Background Growing evidences indicate that circular RNAs (circRNAs) play an important role in the regulation of biological behavior of tumor. We aim to explore the role of circRNA in glioma and elucidate how circRNA acts. Methods Real-time PCR was used to examine the expression of circPTN in glioma tissues and normal brain tissues (NBT). Assays of dual- luciferase reporter system, biotin label RNA pull-down and FISH were used to determine that circPTN could sponge miR-145-5p and miR-330-5p. Tumor sphere formation assay was performed to determine self- renewal of glioma stem cell (GSCs). Cell counting Kit-8 (CCK8), EdU assay and flow cytometry were used to investigate proliferation and cell cycle. Intracranial xenograft was established to determine how circPTN impacts in vivo. Tumor sphere formation assay was performed to determine self- renewal of glioma stem cell (GSCs). Results We demonstrated circPTN was significantly higher expression in glioma tissues and glioma cell lines, compared with NBT and HEB (human astrocyte). In gain- and loss-of-function experiments, circPTN significantly promoted glioma growth in vitro and in vivo. Furthermore, we performed dual-luciferase reporter assays and RNA pull-down assays to verify that circPTN acts through sponging miR-145-5p and miR-330-5p. Increasing expression of circPTN rescued the inhibition of proliferation and downregulation of SOX9/ITGA5 in glioma cells by miR-145-5p/miR-330-5p. In addition, we found that circPTN promoted self-renewal and increased the expression of stemness markers (Nestin, CD133, SOX9, and SOX2) via sponging miR-145-5p. Moreover, this regulation was disappeared when circPTN binding sites in miR-145-5p were mutated. Conclusions Our results suggest that circPTN is an oncogenic factor that acts by sponging miR-145-5p/miR-330-5p in glioma.

The efficient and specific delivery of nanoparticles (NPs) to brain tumors is crucial for successful glioma treatment. Heparin‐based polymers decorated with two peptides self‐assemble into multi‐functional NPs that specifically target glioma cells. These NPs re‐self‐assemble to a smaller size in blood, which is beneficial for in‐vivo brain drug delivery. The hydrodynamic size of one type of these NPs is 63 ± 11 nm under blood‐mimic conditions (10% fetal bovine serum), but it is 164 ± 16 nm in water. Additionally their zeta potential is more neutral in the blood‐mimic conditions. Transmission electron microscopy reveals the morphology of the spherical NPs. In vitro experiments demonstrate that the NPs exhibit a high cellular uptake and the ability to efficiently discourage proliferation, endothelial‐lined vessels, and vasculogenic mimicry. In vivo studies demonstrate that the NPs can by‐pass the normal blood–brain and blood–(brain tumor) barriers and specifically accumulate in glioma tissues; moreover, they present an excellent anti‐glioma effect in subcutaneous/intracranial glioma‐bearing mice. Their superiority is due to their appropriate size in blood and the synergic effect arising from their targeting of two different receptors. The data suggests that these NPs are ideal for anti‐glioma therapy.

The prognosis for human glioma, a malignant tumor of the central nervous system, is poor due to its rapid growth, genetic heterogeneity, and inadequate understanding of its underlying molecular mechanisms. Circular RNAs composed of exonic sequences, represent an understudied form of noncoding RNAs (ncRNAs) that was discovered more than a decade ago, function as microRNA sponges. We aimed to assess the relationship between circ‐U2AF1 (CircRNA ID: hsa_circ_0061868) and hsa‐mir‐7‐5p and examine their effects on proliferation, apoptosis, and the metastatic phenotype of glioma cells regulated by neuro‐oncological ventral antigen 2 (NOVA2). We found that the expression levels of circ‐U2AF1 and NOVA2 were upregulated, while hsa‐miR‐7‐5p was downregulated in human glioma tissues and glioma cell lines. Our data and bioinformatic analysis indicated the association of these molecules with glioma grade, a positive correlation between circ‐U2AF1 and NOVA2 expression levels and a negative correlation of hsa‐miR‐7‐5p with both circ‐U2AF1 and NOVA2, respectively. In addition, silencing of circ‐U2AF1 expression resulted in increased hsa‐miR‐7‐5p expression and decreased NOVA2 expression both in vitro and in vivo. Luciferase assay confirmed hsa‐miR‐7‐5p as a direct target of circ‐U2AF1 and NOVA2 as a direct target of hsa‐miR‐7‐5p. Functionally, silencing of circ‐U2AF1 inhibits glioma development by repressing NOVA2 via upregulating hsa‐miR‐7‐5p both in vitro and in vivo. Thus, we assumed that circ‐U2AF1 promotes glioma malignancy via derepressing NOVA2 by sponging hsa‐miR‐7‐5p. Taken together, we suggest that circ‐U2AF1 can be a prognostic biomarker and the circ‐U2AF1/hsa‐miR‐7‐5p/NOVA2 regulatory pathway may be a novel therapeutic target for treating gliomas.

Abstract. The mammalian target of rapamycin (mTOR) is a crucial regulator in malignant gliomas. Vasculogenic mimicry (VM) describes functional channels established by highly malignant tumor cells that is different from endothelium-lined blood vessels. Our previous studies confirmed the existence and clinical significance of VM in medulloblastoma and glioblastoma. In the present study, by immunohistochemical and CD34/PAS histochemical double-staining, 34 cases (26.8%) with VM structures were identified among a total of 127 glioma cases, and these VM structures were associated with mTOR expression in the glioma specimens. In vitro, U87 malignant glioblastoma cells formed tube structures similar to HUVECs on Matrigel in 3D culture, and mTOR-specific inhibitor rapamycin inhibited VM formation in the U87 malignant glioblastoma cells under both normoxia and hypoxia. In addition, rapamycin and mTOR siRNA inhibited molecules in the signaling cascade of VM formation, particularly HIF-1α. Taken together, our results demonstrated that mTOR signaling is involved in VM formation, and may be a potential therapeutic target for gliomas.

Vasculogenic mimicry (VM) refers to the process by which highly aggressive tumor cells mimic endothelial cells to form vessel-like structures that aid in supplying enough nutrients to rapidly growing tumors. Histone deacetylases (HDACs) regulate the expression and activity of numerous molecules involved in cancer initiation and progression. Notably, HDAC3 is overexpressed in the majority of carcinomas. However, thus far, no data are available to support the role of HDAC3 in VM. In this study, we subjected glioma specimens to immunohistochemical and histochemical double-staining methods and found that VM and HDAC3 expression were related to the pathological grade of gliomas. The presence of VM correlated with HDAC3 expression in glioma tissues. The formation of tubular structures, as determined by the tube formation assay to evaluate VM, was impaired in U87MG cells when transfected by siRNA or treated with an HDAC3 inhibitor. Importantly, the expression of VM-related molecules such as MMP-2/14 and laminin5γ2 was also affected when HDAC3 expression was altered. Furthermore, U87MG cells were treated with a phosphoinositide 3-kinase (PI3K) inhibitor or/and ERK inhibitor and found that the PI3K and ERK signaling pathways play key roles in VM; whereas, in VM, the two signaling pathways did not act upstream or downstream from each other. Taken together, our findings showed that HDAC3 contributed to VM in gliomas, possibly through the PI3K/ERK–MMPs–laminin5γ2 signaling pathway, which could potentially be a novel therapeutic target for gliomas.

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Melatonin is synthesized by the pineal gland and is released into the blood. In the last several years, some studies have shown that melatonin has anticancer properties; however, the mechanisms behind the antitumour traits are unclear, especially in pancreatic cancer. Therefore, in the present study, we investigated the antitumour effects of melatonin on the human pancreatic carcinoma cell line MIA PaCa‑2 and explored its biological mechanisms. MIA PaCa‑2 cells were treated with melatonin, and we used a CCK‑8 assay to evaluate the cell viability. We also used flow cytometry to observe cell apoptosis and western blot analysis to assess the protein expression. Our study found that melatonin inhibited cell viability, suppressed colony formation and reduced cell migration and invasion and induced cell apoptosis in MIA PaCa‑2 cells. Our results showed that melatonin treatment inhibited NF‑κB p65 activation. Moreover, melatonin treatment activated the mitogen‑activated protein kinase pathways (c‑jun N‑terminal kinase and extracellular‑regulated kinase 1/2), which increased Bax protein expression and caspase‑3 cleavage and decreased Bcl‑2 protein expression. These new developments demonstrate that melatonin plays a potential role in anticancer treatment and may act as an effective therapeutic agent in the future.

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