MicroRNA-21 Promotes Glioblastoma Tumorigenesis by Down-regulating Insulin-like Growth Factor-binding Protein-3 (IGFBP3)

Despite advances in surgery, imaging, chemotherapy, and radiation, patients with glioblastoma multiforme (GBM), the most common histological subtype of glioma, have an especially dismal prognosis; >70% of GBM patients die within 2 years of diagnosis. In many human cancers, the microRNA miR-21 is overexpressed, and accumulating evidence indicates that it functions as an oncogene. Here, we report that miR-21 is overexpressed in human GBM cell lines and tumor tissue. Moreover, miR-21 expression in GBM patient samples is inversely correlated with patient survival. Knockdown of miR-21 in GBM cells inhibited cell proliferation in vitro and markedly inhibited tumor formation in vivo. A number of known miR-21 targets have been identified previously. By microarray analysis, we identified and validated insulin-like growth factor (IGF)-binding protein-3 (IGFBP3) as a novel miR-21 target gene. Overexpression of IGFBP3 in glioma cells inhibited cell proliferation in vitro and inhibited tumor formation of glioma xenografts in vivo. The critical role that IGFBP3 plays in miR-21-mediated actions was demonstrated by a rescue experiment, in which IGFBP3 knockdown in miR-21KD glioblastoma cells restored tumorigenesis. Examination of tumors from GBM patients showed that there was an inverse relationship between IGFBP3 and miR-21 expression and that increased IGFBP3 expression correlated with better patient survival. Our results identify IGFBP3 as a novel miR-21 target gene in glioblastoma and suggest that the oncogenic miRNA miR-21 down-regulates the expression of IGFBP3, which acts as a tumor suppressor in human glioblastoma.     

The role of microRNA-26b in human adipocyte differentiation and proliferation

Recent findings indicate that microRNAs (miRNAs) are involved in the regulatory network of adipogenesis and obesity. Thus far, only a few human miRNAs are known to function as adipogenic regulators, fanning interest in studies on the functional role of miRNAs during adipogenesis in humans. In a previous study, we used a microarray to assess miRNA expression during human preadipocyte differentiation. We found that expression of the miR-26b was increased in mature adipocytes. MiR-26b is an intronic miRNA located in the intron of CTDSP1 (carboxy terminal domain, RNA polymerase II, polypeptide A, small phosphatase 1). Target prediction and Renilla luciferase analyses revealed the phosphatase and tensin homolog gene (PTEN) as a putative target gene. In this study, we found that miR-26b was gradually upregulated during adipocyte differentiation. To understand the roles of miR-26b in adipogenesis, we adopted a loss-of-function approach to silence miR-26b stably in human preadipocytes. We found that miR-26b inhibition effectively suppressed adipocyte differentiation, as evidenced by decreased lipid droplets and the ability of miR-26b to decrease mRNA levels of adipocyte-specific molecular markers and triglyceride accumulation. Furthermore, the cell growth assay revealed that miR-26b inhibition promoted proliferation. Nevertheless, it had no effect on apoptosis. Taken together, these data indicate that miR-26b may be involved in adipogenesis and could be targeted for therapeutic intervention in obesity.     

miRNA-182 and the regulation of the glioblastoma phenotype - toward miRNA-based precision therapeutics

Glioblastoma (GBM) is an incurable cancer, with survival rates of just 14-16 months after diagnosis.¹ Functional genomics have identified numerous genetic events involved in GBM development. One of these, the deregulation of microRNAs (miRNAs), has been attracting increasing attention due to the multiple biologic processes that individual miRNAs influence. Our group has been studying the role of miR-182 in GBM progression, therapy resistance, and its potential as GBM therapeutic. Oncogenomic analyses revealed that miR-182 is the only miRNA, out of 470 miRNAs profiled by The Cancer Genome Atlas (TCGA) program, which is associated with favorable patient prognosis, neuro-developmental context, temozolomide (TMZ) susceptibility, and most significantly expressed in the least aggressive oligoneural subclass of GBM. miR-182 sensitized glioma cells to TMZ-induced apoptosis, promoted glioma initiating cell (GIC) differentiation, and reduced tumor cell proliferation via knockdown of Bcl2L12, c-Met and HIF2A.² To deliver miR-182 to intracranial gliomas, we have characterized Spherical Nucleic Acids covalently functionalized with miR-182 sequences (182-SNAs). Upon systemic administration, 182-SNAs crossed the blood-brain/blood-tumor barrier (BBB/BTB), reduced tumor burden, and increased animal subject survival.^2-4 Thus, miR-182-based SNAs represent a tool for systemic delivery of miRNAs and a novel approach for the precision treatment of malignant brain cancers.     

MiR-328 Expression Is Decreased in High-Grade Gliomas and Is Associated with Worse Survival in Primary Glioblastoma

MicroRNAs, a group of small endogenous, noncoding RNAs, are aberrantly expressed in many human cancers and can act as oncogene or anti-oncogene. Recent evidence suggests that some miRNAs have prognostic value for tumors. MiR-328 is known as a tumor suppressor; however, its relationship with the clinicopathological features of glioblastoma (GBM) and its prognostic value has yet not been investigated. We found that expression of miR-328 was significantly decreased both in anaplastic and GBM cohorts and that low miR-328 expression also conferred poor survival in primary GBM (PGBM) patients. MiR-328 might, therefore, serve as an independent prognostic marker. Furthermore, expression profiles of miR-328-associated mRNAs were established via microarrays for 60 GBM samples. The ontology of the miR-328-associated genes was then analyzed, which identified gene sets tightly related to cell mitosis. In addition, ectopic expression of miR-328 inhibited U87 cell proliferation and induced U87 cell cycle arrest. In conclusion, this is the first report showing that miR-328 is associated with patient’s survival time and that miR-328 might serve as an independent prognostic biomarker for GBM.     

Comparative profiling of miRNA expression of lung adenocarcinoma cells in two-dimensional and three-dimensional cultures

Three-dimensional organotypic culture using reconstituted basement membrane matrix (rBM 3-D) is an invaluable tool to characterize morphogenesis of epithelial cells and to elucidate the tumor-modulating actions of extracellular matrix. microRNAs (miRNA) are a novel class of tumor modulating genes. A substantial amount of investigation of miRNAs in cancer is carried out using monolayer 2-D culture on plastic substratum, which lacks a consideration of the matrix-mediated regulation of miRNAs. In the current study we compared the expression of miRNAs in rBM 3-D and 2-D cultures of two lung adenocarcinoma cell lines. Our findings revealed a profound difference in miRNA profiles between 2-D and rBM 3-D cultures of lung adenocarcinoma cells. The rBM 3-D culture-specific miRNA profile was highlighted with higher expression of the tumor suppressive miRNAs (i.e., miR-200 family) and lower expression of the oncogenic miRNAs (i.e., miR-17–92 cluster and miR-21) than that of 2-D culture. Moreover, the expression pattern of miR-17, miR-21, and miR-200a in rBM 3-D culture correlated with the expression of their targets and acinar morphogenesis, a differentiation behavior of lung epithelial cells in rBM 3-D culture. Over-expression of miR-21 suppressed its target PTEN and disrupted acinar morphogenesis. In summary, we provide the first miRNA profile of lung adenocarcinoma cells in rBM 3-D culture with respect to acinar morphogenesis. These results indicate that rBM 3-D culture is essential to a comprehensive understanding of the miRNA biology in lung epithelial cells pertinent to lung adenocarcinoma.     

MicroRNA-4731-5p delivered by AD-mesenchymal stem cells induces cell cycle arrest and apoptosis in glioblastoma

Glioblastoma multiforme (GBM) exhibits the most malignant brain tumor with very poor prognosis. MicroRNAs (miRNAs) are regulatory factors that can downregulate the expression of multiple genes. Several miRNAs acting as tumor-suppressor genes have been identified so far. The delivery of miRNA by mesenchymal stem cell (MSC) due to their ability to specifically target tumors is a new, hopeful therapeutic approach for glioblastoma. The objective of our study is the investigation of the effect of lentivirus-mediated microRNA-4731 (miR-4731) genetic manipulated adipose-derived (AD)-MSC on GBM. The downregulation of miR-4731 in human GBM tumor was detected using the GEO dataset. To evaluate the function of miR-4731, we overexpressed miR-4731 using lentiviral vectors in U-87 and U-251 GBM cell lines. The effects of miR-4731 on cell proliferation and cell cycle of glioma cells were analyzed by wound test and flow-cytometry assay. miR-4731 inhibited the proliferation of GBM cancer cells. Coculturing was used to study the antiproliferative effect of miR-4731-AD-MSCs on GBM cell lines. Direct and indirect coculture of GBM cell lines with miR-4731-AD-MSCs induced cell cycle arrest and apoptosis. Our findings suggest that AD-MSCs expressing miR-4731 have favorable antitumor characteristics and should be further explored in future glioma therapy.     

MicroRNA-421 functions as an oncogenic miRNA in biliary tract cancer through down-regulating farnesoid X receptor expression

MicroRNAs (miRNAs) are involved in the development of most cancers. However, few studies have been conducted to determine their relationship to biliary tract cancer (BTC). Farnesoid X receptor (FXR) has been reported to be a tumor suppressor for hepatocellular carcinoma and breast cancer; but few studies have focused on its correlation with BTC. In this study, we identified miR-421 as a potential regulator of FXR expression. We found that their expression amount was inversely correlated as FXR was aberrantly down-regulated in both primary tumor specimens and cell lines; while miR-421 was significantly up-regulated. Ectopic expression of miR-421 significantly decreased FXR protein concentration in BTC cells and promoted cell proliferation, colony formation and migration in vitro. Furthermore, a decrease in miR-421 expression induced G₀/G₁ cell cycle arrest. In conclusion, our study identified microRNA-421 functions as an oncomiR in BTC by targeting FXR. This finding may provide a novel therapeutic strategy for treatment of biliary tract cancer.     

Role of microRNA-26b in glioma development and its mediated regulation on EphA2

Background

MicroRNAs (miRNAs) are short, non-coding RNAs that regulate the expression of multiple target genes. Deregulation of miRNAs is common in human tumorigenesis. Low level expression of miR-26b has been found in glioma cells. However, its underlying mechanism of action has not been determined.

Methodology/Principal Findings

Real-time PCR was employed to measure the expression level of miR-26b in glioma patients and cells. The level of miR-26b was inversely correlated with the grade of glioma. Ectopic expression of miR-26b inhibited the proliferation, migration and invasion of human glioma cells. A binding site for miR-26b was identified in the 3′UTR of EphA2. Over-expression of miR-26b in glioma cells repressed the endogenous level of EphA2 protein. Vasculogenic mimicry (VM) experiments were performed to further confirm the effects of miR-26b on the regulation of EphA2, and the results showed that miR-26b inhibited the VM processes which regulated by EphA2.

Significance

This study demonstrated that miR-26b may act as a tumor suppressor in glioma and it directly regulates EphA2 expression. EphA2 is a direct target of miR-26b, and the down-regulation of EphA2 mediated by miR-26b is dependent on the binding of miR-26b to a specific response element of microRNA in the 3′UTR region of EphA2 mRNA.     

MiRNA-26b regulates the expression of cyclooxygenase-2 in desferrioxamine-treated CNE cells

Here we report that miR-26b is involved in COX-2 overexpression in desferrioxamine (DFOM)-treated carcinoma of nasopharyngeal epithelial (CNE) cells. The level of miR-26b in DFOM-treated CNE cells is inversely proportional to the expression level of the COX-2 protein. Overexpression of miR-26b in DFOM-treated CNE cells inhibits cell proliferation. A luciferase reporter gene experiment suggests that the 3′ untranslated region of COX-2 carries a binding site for miR-26b. Overexpression of miR-26b marginally reduces the levels of COX-2 protein in DFOM-treated CNE cells. Moreover, knockdown of COX-2 expression had a similar effect to overexpression of miR-26b. Taken together, these results suggest that miR-26b regulates COX-2 expression in DFOM-treated cells.     

Up-Regulation of microRNA-183 Promotes Cell Proliferation and Invasion in Glioma By Directly Targeting NEFL

Glioblastoma multiforme (GBM) is the most common and lethal type of primary malignant brain tumor. In recent years, increasing reports suggest that discovery of microRNAs (miRNAs) might provide a novel therapeutical target for human cancers, including GBM. The expression and roles of microRNA-183 (miR-183) has been explored in several types of human cancers, including in GBM, and plays important roles in tumor initiation and progression. However, its biological functions in GBM remain largely unknown. In this study, we demonstrated that miR-183 was significantly up-regulated in astrocytoma tissues and glioblastoma cell lines. Introduction of miR-183 mimics into U251 cells could promoted, while its antisense oligos inhibited cell proliferation and invasion. Moreover, we identified neurofilament light polypeptide (NEFL) as a novel target gene of miR-183. The expression levels of NEFL are inversely correlated with that of miR-183 in human astrocytoma clinical specimens. In addition, NEFL-siRNA could significantly attenuate the inhibitory effects of knockdown miR-183 on the proliferation and invasion of U251 cells via mTOR signaling pathway. Overall, This study revealed that miR-183 promotes glioma cell proliferation by targeting NEFL, and also demonstrated that miR-183 could be a potential target for GBM treatment.     

Suppression of tumorigenicity by MicroRNA-138 through inhibition of EZH2-CDK4/6-pRb-E2F1 signal loop in glioblastoma multiforme

Deregulation of microRNAs (miRNAs) is implicated in tumor progression. We attempt to indentify the tumor suppressive miRNA not only down-regulated in glioblastoma multiforme (GBM) but also potent to inhibit the oncogene EZH2, and then investigate the biological function and pathophysiologic role of the candidate miRNA in GBM. In this study, we show that miRNA-138 is reduced in both GBM clinical specimens and cell lines, and is effective to inhibit EZH2 expression. Moreover, high levels of miR-138 are associated with long overall and progression-free survival of GBM patients from The Cancer Genome Atlas dataset (TCGA) data portal. Ectopic expression of miRNA-138 effectively inhibits GBM cell proliferation in vitro and tumorigenicity in vivo through inducing cell cycles G1/S arrest. Mechanism investigation reveals that miRNA-138 acquires tumor inhibition through directly targeting EZH2, CDK6, E2F2 and E2F3. Moreover, an EZH2-mediated signal loop, EZH2-CDK4/6-pRb-E2F1, is probably involved in GBM tumorigenicity, and this loop can be blocked by miRNA-138. Additionally, miRNA-138 negatively correlates to mRNA levels of EZH2 and CDK6 among GBM clinical samples from both TCGA and our small amount datasets. In conclusion, our data demonstrate a tumor suppressive role of miRNA-138 in GBM tumorigenicity, suggesting a potential application in GBM therapy.