Junxia Zhang

Long Non-Coding RNA H19 Promotes Glioma Cell Invasion by Deriving miR-675

H19 RNA has been characterized as an oncogenic long non-coding RNA (lncRNA) in breast and colon cancer. However, the role and function of lncRNA H19 in glioma development remain unclear. In this study, we identified that H19/miR-675 signaling was critical for glioma progression. By analyzing glioma gene expression data sets, we found increased H19 in high grade gliomas. H19 depletion via siRNA inhibited invasion in glioma cells. Further, we found H19 positively correlated with its derivate miR-675 expression and reduction of H19 inhibited miR-675 expression. Bioinformatics and luciferase reporter assays showed that miR-675 modulated Cadherin 13 expression by directly targeting the binding site within the 3′ UTR. Finally, introduction of miR-675 abrogated H19 knockdown-induced cell invasion inhibition in glioma cells. To our knowledge, it is first time to demonstrate that H19 regulates glioma development by deriving miR-675 and provide important clues for understanding the key roles of lncRNA-miRNA functional network in glioma.

HOTAIR, a cell cycle-associated long noncoding RNA and a strong predictor of survival, is preferentially expressed in classical and mesenchymal glioma.

BACKGROUND Long noncoding RNA Hox transcript antisense intergenic RNA (HOTAIR) has been characterized as a negative prognostic factor in breast and colon cancer patients. The clinical significance and function of HOTAIR in glioma remains unclear. METHODS We analyzed the clinical significance of HOTAIR in 3 different glioma cohorts with gene expression data, including correlation with tumor grade, prognosis, and molecular subtype. The function of HOTAIR in glioma was explored by performing gene set enrichment analysis and in vitro and in vivo experiments. RESULTS HOTAIR expression was closely associated with glioma grade and poor prognosis. Multivariate Cox regression analysis revealed that HOTAIR was an independent prognostic factor in glioblastoma multiforme patients. HOTAIR expression correlated with glioma molecular subtype, including those of The Cancer Genome Atlas. HOTAIR was preferentially expressed in the classical and mesenchymal subtypes compared with the neural and proneural subtypes. A gene set enrichment analysis designed to show gene set differences between patients with high and low HOTAIR expression indicated that HOTAIR expression was associated with gene sets involved in cell cycle progression. HOTAIR reduction induced colony formation suppression, cell cycle G0/G1 arrest, and orthotopic tumor growth inhibition. CONCLUSION Our data establish that HOTAIR is an important long noncoding RNA that primarily serves as a prognostic factor for glioma patient survival, as well as a biomarker for identifying glioma molecular subtypes, a critical regulator of cell cycle progression.

MiR-125b is critical for the suppression of human U251 glioma stem cell proliferation

Stem cells are unique in their ability to self-renew and maintain tissue homoeostasis by differentiating into different cell types to replace aged or damaged cells. The key characteristic of the stem cell is its capacity to divide for long periods of time. MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. miR-125b, one of neuronal miRNAs, recently was found to be necessary for stem cell fission to bypass the normal G1/S checkpoint and make stem cells insensitive to chemotherapy signals, which normally stop the cell cycle at the G1/S transition. Given the insensitivity of gliomas to chemotherapy and the hypothesis that glioma stem cells cause resistance to drug therapy, exploring the functions and mechanisms of miR-125b in glioma stem cells would be valuable. In this study, we found that miR-125b was downregulated in human U251 glioma stem cells, therefore suggesting that its upregulation can lead to the growth inhibition of U251 glioma stem cells in vitro. Further research on the mechanism demonstrated that inhibition of miR-125b-induced U251 glioma stem cell proliferation was due to cell cycle arrest at the G1/S transition and involved the cell cycle regulated proteins CDK6 and CDC25A; miR-125b overexpression decreased CDK6 and CDC25A expression. These findings underscore the potential of miR-125b to regulate the proliferation of U251 glioma stem cells through the cell cycle regulated proteins CDK6 and CDC25A.

MicroRNA-125b-2 confers human glioblastoma stem cells resistance to temozolomide through the mitochondrial pathway of apoptosis

MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. miR-125b, one of the neuronal miRNAs, was recently found to be necessary for stem cell fission and for making stem cells insensitive to chemotherapy signals. Temozolomide (TMZ) is a promising chemotherapeutic agent for treating glioblastomas. However, resistance develops quickly and with a high frequency. Given the insensitivity of some glioblastomas to TMZ and the hypothesis that glioma stem cells cause resistance to drug therapy, exploring the functions and mechanisms of miR-125b action on TMZ-treated glioblastoma stem cells would be valuable. In this study, we found that miR-125b-2 is overexpressed in glioblastoma multiforme tissues and the corresponding stem cells (GBMSC); downregulation of miR-125b-2 expression in GBMSC could allow TMZ to induce GBMSC apoptosis. Additionally, the expression of the anti-apoptotic protein Bcl-2 was decreased after the TMZ+miR-125b-2 inhibitor treatment, while the expression of the proapoptotic protein Bax was increased. Further research demonstrated that the induction of apoptosis in GBMSC is also associated with increased cytochrome c release from mitochondria, induction of Apaf-1, activation of caspase-3 and poly-ADP-ribose polymerase (PARP). Taken together, these results suggest that miR-125b-2 overexpression might confer glioblastoma stem cells resistance to TMZ.

High level of miR-221/222 confers increased cell invasion and poor prognosis in glioma

BackgroundMiR-221 and miR-222 (miR-221/222), upregulated in gliomas, can regulate glioma cell cycle progression and apoptosis, respectively. However, the association of miR-221/222 with glioma cell invasion and survival remains unknown.MethodsInvasion capability of miR-221/222 was detected by mutiple analyses, including diffusion tensor imaging (DTI), transwell, wound healing and nude mouse tumor xenograft model assay. Further, the target of miR-221/222 was determined by luciferase reporter, western blot and gene rescue assay. The association of miR-221/222 with outcome was examined in fifty glioma patients.ResultsMiR-221/222 expression was significantly increased in high-grade gliomas compared with low-grade gliomas, and positively correlated with the degree of glioma infiltration. Over-expression of miR-221/222 increased cell invasion, whereas knockdown of miR-221/222 decreased cell invasion via modulating the levels of the target, TIMP3. Introduction of a TIMP3 cDNA lacking 3’ UTR abrogated miR-221/222-induced cell invasion. In addition, knockdown of miR-221/222 increased TIMP3 expression and considerably inhibited tumor growth in a xenograft model. Finally, the increased level of miR-221/222 expression in high-grade gliomas confers poorer overall survival.ConclusionsThe present data indicate that miR-221 and miR-222 directly regulate cell invasion by targeting TIMP3 and act as prognostic factors for glioma patients.

MicroRNA roles in beta-catenin pathway

Abstractβ-catenin, a key factor in the Wnt signaling pathway, has essential functions in the regulation of cell growth and differentiation. Aberrant β-catenin signaling has been linked to various disease pathologies, including an important role in tumorigenesis. Here, we review the regulation of the Wnt signaling pathway as it relates to β-catenin signaling in tumorigenesis, with particular focus on the role of microRNAs. Finally, we discuss the potential of β-catenin targeted therapeutics for cancer treatment.

Molecular classification of gliomas based on whole genome gene expression: a systematic report of 225 samples from the Chinese Glioma Cooperative Group

Defining glioma subtypes based on objective genetic and molecular signatures may allow for a more rational, patient-specific approach to molecularly targeted therapy. However, prior studies attempting to classify glioma subtypes have given conflicting results. We aim to complement and validate the existing molecular classification system on a large number of samples from an East Asian population. A total of 225 samples from Chinese patients was selected for whole genome gene expression profiling. Consensus clustering was applied. Three major groups of gliomas were identified (referred to as G1, G2, and G3). The G1 subgroup correlates with a good clinical outcome, young age, and extremely high frequency of IDH1 mutations. Relative to the G1 subgroup, the G3 subgroup is correlated with a poorer clinical outcome, older age, and a very low rate of mutations in the IDH1 gene. Correlations of the G2 subgroup with respect to clinical outcome, age, and IDH1 mutation fall between the G1 and G3 subgroups. In addition, the G2 subtype was associated with a higher percentage of loss of 1p/19q when compared with G1 and G3 subtypes. Furthermore, our classification scheme was validated on 2 independent datasets derived from the cancer genome atlas (TCGA) and Rembrandt. With use of the TCGA classification system, proneural, neural, and mesenchymal, but not classical subtype, associated gene signatures were clearly defined. In summary, our results reveal that 3 main subtypes stably exist in Chinese patients with glioma. Our classification scheme may reflect the clinical and genetic alterations more clearly. Classical subtype-associated gene signature was not found in our dataset.

VHL regulates the effects of miR-23b on glioma survival and invasion via suppression of HIF-1α/VEGF and β-catenin/Tcf-4 signaling

Aberrant microRNA expression has been implicated in the development of human cancers. Here, we investigated the oncogenic significance and function of miR-23b in glioma. We identified that the expression of miR-23b was elevated in both glioma samples and glioma cells, indicated by real-time polymerase chain reaction analyses. Down-regulation of miR-23b triggered growth inhibition, induced apoptosis, and suppressed invasion of glioma in vitro. Luciferase assay and Western blot analysis revealed that VHL is a direct target of miR-23b. Restoring expression of VHL inhibited glioma proliferation and invasion. Mechanistic investigation revealed that miR-23b deletion decreased HIF-1α/VEGF expression and suppressed β-catenin/Tcf-4 transcription activity by targeting VHL. Furthermore, expression of VHL was inversely correlated with miR-23b in glioma samples and was predictive of patient survival in a retrospective analysis. Therefore, we demonstrated that downregulation of miR-23b suppressed tumor survival through targeting VHL, leading to the inhibition of β-catenin/Tcf-4 and HIF-1α/VEGF signaling pathways.

Overexpression of osteopontin induces angiogenesis of endothelial progenitor cells via the avβ3/PI3K/AKT/eNOS/NO signaling pathway in glioma cells

Angiogenesis, a hallmark of tumor growth, is regulated by various angiogenic factors. Recent studies have shown that osteopontin (OPN) is a secreted, integrin-binding protein that contributes to glioma progression. However, its effect on the angiogenesis of gliomas is not fully understood. To elucidate the role of OPN in the process of glioma angiogenesis, endothelial progenitor cells (EPCs) were treated with conditioned media of human glioma SHG44 cells overexpressing OPN. Here, we identified that OPN secreted by glioma cells accelerated EPCs angiogenesis in vitro, including proliferation, migration, and tube formation. OPN also induced the activation of AKT and endothelial nitric oxide synthase (eNOS) and increased NO production without affecting the expression of VEGF, VEGFR-1, or VEGFR-2. Moreover, the avβ3 antibody, the PI3-K inhibitor LY294002 and the eNOS inhibitor NMA suppressed the OPN-mediated increase in NO production and angiogenesis in EPCs. Taken together, these results demonstrate that OPN directly stimulates angiogenesis via the avβ3/PI3-K/AKT/eNOS/NO signaling pathway and may play an important role in tumorigenesis by enhancing angiogenesis in gliomas.

A novel cell cycle-associated lncRNA, HOXA11-AS, is transcribed from the 5-prime end of the HOXA transcript and is a biomarker of progression in glioma

The comprehensive lncRNA expression signature in glioma has not yet been fully elucidated. We performed a high-throughput microarray to detect the ncRNA expression profiles of 220 human glioma tissues. Here, we found that a novel lncRNA, HOXA11-AS, was the antisense transcript of the HOX11 gene. It was shown that HOXA11-AS was closely associated with glioma grade and poor prognosis. Multivariate Cox regression analysis revealed that HOXA11-AS was an independent prognostic factor in glioblastoma multiforme patients, and its expression was correlated with the glioma molecular subtypes of the Cancer Genome Atlas. Gene set enrichment analysis indicated that the gene sets most correlated with HOXA11-AS expression were involved in cell cycle progression. Over-expression of the HOXA11-AS transcript promoted cell proliferation in vitro, while knockdown of HOXA11-AS expression repressed cell proliferation via regulation of cell cycle progression. The growth-promoting and growth-inhibiting effects of HOXA11-AS were also demonstrated in a xenograft mouse model. Our data confirms, for the first time, that HOXA11-AS is an important long non-coding RNA that primarily serves as a prognostic factor for glioma patient survival. HOXA11-AS could serve as a biomarker for identifying glioma molecular subtypes and as therapeutic target for glioma patients.