A miR-200 microRNA cluster as prognostic marker in advanced ovarian cancer

Effect of miR-451 on the biological behavior of the esophageal carcinoma cell line EC9706

BACKGROUND

MicroRNAs play important roles in coordinating a variety of cellular processes. Abnormal expression of miRNAs has been linked to several cancers. However, the functional role of miR-451 in esophageal squamous cell carcinoma remains unclear.

AIMS

The present study explored the effects of miR-451 on the biological behavior of the esophageal carcinoma cell line EC9706.

METHODS

Synthetic miR-451 mimics were transfected into EC9706 cells using Lipofectamine™ 2000. The expression of miR-451 was analyzed by RT-PCR and the expressions of Bcl-2, AKT and phosphorylated AKT were analyzed by Western blotting. The MTT assay, soft agar colony formation assay, transwell assay and FACS were used to assess the effect of miR-451 on EC9706 cell proliferation, invasion, metastasis and apoptosis. Tumor growth was assessed by subcutaneous inoculation of cells into BALB/c nude mice.

RESULTS

In comparison to the controls, a significant increase in the expression of miR-451 was associated with significantly decreased expressions of Bcl-2, AKT and p-AKT, and a significant increase in the apoptosis rate. The number of cell clones was significantly decreased by miR-451 expression, which also caused the inhibition of cell proliferation. The average number of cells penetrating the matrigel was significantly lower than the controls. Injection of miR-451 inhibited tumor growth in a xenograft model.

CONCLUSIONS

Upregulated expression of miR-451 induced apoptosis and suppressed cell proliferation, invasion and metastasis in the esophageal carcinoma cell line EC9706. In addition, injection of miR-451 inhibited tumor growth in a xenograft model of esophageal cancer.

Three-mode electrochemical sensing of ultralow microRNA levels

MicroRNAs (miRNAs) are an emerging class of biomarkers that are frequently deregulated in cancer cells and have shown great promise for cancer classification and prognosis. In this work, we developed a three-mode electrochemical sensor for detection and quantitation of ultralow levels of miRNAs in a wide dynamic range of measured concentrations. The sensor facilitates three detection modalities based on hybridization (H-SENS), p19 protein binding (P-SENS), and protein displacement (D-SENS). The combined three-mode sensor (HPD-SENS) identifies as low as 5 aM or 90 molecules of miRNA per 30 μL of sample without PCR amplification, and can be operated within the dynamic range from 10 aM to 1 μM. The HPD sensor is made on a commercially available gold nanoparticles-modified electrode and is suitable for analyzing multiple miRNAs on a single electrode. This three-mode sensor exhibits high selectivity and specificity and was used for sequential analysis of miR-32 and miR-122 on one electrode. In addition, the H-SENS can recognize miRNAs with different A/U and G/C content and distinguish between a fully matched miRNA and a miRNA comprising either a terminal or a middle single base mutation. Furthermore, the H- and P-SENS were successfully employed for direct detection and profiling of three endogenous miRNAs, including hsa-miR-21, hsa-miR-32, and hsa-miR-122 in human serum, and the sensor results were validated by qPCR.

MiR-200c and HuR in ovarian cancer

BACKGROUND

MicroRNAs in solid malignancies can behave as predictors of either good or poor outcome. This is the case with members of the miR-200 family, which are the primary regulators of the epithelial to mesenchymal transition and have been reported to act as both oncogenes and tumor suppressors. This study assessed the role of miR-200c as regulator of class III β-tubulin (TUBB3), a factor associated with drug-resistance and poor prognosis in ovarian cancer.

METHODS

Expression of miR-200c was assessed in a panel of ovarian cancer cell lines with inherent or acquired drug-resistance. Stable overexpression of miR-200c was obtained in A2780 and Hey cell lines. Crosslinking-coupled affinity purification method and ribonucleic-immunoprecipitation assay were used to characterise the complexes between miR-200c, HuR and 3'UTR region of TUBB3 mRNA. Nanofluidic technology and immunohistochemistry were used to analyze the expression of HuR, TUBB3 and miR-200c in 220 ovarian cancer patients.

RESULTS

In a panel of ovarian adenocarcinoma cell lines, we observed a direct correlation between miR-200c expression and chemoresistance. In A2780 cells miR-200c targeted TUBB3 3'UTR, while a positive correlation was observed between miR-200c and TUBB3 expression in most of the other cell lines. Through the analysis of 3'UTR-associated complexes, we found that the miR-200c can increase the association of the RNA binding protein HuR with TUBB3 mRNA, whereas HuR binding enhanced TUBB3 mRNA translation. Most importantly, in our analysis on 220 ovarian cancer patients we observed that overexpression of miR-200c correlated with poor or good outcome depending on the cellular localization of HuR.

CONCLUSION

This study suggests a model for the combined regulatory activity of miR-200c and HuR on TUBB3 expression in ovarian cancer. When HuR is nuclear, high expression of miR-200c inhibits TUBB3 expression and results in a good prognosis, whereas when HuR occurs in cytoplasm, the same miRNA enhances TUBB3 expression and produces a poor outcome. These findings reveal the usefulness of multidimensional analysis in the investigation of the prognostic role of miRNA expression.

Regulatory networks defining EMT during cancer initiation and progression

Epithelial to mesenchymal transition (EMT) is essential for driving plasticity during development, but is an unintentional behaviour of cells during cancer progression. The EMT-associated reprogramming of cells not only suggests that fundamental changes may occur to several regulatory networks but also that an intimate interplay exists between them. Disturbance of a controlled epithelial balance is triggered by altering several layers of regulation, including the transcriptional and translational machinery, expression of non-coding RNAs, alternative splicing and protein stability.

MicroRNA-200a promotes anoikis resistance and metastasis by targeting YAP1 in human breast cancer

PURPOSE

The process of metastases involves the dissociation of cells from the primary tumor, penetration into the basement membrane, invasion, and exiting from the vasculature to seed and colonize distant tissues. miR-200a is involved in this multistep metastatic cascade. This study aimed to test the hypothesis that miR-200a promotes metastasis through increased anoikis resistance in breast cancer.

EXPERIMENTAL DESIGN

Breast cancer cells transfected with mimic or inhibitor for miR-200a were assayed for anoikis in vitro. miR-200a expression was assessed by quantitative real-time PCR (qRT-PCR). Luciferase assays, colony formation assays, and animal studies were conducted to identify the targets of miR-200a and the mechanism by which it promotes anoikis resistance.

RESULTS

We found that overexpression of miR-200a promotes whereas inhibition of miR-200a suppresses anoikis resistance in breast cancer cells. We identified Yes-associated protein 1 (YAP1) as a novel target of miR-200a. Our data showed that targeting of YAP1 by miR-200a resulted in decreased expression of proapoptotic proteins, which leads to anoikis resistance. Overexpression of miR-200a protected tumor cells from anoikis and promoted metastases in vivo. Furthermore, knockdown of YAP1 phenocopied the effects of miR-200a overexpression, whereas restoration of YAP1 in miR-200a overexpressed breast cancer cells reversed the effects of miR-200a on anoikis and metastasis. Remarkably, we found that YAP1 expression was inversely correlated with miR-200a expression in breast cancer clinical specimens, and miR-200a expression was associated with distant metastasis in patients with breast cancer.

CONCLUSIONS

Our data suggest that miR-200a functions as anoikis suppressor and contributes to metastasis in breast cancer.

Curcumin, a component of turmeric: from farm to pharmacy

Curcumin, an active polyphenol of the golden spice turmeric, is a highly pleiotropic molecule with the potential to modulate the biological activity of a number of signaling molecules. Traditionally, this polyphenol has been used in Asian countries to treat such human ailments as acne, psoriasis, dermatitis, and rash. Recent studies have indicated that curcumin can target newly identified signaling pathways including those associated with microRNA, cancer stem cells, and autophagy. Extensive research from preclinical and clinical studies has delineated the molecular basis for the pharmaceutical uses of this polyphenol against cancer, pulmonary diseases, neurological diseases, liver diseases, metabolic diseases, autoimmune diseases, cardiovascular diseases, and numerous other chronic diseases. Multiple studies have indicated the safety and efficacy of curcumin in numerous animals including rodents, monkeys, horses, rabbits, and cats and have provided a solid basis for evaluating its safety and efficacy in humans. To date, more than 65 human clinical trials of curcumin, which included more than 1000 patients, have been completed, and as many as 35 clinical trials are underway. Curcumin is now used as a supplement in several countries including the United States, India, Japan, Korea, Thailand, China, Turkey, South Africa, Nepal, and Pakistan. In this review, we provide evidence for the pharmaceutical uses of curcumin for various diseases.

MicroRNAs in human cancer

Mature microRNAs (miRNAs) are single-stranded RNA molecules of 20-23-nucleotide (nt) length that control gene expression in many cellular processes. These molecules typically reduce the translation and stability of mRNAs, including those of genes that mediate processes in tumorigenesis, such as inflammation, cell cycle regulation, stress response, differentiation, apoptosis, and invasion. miRNA targeting is initiated through specific base-pairing interactions between the 5' end ("seed" region) of the miRNA and sites within coding and untranslated regions (UTRs) of mRNAs; target sites in the 3' UTR lead to more effective mRNA destabilization. Since miRNAs frequently target hundreds of mRNAs, miRNA regulatory pathways are complex. To provide a critical overview of miRNA dysregulation in cancer, we first discuss the methods currently available for studying the role of miRNAs in cancer and then review miRNA genomic organization, biogenesis, and mechanism of target recognition, examining how these processes are altered in tumorigenesis. Given the critical role miRNAs play in tumorigenesis processes and their disease specific expression, they hold potential as therapeutic targets and novel biomarkers.

Oxidative stress and cancer: an overview

Reactive species, which mainly include reactive oxygen species (ROS), are products generated as a consequence of metabolic reactions in the mitochondria of eukaryotic cells. In normal cells, low-level concentrations of these compounds are required for signal transduction before their elimination. However, cancer cells, which exhibit an accelerated metabolism, demand high ROS concentrations to maintain their high proliferation rate. Different ways of developing ROS resistance include the execution of alternative pathways, which can avoid large amounts of ROS accumulation without compromising the energy demand required by cancer cells. Examples of these processes include the guidance of the glycolytic pathway into the pentose phosphate pathway (PPP) and/or the generation of lactate instead of employing aerobic respiration in the mitochondria. Importantly, ROS levels can be used as a thermostat to monitor the damage that cells can bear. The implications for ROS regulation are highly significant for cancer therapy because commonly used radio- and chemotherapeutic drugs influence tumor outcome through ROS modulation. Moreover, the discovery of novel biomarkers that are able to predict the clinical response to pro-oxidant therapies is a crucial challenge to overcome to allow for the personalization of cancer therapies.

Elevated levels of circulating microRNA-200 family members correlate with serous epithelial ovarian cancer

Background

There is a critical need for improved diagnostic markers for high grade serous epithelial ovarian cancer (SEOC). MicroRNAs are stable in the circulation and may have utility as biomarkers of malignancy. We investigated whether levels of serum microRNA could discriminate women with high-grade SEOC from age matched healthy volunteers.

Methods

To identify microRNA of interest, microRNA expression profiling was performed on 4 SEOC cell lines and normal human ovarian surface epithelial cells. Total RNA was extracted from 500 μL aliquots of serum collected from patients with SEOC (n = 28) and age-matched healthy donors (n = 28). Serum microRNA levels were assessed by quantitative RT-PCR following preamplification.

Results

microRNA (miR)-182, miR-200a, miR-200b and miR-200c were highly overexpressed in the SEOC cell lines relative to normal human ovarian surface epithelial cells and were assessed in RNA extracted from serum as candidate biomarkers. miR-103, miR-92a and miR -638 had relatively invariant expression across all ovarian cell lines, and with small-nucleolar C/D box 48 (RNU48) were assessed in RNA extracted from serum as candidate endogenous normalizers. No correlation between serum levels and age were observed (age range 30-79 years) for any of these microRNA or RNU48. Individually, miR-200a, miR-200b and miR-200c normalized to serum volume and miR-103 were significantly higher in serum of the SEOC cohort (P < 0.05; 0.05; 0.0005 respectively) and in combination, miR-200b + miR-200c normalized to serum volume and miR-103 was the best predictive classifier of SEOC (ROC-AUC = 0.784). This predictive model (miR-200b + miR-200c) was further confirmed by leave one out cross validation (AUC = 0.784).

Conclusions

We identified serum microRNAs able to discriminate patients with high grade SEOC from age-matched healthy controls. The addition of these microRNAs to current testing regimes may improve diagnosis for women with SEOC.

Expression profiles of microRNAs from lactating and non-lactating bovine mammary glands and identification of miRNA related to lactation

Background

MicroRNAs (miRNAs) have been implicated in the regulation of milk protein synthesis and development of the mammary gland (MG). However, the specific functions of miRNAs in these regulations are not clear. Therefore, the elucidation of miRNA expression profiles in the MG is an important step towards understanding the mechanisms of lactogenesis.

Results

Two miRNA libraries were constructed from MG tissues taken from a lactating and a non-lactating Holstein dairy cow, respectively, and the short RNA sequences (18–30 nt) in these libraries were sequenced by Solexa sequencing method. The libraries included 885 pre-miRNAs encoding for 921 miRNAs, of which 884 miRNAs were unique sequences and 544 (61.5%) were expressed in both periods. A custom-designed microarray assay was then performed to compare miRNA expression patterns in the MG of lactating and non-lactating dairy cows. A total of 56 miRNAs in the lactating MG showed significant differences in expression compared to non-lactating MG (P<0.05). Integrative miRNA target prediction and network analysis approaches were employed to construct an interaction network of lactation-related miRNAs and their putative targets. Using a cell-based model, six miRNAs (miR-125b, miR-141, miR-181a, miR-199b, miR-484 and miR-500) were studied to reveal their possible biological significance.

Conclusion

Our study provides a broad view of the bovine MG miRNA expression profile characteristics. Eight hundred and eighty-four miRNAs were identified in bovine MG. Differences in types and expression levels of miRNAs were observed between lactating and non-lactating bovine MG. Systematic predictions aided in the identification of lactation-related miRNAs, providing insight into the types of miRNAs and their possible mechanisms in regulating lactation.

Early detection biomarkers for ovarian cancer

Despite the widespread use of conventional and contemporary methods to detect ovarian cancer development, ovarian cancer remains a common and commonly fatal gynecological malignancy. The identification and validation of early detection biomarkers highly specific to ovarian cancer, which would permit development of minimally invasive screening methods for detecting early onset of the disease, are urgently needed. Current practices for early detection of ovarian cancer include transvaginal ultrasonography, biomarker analysis, or a combination of both. In this paper we review recent research on novel and robust biomarkers for early detection of ovarian cancer and provide specific details on their contributions to tumorigenesis. Promising biomarkers for early detection of ovarian cancer include KLK6/7, GSTT1, PRSS8, FOLR1, ALDH1, and miRNAs.

Overcoming challenges of ovarian cancer stem cells: novel therapeutic approaches

Understanding the genetic and molecular mechanisms of ovarian cancer has been the focus of research efforts working toward the greater goal of improving cancer therapy for patients with residual disease after initial treatment with conventional surgery and neoadjuvant chemotherapy. The focus of this review will be centered on new therapeutic strategies based on Cancer Stem Cells studies of chemoresistant subpopulations, the prevention of metastasis, and individualized therapy in order to find the most successful combination of treatments to effectively treat human ovarian cancer. We reviewed recent literature (1993-2011) of novel treatment approaches to ovarian cancer stem cells. As the focus of ovarian cancer investigation has centered on the cancer stem cell model and the complexities that it presents in the development of effective treatments, the future of treating ovarian cancer lies in utilizing individualized treatment systems that include enhancing existing treatments, aiming for novel therapy targets, managing the plasticity of stem cells to induce cellular differentiation, and regulating oncogenic signaling pathways.

Current status and implications of microRNAs in ovarian cancer diagnosis and therapy

Ovarian cancer is the fifth most common cancer among women and causes more deaths than any other type of female reproductive cancer. Currently, treatment of ovarian cancer is based on the combination of surgery and chemotherapy. While recurrent ovarian cancer responds to additional chemotherapy treatments, the progression-free interval becomes shorter after each cycle, as chemo-resistance increases until the disease becomes incurable. There is, therefore, a strong need for prognostic and predictive markers to help optimize and personalize treatment in order to improve the outcome of ovarian cancer. An increasing number of studies indicate an essential role for microRNAs in ovarian cancer progression and chemo-resistance. MicroRNAs (miRNAs) are small endogenous non-coding RNAs (~22bp) which are frequently dysregulated in cancer. Typically, miRNAs are involved in crucial biological processes, including development, differentiation, apoptosis and proliferation. Two families of miRNAs, miR-200 and let-7, are frequently dysregulated in ovarian cancer and have been associated with poor prognosis. Both have been implicated in the regulation of epithelial-to-mesenchymal transition, a cellular transition associated with tumor aggressiveness, tumor invasion and chemo-resistance. Moreover, miRNAs also have possible implications for improving cancer diagnosis; for example miR-200 family, let-7 family, miR-21 and miR-214 may be useful in diagnostic tests to help detect ovarian cancer at an early stage. Additionally, the use of multiple target O-modified antagomirs (MTG-AMO) to inhibit oncogenic miRNAs and miRNA replacement therapy for tumor suppressor miRNAs are essential tools for miRNA based cancer therapeutics. In this review we describe the current status of the role miRNAs play in ovarian cancer and focus on the possibilities of microRNA-based therapies and the use of microRNAs as diagnostic tools.

Ovarian cancer stem cells: working towards the root of stemness

Despite medical advances made over the past decade, ovarian cancer remains one of the more lethal gynecologic cancers in the United States. While current therapeutic strategies are relatively effective, there is a high incidence of recurrent chemoresistant disease. This has been attributed, in part, to a regenerative tumor cell sub-population that has acquired stem cell properties which allows these cells to escape standard chemotherapeutics and drive recurrent disease. To date, a number of laboratories have identified these cancer stem cell (CSC) sub-populations in ovarian cancer cell lines, tumors or ascites and the collective findings suggest ovarian CSCs are likely to be as heterogeneous as the disease itself. Moreover, the multiple ovarian histophenotypes and possible sites of disease origin together with the potential for differential hierarchal contributions of multiple CSCs populations represent significant challenges to the identification, functional characterization and therapeutic targeting of ovarian CSC. This review will highlight the markers and methodology currently used to identify and isolate these cells. We will discuss some of the underlying ovarian CSC biology, the signaling pathways implicated in their survival, replication and differentiation and potential therapeutic targeting strategies.

Restoration of miR-200c to ovarian cancer reduces tumor burden and increases sensitivity to paclitaxel

A therapeutic intervention that could decrease tumor burden and increase sensitivity to chemotherapy would have a significant impact on the high morbidity rate associated with ovarian cancer. miRNAs have emerged as potential therapeutic candidates due to their ability to downregulate multiple targets involved in tumor progression and chemoresistance. miRNA-200c (miR-200c) is downregulated in ovarian cancer cell lines and stage III ovarian tumors, and low miR-200c correlates with poor prognosis. miR-200c increases sensitivity to taxanes in vitro by targeting class III β-tubulin gene (TUBB3), a tubulin known to mediate chemoresistance. Indeed, we find that patients with tumors having low TUBB3 had significantly prolonged survival (average survival 52.73 ± 4.08 months) as compared with those having high TUBB3 (average survival 42.56 ± 3.19 months). miR-200c also targets TrkB, a mediator of resistance to anoikis. We show that restoration of miR-200c to ovarian cancer cells results in increased anoikis sensitivity and reduced adherence to biologic substrates in vitro. Because both chemo- and anoikis-resistance are critical steps in the progression of ovarian cancer, we sought to determine how restoration of miR-200c affects tumor burden and chemosensitivity in an in vivo preclinical model of ovarian cancer. Restoration of miR-200c in an intraperitoneal xenograft model of human ovarian cancer results in decreased tumor formation and tumor burden. Furthermore, even in established tumors, restoration of miR-200c, alone or in combination with paclitaxel, results in significantly decreased tumor burden. Our study suggests that restoration of miR-200c immediately before cytotoxic chemotherapy may allow for a better response or lower effective dose.

MiRNA-429 suppresses the growth of gastric cancer cells in vitro

Micro-RNAs (miRNAs) have been found to be implicated in a very wide range of physiological processes. This study was aimed to investigate the regulation of miRNA-429 (miR-429) in gastric cancer cells on cell proliferation and apoptosis. Quantitative PCR was employed to detect the expressions of miR-429 after eukaryotic expression plasmid of miR-429 and its inhibitor were transiently transfected into poorly differentiated human gastric cancer cell line BGC823. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assays were used to examine proliferation ability. Apoptosis was analyzed by flow cytometry after transfection. The results showed that 48 h after transfection, overexpression of miR-429 reached maximum efficiency. Compared with mock transfection, miR-429 inhibited tumor cell proliferation significantly (P < 0.05) at 48 h and 72 h. of Overexpression of miR-429 promoted tumor cell apoptosis when compared with mock transfected cells (P < 0.05). On the contrary, miR-429 inhibitor promoted tumor cell proliferation and inhibited apoptosis when compared with controls (P < 0.05). Our results suggested that miRNA-429 may serve as a tumor suppressor during tumorigenesis of gastric cancer and may be a potential gastric cancer therapeutic target.

MicroRNAs in the p53 network: micromanagement of tumour suppression

In recent years, microRNAs (miRNAs) have been identified as mediators of tumour suppression and stress responses exerted by the p53 tumour suppressor. p53-regulated miRNAs contribute to tumour suppression by controlling the expression of central components of multiple processes, including cell cycle progression, epithelial-mesenchymal transition, stemness, metabolism, cell survival and angiogenesis. The expression and activity of p53 itself is also under the control of miRNAs. Finally, genetic and epigenetic alterations identified in the p53-miRNA network indicate that these pathways are important for the initiation and progression of tumours. In the future, knowledge about the p53-miRNA network may be able to be exploited for diagnostic and therapeutic approaches in cancer prevention and treatment.

MicroRNA expression in ovarian carcinoma and its correlation with clinicopathological features

Background

MicroRNA (miRNA) expression is known to be deregulated in ovarian carcinomas. However, limited data is available about the miRNA expression pattern for the benign or borderline ovarian tumors as well as differential miRNA expression pattern associated with histological types, grades or clinical stages in ovarian carcinomas. We defined patterns of microRNA expression in tissues from normal, benign, borderline, and malignant ovarian tumors and explored the relationship between frequently deregulated miRNAs and clinicopathologic findings, response to therapy, survival, and association with Her-2/neu status in ovarian carcinomas.

Methods

We measured the expression of nine miRNAs (miR-181d, miR-30a-3p, miR-30c, miR-30d, miR-30e-3p, miR-368, miR-370, miR-493-5p, miR-532-5p) in 171 formalin-fixed, paraffin-embedded ovarian tissue blocks as well as six normal human ovarian surface epithelial (HOSE) cell lines using Taqman-based real-time PCR assays. Her-2/neu overexpression was assessed in ovarian carcinomas (n = 109 cases) by immunohistochemistry analysis.

Results

Expression of four miRNAs (miR-30c, miR-30d, miR-30e-3p, miR-370) was significantly different between carcinomas and benign ovarian tissues as well as between carcinoma and borderline tissues. An additional three miRNAs (miR-181d, miR-30a-3p, miR-532-5p) were significantly different between borderline and carcinoma tissues. Expression of miR-532-5p was significantly lower in borderline than in benign tissues. Among ovarian carcinomas, expression of four miRNAs (miR-30a-3p, miR-30c, miR-30d, miR-30e-3p) was lowest in mucinous and highest in clear cell samples. Expression of miR-30a-3p was higher in well-differentiated compared to poorly differentiated tumors (P = 0.02), and expression of miR-370 was higher in stage I/II compared to stage III/IV samples (P = 0.03). In multivariate analyses, higher expression of miR-181d, miR-30c, miR-30d, and miR-30e-3p was associated with significantly better disease-free or overall survival. Finally, lower expression of miR-30c, miR-30d, miR-30e-3p and miR-532-5p was significantly associated with overexpression of Her-2/neu.

Conclusions

Aberrant expression of miRNAs is common in ovarian tumor suggesting involvement of miRNA in ovarian tumorigenesis. They are associated with histology, clinical stage, survival and oncogene expression in ovarian carcinoma.

Prognostic biomarkers in ovarian cancer

Epithelial ovarian cancer (EOC) remains the most lethal gynecological malignancy despite several decades of progress in diagnosis and treatment. Taking advantage of the robust development of discovery and utility of prognostic biomarkers, clinicians and researchers are developing personalized and targeted treatment strategies. This review encompasses recently discovered biomarkers of ovarian cancer, the utility of published prognostic biomarkers for EOC (especially biomarkers related to angiogenesis and key signaling pathways), and their integration into clinical practice.

Review of miR-200b and cancer chemosensitivity

Chemoresistance remains a major obstacle to successful cancer treatment and leads to poor prognosis of the patients, yet the underlying mechanisms have not been fully understood. MicroRNAs (miRNAs) are non-coding small RNAs of 19-22 nucleotides which could negatively regulate gene expressions mainly through 3'-untranslated region (3'UTR) binding of target mRNAs. MiR-200 family (miR-200a, miR-200b, miR-200c, miR-141, and miR-429) is a cluster of miRNAs highly correlated with epithelial-mesenchymal transition (EMT), wherein miR-200b is identified as a critical regulator of tumor invasion, metastasis, and chemosensitivity. Recent advances of miR-200b dysregulation in tumor chemoresistance were summarized. Possible mechanisms and reversion strategies were also addressed.

Characterization of human gastric carcinoma-related methylation of 9 miR CpG islands and repression of their expressions in vitro and in vivo

Background

Many miR genes are located within or around CpG islands. It is unclear whether methylation of these CpG islands represses miR transcription regularly. The aims of this study are to characterize gastric carcinoma (GC)-related methylation of miR CpG islands and its relationship with miRNA expression.

Methods

Methylation status of 9 representative miR CpG islands in a panel of cell lines and human gastric samples (including 13 normal biopsies, 38 gastritis biopsies, 112 pairs of GCs and their surgical margin samples) was analyzed by bisulfite-DHPLC and sequencing. Mature miRNA levels were determined with quantitative RT-PCR. Relationships between miR methylation, transcription, GC development, and clinicopathological characteristics were statistically analyzed.

Results

Methylation frequency of 5 miR CpG islands (miR-9-1, miR-9-3, miR-137, miR-34b, and miR-210) gradually increased while the proportion of methylated miR-200b gradually decreased during gastric carcinogenesis (Ps < 0.01). More miR-9-1 methylation was detected in 62%-64% of the GC samples and 4% of the normal or gastritis samples (18/28 versus 2/48; Odds ratio, 41.4; P < 0.01). miR-210 methylation showed high correlation with H. pylori infection. miR-375, miR-203, and miR-193b methylation might be host adaptation to the development of GCs. Methylation of these miR CpG islands was consistently shown to significantly decrease the corresponding miRNA levels presented in human cell lines. The inverse relationship was also observed for miR-9-1, miR-9-3, miR-137, and miR-200b in gastric samples. Among 112 GC patients, miR-9-1 methylation was an independent favourable predictor of overall survival of GC patients in both univariate and multivariate analysis (P < 0.02).

Conclusions

In conclusion, alteration of methylation status of 6 of 9 tested miR CpG islands was characterized in gastric carcinogenesis. miR-210 methylation correlated with H. pylori infection. miR-9-1 methylation may be a GC-specific event. Methylation of miR CpG islands may significantly down-regulate their transcription regularly.

The quantitative analysis by stem-loop real-time PCR revealed the microRNA-34a, microRNA-155 and microRNA-200c overexpression in human colorectal cancer

The recently identified class of microRNAs (miRNAs) provided a new insight in cancer research. As the member of miRNAs family, miR-34a, miR-155 and miR-200c abnormalities have been found in various types of cancer. However, the relationship between these three miRNAs (miR-34a, miR-155 and miR-200c) and colorectal cancer is unclear. In this study, we applied stem-loop real-time PCR to quantitatively detect miR-34a, miR-155 and miR-200c expression in 109 pair-matched human colorectal cancers and the corresponding normal mucosa. MiR-34a (2.2-fold), miR-155 (2.3-fold) and miR-200c (3.1-fold) were all expressed at higher levels in colorectal cancer (P = 0.001, 0.005 and 0.001, respectively). In rectum, miR-34a and miR-200c were significantly upregulated (P = 0.006 and 0.007), while the miR-155 overexpression was not statistically significant (P = 0.083). In colon, the higher expression of three miRNAs was seen, however, without significant difference (P > 0.05). We also found that the miR-34a expression was higher in rectal cancer having more advanced TNM stage (III + IV, P = 0.03). Then miR-200c expression was positively correlated with and sera CEA level of rectal cancer patients (P = 0.04). In conclusion, our results thus suggest that the overexpression of miR-34a, miR-155 and miR-200c be associated with the development of colorectal cancer, meanwhile miR-34a may be involved in the development and progression of rectal cancer. The more deeply and larger scale research are required to prove the correlation.

Role of epigenomics in ovarian and endometrial cancers

Ovarian cancer is the most lethal gynecologic malignancy and while constituting only 3% of all female cancers, it causes 14,600 deaths in the USA annually. Endometrial cancer, the most diagnosed and second-most fatal gynecologic cancer, afflicts over 40,000 US women annually, causing an estimated 7780 deaths in 2009. In both advanced ovarian and endometrial carcinomas, the majority of initially therapy-responsive tumors eventually evolve to a fully drug-resistant phenotype. In addition to genetic mutations, epigenetic anomalies are frequent in both gynecologic malignancies, including aberrant DNA methylation, atypical histone modifications and dysregulated expression of distinct microRNAs, resulting in altered gene-expression patterns favoring cell survival. In this article, we summarize the most recent hypotheses regarding the role of epigenetics in ovarian and endometrial cancers, including a possible role in tumor 'stemness' and also evaluate the possible therapeutic benefits of reversal of these oncogenic chromatin aberrations.

Crosstalk between transcription factors and microRNAs in human protein interaction network

Background

Gene regulatory networks control the global gene expression and the dynamics of protein output in living cells. In multicellular organisms, transcription factors and microRNAs are the major families of gene regulators. Recent studies have suggested that these two kinds of regulators share similar regulatory logics and participate in cooperative activities in the gene regulatory network; however, their combinational regulatory effects and preferences on the protein interaction network remain unclear.

Methods

In this study, we constructed a global human gene regulatory network comprising both transcriptional and post-transcriptional regulatory relationships, and integrated the protein interactome into this network. We then screened the integrated network for four types of regulatory motifs: single-regulation, co-regulation, crosstalk, and independent, and investigated their topological properties in the protein interaction network.

Results

Among the four types of network motifs, the crosstalk was found to have the most enriched protein-protein interactions in their downstream regulatory targets. The topological properties of these motifs also revealed that they target crucial proteins in the protein interaction network and may serve important roles of biological functions.

Conclusions

Altogether, these results reveal the combinatorial regulatory patterns of transcription factors and microRNAs on the protein interactome, and provide further evidence to suggest the connection between gene regulatory network and protein interaction network.

MicroRNA dysregulation in cancer: diagnostics, monitoring and therapeutics. A comprehensive review

Early studies have shown how aberrantly expressed microRNAs are a hallmark of several diseases like cancer. MicroRNA expression profiling was shown to be associated with tumour development, progression and response to therapy, suggesting their possible use as diagnostic, prognostic and predictive biomarkers. Moreover, based on the increasing number of studies demonstrating that microRNAs can function as potential oncogenes or oncosuppressor genes, with the goal to improve disease response and increase cure rates, miRNA-based anticancer therapies have recently been exploited, either alone or in combination with current targeted therapies. The advantage of using microRNA approaches is based on its ability to concurrently target multiple effectors of pathways involved in cell differentiation, proliferation and survival. Here, we review our current knowledge about the involvement of microRNAs in cancer, and their potential as diagnostic, prognostic and therapeutic tools.

Potential applications of microRNAs in cancer diagnosis, prognosis, and treatment

Early studies have established that microRNAs (miRNAs) are widely deregulated in cancer and play a critical role in cancer pathogenesis. Recent research efforts are directed now towards translating these basic discoveries into novel tests or treatments that could improve the diagnosis and outcome of cancer patients. In this review, we will summarize the potential applications of miRNAs for cancer diagnosis, prognosis, and treatment. In addition, we will discuss current pitfalls and future directions.

Roles and mechanisms of microRNAs in pancreatic cancer

Pancreatic cancer (PC) is an aggressive malignancy with poor survival. The discovery of microRNAs (miRNAs) has provided a new opportunity to study the disease. Thus far, altered expression of miRNAs has been reported in a wide range of malignancies, including PC, and some miRNAs are associated with PC cell proliferation, invasion, chemoresistance, and patient survival. This review summarizes recent advances with respect to the roles and mechanisms of miRNAs in PC and discusses potential clinical applications.

MicroRNA-200c represses migration and invasion of breast cancer cells by targeting actin-regulatory proteins FHOD1 and PPM1F

MicroRNA-200c (miR-200c) has been shown to suppress epithelial-mesenchymal transition (EMT), which is attributed mainly to targeting of ZEB1/ZEB2, repressors of the cell-cell contact protein E-cadherin. Here we demonstrated that modulation of miR-200c in breast cancer cells regulates cell migration, cell elongation, and transforming growth factor β (TGF-β)-induced stress fiber formation by impacting the reorganization of cytoskeleton that is independent of the ZEB/E-cadherin axis. We identified FHOD1 and PPM1F, direct regulators of the actin cytoskeleton, as novel targets of miR-200c. Remarkably, expression levels of FHOD1 and PPM1F were inversely correlated with the level of miR-200c in breast cancer cell lines, breast cancer patient samples, and 58 cancer cell lines of various origins. Furthermore, individual knockdown/overexpression of these target genes phenocopied the effects of miR-200c overexpression/inhibition on cell elongation, stress fiber formation, migration, and invasion. Mechanistically, targeting of FHOD1 by miR-200c resulted in decreased expression and transcriptional activity of serum response factor (SRF), mediated by interference with the translocation of the SRF coactivator mycocardin-related transcription factor A (MRTF-A). This finally led to downregulation of the expression and phosphorylation of the SRF target myosin light chain 2 (MLC2) gene, required for stress fiber formation and contractility. Thus, miR-200c impacts on metastasis by regulating several EMT-related processes, including a novel mechanism involving the direct targeting of actin-regulatory proteins.

Micro-RNAs as diagnostic or prognostic markers in human epithelial malignancies

Micro-RNAs (miRs) are important regulators of mRNA and protein expression; the ability of miR expression profilings to distinguish different cancer types and classify their sub-types has been well-described. They also represent a novel biological entity with potential value as tumour biomarkers, which can improve diagnosis, prognosis, and monitoring of treatment response for human cancers. This endeavour has been greatly facilitated by the stability of miRs in formalin-fixed paraffin-embedded (FFPE) tissues, and their detection in circulation. This review will summarize some of the key dysregulated miRs described to date in human epithelial malignancies, and their potential value as molecular bio-markers in FFPE tissues and blood samples. There remain many challenges in this domain, however, with the evolution of different platforms, the complexities of normalizing miR profiling data, and the importance of evaluating sufficiently-powered training and validation cohorts. Nonetheless, well-conducted miR profiling studies should contribute important insights into the molecular aberrations driving human cancer development and progression.

Micro-RNAs as diagnostic or prognostic markers in human epithelial malignancies

Micro-RNAs (miRs) are important regulators of mRNA and protein expression; the ability of miR expression profilings to distinguish different cancer types and classify their sub-types has been well-described. They also represent a novel biological entity with potential value as tumour biomarkers, which can improve diagnosis, prognosis, and monitoring of treatment response for human cancers. This endeavour has been greatly facilitated by the stability of miRs in formalin-fixed paraffin-embedded (FFPE) tissues, and their detection in circulation. This review will summarize some of the key dysregulated miRs described to date in human epithelial malignancies, and their potential value as molecular bio-markers in FFPE tissues and blood samples. There remain many challenges in this domain, however, with the evolution of different platforms, the complexities of normalizing miR profiling data, and the importance of evaluating sufficiently-powered training and validation cohorts. Nonetheless, well-conducted miR profiling studies should contribute important insights into the molecular aberrations driving human cancer development and progression.

miRNA profiling along tumour progression in ovarian carcinoma

MicroRNAs (miRNAs) are small non-coding RNAs that exert a regulatory effect post-transcriptionally by binding target mRNAs and inhibiting gene translation. miRNA expression is deregulated in cancer. The aim of this study was to characterize the differences in miRNA expression pattern and the miRNA-regulating machinery between ovarian carcinoma (OC) cells in primary tumours versus effusions. Using miRNA array platforms, we analysed a set of 21 tumours (13 effusions, 8 primary carcinomas) and identified three sets of miRNAs, one that is highly expressed in both primary carcinomas and effusions, one overexpressed in primary carcinomas and one overexpressed in effusions. Levels of selected miRNAs were analysed using quantitative PCR in an independent set of 45 additional tumours (30 effusions, 15 primary carcinomas). Reduced miR-145 and miR-214 and elevated let-7f, miR-182, miR-210, miR-200c, miR-222 and miR-23a levels were found in effusions in both sets. In silico target prediction programs identified potential target genes for some of the differentially expressed miRNAs. Expression of zinc finger E-box binding homeobox (ZEB)1 and c-Myc, targets of miR-200c, as well as of p21 protein (Cdc42/Rac)-activated kinase (PAK)1 and phosphatase and tensin homologue deleted on chromosome 10 (PTEN), predicted targets of miR-222, were analysed. Inverse correlations between expression levels of the indicated miRNAs and of the predicted target genes were found. In addition, higher expression of the miRNA-processing molecules Ago1, Ago2 and Dicer was observed in effusions compared to primary carcinomas. In conclusion, our data are the first to document different miRNA expression and regulation profiles in primary and metastatic OC, suggesting a role for these molecules in tumour progression.

New role of microRNA: carcinogenesis and clinical application in cancer

MicroRNA (miRNA) is a cluster of small non-encoding RNA molecules of 21-23 nucleotides in length, which controls the expression of target gene at the post-transcriptional level. Recent researches have indicated that miRNA plays an essential role in carcinogenesis, such as affecting the cell growth, differentiation, apoptosis, and cell cycle. Nowadays, multiple promising roles of miRNA involved in carcinogenesis are emerging, and it is shown that miRNA closely relates to the process of epithelial-mesenchymal transition (EMT), the regulation of cancer stem cells (CSCs), the development of tumor invasion and migration. miRNA also acts as a biomarker stably expressed in serum and provides new target for molecular target therapy of various cancers. The aim of this review is to illustrate the new role of miRNA in carcinogenesis and highlight the new prospects of miRNA in cancer clinical application, such as in serological diagnosis and molecular-targeted therapeutics.

miR-200bc/429 cluster modulates multidrug resistance of human cancer cell lines by targeting BCL2 and XIAP

PURPOSE

MicroRNAs (miRNAs) are short non-coding RNA molecules, which post-transcriptionally regulate genes expression and play crucial roles in diverse biological processes. Recent studies have shown that dysregulation of miRNAs might modulate the resistance of cancer cells to anti-cancer drugs, yet the modulation mechanism is not fully understood. We aimed to investigate the possible role of miRNAs in the development of multidrug resistance (MDR) in human gastric and lung cancer cell lines.

METHODS

miRNA Quantitative real-time PCR was used to detect the different miRNA expression levels between drug resistant and parental cancer cells. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to test the drug-resistant phenotype changes in cancer cells via over or downregulation of miRNAs. Dual-luciferase activity assay was used to verify the target genes of miRNAs. Western blot analysis and apoptosis assay were used to elucidate the mechanism of miRNAs on modulating drug resistance in cancer cells.

RESULTS

miR-200bc/429 cluster was downregulated, while BCL2 and XIAP were upregulated in both MDR SGC7901/VCR (vincristine) and A549/CDDP (cisplatin) cells, compared with the parental SGC7901 and A549 cells, respectively. Overexpression of miR-200bc/429 cluster sensitized SGC7901/VCR and A549/CDDP cells to anti-cancer drugs, respectively. Both BCL2 and XIAP 3'-UTR reporters constructed in MDR cells suggested that BCL2 and XIAP were the common target genes of the miR-200bc/429 cluster. Enforced miR-200bc/429 cluster expression reduced BCL2 and XIAP protein level and sensitized both MDR cells to VCR-induced and CDDP-induced apoptosis, respectively.

CONCLUSIONS

Our findings first suggest that miR-200bc/429 cluster could play a role in the development of MDR in both gastric and lung cancer cell lines, at least in part by modulation of apoptosis via targeting BCL2 and XIAP.

MicroRNAs as a potential prognostic factor in gastric cancer

AIM: To compare the microRNA (miR) profiles in the primary tumor of patients with recurrent and non-recurrent gastric cancer.

METHODS: The study group included 45 patients who underwent curative gastrectomies from 1995 to 2005 without adjuvant or neoadjuvant therapy and for whom adequate tumor content was available. Total RNA was extracted from formalin-fixed paraffin-embedded tumor samples, preserving the small RNA fraction. Initial profiling using miR microarrays was performed to identify potential biomarkers of recurrence after resection. The expression of the differential miRs was later verified by quantitative real-time polymerase chain reaction (qRT-PCR). Findings were compared between patients who had a recurrence within 36 mo of surgery (bad-prognosis group, n = 14, 31%) and those who did not (good-prognosis group, n = 31, 69%).

RESULTS: Three miRs, miR-451, miR-199a-3p and miR-195 were found to be differentially expressed in tumors from patients with good prognosis vs patients with bad prognosis (P < 0.0002, 0.0027 and 0.0046 respectively). High expression of each miR was associated with poorer prognosis for both recurrence and survival. Using miR-451, the positive predictive value for non-recurrence was 100% (13/13). The expression of the differential miRs was verified by qRT-PCR, showing high correlation to the microarray data and similar separation into prognosis groups.

CONCLUSION: This study identified three miRs, miR-451, miR-199a-3p and miR-195 to be predictive of recurrence of gastric cancer. Of these, miR-451 had the strongest prognostic impact.

The microRNA-200 family is upregulated in endometrial carcinoma

Background

MicroRNAs (miRNAs, miRs) are small non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. MicroRNAs are dysregulated in cancer and may play essential roles in tumorigenesis. Additionally, miRNAs have been shown to have prognostic and diagnostic value in certain types of cancer. The objective of this study was to identify dysregulated miRNAs in endometrioid endometrial adenocarcinoma (EEC) and the precursor lesion, complex atypical hyperplasia (CAH).

Methodology

We compared the expression profiles of 723 human miRNAs from 14 cases of EEC, 10 cases of CAH, and 10 normal proliferative endometria controls using Agilent Human miRNA arrays following RNA extraction from formalin-fixed paraffin-embedded (FFPE) tissues. The expression of 4 dysregulated miRNAs was validated using real time reverse transcription-PCR.

Results

Forty-three miRNAs were dysregulated in EEC and CAH compared to normal controls (p<0.05). The entire miR-200 family (miR-200a/b/c, miR-141, and miR-429) was up-regulated in cases of EEC.

Conclusions

This information contributes to the candidate miRNA expression profile that has been generated for EEC and shows that certain miRNAs are dysregulated in the precursor lesion, CAH. These miRNAs in particular may play important roles in tumorigenesis. Examination of miRNAs that are consistently dysregulated in various studies of EEC, like the miR-200 family, will aid in the understanding of the role that miRNAs play in tumorigenesis in this tumour type.

Regulation of ovarian cancer progression by microRNA-187 through targeting Disabled homolog-2

MicroRNAs (miRNAs) play important roles in tumorigenesis by regulating oncogenes and tumor-suppressor genes. In this study, miR-187 and miR-200a were found to be expressed at higher levels in ovarian cancers than in benign tumors. In patients with ovarian cancer, however, higher levels of miR-187 and miR-200a expression were paradoxically associated with better OS and recurrence-free survival. Further, multivariate analysis showed that miR-187 served as an independent prognostic factor for patients with ovarian cancer (n=176). Computational prediction and microarray results indicated that miR-187 directly targeted Disabled homolog-2 (Dab2), and luciferase reporter assays confirmed that the target site of miR-187 was located at the 3'-UTR of the Dab2 gene. Generally considered as a tumor-suppressor gene, Dab2 may actually promote tumor progression in advanced cancers through epithelial-to-mesenchymal transition (EMT). Ectopic expression of miR-187 in cancer cells promoted cell proliferation, but continued overexpression of miR-187 suppressed Dab2 and inhibited migration. Suppression of miR-187 upregulated Dab2, which, by inhibiting E-cadherin levels while stimulating vimentin and phospho-FAK levels, promoted EMT. Reduced ovarian cancer Dab2 histoscores correlated with high miR-187 levels and improved outcomes of patients. Collectively, these results demonstrate distinct dual roles of Dab2 in cell proliferation and tumor progression. In the initial steps of tumorigenesis, upregulated miR-187 suppresses Dab2, promoting cell proliferation. During the later stages, however, continued increased levels of miR-187 inhibits the Dab2-dependent EMT that is associated with tumor invasiveness, which is presumed to be the reason why cancers with high miR-187 levels were associated with better survivals.

MicroRNAs in Development and Disease

MicroRNAs (miRNAs) are a class of posttranscriptional regulators that have recently introduced an additional level of intricacy to our understanding of gene regulation. There are currently over 10,000 miRNAs that have been identified in a range of species including metazoa, mycetozoa, viridiplantae, and viruses, of which 940, to date, are found in humans. It is estimated that more than 60% of human protein-coding genes harbor miRNA target sites in their 3′ untranslated region and, thus, are potentially regulated by these molecules in health and disease. This review will first briefly describe the discovery, structure, and mode of function of miRNAs in mammalian cells, before elaborating on their roles and significance during development and pathogenesis in the various mammalian organs, while attempting to reconcile their functions with our existing knowledge of their targets. Finally, we will summarize some of the advances made in utilizing miRNAs in therapeutics.

miR-429 modulates the expression of c-myc in human gastric carcinoma cells

AIM

MicroRNAs (miRNAs) are a recently discovered class of small non-coding RNAs that regulate gene expression and may contribute to the development and progression of many cancers. In this study, our goal was to investigate the regulation of miR-429 in gastric cancer and explored the mechanism/s by which it influenced pathogenesis of gastric cancer.

METHODS

We used real-time reverse transcriptase-polymerase chain reaction to quantify the expression level of miR-429 in 52 gastric cancer tissues and their paracancerous tissues. Bioinformatics was used to predict downstream target genes of miR-429. SGC-7901 gastric cancer cells were transfected with miR-429 mimics and endogenous c-myc expression was detected by western blots. We performed functional assays using the 3'UTR of the c-myc gene as a miR-429 target in a luciferase reporter assay system.

RESULTS

We showed that miR-429 was downregulated in human gastric carcinoma tissue and in SGC-7901 cells. Cell viability, proliferation and attachment were inhibited in miR-429-transfected cells. miR-429 significantly downregulated endogenous c-myc expression in SGC-7901 cells. Action of miR/429 on c-myc 3'UTR was confirmed. The levels of miR-429 in tumour tissue of patients with lymph node metastasis were significantly lower than in those without lymph node metastasis.

CONCLUSIONS

Our results suggested that miR-429 played a role in the pathogenesis of gastric carcinoma and may function as a recessive cancer gene. c-myc is an important miR-429 target gene.

MicroRNA-200a inhibits CD133/1+ ovarian cancer stem cells migration and invasion by targeting E-cadherin repressor ZEB2

OBJECTIVES

MicroRNA-200a (miR-200a) has been reported to be a prognostic marker and to play an important role in ovarian cancer progression. The aim of the study was to elucidate the mechanism of miR-200a involved in migration and invasion in CD133/1+ ovarian cancer stem cells (OCSCs).

METHODS

The expression of miR-200a between CD133/1+ and CD133/1- cells was performed using real-time PCR, and wound healing assay and matrigel invasion assay were used to detect migration and invasion of CD133/1+ cells, respectively, target gene regulated by miR-200a was detected using Dual Luciferase Reporter system, The expression levels of target gene were confirmed using real-time PCR and western blot.

RESULTS

miR-200a was downregulated in CD133/1+ cells compared with CD133/1- cells, and overexpression of miR-200a significantly reduced CD133/1+ cells migration and invasion compare with negative control (NC) (p<0.05). The 3'-UTR of ZEB2 mRNA, a transcriptional repressor of E-cadherin, was found to be regulated directly by miR-200a. In addition, when miR-200a was overexpressed in CD133/1+ cells, the mRNA and protein levels of ZEB2 were both suppressed, which resulted in an increase in the E-cadherin expression level, suggesting that ZEB2 was a functionally important target of miR-200a in CD133/1+ cells.

CONCLUSIONS

Our results suggest that loss of expression of miR-200a may play a critical role in the repression of E-cadherin by ZEB2, thereby enhancing migration and invasion in CD133/1+ cells.

MicroRNAs as therapeutic targets in cancer

Cancer remains a worldwide epidemic. An improved understanding of the underlying molecular mechanisms and development of effective targeted therapies are still required for many deadly cancers. The discovery of microRNAs (miRNAs or miRs) nearly 20 years ago introduced a new layer of complexity to gene regulation, but it also afforded us the opportunity to further our understanding of the molecular pathogenesis of cancers. Dysregulation of miRNAs is fundamental to the pathogenesis of many cancers based on their involvement in basic cellular functions. In addition, these previously underrecognized, noncoding RNAs have the capacity to target tens to hundreds of genes simultaneously. Thus, they are attractive candidates as prognostic biomarkers and therapeutic targets in cancer. However, several challenges remain in translating our current understanding of miRNAs to clinical therapies. Herein, we provide a review of the current knowledge of miRNAs in both solid and hematological malignancies with a focus on their potential application as therapeutic targets in cancer.

MicroRNA-200b regulates vascular endothelial growth factor-mediated alterations in diabetic retinopathy

OBJECTIVE

Diabetic retinopathy (DR) is a leading cause of blindness. Increased vascular endothelial growth factor (VEGF), promoting angiogenesis and increased permeability, is a key mechanistic abnormality in DR. We investigated microRNA (miRNA) alterations in DR with specific focus on miR-200b, and its downstream target, VEGF.

RESEARCH DESIGN AND METHODS

miRNA expression profiling microarray was used to examine the retinas of streptozotocin-induced diabetic rats. Expressions of specific miRNAs were verified with PCR in the rat retina and in glucose-exposed endothelial cells. A target search, based on sequence complementarities, identified specific targets. We analyzed mRNA levels and protein expression in endothelial cells from large vessels and retinal capillaries and in the rat retina, with or without injection of miR-200b mimic or antagomir. Localization of miR-200b and its functional analysis in the rat and human retinas were performed.

RESULTS

Alteration of several miRNAs, including downregulation of miR-200b, were observed in the retina in diabetes. Such downregulation was validated in the retina of diabetic rats and in endothelial cells incubated in glucose. In parallel, VEGF (target of miR-200b) mRNA and protein were elevated. In the retina, miR-200b was localized in neuronal, glial, and vascular elements. Transfection of endothelial cells and intravitreal injection of miR-200b mimic prevented diabetes-induced increased VEGF mRNA and protein. Also prevented were glucose-induced increased permeability and angiogenesis. Furthermore, transfection of miR-200b antagonists (antagomir) led to increased VEGF production. Similar alterations were seen in the human retina.

CONCLUSIONS

These studies show a novel mechanism involving miR-200b in DR. Identification of such mechanisms may lead to the development of novel miRNA-based therapy.

MicroRNA profiles of healthy basal and luminal mammary epithelial cells are distinct and reflected in different breast cancer subtypes

In order to determine the microRNA expression pattern in normal basal and luminal breast epithelium and to analyze the relationship of this expression pattern to different breast cancer subtypes, laser-microdissected luminal and basal cells isolated from plastic surgery tissue samples were used for comprehensive expression profiling, measuring 664 microRNAs by low-density TaqMan arrays. In a test (n = 5) and validation set (n = 9) 10 differentially expressed microRNAs were identified by TaqMan RT-qPCR. These microRNAs were studied in laser-microdissected cells of luminal A (n = 5), luminal B (n = 5), basal-like subtypes of breast cancer (n = 10), and malignant myoepithelioma of the breast (n = 10). From 116 microRNAs unequivocally expressed in normal breast epithelial cells, we identified 8 basal microRNAs (let7c, miR-125b, miR-126, miR-127-3p, miR-143, miR-145, miR-146b-5p, and miR-199a-3p), preferentially expressed in normal basal cells, exceeding luminal cells by a factor from 4 to 1000. All of these microRNAs were also found to be significantly elevated in malignant myoepithelioma but not in basal-type of breast cancer. Two members of the miR-200 family (miR-200c and miR-429) were predominantly luminal. Both microRNAs were expressed in the luminal and basal type of breast cancer in contrast to malignant myoepithelioma, which revealed significantly lower levels potentially contributing to its mesenchymal phenotype. In conclusion, normal luminal and basal mammary epithelial cells exhibit a different microRNA expression profile. Malignant myoepithelioma seems to exhibit a basal pattern of microRNA expression, whereas the so-called basal-like breast cancer is clearly different and reveals a luminal type pattern.

A microRNA survival signature (MiSS) for advanced ovarian cancer

OBJECTIVES

MicroRNAs (miRNAs) are a class of small non-coding RNAs that negatively regulate gene expression primarily through post-transcriptional modification. We tested the hypothesis that miRNA expression is associated with overall survival in advanced ovarian cancer.

METHODS

Cases included newly diagnosed patients with stage III or IV serous ovarian cancer. RNA from a training set of 62 cases was hybridized to an miRNA microarray containing 470 mature human transcripts. Cox Regression was performed to identify miRNAs associated with overall survival. External validation was performed using quantitative RT-PCR miRNA assays in an independent test set of 123 samples. MiRNA targets and associated biologic pathways were predicted in silico.

RESULTS

Of all patients, 80% had high-grade, stage IIIC tumors and 64% underwent optimal cytoreduction. The median survival for the entire cohort was 49±4 months. The training set identified 3 miRNAs associated with survival--miR-337, miR-410, and miR-645. An miRNA signature containing miR-410 and miR-645 was most strongly associated with overall survival in the training set (HR=2.96, 95% CI: 1.51-5.78). This miRNA survival signature (MiSS) was validated in the test set (HR=1.71, 95% CI: 1.05-2.78). The MiSS was independent of FIGO stage and surgical debulking.

CONCLUSIONS

The data suggest that an MiSS that contains miR-410 and miR-645 is negatively associated with overall survival in advanced serous ovarian cancer. This signature, when further validated, may be useful in individualizing care for the ovarian cancer patient. Pathway analyses identify biologically plausible mechanisms.