Regulation of miRNA biogenesis as an integrated component of growth factor signaling

Lau AT, Xu YM. The regulation of microRNAs on chemoresistance in triple-negative breast cancer: a recent update

Triple-negative breast cancer (TNBC) has negative expressions of ER, PR and HER2. Due to the insensitivity to both endocrine therapy and HER2-targeted therapy, the main treatment method for TNBC is cytotoxic chemotherapy. However, the curative effect of chemotherapy is limited because of the existence of acquired or intrinsic multidrug resistance. MicroRNAs (miRNAs) are frequently dysregulated in malignant tumors and involved in tumor occurrence and progression. Interestingly, growing studies show that miRNAs are involved in chemoresistance in TNBC. Thus, targeting dysregulated miRNAs could be a plausible way for better treatment of TNBC. Here, we present the updated knowledge of miRNAs associated with chemoresistance in TNBC, which may be helpful for the early diagnosis, prognosis and treatment of this life-threatening disease.

Multifaceted TGF-β signaling, a master regulator: From bench-to-bedside, intricacies, and complexities

Physiological embryogenesis and adult tissue homeostasis are regulated by transforming growth factor-β (TGF-β), an evolutionarily conserved family of secreted polypeptide factors, acting in an autocrine and paracrine manner. The role of TGF-β in inflammation, fibrosis, and cancer is complex and sometimes even contradictory, exhibiting either inhibitory or promoting effects depending on the stage of the disease. Under pathological conditions, especially fibrosis and cancer, overexpressed TGF-β causes extracellular matrix deposition, epithelial-mesenchymal transition, cancer-associated fibroblast formation, and/or angiogenesis. In this review article, we have tried to dive deep into the mechanism of action of TGF-β in inflammation, fibrosis, and carcinogenesis. As TGF-β and its downstream signaling mechanism are implicated in fibrosis and carcinogenesis blocking this signaling mechanism appears to be a promising avenue. However, targeting TGF-β carries substantial risk as this pathway is implicated in multiple homeostatic processes and is also known to have tumor-suppressor functions. There is a need for careful dosing of TGF-β drugs for therapeutic use and patient selection.

Essential role of the amino-terminal region of Drosha for the Microprocessor function

Drosha is a core component of the Microprocessor complex that cleaves primary-microRNAs (pri-miRNAs) to generate precursor-miRNA and regulates the expression of ∼80 ribosomal protein (RP) genes. Despite the fact that mutations in the amino-terminal region of Drosha (Drosha-NTR) are associated with a vascular disorder, hereditary hemorrhagic telangiectasia, the precise function of Drosha-NTR remains unclear. By deleting exon 5 from the Drosha gene and generating a Drosha mutant lacking the NTR (ΔN), we demonstrate that ΔN is unable to process pri-miRNAs, which leads to a global miRNA depletion, except for the miR-183/96/182 cluster. We find that Argonaute 2 facilitates the processing of the pri-miR-183/96/182 in ΔN cells. Unlike full-length Drosha, ΔN is not degraded under serum starvation, resulting in unregulated RP biogenesis and protein synthesis in ΔN cells, allowing them to evade growth arrest. This study reveals the essential role of Drosha-NTR in miRNA production and nutrient-dependent translational control.

Identification and analysis of differentially expressed microRNAs in gibel carp Carassius auratus gibelio responding to polyinosinic-polycytidylic acid (poly I:C) stimulation

Polyinosinic-polycytidylic acid (poly I:C) is a synthesized analogue of viral double-strand RNA and considered as a potential immunostimulant in aquaculture. MicroRNAs (miRNAs) have been reported to play important roles in the development of the immune system and in regulation of host antiviral responses. In our earlier study, it was found that poly I:C pre-treatment could stimulate the resistance against cyprinid herpesvirus 2 (CyHV-2) infection and enhance the antiviral immune response in gibel carp. To understand the role of miRNAs in regulating the host response to poly I:C treatment, we investigated the expression profiles of miRNAs in the head kidney of poly I:C-treated gibel carp with small RNA sequencing technology. When compared with the untreated group, a total of 24 differentially expressed miRNAs were identified in the poly I:C-stimulated fish, among which, 7 and 17 miRNAs were upregulated and downregulated, respectively. Analysis of target genes of these differentially expressed miRNAs found that most targeted mRNAs were involved in catalytic activity, peptidase activity and endopeptidase activity, and were enriched in the metabolic, protein processing in endoplasmic reticulum and oxidative phosphorylation signaling pathways, suggesting that poly I:C could alter the expression of metabolism-related miRNAs in the kidney of gibel carp. Besides, it was noted that some immune-related miRNAs, including inflammation-related miRNAs (miR-192 and miR-731) and interferon-related miRNAs (miR-194a and miR-122), were downregulated after poly I:C treatment. In summary, it was found that poly I:C could regulate the cellular levels of specific miRNAs involved in metabolism and immune responses in the head kidney of gibel carp, which may increase the capacity of the immune cells to fight against pathogens infection.

Evaluating the Effects of MicroRNAs on Proteoglycans and Matrix Constituents' Expression and Functional Properties

Circulating microRNAs (miRNAs) possess significant roles in normal homeostasis and disease conditions, including cardiovascular diseases, fibrosis, inflammatory response, and cancer. Secreted miRNAs, via the membrane vesicles, actively communicate with extracellular matrix (ECM) components to affect cell-cell and cell-matrix interactions, thereby affecting matrix remodeling and metabolic pathways in the recipient cells. Matrix macromolecules regulate the expression of miRNAs, and in turn miRNAs have been identified as emerging mediators of matrix constituents, serving as appealing biomarkers for many pathophysiological processes. Therefore, the expression profile of certain miRNAs highlights the importance of their targeting in several aspects of human pathologies. In this chapter, we report molecular biology protocols to determine the effects of selected miRNAs on the expression and activity of matrix biomolecules.

Therapeutic Implications of microRNAs in Depressive Disorders: A Review

MicroRNAs are hidden players in complex psychophysical phenomena such as depression and anxiety related disorders though the activation and deactivation of multiple proteins in signaling cascades. Depression is classified as a mood disorder and described as feelings of sadness, loss, or anger that interfere with a person’s everyday activities. In this review, we have focused on exploration of the significant role of miRNAs in depression by affecting associated target proteins (cellular and synaptic) and their signaling pathways which can be controlled by the attachment of miRNAs at transcriptional and translational levels. Moreover, miRNAs have potential role as biomarkers and may help to cure depression through involvement and interactions with multiple pharmacological and physiological therapies. Taken together, miRNAs might be considered as promising novel therapy targets themselves and may interfere with currently available antidepressant treatments.

The microRNA-cell surface proteoglycan axis in cancer progression

Proteoglycans consist one of the major extracellular matrix class of biomolecules that demonstrate nodal roles in cancer progression. Μodern diagnostic and therapeutic approaches include proteoglycan detection and pharmacological targeting in various cancers. Proteoglycans orchestrate critical signaling pathways for cancer development and progression through dynamic interactions with matrix components. It is well established that the epigenetic signatures of cancer cells play critical role in guiding their functional properties and metastatic potential. Secreted microRNAs (miRNAs) reside in a complex network with matrix proteoglycans, thus affecting cell-cell and cell-matrix communication. This mini-review aims to highlight current knowledge on the proteoglycan-mediated signaling cascades that regulate miRNA biogenesis in cancer. Moreover, the miRNA-mediated proteoglycan regulation during cancer progression and mechanistic aspects on the way that proteoglycans affect miRNA expression are presented. Recent advances on the role of cell surface proteoglycans in exosome biogenesis and miRNA packaging and expression are also discussed.

MiRNA-29b and miRNA-497 Modulate the Expression of Carboxypeptidase X Member 2, a Candidate Gene Associated with Left Ventricular Hypertrophy

Left ventricular hypertrophy (LVH) is a major risk factor for adverse cardiovascular events. Recently, a novel candidate gene encoding the carboxypeptidase X member 2 (CPXM2) was found to be associated with hypertension-induced LVH. CPXM2 belongs to the M14 family of metallocarboxypeptidases, yet it lacks detectable enzyme activity, and its function remains unknown. Here, we investigated the impact of micro (mi)RNA-29b, miRNA-195, and miRNA-497 on the posttranscriptional expression control of CPXM2. Candidate miRNAs for CPXM2 expression control were identified in silico. CPXM2 expression in rat cardiomyocytes (H9C2) was characterized via real-time PCR, Western blotting, and immunofluorescence. Direct miRNA/target mRNA interaction was analysed by dual luciferase assay. CPXM2 was expressed in H9C2 and co-localised with z-disc associated protein PDZ and LIM domain 3 (Pdlim3). Transfection of H9C2 with miRNA-29b, miRNA-195, and miRNA-497 led to decreased levels of CPXM2 mRNA and protein, respectively. Results of dual luciferase assays revealed that miRNA-29b and miRNA-497, but not miRNA-195, directly regulated CPXM2 expression on a posttranscriptional level via binding to the 3′UTR of CPXM2 mRNA. We identified two miRNAs capable of the direct posttranscriptional expression control of CPXM2 expression in rat cardiomyocytes. This novel data may help to shed more light on the—so far—widely unexplored expression control of CPXM2 and its potential role in LVH.

Advances in Immunotherapy and the TGF-β Resistance Pathway in Metastatic Bladder Cancer

Simple Summary

Bladder cancer accounts for a significant burden to global public health. Despite advances in therapeutics with the advent of immunotherapy, only a small subset of patients benefit from immunotherapy. In this review, we examine the evidence that suggests that the TGF-β pathway may present a resistance mechanism to immunotherapy. In addition, we present possible therapies that may overcome the TGF-β resistance pathway in the treatment of bladder cancer.

Abstract

Bladder cancer accounts for nearly 200,000 deaths worldwide yearly. Urothelial carcinoma (UC) accounts for nearly 90% of cases of bladder cancer. Cisplatin-based chemotherapy has remained the mainstay of treatment in the first-line setting for locally advanced or metastatic UC. More recently, the treatment paradigm in the second-line setting was drastically altered with the approval of several immune checkpoint inhibitors (ICIs). Given that only a small subset of patients respond to ICI, further studies have been undertaken to understand potential resistance mechanisms to ICI. One potential resistance mechanism that has been identified in the setting of metastatic UC is the TGF-β signaling pathway. Several pre-clinical and ongoing clinical trials in multiple advanced tumor types have evaluated several therapies that target the TGF-β pathway. In addition, there are ongoing and planned clinical trials combining TGF-β inhibition with ICI, which may provide a promising therapeutic approach for patients with advanced and metastatic UC.

Extracellular vesicles derived from mesenchymal stromal cells mediate endogenous cell growth and migration via the CXCL5 and CXCL6/CXCR2 axes and repair menisci

Background

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) are promising candidates for tissue regeneration therapy. However, the therapeutic efficacy of MSC-EVs for meniscus regeneration is uncertain, and the mechanisms underlying MSC-EV-mediated tissue regeneration have not been fully elucidated. The aims of this study were to evaluate the therapeutic efficacy of intra-articular MSC-EV injection in a meniscus defect model and elucidate the mechanism underlying MSC-EV-mediated tissue regeneration via combined bioinformatic analyses.

Methods

MSC-EVs were isolated from human synovial MSC culture supernatants via ultrafiltration. To evaluate the meniscus regeneration ability, MSC-EVs were injected intra-articularly in the mouse meniscus defect model immediately after meniscus resection and weekly thereafter. After 1 and 3 weeks, their knees were excised for histological and immunohistochemical evaluations. To investigate the mechanisms through which MSC-EVs accelerate meniscus regeneration, cell growth, migration, and chondrogenesis assays were performed using treated and untreated chondrocytes and synovial MSCs with or without MSC-EVs. RNA sequencing assessed the gene expression profile of chondrocytes stimulated by MSC-EVs. Antagonists of the human chemokine CXCR2 receptor (SB265610) were used to determine the role of CXCR2 on chondrocyte cell growth and migration induced by MSC-EVs.

Results

In the meniscus defect model, MSC-EV injection accelerated meniscus regeneration and normalized the morphology and composition of the repaired tissue. MSC-EVs stimulated chondrocyte and synovial MSC cell growth and migration. RNA sequencing revealed that MSC-EVs induced 168 differentially expressed genes in the chondrocytes and significantly upregulated CXCL5 and CXCL6 in chondrocytes and synovial MSCs. Suppression of CXCL5 and CXCL6 and antagonism of the CXCR2 receptor binding CXCL5 and CXCL6 negated the influence of MSC-EVs on chondrocyte cell growth and migration.

Conclusions

Intra-articular MSC-EV administration repaired meniscus defects and augmented chondrocyte and synovial MSC cell growth and migration. Comprehensive transcriptome/RNA sequencing data confirmed that MSC-EVs upregulated CXCL5 and CXCL6 in chondrocytes and mediated the cell growth and migration of these cells via the CXCR2 axis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02481-9.

Serum miRNA Profiling for Early PDAC Diagnosis and Prognosis: A Retrospective Study

Background: Tumor stage predicts pancreatic cancer (PDAC) prognosis, but prolonged and short survivals have been described in patients with early-stage tumors. Circulating microRNA (miRNA) are an emerging class of suitable biomarkers for PDAC prognosis. Our aim was to identify whether serum miRNA signatures predict survival of early-stage PDAC. Methods: Serum RNA from archival 15 stage I-III PDAC patients and 4 controls was used for miRNAs expression profile (Agilent microarrays). PDAC patients with comparable age, gender, diabetes, jaundice and surgery were classified according to survival: less than 14 months (7/15 pts, group A) and more than 22 months (8/15 pts, group B). Bioinformatic data analysis was performed by two-class Significance Analysis of Microarray (SAM) algorithm. Binary logistic regression analyses considering PDAC diagnosis and outcome as dependent variables, and ROC analyses were also performed. Results: 2549 human miRNAs were screened out. At SAM, 76 differentially expressed miRNAs were found among controls and PDAC (FDR = 0.4%), the large majority (50/76, 66%) of them being downregulated in PDAC with respect to controls. Six miRNAs were independently correlated with early PDAC, and among these, hsa-miR-6821-5p was associated with the best ROC curve area in distinguishing controls from early PDAC. Among the 71 miRNAs differentially expressed between groups A and B, the most significant were hsa-miR-3135b expressed in group A only, hsa-miR-6126 and hsa-miR-486-5p expressed in group B only. Eight miRNAs were correlated with the presence of lymph-node metastases; among these, hsa-miR-4669 is of potential interest. hsa-miR-4516, increased in PDAC and found as an independent predictor of survival, has among its putative targets a series of gens involved in key pathways of cancer progression and dissemination, such as Wnt and p53 signalling pathways. Conclusions: A series of serum miRNAs was identified as potentially useful for the early diagnosis of PDAC, and for establishing a prognosis.

DGCR8-dependent efficient pri-miRNA processing of human pri-miR-9-2

Microprocessor complex, including DiGeorge syndrome critical region gene 8 (DGCR8) and DROSHA, recognizes and cleaves primary transcripts of microRNAs (pri-miRNAs) in the maturation of canonical miRNAs. The study of DGCR8 haploinsufficiency reveals that the efficiency of this activity varies for different miRNA species. It is thought that this variation might be associated with the risk of schizophrenia with 22q11 deletion syndrome caused by disruption of the DGCR8 gene. However, the underlying mechanism for varying action of DGCR8 with each miRNA remains largely unknown. Here, we used in vivo monitoring to measure the efficiency of DGCR8-dependent microprocessor activity in cultured cells. We confirmed that this system recapitulates the microprocessor activity of endogenous pri-miRNA with expression of a ratiometric fluorescence reporter. Using this system, we detected mir-9-2 as one of the most efficient targets. We also identified a novel DGCR8-responsive RNA element, which is highly conserved among mammalian species and could be regulated at the epi-transcriptome (RNA modification) level. This unique feature between DGCR8 and pri-miR-9-2 processing may suggest a link to the risk of schizophrenia.

The miRNA, miR-125b, Inhibited Invasion and Metastasis of Gastric-Cancer Cells by Triggering the STAT3 Signaling Pathway

OBJECTIVE

To investigate the function and the mechanism of miR-125b in the invasion and metastasis of gastric cancer and provide experimental basis for finding and developing new therapeutic strategies for gastric cancer.

METHODS

The difference of miR-125b expression in gastric cancer tissues and adjacent tissues was detected by qRT-PCR. The same test was performed in different gastric cancer cell lines. The effect of miR-125b on SGC-7901 and BGC-823 gastric cancer cell viability was examined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Transwell assay was used to detect the effect of miR-125b on invasion and metastasis of gastric cancer cells. The target gene STAT3 of miR-125b was identified and validated by dual luciferase reporter assay. Western blot assay and immunofluorescence staining were used to detect the effect of miR-125b on the expression and distribution of STAT3 protein. The inhibitor and activator of STAT3 were used to confirm the effect of STAT3 on invasion and metastasis of gastric cancer cells. Peritoneal metastasis experiment and IHC were used to study the inhibitory effect of miR-125b on the metastasis of gastric cancer in vivo.

RESULTS

The results of qRT-PCR showed that 125b expression was significantly lower in gastric cancer than in adjacent tissues, which indicated poor prognosis for gastric-cancer patients. Furthermore, two gastric-cancer cell lines, SGC-7901 and BGC-823, exhibited lower miR-125b levels than the normal cell line HEK293. After treatment with miR-125b mimics, cell proliferation was markedly inhibited. Meanwhile, the invasion and metastasis of gastric cancer cells were also inhibited after treated with miR-125b mimics. We also identified the signal transducer and activator of transcription 3 (STAT3) as a potential target of miR-125b based on patient data from The Cancer Genome Atlas (TCGA). Dual luciferase assays revealed that miR-125b directly inhibited STAT3 by binding to its 3'-untranslated region (UTR). Immunofluorescence assay showed that miR-125b could affect the subcellular distribution of STAT3. Moreover, treatment with miR-125b mimics or stattic inhibited invasion and migration in the gastric cancer cell lines, and IL-6 could reverse the inhibitory effect. Finally, nude mice xenografted with gastric-cancer cells expressing miR-125b mimics exhibited smaller tumors and lower transfer rates than mice engrafted with control group cells.

CONCLUSION

These data suggested that miR-125b inhibited invasion and metastasis in gastric cancer by inhibiting STAT3; therefore, miR-125b and STAT3 could be potential therapeutic targets in the treatment of gastric cancer.

Long non-coding RNAs and TGF-β signaling in cancer

Cancer is driven by genetic mutations in oncogenes and tumor suppressor genes and by cellular events that develop a misregulated molecular microenvironment in the growing tumor tissue. The tumor microenvironment is guided by the excessive action of specific cytokines including transforming growth factor-β (TGF-β), which normally controls embryonic development and the homeostasis of young or adult tissues. As a consequence of the genetic alterations generating a given tumor, TGF-β can preserve its homeostatic function and attempt to limit neoplastic expansion, whereas, once the tumor has progressed to an aggressive stage, TGF-β can synergize with various oncogenic stimuli to facilitate tumor invasiveness and metastasis. TGF-β signaling mechanisms via Smad proteins, various ubiquitin ligases, and protein kinases are relatively well understood. Such mechanisms regulate the expression of genes encoding proteins or non-coding RNAs. Among non-coding RNAs, much has been understood regarding the regulation and function of microRNAs, whereas the role of long non-coding RNAs is still emerging. This article emphasizes TGF-β signaling mechanisms leading to the regulation of non-coding genes, the function of such non-coding RNAs as regulators of TGF-β signaling, and the contribution of these mechanisms in specific hallmarks of cancer.

Deregulation of Drosha in the pathogenesis of hereditary hemorrhagic telangiectasia

PURPOSE OF REVIEW

The TGFβ (transforming growth factor β) superfamily - a large group of structurally related and evolutionarily conserved proteins - profoundly shapes and organizes the vasculature during normal development and adult homeostasis. Mutations inactivating several of its ligands, receptors, or signal transducers set off hereditary hemorrhagic telangiectasia (HHT), a disorder that causes capillary networks to form incorrectly. Drosha, an essential microRNA-processing enzyme, also interfaces with TGFβ signal transducers, but its involvement in vascular conditions had not been tested until recently. This review summarizes current evidence that links mutations of Drosha to HHT.

RECENT FINDINGS

Genetic studies have revealed that rare missense mutations in the Drosha gene occur more commonly among HHT patients than in healthy people. Molecular analyses also indicated that Drosha enzymes with HHT-associated mutations generate microRNAs less efficiently than their wild-type counterpart when stimulated by TGFβ ligands. In zebrafish or mouse, mutant Drosha proteins cause the formation of dilated, leaky blood vessels deprived of capillaries, similar to those typically found in patients with HHT.

SUMMARY

Recent evidence suggests that Drosha-mediated microRNA biogenesis contributes significantly to the control of vascular development and homeostasis by TGFβ. Loss or reduction of Drosha function may predispose carriers to HHT and possibly other vascular diseases.

Effects of Pseudomonas aeruginosa on Microglial-Derived Extracellular Vesicle Biogenesis and Composition

The packaging of molecular constituents inside extracellular vesicles (EVs) allows them to participate in intercellular communication and the transfer of biological molecules, however the role of EVs during bacterial infection is poorly understood. The goal of this study was to examine the effects of Pseudomonas aeruginosa (P. aeruginosa) infection on the biogenesis and composition of EVs derived from the mouse microglia cell line, BV-2. BV-2 cells were cultured in exosome-free media and infected with 0, 1.3 × 10⁴, or 2.6 × 10⁴ colony forming units per milliliter P. aeruginosa for 72 h. The results indicated that compared with the control group, BV-2 cell viability significantly decreased after P. aeruginosa infection and BV-2-derived EVs concentration decreased significantly in the P. aeruginosa-infected group. P. aeruginosa infection significantly decreased chemokine ligand 4 messenger RNA in BV-2-derived infected EVs, compared with the control group (p ≤ 0.05). This study also revealed that heat shock protein 70 (p ≤ 0.05) and heat shock protein 90β (p ≤ 0.001) levels of expression within EVs increased after P. aeruginosa infection. EV treatment with EVs derived from P. aeruginosa infection reduced cell viability of BV-2 cells. P. aeruginosa infection alters the expression of specific proteins and mRNA in EVs. Our study suggests that P. aeruginosa infection modulates EV biogenesis and composition, which may influence bacterial pathogenesis and infection.

The Role of TGF-β Signaling Regulatory MicroRNAs in the Pathogenesis of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common cancers globally and is associated with a high mortality rate. The transforming growth factor beta (TGF-β) signaling pathway plays an important role in normal intestinal tissue function, but has also been implicated in the development of CRC. MicroRNAs (miRNAs) have also recently emerged as important regulators of cancer development and progression. They act by targeting multiple signaling pathways including the TGF-β signaling pathway. There is growing evidence demonstrating that miRNAs target various components of the TGF-β signaling pathway, including TGF-β1, TGF-β2, regulatory SMADs (SMAD1, 2, 3, 5 and 9), co-mediator SMAD4, inhibitory SMADs (SMAD6 and 7) and the TGF-β receptors, and thereby alter the proliferation and migration of CRC cells. In this review, we summarize the data concerning the interaction between TGF-β signaling pathway and miRNAs with the aim to better understanding the CRC molecular mechanisms and hence better management of this disease.

Gld2 activity is regulated by phosphorylation in the N-terminal domain

The de-regulation of microRNAs (miRNAs) is associated with multiple human diseases, yet cellular mechanisms governing miRNA abundance remain largely elusive. Human miR-122 is required for Hepatitis C proliferation, and low miR-122 abundance is associated with hepatic cancer. The adenylyltransferase Gld2 catalyses the post-transcriptional addition of a single adenine residue (A + 1) to the 3'-end of miR-122, enhancing its stability. Gld2 activity is inhibited by binding to the Hepatitis C virus core protein during HepC infection, but no other mechanisms of Gld2 regulation are known. We found that Gld2 activity is regulated by site-specific phosphorylation in its disordered N-terminal domain. We identified two phosphorylation sites (S62, S110) where phosphomimetic substitutions increased Gld2 activity and one site (S116) that markedly reduced activity. Using mass spectrometry, we confirmed that HEK 293 cells readily phosphorylate the N-terminus of Gld2. We identified protein kinase A (PKA) and protein kinase B (Akt1) as the kinases that site-specifically phosphorylate Gld2 at S116, abolishing Gld2-mediated nucleotide addition. The data demonstrate a novel phosphorylation-dependent mechanism to regulate Gld2 activity, revealing tumour suppressor miRNAs as a previously unknown target of Akt1-dependent signalling.

MicroRNA in Ovarian Cancer: Biology, Pathogenesis, and Therapeutic Opportunities

Ovarian cancer comprises one of the three major malignant tumor types in the female reproductive system. The mortality rate of this cancer is the highest among all gynecological tumors, with ovarian cancer metastasis constituting an important cause of death. Therefore, markers for disease prediction and prognosis are highly desirable for early diagnosis as well as for helping optimize and personalize treatment. Recently, microRNAs (miRNAs), which consist of short-sequence RNAs that do not encode a protein, have emerged as new biomarkers in the clinical diagnosis and treatment of ovarian cancer. By pairing with bases specific to the target messenger RNA (mRNA), miRNAs cause degradation of the target mRNA or inhibit its translation, thereby regulating various cellular processes including cell proliferation and adhesion. Increasing numbers of studies have shown that miRNA expression abnormality plays an important role in the development of ovarian cancer. In this review, we discuss the mechanisms of miRNA action, current research regarding their role in the suppression or promotion of ovarian cancer, and their use as markers for diagnosis of prognosis or as therapeutic targets for this disease. Finally, we present future perspectives regarding the clinical management of ovarian cancer and the role for miRNAs therein.

Epstein-Barr Virus and miRNAs: Partners in Crime in the Pathogenesis of Multiple Sclerosis?

MicroRNAs (miRNAs) are small non-coding RNAs that modulate gene expression post transcriptionally. In healthy individuals, miRNAs contribute to maintaining gene expression homeostasis. However, the level of miRNAs expressed is markedly altered in different diseases, including multiple sclerosis (MS). The impact of such changes is being investigated, and thought to shape the immune system into the inflammatory autoimmune phenotype. Much is yet to be learned about the contribution of miRNAs in the molecular pathology of MS. Epstein-Barr virus (EBV) infection is a major risk factor for the development of MS. EBV encodes more than 40 miRNAs, most of which have been studied in the context of EBV associated cancers. These viral miRNAs regulate genes involved in cell apoptosis, antigen presentation and recognition, as well as B cell transformation. If EBV infection contributes to the pathology of MS, it is plausible that EBV miRNAs may be involved. Unfortunately, there are limited studies addressing how EBV miRNAs are involved in the pathogenesis of MS. This review summarizes what has been reported regarding cellular and viral miRNA profiles in MS and proposes possible interactions between the two in the development of MS.

Reticuloendotheliosis virus and avian leukosis virus subgroup J synergistically increase the accumulation of exosomal miRNAs

BACKGROUND

Co-infection with avian leukosis virus subgroup J and reticuloendotheliosis virus induces synergistic pathogenic effects and increases mortality. However, the role of exosomal miRNAs in the molecular mechanism of the synergistic infection of the two viruses remains unknown.

RESULTS

In this study, exosomal RNAs from CEF cells infected with ALV-J, REV or both at the optimal synergistic infection time were analysed by Illumina RNA deep sequencing. A total of 54 (23 upregulated and 31 downregulated) and 16 (7 upregulated and 9 downregulated) miRNAs were identified by comparing co-infection with two viruses, single-infected ALV-J and REV, respectively. Moreover, five key miRNAs, including miR-184-3p, miR-146a-3p, miR-146a-5p, miR-3538 and miR-155, were validated in both exosomes and CEF cells by qRT-PCR. GO annotation and KEGG pathway analysis of the miRNA target genes showed that the five differentially expressed miRNAs participated in virus-vector interaction, oxidative phosphorylation, energy metabolism and cell growth.

CONCLUSIONS

We demonstrated that REV and ALV-J synergistically increased the accumulation of exosomal miRNAs, which sheds light on the synergistic molecular mechanism of ALV-J and REV.

Regulation of primary microRNA processing

MicroRNAs (miRNAs) are evolutionarily conserved small regulatory RNAs that participate in the adjustment of many, if not all, fundamental biological processes. Molecular mechanisms involved in miRNA biogenesis and mode of action have been elucidated in the past two decades. Similar to many cellular pathways, miRNA processing and function can be globally or specifically regulated at several levels and by numerous proteins and RNAs. Given their role as fine-tuning molecules, it is essential for miRNA expression to be tightly regulated in order to maintain cellular homeostasis. Here, we review our current knowledge of the first step of their maturation occurring in the nucleus and how it can be specifically and dynamically modulated.

MALAT1 affects ovarian cancer cell behavior and patient survival

Epithelial ovarian cancer (EOC) is one of the most lethal malignancies of the female reproductive organs. Increasing evidence has revealed that long non-coding RNAs (lncRNAs) participate in tumorigenesis. Metastasis associated lung adenocarcinoma transcript 1 (MALAT1) is an lncRNA and plays a role in various types of tumors. However, the function of MALAT1 on cellular behavior in EOC remains unclear. The current study explored the expression of MALAT1 in ovarian cancer tissues and in EOC cell lines. Quantitative RT-PCR analysis revealed that the expression of MALAT1 was higher in human ovarian malignant tumor tissues and EOC cells than in normal ovarian tissues and non-tumorous human ovarian surface epithelial cells, respectively. By analyzing the online database Kaplan-Meier Plotter, MALAT1 was identified to be correlated with the overall survival (OS) and progression-free survival (PFS) of patients with ovarian cancer. Furthermore, knockdown of MALAT1 by small interfering RNA (siRNA) significantly decreased EOC cell viability, migration, and invasion. Finally, dual-luciferase reporter assays demonstrated that MALAT1 interacted with miR-143-3p, a miRNA that plays a role in EOC as demonstrated in our previous study. Inhibition of MALAT1 resulted in an increase of miR-143-3p expression, leading to a decrease of CMPK protein expression. In conclusion, our results indicated that MALAT1 was overexpressed in EOC. Silencing of MALAT1 decreased EOC cell viability and inhibited EOC cell migration and invasion. These data revealed that MALAT1 may serve as a new therapeutic target of human EOC.

microRNAs in skeletal muscle development

A fundamental process during both embryo development and stem cell differentiation is the control of cell lineage determination. In developing skeletal muscle, many of the diffusible signaling molecules, transcription factors and more recently non-coding RNAs that contribute to this process have been identified. This has facilitated advances in our understanding of the molecular mechanisms underlying the control of cell fate choice. Here we will review the role of non-coding RNAs, in particular microRNAs (miRNAs), in embryonic muscle development and differentiation, and in satellite cells of adult muscle, which are essential for muscle growth and regeneration. Some of these short post-transcriptional regulators of gene expression are restricted to skeletal muscle, but their expression can also be more widespread. In addition, we discuss a few examples of long non-coding RNAs, which are numerous but much less well understood.

Inhibition of microRNA‑155 ameliorates cardiac fibrosis in the process of angiotensin II‑induced cardiac remodeling

Cardiac fibrosis triggered by pressure overload represents one of the major challenges in the treatment of cardiovascular diseases. MicroRNA (miRNA/miR)-155, a member of the small RNA family, has previously been demonstrated to be associated with cardiac inflammation. However, the effect of miR-155 on cardiac fibrosis induced by angiotensin II (Ang II), particularly in cardiac fibroblasts, requires further investigation. The present study aimed to investigate the effect of miR-155 in Ang II-induced cardiac fibrosis using animal models and cardiac fibroblasts. Animal models were established in male miR-155^−/− and wild-type (WT) C57Bl/6J mice (10–12 weeks old) by Ang II infusion using subcutaneously implanted minipumps. After 8 weeks of Ang II infusion, the results demonstrated that the deletion of miR-155 in mice markedly ameliorated ventricular remodeling compared with WT mice, as demonstrated by restricted inflammatory responses, decreased heart size, improved cardiac function and reduced myocardial fibrosis. In vitro, overexpression of miR-155 in cardiac fibroblasts led to significantly increased fibroblast to myofibroblast transformation. However, this effect was abrogated by miR-155 silencing. In conclusion, the results of the present study indicate that genetic loss of miR-155 in mice ameliorates cardiac fibrotic remodeling following pressure overload. Therefore, inhibiting miR-155 may have potential as an adjunct to reduce cardiac inflammation in the treatment of cardiac fibrosis.

Non-coding RNAs Enabling Prognostic Stratification and Prediction of Therapeutic Response in Colorectal Cancer Patients

Colorectal cancer (CRC) is a heterogeneous disease and current treatment options for patients are associated with a wide range of outcomes and tumor responses. Although the traditional TNM staging system continues to serve as a crucial tool for estimating CRC prognosis and for stratification of treatment choices and long-term survival, it remains limited as it relies on macroscopic features and cases of surgical resection, fails to incorporate new molecular data and information, and cannot perfectly predict the variety of outcomes and responses to treatment associated with tumors of the same stage. Although additional histopathologic features have recently been applied in order to better classify individual tumors, the future might incorporate the use of novel molecular and genetic markers in order to maximize therapeutic outcome and to provide accurate prognosis. Such novel biomarkers, in addition to individual patient tumor phenotyping and other validated genetic markers, could facilitate the prediction of risk of progression in CRC patients and help assess overall survival. Recent findings point to the emerging role of non-protein-coding regions of the genome in their contribution to the progression of cancer and tumor formation. Two major subclasses of non-coding RNAs (ncRNAs), microRNAs and long non-coding RNAs, are often dysregulated in CRC and have demonstrated their diagnostic and prognostic potential as biomarkers. These ncRNAs are promising molecular classifiers and could assist in the stratification of patients into appropriate risk groups to guide therapeutic decisions and their expression patterns could help determine prognosis and predict therapeutic options in CRC.

miR-551b regulates epithelial-mesenchymal transition and metastasis of gastric cancer by inhibiting ERBB4 expression

Epithelial-mesenchymal transition (EMT) is an important biological process that is characteristic of malignant tumor cells with metastatic potential. We investigated the role of miR-551b in EMT and metastasis in gastric cancer (GC). We found that low miR-551b levels were associated with EMT, metastasis and a poor prognosis in GC patients. Further, two GC cell lines, MNK45 and SGC7901, exhibited lower miR-551b levels than the GES normal stomach cell line. Exposing MNK45 and SGC7901 cells to TGF-β1 resulted in cell morphology changes characteristic of EMT, which was confirmed by Western blot analysis demonstrating low E-Cadherin and high N-Cadherin and Vimentin levels. Treatment with miR-551b mimics inhibited these EMT changes as well as Transwell migration and invasiveness. We identified ERBB4 as a potential target of miR-551b based on patient data from the TCGA. ERBB4 was upregulated in GC specimens, and its high expression correlated with a poor prognosis of GC patients. Dual luciferase assays revealed that miR-551b directly inhibited ERBB4 by binding to its 3'UTR. Moreover, treatment with miR-551b mimics or the ERBB4 inhibitor AST-1306 inhibited EMT in the GC cell lines. Finally, nude mice xenografted with GC cancer cell lines expressing miR-551b mimics exhibited smaller tumors and longer survival than mice engrafted with control GC cancer cells. These data indicate that miR-551b inhibits EMT and metastasis in GC by inhibiting ERBB4. miR-551b and ERBB4 are thus potential therapeutic targets for the treatment of GC.

Tumor-associated myoepithelial cells promote the invasive progression of ductal carcinoma in situ through activation of TGFβ signaling

The normal myoepithelium has a tumor-suppressing nature and inhibits the progression of ductal carcinoma in situ (DCIS) into invasive ductal carcinoma (IDC). Conversely, a growing number of studies have shown that tumor-associated myoepithelial cells have a tumor-promoting effect. Moreover, the exact role of tumor-associated myoepithelial cells in the DCIS-to-IDC development remains undefined. To address this, we explored the role of tumor-associated myoepithelial cells in the DCIS-to-IDC progression. We developed a direct coculture system to study the cell-cell interactions between DCIS cells and tumor-associated myoepithelial cells. Coculture studies indicated that tumor-associated myoepithelial cells promoted the invasive progression of a DCIS cell model in vitro, and mechanistic studies revealed that the interaction with DCIS cells stimulated tumor-associated myoepithelial cells to secrete TGFβ1, which subsequently contributed to activating the TGFβ/Smads pathway in DCIS cells. We noted that activation of the TGFβ signaling pathway promoted the epithelial-mesenchymal transition, basal-like phenotypes, stemness, and invasiveness of DCIS cells. Importantly, xenograft studies further demonstrated that tumor-associated myoepithelial cells enhanced the DCIS-to-IDC progression in vivo Furthermore, we found that TGFβ-mediated induction of oncogenic miR-10b-5p expression and down-regulation of RB1CC1, a miR-10b-5p-targeted tumor-suppressor gene, contributed to the invasive progression of DCIS. Our findings provide the first experimental evidence to directly support the paradigm that altered DCIS-associated myoepithelial cells promote the invasive progression of DCIS into IDC via TGFβ signaling activation.

Bone morphogenetic protein 4 regulates microRNAs miR-494 and miR-126-5p in control of endothelial cell function in angiogenesis

MicroRNAs are small non-coding RNAs that negatively regulate posttranscriptional gene expression. Several microRNAs have been described to regulate the process of angiogenesis. Previously, we have shown that bone morphogenetic protein 4 (BMP4) increased the pro-angiogenic activity of endothelial cells. In this project, we now investigated how the pro-angiogenic BMP4 effect is mediated by microRNAs. First, we performed a microRNA array with BMP4-stimulated human umbilical vein endothelial cells (HUVECs). Among the top-regulated microRNAs, we detected a decreased expression of miR-494 and increased expression of miR-126-5p. Next, we analysed the canonical Smad and alternative signalling pathways, through which BMP4 would regulate miR-126-5p and miR-494 expression. Furthermore, the functional effect of miR-494 and miR-126-5p on endothelial cells was investigated. MicroRNA-494 overexpression decreased endothelial cell proliferation, migration and sprout formation. Consistently, miR-494 inhibition increased endothelial cell function. As potential miR-494 targets, bFGF and BMP endothelial cell precursor-derived regulator (BMPER) were identified and confirmed by western blot. Luciferase assays showed direct miR-494 binding in BMPER 3'UTR. In contrast, miR-126-5p overexpression increased pro-angiogenic endothelial cell behaviour and, accordingly, miR-126-5p inhibition decreased endothelial cell function. As a direct miR-126-5p target we identified the anti-angiogenic thrombospondin-1 which was confirmed by western blot analysis and luciferase assays. In the Matrigel plug assay application of antagomiR-494 increased endothelial cell ingrowth, whereas antagomiR-126-5p treatment decreased cell ingrowth in vivo. Taken together, through differential regulation of the anti-angiomiR-494 and the angiomiR-126-5p by BMP4 both microRNAs contribute to the pro-angiogenic BMP4 effect on endothelial cells.

Regulation of miRNAs by herbal medicine: An emerging field in cancer therapies

MicroRNAs' expression profiles have recently gained major attention as far as cancer research is concerned. MicroRNAs are able to inhibit target gene expression via binding to the 3' UTR of target mRNA, resulting in target mRNA cleavage or translation inhibition. MicroRNAs play significant parts in a myriad of biological processes; studies have proven, on the other hand, that aberrant microRNA expression is, more often than not, associated with the growth and progression of cancers. MicroRNAs could act as oncogenes (oncomir) or tumor suppressors and can also be utilized as biomarkers for diagnosis, prognosis, and cancer therapy. Recent studies have shown that such herbal extracts as Shikonin, Sinomenium acutum, curcumin, Olea europaea, ginseng, and Coptidis Rhizoma could alter microRNA expression profiles through inhibiting cancer cell development, activating the apoptosis pathway, or increasing the efficacy of conventional cancer therapeutics. Such findings patently suggest that the novel specific targeting of microRNAs by herbal extracts could complete the restriction of tumors by killing the cancerous cells so as to recover survival results in patients diagnosed with malignancies. In this review, we summarized the current research about microRNA biogenesis, microRNAs in cancer, herbal compounds with anti-cancer effects and novel strategies for employing herbal extracts in order to target microRNAs for a better treatment of patients diagnosed with cancer.

TGF-β Signaling from Receptors to Smads

Transforming growth factor β (TGF-β) and related growth factors are secreted pleiotropic factors that play critical roles in embryogenesis and adult tissue homeostasis by regulating cell proliferation, differentiation, death, and migration. The TGF-β family members signal via heteromeric complexes of type I and type II receptors, which activate members of the Smad family of signal transducers. The main attribute of the TGF-β signaling pathway is context-dependence. Depending on the concentration and type of ligand, target tissue, and developmental stage, TGF-β family members transmit distinct signals. Deregulation of TGF-β signaling contributes to developmental defects and human diseases. More than a decade of studies have revealed the framework by which TGF-βs encode a context-dependent signal, which includes various positive and negative modifiers of the principal elements of the signaling pathway, the receptors, and the Smad proteins. In this review, we first introduce some basic components of the TGF-β signaling pathways and their actions, and then discuss posttranslational modifications and modulatory partners that modify the outcome of the signaling and contribute to its context-dependence, including small noncoding RNAs.

Vaspin regulates the osteogenic differentiation of MC3T3-E1 through the PI3K-Akt/miR-34c loop

Vaspin (visceral adipose tissue-derived serine protease inhibitor) is a newly discovered adipokine that widely participates in diabetes mellitus, polycystic ovarian syndrome and other disorders of metabolism. However, the effect of vaspin on the regulation of osteogenesis and the mechanism responsible are still unclear. Here, we found that vaspin can attenuate the osteogenic differentiation of the preosteoblast cell line MC3T3-E1 in a dose-dependent way; also, during this process, the expression of miRNA-34c (miR-34c) was significantly increased. Down-regulation of the expression of miR-34c in MC3T3-E1 diminished the osteogenic inhibitory effect of vaspin, while the up-regulation of miR-34c increased this effect through its target gene Runx2. Meanwhile, we found that vaspin could also activate the PI3K-Akt signalling pathway. Blocking the PI3K-Akt signalling pathway with specific inhibitors could decrease the osteogenic inhibitory effect of vaspin as well as the expression level of miR-34c. Furthermore, knock-down of miR-34c could promote the activation of Akt, which was probably realised by targeting c-met expression. Thus, PI3K-Akt and miR-34c constituted a modulation loop and controlled the expression of each other. Taken together, our study showed that vaspin could inhibit the osteogenic differentiation in vitro, and the PI3K-Akt/miR-34c loop might be the underlying mechanism.

TGF-β and the TGF-β Family: Context-Dependent Roles in Cell and Tissue Physiology

The transforming growth factor-β (TGF-β) is the prototype of the TGF-β family of growth and differentiation factors, which is encoded by 33 genes in mammals and comprises homo- and heterodimers. This review introduces the reader to the TGF-β family with its complexity of names and biological activities. It also introduces TGF-β as the best-studied factor among the TGF-β family proteins, with its diversity of roles in the control of cell proliferation and differentiation, wound healing and immune system, and its key roles in pathology, for example, skeletal diseases, fibrosis, and cancer.

Exploration of the regulatory effect of miR-21 on breast cancer cell line proliferation and invasion as well as the downstream target genes

OBJECTIVE

To study the regulatory effects of miR-21 on breast cancer cell line proliferation and invasion as well as the downstream target genes.

METHODS

Breast cancer cell lines MCF-7 were cultured and transfected with miR-21 mimics and the corresponding negative control mimics (NC mimics), and then MTS kits were used to detect cell viability. Transwell experiment was used to detect cell invasion ability, and fluorescence quantitative PCR was used to detect the expression of proliferation and invasion-related genes in cells.

RESULTS

24 h after transfection of miR-21 mimics and NC mimics, cell OD value and the number of invasive cells of miR-21 group were significantly higher than those of NC group, and mRNA contents of PDCD-4, FasL, PTEN, RhoB, Maspin, TIMP3 and RECK in cells were significantly lower than those of NC group.

CONCLUSION

miR-21 can promote the proliferation and invasion of breast cancer cell lines, and its downstream target genes include PDCD-4, FasL, PTEN, RhoB, Maspin, TIMP3 and RECK.

The feedback loop between miR-124 and TGF-β pathway plays a significant role in non-small cell lung cancer metastasis

Increasing evidence shows that micro RNAs (miRNAs) play a critical role in tumor development. However, the role of miRNAs in non-small cell lung cancer (NSCLC) metastasis remains largely unknown. Here, we found that miR-124 expression was significantly impaired in NSCLC tissues and associated with its metastasis. In vitro and in vivo experiments indicate that restoring miR-124 expression in NSCLC cells had a marked effect on reducing cell migration, invasion and metastasis. Mechanistic analyses show that Smad4, a cobinding protein in transforming growth factor-β (TGF-β) pathway, was identified as a new target gene of miR-124. Restoring Smad4 expression in miR-124-infected cells could partially rescue miR-124-induced abolition of cell migration and invasion. Notably, upon TGF-β stimulation, phosphorylation of Smad2/3 was modulated by alteration of miR-124 or Smad4 expression, followed by inducing some special transcription of downstream genes including Snail, Slug and ZEB2, all of which may trigger epithelial-mesenchymal transition and be associated with NSCLC metastasis. Moreover, activation of TGF-β pathway may enhance expression of DNMT3a, leading to hypermethylation on miR-124 promoter. Therefore, heavily loss of miR-124 expression further enhances Smad4 level by this feedback loop. Taken together, our data show for the first time that the feedback loop between miR-124 and TGF-β pathway may play a significant role in NSCLC metastasis. Targeting the loop may prove beneficial to prevent metastasis and provide a more effective therapeutic strategy for NSCLC.

Mutation screening of MIR146A/B and BRCA1/2 3'-UTRs in the GENESIS study

Although a wide number of breast cancer susceptibility alleles associated with various levels of risk have been identified to date, about 50% of the heritability is still missing. Although the major BRCA1 and BRCA2 genes are being extensively screened for truncating and missense variants in breast and/or ovarian cancer families, potential regulatory variants affecting their expression remain largely unexplored. In an attempt to identify such variants, we focused our attention on gene regulation mediated by microRNAs (miRs). We screened two genes, MIR146A and MIR146B, producing miR-146a and miR-146b-5p, respectively, that regulate BRCA1, and the 3'- untranslated regions (3'-UTRs) of BRCA1 and BRCA2 in the GENESIS French national case/control study (BRCA1- and BRCA2-negative breast cancer cases with at least one sister with breast cancer and matched controls). We identified one rare variant in MIR146A, four in MIR146B, five in BRCA1 3'-UTR and one in BRCA2 3'-UTR in 716 index cases and 619 controls. Among these 11 rare variants, 7 were identified each in 1 index case. None of the three relevant MIR146A/MIR146B variants affected the pre-miR sequences. The potential causality of the four relevant BRCA1/BRCA2 3'-UTRs variants was evaluated with luciferase reporter assays and co-segregation studies, as well as with bioinformatics analyses to predict miRs-binding sites, RNA secondary structures and RNA accessibility. This is the first study to report the screening of miR genes and of BRCA2 3'-UTR in a large series of familial breast cancer cases. None of the variant identified in this study gave convincing evidence of potential pathogenicity.

Enhancing adoptive T cell immunotherapy with microRNA therapeutics

Adoptive T cell-based immunotherapies can mediate complete and durable regressions in patients with advanced cancer, but current response rates remain inadequate. Maneuvers to improve the fitness and antitumor efficacy of transferred T cells have been under extensive exploration in the field. Small non-coding microRNAs have emerged as critical modulators of immune system homeostasis and T cell immunity. Here, we summarize recent advances in our understanding of the role of microRNAs in regulating T cell activation, differentiation, and function. We also discuss how microRNA therapeutics could be employed to fine-tune T cell receptor signaling and enhance T cell persistence and effector functions, paving the way for the next generation of adoptive immunotherapies.

Down-regulation of miR-135b in colon adenocarcinoma induced by a TGF-β receptor I kinase inhibitor (SD-208)

OBJECTIVES

Transforming growth factor-β (TGF-β) is involved in colorectal cancer (CRC). The SD-208 acts as an anti-cancer agent in different malignancies via TGF-β signaling. This work aims to show the effect of manipulation of TGF-β signaling on some miRNAs implicated in CRC.

MATERIALS AND METHODS

We investigated the effects of SD-208 on SW-48, a colon adenocarcinoma cell line. The cell line was treated with 0.5, 1 and 2 μM concentrations of SD-208. Then, the xenograft model of colon cancer was established by subcutaneous inoculation of SW-48 cell line into the nude mice. The animals were treated with SD-208 for three weeks. A quantitative real-time PCR was carried out for expression level analysis of selected oncogenic (miR-21, 31, 20a and 135b) and suppressor-miRNAs (let7-g, miR-133b, 145 and 200c). Data were analyzed using the 2-∆∆CT method through student's t-test via the GraphPad Prism software.

RESULTS

Our results revealed that SD-208 could significantly down-regulate the expression of one key onco-miRNA, miR-135b, in either SW-48 colon cells (P=0.006) or tumors orthotopically implanted in nude mice (P=0.018). Our in silico study also predicted that SD-208 could modulate the expression of potential downstream tumor suppressor targets of the miR135b.

CONCLUSION

Our data provide novel evidence that anticancer effects of SD-208 (and likely other TGF-β inhibitors) may be owing to their ability to regulate miRNAs expression.

Identification of miRNomes in human stomach and gastric carcinoma reveals miR-133b/a-3p as therapeutic target for gastric cancer

Gastric cancer (GC) is the fourth most frequent malignant disease and the second leading cause of cancer mortality worldwide, but the molecular mechanisms underlying this clinically heterogeneous disease are complex and remain far from completely understood. Accumulating evidence suggests that abnormal microRNA (miRNA) expression is involved in tumorigenesis. However, their accurate expression pattern, function, and mechanism in GC remain unclear. Here, a heatmap analysis of the miRNomes was performed across TCGA datasets and the expression of miR-133 family was found to be consistently downregulated in GC. This result was confirmed in two GC cell lines and 20 pairs of primary GC tissues, and further study demonstrated that the downregulation of miR-133 was mainly mediated by histone modification within its promoter region. Importantly, restoration of miR-133b/a-3p expression could suppress GC cell proliferation and promote cell apoptosis by targeting anti-apoptotic molecules Mcl-1 and Bcl-xL. Consistent with in vitro results, reintroducing of miR-133b/a-3p expression significantly delayed tumor formation and reduced tumor size of GC cells in xenograft nude mice. And the inverse relationship between miR-133b/a-3p and its targets was verified in xenograft mice. Taken together, our findings suggest that miR-133b/a-3p acts as a tumor suppressor in GC by directly targeting Mcl-1 and Bcl-xL. Revealing novel mechanism for oncogene inhibition by miRNA-mediated pathways offers new avenues for GC treatment.

[MicroRNAs in kidney fibrosis]

Renal fibrosis represents the final stage of most chronic kidney diseases and contributes to the progressive and irreversible decline in kidney function with accumulation of extracellular matrix components in the renal parenchyma. The molecular mechanisms governing the renal fibrosis process are complex and remain poorly understood. Recently, the profibrotic role of several microRNAs (miRNAs) has been described in kidney fibrosis. MiRNAs are a new class of, small non-coding RNAs of about 20 nucleotides that act as gene expression negative regulators at the post-transcriptional level. Seminal studies have highlighted the potential importance of miRNA as new therapeutic targets and innovative diagnostic and/or prognostic biomarkers. This review summarizes recent scientific advances on the role played by miRNAs in kidney fibrogenesis and discusses potential clinical applications as well as future research directions.

Therapeutic Opportunities for Targeting microRNAs in Cancer

MicroRNAs (miRNAs) are small noncoding RNAs that can function as either powerful tumor promoters or suppressors in numerous types of cancer. The ability of miRs to target multiple genes and biological signaling pathways has created intense interest in their potential clinical utility as predictive and diagnostic biomarkers, and as innovative therapeutic agents. Recently, accumulating preclinical studies have illustrated the feasibility of slowing tumor progression by either overexpressing tumor suppressive miRNAs, or by neutralizing the activities of oncogenic miRNAs in cell- and animal-based models of cancer. Here we highlight prominent miRNAs that may represent potential therapeutic targets in human malignancies, as well as review current technologies available for inactivating or restoring miRNA activity in clinical settings.

Expression of DROSHA in the Uterus of Mice in Early Pregnancy and Its Potential Significance During Embryo Implantation

Previous studies have shown that microRNAs are involved in the process of implantation. They play an important role in cell growth and proliferation. DROSHA is the microRNA-processing enzyme and is required for the maturation of microRNAs. However, its expression and function during early pregnancy in mice still remain unclear. In the present study, we analyzed the expression pattern of DROSHA in the mouse uterus during early pregnancy, pseudopregnancy, artificially induced decidualization, and in the ovariectomized mouse uterus using real-time quantitative polymerase chain reaction, Western blotting analyses, and immunohistochemistry. We found that DROSHA was spatiotemporally expressed in decidualizing stromal cells during early pregnancy and in pseudopregnant mice in which decidualization was artificially induced. In the ovariectomized mouse uterus, the expression of DROSHA was upregulated after progesterone treatment. In a stromal cell culture model, the expression of DROSHA gradually increased with the progression of stromal decidualization. Taken together, our findings suggest that DROSHA is involved in stromal decidualization and may play an important role in embryo implantation in mice.

p-SMAD2/3 and DICER promote pre-miR-21 processing during pressure overload-associated myocardial remodeling

Transforming growth factor-β (TGF-β) induces miR-21 expression which contributes to fibrotic events in the left ventricle (LV) under pressure overload. SMAD effectors of TGF-β signaling interact with DROSHA to promote primary miR-21 processing into precursor miR-21 (pre-miR-21). We hypothesize that p-SMAD-2 and -3 also interact with DICER1 to regulate the processing of pre-miR-21 to mature miR-21 in cardiac fibroblasts under experimental and clinical pressure overload. The subjects of the study were mice undergoing transverse aortic constriction (TAC) and patients with aortic stenosis (AS). In vitro, NIH-3T3 fibroblasts transfected with pre-miR-21 responded to TGF-β1 stimulation by overexpressing miR-21. Overexpression and silencing of SMAD2/3 resulted in higher and lower production of mature miR-21, respectively. DICER1 co-precipitated along with SMAD2/3 and both proteins were up-regulated in the LV from TAC-mice. Pre-miR-21 was isolated bound to the DICER1 maturation complex. Immunofluorescence analysis revealed co-localization of p-SMAD2/3 and DICER1 in NIH-3T3 and mouse cardiac fibroblasts. DICER1-p-SMAD2/3 protein-protein interaction was confirmed by in situ proximity ligation assay. Myocardial up-regulation of DICER1 constituted a response to pressure overload in TAC-mice. DICER mRNA levels correlated directly with those of TGF-β1, SMAD2 and SMAD3. In the LV from AS patients, DICER mRNA was up-regulated and its transcript levels correlated directly with TGF-β1, SMAD2, and SMAD3. Our results support that p-SMAD2/3 interacts with DICER1 to promote pre-miR-21 processing to mature miR-21. This new TGFβ-dependent regulatory mechanism is involved in miR-21 overexpression in cultured fibroblasts, and in the pressure overloaded LV of mice and human patients.

Temporal expression profiling of novel Spodoptera litura nucleopolyhedrovirus-encoded microRNAs upon infection of Sf21 cells

Baculoviruses are arthropod-specific pathogens, and find extensive applications in pest control strategies and recombinant protein expression. Spodoptera litura nucleopolyhedrovirus (SpltNPV) infects the tropical armyworm Spodoptera litura, which is an important polyphagous crop pest widely distributed in regions of Asia and Oceania. Using next-generation sequencing, we report stage-specific profiling of SpltNPV-encoded microRNAs (miRNAs) at different time intervals post-infection (p.i.) of Sf21 cells. Sequence length distribution analysis of the small RNA libraries revealed a significant increase in 20 nt reads and a reduction of other size fractions during late phases of infection. In silico miRNA prediction tools identified 48 novel SpltNPV-encoded miRNAs, of which 10 were validated experimentally in Sf21 cells using Northern blot analysis and TaqMan quantitative real-time (qRT)-PCR. The viral miRNAs were also found to be expressed in fat-body and mid-gut tissues of infected fifth-instar S. litura larva. qRT-PCR analysis confirmed that expression of most viral miRNAs was triggered 12 h p.i. and continued thereafter. Gene Ontology and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway annotation of computationally predicted targets of the reported miRNAs suggested a major impact of these miRNAs on cell signalling, protein translation and metabolic processes.

Overexpression of genes involved in miRNA biogenesis in medullary thyroid carcinomas with RET mutation

Abnormal expression of non-coding micro RNA (miRNA) has been described in medullary thyroid carcinoma (MTC). Expression of genes encoding factors involved in miRNA biogenesis results often deregulated in human cancer and correlates with aggressive clinical behavior. In this study, expression of four genes involved in miRNA biogenesis (DICER, DROSHA, DCGR8, and XPO5) was investigated in 54 specimens of MTC. Among them, 33 and 13 harbored RET and RAS mutations, respectively. DICER, DGCR8, and XPO5 mRNA levels were significantly overexpressed in MTC harboring RET mutations, in particular, in the presence of RET634 mutation. When MTCs with RET and RAS mutations were compared, only DGCR8 displayed a significant difference, while MTCs with RAS mutations did not show significant differences with respect to non-mutated tumors. We then attempted to correlate expression of miRNA biogenesis genes with tumor aggressiveness. According to the TNM status, MTCs were divided in two groups and compared (N0 M0 vs. N1 and/or M1): for all four genes no significant difference was detected. Cell line experiments, in which expression of a RET mutation is silenced by siRNA, suggest the existence of a causal relationship between RET mutation and overexpression of DICER, DGCR8, and XPO5 genes. These findings demonstrate that RET- but not RAS-driven tumorigenic alterations include abnormalities in the expression of some important genes involved in miRNA biogenesis that could represent new potential markers for targeted therapies in the treatment of RET-mutated MTCs aimed to restore the normal miRNA expression profile.

Identification of regulatory elements directing miR-23a-miR-27a-miR-24-2 transcriptional regulation in response to muscle hypertrophic stimuli

MiRNAs are small non-coding RNAs that significantly regulate the translation of protein coding genes in higher organisms. MicroRNAs are involved in almost every biological process, including early development, lineage commitment, growth and differentiation, cell death, and metabolic control. Misregulation of miRNAs belonging to the intergenic miR-23a-miR-27a-miR-24-2 cluster has been recently associated to cardiac and skeletal muscle diseases, and they are up-regulated in hypertrophic cardiomyopathy and skeletal muscle atrophy. Despite these facts, the basal transcriptional regulation of miR-23a/miR-27-a/miR-24-2 cluster and how it is altered under pathological conditions remain unclear. In this study, we identified and functionally characterized conserved upstream and downstream regulatory sequences from the miR-23a-miR-27a-miR-24-2 locus that are implicated on its transcriptional control. Our data demonstrate that Srf plays a pivotal role in modulating miR-23a-miR-27a-miR-24-2 cluster proximal promoter activity. Importantly, pro-hypertrophic signalling pathways such as those driven by angiotensin II and norepinephrine also regulate miR-23a-miR-27a-miR-24-2 cluster proximal promoter activity. Taking together, our results provide new insights into the regulatory networks driving miR-23a-miR-27a-miR-24-2 cluster expression in cardiac and skeletal muscles.

Lin28a regulates neuronal differentiation and controls miR-9 production

microRNAs shape the identity and function of cells by regulating gene expression. It is known that brain-specific miR-9 is controlled transcriptionally; however, it is unknown whether post-transcriptional processes contribute to establishing its levels. Here, we show that miR-9 is regulated transcriptionally and post-transcriptionally during neuronal differentiation of the embryonic carcinoma cell line P19. We demonstrate that miR-9 is more efficiently processed in differentiated than undifferentiated cells. We reveal that Lin28a affects miR-9 by inducing the degradation of its precursor through a uridylation-independent mechanism. Furthermore, we show that constitutively expressed untagged but not GFP-tagged Lin28a decreases differentiation capacity of P19 cells, which coincides with reduced miR-9 levels. Finally, using an inducible system we demonstrate that Lin28a can also reduce miR-9 levels in differentiated P19 cells. Together, our results shed light on the role of Lin28a in neuronal differentiation and increase our understanding of the mechanisms regulating the level of brain-specific microRNAs.