Radiosensitivity Of Glioma Cells Research Articles

IDH1R132H mutation increases radiotherapy efficacy and a 4-gene radiotherapy-related signature of WHO grade 4 gliomas

The prognosis for the WHO grade 4 IDH-mutant astrocytoma is better than IDH-wildtype glioblastoma (GBM) patients. The purpose of this study is to explore the potential mechanism of how IDH1 mutation can increase the efficacy of radiotherapy and to establish a risk-score model to predict the efficacy of radiotherapy in WHO grade 4 gliomas. First, we conducted experimental study on the effect of IDH1R132H mutation on glioma cells in vitro. Radiosensitivity of glioma cells was detected by γ-H2AX after 5 Gy radiation. Cell proliferation, migration and invasion were determined respectively by CCK-8, EDU, monolayer cell migration scratch assay and Transwell assay. Then we analyzed IDH1 gene status and the survival of WHO grade 4 glioma patients received radiotherapy in our center and verified our results by analyzing CGGA and TCGA database. For the risk-score model, we use CGGA data to find genetic differences between WHO grade 4 IDH-mutant astrocytoma and IDH-wildtype GBM patients, and determined a 4-gene radiotherapy-related signature through survival analysis by R software. Evaluation and verification through different glioma validation sets and different statistical methods. For in vitro experiments, we established glioma cells stably overexpressing IDH1 wild-type and IDH1-mutant proteins. γ-H2AX assay showed that IDH1-mutant glioma cells had higher radiosensitivity than wild-type. CCK-8 and EDU assay showed that proliferation capacity of IDH1-mutant glioma cells declined. Transwell assay and monolayer cell migration scratch assay also showed that IDH1-mutant glioma cells reduced migration and invasion capabilities. Among the 83 WHO grade 4 glioma patients who received radiotherapy in our center, WHO grade 4 IDH-mutant astrocytoma patients had longer OS and PFS versus IDH-wildtype GBM (P = 0.0336, P = 0.0324, respectively). TCGA and CGGA database analysis had the similar results. Through complex analysis of CGGA and TCGA databases, we established a risk-model that can predict the efficacy of radiotherapy for WHO grade 4 glioma patients. The 4-gene radiotherapy-related signature including ADD3, GRHPR, RHBDL1 and SLC9A9. Patients in the high-risk group had worse OS compared to low-risk group (P = 0.0001). High- and low-risk groups of patients receiving radiotherapy have significant survival differences, while patients who did not receive radiotherapy have no survival difference both in CGGA and TCGA databases. WHO grade 4 IDH-mutant astrocytoma is more radiosensitive than IDH-wildtype GBM patients. Our 4-gene radiotherapy-related signature can predict the radiation efficacy of WHO grade 4 glioma patients, and it may provide some reference for clinical treatment options.

DNAR-01. PAR-MEDIATED DNA DAMAGE SIGNALING IN IDH MUTANT GLIOMAS: COMBINING PARG INHIBITION AND RADIATION FOR SELECTIVE CYTOTOXICITY

Abstract Isocitrate dehydrogenase (IDH) 1 or 2 mutant gliomas have unique metabolic characteristics and DNA damage response. Radiotherapy and chemotherapy have been proven to be effective treatments for IDH mutant gliomas. Poly (ADP-ribose) (PAR) mediates DNA damage response and is regulated by opposing enzymes: poly (ADP-ribose) polymerases (PARPs) synthesize PAR, while poly (ADP-ribose) glycohydrolase (PARG) breaks it down. Combining PARG inhibitor (PARGi) and Temozolomide (TMZ) in IDH mutant cells leads to imbalanced NAD sequestration into PAR, causing metabolic lethality. This study characterizes the combination of PARGi and radiation. PARGi monotherapy showed no difference between IDH mutant and wild-type cells. However, we found that combining PARGi with radiation significantly increased cytotoxicity in IDH mutant glioma models, similar to PARPi and radiation. (Wang et al, ACi.Adv. 2020) Our findings showed that unlike TMZ+PARGi, PARGi and radiation did not consume and deplete NAD. Cytotoxicity was partially reversed by IDH inhibitor, highlighting the contribution of PAR-mediated DNA damage signaling in IDH mutant contexts. This convergence of vulnerabilities in IDH mutant cells identifies PAR-mediated DNA repair mechanisms that operate independently of NAD metabolism. IDH mutant enzyme generates 2 hydroxyglutarate (2HG), which is critical early in tumor development. However, the effect of 2HG on radiation sensitivity varies across cellular contexts. In this study, we found that IDH1 mutation and 2HG production enhance radiosensitivity in glioma cells both in vivo and in in vitro models, facilitated by PAR-dependent mechanisms. This augmentation of radiosensitivity is associated with S-phase blockage of the cell cycle, unveiling a vulnerability in the replication process of these cancer cells. In summary, this study demonstrates that the combination of PARGi and radiation regulates DNA repair pathways, augmenting cytotoxicity specifically in IDH mutant gliomas. Targeting PAR during radiation holds promise for treating IDH mutant gliomas, tailoring therapy to maximize durability while minimizing impact on normal cells.

CA9 knockdown enhanced ionizing radiation-induced ferroptosis and radiosensitivity of hypoxic glioma cells

Purpose Ferroptosis is a type of regulatory cell death, caused by excessive lipid peroxidation This study aimed to explore whether ionizing radiation could induce ferroptosis in glioma cells and whether carbonic anhydrase 9 (CA9) knockdown could enhance the killing effect of ionizing radiation on hypoxic glioma cells through ferroptosis. Materials and methods The protein levels of Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4) were detected by Western blot in glioma cells irradiated by different doses of X-ray. The relative mRNA levels of ferroptosis markers and intracellular iron-associated proteins were detected by Real-time qPCR. Lipid peroxidation of glioma cells was detected by oxidation-sensitive probe C11-BODIPY581/591 staining. CCK-8 Assay was used to detect cell viability after X-ray irradiation. Cloning formation assay was used to assess the radiosensitivity of glioma cells. The exposure of cell surface calreticulin was measured by immunofluorescence staining. Results X-ray induced lipid peroxidation and ferroptosis markers expression in U251 and GL261 glioma cells. Knockdown of CA9 in hypoxic glioma cells significantly altered the expression of iron regulation-related proteins and enhanced X-ray-induced ferroptosis and radiosensitivity. The ferroptosis inhibitor significantly improved the survival of cells irradiated by X-ray, while ferroptosis inducers (FINs) enhanced the lethal effect of X-ray on cells. Enhancing ferroptosis in glioma cells promoted the exposure and release of damage-associated molecular patterns (DAMPs). Conclusions Ionizing radiation can induce ferroptosis in glioma cells. CA9 knockdown can enhance the radiosensitivity of hypoxic glioma cells and overcome the resistance of ferroptosis under hypoxia. Enhancing ferroptosis will become a new idea to improve the efficacy of radiotherapy for glioma.

DNA polymerase ζ suppresses the radiosensitivity of glioma cells by regulating the PI3K/AKT/mTOR pathway

Glioblastoma is the most common glioma with high mortality and poor prognosis. Radiation resistance is one of the large challenges in the treatment of glioma. The study aimed to identify whether DNA polymerase ζ affects glioma cell radiosensitivity. The mRNA and protein levels of REV3L and REV7 were examined using quantitative real-time PCR and western blot. After REV3L and REV7 knockdown in a GBM cell line (A172), we assessed cell viability, colonies, apoptosis, and immune escape. The underlying mechanisms were evaluated using western blot and were confirmed using rescue experiments. The results showed that REV3L and REV7 levels were increased in glioma and related to poor survival. γ-ray treatment inhibited cell viability, survival fraction, and immune escape, and induced apoptosis of glioma cells from a GBM cell line, whereas knockdown of REV3L or REV7 enhanced these effects. Mechanically, silencing of REV3L or REV7 inactivated the PI3K/AKT/mTOR pathway. IGF-1 treatment abrogated the effects on cell viability, colonies, and apoptosis induced by REV3L or REV7 knocking down. Taken together, silencing of REV3L and REV7 inhibited radiation resistance via inactivating the PI3K/AKT/mTOR pathway, suggesting that targeting DNA polymerase ζ may be a new strategy to reduce the radiotherapy resistance of glioma.

Arsenite-induced Radiosensitization of Glioma Cells Is Dependent on p53 Deficiency.

Arsenite is a radiosensitizer of glioma cells both in vitro and in vivo; however, the underlying mechanism of action is unclear. Radiosensitizers specific for p53-deficient tumors are a promising adjunct to radiotherapy because, unlike normal cells, many tumor cells lack p53. Previously, we demonstrated that arsenite sensitizes the p53-deficient glioma cell line U87MG-E6 to X-rays. Using flowcytometry, we expand these findings to p53-proficient U87MG cells exposed to heavy ion beams, including carbon and iron ions. Arsenite sensitized U87MG-E6, but not U87MG, cells to heavy ion beams and X-rays. Cell cycle analysis indicated that sensitization of U87MG-E6 was related to an increase in the percentage of cells in the late S/G2/M phases after combined treatment with arsenite, especially when carbon ion beams were used. Induction of γH2AX was significant in U87MG-E6, but not in U87MG, cells after irradiation with carbon ion beams plus arsenite. Arsenite sensitizes cells by increasing the percentage of cells in the late S/G2/M phases after irradiation, possibly via inhibition of DNA repair in the context of p53 deficiency. The findings provide information that may be useful for the development of advanced radiotherapy protocols.

Gold nanoparticles enhances radiosensitivity in glioma cells by inhibiting TRAF6/NF-κB induced CCL2 expression

Gliomas are inherently difficult to treat by radiotherapy because glioma cells become radioresistant over time. However, combining radiotherapy with a radiosensitizer could be an effective strategy to mitigate the radioresistance of glioma cells. Gold nanoparticles (AuNPs) have emerged as a promising nanomaterial for cancer therapy, but little is known about whether AuNPs and X-ray radiation have cytotoxic synergistic effects against tumors. In this study, we found that the combination of AuNPs and X-ray irradiation significantly reduced the viabilities, as well as the migration and invasion, of glioma cells. Mechanistically, we observed that the AuNPs inhibited radiation-induced CCL2 expression by inhibiting the TRAF6/NF-κB pathway, which likely manifested the synergistic therapeutic effect between the AuNPs and X-ray radiation. The AuNPs also re-sensitized radioresistant glioma cells by inhibiting CCL2 expression. These results were also observed in another tumor cell line with a different molecular pattern, indicating that the underlying mechanism may be ubiquitous through cancer cells. Lastly, using the glioma mouse model, we observed that AuNPs significantly reduced tumor growth in the presence of X-ray radiation compared to radiotherapy alone.

Using Hyperbaric Oxygen to Improve the Radiosensitivity of Human U251 Glioma Cells.

The aim of this study was to explore the use of hyperbaric oxygen to enhance the radiosensitivity of human glioma cells. Sub-cultured U251 human glioma cells were randomly divided into four groups: an untreated control group, cells treated with hyperbaric oxygen (HBO) only, cells treated with X-ray irradiation (X-ray) only, and cells treated with both HBO and X-ray. Cell morphology, cell proliferation activity, cell cycle distribution, and apoptosis were observed in these groups to evaluate the role of HBO in improving the radiosensitivity of glioma cells. With the increase in X-ray doses (0 Gy, 2 Gy, 4 Gy, 6 Gy, 8 Gy), the survival fraction (SF) of glioma cells gradually decreased. Significantly lower SF was observed for the cells treated with the HBO and X-ray together than in the X-ray group for each dose (all P < 0.05). The proliferation inhibition was significantly higher in the HBO combined with X-ray group than in the X-ray group for each dose (all P < 0.05) for the U251 cell line. The percentage of G2/M phase cells was significantly higher in the HBO combined with X-ray (2 Gy) group (26.70% ± 2.46%) and the HBO group (22.36% ± 0.91%) than in the control group (11.56% ± 2.01%) and X-ray (2 Gy) group (10.35% ± 2.69%) (all P < 0.05). U251 cell apoptosis was significantly higher in the HBO combined with X-ray (2 Gy) group than in the HBO group, the X-ray (2 Gy) group, and the control group (all P < 0.05). We conclude that HBO can enhance the proliferation inhibition and apoptosis of glioma U251 cells by blocking glioma cells in the G2/M phase and improve the radiosensitivity of U251 glioma cells.

Micro RNA-640 Targeting SLIT1 Enhances Glioma Radiosensitivity by Restraining the Activation of Wnt/β-Catenin Signaling Pathway.

Purpose: The purpose of this study was to analyze the effects of miR-640–SLIT1 axis and the Wnt/β-catenin signaling pathway on radiosensitivity of glioma cells. Methods: Relative expressions of miR-640 and slit guidance ligand 1 (SLIT1) in glioma tissues and glioma cell lines U251 and A172 were detected using RT-qPCR. The cell lines were transfected with si-SLIT1 or miR-640 inhibitor to study the radiosensitivity of glioma cells. We detected cell activity using CCK-8 assay, cell migration using wound healing assay, cell invasion using transwell assay, and apoptosis using caspase-3 assay. Results: SLIT1 was upregulated in glioma tissues and cell lines, and inversely correlated with radiation sensitivity. Its knockdown reduced radioresistance, migration, and invasion, but increased apoptosis in U251 and A17 cells. Loss of miR-640 activity upregulated SLIT1, Wnt, and β-catenin protein expression, whereas it inhibited p-GSK-3β protein levels in U251 and A17 cells. These results suggest that miR-640 mediates the radiosensitivity of glioma cells through SLIT1 and the Wnt/β-catenin signaling pathway. Conclusion: The miR-640–SLIT1 axis that regulates the Wnt/β-catenin signaling pathway is a possible therapeutic option for the effective treatment of glioma in combination with radiotherapy.

Radiosensitization of Glioma Cells by Temozolomide (TMZ): A Colony Formation Assay.

Background: Glioblastoma is one of the most radioresistant cancers. It is suggested that combination of radiotherapy with other cancer treatment modalities may increase control of tumor. Temozolomide (TMZ) is one of the most known drugs for glioblastoma. It has shown that TMZ via induction of mutation and cell death can kill glioma cells.Objective: In the current study, we aimed to show possible radiosensitization effect of TMZ for glioma cells. In addition, results compared to response of normal fibroblast cells to TMZ and irradiation.Material and Methods: This is in vitro study for evaluation of the effect of TMZ and irradiation on high grade glioma cells and normal fibroblasts. The human fibroblast and glioma cells were cultured as monolayer. The cells were treated with 2000 μM TMZ, which was equal drug dose for IC50%. In addition, irradiation was done with 5Gy gamma rays. The formation of colony was observed following irradiation, treatment with TMZ, and combination both of them.Results: The formation of colony for both glioma and fibroblast cells showed a reduction following irradiation or treatment with TMZ. Irradiation showed more toxicity compared to TMZ for glioma cells, but not fibroblast cells. Combination of TMZ and irradiation showed a significant reduction in the colony formation compared to irradiation or TMZ treatment alone.Conclusion: This study showed that TMZ increases sensitivity of both glioma and fibroblast cells to ionizing radiation.

HACE1-mediated NRF2 activation causes enhanced malignant phenotypes and decreased radiosensitivity of glioma cells

HACE1, an E3 ubiquitin-protein ligase, is frequently inactivated and has been evidenced as a putative tumor suppressor in different types of cancer. However, its role in glioma remains elusive. Here, we observed increased expression of HACE1 in gliomas related to control subjects, and found a strong correlation of high HACE1 expression with poor prognosis in patients with WHO grade III and IV as well as low-grade glioma (LGG) patients receiving radiotherapy. HACE1 knockdown obviously suppressed malignant behaviors of glioma cells, while ectopic expression of HACE1 enhanced cell growth in vitro and in vivo. Further studies revealed that HACE1 enhanced protein stability of nuclear factor erythroid 2-related factor 2 (NRF2) by competitively binding to NRF2 with another E3 ligase KEAP1. Besides, HACE1 also promoted internal ribosome entry site (IRES)-mediated mRNA translation of NRF2. These effects did not depend on its E3 ligase activity. Finally, we demonstrated that HACE1 dramatically reduced cellular ROS levels by activating NRF2, thereby decreasing the response of glioma cells to radiation. Altogether, our data demonstrate that HACE1 causes enhanced malignant phenotypes and decreased radiosensitivity of glioma cells by activating NRF2, and indicate that it may act as the role of prognostic factor and potential therapeutic target in glioma.

MiR-56a Mediates the Wnt/β-Catenin Pathway to Promote the Efficacy of Radiation on Glioma

Clarification of the miR-56a-mediated effect of Wnt/β-catenin pathway in glioma cells on radiosensitization. miRNA arrays were used to analyze the differential expression of miRNAs in biopsies from glioma patients. qRT-PCR to detect the levels of miR-56a and Wnt/β-catenin expressed in glioma cells and tissues. Evaluation of the impact of miR-56a on cell growth, invasion, and migrationforming ability by MTT assay and colony formation experiments. To analyze the involvement of miR-56a-mediated Wnt/β-catenin pathway in glioma biological processes and to examine the impact of miR-56a in glioma cell radiosensitivity. After miRNA array analysis, we found that miR-56a expression was significantly increased, and further studies showed that ectopic miR-56a expression in glial cells was sensitive to radiotherapy. miR-56a induction of Wnt/β-catenin promotes the upregulation of Parp in glioma cells. miR-56a can promote glioma cell migration and invasion in vitro as an important potential target for glioma disease.

Erratum.

The role of miRNAs in the radiosensitivity of glioma cells and the underlying mechanism is still far from clear. In the present study, we detected six downregulated and seven upregulated miRNAs in the serum after radiotherapy compared with paired serum samples before radiotherapy via miRNA panel PCR. Among these, miR-17-5p was highly reduced (fold change = −4.21). Further, we validated the levels of miR-17-5p in all serum samples with qRT-PCR. In addition, statistical analysis suggested that a reduced miR-17-5P level was positively associated with advanced clinical stage of glioma, incidence of relapse, and tumor differentiation. Moreover, we provided evidence that irradiation markedly activated autophagy and decreased miR-17-5p in the glioma cell line. Further, we demonstrated that irradiation-induced autophagy activation was mediated by beclin-1, and downregulation of beclin-1 via siRNA significantly abolished the irradiation-activated autophagy. Interestingly, we demonstrated that miR-17-5p could directly target beclin-1 via luciferase gene reporter assay. Exotic expression of miRNA-17-5p decreased autophagy activity in vitro. In nude mice, miRNA-17-5p upregulation sensitized the xenograft tumor to irradiation and suppressed irradiation-induced autophagy. Finally, pharmacal inhibition of autophagy markedly enhanced the cytotoxicity of irradiation in RR-U87 cells.

Knockdown of circ_0008344 contributes to radiosensitization in glioma via miR-433-3p/RNF2 axis

Numerous studies have identified that circular RNAs (circRNAs) functioned as important regulators in tumor initiation, carcinogenesis, drug or radiation resistance. This study aims to reveal the function of circ_0008344 on radiosensitivity in glioma. The quantitative real-time polymerase chain reaction (qRT-PCR) was implemented for detecting the circ_0008344 and microRNA-433-3p (miR-433-3p) levels. Cell survival intensity and apoptosis were analyzed through colony formation assay and flow cytometry respectively. The protein levels were examined via Western blot. Dual-luciferase reporter assay was exploited for the analysis of target combination. Xenograft models were established in mice for circ_0008344 research in vivo. Our data showed that circ_0008344 level was signally increased in radioresistant glioma tissues and its down-regulation facilitated the susceptibility of glioma cells to radiation. Additionally, we found that circ_0008344 could interact with miR-433-3p and regulated radiosensitivity of glioma cells via sponging miR-433-3p. Ring finger protein 2 (RNF2) was proved to be a target of miR-433-3p and it was regulated by circ_0008344/miR-433-3p axis. The promotion of circ_0008344 knockdown on radiosensitivity was counteracted by RNF2 overexpression in glioma cells. Further experiment in vivo indicated that circ_0008344 down-regulation inhibited glioma growth and acted on miR-433-3p/RNF2 axis to enhance the radiosensitivity in glioma. These evidences manifested that knockdown of circ_0008344 exerted the radiosensitivity-promoting effect on glioma via the miR-433-3p-mediated RNF2 down-regulation, identifying circ_0008344 as a novel diagnostic biomarker of radioresistance and therapeutic target in glioma radiotherapy.

AEG-1 Knockdown Sensitizes Glioma Cells to Radiation Through Impairing Homologous Recombination Via Targeting RFC5.

Radiotherapy is the most important adjuvant treatment for glioma; however, radioresistance is the major cause for inevitable recurrence and poor survival of glioma patients. Thus, this study aims to investigate the effect of astrocyte elevated gene-1 (AEG-1) on the radiosensitivity of glioma cells. Immunohistochemistry assay found that AEG-1 was generally overexpressed in glioma tissues and was correlated with poor clinicopathological features of glioma patients. AEG-1 knockdown inhibited proliferation of glioma cells. And γ-H2AX foci assay, colony formation assay, and flow cytometry analysis demonstrated that AEG-1 depletion enhanced radiosensitivity and promoted apoptosis as well as cell cycle arrest in G2 phase of glioma cells treated by ionizing radiation. Moreover, replication factor C5 (RFC5) was screened as the target of AEG-1 by using Affymetrix human gene expression array, and RFC5 expression was downregulated in AEG-1 knockdown glioma cells. Mechanistically, AEG-1 knockdown impaired homologous recombination repair activity induced by radiation through inhibiting RFC5 expression. Furthermore, the Kaplan-Meier analysis and multivariate Cox regression analysis indicated that high levels of AEG-1 and RFC5 were related to poor prognosis of glioma patients treated with radiotherapy. Taken together, our findings indicate that AEG-1 may serve as a reliable radiosensitizing target for glioma radiotherapy.

Knockdown of Long Non-Coding RNA HCP5 Increases Radiosensitivity Through Cellular Senescence by Regulating microRNA-128 in Gliomas.

IntroductionGlioma is the most common malignant brain tumor in adults. Radiation is a key therapy in glioma. However, the radioresistance of glioma was a big challenge. HLA complex P5 (HCP5) has been reported dysregulated in several types of malignant tumor, including glioma. The role of HCP5 in the radiosensitivity of glioma is so far unknown. The present study aimed to investigate the effect of HCP5 on radiosensitivity in gliomas.MethodsThe levels of HCP5 and microRNA (miR)-128 were detected using qRT-PCR. The cell growth curve was used to show the cell proliferation and evaluate the radiosensitivity of glioma cells following exposure to X-ray. Senescence-associated β-galactosidase (SA-β-Gal) staining was used to test the cellular senescence. Luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to determine the correlation between HCP5 and miR-128.ResultsHCP5 level of glioma cells was significantly higher than human astrocytes, whereas miR-128 level was lower in glioma cells. Besides, the HCP5 expression was increased in glioma tissues compared to normal brain tissues (NBTs). Knockdown of HCP5 inhibited cell proliferation and increased radiosensitivity in glioma cells. MiR-128 was predicted to be a target of HCP5. It was demonstrated that HCP5 directly bound to miR-128 and regulated its expression in glioma cells. Furthermore, the effects of HCP5 knockdown on radiosensitivity of glioma cells were attenuated by the inhibitor of miR-128.ConclusionThese findings suggested that interaction between lncRNA HCP5 and microRNA-128 could regulate the radiosensitivity of glioma cells by intervening in cellular senescence. This might be used as the potential radio-sensitization targets for glioma therapy.

FOXG1 mediates the radiosensitivity of glioma cells through regulation of autophagy

Background/Aim Upregulation of Forkhead box G1 (FOXG1) has recently been observed in many cancers, while its effect on radiosensitivity in glioma is still unclear. In this study, we hypothesized that FOXG1 be a major player in radioresistance of glioma as well as the underlying mechanism. Methods Immunohistochemistry (IHC) was conducted to assess FOXG1 expression in glioma tissues and glioma-adjacent tissues. Western Blot was implemented to detect the expression of autophagy-related proteins. CCK-8, colony formation and flow cytometry assays were implemented to assess cell viability, proliferation and apoptosis, respectively. Transmission electron microscope (TEM) was used to observe autophagic vesicles. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay was applied to detect the expression of FOXG1. Results The present study demonstrated that FOXG1 was highly expressed in glioma tissues. FOXG1 expression level was up-regulated in glioma cells following exposure to X-ray irradiation. FOXG1 can attenuate radiosensitivity of glioma cells. Moreover, it revealed that FOXG1 attenuate radiosensitivity of glioma cells by promoting autophagy. Conclusions The present study suggests that FOXG1 is a pivotal molecule for circumventing radiation-induced cell death in malignant glioma cells through the regulation of autophagy, and it may be a target for the treatment of human brain glioma.

Overexpression of RPN2 suppresses radiosensitivity of glioma cells by activating STAT3 signal transduction

BackgroundRadiation therapy is the primary method of treatment for glioblastoma (GBM). Therefore, the suppression of radioresistance in GBM cells is of enormous significance. Ribophorin II (RPN2), a protein component of an N-oligosaccharyl transferase complex, has been associated with chemotherapy drug resistance in multiple cancers, including GBM. However, it remains unclear whether this also plays a role in radiation therapy resistance in GBM.MethodsWe conducted a bioinformatic analysis of RPN2 expression using the UCSC Cancer Genomics Browser and GEPIA database and performed an immunohistochemical assessment of RPN2 expression in biopsy specimens from 34 GBM patients who had received radiation-based therapy. We also studied the expression and function of RPN2 in radiation-resistant GBM cells.ResultsWe found that RPN2 expression was upregulated in GBM tumors and correlated with poor survival. The expression of RPN2 was also higher in GBM patients with tumor recurrence, who were classified to be resistant to radiation therapy. In the radiation-resistant GBM cells, the expression of RPN2 was also higher than in the parental cells. Depletion of RPN2 in resistant cells can sensitize these cells to radiation-induced apoptosis, and overexpression of RPN2 had the reverse effect. Myeloid cell leukemia 1 (MCL1) was found to be the downstream target of RPN2, and contributed to radiation resistance in GBM cells. Furthermore, STAT3 was found to be the regulator of MCL1, which can be activated by RPN2 dysregulation.ConclusionOur study has revealed a novel function of RPN2 in radiation-resistant GBM, and has shown that MCL1 depletion or suppression could be a promising method of therapy to overcome the resistance promoted by RPN2 dysregulation.

Silencing long non-coding RNA HCP5 increases the radiosensitivity of glioma cells by up-regulating miR-508-3p expression

Objective To investigate the effect of long non-coding (lnc) RNA HCP5 on the radiation sensitivity of glioma cells and underlying mechanism. Methods The glioma cells U251 and U87 were irradiated with 0, 2, 4, 6, and 8 Gy rays as different doses.si-Con, si-HCP5, pcDNA, and pcDNA-HCP5 were transfected into cells U251 and U87, recorded as si-con group, si-HCP5 group, pcDNA group, and pcDNA-HCP5 group.si-Con and si-HCP5 were transfected into cells U251 and U87, and then irradiated with 4 Gy rays, respectively, recorded as IR+ si-con group and IR+ si-HCP5 group, the cells only irradiated with 4 Gy rays were recorded as IR group.After si-HCP5 with anti-miR-con and anti-miR-508-3p was co-transfected into cell U251 and U87, respectively, irradiated with 4 Gy rays, recorded as IR+ si-HCP5+ anti-miR-con group and IR+ si-HCP5+ anti-miR-508-3p group, respectively, the transfection was performed by liposome method.RT-qPCR was used to detect the expression of miR-508-3p and HCP5.Cell clone formation assay was used to detect the radiosensitivity of glioma cells.Flow cytometry was used to detect apoptosis, dual luciferase Reporter gene detection experiments detects fluorescence activity. Results HCP5 was highly expressed in radiation-treated glioma cells, and miR-508-3p was lowly expressed.After silenced HCP5, U251 and U87 cells had enhanced radiosensitivity and apoptotic rate((16.67±1.68) vs (3.58±0.62), t=21.929, P<0.05; (12.32±1.08) vs (4.48±0.71), t=18.198, P<0.05) was increased, and γ-H2AX( (0.45±0.04) vs (0.23±0.05), t=10.307, P<0.05; (0.38±0.04) vs (0.24±0.03), t=8.400, P<0.05), Cleaved caspase-3((0.37±0.04) vs (0.16±0.03), t=12.600, P<0.05; (0.38±0.04) vs (0.22±0.03), t=9.600, P<0.05) expressions were increased.Compared with silencing HCP5 or radiation treatment alone, silencing HCP5 and radiation treatment of U251 cells simultaneously, the apoptosis rate ((25.34±1.54) vs (16.67±1.68), t=11.413, P<0.05; (25.34±1.54) vs (11.13±1.06), t=22.802, P<0.05) was significantly increased, and γ-H2AX((0.69±0.05) vs (0.45±0.04), t=11.245, P<0.05; (0.69±0.05) vs (0.31±0.04), t=17.804, P<0.05), Cleaved caspase-3 ((0.52±0.06/0.37±0.04, t=6.240, P<0.05) (0.52±0.06/0.34±0.04, t=7.488, P<0.05) expressions were increased.The expressions of p-PI3K ((0.21±0.02) vs (0.52±0.04), t=20.795, P<0.05; (0.26±0.23 ), ( 0.67±0.07), t=5.116, P<0.05), p- AKT ((0.22±0.03) vs (0.66±0.07), t=17.332, P<0.05; (0.23±0.04) vs (0.71±0.03), t=28.800, P<0.05) in U251 and U87 cells were decreased.HCP5 can target the regulation of miR-508-3p expression; interfering with miR-508-3p reversed the effects of silent HCP5 and radiation on the radiation sensitization and apoptosis of U251 and U87 cells.It reduced the expression levels of reducing γ-H2AX and Cleaved caspase-3, while increased the expression levels of p-PI3K and p-AKT. Conclusion Silencing lncRNA HCP5 can enhance the radiation sensitivity of glioma cells and promote apoptosis.The mechanism may be related with the miR-508-3p and PI3K/Akt signaling pathway, which will provide new targets and new ideas for glioma treatment. Key words: LncRNA HCP5; MicroRNA-508-3p; Glioma; Radiosensitivity; Apoptosis

Circular RNA circPITX1 knockdown inhibits glycolysis to enhance radiosensitivity of glioma cells by miR-329-3p/NEK2 axis

BackgroundNumerous circular RNAs (circRNAs) have been recognized as vital modulators of human malignancies, including glioma. Whereas, the functional role of circRNA Pituitary Homeo Box 1 (circPITX1) in the radioresistance of glioma cells remains largely uncertain.MethodsQuantitative real-time PCR (qRT-PCR) or western blot analysis was employed to examine the expression of circPITX1, microRNA (miR)-329-3p and NIMA-related kinase 2 (NEK2). 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) assay was used to determine cell viability. Glycolysis was assessed by commercial kits and western blot analysis. Colony formation assay was conducted to analyze cell survival and clonogenicity capacity. The relationship among circPITX1, miR-329-3p and NEK2 was confirmed via dual-luciferase reporter assay. The in vivo function of circPITX1 was evaluated by tumor xenograft assay.ResultsExpression of circPITX1 and NEK2 was up-regulated in glioma tissues and cells, while miR-329-3p exhibited reverse trend. CircPITX1 knockdown repressed viability, glycolysis and colony formation, but promoted radiosensitivity of glioma cells, as well as inhibited tumor growth in vivo. MiR-329-3p was a target miRNA of circPITX1 and miR-329-3p deficiency reversed knockdown of circPITX1-mediated glycolysis inhibition and radioresistance reduction. MiR-329-3p exerted inhibitory effects on glycolysis and radioresistance of glioma cells by targeting NEK2. CircPITX1 facilitated NEK2 expression by sponging miR-329-3p. Glycolytic inhibitor 2-deoxy-d-glucose (2-DG) disposition weakened the promoted impact on glycolysis caused by circPITX1.ConclusionCircPITX1 knockdown reduced glycolysis to contribute to radiosensitivity in glioma through miR-329-3p/NEK2 axis, providing a possible mechanism of circPITX1 in the development of glioma.

Overexpression of XIST facilitates cell proliferation, invasion and suppresses cell apoptosis by reducing radio-sensitivity of glioma cells via miR-329-3p/CREB1 axis.

Glioma is a malignant brain cancer capable of spreading to the microenvironment. Long non-coding RNA (lncRNA) X inactive specific transcript (XIST) was recognized as a significant regulator in many cancers. However, the molecular mechanism of XIST in glioma cell radio-sensitivity requires further exploration. The expression of XIST, microRNA (miR)-329-3p and cyclic AMP response element-binding protein 1 (CREB1) was evaluated by quantitative Real-time polymerase chain reaction (qRT-PCR). Cell viability and apoptosis were examined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and flow cytometry, respectively. Transwell assay was performed to detect cell invasion. Protein expression of gamma-H2AX (γ-H2AX) and CREB1 was determined by Western blot. The correlation between miR-329-3p and XIST or CREB1 was determined by dual-luciferase reporter assay. Animal models were established by subcutaneously injecting U251 cells transfected with sh-XIST and sh-NC. XIST and CREB1 were overexpressed whereas miR-329-3p was low-expressed in glioma tumors and cells compared with the normal counterparts. XIST knockdown inhibited cell proliferation, invasion and induced cell apoptosis by enhancing cell sensitivity to X-ray radiation in glioma. Then, we discovered that miR-329-3p directly interacted with XIST or CREB1 in glioma. In addition, miR-329-3p inhibitor abolished XIST silencing-induced regulatory effects on cell proliferation, apoptosis, invasion, and radio-sensitivity. Meanwhile, miR-329-3p inhibitor counteracted CREB1 silencing-induced inhibition on cell progression and facilitation on radio-sensitivity in glioma. Moreover, we found that XIST could increase CREB1 expression by sponging miR-329-3p. Animal experiments revealed that XIST silencing restrained tumor growth in vivo. XIST accelerates cell proliferation, invasion and inhibits cell apoptosis by repressing radio-sensitivity of glioma via enhancing CREB1 expression through sponging miR-329-3p, representing prospective methods for glioma treatment.