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Introduction:MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level. Recently, different experimental approaches, such as RNA Sequencing, crosslinking immunoprecipitation (CLIP) methods and its variations, together with computational approaches have been developed to elucidate the miRNA-mRNA targetome. Areas covered:This report focuses on comparing the different experimental and computational approaches, describing their advantages and disadvantages and providing several examples of preclinical (in vitroandin vivo) and clinical studies that have identified miRNA target genes in various tumour types, including breast, ovary, colorectal and pancreas. Expert commentary:The combination of CLIP methods with bioinformatic analyses is essential to better predict miRNA-mRNA interactions and associate their specific pathways within the extensive regulatory network. Nevertheless, further studies are needed to overcome the difficulties these methods have, in order to find a gold standard method that identifies, without any bias, the regulatory association between miRNAs and their target mRNAs. [ABSTRACT FROM PUBLISHER]

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease characterized by a dense desmoplastic reaction surrounding malignant epithelial cells. Interaction between the epithelial and stromal compartments is suggested to enhance its aggressive nature. Indeed, therapies targeting the stroma, as well as the tumor cells, may improve survival outcomes for patients. The evaluated study by Moffittet al. used bioinformatic techniques to separate gene expression patterns of normal tissues from PDAC and stroma in a large cohort of samples. The researchers identified two different subtypes of PDAC (‘classical’ and ‘basal-like’) and surrounding stroma (‘normal’ and ‘activated’). The basal-like subtype was associated with worse prognosis and a trend towards better response to adjuvant therapy. Hopefully, the molecular stratification of PDAC will potentially allow more personalized treatment strategies and guide clinical decision making. [ABSTRACT FROM PUBLISHER]

Genome-wide single-cell sequencing investigations have the potential to classify individual cells within a tumor mass. In recent years, various single-cell DNA and RNA quantification techniques have facilitated significant advances in our ability to classify subpopulations of cells within a heterogeneous population. These approaches provide the possibility of unraveling the complex variability in genetic, epigenetic and transcriptional interactions that occur within identical cells in a tumor. This should enhance our knowledge of the underlying biological phenotypes and could have a huge impact in designing more precise anticancer treatments in order to improve outcomes and avoid tumor resistance. In addition, single-cell sequencing analysis has the potential to allow the development of better diagnostic and prognostic biomarkers, and thus aid the delivery of more personalized targeted cancer therapy. Nevertheless, further research is still required to overcome technical, biological and computational problems before clinical application. [ABSTRACT FROM PUBLISHER]

Evaluation of:Singhi AD, Nikiforova MN, Fasanella KE,et al. PreoperativeGNASandKRAStesting in the diagnosis of pancreatic mucinous cysts.Clin. Cancer Res.20(16), 4381-9 (2014). Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas have a risk of malignant transformation following an adenoma–carcinoma sequence. Surgical resection is often required, especially for main pancreatic duct IPMNs (MD-IPMNs). There is an urgent need for novel biomarkers to reliably differentiate IPMNs from more benign pancreatic cysts and therefore avoid unnecessary surgery. DNA sequencing has demonstrated that guanine nucleotide binding protein alpha stimulating (GNAS) activity polypeptide 1 mutations play a driving role in IPMN development.GNASmutations have been shown to be highly specific for IPMNs, whereas oncogenicKRASmutations have been associated with mucinous differentiation. The evaluated article by Singhiet al.helps to define the role of these mutations as biomarkers in preoperative endoscopic ultrasound fine-needle aspiration samples for detecting IPMNs. They found that the presence of aGNASand/or aKRASmutation was highly specific and sensitive for IPMNs. [ABSTRACT FROM PUBLISHER]

Evaluation of: Ma MZ, Kong X, Weng MZ et al. Candidate microRNA biomarkers of pancreatic ductal adenocarcinoma: meta-analysis, experimental validation and clinical significance. J. Exp. Clin. Cancer Res. 32(1), 71 (2013). Due to its aggressive and late presentation, there is an urgent need for novel and reliable biomarkers for the diagnosis and prognostication of pancreatic ductal adenocarcinoma (PDAC). MiRNAs have been extensively profiled in PDAC tissues, biopsies, blood samples and other biofluids and their expression levels compared to normal and chronic pancreatitis (CP) specimens in order to identify the most relevant candidates. Consolidation of these activities has not been attempted until now. The evaluated meta-review by Ma et al. helps to define the use of miRNAs as biomarkers for detecting this tumor-type and predicting survival outcomes in PDAC. Based on frequency and consistency between microarray studies, they identified a miRNA meta-signature for recognising PDAC: upregulation of miR-21, 23a, 31, 100, 143, 155, and 221; with downregulation of miR-148a, 217 and 375. Furthermore, they validated high miR-21, high miR-31 and low miR-375 tumoural expression as independently prognostic for poor overall-survival (OS; n = 70). [ABSTRACT FROM AUTHOR]

Evaluation of: Bidard FC, Huguet F, Louvet C et al. Circulating tumor cells in locally advanced pancreatic adenocarcinoma: the ancillary CirCe 07 study to the LAP 07 trial. Ann. Oncol. 24(8), 2057-2061 (2013). Circulating tumor cells (CTCs) may be shed from the primary tumor and lead to metastatic disease. This evaluated article reports on CTCs in locally advanced pancreatic cancer (LAPC). By assessing CTCs from peripheral blood prior to any treatment and after 2 months of chemotherapy, 11% of patients had detectable CTCs. These patients had a poorer overall survival. With such low numbers of CTCs detected in LAPC patients, it is unclear whether CTCs can actually contribute toward tumor invasiveness and spread in such an aggressive cancer. Although this is a well-designed study, the small number of patients with detectable CTCs means that the statistical power is not great enough to make firm conclusions. Therefore, this expensive assay needs further investigation before being used a prognostic marker in patients with LAPC. [ABSTRACT FROM AUTHOR]

The capacity of noncoding RNA to regulate gene expression in health and disease is epitomized by the microRNAs, small ~22-nucleotide RNAs that target mRNAs to repress their translation into protein. Recently a previously unrecognized gene regulatory layer has emerged, characterized by the ability of a wide range of RNA transcripts to vie for microRNA binding and alleviate the repressive effect of microRNAs on their mRNA targets. Termed competing endogenous RNAs (ceRNAs), these participate in a microRNA-dependent cross talk, producing robust networks that when perturbed may lead to cancer. To date, the tumor suppressor PTEN has been most extensively validated as competing with a variety of ceRNAs in different cancers: reducing these ceRNAs appears to reduce PTEN levels, tipping cells toward cancer progression. In this review we look at ceRNA networks in cancer, their characteristics, and constituent parts, focusing on the insights that can be gained from the studies conducted on PTEN. We also explore the conditions that facilitate ceRNA cross talk, proposing that the disruption of these conditions may represent a general phenomenon in carcinogenesis. [ABSTRACT FROM AUTHOR]

The cytoskeleton is a dynamic three dimensional structure contained within the cytoplasm of a cell, and is important in cell shape and movement, and in metastatic progression during carcinogenesis. Members of the Rho family of small GTPases, RHO, RAC and cell cycle division 42 (Cdc42) proteins regulate cytoskeletal dynamics, through the control of a panel of genes. We have recently shown that the microRNA (miRNA) miR-23b represents a central effector of cytoskeletal remodelling. It increases cell-cell interactions, modulates focal adhesion and reduces cell motility and invasion by directly regulating several genes involved in these processes. [ABSTRACT FROM AUTHOR]

Patients with pancreatic ductal adenocarcinoma (PDAC) have a bleak outlook, primarily because tumors are detected late and are often too advanced for surgical resection. In addition, these lesions are incredibly resistant to anticancer therapies. The majority of PDAC patients have impaired tumor immunity, contributing to disease development and progression, although the mechanisms remain poorly understood. miRNAs are important negative gene regulators that have critical roles in human tumorigenesis. Blood-based miRNAs have been investigated as biomarkers for various cancers, in the hope that these will outperform current serum tumor markers. The evaluated study examined the miRNA profiles in peripheral blood mononuclear cells from PDAC patients. The theory is that circulating blood cells monitor the patients' physiological state and respond by altering their transcriptome and that this can then be used to detect disease. In this article, we have examined the evidence for using circulating miRNAs to diagnose/prognose PDAC. [ABSTRACT FROM AUTHOR]

Pancreatic cysts are now being detected more frequently owing to increased recognition and the liberal use of cross-sectional imaging. There is a spectrum of pancreatic cystic lesions ranging from the completely benign inflammatory to the highly malignant. Pancreatic cystic tumors, especially those with a mucinous epithelial lining such as the intraductal papillary mucinous neoplasms (IPMNs), have the potential to become malignant. The evaluated paper provides further evidence for miRNAs as diagnostic biomarkers for detecting dysplastic and malignant change in IPMNs, which may be useful for future clinical decision making. IPMNs of varying degrees of dysplasia, as well as IPMN with carcinoma, pancreatic ductal adenocarcinoma and normal pancreas samples were examined by microarray. Upregulation of miR-21, miR-155 and miR-708 was found to occur during IPMN malignant transformation. Here, the authors evaluate the published miRNA profiles of premalignant pancreatic lesions in order to consolidate these data. [ABSTRACT FROM AUTHOR]

Several studies have implicated miRNAs in the initiation and progression of human cancers. Examining the biogenesis pathways that generate these important regulatory molecules has revealed new mechanisms for tumor development. Altered expression of the endoribonuclease Dicer in many tumors has given new hope to unraveling the complex relationship between miRNA processing and cancer. This may provide further insight into mechanisms for targeting multiple genes that are critical for the malignant phenotype of several cancers. The evaluated article demonstrates that Dicer is transcriptionally regulated by Sox4 and reduced levels of this transcription factor consequently leads to a reduction in expression, and therefore deregulation of cancer-related miRNAs in melanoma. Reduced Dicer expression in malignant melanoma is an independent predictor of poor survival. In this review, we assess the prognostic significance of Dicer expression in different tumor types. [ABSTRACT FROM AUTHOR]

Worldwide, colorectal cancer (CRC) is one of the most common forms of malignancy and is increasing in incidence in many regions. At diagnosis, approximately 40% of patients with CRC are anemic, a figure that increases over the course of a patient's treatment due to many factors, including ongoing hemorrhage. Preoperative anemia is therefore associated with increased allogenic red blood cell transfusion (ARBT) rates. In the context of CRC, perioperative ARBT has been linked with adverse postoperative outcomes, including higher morbidity, mortality and cancer recurrence rates. Therefore, strategies to potentially reduce the need for ARBT have been the focus of several recent studies. We critically evaluate a recent paper that explores intravenous iron III sucrose as a treatment option for the management of postoperative anemia in CRC patients. This study is a retrospective, observational case-controlled study that was designed to evaluate whether the use of postoperative intravenous iron reduces the incidence of ARBT following CRC resection. [ABSTRACT FROM AUTHOR]

The tumor-suppressor miRNA 126 (miR-126) is downregulated in many tumors and has recently been placed at the heart of complex metastatic pathways. Hamada and colleagues have identified miR-126 as being downregulated in pancreatic ductal adenocarcinoma (PDAC) patient samples and cell lines. The protein ADAM9 has been implicated in the progression of various solid tumors including PDAC. ADAM9 is overexpressed in PDAC and also a direct target of miR-126. The miR-126/ADAM9 axis was subsequently established to control migration and invasion in PDAC, as well as reversal of epithelial-to-mesenchymal transition. miR-126 is also known to target other crucial oncogenes in PDAC such as KRAS and CRK. Replacing miR-126 in PDAC patients may be a novel strategy for preventing progression and metastasis. [ABSTRACT FROM AUTHOR]

Retinoblastoma protein (RB) is one of the most important tumor suppressors and functions in multiple biological pathways that are deregulated during tumor initiation and progression. Epithelial-to-mesenchymal transition (EMT) is a reversible embryonic process by which epithelial cells lose cell-cell contact and polarity, and its aberrant activation can trigger tumor progression and metastasis. Previously, it has been shown that depletion of RB initiates EMT by downregulating the adhesion molecule E-cadherin. The evaluated article suggests that RB inactivation contributes to loss of cell cycle control and also leads to downregulation of the miR-200 family, thereby causing upregulation of ZEB expression and consequently EMT by downregulation of E-cadherin. RB inactivation could be a key event underlying the mesenchymal and aggressive phenotype of triple-negative breast cancer. Furthermore, exploring links between RB inactivation and EMT might reveal new therapeutic targets for triple-negative breast cancer. [ABSTRACT FROM AUTHOR]

Examines selected representations of the mythological character Melusine in French literature. Structure of the myth common to fairy stories; Depiction of Melusine in texts; Attributes of Melusine.