Exosomal lncRNA­ATB activates astrocytes that promote glioma cell invasion.

Glioma invasion is a main cause of a poor prognosis and relapse in patients suffering from the disease. However, the molecular mechanisms responsible for glioma cell invasion remain poorly understood. In this study, the characteristics of exosomes were identified using electron microscope (TEM), and western blot analysis. The potential mechanism of long non­coding RNA (lncRNA) activated by TGF­ß (lncRNA­ATB) was demonstrated using luciferase reporter assays and RNA immunoprecipitation. We found that glioma cell­derived exosomes promoted the activation of astrocytes and had the ability to shuttle long non­coding RNA (lncRNA) activated by TGF­ß (lncRNA­ATB) to astrocytes. More importantly, lncRNA­ATB activated astrocytes through the suppression of microRNA (miRNA or miR)­204­3p in an Argonaute 2 (Ago2)­dependent manner. Furthermore, astrocytes activated by lncRNA­ATB in turn promoted the migration and invasion of glioma cells. Taken together, the findings of this study suggest that lncRNA­ATB may play an important role in modulating glioma microenvironment through exosomes. Thus, a better understanding of this process may provide implications for the prevention of highly invasive glioma.

Long non-coding RNA SPRY4-IT1 promotes the proliferation and invasion of U251 cells through upregulation of SKA2.

The long non-coding RNA SPRY4-intronic transcript 1 (SPRY4-IT1) has been shown to promote the progression of cancer; however, the role of SPRY4-IT1 in glioma remains unclear. The present study demonstrated that SPRY4-IT1 expression was markedly increased in glioma tissues and cells compared with normal brain tissues, whereas knockdown of SPRY4-IT1 inhibited cell proliferation, migration, and invasion in U251 cells. Spindle and kinetochore associated complex subunit 2 (SKA2) was found to be a target of SPRY4-IT1 and was downregulated by SPRY4-IT1-knockdown. Additionally, SPRY4-IT1 expression was positively correlated with SKA2 in glioma tissues. To the best of our knowledge, the present study provides the first demonstration that SKA2 may have an oncogenic role in U251 cells. These results indicate that SPRY4-IT1 may serve a notable role in the molecular etiology of glioma and represents a potential target in glioma therapy.

TGF-ß-mediated repression of MST1 by DNMT1 promotes glioma malignancy.

Human gliomas are related to high rates of morbidity and mortality. TGF-ß promotes the growth of glioma cells, and correlate with the degree of malignancy of human gliomas. However, the molecular mechanisms involved in the malignant function of TGF-ß are not fully elucidated. Here, we showed that TGF-ß induced the downregulation of MST1 expression in U87 and U251 glioma cells. Treatment of glioma cells with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-AzadC) prevented the loss of MST1 expression. Addition of 5-AzadC also reduced the TGF-ß-stimulated proliferation, migration and invasiveness of glioma cells. Furthermore, Knockdown of DNMT1 upregulated MST1 expression in gliomas cells. In addition, the inhibition of DNMT1 blocked TGF-ß-induced proliferation, migration and invasiveness in glioma cells. These results suggest that TGF-ß promotes glioma malignancy through DNMT1-mediated loss of MST1 expression.

Long non-coding RNA ATB promotes glioma malignancy by negatively regulating miR-200a.

BACKGROUND: Glioma is one of the most common and aggressive primary malignant tumor in the brain. Accumulating evidences indicated that aberrantly expressed non-coding RNAs (ncRNAs), including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), contribute to tumorigenesis. However, potential mechanisms between lncRNAs and miRNAs in glioma remain largely unknown. METHODS: Long non-coding RNA activated by TGF-ß (LncRNA-ATB) expression in glioma tissues and cells was quantified by quantitative reverse transcription-PCR. Glioma cell lines U251 and A172 were transfected with sh-ATB, miR-200a mimics, miR-200a inhibitors, after we assayed the cell phenotype and expression of the relevant molecules. Dual-luciferase reporter assay, RIP and a xenograft mouse model were used to examine the expression of sh-ATB and its target gene miR-200a. RESULTS: ATB is abnormally up-regulated both in glioma tissues and cell lines compared with normal brain tissues, and glioma patients with high ATB expression had shorter overall survival time. Knockdown of ATB significantly inhibits glioma malignancy, including cell proliferation, colony formation, migration, invasion in vitro, and the xenograft tumor formation in vivo. In addition, ATB was confirmed to target miR-200a, and miR-200a inhibition reversed the malignant characteristics of ATB knockdown on glioma cells. In particular, ATB may act as a ceRNA, effectively becoming a sink for miR-200a, thereby modulating the derepression of TGF-ß2. CONCLUSIONS: Our findings suggest that ATB plays an oncogenic role of glioma cells by inhibiting miR-200a and facilitating TGF-ß2 in glioma, thereby may represent a potential therapeutic target for the treatment of human glioma.

Epigenetic modification of miR-141 regulates SKA2 by an endogenous 'sponge' HOTAIR in glioma.

Aberrant expression of miR-141 has recently implicated in the occurrence and development of various types of malignant tumors. However whether the involvement of miR-141 in the pathogenesis of glioma remains unknown. Here, we showed that miR-141 was markedly downregulated in glioma tissues and cell lines compared with normal brain tissues, and its expression correlated with the pathological grading. Enforced expression of miR-141 in glioma cells significantly inhibited cell proliferation, migration and invasion, whereas knockdown of miR-141 exerted opposite effect. Mechanistic investigations revealed that HOTAIR might act as an endogenous 'sponge' of miR-141, thereby regulating the derepression of SKA2. Further, we explored the molecular mechanism by which miR-141 expression was regulated, and found that the miR-141 promoter was hypermethylated and that promoter methylation of miR-141 was mediated by DNMT1 in glioma cells. Finally, both overexpression of miR-141 and knockdown of HOTAIR in a mouse model of human glioma resulted in significant reduction of tumor growth in vivo. Collectively, these results suggest that epigenetic modification of miR-141 and the interaction of ceRNA regulatory network will provide a new approach for therapeutics against glioma.

Epigenetic repression of long non-coding RNA MEG3 mediated by DNMT1 represses the p53 pathway in gliomas.

Epigenetic regulation plays a significant role in gliomas. However, how methylation and long non-coding RNA (lncRNA) cooperates to regulate gliomas progression is largely unknown. In this investigation we showed that the downregulation of MEG3 expression due to hypermethylation of MEG3 was observed in gliomas tissues. Treatment of glioma cells with the DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-AzadC) decreased aberrant hypermethylation of the MEG3 promoter and prevented the loss of MEG3 expression. In addition, DNMT1 was involved in MEG3 promoter methylation, and was inversely correlated with MEG3 expression in gliomas. The inhibition of DNMT1 repressed the proliferation, clone formation, and induced apoptosis in glioma cells. Importantly, the inhibition of DNMT1 contributed to the activation of p53 pathways in gliomas cells. These results suggest that DNMT1-mediated MEG3 hypermethylation caused the loss of MEG3 expression, followed by the inhibition of the p53 pathways in gliomas.