MicroRNA and transcription factor co-regulatory networks and subtype classification of seminoma and non-seminoma in testicular germ cell tumors

Recent studies have revealed that feed-forward loops (FFLs) as regulatory motifs have synergistic roles in cellular systems and their disruption may cause diseases including cancer. FFLs may include two regulators such as transcription factors (TFs) and microRNAs (miRNAs). In this study, we extensively investigated TF and miRNA regulation pairs, their FFLs, and TF-miRNA mediated regulatory networks in two major types of testicular germ cell tumors (TGCT): seminoma (SE) and non-seminoma (NSE). Specifically, we identified differentially expressed mRNA genes and miRNAs in 103 tumors using the transcriptomic data from The Cancer Genome Atlas. Next, we determined significantly correlated TF-gene/miRNA and miRNA-gene/TF pairs with regulation direction. Subsequently, we determined 288 and 664 dysregulated TF-miRNA-gene FFLs in SE and NSE, respectively. By constructing dysregulated FFL networks, we found that many hub nodes (12 out of 30 for SE and 8 out of 32 for NSE) in the top ranked FFLs could predict subtype-classification (Random Forest classifier, average accuracy ≥90%). These hub molecules were validated by an independent dataset. Our network analysis pinpointed several SE-specific dysregulated miRNAs (miR-200c-3p, miR-25-3p, and miR-302a-3p) and genes (EPHA2, JUN, KLF4, PLXDC2, RND3, SPI1, and TIMP3) and NSE-specific dysregulated miRNAs (miR-367-3p, miR-519d-3p, and miR-96-5p) and genes (NR2F1 and NR2F2). This study is the first systematic investigation of TF and miRNA regulation and their co-regulation in two major TGCT subtypes

MiRNAs as novel adipokines : obesity-related circulating MiRNAs influence chemosensitivity in cancer patients

Adipose tissue is an endocrine organ, capable of regulating distant physiological processes in other tissues via the release of adipokines into the bloodstream. Recently, circulating adipose-derived microRNAs (miRNAs) have been proposed as a novel class of adipokine, due to their capacity to regulate gene expression in tissues other than fat. Circulating levels of adipokines are known to be altered in obese individuals compared with typical weight individuals and are linked to poorer health outcomes. For example, obese individuals are known to be more prone to the development of some cancers, and less likely to achieve event-free survival following chemotherapy. The purpose of this review was twofold; first to identify circulating miRNAs which are reproducibly altered in obesity, and secondly to identify mechanisms by which these obesity-linked miRNAs might influence the sensitivity of tumors to treatment. We identified 8 candidate circulating miRNAs with altered levels in obese individuals (6 increased, 2 decreased). A second literature review was then performed to investigate if these candidates might have a role in mediating resistance to cancer treatment. All of the circulating miRNAs identified were capable of mediating responses to cancer treatment at the cellular level, and so this review provides novel insights which can be used by future studies which aim to improve obese patient outcomes

miRNAs as Influencers of Cell-Cell Communication in Tumor Microenvironment

microRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level, inducing the degradation of the target mRNA or translational repression. MiRNAs are involved in the control of a multiplicity of biological processes, and their absence or altered expression has been associated with a variety of human diseases, including cancer. Recently, extracellular miRNAs (ECmiRNAs) have been described as mediators of intercellular communication in multiple contexts, including tumor microenvironment. Cancer cells cooperate with stromal cells and elements of the extracellular matrix (ECM) to establish a comfortable niche to grow, to evade the immune system, and to expand. Within the tumor microenvironment, cells release ECmiRNAs and other factors in order to influence and hijack the physiological processes of surrounding cells, fostering tumor progression. Here, we discuss the role of miRNAs in the pathogenesis of multicomplex diseases, such as Alzheimer's disease, obesity, and cancer, focusing on the contribution of both intracellular miRNAs, and of released ECmiRNAs in the establishment and development of cancer niche. We also review growing evidence suggesting the use of miRNAs as novel targets or potential tools for therapeutic applications

decodeRNA-predicting non-coding RNA functions using guilt-by-association

Although the long non-coding RNA (lncRNA) landscape is expanding rapidly, only a small number of lncRNAs have been functionally annotated. Here, we present decodeRNA (http://www.decoderna.org), a database providing functional contexts for both human lncRNAs and microRNAs in 29 cancer and 12 normal tissue types. With state-of-the-art data mining and visualization options, easy access to results and a straightforward user interface, decodeRNA aims to be a powerful tool for researchers in the ncRNA field

Investigating the Regulation and Function of the NR4A Nuclear Receptors in Cancer

The nuclear receptor (NR) superfamily represents a structurally-conserved group of ligand-regulated transcription factors. These proteins have critical roles in various physiological and pathological processes, including cancer, and have been targets of drug therapy. The orphan NR subfamily 4A (NR4A), which includes the NR4A1 (Nur77), NR4A2 (Nurr1), and NR4A3 (Nor-1) genes, has been implicated in adult solid tumors and has been characterized as pro-tumorigenic mediator of cell proliferation, transformation, migration, and drug resistance. Alternatively, in leukemia, NR4A1 and NR4A3 have been described as tumor suppressors in hematologic malignancies. Members of the NR4A family are commonly overexpressed in cancer and this has been attributed to their regulation by other oncogenic signaling pathways. Despite the understanding of signaling cascades that lead to overexpression of the NR4A members, little is known about their regulation by microRNAs (miRNAs). miRNAs are small, non-coding, endogenous RNAs that are transcribed, processed, and used to direct cellular proteins that destabilize or block translation of target mRNA. In this study, we first sought to determine the miRNAs that are responsible for regulating NR4A2. Using a 3ʹ UTR reporter assay, we identified miR-34 as a regulator of the NR4A2 through its 3ʹ UTR, which was confirmed using mutagenesis of the predicted binding region of the miR-34 seed region to its target site. We demonstrated that overexpression of exogenous or induction of endogenous miR-34 expression downstream of p53 activation by Nutlin-3a was associated with decreased endogenous NR4A2. Additionally, overexpression of NR4A2 was capable of suppressing the activation of p53 target genes, and was also able to attenuate the sensitivity of cells to the anti-proliferative effect of Nutlin-3a. We further explored the roles of the NR4A family in pediatric cancer, an area that has not been fully investigated. We first determined that the members of the NR4A family are overexpressed in rhabdomyosarcoma (RMS) cell lines compared to normal muscle cells. Knockdown of NR4A1 or NR4A2 led to a reduction in cell proliferation and transformation, while knockdown of NR4A2 could also affect cell migration. Using a microarray approach, we sought to investigate the transcriptome-level changes in response to NR4A knockdown, and determined that knockdown of NR4A2 led to a unique gene signature, while NR4A1 and NR4A3 knockdown had large overlaps in expression changes. These unique gene expression changes in response to NR4A2 knockdown could explain the unique effects that NR4A2 has on migration. Overall, this study has discovered miR-34 as a novel regulator of NR4A2, and places NR4A2 in a potential feedback mechanism involving p53, miR-34, and NR4A2. This could indicate that NR4A2 mediates at least some of its pro-oncogenic effects through the inhibition of p53, which is relieved by p53 itself upon activation. Alternatively, NR4A2, is shown to have other roles in cancer progression, potentially through novel downstream target genes. These data may be used in understanding the effects of miR-34 replacement therapy, as this method of treatment is progressing through clinical trials, allowing us to understand the diverse regulator cascades being modulated

MicroRNAs in Tumor Endothelial Cells: Regulation, Function and Therapeutic Applications

Tumor endothelial cells (TECs) are key stromal components of the tumor microenvironment, and are essential for tumor angiogenesis, growth and metastasis. Accumulating evidence has shown that small single-stranded non-coding microRNAs (miRNAs) act as powerful endogenous regulators of TEC function and blood vessel formation. This systematic review provides an upto-date overview of these endothelial miRNAs. Their expression is mainly regulated by hypoxia, pro-angiogenic factors, gap junctions and extracellular vesicles, as well as long non-coding RNAs and circular RNAs. In preclinical studies, they have been shown to modulate diverse fundamental angiogenesis-related signaling pathways and proteins, including the vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathway; the rat sarcoma virus (Ras)/rapidly accelerated fibrosarcoma (Raf)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway; the phosphoinositide 3-kinase (PI3K)/AKT pathway; and the transforming growth factor (TGF)-β/TGF-β receptor (TGFBR) pathway, as well as krüppel-like factors (KLFs), suppressor of cytokine signaling (SOCS) and metalloproteinases (MMPs). Accordingly, endothelial miRNAs represent promising targets for future anti-angiogenic cancer therapy. To achieve this, it will be necessary to further unravel the regulatory and functional networks of endothelial miRNAs and to develop safe and efficient TEC-specific miRNA delivery technologies

CMTCN: a web tool for investigating cancer-specific microRNA and transcription factor co-regulatory networks

Transcription factors (TFs) and microRNAs (miRNAs) are well-characterized trans-acting essential players in gene expression regulation. Growing evidence indicates that TFs and miRNAs can work cooperatively, and their dysregulation has been associated with many diseases including cancer. A unified picture of regulatory interactions of these regulators and their joint target genes would shed light on cancer studies. Although online resources developed to support probing of TF-gene and miRNA-gene interactions are available, online applications for miRNA-TF co-regulatory analysis, especially with a focus on cancers, are lacking. In light of this, we developed a web tool, namely CMTCN (freely available at http://www.cbportal.org/CMTCN), which constructs miRNA-TF co-regulatory networks and conducts comprehensive analyses within the context of particular cancer types. With its user-friendly provision of topological and functional analyses, CMTCN promises to be a reliable and indispensable web tool for biomedical studies