The role of epigenetic modifications, long-range contacts, enhancers and topologically associating domains in the regulation of glioma grade-specific genes

Regulation of a novel circATP8B4/miR-31-5p/nestin ceRNA crosstalk in proliferation, motility, invasion and radiosensitivity of human glioma cells

Deregulation of circular RNAs (circRNAs) is frequent in human glioma. Although circRNA ATPase phospholipid transporting 8B4 (circATP8B4) is highly expressed in glioma, its precise action in glioma development is still not fully understood. The relationship of microRNA (miR)-31-5p and circATP8B4 or nestin (NES) was predicted by bioinformatic analysis and confirmed by RNA pull-down and Dual-luciferase reporter assays. CircATP8B4, miR-31-5p and NES were quantified by qRT-PCR or western blot. Cell functional behaviors were assessed by EdU, wound-healing and transwell invasion assays. Xenograft model experiments were performed to define circATP8B4's activity in vivo. CircATP8B4, a true circular transcript, was upregulated in human glioma. CircATP8B4 downregulation weakened glioma cell growth, motility, and invasion and facilitated radiosensitivity. Mechanistically, circATP8B4 and NES 3'UTR harbored a shared miR-31-5p pairing site, and circATP8B4 involved the post-transcriptional NES regulation by functioning as a competing endogenous RNA (ceRNA). Furthermore, the miR-31-5p/NES axis participated in circATP8B4's activity in glioma cell proliferation, motility, invasion and radiosensitivity. Additionally, circATP8B4 loss diminished tumor growth and enhanced the anticancer effect of radiotherapy in vivo. We have uncovered an uncharacterized ceRNA cascade, circATP8B4/miR-31-5p/NES axis, underlying glioma development and radiosensitivity. Targeting the ceRNA crosstalk may have potential to improve the outcome of glioma patients.

Defining a Correlative Transcriptional Signature Associated with Bulk Histone H3 Acetylation Levels in Adult Glioblastomas

Glioblastoma (GB) is the most prevalent primary brain cancer and the most aggressive form of glioma because of its poor prognosis and high recurrence. To confirm the importance of epigenetics in glioma, we explored The Cancer Gene Atlas (TCGA) database and we found that several histone/DNA modifications and chromatin remodeling factors were affected at transcriptional and genetic levels in GB compared to lower-grade gliomas. We associated these alterations in our own cohort of study with a significant reduction in the bulk levels of acetylated lysines 9 and 14 of histone H3 in high-grade compared to low-grade tumors. Within GB, we performed an RNA-seq analysis between samples exhibiting the lowest and highest levels of acetylated H3 in the cohort; these results are in general concordance with the transcriptional changes obtained after histone deacetylase (HDAC) inhibition of GB-derived cultures that affected relevant genes in glioma biology and treatment (e.g., A2ML1, CD83, SLC17A7, TNFSF18). Overall, we identified a transcriptional signature linked to histone acetylation that was potentially associated with good prognosis, i.e., high overall survival and low rate of somatic mutations in epigenetically related genes in GB. Our study identifies lysine acetylation as a key defective histone modification in adult high-grade glioma, and offers novel insights regarding the use of HDAC inhibitors in therapy.

TRPC6 interacted with KCa1.1 channels to regulate the proliferation and apoptosis of glioma cells

Malignant glioma is the most aggressive and deadliest brain malignancy. TRPC6 and K_Ca1.1, two ion channels, have been considered as potential therapeutic targets for malignant glioma treatment. TRPC6, a Ca²⁺-permeable channel, plays a vital role in promoting tumorigenesis and the progression of glioma. K_Ca1.1, a large-conductance Ca²⁺-activated channel, is also involved in growth and migration of glioma. However, the underlying mechanism by which these two ion channels promote glioma progression was unclear. In our study, we found that TRPC6 upregulated the expression of K_Ca1.1, while the immunoprecipitation analysis also showed that TRPC6 interacts with K_Ca1.1 channels in glioma cells. The currents of K_Ca1.1 recorded by the whole-cell patch clamp technique were increased by TRPC6 in glioma cells, suggesting that TRPC6 can provide a Ca²⁺ source for the activation of K_Ca1.1 channels. It was also suggested that TRPC6 regulates the proliferation and apoptosis of glioma cells through K_Ca1.1 channels in vitro. Therefore, C6-bearing glioma rats were established to validate the results in vitro. After the administration of paxilline (a specific inhibitor of K_Ca1.1 channels), TRPC6-dependent growth of glioma was inhibited in vivo. We also found that TRPC6 enhanced co-expression with K_Ca1.1 in glioma. These all suggested that TRPC6/K_Ca1.1 signal plays a role in promoting the growth of glioma. Our results provided new evidence for TRPC6 and K_Ca1.1 as potential targets for glioma treatment.