NUDT5 promotes the growth,metastasis,and Warburg effect of IDH wild-type glioblastoma multiforme cells by upregulating TRIM47

Objective:To explore the regulatory mechanism of NUDT5 in glioblastoma multiforme(GBM).Methods:GEPIA database was used to predict the expressions of NUDT5 and tripartite motif family proteins 47(TRIM47)in GBM patients.RT-qPCR and Western blot analyses were performed to examine NUDT5 expression in GBM cells.LN-229 cell proliferation,migration as well as invasion were estimated by CCK-8,colony formation,wound healing,and Transwell assays following interference with NUDT5.ECAR assay,L-lactic acid kit,glucose detection kit,and ATP detection kit were applied for the detection of glycolysis-related indexes.Co-immunoprecipitation experiment was carried out to verify the relationship between NUDT5 and TRIM47.Results:GEPIA database showed that NUDT5 expression was significantly increased in GBM patients.Inhibiting the expression of NUDT5 in GBM cells significantly suppressed the viability,proliferation,invasion,migration,and glycolysis of GBM cells.Moreover,TRIM47 was highly expressed in GBM cells and interacted with NUDT5.Overexpression of TRIM47 partially reversed the inhibitory effect of NUDT5 downregulation on the proliferation,metastasis,and glycolysis of GBM cells.Conclusions:NUDT5 promotes the growth,metastasis,and Warburg effect of GBM cells by upregulating TRIM47.Both NUDT5 and TRIM47 can be used as targets for GMB treatment.

Hypoxia-inducible factor 1alpha and vascular endothelial growth factor in Glioblastoma Multiforme:a systematic review going beyond pathologic implications

Glioblastoma multiforme(GBM)is an aggressive primary brain tumor characterized by extensive heterogeneity and vascular proliferation.Hypoxic conditions in the tissue microenvironment are considered a pivotal player leading tumor progression.Specifically,hypoxia is known to activate inducible factors,such as hypoxia-inducible factor 1alpha(HIF-1α),which in turn can stimulate tumor neo-angiogenesis through activation of various downward mediators,such as the vascular endothelial growth factor(VEGF).Here,we aimed to explore the role of HIF-1α/VEGF immunophenotypes alone and in combination with other prognostic markers or clinical and image analysis data,as potential biomarkers of GBM prognosis and treatment efficacy.We performed a systematic review(Medline/Embase,and Pubmed database search was completed by 16th of April 2024 by two independent teams;PRISMA 2020).We evaluated methods of immunoassays,cell viability,or animal or patient survival methods of the retrieved studies to assess unbiased data.We used inclusion criteria,such as the evaluation of GBM prognosis based on HIF-1α/VEGF expression,other biomarkers or clinical and imaging manifestations in GBM related to HIF-1α/VEGF expression,application of immunoassays for protein expression,and evaluation of the effectiveness of GBM therapeutic strategies based on HIF-1α/VEGF expression.We used exclusion criteria,such as data not reporting both HIF-1αand VEGF or prognosis.We included 50 studies investigating in total 1319 GBM human specimens,18 different cell lines or GBM-derived stem cells,and 6 different animal models,to identify the association of HIF-1α/VEGF immunophenotypes,and with other prognostic factors,clinical and macroscopic data in GBM prognosis and therapeutic approaches.We found that increased HIF-1α/VEGF expression in GBM correlates with oncogenic factors,such as miR-210-3p,Oct4,AKT,COX-2,PDGF-C,PLDO3,M2 polarization,or ALK,leading to unfavorable survival.Reduced HIF-1α/VEGF expression correlates with FIH-1,ADNP,or STAT1 upregulation,as well as with clinical manifestations,like epileptogenicity,and a favorable prognosis of GBM.Based on our data,HIF-1αor VEGF immunophenotypes may be a useful tool to clarify MRI-PET imaging data distinguishing between GBM tumor progression and pseudoprogression.Finally,HIF-1α/VEGF immunophenotypes can reflect GBM treatment efficacy,including combined first-line treatment with histone deacetylase inhibitors,thimerosal,or an active metabolite of irinotecan,as well as STAT3 inhibitors alone,and resulting in a favorable tumor prognosis and patient survival.These data were supported by a combination of variable methods used to evaluate HIF-1α/VEGF immunophenotypes.Data limitations may include the use of less sensitive detection methods in some cases.Overall,our data support HIF-1α/VEGF’s role as biomarkers of GBM prognosis and treatment efficacy.

Nanosensitizers for sonodynamic therapy for glioblastoma multiforme: current progress and future perspectives

Glioblastoma multiforme(GBM) is the most common primary malignant brain tumor, and it is associated with poor prognosis. Its characteristics of being highly invasive and undergoing heterogeneous genetic mutation, as well as the presence of the blood–brain barrier(BBB), have reduced the efficacy of GBM treatment. The emergence of a novel therapeutic method, namely, sonodynamic therapy(SDT), provides a promising strategy for eradicating tumors via activated sonosensitizers coupled with low-intensity ultrasound. SDT can provide tumor killing effects for deep-seated tumors, such as brain tumors. However, conventional sonosensitizers cannot effectively reach the tumor region and kill additional tumor cells, especially brain tumor cells. Efforts should be made to develop a method to help therapeutic agents pass through the BBB and accumulate in brain tumors. With the development of novel multifunctional nanosensitizers and newly emerging combination strategies, the killing ability and selectivity of SDT have greatly improved and are accompanied with fewer side effects. In this review, we systematically summarize the findings of previous studies on SDT for GBM, with a focus on recent developments and promising directions for future research.

Glioblastoma multiforme:Diagnosis, treatment, and invasion

Glioblastoma multiforme(GBM) is an essentially incurable brain tumor, which has been explored for approximately a century. Nowadays, surgical resection, chemotherapy, and radiation therapy are still the standardized therapeutic options. However, due to the intrinsic invasion and metastasis features and the resistance to chemotherapy, the survival rate of glioblastoma patients remains unsatisfactory. To improve the current situation, much more research is needed to provide comprehensive knowledge of GBM. In this review, we summarize the latest updates on GBM treatment and invasion. Firstly, we review the traditional and emerging therapies that have been used for GBM treatment. Given the limited efficiency of these therapies, we further discuss the role of invasion in GBM recurrence and progression, and present current research progress on the mode and mechanisms of GBM invasion.

Exploring Chemovar-Specific Cannabis Extracts Quantification and Evaluation of Cytotoxic Compounds for Targeting Glioblastoma Multiforme

Glioblastoma Multiforme (GBM) represents one of the most aggressive and metastatic brain tumors, with a dismal success rate of less than three percent after five years, particularly in tumors with active immune checkpoints. This necessitates the development of targeted endogenous agents for precise GBM treatment. Previous experiments utilizing Chemovar Specific Cannabis Extractions (CSCEs), fractionated with polar solvents and quantified using Liquid and Gas Column Chromatography combined with Mass Spectrometry (LC/GCMS), have shown reduced viability and motility in human GBM cell lines. However, the complexity of the botanical substance has hindered the personalization of standard cannabis medicines for GBM due to unknown synergistic effects of multiple compounds. To address this limitation, our study focuses on exposing AM251 cells to chemovar fractions extracted using a non-polar solvent, thereby isolating a broader spectrum of constituents. By employing LC/GCMS in conjunction with Nuclear Magnetic Resonance (NMR), we have identified and quantified nine* compounds present in the non-polar CSCE that exhibit significant efficacy (0.1 μM) in inducing cytotoxicity* in GBM tumor cells. Conversely, the polar fraction in our experiment did not demonstrate efficacy against UM251 cells. The quantification of individual compounds within a cannabis extraction that selectively induces cell death in brain tumors holds promise for guiding future research and facilitating the development of a standardized CSCE for GBM therapy.

MRI Manif estions Correlate with Survival of Glioblastoma Multiforme Patients

Objective To identify the correlation between magnetic resonance manifestation and survival of patients with glioblastoma lnultiforme （GBM）, Methods The magnetic resonance imaging （MRI） images of 30 glioblastoma patients were collected. Imaging features including degrees of contrasted area, edema surrounding the tumor; and intensity in T2-weighted imaging were selected to determine their correlation with patient survival. The relationship between imaging and survival time was studied using SPSS 19.0 software. Kaplan- Meier survival analysis and log-rank test were used to compare the survival curves. Results Patients with 〈5% contrasted enhancement area of tumor had longer overall survival （OS） than those with 〉5% contrasted enhancement area of tumor. Patients without edema surrounding the tumor had longer OS than those with edema. Patients with tumor of hyperintensity and/or isointensity in T2-weighted imaging had longer OS than those with hyperintensity and/or isointensity and hypointensity. Conclusions Some MR imaging features including degrees of contrasted area, edema surrounding the tumor, and intensity in T2- weighted imaging are correlated with the survival of patients with GBM. These features can serve as prognostic indicators for GBM patients.

Consideration of transmembrane water exchange in pharmacokinetic model significantly improves the accuracy of DCE-MRI in estimating cellular density:A pilot study in glioblastoma multiforme

Transmembrane water exchange(TWE)including transcytolemmal water exchange and transvascular water exchange is involved in many in vivo measurements and makes different contributions to the measuring results.In this study,we focus on the potential influence of TWE on the cell density parameter,intracellular water mole fraction pi,derived by dynamic contrast enhanced-magnetic resonance imaging(DCE-MRI)which has been reported as a technique to characterize perfusion and vascularization of tissues,but its accuracy in measuring cell density(or interstitial space)has been questioned.Sixteen patients with glioblastoma multiforme(GBM)were enrolled since GBM shows strong intratumor heterogeneity in both cell density and TWE.All the subjects were collected with DCE-MRI and apparent diffusion coefficient(ADC)map.The latter was considered as a valid surrogate of cell density.Extended Tofts(eTofts)model considering TWE as infinitely large variables and shutter-speed model(SSM)considering TWE as finite ones were used to fit DCE-MRI data.Monte Carlo(MC)and finite difference(FD)methods were used to simulate the influence of TWE on DCE-MRI-derived pi and ADC,respectively.The eTofts model shows a significant overestimation of pi in comparison with SSM in GBM(P<0.001),which is in accordance with MC simulations,and this overestimation shows dependence on the intra-to-extracellular water exchange rate constant(kio).Significant negative correlations between ADC and SSM-derived pi were found in both voxel-wise analyses(t-test P<0.001,average r=-0.74)and inter-subject comparisons(r=-0.63,P=0.009).But no consistent voxel-wise correlations(P>0.05)and a weaker inter-subject negative correlation(r=-0.56,P=0.02)were found between ADC and eTofts-derived pi.Further experimental and FD results revealed that kio made a limited contribution to ADC values in the physiological kio range in GBM,supporting ADC as a valid biomarker of cell density.These results suggest that the DCE-MRI pharmacokinetic shutter-speed model could significantly improve its accuracy in cell density estimation because of the considering transmembrane water exchange.

The cuproptosis-related gene signature predicts clinical diagnosis,prognosis,and immune microenvironment for glioblastoma multiforme

Background:Glioblastoma multiforme(GBM)is a kind of extremely malignant brain tumor with a poor prognosis.The problem of high recurrence rates and drug resistance has been difficult to solve.Cuproptosis is a newly discovered mode of cell death,which is related to the occurrence and progression of GBM.Methods:We screened TCGA and GEO databases to comprehensively analyze the regulation patterns of cuproptosis in GBM based on cuproptosis-related genes(CRGs).The expression levels,copy number variants(CNV),and mutation of CRGs in GBM were probed.Different regulation patterns of cuproptosis were identified and performed GSVA analysis.Then we constructed a prognostic model based on genes that were differentially expressed in all regulation patterns.The immune cells and tumor microenvironment in different risk groups were compared.Finally,the potential therapeutic drugs were predicted.Results:We identified two key differentially expressed genes under different regulation patterns of cuproptosis and constructed a risk prognostic model.There were significant differences in immune infiltration and drug sensitivity between high and low risk groups.Conclusions:We established a risk prognostic model based on two genes and explored its relationship with immune characteristics,which might help to assess the prognosis and treatment sensitivity to immune and targeted therapy of GBM patients.

Radiation-Induced Spinal Glioblastoma Multiforme: A Rare Complication in the Management of Head and Neck Cancer

Background: Radiation-induced gliomas of the spinal cord are rare late complications of spinal cord irradiation that typically occur in patients treated at younger ages. Aim: Raise awareness of radiation induced high grade gliomas with a case presentation and a review of the literature. Case Presentation: A 50-year-old male with Stage IVA squamous cell carcinoma of the oropharynx was treated with external beam radiotherapy with a complete response. Seven years later, he presented with a cervical spinal cord mass on MRI. An open biopsy was performed. Pathology revealed an intramedullary WHO grade IV astrocytoma, (i.e., glioblastoma multiforme) of the cervical spine that fulfilled the criteria for a radiation-induced malignancy. Conclusions : Review of the literature suggests that radiation-induced gliomas tend to be high grade and may occur at the periphery of an irradiated field. Radiation-induced gliomas of the spinal cord are a serious complication of radiotherapy that may occur in older patients with head and neck cancers, but are so rare that it should not affect treatment decisions.

Biomaterial-based in vitro 3D modeling of glioblastoma multiforme

Adult-onset brain cancers,such as glioblastomas,are particularly lethal.People with glioblastoma multiforme(GBM)do not anticipate living for more than 15 months if there is no cure.The results of conventional treatments over the past 20 years have been underwhelming.Tumor aggressiveness,location,and lack of systemic therapies that can penetrate the blood–brain barrier are all contributing factors.For GBM treatments that appear promising in preclinical studies,there is a considerable rate of failure in phaseⅠandⅡclinical trials.Unfortunately,access becomes impossible due to the intricate architecture of tumors.In vitro,bioengineered cancer models are currently being used by researchers to study disease development,test novel therapies,and advance specialized medications.Many different techniques for creating in vitro systems have arisen over the past few decades due to developments in cellular and tissue engineering.Later-stage research may yield better results if in vitro models that resemble brain tissue and the blood–brain barrier are used.With the use of 3D preclinical models made available by biomaterials,researchers have discovered that it is possible to overcome these limitations.Innovative in vitro models for the treatment of GBM are possible using biomaterials and novel drug carriers.This review discusses the benefits and drawbacks of 3D in vitro glioblastoma modeling systems.

Prognostic factors influencing clinical outcomes of glioblastoma multiforme

Background Glioblastoma multiforme （GBM） is the most malignant kind of astrocytic tumors and is associated with a poor prognosis. In this retrospective study, we assessed the clinical, radiological, genetic molecular and treatment factors that influence clinical outcomes of patients with GBM. Methods A total of 116 patients with GBM who received surgery and radiation between January 2006 and December 2007 were included in this study. Kaplan-Meier survival analysis and Cox regression analysis were used to find the factors independently influencing patients＇ progression free survival （PFS） time and overall survival （OS） time. Results Age, preoperative Karnofsky Performance Scale （KPS） score, KPS score change at 2 weeks after operation, neurological deficit symptoms, tumor resection extent, maximal tumor diameter, involvement of eloquent cortex or deep structure, involvement of brain lobe, Ki-67 expression level and adjuvant chemotherapy were statistically significant factors （P 〈0.05） for both PFS and OS in the univariate analysis. Cox proportional hazards modeling revealed that age 〈50 years, preoperative KPS score 〉80, KPS score change after operation 〉0, involvement of single frontal lobe, non-eloquent area or deep structure involvement, low Ki-67 expression and adjuvant chemotherapy were independent favorable factors （P 〈0.05） for patients＇ clinical outcomes. Conclusions Age at diagnosis, preoperative KPS score, KPS score change at 2 weeks postoperation, involvement of brain lobe, involvement of eloquent cortex or deep structure, Ki-67 expression level and adjuvant chemotherapy correlate significantly with the prognosis of patients with GBM.

Effect of intensity-modulated radiotherapy versus three-dimensional conformal radiotherapy on clinical outcomes in patients with glioblastoma multiforme

Background Few studies were reported on the comparison of clinical outcomes between intensity-modulated radiotherapy （IMRT） and three-dimensional conformal radiotherapy （3D-CRT） in the treatment of glioblastoma multiforme （GBM）.This study aimed to determine whether IMRT improves clinical outcomes compared with 3D-CRT in patients with GBM.Methods The records of 54 patients with newly-diagnosed GBM from July 2009 to December 2010 were reviewed.The patients underwent postoperative IMRT or 3D-CRT with concurrent and adjuvant temozolomide.Kaplan-Meier method and log rank test were used to estimate differences of patients＇ survival.Results The median follow-up was 13 months.Of the 54 patients,fifty （92.6%） completed the combined modality treatment.The 1-year overall survival rate （OS） was 79.6%.The pattern of failure was predominantly local.A comparative analysis revealed that no statistical difference was observed between the IMRT group （n=21） and the 3D-CRT group （n=33） for 1-year OS （89.6% vs.75.8%,P=0.795）,or 1-year progression-free survival （PFS） （61.0% vs.45.5%,P=0.867）.In dosimetric comparison,IMRT seemed to allow better sparing of organs at risk than 3D-CRT did （P=0.050,P=0.055）.However,there was no significant difference for toxicities of irradiation between the IMRT group and the 3D-CRT group.Conclusions Our preliminary results suggested that delivering standard radiation doses by IMRT is unlikely to improve local control or overall survival for GBM compared with 3D-CRT.Given this lack of survival benefit and increased costs of IMRT,the utilization of IMRT treatment for GBM needs to be carefully rationalized.

Relationship between magnetic resonance imaging and molecular pathology in patients with glioblastoma multiforme

Background Glioblastoma multiforme （GBM） is the most common and lethal primary brain tumor in adults. Magnetic resonance imaging （MRI） is routinely used in the diagnosis, characterization and clinical management of GBM. The diagnosis and treatment of GBM is largely guided by histopathology and immunohistochemistry. This study aimed to identify the relationship between magnetic resonance features and molecular pathology of GBM. Methods MRI images of 43 glioblastoma patients were collected. Four imaging features, degree of edema, contrast tumor enhanced/T2 ratio, multiple lesions and tumor across the midline, were selected to identify their relationship with P53, Ki-67 and O6-methylguanine-DNA methltransferase （MGMT） expression in patients with GBM. The relationship between imaging features and molecular pathology was studied by chi-square test using the software SPSS 13.0. Results High expression of P53 was found correlated with low contrast tumor enhancedFF2 ratio, low expression of Ki-67 was correlated with multiple lesions and high expression of KI-67 may be related with tumor across the midline, low expression of MGMT was correlated with edema. Conclusion Some MRI features such as the degree of edema, contrast tumor enhanced/T2 ratio, multiple lesions and tumor acrossing the midline are correlated with P53, Ki-67 and MGMT of GBM.

Combination immunotherapy of glioblastoma with dendritic cell cancer vaccines,anti-PD-1 and poly I:C

Glioblastoma(GBM)is a lethal cancer with limited therapeutic options.Dendritic cell(DC)-based cancer vaccines provide a promising approach for GBM treatment.Clinical studies suggest that other immunotherapeutic agents may be combined with DC vaccines to further enhance antitumor activity.Here,we report a GBM case with combination immunotherapy consisting of DC vaccines,anti-programmed death-1(anti-PD-1)and poly I:C as well as the chemotherapeutic agent cyclophosphamide that was integrated with standard chemoradiation therapy,and the patient remained disease-free for 69 months.The patient received DC vaccines loaded with multiple forms of tumor antigens,including mRNA-tumor associated antigens(TAA),mRNA-neoantigens,and hypochlorous acid(HOCl)-oxidized tumor lysates.Furthermore,mRNA-TAAs were modified with a novel TriVac technology that fuses TAAs with a destabilization domain and inserts TAAs into full-length lysosomal associated membrane protein-1 to enhance major histocompatibility complex(MHC)class I and II antigen presentation.The treatment consisted of 42 DC cancer vaccine infusions,26 anti-PD-1 antibody nivolumab administrations and 126 poly I:C injections for DC infusions.The patient also received 28 doses of cyclophosphamide for depletion of regulatory T cells.No immunotherapy-related adverse events were observed during the treatment.Robust antitumor CD4t and CD8t T-cell responses were detected.The patient remains free of disease progression.This is the first case report on the combination of the above three agents to treat glioblastoma patients.Our results suggest that integrated combination immunotherapy is safe and feasible for long-term treatment in this patient.A large-scale trial to validate these findings is warranted.

Prognostic significance of annexin VII expression in glioblastomas multiforme in humans

OBJECT:Glioblastoma multiforme(GBM)is the most common and lethal primary brain tumor in adults.It isnearly uniformly fatal,with a median survival time of approximately l year,despite modem treatment modalities.Nevertheless,a range of survival times exists around this median.Efforts to understand why some patients livelonger or shorter than the average may provide insight into the biology of these neoplasms.The annexin VII(ANX7)gene is located on the human chromosome 10q21,a site long hypothesized to harbor tumor

Magnetic Field Emulations of Small Inhibitor RNA: Effects on Implanted GL261 Tumors in C57BL/6 Immune Competent Mice

EMulate Therapeutics has developed a system for emulating the effects of solvated molecules via their magnetic field recordings. Recordings of magnetic field emissions of select small inhibitor RNAs (siRNAs;murine targeting CTLA-4 and murine targeting PD-1) were tested on C57Bl/6 mice implanted subcutaneously with the GL261 murine tumor cell line. A signal composed of concatenated recordings of siRNA molecules targeting the murine CTLA-4 and PD-1 receptors (labeled A2) was used in immune competent C57Bl/6 mice. The mice were flank implanted with the murine glioblastoma cell line GL261. Mice were exposed to the signal continuously (24 hours a day) until tumor volumes reached the designated volume limit. Tumors were excised and analyzed via PAGE/Western blot for the expression of CTLA-4, PD-1, Ki67, Caspase 3, CD4 and CD8. Terminal blood draws were used for CBCs. We report the down regulation of the checkpoint inhibitors CTLA-4 in the exposed mice. Significant tumor volume reduction was observed in mice exposed to the siRNA signal compared to control mice;no adverse events were recorded. Cell blood counts (CBC) and protein expression patterns were observed to correlate with the expected function of protein expression inhibition of the targets.

Role of MRI in Differentiation between Postoperative Tumoral Recurrence and Radiation-Induced Brain Necrosis in Patients of Glioblastoma Multiform

The distinction of radiation-induced brain necrosis (RBN) and recurrent glioblastoma multiform (rGBM) remains a diagnostic challenge due to their similarly on routine follow-up imaging studies and also their clinical manifestations. Our purpose of this review article is to evaluate the role of advanced MR imaging techniques such as Perfusion-weighted imaging (PWI), Diffusion-weighted imaging (DWI) and Magnetic resonance spectroscopy (MRS) in the differentiation of RBN and rGBM and their complications together with our experience and knowledge gained during our neuroimaging practice.

Emerging targets for glioblastoma stem cell therapy

Glioblastoma multiforme（GBM）,designated as World Health Organization（WHO）grade IV astrocytoma,is a lethal and therapy-resistant brain cancer comprised of several tumor cell subpopulations,including GBM stem cells（GSCs）which are believed to contribute to tumor recurrence following initial response to therapies.Emerging evidence demonstrates that GBM tumors are initiated from GSCs.The development and use of novel therapies including small molecule inhibitors of specific proteins in signaling pathways that regulate sternness,proliferation and migration of GSCs,immunotherapy,and non-coding microRNAs may provide better means of treating GBM.Identification and characterization of GSC-specific signaling pathways would be necessary to identify specific therapeutic targets which may lead to the development of more efficient therapies selectively targeting GSCs.Several signaling pathways including mTOR,AKT,maternal embryonic leucine zipper kinase（MELK）,NOTCH1 and Wnt/β-catenin as well as expression of cancer stem cell markers CD133,CD44,Oct4,Sox2,Nanog,and ALDHlA1 maintain GSC properties.Moreover,the data published in the Cancer Genome Atlas（TCGA）specifically demonstrated the activated PI3K/AKT/mTOR pathway in GBM tumorigenesis.Studying such pathways may help to understand GSC biology and lead to the development of potential therapeutic interventions to render them more sensitive to chemotherapy and radiation therapy.Furthemore,recent demonstration of dedifferentiation of GBM cell lines into CSC-like cells prove that any successful therapeutic agent or combination of drugs for GBM therapy must eliminate not only GSCs,but the differentiated GBM cells and the entire bulk of tumor cells.

Decoupling of DNA damage response signaling from DNA damages underlies temozolomide resistance in glioblastoma cells

Glioblastoma multiforme （GBM） is the most aggressive primary brain tumor in adults.Current therapy includes surgery,radiation and chemotherapy with temozolomide （TMZ）.Major determinants of clinical response to TMZ include methylation status of the O6-methylguanine-DNA methyltransferase （MGMT） promoter and mismatch repair （MMR） status.Though the MGMT promoter is methylated in 45% of cases,for the first nine months of follow-up,TMZ does not change survival outcome.Furthermore,MMR deficiency makes little contribution to clinical resistance,suggesting that there exist unrecognized mechanisms of resistance.We generated paired GBM cell lines whose resistance was attributed to neither MGMT nor MMR.We show that,responding to TMZ,these cells exhibit a decoupling of DNA damage response （DDR） from ongoing DNA damages.They display methylation-resistant synthesis in which ongoing DNA synthesis is not inhibited.They are also defective in the activation of the S and G2 phase checkpoint.DDR proteins ATM,Chk2,MDC1,NBS1 and gammaH2AX also fail to form discrete foci.These results demonstrate that failure of DDR may play an active role in chemoresistance to TMZ.DNA damages by TMZ are repaired by MMR proteins in a futile,reiterative process,which activates DDR signaling network that ultimately leads to the onset of cell death.GBM cells may survive genetic insults in the absence of DDR.We anticipate that our findings will lead to more studies that seek to further define the role of DDR in ultimately determining the fate of a tumor cell in response to TMZ and other DNA methylators.

EXPRESSION OF IMMUNE-RELATED MOLECULES IN GLIOBLASTOMA MULTIFORM CELLS

Objective: To investigate the expression of immune- related molecules in glioblastoma multiform(GBM) cells. Methods: The expression of major histocompatibility complex (MHC), b2-microglobulin, Fas, CD80 and CD86 molecules on the surface of GBM cells were evaluated by flow cytometry. The expression of TAP-1, TAP-2 and Tapasin in the GBM cells were evaluated by RT-PCR method. Results: MHC class I, b2 microglobulin, TAP-1, TAP-2 and tapasin were expressed in most GBM cell lines. Except U87, there was no MHC class II molecule expression on any of the other GBM cell lines. Fas was expressed on all the GBM cell lines examined. Conclusion: The mechanism by which GBM escapes immune surveillance may involve down regulation of expression of MHC class I molecules and MHC class II molecules. MHC class I positive GBM may be the suitable target of immunotherapy.