Mechanistically, inactivation of miR-181a elevated the expression of the proapoptotic molecule Bim, which sensitized metastatic cells to anoikis. Along these lines, miR-181a expression was essential in driving pulmonary micrometastatic outgrowth and enhancing the lethality of late-stage mammary tumors in mice. Finally, miR-181a expression was dramatically and selectively upregulated in metastatic breast tumors, particularly triple-negative breast cancers, and was highly predictive for decreased overall survival in human breast cancer patients. Collectively, our findings strongly implicate miR-181a as a predictive biomarker for breast cancer metastasis and patient survival, and consequently, as a potential therapeutic target in metastatic breast cancer.

MicroRNA-27a inhibitors alone or in combination with perifosine suppress the growth of gastric cancer cells

MicroRNA-27a (miR‑27a) is an oncogene that contributes to drug resistance in various types of cancer. However, the involvement of miR‑27a in gastric cancer has yet to be elucidated. Perifosine is an alkylphospholipid exhibiting antitumor activity as shown in both preclinical studies and clinical trials. The effects of perifosine on gastric cancer have yet to be determined. Therefore, this study was conducted to detect the role of miR‑27a and perifosine in human gastric cancer. miR‑27a was found to be expressed in human gastric cancer tissues and cell lines by quantitative reverse-transcription polymerase chain reaction (qRT‑PCR). The correlation between miR‑27a expression and clinicopathological characteristics of gastric cancer. We also explored the growth inhibitory effect of perifosine on human gastric cancer cells with or without co‑targeting miR‑27a by sulforhodamine B (SRB) assay. The results showed that miR‑27a expression was significantly upregulated in gastric cancer tissues, compared with their non‑tumor adjacent tissues. High expression levels of miR‑27a were associated with poor tumor histological grade (P=0.037). MiR‑27a inhibitors suppressed the growth of MGC‑803 cells. Assay results showed that perifosine exerted its activity selectively on the AGS cell line and the growth inhibitory effect of perifosine was enhanced significantly in combination with miR‑27a inhibitors in MGC‑803 cells. In conclusion, our results demonstrated that miR‑27a may be a therapeutic target and potential prognostic biological marker in gastric cancer. MiR‑27a inhibitors alone or in combination with perifosine may be a novel therapeutic approach against gastric cancer.

miRNA-miRNA interaction implicates for potential mutual regulatory pattern

BACKGROUND

Natural or endogenous sense/antisense miRNAs, located on sense and antisense strands in the same genomic region, respectively, are detected recently. However, little is known about these miRNA pairs, especially for their distributions in different animal species. We herein present systematic analysis of them in human, mouse and rat miRNAs, and their expression patterns based on deep sequencing datasets.

METHODS AND RESULTS

The phenomenon of miRNA-miRNA interaction could be detected in different animal species. The common miRNAs pairs were found across species. These miRNA pairs could form miRNA:miRNA duplex with complete complementary structure, and were prone to be located on specific chromosomes. They might be homologous miRNA genes (especially in human), or clustered in a gene cluster (especially in rat), or simultaneously detected in different genomic regions due to multicopy pre-miRNAs. Remarkably, some miRNA pairs, located in different genomic regions, also showed complementarity as well as endogenous sense/antisense miRNAs. Based on published deep sequencing datasets, one member of miRNA pairs always was abundantly expressed, whereas another was quite rare. Rare common target mRNAs of these miRNA pairs were predicted.

CONCLUSIONS

Interaction between miRNAs and significant expression divergence implied complex potential mutual regulatory pattern in the miRNA world. The study would enrich miRNA regulatory network.

Investigational agent MLN9708/2238 targets tumor-suppressor miR33b in MM cells

miRs play a critical role in tumor pathogenesis as either oncogenes or tumor-suppressor genes. However, the role of miRs and their regulation in response to proteasome inhibitors in multiple myeloma (MM) is unclear. In the current study, miR profiling in proteasome inhibitor MLN2238-treated MM.1S MM cells shows up-regulation of miR33b. Mechanistic studies indicate that the induction of miR33b is predominantly via transcriptional regulation. Examination of miR33b in patient MM cells showed a constitutively low expression. Overexpression of miR33b decreased MM cell viability, migration, colony formation, and increased apoptosis and sensitivity of MM cells to MLN2238 treatment. In addition, overexpression of miR33b or MLN2238 exposure negatively regulated oncogene PIM-1 and blocked PIM-1 wild-type, but not PIM-1 mutant, luciferase activity. Moreover, PIM-1 overexpression led to significant abrogation of miR33b- or MLN2238-induced cell death. SGI-1776, a biochemical inhibitor of PIM-1, triggered apoptosis in MM. Finally, overexpression of miR33b inhibited tumor growth and prolonged survival in both subcutaneous and disseminated human MM xenograft models. Our results show that miR33b is a tumor suppressor that plays a role during MLN2238-induced apoptotic signaling in MM cells, and these data provide the basis for novel therapeutic strategies targeting miR33b in MM.

miR-200c inhibits melanoma progression and drug resistance through down-regulation of BMI-1

MicroRNAs (miRNAs) are short noncoding RNAs that play crucial roles in tumorigenesis and tumor progression. Melanoma is the most aggressive skin cancer that is resistant or rapidly develops resistance to a variety of chemotherapeutic agents. The role of miRNAs in melanoma progression and drug resistance has not been well studied. Herein, we demonstrate that miR-200c is down-regulated in melanomas (primary and metastatic) compared with melanocytic nevi. Overexpression of miR-200c in melanoma cells resulted in significantly decreased cell proliferation and migratory capacity as well as drug resistance. miR-200c overexpression resulted in significant down-regulation of BMI-1, ABCG2, ABCG5, and MDR1 expression and in a concomitant increase in E-cadherin levels. Knockdown of BMI-1 showed similar effects as miR-200c overexpression in melanoma cells. In addition, miR-200c overexpression significantly inhibited melanoma xenograft growth and metastasis in vivo, and this correlated with diminished expression of BMI-1 and reduced levels of E-cadherin in these tumors. The effects of miR-200c on melanoma cell proliferation and migratory capacity and on self-renewal were rescued by overexpression of Bmi-1, and the reversal of these phenotypes correlated with a reduction in E-cadherin expression and increased levels of ABCG2, ABCG5, and MDR1. Taken together, these findings demonstrate a key role for miR-200c in melanoma progression and drug resistance. These results suggest that miR-200c may represent a critical target for increasing melanoma sensitivity to clinical therapies.

miR-200c is aberrantly expressed in leiomyomas in an ethnic-dependent manner and targets ZEBs, VEGFA, TIMP2, and FBLN5

MicroRNA-200c (miR-200c) through repression of specific target genes has been associated with cellular transition, tumorigenesis, and tissue fibrosis. We explored the expression and functional aspects of miR-200c in genesis of leiomyomas (LYO), benign uterine tumors with fibrotic characteristic. Using LYO and matched myometrium (MYO; n=76) from untreated and from patients exposed to hormonal therapies (GNRH agonist (GNRHa), Depo-Provera, and oral contraceptives), we found that miR-200c was expressed at significantly lower levels (P<0.05) in LYO as compared with MYO. These levels were lower in LYO from African Americans as compared with Caucasians, patients experiencing abnormal uterine bleeding and those exposed to GNRHa therapy. Gain-of-function of miR-200c in isolated leiomyoma smooth muscle cells (LSMCs), myometrial smooth muscle cells (MSMCs), and leiomyosarcoma cell line (SKLM-S1) repressed ZEB1/ZEB2 mRNAs and proteins, with concurrent increase in E-cadherin (CDH1) and reduction in vimentin expression, phenotypic alteration, and inhibition of MSMC and LSMC proliferations. We further validated TIMP2, FBLN5, and VEGFA as direct targets of miR-200c through interaction with their respective 3' UTRs, and other genes as determined by microarray analysis. At tissue levels, LYO expressed lower levels of TIMP2 and FBLN5 mRNAs but increased protein expressions, which to some extent altered due to hormonal exposure. Given the regulatory functions of ZEBs, VEGFA, FBLN5, and TIMP2 on cellular activities that promote cellular transition, angiogenesis, and matrix remodeling, we concluded that altered expression of miR-200c may have a significant impact on the outcome of LYO growth, maintenance of their mesenchymal and fibrotic characteristics, and possibly their associated symptoms.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.

miRNAs and cancer: an epigenetics view

microRNAs (miRNAs) are small, non-coding RNAs with critical roles in fine-tuning a wide array of biological processes including development, metabolism, and homeostasis. miRNAs expression, similarly to that of protein-coding genes, is regulated by multiple transcriptional networks as well as the epigenetic machinery. miRNA genes can be epigenetically regulated by DNA methylation or specific histone modifications. In addition, miRNAs can themselves repress key enzymes that drive epigenetic remodeling, generating regulatory circuits that have a significant effect in the transcriptional landscape of the cell. Recent evidences also suggest that miRNAs can directly modulate gene transcription in the nucleus through the recognition of specific target sites in promoter regions. Given the widespread distribution of epigenetic marks and miRNA target sites in the genome, the regulatory circuits linking both mechanisms are likely to have a major impact in genome transcription and cell physiology. Not surprisingly, tumor-associated aberrations in the miRNA or epigenetic machineries are widely distributed in human cancer, and we are just starting to understand their relevance in diagnosis, prognosis or therapy.

Loss of microRNA-205 expression is associated with melanoma progression

In this study, we used formalin-fixed paraffin-embedded melanocytic tumors to demonstrate reproducible alterations in microRNA expression in nevi compared with melanomas using a microarray platform. We validated those results in an independent set of nevi and melanomas by quantitative RT-PCR. miR-205 demonstrated a statistically significant, progressive diminution in expression from nevi to primary melanomas to metastatic melanomas. Enforced miR-205 expression in melanoma cells profoundly impairs cell motility and migration along with significantly decreased F-actin polymerization with only a modest reduction in cell proliferation. Using a xenograft model, melanoma cells overexpressing miR-205 exhibit a reduced migratory capacity compared with control tumor cells. Mechanistically, miR-205 overexpression results in decreased expression of the zinc-finger E-box binding homeobox 2 (ZEB2) mRNA and protein. This coincides with increased expression of E-cadherin mRNA and protein. Furthermore, re-introduction of ZEB2 into melanoma cells overexpressing miR-205 rescues these phenotypic effects and results in a restoration of cell migration and F-actin polymerization with a concomitant reduction in E-cadherin expression. Together, these results provide in vitro and in vivo evidence for miR-205 as a critical suppressor of melanoma cell migration.

EMT and induction of miR-21 mediate metastasis development in Trp53-deficient tumours

Missense mutations in TP53 gene promote metastasis in human tumours. However, little is known about the complete loss of function of p53 in tumour metastasis. Here we show that squamous cell carcinomas generated by the specific ablation of Trp53 gene in mouse epidermis are highly metastatic. Biochemical and genome-wide mRNA and miRNA analyses demonstrated that metastases are associated with the early induction of epithelial-mesenchymal transition (EMT) and deregulated miRNA expression in primary tumours. Increased expression of miR-21 was observed in undifferentiated, prometastatic mouse tumours and in human tumours characterized by p53 mutations and distant metastasis. The augmented expression of miR-21, mediated by active mTOR and Stat3 signalling, conferred increased invasive properties to mouse keratinocytes in vitro and in vivo, whereas blockade of miR-21 in a metastatic spindle cell line inhibits metastasis development. Collectively these data identify novel molecular mechanisms leading to metastasis in vivo originated by p53 loss in epithelia.

Hepatic microRNA profiles offer predictive and mechanistic insights after exposure to genotoxic and epigenetic hepatocarcinogens

In recent years, accumulating evidence supports the importance of microRNAs in liver physiology and disease; however, few studies have examined the involvement of these noncoding genes in chemical hepatocarcinogenesis. Here, we examined the liver microRNA profile of male Fischer rats exposed through their diet to genotoxic (2-acetylaminofluorene) and epigenetic (phenobarbital, diethylhexylphthalate, methapyrilene HCL, monuron, and chlorendic acid) chemical hepatocarcinogens, as well as to non-hepatocarcinogenic treatments (benzophenone, and diethylthiourea) for 3 months. The effects of these treatments on liver pathology, plasma clinical parameters, and liver mRNAs were also determined. All hepatocarcinogens affected the expression of liver mRNAs, while the hepatic microRNA profiles were associated with the mode of action of the chemical treatments and corresponded to chemical carcinogenicity. The three nuclear receptor-activating chemicals (phenobarbital, benzophenone, and diethylhexylphthalate) were characterized by the highly correlated induction of the miR-200a/200b/429, which is involved in protecting the epithelial status of cells and of the miR-96/182 clusters. The four non-nuclear receptor-activating hepatocarcinogens were characterized by the early, persistent induction of miR-34, which was associated with DNA damage and oxidative stress in vivo and in vitro. Repression of this microRNA in a hepatoma cell line led to increased cell growth; thus, miR-34a could act to block abnormal cell proliferation in cells exposed to DNA damage or oxidative stress. This study supports the proposal that hepatic microRNA profiles could assist in the earlier evaluation and identification of hepatocarcinogens, especially those acting by epigenetic mechanisms.

miRNA-125b regulates TNF-α production in CD14+ neonatal monocytes via post-transcriptional regulation

Neonates, although deficient in cell immunity, frequently reveal sepsis with augmented proinflammatory reactions. Here, we found that neonatal monocytes produced significantly higher TNF-α mRNA and protein than adult monocytes. Assessment of the transcriptional factor found no significant difference of NF-κB p65 level between neonatal and adult monocytes. Addition of Act D to access the half-life of TNF-α mRNA revealed no significant difference of the LPS-induced TNF-α mRNA half-life between them, whereas CHX increased neonatal TNF-α mRNA significantly. This suggests that a post-transcriptional mechanism involves the augmentation of TNF-α production by neonatal monocytes. To examine whether miRNA was involved in the post-transcriptional regulation, differential displays of miRNA array between neonatal and adult MNCs were performed, along with the discovery of hsa-miR-103, hsa-miR-125b, hsa-miR-130a, hsa-miR-454-3p, and hsa-miR-542-3p, which were greater than a twofold decrease or increase after LPS treatment for 4 h. The functional validation identified that miR-125b decreased significantly in association with higher TNF-α expression by neonatal monocytes after LPS stimulation. Transfection of the miR-125b precursor into neonatal monocytes significantly repressed the TNF-α mRNA and protein expression, suggesting that miR-125b negatively regulates TNF-α expression in neonatal monocytes. Modulation of miRNA expression may be used to regulate TNF-α production in newborns with altered proinflammatory reactions.

Endometrial miR-200c is altered during transformation into cancerous states and targets the expression of ZEBs, VEGFA, FLT1, IKKβ, KLF9, and FBLN5

A number of microRNAs (miRNAs), including miR-200 family, are aberrantly expressed in endometriosis and endometrial cancer. Here we assessed the expression and functional aspects of miR-200c in endometrial tissues (N = 52) from normal endometrial biopsies (N = 15), endometrial tissues including those exposed to hormonal therapies (N = 20), and grade I-III endometrial cancer (N = 17). miR-200c expression was elevated in normal endometrial biopsies from mid- and late-luteal phase, and in endometrial tumors as compared to endometrial tissues from peri- and postmenopausal period (P < .05) and its pattern of temporal expression displayed an inverse relationship with the expression of ZEBs. The expression of E-cadherin (CDH1) varied, but expressed at low levels, specifically in endometrial tissues and endometrial tumors. The endometrial expression of ZEBs and CDH1 in patients who were exposed to Depo-Provera and gonadotropin-releasing hormone agonist GnRHa displayed a trend toward lower expression as compared to proliferative phase; however, treatment of Ishikawa cells with 17β-estradiol, progesterone, and medroxy progesterone acetate had modest effects on the expression of miR-200c and ZEBs without affecting CDH1 expression. Gain of function of miR-200c in Ishikawa cells repressed ZEBs, as well as VEGFA, FLT1, IKKβ, and KLF9 expression at transcriptional and translational levels through direct interaction with their respective 3'untranslated regions and increased the rate of their proliferation. These results indicated that endometrial miR-200c expression undergoes dynamic changes during transition from normal into cancerous states; possibly influenced by hormonal milieu and by targeting the expression of specific genes with key regulatory functions in cellular transformation, inflammation, and angiogenesis may influence these events during normal and disease progression.

MiR-139 inhibits invasion and metastasis of colorectal cancer by targeting the type I insulin-like growth factor receptor

MicroRNAs (miRNAs), which are noncoding RNAs that regulate gene expression, are involved in tumor metastasis. In this study, we describe the down-regulation and function of miR-139 in colorectal cancer (CRC) metastasis. MiR-139 was found underexpressed in 34 CRC tissues compared to their corresponding nontumor tissues. Decreased miR-139 in CRC tissue was associated with disease progression and metastasis. Re-expression of miR-139 did not inhibit CRC cell growth but suppresses CRC cell metastasis and invasion in vitro and in vivo. MiR-139 might suppress CRC cells invasion and metastasis by targeting type I insulin-like growth factor receptor (IGF-IR). We also found miR-139 directed migration inactivation of human CRC cells involves down-regulation of matrix metalloproteinase 2 (MMP-2). The IGF-IR/MEK/ERK signaling was inhibited by miR-139 overexpression and then resulted in MMP-2 promoter suppression. Taken together, our results provide evidence that miR-139 might function as a metastasis suppressor in CRC. Targeting miR-139 may provide a strategy for blocking CRC metastasis.

Prognostic implications of microRNA-100 and its functional roles in human epithelial ovarian cancer

Dysregulation of microRNAs (miRNAs) has been found to be associated with a variety of diseases, including epithelial ovarian cancer (EOC). Recently, miR-100 was reported to be downregulated in human ovarian carcinoma, however, the clinical significance and functional roles of miR-100 expression in human EOC are unclear. TaqMan real-time quantitative RT-PCR assay was performed to detect the expression of miR-100 in 98 EOC tissues and 15 adjacent normal epithelial tissues. The relationship between miR-100 expression and clinicopathological factors in 98 EOC patients was statistically analyzed. The effect of miR-100 expression on patient survival was determined. Finally, the role of miR-100 in EOC cell growth and its possible mechanisms were analyzed with miR-100 precursor or inhibitor-transfected cells. We showed that the level of miR-100 was significantly lower in EOC tissues compared to adjacent normal tissues. Low miR-100 expression was found to be closely correlated with advanced FIGO stage, higher serum CA125 expression level and lymph node involvement. Also, low miR-100 expression was correlated with shorter overall survival of EOC patients, and multivariate analysis showed that the status of miR-100 expression was an independent predictor of overall survival in EOC. Additionally, miR-100 could affect the growth of EOC cells by post-transcriptionally regulating polo-like kinase 1 (PLK1) expression. Together, these results suggest that low miR-100 expression may be an independent poor prognostic factor and miR-100 can function as a tumor suppressor by targeting PLK1 in human EOCs.

Involvement of microRNA-93, a new regulator of PTEN/Akt signaling pathway, in regulation of chemotherapeutic drug cisplatin chemosensitivity in ovarian cancer cells

The mechanisms underlying ovarian cancer cell resistance to cisplatin (CDDP) are not fully understood. MicroRNAs (miRNAs) play important roles in tumorigenesis and drug resistance. In this paper, we utilized microRNA array and real-time PCR to show that miR-93 is significantly up-regulated in cisplatin-resistant ovarian cancer cells. In vitro assays show that over-expression and knock-down of miR-93 regulate apoptotic activity, and thereby cisplatin chemosensitivity, in ovarian cells. Furthermore, we found that miR-93 can directly target PTEN, and participates in the regulation of the AKT signaling pathway. MiR-93 inversely correlates with PTEN expression in CDDP-resistant and sensitive human ovarian cancer tissues. These results may have implications for therapeutic strategies aiming to overcome ovarian cancer cell resistance to cisplatin.

RAC1 activation mediates Twist1-induced cancer cell migration

Epithelial-mesenchymal transition (EMT), which is characterized by the suppression of the adhesion protein E-cadherin, is a crucial process that promotes metastasis and stem-like properties of cancer cells. However, the dissociation of cellular aggregates is not sufficient to explain why cancer cells move, and the motile nature of cancer cells undergoing EMT remains elusive. Here, we identify a mechanism in which the EMT inducer Twist1 elicits cancer cell movement through activation of RAC1. Twist1 cooperates with BMI1 to suppress let-7i expression, which results in upregulation of NEDD9 and DOCK3, leading to RAC1 activation and enabling mesenchymal-mode movement in three-dimensional environments. Moreover, the suppression of let-7i contributes to Twist1-induced stem-like properties. Clinically, activation of the Twist1-let-7i-NEDD9 axis in head and neck cancer patients correlates with tumour invasiveness and worse outcome. Our results uncover an essential mechanism to explain how Twist1 induces the motile stem-like cancer cell phenotype beyond simply suppressing E-cadherin.

Biochemical role of the collagen-rich tumour microenvironment in pancreatic cancer progression

PDAC (pancreatic ductal adenocarcinoma) is among the most deadly of human malignances. A hallmark of the disease is a pronounced collagen-rich fibrotic extracellular matrix known as the desmoplastic reaction. Intriguingly, it is precisely these areas of fibrosis in which human PDAC tumours demonstrate increased expression of a key collagenase, MT1-MMP [membrane-type 1 MMP (matrix metalloproteinase); also known as MMP-14]. Furthermore, a cytokine known to mediate fibrosis in vivo, TGF-β1 (transforming growth factor-β1), is up-regulated in human PDAC tumours and can promote MT1-MMP expression. In the present review, we examine the regulation of PDAC progression through the interplay between type I collagen (the most common extracellular matrix present in human PDAC tumours), MT1-MMP and TGF-β1. Specifically, we examine the way in which signalling events through these pathways mediates invasion, regulates microRNAs and contributes to chemoresistance.

MicroRNA-200 is commonly repressed in conjunctival MALT lymphoma, and targets cyclin E2

BACKGROUND

Aberrant microRNA expression is implicated in cancer initiation and progression. We sought to identify dysregulated miRNAs in conjunctival mucosa-associated lymphoid tissue (MALT) lymphoma, and investigated their biological significance.

METHODS

The profiles of miRNAs in conjunctival MALT lymphoma and normal adjacent tissues were investigated by microRNA microarray of four pairs of surgically removed conjunctival MALT lymphoma tissues and matched controls. The results of microarray were further confirmed in 14 paired conjunctival MALT lymphoma samples (including the former four pairs) using quantitative RT-PCR. The functional effect of miR-200 was examined further. A luciferase reporter assay was performed to confirm the predicted target.

RESULTS

The microarray results revealed upregulated miR-150/155, and downregulated miR-184, miR-200a, b, c, and miR-205. These findings were confirmed by quantitative RT-PCR. Targetscan analysis suggested cyclin E2 as potential target of miR-200a, b, c. Luciferase reporter assay using vectors containing the 3'UTR of cyclin E2 showed that miR-200a, b, c could suppress luciferase activities. RT-PCR and immunoblotting studies revealed that overexpression of miR-200a, b, c reduced the mRNA and protein levels of cyclin E2 respectively.

CONCLUSIONS

We demonstrated that miRNAs were dysregulated in conjunctival MALT lymphoma, and dysregulation of the miR-200 family could be involved in the pathogenesis and progression of the disease.

MicroRNA-148a is silenced by hypermethylation and interacts with DNA methyltransferase 1 in gastric cancer

Studies have shown that microRNA-148a (miR-148a) was proved to be silenced while DNA methyltransferase 1 (DNMT1) was over-expressed in gastric cancer. But the mechanism of aberrant expression of miR-148a and DNMT1 and their relationships in gastric cancer are still unknown. The aims of this study were to investigate the expression profile of miR-148a and DNMT1 and reveal whether they have any relationships. We used reverse-transcriptase quantitative real-time PCR, methylation-specific PCR and Western blot to measure the level of miR-148a expression, DNA methylation level and DNMT1 expression, respectively. Gastric cancer cells were transfected with plasmid or siRNA or treated with 5-aza-2'-deoxycytidine. Cell proliferation and apoptosis were detected by cell counting and flow cytometric analysis. In this study, we demonstrated that gastric cancer tissues and cell lines displayed a consistent down-regulation of miR-148a and hypermethylation of promoter region. DNMT1 was over-expressed in primary tumors and cell lines, while knockdown of DNMT1 using siRNA could decrease methylation level of miR-148a promoter and restore its expression. Furthermore, ectopic over-expression of miR-148a in cancer cell lines caused reduction in DNMT1 expression and inhibited cell proliferation, but no obvious change was found in apoptosis rate. These results suggest that miR-148a is inactivated by DNA hypermethylation of promoter region in gastric cancer, which is mediated through DNMT1 over-expression. Additionally, the silence of miR-148a reduces its suppression to DNMT1 in gastric cancer, and this may in turn result in over-expression of DNMT1 and promote DNA hypermethylation.

MicroRNA-205 functions as a tumor suppressor in human glioblastoma cells by targeting VEGF-A

MicroRNAs (miRNAs) are endogenously small non-coding RNAs which are key post-transcriptional regulators of gene expression. Deregulation of miRNAs is common in human tumorigenesis. We report that miRNA-205 is significantly down-regulated in glioma cell lines and tissue specimens. Ectopic expression of miRNA-205 induces apoptosis, cell cycle arrest, impairs cell viability, clonability and invasive properties of glioma cells. We further demonstrate that miRNA-205 can specifically suppress expression of VEGF-A by directly interacting with the putative miRNA-205 binding site at the 3′-UTR. Identification of VEGF-A as a direct target for miRNA-205 may imply that miRNA-205 is a novel target for glioma therapy. Taken together, the present study for the first time provides evidence that miRNA-205 is a glioma-specific tumor suppressor by targeting VEGF-A.