LncRNA-H19 gene plays a significant role in regulating glioma cell function

Background

Glioma is an aggressive adult primary cancer, and is characterized by low cure rate, poor prognosis, and high recurrence. The present study aimed to investigate the effect of lncRNA‐H19 gene silencing on glioma cell function.

Methods

lncRNA‐H19 interference vector (LV3‐si‐H19) and negative control vector (LV3‐NC) were stably transfected into U251 and U87‐MG cells, respectively. Quantitative real‐time PCR (qRT‐PCR) was performed to investigate the expression of lncRNA‐H19. Cell proliferation capacity was tested by adopting cell counting kit (CCK8), and propidium iodide (PI) was used for cell cycle analysis. Meanwhile, flow cytometry (FCM) method was used to investigate cell apoptosis, cell migration capacity was detected via wound healing and transwell experiments, and sphere‐forming ability was examined in serum‐free suspension culture. Additionally, glioma animal models were conducted through injecting U251 cells to estimate the effects of lncRNA‐H19 on glioma growth in vivo.

Results

Knocking down lncRNA‐H19 gene could effectively suppress the proliferation of U251 and U87‐MG cells. The knockdown of lncRNA‐H19 remarkably inhibited the migration and blocked cycle progressions of U251 and U87‐MG cells, yet, no obvious changes were observed in cell apoptosis. Besides, inhibiting lncRNA‐H19 expression could attenuate sphere‐forming function of U251 and U87‐MG cells. Additionally, tumor volume and weight were significantly reduced in rats injected with U251 LV‐si‐H19 cell line compared to untransfected and negative controls, when survival time was obviously prolonged in U251 LV‐si‐H19 injection groups.

Conclusion

LncRNA‐H19 gene plays a carcinogenic role in glioma progression via enhancing aggressive behavior of glioma cells.

Bufalin induces mitochondrial dysfunction and promotes apoptosis of glioma cells by regulating Annexin A2 and DRP1 protein expression

Background

Glioma is a common primary central nervous system tumour, and therapeutic drugs that can effectively improve the survival rate of patients in the clinic are lacking. Bufalin is effective in treating various tumours, but the mechanism by which it promotes the apoptosis of glioma cells is unclear. The aim of this study was to investigate the drug targets of bufalin in glioma cells and to clarify the apoptotic mechanism.

Methods

Cell viability and proliferation were evaluated by CCK-8 and colony formation assays. Then, the cell cycle and apoptosis, intracellular ion homeostasis, oxidative stress levels and mitochondrial damage were assessed after bufalin treatment. DARTS-PAGE technology was employed and LC–MS/MS was performed to explore the drug targets of bufalin in U251 cells. Molecular docking and western blotting were performed to identify potential targets. siRNA targeting Annexin A2 and the DRP1 protein inhibitor Mdivi-1 were used to confirm the targets of bufalin.

Results

Bufalin upregulated the expression of cytochrome C, cleaved caspase 3, p-Chk1 and p-p53 proteins to induce U251 cell apoptosis and cycle arrest in the S phase. Bufalin also induced oxidative stress in U251 cells, destroyed intracellular ion homeostasis, and caused mitochondrial damage. The expression of mitochondrial division-/fusion-related proteins in U251 cells was abnormal, the Annexin A2 and DRP1 proteins were translocated from the cytoplasm to mitochondria, and the MFN2 protein was released from mitochondria into the cytoplasm after bufalin treatment, disrupting the mitochondrial division/fusion balance in U251 cells.

Conclusions

Our research indicated that bufalin can cause Annexin A2 and DRP1 oligomerization on the surface of mitochondria and disrupt the mitochondrial division/fusion balance to induce U251 cell apoptosis.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02137-x.

Depressive effectiveness of vigabatrin (γ-vinyl-GABA), an antiepileptic drug, in intermediate-conductance calcium-activated potassium channels in human glioma cells

BACKGROUND

Vigabatrin (VGB) is an approved non-traditional antiepileptic drug that has been revealed to have potential for treating brain tumors; however, its effect on ionic channels in glioma cells remains largely unclear.

METHODS

With the aid of patch-clamp technology, we investigated the effects of VGB on various ionic currents in the glioblastoma multiforme cell line 13-06-MG.

RESULTS

In cell-attached configuration, VGB concentration-dependently reduced the activity of intermediate-conductance Ca²⁺-activated K⁺ (IK_Ca) channels, while DCEBIO (5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) counteracted the VGB-induced inhibition of IK_Ca channels. However, the activity of neither large-conductance Ca²⁺-activated (BK_Ca) nor inwardly rectifying K⁺ (K_IR) channels were affected by the presence of VGB in human 13-06-MG cells. However, in the continued presence of VGB, the addition of GAL-021 or BaCl₂ effectively suppressed BK_Ca and K_IR channels.

CONCLUSIONS

The inhibitory effect of VGB on IK_Ca channels demonstrated in the current study could be an important underlying mechanism of VGB-induced antineoplastic (e.g., anti-glioma) actions.

Quantitative analysis for the differences in vasculogenic activity and sensitivity to angiogenic stimulants between human glioma cells and normal endothelial cells

Neovascularization is a histological feature of glioma, especially of glioblastoma (GBM), being associated with tumor invasiveness and poor prognosis. However, current anti-angiogenic therapies targeting vascular endothelial cells (ECs), has exhibited poor efficacy in some GBM cases. This may be at least partially attributed to the potential of glioblastoma cells to construct blood supply chain via vasculogenic mimicry or endothelial differentiation. This study aims to explore differences in vasculogenic activity and sensitivity to angiogenic stimulants between normal human ECs and glioma cells of different grades. We found that grade IV U87 GBM cells showed highly inducible vasculogenic activity either in the orthotopic xenograft model or under in vitro angiogenic stimulants as compared with grade II CHG5 glioma cells. The hypoxia mimetic more strongly induced in vitro vasculogenic capacity and endothelial marker expression of U87 GBM cells than the stimulation with multiple proangiogenic growth factors (vascular endothelial growth factor, basic fibroblast growth factor and epidermal growth factor). In contrast, proangiogenic effect of hypoxia on human umbilical vein endothelial cells (HUVECs) was weaker than on U87 GBM cells. In addition, it was also observed that the in vitro vasculogenic process of U87 cells started later but lasted longer than that of HUVECs. These results demonstrate that when compared with normal ECs, high-grade glioma cells basically possess weaker vasculogenic activity, but exhibit higher sensitivity and longer-lasting response to angiogenic stimulants, especially to hypoxia. This may be helpful to develop novel anti-angiogenic strategies targeting both vascular ECs and vasculogenic glioma cells.

HAUSP promoted the growth of glioma cells in vitro and in vivo via stabilizing NANOG

OBJECTIVE

To investigate the role and mechanisms of HAUSP (Herpesvirus Associated Ubiquitin Specific Protease) and NANOG in pathogenesis of malignant human gliomas progression.

METHODS

Lentivirus-mediated HAUSP over-expression and RNAiHAUSP mediated HAUSP down-regulation were established in the glioma cells (U87 and U251 cell lines). Firstly, Real-time qPCR, western-blot (WB) and immunofluorescence staining were performed to detect mRNA levels, protein expressions and deposition of HAUSP and NANOG in the glioma cells, respectively. Then cell proliferation, invasion, apoptosis and xenograft tumor growth in nude mice were assessed by using cell counting kit-8 (CCK-8) assay, transwell assay, flow cytometry (FCM) and Hematoxylin-Eosin (HE) staining.

RESULTS

We first demonstrated HAUSP was significantly increased in lentivirus- mediated HAUSP over-expression cells compared to the Control group. HAUSP over-expression could upregulate genes involved in proliferation and invasion such as NANOG. However, the mRNA of NANOG had no significant changes. Similarly, in RNAiHAUSP mediated HAUSP down-regulation group, HAUSP were significantly decreased compared to the Control group. Simultaneously, NANOG protein were decreased significantly, which decreased the proliferation and invasion, increased the apoptosis rate of glioma cells. Finally, low expression of HAUSP could suppress xenograft tumors growth in nude mice in different periods.

CONCLUSION

This study revealed that HAUSP-NANOG pathway is a key target to inhibit glioma cells proliferation, and NANOG play important role in the formation and evolution of glioma cells. The regulation of HAUSP could change the biological activity of glioma cells through regulate NANOG expression.

Impact of calcineurin inhibitors on rat glioma cells viability

Background

Although kidney transplantation outcomes have improved dramatically after using calcineurin inhibitors (CNIs), CNI toxicity continues to be reported and the mechanism remains uncertain. Here, we investigated the neurotoxicity of CNIs by focusing on the viability of glioma cells.

Methods

Glioma cells were treated with several concentrations of CNIs for 24 hours at 37℃ and their cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Results

Exposure to 0, 0.25, 0.5, 2.5, 5.0, and 10.0 mM concentrations respectively showed 100%, 64.3%, 61.3%, 68.1%, 62.4%, and 68.6% cell viability for cyclosporine and 100%, 38.6%, 40.8%, 43.7%, 37.8%, and 43.0% for tacrolimus. The direct toxic effect of tacrolimus on glioma cell viability was stronger than that of cyclosporine at the same concentration.

Conclusion

CNIs can cause neurological side effects by directly exerting cytotoxic effects on brain cells. Therefore, we should carefully monitor the neurologic symptoms and level of CNIs in kidney transplant patients.

Zika virus NS5 protein inhibits cell growth and invasion of glioma

Glioma is the most common primary brain tumor with high mortality. Given the poor outcomes with standard-of-care treatments, novel treatment strategies are needed. Oncolytic viral therapy for glioma has developed as an exciting therapeutic method in recent years. Zika virus, a member of flavivirus family, has oncolytic activity against glioma cells but the mechanism is unknown. Here, we aimed to determine which viral protein might play a critical role in mitigating glioma cell growth. We examined the tumor suppressor function of four nonstructural proteins NS1, NS3, NS4B and NS5 in human glioma cell line U87. As a result, we found that only NS5 significantly inhibited proliferation, migration and invasion of U87 cells. Moreover, expression of NS5 suppressed tumorigenicity of mouse GL261 glioma cell in vivo. Our findings provide some clues for further exploration of oncolytic Zika virus in the treatment of glioma.

An enzyme-based electrochemical biosensor probe with sensitivity to detect astrocytic versus glioma uptake of glutamate in real time in vitro

Glutamate, a major excitatory neurotransmitter in the central nervous system, is essential for regulation of thought, movement, memory, and other higher functions controlled by the brain. Dysregulation of glutamate signaling is associated with severe neuropathological conditions, such as epilepsy, and glioma, a form of brain cancer. Glutamate signals are currently detected by several types of neurochemical probes ranging from microdialysis-based to enzyme-based carbon fiber microsensors. However, an important technology gap exists in the ability to measure glutamate dynamics continuously, and in real time, and from multiple locations in the brain, which limits our ability to further understand the involved spatiotemporal mechanisms of underlying neuropathologies. To overcome this limitation, we developed an enzymatic glutamate microbiosensor, in the form of a ceramic-substrate enabled platinum microelectrode array, that continuously, in real time, measures changes in glutamate concentration from multiple recording sites. In addition, the developed microbiosensor is almost four-fold more sensitive to glutamate than enzymatic sensors previously reported in the literature. Further analysis of glutamate dynamics recorded by our microbiosensor in cultured astrocytes (control condition) and glioma cells (pathological condition) clearly distinguished normal versus impaired glutamate uptake, respectively. These results confirm that the developed glutamate microbiosensor array can become a useful tool in monitoring and understanding glutamate signaling and its regulation in normal and pathological conditions. Furthermore, the developed microbiosensor can be used to measure the effects of potential therapeutic drugs to treat a range of neurological diseases.

Apoptotic effects of ε-viniferin in combination with cis-platin in C6 cells

Glioblastoma (GBM) is one of the most common and lethal forms of primary brain tumors in human adults. Treatment options are limited, and in most cases ineffective. Natural products are sources of novel compounds endowed with therapeutic properties in many human diseases like cancer. ε-viniferin is a resveratrol dimer and well known for having antiproliferative and apoptotic effects on cancer cells. Cisplatin is a platinum containing anti-cancer drug. In this study, we aimed to investigate antiproliferative and apoptotic effects of using cis-platin and ε-viniferin alone or in combined treatment of C6 cells. Cell proliferation was detected by WST-1. Mitochondrial membrane potential changes in the cells (ΔΨm) were evaluated using cationic dye JC1. Apoptotic index which is a hallmark of late apoptosis was detected by using Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method and apoptotic alterations were observed by transmission electron microscope (TEM). Activation of caspase-8, -9, -3 in C6 cells at various incubation periods was measured by flow cytometer. Apoptotic index increased at highest level in only combined treatment cells (91.6%) after 48 h incubation. These results were supported by TEM images. Caspase-8 activation in C6 cells increased to a maximum (12.5%) after 6 h by using combined cis-platin/ε-viniferin treatment (13.25/95 μM). Caspase-9 was activated at 44.5% after combined treatment for 24 h. This rate is higher than using cis-platin (14.2%) or ε-viniferin (43.3%) alone. The combined 13.25 μM/cisplatin and 95 μM ε-viniferin treatment caused maximum caspase-3 activation in C6 cells (15.5%) at the end of the 72 h incubation. In conclusion, it was observed that caspase-8, -9, -3 activation which was determined in vitro, trigerred apoptotic mechanism in C6 cells by using low concentrations of combined cis-platin and ε-viniferin.

Study and evaluation of nucleolin-targeted delivery of magnetic PLGA-PEG nanospheres loaded with doxorubicin to C6 glioma cells compared with low nucleolin-expressing L929 cells

Magnetic nanoparticulate systems based on polymeric materials such as poly (lactic-co-glycolic acid) (PLGA1) are being studied for their potential applications in targeted therapy and imaging of malignant tumors. In the current study, superparamagnetic iron oxide nanocrystals (SPIONs2) and doxorubicin (Dox3) were entrapped in the PLGA-based nanoparticles via a modified multiple emulsion solvent evaporation method. Furthermore, SPIO/Dox-NPs4 were conjugated to anti-nucleolin AS1411 aptamer (Apt5) and their targeting ability was investigated in high nucleolin-expressing C6 glioma cells compared to low nucleolin-expressing L929 cells. The NPs exhibited a narrow size distribution with mean diameter of ~170nm and an appropriate SPION content (~18% of total polymer weight) with a sufficient saturation magnetization value of 5.9emu/g which is suitable for imaging objectives. They manifested an increased Dox release at pH5.5 compared to pH7.4, with initial burst release (within 24h) followed by sustained release of Dox for 36days. The Apt conjugation to NPs enhanced cellular uptake of Dox in C6 glioma cells compared to L929 cells. Similarly, the Apt-NPs increased the cytotoxicity effect of Dox compared with NPs and Dox solution (f-Dox) alone. In conclusion, the Apt-NPs were found to be a promising delivery system for therapeutic and diagnostic purposes.

Cathepsin L knockdown enhances curcumin-mediated inhibition of growth, migration, and invasion of glioma cells

Curcumin can be used to prevent and treat cancer. However, its exact underlying molecular mechanisms remain poorly understood. Cathepsin L, a lysosomal cysteine protease, is overexpressed in several cancer types. This study aimed to determine the role of cathepsin L in curcumin-mediated inhibition of growth, migration, and invasion of glioma cells. Results revealed that the activity of cathepsin L was enhanced in curcumin-treated glioma cells. Cathepsin L knockdown induced by RNA interference significantly promoted curcumin-induced cytotoxicity, apoptosis, and cell cycle arrest. The knockdown also inhibited the migration and invasion of glioma cells. Our results suggested that the inhibition of cathepsin L can enhance the sensitivity of glioma cells to curcumin. Therefore, cathepsin L may be a new target to enhance the efficacy of curcumin against cancers.

Novel hybrid DHPM-fatty acids: synthesis and activity against glioma cell growth in vitro

We described the first synthesis of fatty acid 3,4-dihydropyrimidinones (DHPM-fatty acids) using the Biginelli multicomponent reaction. Antiproliferative activity on two glioma cell lines (C6 rat and U-138-MG human) was also reported. The novel DHPM-fatty acids reduced glioma cell viability relative to temozolomide. Hybrid oxo-monastrol-palmitic acid was the most potent, reducing U-138-MG human cell viability by ca. 50% at 10 μM. In addition, the DHPM-fatty acids showed a large safety range to neural cells, represented by the organotypic hippocampal culture. These results suggest that the increased lipophilicity of DHPM-fatty acids offer a promising approach to overcoming resistance to chemotherapy and may play an important role in the development of new antitumor drugs.

The association between Salt-inducible kinase 2 (SIK2) and gamma isoform of the regulatory subunit B55 of PP2A (B55gamma) contributes to the survival of glioma cells under glucose depletion through inhibiting the phosphorylation of S6K

Background

PPP2R2C encodes a gamma isoform of the regulatory subunit B55 subfamily consisting PP2A heterotrimeric with A and C subunits. Currently, the precise functions of B55gamma in cancer are still under investigating. In this project, we reported a novel function of B55gamma in the regulation of glucose metabolism in Glioma cells.

Methods

Western blot and immunoprecipitation were performed to determine protein expression and interaction. Cell viability was measured by Typan Blue staining and direct cell counting using hematocytometer. siRNA technology was used to down regulate protein expression.

Results

Glucose uptake and lactate product were suppressed by overexpression of B55gamma in Glioma cells. In addition, cancer cells with larger amount of B55gamma showed higher survival advantages in response to glucose starvation through the dephosphorylation of S6K. From proteomic analysis, we found B55gamma binds with and up regulates SIK2 through the stabilization of SIK2 protein which is required for the B55gamma-mediated suppression of S6K pathway. Knocking down of SIK2 in B55gamma over expressing cells recovered the phosphorylation of S6K.

Conclusion

In summary, our project will provide novel insight into the design and development of therapeutic strategies to target the B55gamma-mediated glucose metabolism for the treatment of human brain tumor patients.

Methylation status of promoter 1 region of GDNF gene in human glioma cells

OBJECTIVE

This study aimed to investigate the methylation status of promoter 1 region of glial cell line-derived neurotrophic factor (GDNF) in human glioma cells and to explore the effect of GDNF methylation on the expression of GDNF in glioma.

METHODS

GDNF gene mutation was detected by sequencing in 10 patients with glioma and 5 healthy controls. Bisulfite modification for analysis of DNA methylation was done to detect the methylation status of promoter 1 region of GDNF in 20 patients with glioma (10 with poorly differentiated and 10 with well differentiated) and 5 healthy controls.

RESULTS

There was no mutation at the promoter 1 region of GDNF gene in glioma. The incidence of methylation of GDNF gene at the promoter 1 region in healthy control, patients with poorly differentiated glioma and those with well differentiated glioma was 72.25%, 86.25% and 86.75%. The incidence of GDNF methylation in glioma was significantly higher than that in the normal brain (P<0.05); while there was no significant difference between well differentiated glioma and poorly differentiated glioma.

CONCLUSIONS

Hypermethylation occurs in the promoter 1 region of GDNF and may influence the expression of GDNF in glioma.