Potential Epigenetic-Based Therapeutic Targets for Glioma

Systematic Profiling of Alternative mRNA Splicing Signature for Predicting Glioblastoma Prognosis

Emerging evidence suggests that alternative splicing (AS) is modified in cancer and is associated with cancer progression. Systematic analysis of AS signature in glioblastoma (GBM) is lacking and is greatly needed. We profiled genome-wide AS events in 498 GBM patients in TCGA using RNA-seq data, and splicing network and prognostic predictor were built by integrated bioinformatics analysis. Among 45,610 AS events in 10,434 genes, we detected 1,829 AS events in 1,311 genes, and 1,667 AS events in 1,146 genes that were significantly associated with overall survival and disease-free survival of GBM patients, respectively. Five potential feature genes, S100A4, ECE2, CAST, ASPH, and LY6K, were discovered after network mining as well as correlation analysis between AS and gene expression, most of which were related to carcinogenesis and development. Multivariate survival model analysis indicated that these five feature genes could classify the prognosis at AS event and gene expression level. This report opens up a new avenue for exploration of the pathogenesis of GBM through AS, thus more precisely guiding clinical treatment and prognosis judgment.

Specific Glioma Prognostic Subtype Distinctions Based on DNA Methylation Patterns

DNA methylation is an important regulator of gene expression and may provide an important basis for effective glioma diagnosis and therapy. Here, we explored specific prognosis subtypes based on DNA methylation status using 653 gliomas from The Cancer Genome Atlas (TCGA) database. Five subgroups were distinguished by consensus clustering using 11,637 cytosines preceding a guanosine (CpGs) that significantly influenced survival. The specific DNA methylation patterns were correlated with age, tumor stage, and prognosis. Additionally, weighted gene co-expression network analysis (WGCNA) analysis of CpG sites revealed that 11 of them could distinguish the samples into high- and low-methylation groups and could classify the prognostic information of samples after cluster analysis of the training set samples using the hierarchical clustering algorithm. Similar results were obtained from the test set and 12 glioma patients. Moreover, in vitro experiments revealed an inverse relationship between methylation level and migration ability or insensitivity to temozolomide (or radiotherapy) of glioma cells based on the final prognostic predictor. Thus, these results suggested that the model constructed in this study could provide guidance for clinicians regarding the prognosis of various epigenetic subtypes.

LncRNA CPS1-IT1 serves as anti-oncogenic role in glioma

Carbamoyl-phosphate synthetase 1 intronic transcript 1 (CPS1-IT1) is identified recently as a novel tumor suppressive long non-coding RNA (lncRNA). However, the expression status and clinical significance of CPS1-IT1 expression remained unknown in glioma. In our study, we observed CPS1-IT1 levels were decreased in glioma tissues and cells compared with paired normal brain tissues and human astrocyte cell line, respectively. Moreover, we analyzed the associations of CPS1-IT1 expression with clinicopathological characteristics, and found low CPS1-IT1 expression was correlated with high World Health Organisation (WHO) grade and large tumor size in glioma patients. Survival analysis showed glioma patients in low CPS1-IT1 expression group had shorter overall survival than those in high CPS1-IT1 expression group, and low CPS1-IT1 expression was an independent prognostic factor for overall survival in glioma patients. The in vitro studies suggested up-regulation of CPS1-IT1 expression resulted in the decrease of proliferation, migration and invasion abilities of glioma cells. In conclusion, CPS1-IT1 plays an anti-oncogenic role in glioma.

Circular RNA circ_001350 regulates glioma cell proliferation, apoptosis, and metastatic properties by acting as a miRNA sponge

Glioma is an aggressive malignancy with increasing incidence and threatens people's health worldwide. Accumulating evidence revealed that circular RNAs (circRNAs) play important functions in cancers. A previous study demonstrated that circ_001350 was elevated in glioma tissue samples than nontumorous tissue specimens screened by high-throughput microarray. The level of circ_001350 in glioma tissue specimens and cell lines was detected by quantitative real-time polymerase chain reaction. The Fisher exact test was carried out to estimate the correlation of circ_001350 level with clinical characteristics. Cell proliferation, apoptosis, and motility abilities were detected using cell counting kit-8, clonogenic, flow cytometry, and transwell experiments, respectively. The potential target of circ_001350 was identified by the luciferase assay. circ_001350 level was significantly enhanced in glioma tissue specimens and cells. Further, elevated expression of circ_001350 was closely linked to patients' clinical severity. Knockdown of circ_001350 could inhibit cell proliferation and metastatic properties and increase apoptotic cells. circ_001350 could directly bind to miR-1236 and regulate its expression to exert oncogenic functions. Collectively, circ_001350 directly sponges miR-1236, thus contributing to malignant progression of glioma.

Low LINC00599 expression is a poor prognostic factor in glioma

LINC00599 has been suggested to be involved in physiological and pathological processes including carcinogenesis. However, the clinical and prognostic significance of LINC00599 in glioma patients and the effect of LINC00599 on glioma cell migration and invasion remain unknown. In our results, we first observe the expression of LINC00599 in 31 types of human cancers including tumor tissues and corresponding normal tissues at The Cancer Genome Atlas (TCGA) database, and found that LINC00599 expression levels were only reduced in lower grade glioma (LGG) tissues and glioblastoma multiforme (GBM) tissues compared with normal brain tissues. Moreover, we confirmed levels of LINC00599 expression were decreased in glioma tissues and cell lines compared with matched adjacent normal tissues and normal human astrocytes (NHAs), respectively. Meanwhile, we found that glioma tissues with WHO III-IV grade exhibited lower levels of LINC00599 expression than glioma tissues with I-II grade. The survival analysis at TCGA data showed low LINC00599 expression was associated with poor disease-free survival and overall survival in glioma patients. In vitro study suggested up-regulation of LINC00599 depressed glioma cell migration and invasion through regulating epithelial–mesenchymal transition (EMT) process. In conclusion, LINC00599 acts as a tumor-suppressing long non-coding RNA (lncRNA) in glioma.

A New Patient-Derived Metastatic Glioblastoma Cell Line: Characterisation and Response to Sodium Selenite Anticancer Agent

Glioblastoma multiform (GBM) tumors are very heterogeneous, organized in a hierarchical pattern, including cancer stem cells (CSC), and are responsible for development, maintenance, and cancer relapse. Therefore, it is relevant to establish new GBM cell lines with CSC characteristics to develop new treatments. A new human GBM cell line, named R2J, was established from the cerebro-spinal fluid (CSF) of a patient affected by GBM with leptomeningeal metastasis. R2J cells exhibits an abnormal karyotype and form self-renewable spheres in a serum-free medium. Original tumor, R2J, cultured in monolayer (2D) and in spheres showed a persistence expression of CD44, CD56 (except in monolayer), EGFR, Ki67, Nestin, and vimentin. The R2J cell line is tumorigenic and possesses CSC properties. We tested in vitro the anticancer effects of sodium selenite (SS) compared to temozolomide TMZ. SS was absorbed by R2J cells, was cytotoxic, induced an oxidative stress, and arrested cell growth in G2M before inducing both necrosis and apoptosis via caspase-3. SS also modified dimethyl-histone-3-lysine-9 (H3K9m2) levels and decreased histone deacetylase (HDAC) activity, suggesting anti-invasiveness potential. This study highlights the value of this new GBM cell line for preclinical modeling of clinically relevant, patient specific GBM and opens a therapeutic window to test SS to target resistant and recurrent GBM.