Reduction of the ST6 β-galactosamide α-2,6-sialyltransferase 1 (ST6GAL1)-catalyzed sialylation of nectin-like molecule 2/cell adhesion molecule 1 and enhancement of ErbB2/ErbB3 signaling by microRNA-199a

The pro-inflammatory cytokines IL-1β and IL-6 promote upregulation of the ST6GAL1 sialyltransferase in pancreatic cancer cells

The ST6GAL1 sialyltransferase is overexpressed in multiple cancers, including pancreatic ductal adenocarcinoma (PDAC). ST6GAL1 adds an α2-6-linked sialic acid to N-glycosylated membrane receptors, which consequently modulates receptor structure and function. While many studies have investigated the effects of ST6GAL1 on cell phenotype, there is a dearth of knowledge regarding mechanisms that regulate ST6GAL1 expression. In the current study, we evaluated the regulation of ST6GAL1 by two pro-inflammatory cytokines, IL-1β and IL-6, which are abundant within the PDAC tumor microenvironment. Cytokine activity was monitored using the Suit-2 PDAC cell line and two Suit-2-derived metastatic subclones, S2-013 and S2-LM7AA. For all three cell models, treatment with IL-1β or IL-6 increased the expression of ST6GAL1 protein and mRNA. Specifically, IL-1β and IL-6 induced expression of the ST6GAL1 YZ mRNA isoform, which is driven by the P3 promoter. The ST6GAL1 H and X isoforms were not detected. Promoter reporter assays confirmed that IL-1β and IL-6 activated transcription from the P3 promoter. We then examined downstream signaling mechanisms. IL-1β is known to signal through the NFκB transcription factor, whereas IL-6 signals through the STAT3 transcription factor. CUT&RUN experiments revealed that IL-1β promoted the binding of NFκB to the ST6GAL1 P3 promoter, and IL-6 induced the binding of STAT3 to the P3 promoter. Finally, we determined that inhibitors of NFκB and STAT3 blocked the upregulation of ST6GAL1 stimulated by IL-1β and IL-6, respectively. Together, these results highlight a novel molecular pathway by which cytokines within the tumor microenvironment stimulate the upregulation of ST6GAL1 in PDAC cells.

The Mutual Relationship between Glycosylation and Non-Coding RNAs in Cancer and Other Physio-Pathological Conditions

Glycosylation, which consists of the enzymatic addition of sugars to proteins and lipids, is one of the most important post-co-synthetic modifications of these molecules, profoundly affecting their activity. Although the presence of carbohydrate chains is crucial for fine-tuning the interactions between cells and molecules, glycosylation is an intrinsically stochastic process regulated by the relative abundance of biosynthetic (glycosyltransferases) and catabolic (glycosidases) enzymes, as well as sugar carriers and other molecules. Non-coding RNAs, which include microRNAs, long non-coding RNAs and circRNAs, establish a complex network of reciprocally interacting molecules whose final goal is the regulation of mRNA expression. Likewise, these interactions are stochastically regulated by ncRNA abundance. Thus, while protein sequence is deterministically dictated by the DNA/RNA/protein axis, protein abundance and activity are regulated by two stochastic processes acting, respectively, before and after the biosynthesis of the protein axis. Consequently, the worlds of glycosylation and ncRNA are closely interconnected and mutually interacting. In this paper, we will extensively review the many faces of the ncRNA-glycosylation interplay in cancer and other physio-pathological conditions.

Sialyltransferases and Neuraminidases: Potential Targets for Cancer Treatment

Cancers are the leading cause of death, causing around 10 million deaths annually by 2020. The most common cancers are those affecting the breast, lungs, colon, and rectum. However, it has been noted that cancer metastasis is more lethal than just cancer incidence and accounts for more than 90% of cancer deaths. Thus, early detection and prevention of cancer metastasis have the capability to save millions of lives. Finding novel biomarkers and targets for screening, determination of prognosis, targeted therapies, etc., are ways of doing so. In this review, we propose various sialyltransferases and neuraminidases as potential therapeutic targets for the treatment of the most common cancers, along with a few rare ones, on the basis of existing experimental and in silico data. This compilation of available cancer studies aiming at sialyltransferases and neuraminidases will serve as a guide for scientists and researchers working on possible targets for various cancers and will also provide data about the existing drugs which inhibit the action of these enzymes.

ST6Gal1: Oncogenic signaling pathways and targets

The Golgi-sialyltransferase ST6Gal1 (βgalactosidase α2,6 sialyltransferase 1), adds the negatively charged sugar, sialic acid, to the terminal galactose of N-glycosylated proteins. Upregulation of ST6Gal1 is observed in many malignancies, and a large body of research has determined that ST6Gal1-mediated α2,6 sialylation impacts cancer hallmarks. ST6Gal1 affects oncogenic behaviors including sustained proliferation, enhanced self-renewal, epithelial-to-mesenchymal transition, invasion, and chemoresistance. However, there are relatively few ST6GaL1 related signaling pathways that are well-established to mediate these biologies: greater delineation of specific targets and signaling mechanisms that are orchestrated by ST6Gal1 is needed. The aim of this review is to provide a summary of our current understanding of select oncogenic signaling pathways and targets affected by ST6Gal1.

Emerging roles of the nectin family of cell adhesion molecules in tumour-associated pathways

Tumour cells achieve maximum survival by modifying cellular machineries associated with processes such as cell division, migration, survival, and apoptosis, resulting in genetically complex and heterogeneous populations. While nectin and nectin-like cell adhesion molecules control development and maintenance of multicellular organisation in higher vertebrates by mediating cell-cell adhesion and related signalling processes, recent studies indicate that they also critically regulate growth and development of different types of cancers. In this review, we detail current knowledge about the role of nectin family members in various tumours. Furthermore, we also analyse the seemingly opposing roles of some members of nectin family in tumour-associated pathways, as they function as both tumour suppressors and oncogenes. Understanding this functional duality of nectin family in tumours will further our knowledge of molecular mechanisms regulating tumour development and progression, and contribute to the advancement of tumour diagnosis and therapy.

Abnormal saccharides affecting cancer multi-drug resistance (MDR) and the reversal strategies

Clinically, chemotherapy is the mainstay in the treatment of multiple cancers. However, highly adaptable and activated survival signaling pathways of cancer cells readily emerge after long exposure to chemotherapeutics drugs, resulting in multi-drug resistance (MDR) and treatment failure. Recently, growing evidences indicate that the molecular action mechanisms of cancer MDR are closely associated with abnormalities in saccharides. In this review, saccharides affecting cancer MDR development are elaborated and analyzed in terms of aberrant aerobic glycolysis and its related enzymes, abnormal glycan structures and their associated enzymes, and glycoproteins. The reversal strategies including depletion of ATP, circumventing the original MDR pathway, activation by or inhibition of sugar-related enzymes, combination therapy with traditional cytotoxic agents, and direct modification on the sugar moiety, are ultimately proposed. It follows that abnormal saccharides have a significant effect on cancer MDR development, providing a new perspective for overcoming MDR and improving the outcome of chemotherapy.

Regulation of breast cancer metastasis signaling by miRNAs

Despite the decline in death rate from breast cancer and recent advances in targeted therapies and combinations for the treatment of metastatic disease, metastatic breast cancer remains the second leading cause of cancer-associated death in U.S. women. The invasion-metastasis cascade involves a number of steps and multitudes of proteins and signaling molecules. The pathways include invasion, intravasation, circulation, extravasation, infiltration into a distant site to form a metastatic niche, and micrometastasis formation in a new environment. Each of these processes is regulated by changes in gene expression. Noncoding RNAs including microRNAs (miRNAs) are involved in breast cancer tumorigenesis, progression, and metastasis by post-transcriptional regulation of target gene expression. miRNAs can stimulate oncogenesis (oncomiRs), inhibit tumor growth (tumor suppressors or miRsupps), and regulate gene targets in metastasis (metastamiRs). The goal of this review is to summarize some of the key miRNAs that regulate genes and pathways involved in metastatic breast cancer with an emphasis on estrogen receptor α (ERα+) breast cancer. We reviewed the identity, regulation, human breast tumor expression, and reported prognostic significance of miRNAs that have been documented to directly target key genes in pathways, including epithelial-to-mesenchymal transition (EMT) contributing to the metastatic cascade. We critically evaluated the evidence for metastamiRs and their targets and miRNA regulation of metastasis suppressor genes in breast cancer progression and metastasis. It is clear that our understanding of miRNA regulation of targets in metastasis is incomplete.

Regulation of ST6GAL1 sialyltransferase expression in cancer cells

The ST6GAL1 sialyltransferase, which adds α2-6 linked sialic acids to N-glycosylated proteins, is overexpressed in a wide range of human malignancies. Recent studies have established the importance of ST6GAL1 in promoting tumor cell behaviors such as invasion, resistance to cell stress and chemoresistance. Furthermore, ST6GAL1 activity has been implicated in imparting cancer stem cell characteristics. However, despite the burgeoning interest in the role of ST6GAL1 in the phenotypic features of tumor cells, insufficient attention has been paid to the molecular mechanisms responsible for ST6GAL1 upregulation during neoplastic transformation. Evidence suggests that these mechanisms are multifactorial, encompassing genetic, epigenetic, transcriptional and posttranslational regulation. The purpose of this review is to summarize current knowledge regarding the molecular events that drive enriched ST6GAL1 expression in cancer cells.

Restoring of miR-193a-5p Sensitizes Breast Cancer Cells to Paclitaxel through P53 Pathway

Purpose: Recent evidence presented the important role of microRNAs in health and disease particularly in human cancers. Among those, miR-193 family contributes as a tumor suppressor in different benign and malignant cancers like breast cancer (BC) via interaction with specific targets. On the other hand, it was stated that miR-193 is able to modulate some targets in chemoresistant cancer cells. Therefore, the aim of this study was to evaluate the potential function of miR-193a-5p and paclitaxel in the apoptosis induction by targeting P53 in BC cells.

Methods: At first, miR-193a-5p mimics were transfected to MDA-MB-231 BC cell line which indicated the lower expression level of miR-193a-5p. Subsequently, the transfected cells were treated with paclitaxel. Then, cell viability, apoptosis, and migration were evaluated by MTT, flow cytometry and DAPI staining, and scratch-wound motility assays, respectively. Moreover, the expression levels of P53 was evaluated by qRT-PCR.

Results: The expression level of miR-193a-5p was restored in MDA-MB-231 cells which profoundly inhibited the proliferation (P<0.0001), induced apoptosis (P <0.0001) and harnessed migration (P <0.0001) in the BC cells and more effectiveness was observed in combination with paclitaxel. Interestingly, increased miR-193a-5p expression led to a reduction in P53 mRNA, offering that it can be a potential target of miR-193a.

Conclusion: Taken together, it is concluded that the combination of miR-193a-5p restoration and paclitaxel could be potentially considered as an effective therapeutic strategy to get over chemoresistance during paclitaxel chemotherapy

Insight in Adhesion Protein Sialylation and Microgravity Dependent Cell Adhesion-An Omics Network Approach

The adhesion behavior of human tissue cells changes in vitro, when gravity forces affecting these cells are modified. To understand the mechanisms underlying these changes, proteins involved in cell-cell or cell-extracellular matrix adhesion, their expression, accumulation, localization, and posttranslational modification (PTM) regarding changes during exposure to microgravity were investigated. As the sialylation of adhesion proteins is influencing cell adhesion on Earth in vitro and in vivo, we analyzed the sialylation of cell adhesion molecules detected by omics studies on cells, which change their adhesion behavior when exposed to microgravity. Using a knowledge graph created from experimental omics data and semantic searches across several reference databases, we studied the sialylation of adhesion proteins glycosylated at their extracellular domains with regards to its sensitivity to microgravity. This way, experimental omics data networked with the current knowledge about the binding of sialic acids to cell adhesion proteins, its regulation, and interactions in between those proteins provided insights into the mechanisms behind our experimental findings, suggesting that balancing the sialylation against the de-sialylation of the terminal ends of the adhesion proteins' glycans influences their binding activity. This sheds light on the transition from two- to three-dimensional growth observed in microgravity, mirroring cell migration and cancer metastasis in vivo.

A comprehensive review on miR-451: A promising cancer biomarker with therapeutic potential

MicroRNAs (miRNAs) are proposed as a family of short noncoding molecules able to manage and control the expression of the gene targets at the posttranscriptional level. They contribute in several fundamental physiological mechanisms as well as a verity of human and animal diseases such as cancer progression. Among these tiny RNAs, miR-451 placed on chromosome 17 at 17q11.2 presents an essential role in many biological processes in health condition and also in pathogenesis of different diseases. Besides, it has been recently considered as a valuable biomarker for cancer detection, prognosis and treatment. Therefore, this review will provide the critical functions of miR-451 on biological mechanisms including cell cycle and proliferation, cell survival and apoptosis, differentiation and development as well as disease initiation and progression such as tumor formation, migration, invasion, and metastasis.

miR-193: A new weapon against cancer

microRNAs (miRNAs) are known as a large group of short noncoding RNAs, which structurally consist of 19-22 nucleotides in length and functionally act as one of the main regulators of gene expression in important biological and physiological contexts like cell growth, apoptosis, proliferation, differentiation, movement (cell motility), and angiogenesis as well as disease formation and progression importantly in cancer cell invasion, migration, and metastasis. Among these notable tiny molecules, many studies recently presented the important role of the miR-193 family comprising miR-193a-3p, miR-193a-5p, miR-193b-3p, and miR-193b-5p in health and disease biological processes by interaction with special targeting and signaling, which mainly contribute as a tumor suppressor. Therefore, in the present paper, we review the functional role of this miRNA family in both health and disease conditions focusing on various tumor developments, diagnoses, prognoses, and treatment.

Glycosylation as a Main Regulator of Growth and Death Factor Receptors Signaling

Glycosylation is a very frequent and functionally important post-translational protein modification that undergoes profound changes in cancer. Growth and death factor receptors and plasma membrane glycoproteins, which upon activation by extracellular ligands trigger a signal transduction cascade, are targets of several molecular anti-cancer drugs. In this review, we provide a thorough picture of the mechanisms bywhich glycosylation affects the activity of growth and death factor receptors in normal and pathological conditions. Glycosylation affects receptor activity through three non-mutually exclusive basic mechanisms: (1) by directly regulating intracellular transport, ligand binding, oligomerization and signaling of receptors; (2) through the binding of receptor carbohydrate structures to galectins, forming a lattice thatregulates receptor turnover on the plasma membrane; and (3) by receptor interaction with gangliosides inside membrane microdomains. Some carbohydrate chains, for example core fucose and β1,6-branching, exert a stimulatory effect on all receptors, while other structures exert opposite effects on different receptors or in different cellular contexts. In light of the crucial role played by glycosylation in the regulation of receptor activity, the development of next-generation drugs targeting glyco-epitopes of growth factor receptors should be considered a therapeutically interesting goal.

Upregulation of miR-181c inhibits chemoresistance by targeting ST8SIA4 in chronic myelocytic leukemia

Chemotherapy resistance frequently drives tumor progression. Increased expression of ST8SIA4 has been reported in diverse carcinomas and highly correlates with leukemia multidrug resistance (MDR). MicroRNAs (miRNA) are widely recognized as key players in cancer progression and drug resistance. Here, to explore whether miRNA modulates the sensitivity of chronic myelocytic leukemia (CML) to chemotherapeutic agents and regulates ST8SIA4 expression, we analyzed the complete miRNA expression profile and found a subset of miRNAs specifically dysregulated in adriamycin-resistant CML cell line K562/ADR and its parent cell line K562. Compared with three pairs of CML cell lines and 38 clinical samples of peripheral blood mononuclear cells (PBMC) of CML patients, miR-181c expression was down-regulated in drug-resistant cell lines and CML/MDR samples. Altered expression levels of miR-181c influenced the MDR phenotypes of K562 and K562/ADR. Reporter-gene assay showed that miR-181c directly targeted and inhibited the ST8SIA4 expression, as well as miR-181c was inversely correlated with the levels of ST8SIA4 expression in CML cell lines and samples. Moreover, ST8SIA4 could reverse the effect of miR-181c on drug resistance in K562 and K562/ADR cells in vitro. Upregulation of miR-181c sensitized K562/ADR cells to adriamycin in vivo through directly suppressing ST8SIA4 expression. Further investigation showed that miR-181c mediated the activity of phosphoinositide-3 kinase (PI3K)/AKT signal pathway, and inhibition of PI3K/Akt in K562 cells counteracted miR-181c-mediated MDR phenotype. These data revealed an important role for miR-181c in the regulation of chemoresistance in CML, and suggested the potential application of miR-181c in drug resistance treatment.

Nectin-like molecule-4/cell adhesion molecule 4 inhibits the ligand-induced dimerization of ErbB3 with ErbB2

The ligand-induced dimerization of cell surface single-transmembrane receptors is essential for their activation. However, physiological molecules that inhibit their dimerization and activation have not been identified. ErbB3 dimerizes with ErbB2 upon binding of heregulin (HRG) to ErbB3, causing the ErbB2-catalyzed tyrosine phosphorylation of ErbB3, which leads to the activation of the signalling pathways for cell movement and survival. Genetic disorders of this receptor cause tumorigenesis and metastasis of cancers. We show here that nectin-like molecule-4/cell adhesion molecule 4, known to serve as a tumour suppressor, interacts with ErbB3 in the absence of HRG and inhibits the HRG-induced dimerization of ErbB3 with ErbB2 and its activation. The third immunoglobulin-like domain of nectin-like molecule-4 cis-interacts with the extracellular domain 3 of ErbB3. We describe here a novel regulatory mechanism for the activation and signalling of cell surface single-transmembrane receptors.

Epigenetic Bases of Aberrant Glycosylation in Cancer

In this review, the sugar portions of glycoproteins, glycolipids, and glycosaminoglycans constitute the glycome, and the genes involved in their biosynthesis, degradation, transport and recognition are referred to as “glycogenes“. The extreme complexity of the glycome requires the regulatory layer to be provided by the epigenetic mechanisms. Almost all types of cancers present glycosylation aberrations, giving rise to phenotypic changes and to the expression of tumor markers. In this review, we discuss how cancer-associated alterations of promoter methylation, histone methylation/acetylation, and miRNAs determine glycomic changes associated with the malignant phenotype. Usually, increased promoter methylation and miRNA expression induce glycogene silencing. However, treatment with demethylating agents sometimes results in silencing, rather than in a reactivation of glycogenes, suggesting the involvement of distant methylation-dependent regulatory elements. From a therapeutic perspective aimed at the normalization of the malignant glycome, it appears that miRNA targeting of cancer-deranged glycogenes can be a more specific and promising approach than the use of drugs, which broad target methylation/acetylation. A very specific type of glycosylation, the addition of GlcNAc to serine or threonine (O-GlcNAc), is not only regulated by epigenetic mechanisms, but is an epigenetic modifier of histones and transcription factors. Thus, glycosylation is both under the control of epigenetic mechanisms and is an integral part of the epigenetic code.

miR-21 enhances cardiac fibrotic remodeling and fibroblast proliferation via CADM1/STAT3 pathway

Background

Cardiac fibrosis play a key role in the atrial fibrillation pathogenesis but the underlying potential molecular mechanism is still understood. However, potential mechanisms for miR-21 upregulation and its role in cardiac fibrosis remain unclear. The controls cell proliferation and processes fundamental to disease progression.

Methods

In this study, immunohistochemistry, real-time RT-PCR, cell transfection, cell cycle, cell proliferation and Western blot were used, respectively.

Results

Here we have been demonstrated that the tumor suppressor cell adhesion molecule 1 (CADM1) is the potential target of miR-21. Our study revealed that miR-21 regulation of CADM1 expression, which was decreased in cardiac fibroblasts and fibrosis tissue. The cardiac fibroblasts transfected with miR-21 mimic promoted miR-21 overexpression enhanced STAT3 expression and decreased CADM1 expression. Nevertheless, the cardiac fibroblasts transfected with miR-21 inhibitor obtained the opposite expression result. Furthermore, downexpression of miR-21 suppressed cardiac fibroblast proliferation.

Conclusions

These results suggested that miR-21 overexpression promotes cardiac fibrosis via STAT3 signaling pathway by decrease CADM1 expression, indicating miR-21 as an important signaling molecule for cardiac fibrotic remodeling and AF.

Functional roles of sialylation in breast cancer progression through miR-26a/26b targeting ST8SIA4

Sialylation is one of the altered glycosylation patterns associated with cancer progression. In this study, we investigated the N-glycan profiles of breast cancer patients and cell lines to reveal sialylation associated with breast cancer progression, and provided new evidences of miRNA-mediated sialylation. MALDI-TOF MS analysis revealed that N-glycans found in breast cancer tissues and breast cancer cell MDA-MB-231 featured increased levels of sialylation compared with adjacent tissues and normal breast epithelial cell MCF-10A. The expressional profiles of 20 sialyltransferase genes were then analyzed and found significantly different comparing breast cancer samples with adjacent tissues, and two breast cancer cell lines MDA-MB-231 and MCF-7 with different metastatic potential and MCF-10A cells. Tumor tissues and highly metastatic breast cancer cell line MDA-MB-231 exhibited higher levels of ST8SIA4. Knocking down ST8SIA4 in breast cancer cell lines significantly inhibited their malignant behaviors including cell proliferation and invasion in a sialyltransferase-dependent manner. By applying bioinformatic approaches for the prediction of miRNA targeting 3′-UTR of ST8SIA4, we identified ST8SIA4 as one of the miR-26a/26b-targeted genes. Further data analysis revealed the inversely related expression of ST8SIA4 and miR-26a/26b in breast cancer cells, tumor tissues and corresponding adjacent tissues. The ability of miR-26a/26b to interact specifically with and regulate the 3′-UTR of ST8SIA4 was demonstrated via a luciferase reporter assay. The forced expression of miR-26a/26b was able to induce a decrease of ST8SIA4 level and also to affect breast cancer cells progression, while altered expression of ST8SIA4 in breast cancer cells modulated progression upon transfection with miR-26a/26b mimics or inhibiter. Taken together, these results indicate that changes in the glycosylation patterns and sialylation levels may be useful markers of the progression of breast cancer, as well as miR-26a/26b may be widely involved in the regulation of sialylation machinery by targeting ST8SIA4.

The Inhibitory Role of α2,6-Sialylation in Adipogenesis

Adipose tissue plays critical roles in obesity and related diseases such as diabetes and cardiovascular diseases. Previous reports suggest that glycans, the most common posttranslational modifications, are involved in obesity-related diseases, but what type of glycan regulates adipogenesis during obesity remains unclear. In this study, we first quantified the mRNA levels of 167 genes (encoding 144 glycosyltransferases and 23 related enzymes) in visceral adipose tissues (VATs) from control mice and high-fat diet (HFD)-induced obese mice. We found that a gene encoding β-galactoside α2,6-sialyltransferase-1 (St6gal1), a key enzyme responsible for the biosynthesis of α2,6-linked sialic acid in N-linked glycans, was most down-regulated in VATs from obese mice. We confirmed the reduction in α2,6-sialic acid in VATs from obese mice and differentiated adipocyte model 3T3-L1 cells. Using proteomic analysis, integrin-β1 was identified as one of the target α2,6-sialylated proteins in adipose tissues, and phosphorylation of its downstream molecule focal adhesion kinase was found to be decreased after HFD feeding. St6gal1 overexpression in differentiating 3T3-L1 cells inhibited adipogenesis with increased phosphorylation of focal adhesion kinase. Furthermore, St6gal1 knockout mice exhibited increased bodyweight and VAT weight after HFD feeding. The down-regulation of St6gal1 during adipogenesis was canceled by treatment with a DNA methyltransferase inhibitor, suggesting an involvement of epigenetic DNA methylation in St6gal1 silencing. Our findings suggest that ST6GAL1 has an inhibitory role in adipogenesis through integrin-β1 activation, providing new insights into the roles and regulation mechanisms of glycans in adipocytes during obesity.

miR-493-5p attenuates the invasiveness and tumorigenicity in human breast cancer by targeting FUT4

Breast cancer is a leading cause of cancer-related mortality among women. Altered fucosylation was found to be closely associated with tumorigenesis and metastasis of breast cancer. MicroRNAs (miRNAs) are important regulators of cell proliferation and metastasis, and aberrant miRNA expression has been observed in breast cancer. The present study aimed to evaluate the level of fucosyltransferase IV (FUT4) and miR-493-5p in breast cancer and investigate their relationship. In the present study, we demonstrated the differential expressional profiles of FUT4 and miR‑493-5p in 29 clinical breast cancer tissues, matched adjacent tissue samples and two breast carcinoma cell lines (MCF-7 and MDA-MB-231). Briefly, altered expression levels of FUT4 modified the invasive activities and tumorigenicity of the MCF-7 and MDA-MB-231 cells. Further study demonstrated that miR-493-5p plays a role as a suppressor in breast cancer cell invasion and tumorigenicity. Moreover, the expression levels of miR-493-5p were inversely proportional to those of FUT4 both at the mRNA and protein levels. Luciferase reporter assays confirmed that miR‑493-5p bound to the 3'-untranslated (3'-UTR) region of FUT4, and inhibited the expression of FUT4 in breast cancer cells. Taken together, our data suggest that FUT4 may have a potential role in the treatment of breast cancer, as well as miR-493-5p is a novel regulator of invasiveness and tumorigenicity of breast cancer cells through targeting FUT4. The miR-493-5p/FUT4 pathway has therapeutic potential in breast cancer.

Role of Small RNAs in Trypanosomatid Infections

Trypanosomatid parasites survive and replicate in the host by using mechanisms that aim to establish a successful infection and ensure parasite survival. Evidence points to microRNAs as new players in the host-parasite interplay. MicroRNAs are small non-coding RNAs that control proteins levels via post-transcriptional gene down-regulation, either within the cells where they were produced or in other cells via intercellular transfer. These microRNAs can be modulated in host cells during infection and are among the growing group of small regulatory RNAs, for which many classes have been described, including the transfer RNA-derived small RNAs. Parasites can either manipulate microRNAs to evade host-driven damage and/or transfer small RNAs to host cells. In this mini-review, we present evidence for the involvement of small RNAs, such as microRNAs, in trypanosomatid infections which lack RNA interference. We highlight both microRNA profile alterations in host cells during those infections and the horizontal transfer of small RNAs and proteins from parasites to the host by membrane-derived extracellular vesicles in a cell communication mechanism.

Human T-cell leukemia virus type 1 (HTLV-1) tax requires CADM1/TSLC1 for inactivation of the NF-κB inhibitor A20 and constitutive NF-κB signaling

Persistent activation of NF-κB by the Human T-cell leukemia virus type 1 (HTLV-1) oncoprotein, Tax, is vital for the development and pathogenesis of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). K63-linked polyubiquitinated Tax activates the IKK complex in the plasma membrane-associated lipid raft microdomain. Tax also interacts with TAX1BP1 to inactivate the NF-κB negative regulatory ubiquitin-editing A20 enzyme complex. However, the molecular mechanisms of Tax-mediated IKK activation and A20 protein complex inactivation are poorly understood. Here, we demonstrated that membrane associated CADM1 (Cell adhesion molecule1) recruits Ubc13 to Tax, causing K63-linked polyubiquitination of Tax, and IKK complex activation in the membrane lipid raft. The c-terminal cytoplasmic tail containing PDZ binding motif of CADM1 is critical for Tax to maintain persistent NF-κB activation. Finally, Tax failed to inactivate the NF-κB negative regulator ubiquitin-editing enzyme A20 complex, and activate the IKK complex in the lipid raft in absence of CADM1. Our results thus indicate that CADM1 functions as a critical scaffold molecule for Tax and Ubc13 to form a cellular complex with NEMO, TAX1BP1 and NRP, to activate the IKK complex in the plasma membrane-associated lipid rafts, to inactivate NF-κB negative regulators, and maintain persistent NF-κB activation in HTLV-1 infected cells.

HTLV-1 infection leads to the development of Adult T-cell Leukemia (ATL) or HTLV-1 associated myelopathy/ tropical spastic paraparesis (HAM/TSP). One of the major causes responsible for the development of HTLV-1 associated diseases is chronic inflammation directed by NF-kappaB (NF-κB). NF-κB activation in response to a wide variety of signals is transient and tightly controlled by ubiquitin-editing enzyme A20. One of the mechanisms of persistent NF-κB activation in HTLV-1 infected cells is inactivation of NF-κB negative regulators; however, the precise mechanism is unknown. Here, we focused on host tumor suppressor Cell adhesion molecule 1 (CADM1) that is robustly upregulated in HTLV-1 infected cells. The expression of CADM1 is frequently silenced in several cancers; however, it is critical for HTLV-1 associated ATL tumor cell survival. We characterized the role of CADM1 in persistent NF-κB activation in HTLV-1 infected cells. We found that CADM1 is required for the HTLV-1 oncoprotein, Tax, to form a cellular complex with Ubc13, TAX1BP1, NRP and NEMO in the membrane lipid rafts micorodomain. We further demonstrated that Tax requires CADM1 to inactivate NF-κB negative regulator and maintain persistent NF-κB activation. Our study reveals a novel mechanism of chronic NF-κB activation by CADM1 in HTLV-1 infected cells.

A global microRNA screen identifies regulators of the ErbB receptor signaling network

Background

The growth factor heregulin (HRG) potently stimulates epithelial cell survival and proliferation through the binding of its cognate receptor ErbB3 (also known as HER3). ErbB3-dependent signal transmission relies on the dimerization partner ErbB2, a receptor tyrosine kinase that is frequently overexpressed and/or amplified in breast cancer cells. Substantial evidence suggests that deregulated ErbB3 expression also contributes to the transformed phenotype of breast cancer cells.

Results

By genome-wide screening, we identify 43 microRNAs (miRNAs) that specifically impact HRG-induced activation of the PI3K-Akt pathway. Bioinformatic analysis combined with experimental validation reveals a highly connected molecular miRNA-gene interaction network particularly for the negative screen hits. For selected miRNAs, namely miR-149, miR-148b, miR-326, and miR-520a-3p, we demonstrate the simultaneous downregulation of the ErbB3 receptor and multiple downstream signaling molecules, explaining their efficient dampening of HRG responses and ascribing to these miRNAs potential context-dependent tumor suppressive functions.

Conclusions

Given the contribution of HRG signaling and the PI3K-Akt pathway in particular to tumorigenesis, this study not only provides mechanistic insight into the function of miRNAs but also has implications for future clinical applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-015-0084-z) contains supplementary material, which is available to authorized users.

Suppression of the TGF-β1-induced protein expression of SNAI1 and N-cadherin by miR-199a

MicroRNA miR-199a is clustered with miR-214 on chromosome 1 and its expression is up-regulated by various factors that are associated with epithelial-to-mesenchymal transition (EMT), such as a transcriptional repressor Twist1 and transforming growth factor (TGF)-β. miR-199a is either up-regulated or down-regulated in a variety of cancers, although EMT is associated with the progression of cancer. We found here that miR-199a suppressed the translation of SNAI1, a transcriptional repressor that plays a role in EMT, by targeting the sequence within the 3'UTR of the SNAI1 mRNA, and reduced the protein level of SNAI1. miR-199a increased the protein level of claudin-1 in both the TGF-β1-treated and -untreated cells at least partly by decreasing the protein level of SNAI1, a transcriptional repressor for claudin-1. In addition, miR-199a targeted the sequence within the 3'UTR of the N-cadherin mRNA and suppressed the TGF-β1-induced increase in the protein level of N-cadherin in a manner independent of SNAI1. These results indicate that miR-199a suppresses the TGF-β1-induced protein expression of SNAI1 and N-cadherin.

MicroRNA-193a-3p and -5p suppress the metastasis of human non-small-cell lung cancer by downregulating the ERBB4/PIK3R3/mTOR/S6K2 signaling pathway

The metastatic cascade is a complex and multistep process with many potential barriers. Recent evidence has shown that microRNAs (miRNAs) are involved in carcinogenesis and tumor progression in non-small-cell lung cancer (NSCLC). In this study, by comparing the miRNA expression profiles of SPC-A-1sci (high metastatic) and SPC-A-1 (weakly metastatic) cells, we demonstrated that the downregulation and function of miR-193a-3p and miR-193a-5p in NSCLC metastasis and the expression of these miRNAs was suppressed in NSCLC compared with corresponding non-tumorous tissues. Decreased miR-193a-3p/5p expression was significantly associated with tumor node metastasis (TNM) and lymph node metastasis. Furthermore, functional assays showed that the overexpression of miR-193a-3p/5p inhibited NSCLC cell migration, invasion and epithelial-mesenchymal transition (EMT) in vitro and lung metastasis formation in vivo. In addition, we discovered that ERBB4 and S6K2 were the direct targets of miR-193a-3p and that PIK3R3 and mTOR were the direct targets of miR-193a-5p in NSCLC. We also observed that miR-193a-3p/5p could inactivate the AKT/mTOR signaling pathway. Thus, miR-193a-3p/5p functions as a tumor suppressor and has an important role in NSCLC metastasis through ERBB signaling pathway.

Interaction of Necl-4/CADM4 with ErbB3 and integrin α6 β4 and inhibition of ErbB2/ErbB3 signaling and hemidesmosome disassembly

Nectin-like molecule 4 (Necl-4)/CADM4, a transmembrane cell-cell adhesion molecule with three Ig-like domains, was shown to serve as a tumor suppressor, but its mode of action has not been elucidated. In this study, we showed that Necl-4 interacted in cis with ErbB3 through their extracellular regions, recruited PTPN13 and inhibited the heregulin-induced activation of the ErbB2/ErbB3 signaling. In addition, we extended our previous finding that Necl-4 interacts in cis with integrin α6 β4 through their extracellular regions and found that Necl-4 inhibited the phorbol ester-induced disassembly of hemidesmosomes. These results indicate that Necl-4 serves as a tumor suppressor by inhibiting the ErbB2/ErbB3 signaling and hemidesmosome disassembly.