MiR-26b is down-regulated in carcinoma-associated fibroblasts from ER-positive breast cancers leading to enhanced cell migration and invasion

Human Aging and Cancer: Role of miRNA in Tumor Microenvironment

Human aging is an inevitable and complex phenomenon characterized by a progressive, gradual degradation of physiological and cellular processes that leads from vulnerability to death. Mammalian somatic cells display limited proliferative properties in vitro that results in a process of permanent cell cycle arrest commonly known as senescence. Events leading to cellular senescence are complex but may be due to the increase in tumor suppressor genes, caused by lifetime somatic mutations. Cumulative mutation leaves an imprint on the genome of the cell, an important risk factor for the occurrence of cancer. Adults over the age of 65+ are vulnerable to age related diseases such as cancers but such changes may begin at middle age. MicroRNAs (miRNAs), which are small non-coding RNA, can regulate cancer progression, recurrence and metastasis. This chapter discusses the role of miRNA in tumor microenvironment, consequent to aging.

Phosphoproteomic analysis of the antitumor effects of ginsenoside Rg3 in human breast cancer cells

The incidence of breast cancer has been increasing in China and the age of breast cancer onset is earlier compared with Western countries. Compounds commonly used in Traditional Chinese Medicine (TCM) are an important source of anticancer drugs. Ginseng is one of the most common medicines used in TCM. Ginsenosides, which are saponins found in the ginseng plant, are the major active components responsible for the chemopreventive effects of ginseng in cancer. However, the mechanisms by which ginsenosides exert their anticancer effects remain elusive. The current study combined tandem mass tag (TMT)-based quantification with titanium dioxide-based phosphopeptide enrichment to quantitatively analyze the changes in phosphoproteomes in breast cancer MDA-MB-231 cells that occur following treatment with the ginsenoside Rg3. A total of 5,140 phosphorylation sites on 2,041 phosphoproteins were quantified and it was demonstrated that the phosphorylation status of 13 sites were altered in MDA-MB-231 cells following treatment with Rg3. The perturbed phosphoproteins were: Cleavage and polyadenylation specificity factor subunit 7, elongation factor 2 (EEF2), HIRA-interacting protein 3, melanoma-associated antigen D2, myosin phosphatase Rho-interacting protein, probable E3 ubiquitin-protein ligase MYCBP2, PRKC apoptosis WT1 regulator protein, protein phosphatase 1 regulatory subunit 12A, E3 SUMO-protein ligase RanBP2, Septin-9, thymopoietin, and E3 UFM1-protein ligase 1. Western blotting confirmed that Rg3 increased the phosphorylation of EEF2 on Thr57 but did not alter the protein expression of EEF2 in MDA-MB-231 and HCC1143 cells. These ginsenoside Rg3-regulated proteins are involved in various biological processes, including protein synthesis, cell division and the inhibition of nuclear factor-κB signaling. The results of the present study revealed that Rg3 exerts its anticancer effects via a combination of different signaling pathways.

Novel Gene and Network Associations Found for Acute Lymphoblastic Leukemia Using Case-Control and Family-Based Studies in Multiethnic Populations

Background: Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, suggesting that germline variants influence ALL risk. Although multiple genome-wide association (GWA) studies have identified variants predisposing children to ALL, it remains unclear whether genetic heterogeneity affects ALL susceptibility and how interactions within and among genes containing ALL-associated variants influence ALL risk.Methods: Here, we jointly analyzed two published datasets of case-control GWA summary statistics along with germline data from ALL case-parent trios. We used the gene-level association method PEGASUS to identify genes with multiple variants associated with ALL. We then used PEGASUS gene scores as input to the network analysis algorithm HotNet2 to characterize the genomic architecture of ALL.Results: Using PEGASUS, we confirmed associations previously observed at genes such as ARID5B, IKZF1, CDKN2A/2B, and PIP4K2A, and we identified novel candidate gene associations. Using HotNet2, we uncovered significant gene subnetworks that may underlie inherited ALL risk: a subnetwork involved in B-cell differentiation containing the ALL-associated gene CEBPE, and a subnetwork of homeobox genes, including MEIS1Conclusions: Gene and network analysis uncovered loci associated with ALL that are missed by GWA studies, such as MEIS1 Furthermore, ALL-associated loci do not appear to interact directly with each other to influence ALL risk, and instead appear to influence leukemogenesis through multiple, complex pathways.Impact: We present a new pipeline for post hoc analysis of association studies that yields new insight into the etiology of ALL and can be applied in future studies to shed light on the genomic underpinnings of cancer. Cancer Epidemiol Biomarkers Prev; 26(10); 1531-9. ©2017 AACR.

Tumor microenvironment and noncoding RNAs as co-drivers of epithelial-mesenchymal transition and cancer metastasis

Reciprocal interactions between cancer cells and tumor microenvironment (TME) are crucial events in tumor progression and metastasis. Pervasive stromal reprogramming of TME modifies numerous cellular functions, including extracellular matrix (ECM) stiffness, inflammation, and immunity. These environmental factors allow selection of more aggressive cells that develop adaptive strategies associating plasticity and epithelial-mesenchymal transition (EMT), stem-like phenotype, invasion, immunosuppression, and resistance to therapies. EMT is a morphomolecular process that endows epithelial tumor cells with mesenchymal properties, including reduced adhesion and increased motility. Numerous studies have demonstrated involvement of noncoding RNAs (ncRNAs), such as miRNAs and lncRNAs, in tumor initiation, progression, and metastasis. NcRNAs regulate every hallmark of cancer and have now emerged as new players in induction and regulation of EMT. The reciprocal regulatory interactions between ncRNAs, TME components, and cancer cells increase the complexity of gene expression and protein translation in cancer. Thus, deeper understanding of molecular mechanisms controlling EMT will not only shed light on metastatic processes of cancer cells, but enhance development of new therapies targeting metastasis. In this review, we will provide recent findings on the role of known ncRNAs relevant to EMT and cancer metastasis and discuss the role of the interaction between ncRNAs and TME as co-drivers of EMT. Developmental Dynamics 247:405-431, 2018. © 2017 Wiley Periodicals, Inc.

Cancer associated fibroblasts: An essential role in the tumor microenvironment

Fibroblasts in the tumor stroma are well recognized as having an indispensable role in carcinogenesis, including in the initiation of epithelial tumor formation. The association between cancer cells and fibroblasts has been highlighted in several previous studies. Regulation factors released from cancer-associated fibroblasts (CAFs) into the tumor microenvironment have essential roles, including the support of tumor growth, angiogenesis, metastasis and therapy resistance. A mutual interaction between tumor-induced fibroblast activation, and fibroblast-induced tumor proliferation and metastasis occurs, thus CAFs act as tumor supporters. Previous studies have reported that by developing fibroblast-targeting drugs, it may be possible to interrupt the interaction between fibroblasts and the tumor, thus resulting in the suppression of tumor growth, and metastasis. The present review focused on the reciprocal feedback loop between fibroblasts and cancer cells, and evaluated the potential application of anti-CAF agents in the treatment of cancer.

Exosomal miRNAs and miRNA dysregulation in cancer-associated fibroblasts

Purpose

The present review aimed to assess the role of exosomal miRNAs in cancer-associated fibroblasts (CAFs), normal fibroblasts (NFs), and cancer cells. The roles of exosomal miRNAs and miRNA dysregulation in CAF formation and activation were summarized.

Methods

All relevant publications were retrieved from the PubMed database, with key words such as CAFs, CAF, stromal fibroblasts, cancer-associated fibroblasts, miRNA, exosomal, exosome, and similar terms.

Results

Recent studies have revealed that CAFs, NFs, and cancer cells can secrete exosomal miRNAs to affect each other. Dysregulation of miRNAs and exosomal miRNAs influence the formation and activation of CAFs. Furthermore, miRNA dysregulation in CAFs is considered to be associated with a secretory phenotype change, tumor invasion, tumor migration and metastasis, drug resistance, and poor prognosis.

Conclusions

Finding of exosomal miRNA secretion provides novel insights into communication among CAFs, NFs, and cancer cells. MicroRNA dysregulation is also involved in the whole processes of CAF formation and function. Dysregulation of miRNAs in CAFs can affect the secretory phenotype of the latter cells.

miR-26b Mimic Inhibits Glioma Proliferation In Vitro and In Vivo Suppressing COX-2 Expression

Glioma is the most common malignant tumor of the nervous system. Studies have shown the microRNA-26b (miR-26b)/cyclooxygenase-2 (COX-2) axis in the development and progression in many tumor cells. Our study aims to investigate the effect and mechanism of the miR-26b/COX-2 axis in glioma. Decreased expression of miR-26b with increased levels of COX-2 was found in glioma tissues compared with matched normal tissues. A strong negative correlation was observed between the level of miR-26b and COX-2 in 30 glioma tissues. The miR-26b was then overexpressed by transfecting a miR-26b mimic into U-373 cells. The invasive cell number and wound closing rate were reduced in U-373 cells transfected with miR-26b mimic. In addition, COX-2 siRNA enhanced the effect of miR-26b mimic in suppressing the expression of p-ERK1 and p-JNK. Finally, the in vivo experiment revealed that miR-26b mimic transfection strongly reduced the tumor growth, tumor volume, and expression of matrix metalloproteinase-2 (MMP-2) and MMP-9. Taken together, our research indicated a miR-26b/COX-2/ERK/JNK axis in regulating the motility of glioma in vitro and in vivo, providing a new sight for the treatment of glioma.

Bioinformatic analysis of microRNA-mRNA expression profiles of bladder tissue induced by bladder outlet obstruction in a rat model

Various microRNAs (miRNAs) have previously been demonstrated to exhibit an association with the process of bladder remodeling, induced by bladder outlet obstruction (BOO). However, little is known about miRNA and gene expression profiles and the molecular mechanism underlying bladder pathophysiological alterations. The present study used bioinformatic analysis technology to examine the altered miRNA and mRNA expression profiles of bladder tissue in a rat model of BOO and validate the involved signaling pathways. The gene expression profile data was downloaded from Gene Expression Omnibus (GEO), and the differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) were screened. Potential target genes of DEMs were predicted. The target genes and DEGs were used for further gene ontology (GO) analysis followed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis using the Database for Annotation, Visualization and Integrated Discovery. The present study additionally constructed a DEM‑DEG interaction network. A total of 9 DEMs (3 upregulated and 6 downregulated) were identified; 664 DEGs were screened. KEGG analysis revealed that the DEGs were involved in the regulation of the actin cytoske-leton, extracellular matrix (ECM) remodeling, cell adhesion and the cell cycle. Additionally, KEGG classification indicated that these genes were important in angiogenesis, and in the p53 and transforming growth factor‑β signaling pathways. Notably, rno‑miRNA (miR)‑26b and rno‑miR‑101b were the two larger nodes of the 7 obstruction‑associated DEMs and interacted with 32 and 27 DEGs, respectively. On removal of obstruction, few DEMs were present; however, 370 genes exhibited the opposite expression trend. The majority of pathways enriched for the DEGs were identified and were associated with ECM‑receptor interaction and focal adhesion. In the DEM‑DEG regulatory network, miR‑495, miR‑494 and their target genes were significantly differentially expressed. The present study demonstrated that miRNAs and genes may be potential biomarkers of bladder remodeling induced by BOO, and additionally provided novel insights into the molecular mechanisms underlying this disorder.

MicroRNA-211-5p suppresses tumour cell proliferation, invasion, migration and metastasis in triple-negative breast cancer by directly targeting SETBP1

Background:

Triple-negative breast cancer (TNBC) accounts for 15–20% of all breast cancer in women globally. This subtype often has early and high recurrence rates, resulting in poor survival, partially due to lack of targeted therapies. To date, the detailed molecular mechanisms underlying TNBC progression are unclear. Given the crucial role of microRNAs (miRNAs) in cancer metastasis, we aimed to analyse the expression and function of a metastasis-associated miRNA named miR-211-5p in TNBC.

Methods:

MiRNA array analysis was performed to search for metastasis-associated miRNAs in TNBC. The miR-211-5p expression in tumour tissues, adjacent non-tumourous breast tissues of TNBC patients and cell lines were evaluated by real-time PCR. The protein expression levels were analysed by western blot, immunohistochemistry and in situ hybridisation. Luciferase reporter assays were employed to validate the target of miR-211-5p. The effect of miR-211-5p on TNBC progression was investigated in vitro and in vivo.

Results:

MiR-211-5p was significantly downregulated in TNBC, and its expression level was associated with overall survival in TNBC. The expression of miR-211-5p suppressed TNBC cell proliferation, invasion, migration and metastasis in vitro and in vivo. Furthermore, SETBP1 was identified as a target of miR-211-5p. Through gain-of-function and loss-of-function studies, SETBP1 was shown to significantly affect colony and cell number in vitro. Enforced expression of miR-211-5p inhibited the expression of SETBP1 significantly and the restoration of SETBP1 expression reversed the inhibitory effects of miR-211-5p on TNBC cell proliferation and metastasis.

Conclusions:

These findings collectively demonstrate a tumour suppressor role of miR-211-5p in TNBC progression by targeting SETBP1, suggesting that miR-211-5p could serve as a potential prognostic biomarker and therapeutic target for TNBC.

Dysregulation of miRNA Expression in Cancer Associated Fibroblasts (CAFs) and Its Consequences on the Tumor Microenvironment

The tumor microenvironment, including cancer-associated fibroblasts (CAF), has developed as an important target for understanding tumor progression, clinical prognosis and treatment responses of cancer. Cancer cells appear to transform normal fibroblasts (NF) into CAFs involving direct cell-cell communication and epigenetic regulations. This review summarizes the current understanding on miR involvement in cancer cell—tumor environment/stroma communication, transformation of NFs into CAFs, their involved targets and signaling pathways in these interactions; and clinical relevance of CAF-related miR expression profiles. There is evidence that miRs have very similar roles in activating hepatic (HSC) and pancreatic stellate cells (PSC) as part of precancerous fibrotic diseases. In summary, deregulated miRs affect various intracellular functional complexes, such as transcriptional factors, extracellular matrix, cytoskeleton, EMT/MET regulation, soluble factors, tyrosine kinase and G-protein signaling, apoptosis and cell cycle & differentiation, but also formation and composition of the extracellular microenvironment. These processes result in the clinical appearance of desmoplasia involving CAFs and fibrosis characterized by deregulated stellate cells. In addition, modulated release of soluble factors can act as (auto)activating feedback loop for transition of NFs into their pathological counterparts. Furthermore, epigenetic communication between CAFs and cancer cells may confer to cancer specific functional readouts and transition of NF. MiR related epigenetic regulation with many similarities should be considered as key factor in development of cancer and fibrosis specific environment.

Carcinoma-associated fibroblasts: orchestrating the composition of malignancy

The tumor stroma is no longer seen solely as physical support for mutated epithelial cells but as an important modulator and even a driver of tumorigenicity. Within the tumor stromal milieu, heterogeneous populations of fibroblast-like cells, collectively termed carcinoma-associated fibroblasts (CAFs), are key players in the multicellular, stromal-dependent alterations that contribute to malignant initiation and progression. This review focuses on novel insights into the contributions of CAFs to disease progression, emergent events leading to the generation of CAFs, identification of CAF-specific biomarkers predictive of disease outcome, and recent therapeutic approaches aimed at blunting or reverting detrimental protumorigenic phenotypes associated with CAFs.

MiR-124 down-regulation is critical for cancer associated fibroblasts-enhanced tumor growth of oral carcinoma

Cancer associated fibroblasts (CAFs) are known to be involved in initiation, progression and metastasis of various cancers. However, the molecular mechanism of how CAFs affects the biological function of oral cancer (OC) has not been fully-addressed. In this study, we demonstrated that miR-124 was downregulated in oral CAFs and oral cancer cells (OCCs) when compared with matched normal fibroblasts (NFs). Hypermethylation in the promoter region of miR-124 genes was accounted for its downregulation. Interestingly, CAFs but not NFs exerted promotion effect on OCCs cell proliferation, migration and tumor growth in CAFs/NFs-OCCs co-culture. Furthermore, we identified Chemokine (C-C motif) ligand 2 (CCL2) and Interleukin 8 (IL-8) as two direct targets of miR-124. Over-expression of miR-124 in CAFs-OCCs co-culture abrogated CAFs-promoted OCCs cell growth and migration, and this inhibitory effect can be rescued by addition of CCL2 and IL-8. Finally, we showed that restoration of miR-124 expression by lentiviral infection or formulated miR-124 injection inhibited oral tumor growth in vivo suggesting miR-124 rescue could be a potential rationale for therapeutic applications in oral cancer in the future.

Overexpression of miR-26b-5p regulates the cell cycle by targeting CCND2 in GC-2 cells under exposure to extremely low frequency electromagnetic fields

The increasing prevalence of extremely low frequency electromagnetic fields (ELF-EMFs) exposure has raised considerable public concern regarding the potential hazardous effects of ELF-EMFs on male reproductive function. Increasing evidence indicates that miRNAs are necessary for spermatogenesis and male fertility. However, the regulation of miRNA expression and the roles of miRNAs in response to ELF-EMFs remain unclear. In our study, mouse spermatocyte-derived GC-2 cells were intermittently exposed to a 50 Hz ELF-EMF for 72 h (5 min on/10 min off) at magnetic field intensities of 1 mT, 2 mT and 3 mT. MiR-26b-5p was differentially expressed in response to different magnetic field intensities of ELF-EMFs. The host gene CTDSP1 showed an unmethylation status in GC-2 cells at different magnetic field intensities of ELF-EMF exposure. MiR-26b-5p had no significant, obvious influence on the cell viability, apoptosis or cell cycle of GC-2 cells. However, the overexpression of miR-26b-5p significantly decreased the percentage of G0/G1 phase cells and slightly increased the percentage of S phase cells compared to the sham group that was exposed to a 50 Hz ELF-EMF. Computational algorithms identified Cyclin D2 (CCND2) as a direct target of miR-26b-5p. MiR-26b-5p and a 50 Hz ELF-EMF altered the expression of CCND2 at both the mRNA and protein levels. Overexpressed miR-26b-5p in GC-2 cells can change the mRNA expression of CCND2 following 50 Hz ELF-EMF at 3 mT. These findings demonstrate that miR-26b-5p could serve as a potential biomarker following 50 Hz ELF-EMF exposure, and miR-26b-5p-CCND2-mediated cell cycle regulation might play a pivotal role in the biological effects of ELF-EMFs.

LncRNA profile study reveals four-lncRNA signature associated with the prognosis of patients with anaplastic gliomas

Anaplastic glioma is Grade III and the median overall survival is about 37.6 months. However, there are still other factors that affect the prognosis for anaplastic glioma patients due to variable overall survival. So we screened four-lncRNA signature (AGAP2-AS1, TPT1-AS1, LINC01198 and MIR155HG) from the lncRNA expression profile from the GSE16011, CGGA and REMBRANDT datasets. The patients in low risk group had longer overall survival than high risk group (median OS 2208.25 vs. 591.30 days; P < 0.0001). Moreover, patients in the low risk group showed similar overall survival to Grade II patients (P = 0.1669), while the high risk group showed significant different to Grade IV (P = 0.0005) with similar trend. So based on the four-lncRNA, the anaplastic gliomas could be divided into grade II-like and grade IV-like groups. On the multivariate analysis, it showed the signature was an independent prognostic factor (P = 0.000). The expression of four lncRNAs in different grades showed that AGAP2-AS1, LINC01198 and MIR155HG were increased with tumor grade, while TPT1-AS1 was decreased. Knockdown of AGAP2-AS1 can inhibit the cell proliferation, migration and invasion, while increase the apoptosis cell rates in vitro. In conclusion, our results showed that the four-lncRNA signature has prognostic value for anaplastic glioma. Moreover, clinicians should conduct corresponding therapies to achieve best treatment with less side effects for two groups patients.

miR-26a-5p suppresses tumor metastasis by regulating EMT and is associated with prognosis in HCC

OBJECTIVE

To determine the role of miR-26a-5p in tumor invasion and metastasis in hepatocellular carcinoma (HCC).

METHODS

We evaluated miR-26a-5p expression in HCC tissues by quantitative PCR and then analyzed its clinical significance using a Cox regression model. Transwell and nude mouse models were used to examine tumor metastasis in vitro and in vivo, respectively. The relationship between miR-26a-5p and epithelial-mesenchymal transition was also investigated by q-PCR and western blot.

RESULTS

Strong downregulation of miR-26a-5p was observed in tumor tissues compared to paired adjacent normal tissues. Moreover, patients with low miR-26a-5p expression had a significantly poorer prognosis than those with high expression. The multivariate analysis indicated that miR-26a-5p expression was an independent prognostic indicator. The experimental transwell model and athymic mouse model revealed that miR-26a-5p depressed tumor metastasis in vitro and in vivo, respectively. In addition, the decreased miR-26a-5p level observed in HCC was associated with reduced E-cadherin expression and upregulation of vimentin, which affects the molecular mechanism of EMT.

CONCLUSION

Downregulation of miR-26a-5p promotes tumor metastasis by targeting EMT and influences the prognosis of HCC patients. Therefore, miR-26a-5p has potential as a new biomarker and therapeutic target.

Oxidative stress induced autophagy in cancer associated fibroblast enhances proliferation and metabolism of colorectal cancer cells

Tumors are comprised of malignant cancer cells and stromal cells which constitute the tumor microenvironment (TME). Previous studies have shown that cancer associated fibroblast (CAF) in TME is an important promoter of tumor initiation and progression. However, the underlying molecular mechanisms by which CAFs influence the growth of colorectal cancer cells (CRCs) have not been clearly elucidated. In this study, by using a non-contact co-culture system between human colorectal fibroblasts (CCD-18-co) and CRCs (LoVo, SW480, and SW620), we found that fibroblasts existing in tumor microenvironment positively influenced the metabolism of colorectal cancer cells, through its autophagy and oxidative stress pathway which were initially induced by neighboring tumor cells. Therefore, our data provided a novel possibility to develop fibroblasts as a potential target to treat CRC.

MicroRNA-26b Enhances the Radiosensitivity of Hepatocellular Carcinoma Cells by Targeting EphA2

Sensitizing hepatocellular carcinoma (HCC) cells to irradiation is important to achieve satisfactory therapeutic effect with low-dose radiotherapy. Erythropoietin-producing hepatocellular carcinoma A2 (EphA2) is a member of the Eph receptor family that constitutes the largest family of tyrosine kinase receptors. EphA2 overexpression is one of the poor prognostic factors in many progressive cancers. Importantly, EphA2 is a potential target of microRNA-26b (miR-26b), and miR-26b expression is down-regulated in several types of cancer. In this study, we measured the expression levels of miR-26b and EphA2 protein in seven human HCC cell lines by quantitative PCR and western blot analysis, respectively. Overall, lower miR-26b expression levels tended to be associated with higher EphA2 levels in HCC cell lines. Among the cell lines examined, 97H HCC cells expressed the lowest level of miR-26b and highest level of EphA2 protein. Thus, using 97H HCC cells, EphA2 mRNA was verified as the target of miR-26b by the luciferase reporter assay. Accordingly, a synthetic miR-26b, miR-26b mimics, was used to mimic the function of endogenous miR-26b. In 97H HCC cells transfected with miR-26b mimics or short-hairpin RNA targeting EphA2 mRNA, expression of EphA2 protein was reduced, which was associated with significantly lower proliferation rate and invasion ability and with higher apoptosis rate in response to low-dose irradiation, compared to control cells. In contrast, 97H HCC cells over-expressing EphA2 showed higher proliferation rate and invasion ability and lower apoptosis rate upon irradiation. These data suggest that miR-26b enhances the radiosensitivity of 97H HCC cells by targeting EphA2 protein.

miR-146b-5p mediates p16-dependent repression of IL-6 and suppresses paracrine procarcinogenic effects of breast stromal fibroblasts

Increasing evidence support the critical roles of active stromal fibroblasts in breast cancer development and spread. However, the mediators and the mechanisms of regulation are still not well defined. We have shown here that the tumor suppressor p16^INK4A protein inhibits the pro-carcinogenic effects of breast stromal fibroblasts through repressing the expression/secretion of IL-6. Indeed, p16^INK4A suppresses IL-6 at the mRNA and protein levels. This effect is mediated trough miR-146b-5p, which inhibits IL-6 expression through a specific sequence at the IL-6 3′UTR. In addition, we present clear evidence that miR-146b-5p inhibition is sufficient to transactivate breast stromal fibroblasts, which promote epithelial-to-mesenchymal-transition in breast cancer cells in a paracrine manner. By contrast, ectopic expression of miR-146b-5p in active fibroblasts abrogated their pro-carcinogenic effects. The physiological importance of miR-146b-5p inhibition was revealed by showing that the levels of pre-miR-146b-5p as well as its mature form are reduced in cancer-associated fibroblasts as compared with their normal adjacent counterparts from cancer-free tissues isolated from the same patients. Interestingly, treatment of active breast stromal fibroblasts with curcumin increased the level of the p16^INK4A coding CDKN2A mRNA and miR-146b-5p and suppressed IL-6, which confirms the repressive effect of these two tumor suppressor molecules on IL-6, and shows the possible “normalization” of cancer-related active fibroblasts. These results show that miR-146b-5p has non-cell-autonomous tumor suppressor function through inhibition of IL-6, suggesting that targeting this microRNA in breast stromal fibroblasts could be of great therapeutic value.

miR-101 inhibits glioma cell invasion via the downregulation of COX-2

Glioma is the most common type of primary tumor of the central nervous system. The present study aimed to demonstrate the role of miR-101 and cyclooxygenase-2 (COX-2) in the initiation and development of glioma. The expression of miR-101 and COX-2 in normal and malignant human glial cells and tissues was determined by western blotting and quantitative polymerase chain reaction analysis. The role of miR-101 on COX-2 expression was evaluated by a dual-luciferase reporter assay. The effects of miR-101 and COX-2 in glioma cell proliferation and invasion was verified by CCK-8 test and Transwell assays, respectively. The present study demonstrated that miR-101 expression was downregulated while COX-2 was upregulated in glioma tissues and cells. Furthermore, transfection of miR-101 significantly downregulated COX-2 expression in both U373 and U87 glioma cells. In addition, further experiments revealed that overexpression of miR-101 resulted in significant inhibition of the in vitro proliferation and migration of glioma cells, and the in vivo growth of established tumors. Direct downregulation of COX-2 by transfection with corresponding small interfering RNA also inhibited the proliferation and invasion of glioma cells. These results indicate that downregulation of miR-101 is involved in the initiation and development of glioma via COX-2 upregulation.

miR-26b enhances radiosensitivity of hepatocellular carcinoma cells by targeting EphA2

OBJECTIVES

Although low-dose radiotherapy (RT) that involves low collateral damage is more suitable for hepatocellular carcinoma (HCC) than traditional high-dose RT, but to achieve satisfactory therapeutic effect with low-dose RT, it is necessary to sensitize HCC cells to irradiation. This study was aimed to determine whether radiosensitivity of HCC cells can be enhanced using miR-26b by targeting erythropoietin producing human hepatocelluar A2 (EphA2).

MATERIALS AND METHODS

The levels of miR-26b and EphA2 expression in multiple HCC cell lines were assessed by qPCR and western blotting, respectively, and compared with those in a hepatic cell line. HCC 97H cells were transfected with miR-26b mimics, EphA2-ShRNA or EphA2 over-expression vector before exposure to low-dose irradiation.

RESULTS

Different degrees of miR-26b down-regulation and EphA2 up-regulation were observed in all HCC cell lines, among which the HCC 97H cell line expressed the lowest level of miR-26b and highest level of EphA2. EphA2 was verified as the target of miR-26b by dual luciferase reporter assay. HCC 97H cells transfected with miR-26b mimics or EphA2-ShRNA reduced the expression of EphA2 protein, with significantly lower cell proliferation rate and cell invasion ability and higher apoptosis rate in response to low-dose irradiation than those in the non-transfected cells. These results were reversed after EphA2 was overexpressed by transfection with the EphA2 overexpression vector. Co-transfection with miR-26b mimics and EphA2 overexpression vector barely altered EphA2 expression level and cell response to low-dose irradiation.

CONCLUSION

These data suggest that miR-26b enhances radiosensitivity of HCC 97H cells by targeting EphA2 protein.

Context Specific and Differential Gene Co-expression Networks via Bayesian Biclustering

Identifying latent structure in high-dimensional genomic data is essential for exploring biological processes. Here, we consider recovering gene co-expression networks from gene expression data, where each network encodes relationships between genes that are co-regulated by shared biological mechanisms. To do this, we develop a Bayesian statistical model for biclustering to infer subsets of co-regulated genes that covary in all of the samples or in only a subset of the samples. Our biclustering method, BicMix, allows overcomplete representations of the data, computational tractability, and joint modeling of unknown confounders and biological signals. Compared with related biclustering methods, BicMix recovers latent structure with higher precision across diverse simulation scenarios as compared to state-of-the-art biclustering methods. Further, we develop a principled method to recover context specific gene co-expression networks from the estimated sparse biclustering matrices. We apply BicMix to breast cancer gene expression data and to gene expression data from a cardiovascular study cohort, and we recover gene co-expression networks that are differential across ER+ and ER- samples and across male and female samples. We apply BicMix to the Genotype-Tissue Expression (GTEx) pilot data, and we find tissue specific gene networks. We validate these findings by using our tissue specific networks to identify trans-eQTLs specific to one of four primary tissues.

Export of microRNAs: A Bridge between Breast Carcinoma and Their Neighboring Cells

Breast cancer is a leading type of cancer among women in India as well as worldwide. According to the WHO 2015 report, it has been anticipated that there would be a twofold rise in the death due to breast cancer among women. The heterogeneous property of breast carcinoma has been suggested to be linked with dedicated set of communication and signaling pathway with their surroundings, which culminate into progression and development of the cancer. Among the plethora of communication tools in the hand of breast carcinoma cells is the recently appreciated exocytosis of the tightly packed short non-coding RNA molecules, predominantly the microRNAs (miRNAs). Recent studies suggest that miRNAs may work as courier messengers to participate in endocrine and paracrine signaling to facilitate information transfer between breast carcinoma and their neighboring cells. Evidence suggests that breast tumor cells communicate via packaged miRNAs in the tumor-released microvesicles, which enrich the tumor microenvironment. There is a strong view that dissecting out the mechanistic and regulatory aspects of miRNA export and role may uncover many prospects for overcoming the signaling defects and thereby controlling aberrant cell division. The detection of circulating miRNAs associated with breast carcinoma can also be used as biomarkers for early diagnosis. This review article is an attempt to provide updated knowledge on implications of short RNAs and their transport in the breast cancer pathophysiology.

Essential role of miRNAs in orchestrating the biology of the tumor microenvironment

MicroRNAs (miRNAs) are emerging as central players in shaping the biology of the Tumor Microenvironment (TME). They do so both by modulating their expression levels within the different cells of the TME and by being shuttled among different cell populations within exosomes and other extracellular vesicles. This review focuses on the state-of-the-art knowledge of the role of miRNAs in the complexity of the TME and highlights limitations and challenges in the field. A better understanding of the mechanisms of action of these fascinating micro molecules will lead to the development of new therapeutic weapons and most importantly, to an improvement in the clinical outcome of cancer patients.

A Set of miRNAs, Their Gene and Protein Targets and Stromal Genes Distinguish Early from Late Onset ER Positive Breast Cancer

Breast cancer (BC) in young adult patients (YA) has a more aggressive biological behavior and is associated with a worse prognosis than BC arising in middle aged patients (MA). We proposed that differentially expressed miRNAs could regulate genes and proteins underlying aggressive phenotypes of breast tumors in YA patients when compared to those arising in MA patients.

OBJECTIVE

Using integrated expression analyses of miRs, their mRNA and protein targets and stromal gene expression, we aimed to identify differentially expressed profiles between tumors from YA-BC and MA-BC.

METHODOLOGY AND RESULTS

Samples of ER+ invasive ductal breast carcinomas, divided into two groups: YA-BC (35 years or less) or MA-BC (50-65 years) were evaluated. Screening for BRCA1/2 status according to the BOADICEA program indicated low risk of patients being carriers of these mutations. Aggressive characteristics were more evident in YA-BC versus MA-BC. Performing qPCR, we identified eight miRs differentially expressed (miR-9, 18b, 33b, 106a, 106b, 210, 518a-3p and miR-372) between YA-BC and MA-BC tumors with high confidence statement, which were associated with aggressive clinicopathological characteristics. The expression profiles by microarray identified 602 predicted target genes associated to proliferation, cell cycle and development biological functions. Performing RPPA, 24 target proteins differed between both groups and 21 were interconnected within a network protein-protein interactions associated with proliferation, development and metabolism pathways over represented in YA-BC. Combination of eight mRNA targets or the combination of eight target proteins defined indicators able to classify individual samples into YA-BC or MA-BC groups. Fibroblast-enriched stroma expression profile analysis resulted in 308 stromal genes differentially expressed between YA-BC and MA-BC.

CONCLUSION

We defined a set of differentially expressed miRNAs, their mRNAs and protein targets and stromal genes that distinguish early onset from late onset ER positive breast cancers which may be involved with tumor aggressiveness of YA-BC.

MicroRNA Targeting to Modulate Tumor Microenvironment

Communication between stromal cells and tumor cells initiates tumor growth, angiogenesis, invasion, and metastasis. Stromal cells include cancer-associated fibroblasts, tumor-associated macrophages, pericytes, endothelial cells, and infiltrating immune cells. MicroRNAs (miRNAs) in the tumor microenvironment have emerged as key players involved in the development of cancer and its progression. miRNAs are small endogenous non-protein-coding RNAs that negatively regulate the expression of multiple target genes at post-transcriptional level and thereby control many cellular processes. In this review, we provide a comprehensive overview of miRNAs dysregulated in different stromal cells and their impact on the regulation of intercellular crosstalk in the tumor microenvironment. We also discuss the therapeutic significance potential of miRNAs to modulate the tumor microenvironment. Since miRNA delivery is quite challenging and the biggest hurdle for clinical translation of miRNA therapeutics, we review various non-viral miRNA delivery systems that can potentially be used for targeting miRNA to stromal cells within the tumor microenvironment.

TNKS1BP1 functions in DNA double-strand break repair though facilitating DNA-PKcs autophosphorylation dependent on PARP-1

TNKS1BP1 was originally identified as an interaction protein of tankyrase 1, which belongs to the poly(ADP-ribose) polymerase (PARP) superfamily. PARP members play important roles for example in DNA repair, telomere stability and mitosis regulation. Although the TNKS1BP1 protein was considered to be a poly(ADP-ribosyl)ation acceptor of tankyrase 1, its function is still unknown. Here we firstly identified that TNKS1BP1 was up-regulated by ionizing radiation (IR) and the depletion of TNKS1BP1 significantly sensitized cancer cells to IR. Neutral comet assay, pulsed-field gel electrophoresis, and γH2AX foci analysis indicated that TNKS1BP1 is required for the efficient repair of DNA double-strand breaks (DSB). The TNKS1BP1 protein was demonstrated to interact with DNA-dependent protein kinase (DNA-PKcs) and poly(ADP-ribose) polymerase 1 (PARP-1), by co-immunoprecipitation analysis. Moreover, TNKS1BP1 was shown to promote the association of PARP-1 and DNA-PKcs. Overexpression of TNKS1BP1 induced the autophosphorylation of DNA-PKcs/Ser2056 in a PARP-1 dependent manner, which contributed to an increased capability of DNA DSB repair. Inhibition of PARP-1 blocked the TNKS1BP1-mediated DNA-PKcs autophosphorylation and attenuated the PARylation of DNA-PKcs. TNKS1BP1 is a newly described component of the DNA DSB repair machinery, which provides much more mechanistic evidence for the rationale of developing effective anticancer measures by targeting PARP-1 and DNA-PKcs.

Proteomic Analysis of Epithelial to Mesenchymal Transition (EMT) Reveals Cross-talk between SNAIL and HDAC1 Proteins in Breast Cancer Cells

Epithelial to mesenchymal transition (EMT)(1) occurs naturally during embryogenesis, tissue repair, cancer progression, and metastasis. EMT induces cellular and microenvironmental changes resulting in loss of epithelial and acquisition of mesenchymal phenotypes, which promotes cellular invasive and migratory capabilities. EMT can be triggered by extracellular factors, including TGF-β, HGF, and EGF. Overexpression of transcription factors, such as SNAIL, SLUG, ZEB1/2, and TWIST1, also induces EMT and is correlated to cancer aggressiveness. Here, the breast adenocarcinoma cell line MCF7 was transduced with SNAIL to identify specific mechanisms controlled by this transcription factor during EMT. Overexpression of SNAIL led to EMT, which was thoroughly validated by molecular, morphological, and functional experiments. Subcellular proteome enrichment followed by GEL-LC-MS/MS was performed to provide extensive protein fractionation and in-depth proteomic analysis. Quantitative analysis relied on a SILAC strategy, using the invasive breast cancer cell line MDA-MB-231 as a reference for quantitation. Subsets of proteins enriched in each subcellular compartment led to a complementary list of 4289 proteins identified with high confidence. A subset of differentially expressed proteins was validated by Western blot, including regulation in specific cellular compartments, potentially caused by protein translocation. Protein network analysis highlighted complexes involved in cell cycle control and epigenetic regulation. Flow cytometry analysis indicated that SNAIL overexpression led to cell cycle arrest in G0/G1 phases. Furthermore, down-regulation of HDAC1 was observed, supporting the involvement of epigenetic processes in SNAIL-induced EMT. When HDAC1 activity was inhibited, MCF7 not only apparently initiated EMT but also up-regulated SNAIL, indicating the cross-talk between these two proteins. Both HDAC1 inhibition and SNAIL overexpression activated the AKT pathway. These molecular mechanisms appear to be essential to EMT and therefore for cancer metastasis. Specific control of such epigenetic processes might then represent effective approaches for clinical management of metastatic cancer.

3-D Tissue Modelling and Virtual Pathology as New Approaches to Study Ductal Carcinoma In Situ

Widespread screening mammography programmes mean that ductal carcinoma in situ (DCIS), a pre-invasive breast lesion, is now more frequently diagnosed. However, not all diagnosed DCIS lesions progress to invasive breast cancer, which presents a dilemma for clinicians. As such, there is much interest in studying DCIS in the laboratory, in order to help understand more about its biology and determine the characteristics of those that progress to invasion. Greater knowledge would lead to targeted and better DCIS treatment. Here, we outline some of the models available to study DCIS, with a particular focus on animal-free systems.

Recent highlights of experimental research for inhibiting tumor growth by using Chinese medicine

To give an overview of contemporary experimental research using Chinese medicine (CM) for the treatment of cancer. As an integral part of mainstream medicine in the People's Republic of China, CM emphasizes improvements in holistic physical condition instead of merely killing tumor cells, which is consistent with the current medical model that advocates patient-oriented treatment. Great progress has been made in experimental research, and the principle aspects include anti-tumor angiogenesis, inducing apoptosis and differentiation, reversing multidrug resistance, and improving immune function. As a current hot topic in cancer research, tumor microenvironment (TME) highlights the mutual and interdependent interaction between tumor cells and their surrounding tissues, and the CM treatment concept bears a striking resemblance to it. To date, primary points of TME include extracellular matrix remodeling, inflammation, hypoxia, and angiogenesis, but trials using CM with a focus on TME are rare. Despite considerable recent development, experimental research on CM for solving cancer issues appears insufficient. Greater efforts in this field are urgently needed.

MicroRNA-26b Modulates the NF-κB Pathway in Alveolar Macrophages by Regulating PTEN

NF-κB is one of the best-characterized transcription factors, providing the link between early membrane-proximal signaling events and changes in many inflammatory genes. MicroRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level. In this study, we evaluated the role of miR-26b in the LPS-induced inflammatory response in bovine alveolar macrophages (bAMs). LPS stimulation of bAMs upregulated miR-26b at 1 h and downregulated it at 6 and 36 h. Overexpression of miR-26b in bAMs enhanced the LPS-induced mRNA expression of proinflammatory cytokines and chemokines, including TNF-α, IL-1β, IL-8, and IL-10, but it directly inhibited that of IL-6. A similar trend was observed for the release of these cytokines and chemokines from bAMs. miR-26b directly bound the 3'-untranslated region of PTEN, leading to the reduction of PTEN protein in bAMs. miR-26b also enhanced the LPS-induced NF-κB signaling pathway, as revealed by increased NF-κB transcriptional activity and phosphorylation of p65, IκBα, IκB kinase, and Akt. Moreover, PTEN silencing increased the LPS-induced mRNA expression of TNF-α, IL-1β, IL-6, IL-8, and IL-10 and upregulated the NF-κB pathway. Taken together, we conclude that miR-26b participates in the inflammatory response of LPS-stimulated bAMs by modulating the NF-κB pathway through targeting PTEN.

Down-Regulation of miR-92 in Breast Epithelial Cells and in Normal but Not Tumour Fibroblasts Contributes to Breast Carcinogenesis

BACKGROUND

MicroRNA (miR) expression is commonly dysregulated in many cancers, including breast. MiR-92 is one of six miRs encoded by the miR-17-92 cluster, one of the best-characterised oncogenic miR clusters. We examined expression of miR-92 in the breast epithelium and stroma during breast cancer progression. We also investigated the role of miR-92 in fibroblasts in vitro and showed that down-regulation in normal fibroblasts enhances the invasion of breast cancer epithelial cells.

METHODOLOGY/PRINCIPAL FINDINGS

We used laser microdissection (LMD) to isolate epithelial cells from matched normal, DCIS and invasive tissue from 9 breast cancer patients and analysed miR-92 expression by qRT-PCR. Expression of ERβ1, a direct miR-92 target, was concurrently analysed for each case by immunohistochemistry. LMD was also used to isolate matched normal (NFs) and cancer-associated fibroblasts (CAFs) from 14 further cases. Effects of miR-92 inhibition in fibroblasts on epithelial cell invasion in vitro was examined using a Matrigel™ assay. miR-92 levels decreased in microdissected epithelial cells during breast cancer progression with highest levels in normal breast epithelium, decreasing in DCIS (p<0.01) and being lowest in invasive breast tissue (p<0.01). This was accompanied by a shift in cell localisation of ERβ1 from nuclear expression in normal breast epithelium to increased cytoplasmic expression during progression to DCIS (p = 0.0078) and invasive breast cancer (p = 0.031). ERβ1 immunoreactivity was also seen in stromal fibroblasts in tissues. Where miR-92 expression was low in microdissected NFs this increased in matched CAFs; a trend also seen in cultured primary fibroblasts. Down-regulation of miR-92 levels in NFs but not CAFs enhanced invasion of both MCF-7 and MDA-MB-231 breast cancer epithelial cells.

CONCLUSIONS

miR-92 is gradually lost in breast epithelial cells during cancer progression correlating with a shift in ERβ1 immunoreactivity from nuclei to the cytoplasm. Our data support a functional role in fibroblasts where modification of miR-92 expression can influence the invasive capacity of breast cancer epithelial cells. However in silico analysis suggests that ERβ1 may not be the most important miR-92 target in breast cancer.

miR-101 represses lung cancer by inhibiting interaction of fibroblasts and cancer cells by down-regulating CXCL12

Cancer-associated fibroblasts (CAFs) are the main component of tumor stroma which support tumor progression. Here, we set out to determine the factors that may be involved in dramatic alteration of microRNAs (miRNAs) expression pattern in CAFs. miRNAs analyses identified differential expression of 15 microRNAs, with miR-101 being the most downregulated miRNA in CAFs which were different from the normal fibroblasts. We examined several putative miR-101 target genes identified by microarray analysis and demonstrated that miR-101 directly targets CXCL12, which play important roles in CAFs. Overexpression of miR-101 significantly impaired the ability of CAFs to stimulate tumor cell proliferation, sphere formation migration and invasion, and enhanced apoptosis. Further research showed that the cellular biological behavior was regulated by miR-101 targeting CXCL12. These findings provide new insights miR-101 down-regulation in CAFs could inhibit lung cancer proliferation and metastasis via targeting CXCL12.

Expression of microRNA‑26b and identification of its target gene EphA2 in pituitary tissues in Yanbian cattle

microRNAs (miRNAs/miRs) are a class of single-stranded non-coding RNA molecules of 19–24 nucleotides (nt) in length. They are widely expressed in animals, plants, bacteria and viruses. Via specific mRNA complementary pairing of target genes, miRNAs are able to regulate the expression of mRNA levels or inhibit protein translation following transcription. miRNA expression has a time- and space specificity, and it is involved in cell proliferation and differentiation, apoptosis, development, tumor metastasis occurrence and other biological processes. miR-26b is an miRNA of 22 nt and is important in the regulation of cellular processes. With the advancement of molecular biology techniques in recent years, there have been extensive investigations into miR-26b. Numerous studies have observed that miR-26b is involved in early embryonic development, cell proliferation regulation, pituitary hormone secretion and other physiological activities. miRNAs are associated with the function of propagation. The present study used reverse transcription quantitative polymerase chain reaction to detect the relative expression levels of miR-26b in the pituitary tissue of Yanbian cattle at different developmental stages. The 2^−ΔΔCt method was used to calculate the relative gene expression levels. The miRNA target gene database TargetScan and RNA22 were used for prediction of the miR-26b target gene and selective recognition was also performed. The results demonstrated that miR-26b is expressed in the pituitary tissues of Yanbian cattle at 6 and 24 months of age. The relative expression levels of miR-26b in the pituitary tissues of 24-month-old Yanbian cattle were 2.41 times that of those in the six-month-old Yanbian cattle, demonstrating significant differences in the relative expression (P<0.01). The relative expression of the candidate target genes, EphA2 and miR-26b, exhibited the opposite expression pattern. The relative expression levels in the pituitary tissues of six-month-old Yanbian cattle were 3.34 times that of those in 24-month-old Yanbian cattle (P<0.01). There are miR-26b binding sites in the 3′-untranslated region (3′-UTR) of EphA2 in bovine, human, murine and other mammalian mRNAs, suggesting that the EphA2 gene may be a target gene of miR-26b. The results of a Luciferase reporter system assay revealed that miR-26b is able to suppress EphA2 expression at the transcription level. Following the site-directed mutagenesis of plasmid EphA2 3′-UTR pmirGLO-MUT- and miR-26b mimic-transfected HeLa cells, the dual-luciferase reporter gene assay revealed that there were three consecutive nucleotide mutations in the 3′-UTR, binding with the predicted seed region. This may have caused the miR-26b inhibition of luciferase activity to decrease from 60% in the wild-type to 26%, suggesting that miR-26b achieved its function via binding with the TACTTGAA sequence of the 3′-UTR in EphA2. In conclusion, the present study successfully assessed the expression pattern of miR-26b in the pituitary tissue of Yanbian cattle, and also confirmed that EphA2 was a target gene of miR-26b in Yanbian cattle in vitro. The present study provided the theoretical basis to further investigate the role of miR-26b in early embryonic development, pituitary hormone secretion and other reproductive functions.

Specific upregulation of RHOA and RAC1 in cancer-associated fibroblasts found at primary tumor and lymph node metastatic sites in breast cancer

The importance of tumor-stromal cell interactions in breast tumor progression and invasion is well established. Here, an evaluation of differential genomic profiles of carcinoma-associated fibroblasts (CAFs) compared to fibroblasts derived from tissues adjacent to fibroadenomas (NAFs) revealed altered focal adhesion pathways. These data were validated through confocal assays. To verify the possible role of fibroblasts in lymph node invasion, we constructed a tissue microarray consisting of primary breast cancer samples and corresponding lymph node metastasis and compared the expression of adhesion markers RhoA and Rac1 in fibroblasts located at these different locations. Two distinct tissue microarrays were constructed from the stromal component of 43 primary tumors and matched lymph node samples, respectively. Fibroblasts were characterized for their expression of α-smooth muscle actin (α-SMA) and vimentin. Moreover, we verified the level of these proteins in the stromal compartment from normal adjacent tissue and in non-compromised lymph nodes. Our immunohistochemistry revealed that 59 % of fibroblasts associated with primary tumors and 41 % of the respective metastatic lymph nodes (p = 0.271) displayed positive staining for RhoA. In line with this, 57.1 % of fibroblasts associated with primary tumors presented Rac1-positive staining, and the frequency of co-positivity within the lymph nodes was 42.9 % (p = 0.16). Expression of RhoA and Rac1 was absent in fibroblasts of adjacent normal tissue and in compromised lymph nodes. Based on our findings that no significant changes were observed between primary and metastatic lymph nodes, we suggest that fibroblasts are active participants in the invasion of cancer cells to lymph nodes and support the hypothesis that metastatic tumor cells continue to depend on their microenvironment.

MiR-26b modulates insulin sensitivity in adipocytes by interrupting the PTEN/PI3K/AKT pathway

BACKGROUND

MicroRNAs (miRNAs) have emerged as epigenetic regulators of metabolism and energy homeostasis. There is a growing body of evidence pointing to miRNAs that have important regulatory roles in insulin sensitivity.

OBJECTIVE

The aim of this work was to explore the expression and mechanism of action of miR-26b in obesity-related insulin resistance (IR) in adipocytes.

METHODS

Quantitative real-time PCR was performed to determine miR-26b expression in obese rodent models, human obesity subjects and insulin-resistant adipocytes. We analysed the roles of miR-26b overexpression and inhibition on glucose uptake in adipocytes. Western blotting was used to detect the levels of protein molecules involved in the phosphoinositide-3-kinase (PI3K) pathway. Bioinformatics and the Dual Luciferase Assay were used to identify the target gene of miR-26b. We assessed the regulatory roles of miR-26b on the phosphatase and tensin homologue (PTEN)/PI3K/AKT pathway and the relationship between miR-26b and the metabolism of human obese subjects.

RESULTS

Levels of miR-26b are reduced in visceral adipose tissue (VAT) in obese rodent models, human obesity and insulin-resistant adipocytes. MiR-26b promotes insulin-stimulated glucose uptake and increases insulin-stimulated glucose transporter type 4 translocation to the plasma membrane in human mature adipocytes. MiR-26b modulates insulin-stimulated AKT activation via inhibition of its target gene, PTEN, and significantly increases insulin sensitivity via the PTEN/PI3K/AKT pathway. The expression level of miR-26b negatively correlates with increasing body mass index and homeostasis model assessment for IR in human obese subjects.

CONCLUSION

Decreased miR-26b expression in VAT may be involved in obesity-related IR by interrupting the PTEN/PI3K/AKT pathway.

Mcl-1 Is a Novel Target of miR-26b That Is Associated with the Apoptosis Induced by TRAIL in HCC Cells

Aim. To investigate the role of miR-26b and Mcl-1 in TRAIL-inducing cell death in hepatocellular carcinoma. Methods. The expression of miR-26b and Mcl-1 in HCC was detected by RT-qPCR and western blot. The regulation of Mcl-1 by miR-26b was determined by luciferase reporter assay. MTT and flow cytometry were employed to detect the cell viability and apoptosis. Results. miR-26b is commonly downregulated in HCC cell lines compared with the LO2 cell line. In contrast, the Mcl-1 expression is upregulated in HCC cell lines. Bioinformatic analysis identified a putative target site in the Mcl-1 mRNA for miR-26b and luciferase reporter assay showed that miR-26b directly targeted the 3′-UTR (3′-Untranslated Regions) of Mcl-1 mRNA. Transfection of miR-26b mimics suppressed Mcl-1 expression in HCC cells and sensitized the cancer cells to TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) cytotoxicity. In addition, transfection of HCC cells with Mcl-1 expression plasmid abolished the sensitization effect of miR-26b to TRAIL-inducing apoptosis. Conclusions. Our study showed that miR-26b was a negative regulator of Mcl-1 gene and sensitized TRAIL-inducing apoptosis in HCC cells, suggesting that the miR-26b-Mcl-1 pathway might be a novel target for the treatment of HCC.

MicroRNAs as mediators and communicators between cancer cells and the tumor microenvironment

Cancer cells grow in an environment comprised of multiple components that support tumor growth and contribute to therapy resistance. Major cell types in the tumor microenvironment are fibroblasts, endothelial cells and infiltrating immune cells all of which communicate with cancer cells. One way that these cell types promote cancer progression is by altering the expression of microRNAs (miRNAs), small noncoding RNAs that negatively regulate protein expression, either in the cancer cells or in the associated normal cells. Changes in miRNA expression can be brought about by direct interaction between the stromal cells and cancer cells, by paracrine factors secreted by any of the cell types or even through direct communication between cells through secreted miRNAs. Understanding the role of miRNAs in the complex interactions between the tumor and cells in its microenvironment is necessary if we are to understand tumor progression and devise new treatments.

MicroRNA-26b inhibits metastasis of osteosarcoma via targeting CTGF and Smad1

Downregulation of miR-26b has been found in various cancers, but it has never been investigated in osteosarcoma. In this study, we demonstrated downregulation of miR-26b in osteosarcoma tissues, negatively correlated with the expression of connective tissue growth factor (CTGF) and Smad1. Luciferase reporter assay confirmed the interaction of miR-26b with the 3' untranslated regions (UTRs) of CTGF and Smad1. Transfection of miR-26b in osteosarcoma cells suppressed the expression of CTGF and Smad1, suggesting CTGF and Smad1 as direct targets of miR-26b. Overexpression of miR-26b inhibited the migration of osteosarcoma cells, which was reversed by overexpression of CTGF or Smad1. Knockdown of CTGF by small interfering RNA (siRNA) interference blocked the activation of Smad1, ERK1/2, and MMP2, which was opposite to the overexpression of CTGF. Differently, Smad1 did not significantly affect CTGF level, but mediated ERK1/2 phosphorylation and MMP2 activation. Furthermore, miR-26b inhibited lung metastasis of osteosarcoma in vivo. Our data indicated that downregulation of miR-26b in osteosarcoma elevated the levels of CTGF and Smad1, facilitating osteosarcoma metastasis.

miR-26b inhibits proliferation, migration, invasion and apoptosis induction via the downregulation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 driven glycolysis in osteosarcoma cells

MicroRNAs (miRNAs) are differentially expressed and play crucial roles in cancer development and progression. Elevated glycolysis provides survival advantage and metastatic phenotype. Emerging evidence indicates that glycolysis in cancers can be regulated by miRNAs. In the present study, the role of miR-26b in the proliferation, invasion and glycolytic phenotype of osteosarcoma (OS) cells was investigated. miR-26b was reported to be downregulated in OS tissues, however, the effect of miR-26b on OS has not been distinctly evaluated. The present study therefore investigated the miR-26b sensitivity mechanism in OS. To determine the role of miR-26, we reinstated its expression in the U2OS OS cell line through transfection with miR-26b mimics and examined the effects on cell proliferation, migration, invasion, cell cycle progression and glycolytic parameters. The computational prediction tool was employed to identify the molecular target of miR-26b and was confirmed experimentally. Restoration of miR-26b expression inhibited cell proliferation, migration and invasion, arrested cell cycle progression, and induced cell apoptosis accompanied by the downregulation of glycolytic phenotype. Moreover, the binding site for miR-26b was predicted in the 3'UTR of gene 6-phosphofructo-2-kinase/fructose‑2,6-bisphosphatase-3 (PFKFB3), suggesting a role for miR-26b in metabolic alteration in OS cells. Further studies showed that overexpression of miR-26b repressed PFKFB3 mRNA and protein levels followed by modulation of the expression of glycolytic components (LDHA, GLUT-1) and markers of invasion and cell cycle such as MMP-9, MMP-2, cyclin D1 and p27. Collectively, the data suggested the tumor suppressive role of miR-26b which functions by targeting the glycolytic metabolism in OS cells, and providing a possible therapeutic strategy for OS patients by targeting miRNA expression.

MicroRNA-26b functions as a proapoptotic factor in porcine follicular Granulosa cells by targeting Sma-and Mad-related protein 4

Sma- and Mad-related protein 4 (SMAD4) is the central mediator of the transforming growth factor beta signaling pathway and is closely related to mammalian reproductive ability and the development of ovarian follicles. However, little is currently known about the role of SMAD4 in mammalian follicular granulosa cell (GC) apoptosis or its regulation by miRNAs. Here, we found that the porcine SMAD4 protein was expressed at high levels in GCs and oocytes from primary, preantral, and antral follicles, and only slightly expressed in theca cells; its expression level was down-regulated in apoptotic ovarian GCs, suggesting that SMAD4 may be involved in ovary development and selection. Overexpression and knockdown of SMAD4 increased the proliferation and apoptosis of cultured porcine GCs, respectively. In addition, the use of miRNA mimics and luciferase reporter assays revealed that miRNA-26b (miR-26b) functions as a proapoptotic factor in porcine follicular GCs by targeting the 3'-untranslated region of the SMAD4 gene. Overexpression of miR-26b in follicular GCs suppressed SMAD4 mRNA and protein levels, resulting in down-regulation of the antiapoptotic BCL-2 gene and the promotion of GC apoptosis. Furthermore, transforming growth factor beta 1 (TGF-beta1) down-regulates miR-26b expression in porcine GCs. Taken together, these data suggest that SMAD4 plays a critical role in porcine follicular GC apoptosis and follicular atresia and that miR-26b may have a proapoptotic role in GCs by regulating the expression of SMAD4 in the transforming growth factor beta signaling pathway.

MiRNA-26b inhibits the proliferation, migration, and epithelial-mesenchymal transition of lens epithelial cells

MicroRNAs (miRNAs) are a class of small endogenous gene regulators that play important roles in various developmental and pathological processes. However, little is known about the precise identity and functions of miR-26b in posterior capsule opacification (PCO). In this study, we report that the expression of miR-26b is decreased in human PCO-attached lens epithelial cells (LECs) and SRA01/04 cells in the presence of TGF-β2. Overexpression of miR-26b inhibited the proliferation of LECs based on MTT assays and BrdU incorporation assays. In addition, the overexpression of miR-26b inhibited the migration ability of LECs, as shown by wound-healing and transwell migration assays. The overexpression of miR-26b increased the level of the lens epithelial marker E-cadherin and reduced the levels of mesenchymal-related proteins, such as fibronectin, a-SMA, and type I collagen, in SRA01/04 cells in the presence of TGF-β2. Furthermore, the upregulation of E-cadherin and downregulation of mesenchymal-related proteins were induced in human PCO-attached LECs transfected with miR-26b mimics. We further demonstrated that Smad4 and COX-2 are targets of miR-26b in LECs using luciferase reporter assays. These data reveal that miR-26b can inhibit the proliferation, migration, and EMT of lens epithelial cells, and restoration of miRNA-26b may be a potential, novel therapeutic target for the prevention and treatment of posterior capsule opacification.

MicroRNA-26b inhibits hepatitis B virus transcription and replication by targeting the host factor CHORDC1 protein

Hepatitis B virus (HBV) causes acute and chronic hepatitis in humans, and HBV infection is a major threat to global health. HBV replication is regulated by a series of host factors, including microRNAs (miRNAs), which are highly conserved small noncoding RNAs that participate in a variety of physiological and pathological processes. Here, we report that a chemically synthesized mimic of miR-26b inhibited HBV antigen expression, transcription, and replication, whereas antisense knockdown of endogenous miR-26b enhanced HBV replication in HepG2 cells. Overexpression and knockdown experiments showed that miR-26b significantly decreased HBV enhancer/promoter activities. We identified the cysteine- and histidine-rich domain containing 1 (CHORDC1) as a novel host factor target of miR-26b. CHORDC1 protein but not mRNA was markedly decreased by miR-26b overexpression via base-pairing with complementary sequences in the 3'UTR of its mRNA. Overexpression and knockdown studies showed that CHORDC1 increased viral antigen expression, transcription, and replication by elevating HBV enhancer/promoter activities. Conversely, HBV infection suppressed miR-26b expression and increased CHORDC1 protein levels in human liver cells. Another mature miRNA of the hsa-miR-26 family, miR-26a, had a similar function as miR-26b in targeting CHORDC1 and affecting HBV production. These results suggest that suppression of miR-26b expression up-regulates its target gene CHORDC1, which increases HBV enhancer/promoter activities and promotes viral transcription, gene expression, and replication. Our study could provide new insights into miRNA expression and the persistence of HBV infection.

MicroRNA-106b in cancer-associated fibroblasts from gastric cancer promotes cell migration and invasion by targeting PTEN

It is well established that the interaction between cancer cells and microenvironment has a critical role in tumor development, but the roles of miRNAs in this interaction are rarely known. Here, we have shown that miR-106b is up-regulated in cancer associated fibroblasts compared with normal fibroblasts established from patients with gastric cancer, the expression level of miR-106b is associated with poor prognosis of patients, and CAFs with down-regulated miR-106b could significantly inhibit gastric cancer cell migration and invasion by targeting PTEN. Taken together, these data suggest that miR-106b might be a novel candidate target for the treatment of gastric cancer.

C-terminal tensin-like (CTEN): a promising biomarker and target for cancer

C-terminal tensin-like (cten, also known as tensin4, TNS4) is a member of the tensin family. Cten protein, like the other three tensin family members, localizes to focal adhesion sites but only shares sequence homology with other tensins at its C-terminal region, which contains the SH2 and PTB domains. Cten is abundantly expressed in normal prostate and placenta and is down-regulated in prostate cancer. However, overexpression of cten frequently associates with tumors derived from breast, colon, lung, stomach, skin and pancreas. A variety of cancer-associated growth factors and cytokines induce cten expression. Up-regulated cten promotes cell motility, prolongs epidermal growth factor receptor signaling, and enhances tumorigenicity. Emerging findings suggest that cten is a promising biomarker and therapeutic target for various cancers.