miR-16 Inhibits Extracellular Signal-Regulated Kinases (ERK) Mitogen-Activated Protein Kinases (MAPK) Signaling to Affect Epithelial-Mesenchymal Transition (EMT) and Invasion of Glioma Cells

Abnormal MEK1 expression is associated with tumor cell EMT, invasion and metastasis. Decreased miR-16 level is associated with glioma. Bioinformatics analysis showed a relationship between miR-16 and MEK1. This study assessed whether miR-16 regulates MEK1 expression and affects glioma cell EMT and invasion. The tumor tissues and adjacent glioma tissues were collected to measure miR-16 and MEK1 mRNA. The dual luciferase assay validated the relation of miR-16 with MEK1. U251 cells were cultured and assigned into NC group and mimic group, followed by analysis of cell biological behaviors, and MEK1, p-ERK1/2, E-cadherin, N-Cadherin expression. Compared with adjacent tissues, miR-16 expression was significantly decreased and MEK1 was elevated in glioma tissues. Compared with HEB, miR-16 in glioma U251 and SHG44 cells was decreased and MEK1 was increased. Dual luciferase reporter gene experiments confirmed the relation of miR-16 with MEK1. Transfection of miR-16 mimic significantly down-regulated MEK1, p-ERK1/2 and N-cadherin in U251 cells, upregulated E-cadherin, inhibited cell proliferation, promoted apoptosis, and attenuated EMT and invasion of glioma cells. In conclusion, decreased miR-16 expression and increased MEK1 expression is related to glioma pathogenesis. Overexpression of miR-16 can inhibit MEK1 expression, ERK/MAPK signaling, glioma cell proliferation, promote apoptosis, and attenuate EMT and invasion.

LINC00883 Promotes Drug Resistance of Glioma Through a microRNA-136/NEK1-Dependent Mechanism

ObjectiveAccumulating evidence has highlighted the roles of long noncoding RNAs (lncRNAs) as competing endogenous RNAs (ceRNAs) of microRNAs (miRNAs) through their binding sites in the progression of glioma. Hereby, we aim to explore the role of LINC00883 as a regulator of miR-136 and its target, NIMA-related kinase 1 (NEK1), thus, its involvement in the drug resistance of glioma cells.Methods and ResultsMechanistic investigations by dual-luciferase reporter, RNA pull-down, and RNA-binding protein immunoprecipitation (RIP) assays indicated that LINC00883 bound to miR-136, thereby blocking miR-136-induced downregulation of NEK1. Through gain-of-function experiments in U251 cells that presented a high drug resistance, we found that ectopic expression of LINC00883 resulted in increased MRP (encoding multidrug resistance-associated protein), limited cell apoptosis, and increased proliferation. Expectedly, depleting LINC00883 yielded tumor-suppressive and anti-chemoresistance effects on U251 cells by increasing miR-136 and inhibiting NEK1. Next, drug-resistant glioma cell line SOWZ1, drug-sensitive glioma cell line SOWZ2, and drug-resistant glioma cell line SOWZ2-BCNU (SOWZ2 cultured in BCNU) were applied to validate the roles of LINC00883 in the regulation of multidrug resistance. LINC00883 knockdown suppressed the viability of SWOZ1, SWOZ2, and SWOZ2-BCNU cells.ConclusionIn conclusion, LINC00883 knockdown reduces drug resistance in glioma. Hence, our study provides a future strategy to prevent drug resistance-induced therapeutic failure in glioma.

Functional In Vitro Assessment of VEGFA/NOTCH2 Signaling Pathway and pRB Proteasomal Degradation and the Clinical Relevance of Mucolipin TRPML2 Overexpression in Glioblastoma Patients

Glioblastoma (GBM) is the most malignant glioma with an extremely poor prognosis. It is characterized by high vascularization and its growth depends on the formation of new blood vessels. We have previously demonstrated that TRPML2 mucolipin channel expression increases with the glioma pathological grade. Herein by ddPCR and Western blot we found that the silencing of TRPML2 inhibits expression of the VEGFA/Notch2 angiogenic pathway. Moreover, the VEGFA/Notch2 expression increased in T98 and U251 cells stimulated with the TRPML2 agonist, ML2-SA1, or by enforced-TRPML2 levels. In addition, changes in TRPML2 expression or ML2-SA1-induced stimulation, affected Notch2 activation and VEGFA release. An increased invasion capability, associated with a reduced VEGF/VEGFR2 expression and increased vimentin and CD44 epithelial-mesenchymal transition markers in siTRPML2, but not in enforced-TRPML2 or ML2-SA1-stimulated glioma cells, was demonstrated. Furthermore, an increased sensitivity to Doxorubicin cytotoxicity was demonstrated in siTRPML2, whereas ML2-SA1-treated GBM cells were more resistant. The role of proteasome in Cathepsin B-dependent and -independent pRB degradation in siTRPML2 compared with siGLO cells was studied. Finally, through Kaplan-Meier analysis, we found that high TRPML2 mRNA expression strongly correlates with short survival in GBM patients, supporting TRPML2 as a negative prognostic factor in GBM patients.

Isoform-Dependent Effects of Apolipoprotein E on Sphingolipid Metabolism in Neural Cells

Background: Sphingosine 1-phosphate (S1P) and ceramides have been implicated in the development of Alzheimer’s disease. Apolipoprotein E (ApoE) isoforms are also involved in the development of Alzheimer’s disease. Objective: We aimed at elucidating the potential association of the ApoE isoforms with sphingolipid metabolism in the central nervous system. Methods: We investigated the modulations of apolipoprotein M (apoM), a carrier of S1P, S1P, and ceramides in Apoeshl mice, which spontaneously lack apoE, and U251 cells and SH-SY5Y cells infected with adenovirus vectors encoding for apoE2, apoE3, and apoE4. Results: In the brains of Apoeshl mice, the levels of apoM were lower, while those of ceramides were higher. In U251 cells, cellular apoM and S1P levels were the highest in the cells overexpressing apoE2 among the apoE isoforms. The cellular and medium contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 and increased in the cells overexpressing apoE4. In SH-SY5Y cells, apoM mRNA and medium S1P levels were also the highest in the cells overexpressing apoE2. The cellular contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 = apoE4 and those in medium decreased in the order of the cells overexpressing apoE3 > apoE2, while increased in the cells overexpressing apoE4. Conclusion: The modulation of apoM and S1P might partly explain the protective effects of apoE2 against Alzheimer’s disease, and the modulation of ceramides might be one of the mechanisms explaining the association of apoE4 with the development of Alzheimer’s disease.

Hypoxia Enhanced Glioblastoma Resistance to Erastin-Induced Ferroptosis by Up-Regulating GPX4 via PI3K/AKT/HIF-1α Axis

Background Glioblastoma is the deadliest type of primary brain tumor with a high rate of recurrence and treatment resistance. Hypoxia contributed much to radiotherapy resistance and chemoresistance of cancer. Ferroptosis is a nonapoptotic, oxidative cell death and identified as a potential anticancer mechanism in recent years. Erastin acts as a ferroptosis activator and shows a potential role in tumor treatment but the relationship between hypoxia and erastin resistance in glioblastoma has not been explained. This study aimed to investigate the role and underlying mechanism of hypoxia in erastin-induced ferroptosis in glioblastoma. Methods Cell proliferation and viability were determined by Cell Counting Kit-8 (CCK-8) assay, flow cytometry, TUNEL assays, and clone formation assay. Lipid peroxides level was analyzed by Malondialdehyde (MDA) assay and flow cytometry using C11-BODIPY dye. The correlation between HIF-1α and GPX4 expression was detected in data from the TCGA database and was determined by ChIP-qPCR assay and luciferase reporter assay. Subcutaneous xenograft and orthotopic xenograft models were established to test our findings in vivo. Results Hypoxia for at least 16 hours significantly suppressed erastin-induced ferroptosis by up-regulating glutathione peroxidase 4 (GPX4) expression in U87 and U251 cells. Hypoxia promotes GPX4 expression via enhancing the PI3K/AKT/HIF-1α pathway. Mechanistically, HIF-1α directly bound to the GPX4 gene promoter region and promoted GPX4 transcription. AKT inhibitor MK-2206 and HIF-1α inhibitor PX-478 could significantly reverse the effect. Besides, under normoxia, PX-478 could induce a higher lipid peroxidation level by decreasing GPX4 expression in U87 and U251 cells but cannot induced cell death directly, and it could significantly enhance the tumor cell killing effect of erastin. In vivo, combination of PX-478 and erastin had a coordinated intensification effect on anticancer activity uncovered by subcutaneous xenograft and orthotopic xenograft mouse models. Conclusions Hypoxia enhanced glioblastoma resistance to erastin-induced ferroptosis by activating PI3K/AKT/HIF-1α pathway and promoting GPX4 expression in a transcriptional regulation way. Combination therapy of PX-478 and erastin may be a potential strategy against glioblastoma.

LINC01087 indicates a poor prognosis of glioma patients with preoperative MRI

Long intergenic non-coding RNA 01,087 (LINC01087) has been concerned as an oncogene in breast cancer, while its mechanism in glioma has been little surveyed. Thus, we searched the prognostic value and functional action of LINC01087 in glioma. Glioma patients after preoperative MRI diagnosis were enrolled, and LINC01087, microRNA (miR)-1277-5p, and alkaline ceramidase 3 (ACER3) levels were tested in glioma cancer tissue. The correlation between LINC01087 expression and the survival of patients were analyzed. LINC01087, miR-1277-5p, and ACER3 levels in U251 cells were altered via transfection, and cell malignant phenotypes were monitored. The relationship between miR-1277-5p and LINC01087 or ACER3 was detected. The LINC01087 and ACER3 expression was in up-regulation and the miR-1277-5p expression was in down-regulation in clinical glioma samples. High expression of LINC01087 was associated with poor prognosis of glioma patients with preoperative MRI. LINC01087 silencing restrained tumor malignancy in glioma cells. Mechanistically, LINC01087 directly interacted with miR-1277-5p. ACER3 was a known target of miR-1277-5p. Moreover, rescue assays reveal that miR-1277-5p overexpression (or ACER3 overexpression) reversed the effects of LINC01087 upregulation (or miR-1277-5p upregulation) on glioma cells. LINC01087 has prognostic significance in glioma and silencing LINC01087 deters glioma development through elevating miR-1277-5p to reduce ACER3 expression.

Analysis of Ionizing Radiation Induced DNA Damage by Superresolution dSTORM Microscopy

The quantitative detection of radiation caused DNA double-strand breaks (DSB) by immunostained γ-H2AX foci using direct stochastic optical reconstruction microscopy (dSTORM) provides a deeper insight into the DNA repair process at nanoscale in a time-dependent manner. Glioblastoma (U251) cells were irradiated with 250 keV X-ray at 0, 2, 5, 8 Gy dose levels. Cell cycle phase distribution and apoptosis of U251 cells upon irradiation was assayed by flow cytometry. We studied the density, topology and volume of the γ-H2AX foci with 3D confocal microscopy and the dSTORM superresolution method. A pronounced increase in γ-H2AX foci and cluster density was detected by 3D confocal microscopy after 2 Gy, at 30 min postirradiation, but both returned to the control level at 24 h. Meanwhile, at 24 h a considerable amount of residual foci could be measured from 5 Gy, which returned to the normal level 48 h later. The dSTORM based γ-H2AX analysis revealed that the micron-sized γ-H2AX foci are composed of distinct smaller units with a few tens of nanometers. The density of these clusters, the epitope number and the dynamics of γ-H2AX foci loss could be analyzed. Our findings suggest a discrete level of repair enzyme capacity and the restart of the repair process for the residual DSBs, even beyond 24 h. The dSTORM superresolution technique provides a higher precision over 3D confocal microscopy to study radiation induced γ-H2AX foci and molecular rearrangements during the repair process, opening a novel perspective for radiation research.

Oleanolic Acid Inhibits the Proliferation and Invasion of U251Glioma Cells and Promotes their Apoptosis through the IKK-β, MAPK3, and MAPK4 Signaling Pathway

Object: To investigate the effects of Oleanolic acid (OA) on proliferation, apoptosis, migration, and invasion of human glioma cell U251, as well as IKK-β and MAPK signaling pathways.Methods: The binding of OA to IKK-β and MAPK signaling pathway essential proteins IKK-β, MAPK3, and MAPK4 was analyzed by molecular docking technique. U251 cells were treated with different concentrations of OA. The proliferation and apoptosis rates of U251 cells were detected by CCK-8 assay, MTT assay, cell cloning assay, and AnnexinⅤ FITC/PI double staining assay. Transwell chamber assay was used to detect migration and invasion of U251 cells. Western blot was used to detect and analyze the expression levels of CYP17A1, IKK-β, PTGS2 and MAPK3/4 protein in U251 cells after OA treatment. Finally, the transcriptome sequencing method was used to detect the differentially expressed genes in the two groups, and the GO and KEGG enrichment analysis were performed.Results: The results of molecular docking showed that OA could stably bind to IKK-β, MAPK3, and MAPK4 proteins. OA could not only effectively inhibit the proliferation and induce apoptosis of U251 cells (P < 0.05), but also significantly inhibit the invasion of U251 cells (P < 0.005). Western blot assay confirmed that OA could dramatically inhibit the protein expression levels of CYP17A1, IKK-β, PTGS2, MAPK3, and MAPK4 in U251 cells (P < 0.01). A total of 446 significantly differentially expressed genes were detected in transcriptome sequencing, of which 96 were up-regulated genes and 350 were down-regulated genes. These genes are mainly involved in processes such as inflammation, metabolism, immunity, and regulation of cell growth.Conclusions: OA may inhibit the proliferation, migration, and invasion of glioma U251 cells by binding key molecules of the IKK-β signaling pathway and essential target proteins of MAPK3 and MAPK4 in the MAPK signaling pathway.

Combined Scutellarin and C18H17NO6 Imperils the Survival of Glioma: Partly Associated With the Repression of PSEN1/PI3K-AKT Signaling Axis

Glioma, the most common intracranial tumor, harbors great harm. Since the treatment for it has reached the bottleneck stage, the development of new drugs becomes a trend. Therefore, we focus on the effect of scutellarin (SCU) and its combination with C18H17NO6 (abbreviated as combination) on glioma and its possible mechanism in this study. Firstly, SCU and C18H17NO6 both suppressed the proliferation of U251 and LN229 cells in a dose-dependent manner, and C18H17NO6 augmented the inhibition effect of SCU on U251 and LN229 cells in vitro. Moreover, there was an interactive effect between them. Secondly, SCU and C18H17NO6 decreased U251 cells in G2 phase and LN229 cells in G2 and S phases but increased U251 cells in S phase, respectively. Meanwhile, the combination could further reduce U251 cells in G2 phase and LN229 cells in G2 and S phases. Thirdly, SCU and C18H17NO6 both induced the apoptosis of U251 and LN229. The combination further increased the apoptosis rate of both cells compared with the two drugs alone. Furthermore, SCU and C18H17NO6 both inhibited the lateral and vertical migration of both cells, which was further repressed by the combination. More importantly, the effect of SCU and the combination was better than positive control-temozolomide, and the toxicity was low. Additionally, SCU and C18H17NO6 could suppress the growth of glioma in vivo, and the effect of the combination was better. Finally, SCU and the combination upregulated the presenilin 1 (PSEN1) level but inactivated the phosphatidylinositol 3−kinase (PI3K)-protein kinase B (AKT) signaling in vitro and in vivo. Accordingly, we concluded that scutellarin and its combination with C18H17NO6 suppressed the proliferation/growth and migration and induced the apoptosis of glioma, in which the mechanism might be associated with the repression of PSEN1/PI3K-AKT signaling axis.