Radioresistance Of Glioma Cells Research Articles

Hypofractionated Radiation Therapy Suppresses Radioresistance in U87 Human Glioma Cells by Inhibiting Yap1 and Hsp90 Proteins.

Radiotherapy plays a vital role in the management of high-grade gliomas. However, the radio resistance of glioma cells limits the effect of radiation and drives recurrence inside the irradiated tumor volume leading to poor outcomes for patients. High-grade glioma cell radioresistance significantly contributes to radiotherapy failure, highlighting the importance of identifying predictive biomarkers for radioresistance. An increasing body of evidence complies with the Yes Associated Protein 1 (Yap-1) and heat shock protein 90 (Hsp90) as biomarkers for radioresistance in glioma cells. A number of studies suggest the potential of radioresistance-associated factors as biomarkers and/ or novel therapeutic targets in glioma cells. Thus, it is essential for glioblastoma patients to identify robust druggable targets involved in radioresistance, optimizing irradiation protocol, and understanding their underlying molecular mechanisms. Therefore, in the present study, we hypothesized that hypofractionated Gamma Knife radiation therapy (HF-GKRT) could target Yap-1 and Hsp90 and downregulate the mechanism of radioresistance in high-grade glioma cells. For this purpose, expression levels of radioresistance markers Yap-1 and Hsp90 were evaluated after treatment with HF-GKRT, and this was compared with single fraction Gamma Knife radiation therapy (SF-GKRT) in U87MG primary human glioblastoma cell line model. This would help design a novel radiation therapy regimen for glioblastoma patients by reducing the risk of radioresistance.

HJURP is recruited to double-strand break sites and facilitates DNA repair by promoting chromatin reorganization.

HJURP is overexpressed in several cancer types and strongly correlates with patient survival. However, the mechanistic basis underlying the association of HJURP with cancer aggressiveness is not well understood. HJURP promotes the loading of the histone H3 variant, CENP-A, at the centromeric chromatin, epigenetically defining the centromeres and supporting proper chromosome segregation. In addition, HJURP is associated with DNA repair but its function in this process is still scarcely explored. Here, we demonstrate that HJURP is recruited to DSBs through a mechanism requiring chromatin PARylation and promotes epigenetic alterations that favor the execution of DNA repair. Incorporation of HJURP at DSBs promotes turnover of H3K9me3 and HP1, facilitating DNA damage signaling and DSB repair. Moreover, HJURP overexpression in glioma cell lines also affected global structure of heterochromatin independently of DNA damage induction, promoting genome-wide reorganization and assisting DNA damage response. HJURP overexpression therefore extensively alters DNA damage signaling and DSB repair, and also increases radioresistance of glioma cells. Importantly, HJURP expression levels in tumors are also associated with poor response of patients to radiation. Thus, our results enlarge the understanding of HJURP involvement in DNA repair and highlight it as a promising target for the development of adjuvant therapies that sensitize tumor cells to irradiation.

Exploration of the radiosensitivity-related prognostic risk signature in patients with glioma: evidence from microarray data

BackgroundGene expression signatures can be used as prognostic biomarkers in various types of cancers. We aim to develop a gene signature for predicting the response to radiotherapy in glioma patients.MethodsRadio-sensitive and radio-resistant glioma cell lines (M059J and M059K) were subjected to microarray analysis to screen for differentially expressed mRNAs. Additionally, we obtained 169 glioblastomas (GBM) samples and 5 normal samples from The Cancer Genome Atlas (TCGA) database, as well as 80 GBM samples and 4 normal samples from the GSE7696 set. The “DESeq2” R package was employed to identify differentially expressed genes (DEGs) between the normal brain samples and GBM samples. Combining the prognostic-related molecules identified from the TCGA, we developed a radiosensitivity-related prognostic risk signature (RRPRS) in the training set, which includes 152 patients with glioblastoma. Subsequently, we validated the reliability of the RRPRS in a validation set containing 616 patients with glioma from the TCGA database, as well as an internal validation set consisting of 31 glioblastoma patients from the Nanfang Hospital, Southern Medical University.ResultsBased on the microarray and LASSO COX regression analysis, we developed a nine-gene radiosensitivity-related prognostic risk signature. Patients with glioma were divided into high- or low-risk groups based on the median risk score. The Kaplan–Meier survival analysis showed that the progression-free survival (PFS) of the high-risk group was significantly shorter. The signature accurately predicted PFS as assessed by time-dependent receiver operating characteristic curve (ROC) analyses. Stratified analysis demonstrated that the signature is specific to predict the outcome of patients who were treated using radiotherapy. Univariate and multivariate Cox regression analysis revealed that the predictor was an independent predictor for the prognosis of patients with glioma. The prognostic nomograms accompanied by calibration curves displayed the 1-, 2-, and 3-year PFS and OS in patients with glioma.ConclusionOur study established a new nine-gene radiosensitivity-related prognostic risk signature that can predict the prognosis of patients with glioma who received radiotherapy. The nomogram showed great potential to predict the prognosis of patients with glioma treated using radiotherapy.

SDPS-17 COMPREHENSIVE ANALYSIS OF CELL DIVISION CYCLE ASSOCIATED GENE FAMILY EXPRESSION PATTERN AND PROGNOSIS VALUE REVEALS CDCA2 AS A NOVEL ONCOGENE FOR GLIOMA

Abstract Glioma is the most common central nervous system tumors. Although many biomarkers have been reported for detecting glioma, the prognosis for the disease remains poor, and therefore, new biomarkers need to be identified. The cell division cycle associated proteins (CDCA) family gene is involved in a wide range of biological functions in human cancers. Nevertheless, the expression characteristics of CDCAs, and prognostic value landscape of glioma are remain unknown. Based on a wide variety of public databases and integrated several bioinformatics analysis methods, we evaluated expression dysregulations, clinical implications, DNA methylation, copy number alterations, prognostic and therapeutic values of CDCA family gene in glioma. Further, we identified crucial biomarker, CDCA2, that influence the progression of malignant glioma and poor prognosis. Thereafter, we disclosed the effect of CDCA2 knockdown on the biological function of glioma cells through various experiments in vitro. We found that the elevated mRNA expression of CDCAs in glioma. The upregulated expression of CDCAs was found to be associated with the tumor grade in glioma. The overexpression of CDCAs mRNA were correlated with the poor prognosis. Moreover, the expression level of CDCA2 was significantly higher in glioma, and the level is correlated with grade, age, IDH1 mutation and 1p19q codeletion states. Further cell experimental results supported that the ability of cell proliferation, migration, invasion and radioresistance of glioma cells was significantly decreased after downregulated CDCA2 expression, and these changes may be achieved through the RAD51 and p21/CDK2/CyclinE1 signaling pathways. These findings provide new insights into CDCAs from a bioinformatics standpoint and highlight the significance of CDCAs in glioma diagnosis and treatment. And knockdown of CDCA2 inhibits glioma cells' proliferation, migration, invasion and radioresistance. Regulation of CDCA2 on malignant progression of glioma cells may be realized through the RAD51 and p21/CDK2/CyclinE1 signaling pathways.

Radiation induces IRAK1 expression to promote radioresistance by suppressing autophagic cell death via decreasing the ubiquitination of PRDX1 in glioma cells

Radiotherapy is the standard adjuvant treatment for glioma patients; however, the efficacy is limited by radioresistance. The function of Interleukin-1 receptor associated kinase 1 (IRAK1) in tumorigenesis and radioresistance remains to be elucidated. IRAK1 expression and its correlation with prognosis were analyzed in glioma tissues. We found that glioma patients with overexpressed IRAK1 show a poor prognosis. Notably, ionizing radiation (IR) remarkably induces IRAK1 expression, which was decreased by STING antagonist H-151 treatment. JASPAR prediction, ChIP assays, and dual luciferase reporter assays indicated that transcription factor FOXA2, suppressed by STING inhibition, directly binds to the IRAK1 promoter region and activates its transcription. IRAK1 knockdown inhibits malignancy and enhances the radiosensitivity of glioma in vitro and in vivo. To explore the potential IRAK1 interacting targets mediating the radioresistance of glioma cells, IP/Co-IP, LC-MS/MS, GST pull-down, and ubiquitination analyses were conducted. Mechanistically, IRAK1 bound to PRDX1, a major member of antioxidant enzymes, and further prevents ubiquitination and degradation of PRDX1 mediated by E3 ubiquitin ligase HECTD3; Both the DOC and HECT domains of HECTD3 directly interacted with PRDX1 protein. Overexpression of PRDX1 reverses the radiotherapy sensitization effect of IRAK1 depletion by diminishing autophagic cell death. These results suggest the IRAK1-PRDX1 axis provides a potential therapeutic target for glioma patients.

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.

Oncogenic magnesium transporter 1 upregulates programmed death-1-ligand 1 expression and contributes to growth and radioresistance of glioma cells through the ERK/MAPK signaling pathway

ABSTRACT Radiotherapy has been established as a major therapeutic modality for glioma, whereas new therapeutic targets are needed to prevent tumor recurrence. This study intends to explore the regulatory role of magnesium transporter 1 (MAGT1) in radiotherapy resistance of glioma through modulating ERK and programmed death-1-ligand 1 (PD-L1). Our bioinformatics analysis identified differentially expressed MAGT1 in glioma, expression of which was subsequently determined in cohort data of TCGA database and microarray dataset as well as glioma cell lines. Artificial modulation of MAGT1, ERK, and PD-L1 expression was performed to examine their effects on glioma cell proliferation and radioresistance, as reflected by MTT and colony formation assays under irradiation. Mouse glioma cells with manipulated MAGT1 and ERK inhibitors were further injected into mice to assess the in vivo tumor formation ability of glioma cells. It was noted that MAGT1 expression was highly expressed in glioma tissues of TCGA data and microarray dataset, which was then validated in glioma cell lines. Ectopic expression of MAGT1 was revealed to promote the proliferation and radioresistance of glioma cells, which was attributed to the MAGT1-mediated activation of the ERK/MAPK signaling pathway. It was illuminated that MAGT1 stimulated PD-L1 expression through the ERK/MAPK pathway and thus facilitated glioma cell growth. Additionally, MAGT1 overexpression accelerated the in vivo tumor formation of glioma cells, while the ERK inhibitor negated its effect. In conclusion, MAGT1 enhances the growth and radioresistance of glioma cells through the ERK/MAPK signaling pathway-mediated upregulation of PD-L1 expression.

Downregulation of SFRP2 facilitates cancer stemness and radioresistance of glioma cells via activating Wnt/β-catenin signaling.

Secreted frizzled-related protein 2 (SFRP2) is a glycoprotein with frizzled-like cysteine-rich domain that binds with Wnt ligands or frizzled receptors to regulate Wnt signaling. SFRP2 is frequently hypermethylated in glioma patients, and analysis of TCGA data indicates that SFRP2 is one of the most downregulated genes in radiotherapy treated glioma patients. In the present study, we aimed to explore the potential function of SFRP2 in tumorigenesis and radioresistance of glioma. The RNA sequencing data of TCGA glioma samples were downloaded and analyzed. SFRP2 expression in 166 glioma patients was evaluated by qRT-PCR. The potential functions of SFRP2 in glioma were evaluated by loss-of-function assays and gain-of-function assays in glioma cell lines. We found that SFRP2 was downregulated in radiotherapy-treated glioma patients, and low SFRP2 expression was correlated with advanced tumor stage and poor prognosis. CRISP/Cas9-meidated SFRP2 knockdown promoted soft agar colony formation, cancer stemness and radioresistance of glioma cells, while enforced SFRP2 expression exhibited opposite effects. Moreover, Wnt/β-catenin signaling was activated in radiotherapy treated glioma patients. SFRP2 knockdown activated Wnt/β-catenin signaling in glioma cell lines, while overexpression of SFRP2 inhibited Wnt/β-catenin activation. Besides, pharmacological inhibition of Wnt/β-catenin signaling by XAV-939 abrogated the effects of SFRP2 knockdown on cancer stemness and radioresistance of glioma cells. Our data for the first time demonstrated a role of SFRP2 in radioresistance of glioma cells, and suggested that inhibition of Wnt/β-catenin signaling might be a potential strategy for increasing radiosensitivity of glioma patients.

LINC01123 potentially correlates with radioresistance in glioma through the miR-151a/CENPB axis.

Radiotherapy represents the most effective nonsurgical therapy, whereas acquired radioresistance remains a major challenge in glioma treatment. Deregulation of long noncoding RNAs (lncRNAs) is frequently involved in tumorigenesis. This study investigates the role of LINC01123 in radioresistance in glioma with molecules involved. LINC01123 was identified as the most upregulated gene in a glioma gene expression dataset GSE103227. LINC01123 was highly expressed in the radioresistant glioma tissues radioresistant glioma U251 (U251R) cells. Downregulation of LINC01123 reduced cell proliferation and colony formation abilities, as well as resistance to apoptosis of the U251R cells after 4 Gy X-ray irradiation. The micro(mi)RNA-151a gene (miR-151a) was a poorly expressed miRNA in glioma, and it was a target of LINC01123. The centromere protein B gene (CENPB) mRNA was a direct target of miR-151a and demonstrated a positive correlation with LINC01123 in glioma tissues and cells. Further inhibition of miR-151a or overexpression of CENPB restored radioresistance of glioma cells. In addition, silencing of LINC01123 suppressed growth of xenograft tumors formed by U251R cells in nude mice. To conclude, the present study demonstrates that LINC01123 serves as a sponge for miR-151a and upregulates CENPB expression to increase the radioresistance of glioma cells in vitro and in vivo.

SP1 transcriptionally activates NLRP6 inflammasome and induces immune evasion and radioresistance in glioma cells

Glioma accounts for approximately 80% of all malignant brain tumors. This study aimed to investigate the interaction between specificity protein 1 (SP1) and NLR family pyrin domain containing 6 (NLRP6) and their roles in the activity of glioma cells. Differentially expressed genes in glioma were identified using transcriptome analysis tools, and a protein-protein-interaction network was performed based on the DEGs. SP1 and NLRP6 were abundantly expressed in glioma cells and indicated unfavorable prognosis of patients according to the GEO datasets. SP1could bind to the promoter of NLRP6 and induce its transcriptional activity. Downregulation of SP1 reduced proliferation, migration and invasion of glioma U87 cells in vitro as well as tumorigenesis in vivo. The malignancy of cells was restored after NLRP6 upregulation. Downregulation of SP1 in glioma cells also increased proliferation of CD8+ T cells and the immune activity in U87 cells, and it reduced the radioresistance of U87 cells. However, the immune evasion and radioresistance of glioma cells were restored upon NLRP6 upregulation. NLRP6 mediated the innate immune pathway through an ASC/caspase-1/IL-1β axis. To conclude, this study suggested that SP1 interacts with NLRP6 inflammasome to enhance malignant behaviors, immune evasion and radioresistance in glioma cells.

Differential gene expression in peritumoral brain zone of glioblastoma: role of SERPINA3 in promoting invasion, stemness and radioresistance of glioma cells and association with poor patient prognosis and recurrence.

Glioblastoma (GBM) is a highly invasive tumor. Despite advances in treatment modalities, tumor recurrence is common, seen mainly in the peritumoral brain zone (PBZ). We aimed to molecularly characterize PBZ, to understand the pathobiology of tumor recurrence. We selected eight differentially regulated genes from our previous transcriptome profiling study on tumor core and PBZ. Expression of selected genes were validated in GBM (tumor core and PBZ, n = 37) and control (n = 22) samples by real time quantitative polymerase chain reaction (qPCR). Serine protease inhibitor clade A, member 3 (SERPINA3) was selected for further functional characterization in vitro by gene knockdown approach in glioma cells. Its protein expression by immunohistochemistry (IHC) was correlated with other clinically relevant GBM markers, patient prognosis and tumor recurrence. The mRNA expression of selected genes from the microarray data validated in tumor core and PBZ and was similar to publicly available databases. SERPINA3 knock down in vitro showed decreased tumor cell proliferation, invasion, migration, transition to mesenchymal phenotype, stemness and radioresistance. SERPINA3 protein expression was higher in PBZ compared to tumor core and also was higher in older patients, IDH wild type and recurrent tumors. Finally, its expression showed positive correlation with poor patient prognosis. SERPINA3 expression contributes to aggressive GBM phenotype by regulating pro-tumorigenic actions in vitro and is associated with adverse clinical outcome.

Linc-RA1 inhibits autophagy and promotes radioresistance by preventing H2Bub1/USP44 combination in glioma cells

Radiotherapy is one of the standard treatments for glioma patients; however, its clinical efficacy is limited by radioresistance. We identified a mechanism of such resistance mediated by linc-RA1 (radioresistance-associated long intergenic noncoding RNA 1). Linc-RA1 was upregulated in radioresistant glioma cells and glioma tissue samples, compared with radiosensitive cells and nontumor tissues. Linc-RA1 was associated with inferior overall survival and advanced clinical stage of glioma. Linc-RA1 promoted glioma radioresistance in vitro and in vivo. Mechanistically, linc-RA1 stabilized the level of H2B K120 monoubiquitination (H2Bub1) by combining with H2B and inhibiting the interaction between H2Bub1 and ubiquitin-specific protease 44 (USP44), which inhibited autophagy, thus contributing to glioma radioresistance. These results reveal that linc-RA1-mediated autophagy is a key mechanism of radioresistance and is an actionable target for improving radiotherapy efficacy in patients with glioma.

Long Noncoding RNA TP53TG1 Contributes to Radioresistance of Glioma Cells Via miR-524-5p/RAB5A Axis.

Background: Long noncoding RNAs (lncRNAs) have been reported to be important regulators in cancer. In this study, we aimed to discover the functions of lncRNA TP53TG1 in glioma. Methods: The expression of lncRNA TP53TG1, microRNA-524-5p (miR-524-5p) and RAB5A, a member RAS oncogene family (RAB5A), were examined by quantitative real-time polymerase chain reaction. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry were applied to analyze the proliferation and apoptosis of glioma cells. Colony formation assay was used to detect the colony formation ability and radioresistance of glioma cells. Western blot assay was performed to detect the expression of autophagy-associated proteins and RAB5A. StarBase software was utilized to predict the combination between miR-524-5p and TP53TG1 or RAB5A, and dual-luciferase reporter assay and RNA immunoprecipitation assay were used to verify the above predictions. Animal experiment using immunodeficient nude mice was conducted to detect the role of TP53TG1 in vivo. Results: Radiation stimulation (6 Gy) upregulated the abundance of TP53TG1. TP53TG1 potentiated radioresistance and progression of glioma by promoting the autophagy. miR-524-5p was verified as a direct downstream regulation of TP53TG1. miR-524-5p depletion attenuated the influence of TP53TG1 interference on the functions of glioma cells. RAB5A was a direct target of miR-524-5p as well. The inhibitory effect of miR-524-5p on the malignancy of glioma cells was overturned by overexpression of RAB5A. RAB5A was regulated by TP53TG1/miR-524-5p signaling in glioma cells. TP53TG1 silencing impeded the progression of glioma in vivo. Conclusion: lncRNA TP53TG1 accelerated the proliferation, colony formation, autophagy, and radioresistance, and restrained the apoptosis of glioma cells through miR-524-5p/RAB5A axis.

NCK1-AS1 enhances glioma cell proliferation, radioresistance and chemoresistance via miR-22-3p/IGF1R ceRNA pathway

Glioma is the deadliest disease in human central nerve system. Abnormal expression of long noncoding RNA (lncRNA) expression has been demontrated to be implicated in various cancers. The oncogenic role of lncRNA NCK1-AS1 has been validated in cervical cancer, wheras its role in glioma remians obscure. Our research findings suggested that NCK1-AS1 was upregulated in glioma tissues and cells. NCK1-AS1 deficiency hindered cell proliferation and enhanced cell apoptosis. Additionally, the chemoresistance and radioresistance of glioma cells were impaired by NCK1-AS1 depletion. Moreover, miR-22-3p, a downstream gene of NCK1-AS1, could weaken glioma cell chemoresistance and radioresistance. Similarly, IGF1R was the downstream target gene of miR-22-3p. Further mechanism and function assays demonstrated that NCK1-AS1 promoted glioma cell growth, chemoresistance and radioresistance via sponging miR-22-3p to upregulate IGF1R. Finally, the tumor facilitator function of NCK1-AS1 was also verified by in vivo experiments. Taken together, NCK1-AS1 contributes to glioma cell proliferation, radioresistance and chemoresistance via miR-22-3p/IGF1R ceRNA pathway, which might provide a new insight for improving the radiotherapy and chemotherapy treatments of glioma.

Inhibition of mitochondria NADH–Ubiquinone oxidoreductase (complex I) sensitizes the radioresistant glioma U87MG cells to radiation

Radiation is a current standard treatment of glioma. The fractionated radiotherapy with low dose of radiation over weeks has been employed in glioma patients, while radiotherapy can only offer palliation due to the radioresistance. We cumulatively radiated a glioblastoma cell line, U87MG, and screened radioresistant glioma cells. A transcriptome sequencing was performed to analyze the transcription differences between the raidoresistant and control cells, which showed the mitochondria NADH–ubiquinone oxidoreductase (Complex I) subunits were up-regulated in the radioresistant cells. The copy numbers of mitochondria were increased in the radioresistant glioma cells. After using mitochondria Complex I inhibitors, rotenone and metformin, to treat glioma cells, we found the resistant glioma cells re-sensitized to radiation. These results demonstrate that Complex I is associated with the fractioned radiation-induced radioresistance of glioma and would be a potent target for clinical radiotherapy of glioma.

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.

Enhancement of Radiosensitization by Silver Nanoparticles Functionalized with Polyethylene Glycol and Aptamer As1411 for Glioma Irradiation Therapy.

BackgroundThe efficacy of radiotherapy for glioma is often limited by the radioresistance of glioma cells. The radiosensitizing effects of silver nanoparticles (AgNPs) on glioma were found in the previous studies of our group. In order to enhance the radiosensitivity of tumor cells and selectively kill them while reducing the side effects of irradiation therapy, targeted modification of AgNPs is urgently needed.Materials and methodsIn the present study, AgNPs functionalized with polyethylene glycol (PEG) and aptamer As1411 (AsNPs) were synthesized and subsequently characterized by transmission electron microscopy, ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. Then the targeting property of AsNPs was evaluated by dark-field imaging, confocal microscopy and in vivo imaging. Both colony formation assay and glioma-bearing mouse model were employed to study the radiosensitizing effect of AsNPs.ResultsThe characterization results revealed a spherical shape of AgNPs with an average diameter of 18 nm and the successful construction of AsNPs. AsNPs were confirmed to specifically target C6 glioma cells, but not normal human microvascular endothelial cells. Moreover, AsNPs could not only internalize into tumor cells, but also penetrate into the core of tumor spheroids. In vitro experiments showed that AsNPs exhibited a better radiosensitizing effect than AgNPs and PEGylated AgNPs (PNPs), inducing a higher rate of apoptotic cell death. In vivo imaging demonstrated that Cy5-AsNPs preferentially accumulated at the tumor site, and the ratio of fluorescence intensity of Cy5-AsNPs to that of Cy5-PNPs reached the maximum at 6 h post-systemic administration. Furthermore, the combination of AsNPs with irradiation significantly prolonged the median survival time of C6 glioma-bearing mice.ConclusionOur results indicated that AsNPs could be an effective nano-radiosensitizer for glioma targeting treatment.

IDH1-R132H mutation radiosensitizes U87MG glioma cells via epigenetic downregulation of TIGAR.

Isocitrate dehydrogenase 1 (IDH1) is the most frequently mutated gene in World Health Organization grade II–III and secondary glioma. The majority of IDH1 mutation cases involve the substitution from arginine to histidine at codon 132 (IDH1-R132H). Although the oncogenic role of IDH1-R132H has been confirmed, patients with IDH1-R132H brain tumors exhibit a better response to radiotherapy compared with those with wild-type (WT) IDH1. In the present study, the potential mechanism of radiosensitization mediated by IDH1-R132H was investigated by overexpressing IDH1-R132H in U87MG glioma cells. The results demonstrated decreased clonogenic capacity of IDH1-R132H-expressing cells, as well as delayed repair of DNA double-strand breaks compared with IDH1-WT. Data from The Cancer Genome Atlas were analyzed, which demonstrated that the expression of TP53-induced glycolysis and apoptosis regulator (TIGAR) was lower in patients with glioma harboring IDH1 mutations compared with that in patients with IDH1-WT. TIGAR-knockdown increases the radiosensitivity of glioma cells; in U87MG cells, IDH1-R132H suppressed TIGAR expression. Chromatin immunoprecipitation assays revealed increased levels of repressive H3K9me3 markers at the TIGAR promoter in IDH1-R132H compared with IDH1-WT. These data indicated that IDH1-R132H may overcome radioresistance in glioma cells through epigenetic suppression of TIGAR expression. However, these favorable effects were not observed in U87MG glioma stem-like cells. The results of the present study provide an improved understanding of the functionality of IDH1 mutations in glioma cells, which may improve the therapeutic efficacy of radiotherapy.

Long Noncoding Ribonucleic Acid SNHG18 Promotes Glioma Cell Motility via Disruption of α-Enolase Nucleocytoplasmic Transport.

Glioma is a common malignancy with poor prognosis. Recent evidence suggests that the pathogenesis and progression of glioma involve long noncoding RNAs (lncRNAs). Previously, we showed that glioma cell radioresistance was enhanced by lncRNA SNHG18 in vitro and in vivo. In the present study, we showed that SNHG18 promoted the invasion and migration of glioma cells. SNHG18 was demonstrated to regulate the progression of epithelial-mesenchymal transition and cytoskeleton remodeling, thereby affecting cell motility. Furthermore, the promotion of invasion evoked by SNHG18 overexpression could be rescued by α-enolase (ENO1) deletion. Moreover, rather than altering ENO1 expression, SNHG18 suppressed its nucleocytoplasmic transport by directly combining with ENO1 in glioma cells. The results suggested that SNHG18 inhibited the nucleocytoplasmic transport of ENO1 to promote cell motility. The results reveal the mechanism by which this lncRNA affects tumorigenesis and metastasis, forming the basis for further research that will lead to novel strategies to treat glioma.

Effect of SSH1/SSH2 expression changes by shRNA in glioma cell lines on response to radiotherapy and cofilin-1 reactivation.

e13505 Background: Radiotherapy has become the most important treatment for malignant glioma following surgery. However, development of radioresistance in glioma cells limits therapeutic efficacy. The slingshot (SSH) family of phosphatases is a potent regulator of Cofilin-1 activation. Methods: We investigate the role of SSH1(slingshot protein phosphatase 1) and SSH2 in radioresistance via using shRNA to block SSH1/2 expression in U251 and U373 cells as well as established radioresistant U251 (RR-U251) and U373 (RR-U373) cells. Results: We found that both SSH1 and SSH2-shRNA efficiently sensitized glioma cells to radiation with a sensitization enhancement ratio (SER) of 1.01-1.73. In SSH1-silenced cells, the cell viability, migration, and invasion abilities following radiation were remarkably reduced and radiation induced cell apoptosis was markedly enhanced compared with control cells. While in SSH2-silenced cells, the alterations were not as significant. Furthermore, the result of Western-blot suggested that radiosensization of SSH1/SSH2 silencing was mediated by inhibiting reactivation of phosphorylated CFL-1. Conclusions: Our study demonstrated that SSH1 and SSH2 are valid radiosensitizing targets in not only normal glioma cells but radioresistant lines, suggesting a novel therapeutic strategy to improve the efficacy of radiotherapy in patients with glioma.