Applied Fence-Post Techniques Using Deep Electrodes Instead of Catheters for Resection of Glioma Complicated with Frequent Epileptic Seizures: A Case Report

Fence-post catheter techniques are used to use tumor margins when resecting gliomas. In the present study, deep electrodes instead of catheters were used as fence-posts. The case of a 25-year-old female patient whose magnetic resonance images (MRI) revealed a tumor in the left cingulate gyrus is presented in this study. She underwent daily seizures without loss of consciousness under the administration of anti-seizure medications. Despite video electroencephalography (EEG) monitoring, the scalp inter-ictal EEG did not show obvious epileptiform discharges. We were consequently uncertain whether such frequent seizures were epileptic seizures or not. As a result, deep electrodes were used as fence-posts: three deep electrodes were inserted into the tumor’s anterior, lateral, and posterior margins using a navigation-guided method. The highest epileptic discharge was detected from the anterior deep electrode. As a result, ahead of the tumor was extendedly resected, and epileptic discharges were eliminated using EEG. The postoperative MRI revealed that the tumor was resected. The patient has never experienced seizures after the surgery. In conclusion, when supratentorial gliomas complicated by frequent seizures are resected, intraoperative EEG monitoring using deep electrodes as fence-posts is useful for estimating epileptogenic areas.

Carotid Plaque Diagnosis With 3-Dimensional Computed Tomography Angiography: A Comparison With Magnetic Resonance Imaging-Based Plaque Diagnosis

OBJECTIVE

Although a qualitative diagnosis of plaque causing carotid stenosis has been attempted with carotid computed tomography angiography (CaCTA), no clear findings have been reported. We examined the correlation between the plaque CT values and plaque images obtained by magnetic resonance imaging to derive a qualitative diagnosis of the plaque using CaCTA.

METHODS

Preoperative CaCTA images acquired from patients stented for carotid stenosis were retrospectively analyzed with respect to magnetization-prepared rapid acquisition with gradient echo and time-of-flight magnetic resonance angiography data. Carotid plaques in the stenosed region were quantified in terms of CT density and the plaque/muscle ratio (magnetization-prepared rapid acquisition with gradient echo), and correlations between these 2 features were determined. Plaques were classified as stable or unstable based on the plaque/muscle ratio, with the smallest plaque/muscle ratio observed among plaques positive for intraplaque hemorrhage set as the cutoff value (1.76).

RESULTS

A total of 165 patients (179 plaques) were included. Perioperative complications included minor stroke (n = 3), major stroke (n = 1, fatal), and hyperperfusion (n = 2). The correlation between CT density and the plaque/muscle ratio was nonlinear (P = 0.0139) and negative (P < 0.0001). The cutoff point (1.76) corresponded to a CT density of 83 HU, supporting this value as a standard reference for plaque stability.

CONCLUSIONS

Computed tomography density exhibits a nonlinear (P = 0.0139) and highly negative correlation (P < 0.0001) with the plaque/muscle ratio. Our results demonstrate that plaque characteristics can be meaningfully diagnosed based on CaCTA image data.

Three-Dimensional Amide Proton Transfer-Weighted Imaging for Differentiating between Glioblastoma, IDH-Wildtype and Primary Central Nervous System Lymphoma

Distinguishing primary central nervous system lymphoma (PCNSL) from glioblastoma, isocitrate dehydrogenase (IDH)-wildtype is sometimes hard. Because the role of operation on them varies, accurate preoperative diagnosis is crucial. In this study, we evaluated whether a specific kind of chemical exchange saturation transfer imaging, i.e., amide proton transfer-weighted (APTw) imaging, was useful to distinguish PCNSL from glioblastoma, IDH-wildtype. A total of 14 PCNSL and 27 glioblastoma, IDH-wildtype cases were evaluated. There was no significant difference in the mean APTw signal values between the two groups. However, the percentile values from the 1st percentile to the 20th percentile APTw signals and the width_1-100 APTw signals significantly differed. The highest area under the curve was 0.796, which was obtained from the width_1-100 APTw signal values. The sensitivity and specificity values were 64.3% and 88.9%, respectively. APTw imaging was useful to distinguish PCNSL from glioblastoma, IDH-wildtype. To avoid unnecessary aggressive surgical resection, APTw imaging is recommended for cases in which PCNSL is one of the differential diagnoses.

CBMS-1 TARGETING GLUTAMINE METABOLISM IN IDH-MUTANT GLIOMAS

IDH-wildtype and IDH-mutant glioma have different genetical and metabolic background although their histological appearances are similar. To reveal the difference in metabolites between IDH-wildtype and IDH-mutant glioma, two artificial cell lines made from normal human astrocyte, NHAE6E7hTERTRas (IDH-wildtype) and NHAE6E7hTERTIDHmut (IDH-mutant), were investigated. Capillary electrophoresis- and ion chromatography-coupled mass spectrometry revealed the lower amount of glutamine, glutamate and 2-oxoglutarate in NHAE6E7hTERTIDHmut cells than NHAE6E7hTERTRas cells. Pharmacological or genetical inhibition of GLUD1 which converts glutamate to 2-oxoglutarate, suppressed proliferation of the cells by inducing ROS and apoptosis in NHAE6E7hTERTIDHmut cells. ROS inhibitor, NAC suppressed GLUD1 inhibitor-induced ROS, apoptosis, and cytotoxicity in NHAE6E7hTERTIDHmut cells, revealing that cytotoxicity by GLUD1 inhibitor was at least partially due to the inhibitor-induced ROS. Exogeneous dimethyl 2-oxoglutarate rescued the cytotoxicity by GLUD1 inhibitor, suggesting decreased 2-oxoglutarate was associated with GLUD1 inhibitor-induced cytotoxicity. Mutant IDH1 overexpressed glioma cell line showed similar sensitivity to GLUD1 inhibitor to NHAE6E7hTERTIDHmut, which suggested that the difference of sensitivity to GLUD1 inhibitor was due to the status of mutant IDH. In conclusion, GLUD1 inhibitor will be new therapeutic options for IDH-mutant glioma.

LW-8 TREATMENT STRATEGY FOR OLIGODENDROGLIOMAS WITH NEOADJUVANT STRATEGY AND STAGED RESECTION UTILIZING THEIR CHEMOTHERAPEUTIC RESPONSIVENESS

Background

In glioma surgery, both of functional preservation and maximal safe resection are critical, however, neoadjuvant strategy has never been used because of difficulty of tissue sampling without craniotomy.

Method

In Keio University Hospital, oligodendrogliomas, i.e., diffuse gliomas with IDH mutation and 1p/19q codeletion, with incomplete initial resection have been treated by upfront chemotherapy and subsequent resection after tumor volume decrease (second look resection, SLR) since 2006 (J Neurooncol 124:127-35, 2015). At first, initial radiotherapy was prescribed immediately after chemotherapy or SLR only for the cases with aggressive clinical course or subarachnoid infiltration, however, cases with residual FLAIR abnormality after upfront chemotherapy or SLR were also subjected to initial radiotherapy since 2018. Cases 1) with IDH mutation and 1p/19q codeletion, and 2) without history of either chemotherapy or radiotherapy, and 3) treated with upfront chemotherapy and subsequent resection strategy, were included.

Results

Thirty nine cases of oligodendroglioma have been treated with the above strategy since 2006. Tumor volume decrease following upfront chemotherapy was 30-35% (median), and 19 tumors underwent SLR. Among the total 39 cases, PFS and OS after initiation of upfront chemotherapy were 81 months and not reached, respectively, and were 64 months and not reached, respectively, among the 32 cases with deferred radiotherapy. Importantly, the majority of tumor recurrence occurred at the residual FLAIR abnormality following upfront chemotherapy.

Conclusions

Treatment of oligodendrogliomas utilizing neoadjuvant strategy enables 1) decrease of resection volume as compared with initial maximal safe resection, 2) more precise resection, 3) confirmation of the necessity of initial radiotherapy based on the observed efficacy of chemotherapy. Moreover, the study also suggested that 4) invasion front of oligodendroglioma likely withdraw by alkylating agents, and 5) cases with residual FLAIR abnormality following chemotherapy may be appropriate subjects for initial radiotherapy.

Intracranial phosphaturic mesenchymal tumors. A case report and review of literature

Most osteomalacia-inducing tumors (OITs) are phosphaturic mesenchymal tumors (PMTs) that secrete fibroblast growth factor 23 (FGF23). These tumors usually occur in the bone and soft tissues, and intracranial OITs are rare. Therefore, intracranial OIT is difficult to diagnose and treat. This paper presents a case of intracranial OIT and shows a review of previous cases. A 45-year-old man underwent nasal cavity biopsy and treatment with active vitamin D₃ and neutral phosphate for hypophosphatemia. Amplification of FGF23 mRNA level within the tumor was detected. Subsequently, the surgical specimen was diagnosed with a PMT and was considered the cause of the patient's osteomalacia. The patient was referred to a neurosurgery department for the excision of the intracranial tumor extending to the nasal cavity. After tumor removal, the serum levels of FGF23 and phosphorus were normalized as compared to preoperative those. The patient remains disease-free, without additional treatment, approximately 10 years after surgery, with no tumor recurrence. As per the literature, intracranial OITs usually occur in patients aged 8-69 years. Bone and muscle pain are major complaints. Approximately 60% of the patients reported previously had symptoms because of intracranial tumors. In some cases, it took several years to diagnose OIT after the onset of the osteomalacia symptoms. Laboratory data in such cases show hypophosphatemia and elevated FGF23 levels. Because FGF23 levels are associated with the severity of osteomalacia symptoms, total tumor resection is recommended. PMT and hemangiopericytoma (HPC) are histologically similar, but on immunochemistry, PMT is negative for signal transducer and activator of transcription 6 (STAT6), whereas HPC is positive. FGF23 amplification is seen in PMTs but not in HPCs. Therefore, the analysis of FGF23 and STAT6 was helpful in distinguishing PMTs from HPCs. In cases of hypophosphatemia and osteomalacia without a history of metabolic, renal, or malabsorptive diseases, the possibility of oncogenic osteomalacia should be considered.

Hydrocephalus in Neurofibromatosis Type 1 Caused by a Cyst Formation Similar to Late-Onset Aqueductal Membranous Occlusion: A Case Report and Review of Literature

Cyst formation in the third ventricle and the histopathological findings were rarely reported. We report a similar case of late-onset aqueductal membranous occlusion (LAMO) caused by a thin gliotic cyst and a review of related literature. A 28-year-old woman with enlarged lateral ventricles was referred to our hospital with complaints of headache and dizziness. In our hospital, the obvious cause of the hydrocephalus was unknown on any examination and we decided performing endoscopic third ventriculostomy for hydrocephalus. A thin cyst covering the entrance of the aqueduct was identified and we perforated it. Histopathological finding of the cyst wall was gliosis and our case was similar to LAMO, although not typical. The postoperative symptoms and ventricle size improved for 4 years. When suspecting cases similar to definition of LAMO, neuroendoscopic surgery would be the first-choice treatment and might detect causes undetectable on preoperative imaging such as our thin membrane.

PKM2 Interacts With the Cdk1-CyclinB Complex to Facilitate Cell Cycle Progression in Gliomas

PKM2 is a phosphotyrosine-binding glycolytic enzyme upregulated in many cancers, including glioma, and contributes to tumor growth by regulating cell cycle progression. We noted, however, that in multiple glioma cell lines, PKM2 knock-down resulted in an accumulation of cells in G2-M phase. Moreover, PKM2 knock-down decreased Cdk1 activity while introducing a constitutively active Cdk1 reversed the effects of PKM2 knock-down on cell cycle progression. The means by which PKM2 increases Cdk1 activity have not been described. Transient interaction of T14/Y15-phosphorylated Cdk1 with cyclin B allows Cdk7-mediated pT161 Cdk1 phosphorylation followed by cdc25C-mediated removal of pT14/Y15 and activation of Cdk1 in cycling cells. In the present course of investigation, PKM2 modulation did not influence Cdk7 activity, but phosphotyrosine binding forms of PKM2 co-immunoprecipitated with pY15-containing Cdk1-cyclinB and enhanced formation of active pT161 Cdk1-cyclin B complexes. Moreover, exogenous expression of phosphotyrosine binding forms of PKM2 reversed the effects of PKM2 knock-down on G2-M arrest. We here show that PKM2 binds and stabilize otherwise transient pY15-containing Cdk1-cyclinB complexes that in turn facilitate Cdk1-cyclin B activation and entry of cells into mitosis. These results, therefore, establish metabolic enzyme PKM2 as a direct interactor and activator of Cdk1-cyclin B complex and thereby directly controls mitotic progression and the growth of brain tumor cells.

Transsylvian and trans-Heschl’s gyrus approach for a left posterior insular lesion and functional analyses of the left Heschl’s gyrus: illustrative case

BACKGROUND

A common surgical approach for dominant insular lesions is to make a surgical corridor in asymptomatic cortices based on functional mapping. However, the surgical approach is difficult for posterior insular lesions in a dominant hemisphere because the posterior parts of the perisylvian cortices usually have verbal functions.

OBSERVATIONS

We present the case of a 40-year-old male whose magnetic resonance images revealed the presence of contrast-enhancing lesions in the left posterior insula. Our surgical approach was to split the sylvian fissure as widely as possible, and partially resect Heschl’s gyrus if the cortical mapping was negative for language tests. Because Heschl’s gyrus did not have verbal functions, the gyrus was used as a surgical corridor. It was wide enough for the removal of the lesion; however, because intraoperative pathological diagnosis eliminated the possibility of brain tumors, further resection was discontinued. The tissues were histologically diagnosed as tuberculomas. Antituberculosis drugs were administered, and the residual lesions finally disappeared. According to the neurophysiological tests, the patient showed temporary impairment of auditory detection, but the low scores of these tests improved.

LESSONS

The transsylvian and trans-Heschl’s gyrus approach can be a novel surgical option for excising dominant posterior insular lesions.

CBMS-1 Targeting amino acid metabolic vulnerabilities in IDH-mutant and IDH-wildtype gliomas

IDH-wildtype glioma and IDH-mutant glioma have different genetical and metabolic background although their histological appearances are similar. To reveal the difference in metabolites between IDH-wildtype and IDH-mutant glioma, and to find the effective treatment targeting cancer metabolism according to the status of IDH in gliomas, two artificial cell lines made from normal human astrocyte, NHAE6E7hTERTRas (IDH-wildtype) and NHAE6E7hTERTIDHmut (IDH-mutant), were investigated. RNA-seq analysis revealed that about 10% of changed genes were involved with metabolism. Capillary electrophoresis- and ion chromatography-coupled mass spectrometry revealed that the amount of asparagine was lower in NHAE6E7hTERTRas cells compared with NHAE6E7hTERTIDHmut cells. L-asparaginase, which converts asparagine into aspartate, was more effective in former cells. L-asparaginase induced autophagy and inhibition of autophagy by 3-MA suppressed L-asparaginase-induced antitumor effect. Adding asparagine into the culture medium rescued the antitumor effect of L-asparaginase. L-asparaginase increased the expression of asparagine synthetase (ASNS) and inhibition of ASNS enhanced the antitumor effect of L-asparaginase. Metabolic assay also showed the lower amount of glutamine, glutamate and 2-oxoglutarate in NHAE6E7hTERTIDHmut cells than NHAE6E7hTERTRas cells. Inhibition of GLUD1 which converts glutamate to 2-oxoglutarate, suppressed proliferation of the cells by inducing ROS and apoptosis in NHAE6E7hTERTIDHmut cells. Exogeneous dimethyl 2-oxoglutarate rescued the cytotoxicity by GLUD1 inhibitor, suggesting decreased 2-oxoglutarate was associated with GLUD1 inhibitor-induced cytotoxicity. ROS inhibitor, NAC suppressed GLUD1 inhibitor-induced ROS, apoptosis, and cytotoxicity in NHAE6E7hTERTIDHmut cells, revealing that cytotoxicity by GLUD1 inhibitor was at least partially due to the inhibitor-induced ROS. Other IDH-wildtype glioma cells, U251 and U87 showed similar sensitivity to L-asparaginase and GLUD1 inhibitor to NHAE6E7hTERTRas, whereas U251 expressing mutant IDH1 showed similar sensitivity to GLUD1 inhibitor to NHAE6E7hTERTIDHmut, which suggested that the difference of sensitivity to each reagent was due to the status of mutant IDH. L-asparaginase and GLUD1 inhibitor will be new therapeutic options for IDH-wildtype glioma and IDH-mutant glioma, respectively.

Contrast-Enhanced Magnetic Resonance Imaging, Perfusion Magnetic Resonance Imaging, and 1H-Magnetic Resonance Spectroscopy Distinguish Primary Central Nervous System Vasculitis from Glioblastoma

BACKGROUND

We investigated the ability of magnetic resonance imaging (MRI) to distinguish primary central nervous system vasculitis (PCNSV) from glioblastoma to facilitate the development of an appropriate treatment for PCNSV.

METHODS

We enrolled patients who were treated for PCNSV or glioblastoma at our center between January 2007 and August 2018. We compared the diagnoses of the 2 conditions by retrospectively reviewing patients' data for contrast-enhanced MRI, perfusion MRI, flow-sensitive black-blood (FSBB) imaging, and ¹H-magnetic resonance spectroscopy (MRS).

RESULTS

We evaluated 108 patients (6 PCNSV; 102 glioblastoma). We found a statistically significant correlation between diagnosis and the contrast pattern on MRI. Perivascular enhancement was observed in all cases of PCNSV as follows: ring-like, homogeneous, and irregular patterns were observed in 53 (60%), 18 (20%), and 17 (19%) cases of glioblastoma, respectively. We identified a statistically significant correlation between diagnosis and cerebral blood volume (CBV) in 3 patients with PCNSV who underwent perfusion MRI; and all had low CBVs. Among the 55 patients with glioblastoma who underwent perfusion MRI, low and high CBVs were detected in 3 and 52 patients, respectively. There was no significant correlation between diagnosis and FSBB findings. Evaluation of ¹H-MRS data showed statistically significant differences between PCNSV and glioblastoma as functions of neuronal amino acid levels on long echo time MRS, with a slightly different amino acid profile, including glutamine + glutamate on short echo time MRS.

CONCLUSIONS

Contrast-enhanced MRI, perfusion MRI, and quantitative analysis of ¹H-MRS are valuable techniques for distinguishing PCNSV from glioblastoma before surgery.

TAMI-56. TARGETING AMINO ACID METABOLIC VULNERABILITIES IN IDH-MUTANT AND IDH-WILDTYPE GLIOMAS

IDH-wildtype glioma and IDH-mutant glioma have different genetical and metabolic background although their histological appearances are similar. The aim of the study is to reveal the difference in metabolites between IDH-wildtype glioma and IDH-mutant glioma, and to find the effective treatment targeting cancer metabolism according to the status of IDH in gliomas. Two artificial cell lines made from normal human astrocyte were used: NHAE6E7hTERTRas (IDH-wildtype) and NHAE6E7hTERTIDHmut (IDH-mutant). Capillary electrophoresis time-of-flight-mass spectrometry (CE-TOFMS) revealed that the amount of asparagine was lower in NHAE6E7hTERTRas cells compared with NHAE6E7hTERTIDHmut cells. L-asparaginase, which converts asparagine into aspartate, was more effective in the former cells than the latter cells. L-asparaginase induced autophagy and inhibition of autophagy by 3-MA suppressed L-asparaginase-induced antitumor effect. Adding asparagine into the culture medium rescued the antitumor effect of L-asparaginase. L-asparaginase increased the expression of asparagine synthetase (ASNS) and genetical or pharmacological inhibition of ASNS enhanced the antitumor effect of L-asparaginase. CE-TOFMS showed the lower amount of glutamine, glutamate and 2-oxoglutarate in NHAE6E7hTERTIDHmut cells than NHAE6E7hTERTRas cells. GLUD1 inhibitor inhibited proliferation by inducing higher ROS level and apoptosis in NHAE6E7hTERTIDHmut cells than NHAE6E7hTERTRas cells. ROS inhibitor, NAC suppressed GLUD1 inhibitor-induced ROS, apoptosis, and cytotoxicity in NHAE6E7hTERTIDHmut cells. Exogeneous dimethyl 2-oxoglutarate rescued the cytotoxicity induced by GLUD1 inhibitor. L-asparaginase and GLUD1 inhibitor will be new therapeutic option for IDH-wildtype glioma and IDH-mutant glioma, respectively.

Primary central nervous system lymphomas with massive intratumoral hemorrhage: Clinical, radiological, pathological, and molecular features of six cases

Primary central nervous system lymphomas (PCNSLs) rarely exhibit intratumoral hemorrhage. The differential diagnosis of hemorrhagic neoplasms of the central nervous system (CNS) currently includes metastatic carcinomas, melanomas, choriocarcinomas, oligodendrogliomas, and glioblastomas. Here we present the clinical, radiological, pathological, and molecular genetic features of six cases of PCNSL associated with intratumoral hemorrhage. The median age of patients was 75 years, with male predominance. While conventional PCNSLs were associated with low cerebral blood volume (CBV), perfusion magnetic resonance imaging (MRI) revealed elevated CBV in three cases, consistent with vascular proliferation. All six cases were diagnosed pathologically as having diffuse large B-cell lymphoma (DLBCL) with a non-germinal center B-cell-like (non-GCB) phenotype; marked histiocytic infiltrates and abundant non-neoplastic T-cells were observed in most cases. Expression of vascular endothelial growth factor and CD105 in the lymphoma cells and the small vessels, respectively, suggested angiogenesis within the neoplasms. Neoplastic cells were immunohistochemically negative for programmed cell death ligand 1 (PD-L1), while immune cells in the microenvironment were positive for PD-L1. Mutations in the MYD88 gene (MYD88) (L265P) and the CD79B gene (CD79B) were detected in five and one case, respectively. As therapeutic modalities used for PCNSLs differ from those that target conventional hemorrhagic neoplasms, full tissue diagnoses of all hemorrhagic CNS tumors are clearly warranted.

Superficial Siderosis of the Central Nervous System Caused by Glioneuronal Tumor: A Case Report and Literature Review

Superficial siderosis is a rare disease resulting from the deposited hemosiderin owing to repeated subarachnoid hemorrhage. It has been reported that hemosiderin deposits on the brain surface and brain parenchyma causes nerve disorder, resulting in progressive and irreversible hearing loss, cerebellar ataxia and pyramidal disorder. The brain tumor is one of the cause of superficial siderosis. A 16-year-old female present a nearby hospital with complaints of absence seizure. A magnetic resonance imaging (MRI) revealed a heterogeneously enhanced mass at the right temporal lobe. Susceptibility-weighted imaging revealed diffuse and extensive superficial siderosis on the brain surface. The tumor was gross totally removed and diagnosed as glioneuronal tumor. The patient had been well, although susceptibility-weighted imaging performed one year after the surgery showed superficial siderosis remained. Early diagnosis and prevention of bleeding sources are recommended to prevent symptom progression associated with superficial siderosis. Susceptibility-weighted imaging is considered useful for early detection of superficial siderosis.

[Genomic and Epigenomic Abnormalities in Gliomas]

Advances in genetic and epigenetic analyses and immunohistochemical studies involving the development of mutation-specific or histone-methylated antibodies have provided many significant findings about gliomas. Based on these findings, the WHO developed and published the classification of tumors of the central nervous system in 2016. In the classification system, molecular information was combined with pathological findings. After its publication, the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy-Not Official WHO(cIMAPCT-NOW)was published to evaluate and recommend changes to future central nervous system tumor classifications. This review describes the genetic and epigenetic features of gliomas, mainly those associated with the WHO classification and cIMPACT-NOW.

Myoinositol to Total Choline Ratio in Glioblastomas as a Potential Prognostic Factor in Preoperative Magnetic Resonance Spectroscopy

Isocitrate dehydrogenase (IDH) wild-type diffuse astrocytic tumors tend to be pathologically diagnosed as glioblastomas (GBMs). We previously reported that myoinositol to total choline (Ins/Cho) ratio in GBMs on magnetic resonance (MR) spectroscopy was significantly lower than that in IDH-mutant gliomas. We then hypothesized that a low Ins/Cho ratio is a poor prognosis factor in patients with GBMs, IDH-wild-type. In the present study, we calculated the Ins/Cho ratios of patients with GBMs and investigated their progression-free survival (PFS) and overall survival (OS) to determine their utility as prognostic marker. We classified patients with GBMs harboring wild-type IDH (n = 27) into two groups based on the Ins/Cho ratio, and compared patient backgrounds, pathological findings, PFS, OS, and copy number aberrations between the high and low Ins/Cho groups. Patients with GBMs in the low Ins/Cho ratio group indicated shorter PFS (P = 0.021) and OS (P = 0.048) than those in the high Ins/Cho group. Multivariate analysis demonstrated that the Ins/Cho ratio was significantly correlated with PFS (hazard ratio 0.24, P = 0.028). In conclusion, the preoperative Ins/Cho ratio can be used as a novel potential prognostic factor for GBM, IDH-wild-type.

RETRACTED: A subset of PARP inhibitors induces lethal telomere fusion in ALT-dependent tumor cells

About 10% of all tumors, including most lower-grade astrocytoma, rely on the alternative lengthening of telomere (ALT) mechanism to resolve telomeric shortening and avoid limitations on their growth. Here, we found that dependence on the ALT mechanism made cells hypersensitive to a subset of poly(ADP-ribose) polymerase inhibitors (PARPi). We found that this hypersensitivity was not associated with PARPi-created genomic DNA damage as in most PARPi-sensitive populations but rather with PARPi-induced telomere fusion. Mechanistically, we determined that PARP1 was recruited to the telomeres of ALT-dependent cells as part of a DNA damage response. By recruiting MRE11 and BRCC3 to stabilize TRF2 at the ends of telomeres, PARP1 blocked chromosomal fusion. Exposure of ALT-dependent tumor cells to a subset of PARPi induced a conformational change in PARP1 that limited binding to MRE11 and BRCC3 and delayed release of the TRF2-mediated block on lethal telomeric fusion. These results therefore provide a basis for PARPi treatment of ALT-dependent tumors, as well as establish chromosome fusion as a biomarker of their activity.

Association of preoperative seizures with tumor metabolites quantified by magnetic resonance spectroscopy in gliomas

Seizures are common in patients with gliomas; however, the mechanisms of epileptogenesis in gliomas have not been fully understood. This study hypothesized that analyzing quantified metabolites using magnetic resonance spectroscopy (MRS) might provide novel insights to better understand the epileptogenesis in gliomas, and specific metabolites might be indicators of preoperative seizures in gliomas. We retrospectively investigated patient information (gender, age at diagnosis of tumor, their survival time) and tumor information (location, histology, genetic features, and metabolites according to MRS) in patients with gliomas. The data were correlated with the incidence of seizure and analyzed statistically. Of 146 adult supratentorial gliomas, isocitrate dehydrogenase (IDH) mutant tumors significantly indicated higher incidence of preoperative seizures than IDH wild-type gliomas. However, MRS study indicated that glutamate concentration in IDH wild-type gliomas was higher than that in IDH mutant gliomas. Glutamate was not associated with high frequency of preoperative seizures in patients with gliomas. Instead, increased total N-acetyl-L-aspartate (tNAA) was significantly associated with them. Moreover, multivariable analysis indicated that increased level of tNAA was an independent predictor of preoperative seizures. According to MRS analysis, tNAA, rather than glutamate, might be a useful to detect preoperative seizures in patient with supratentorial gliomas.

DDRE-04. THE COMBINED TREATMENT OF L-ASPARAGINASE AND 6-DIAZO-5-OXO-L-NORLEUCINE INHIBIT THE PROLIFERATION OF TEMOZOLOMIDE-SENSITIVE OR RESISTANT GLIOBLASTOMA CELLS

Glioblastoma is one of the aggressive brain tumors with a 5-year survival rate of < 10%. The standard treatment is maximal safe resection, followed by radiation therapy and temozolomide (TMZ). Clinically, the resistance to TMZ is a big problem. Cancer cells have been revealed to show different metabolism from normal cells. The object of this study is to evaluate whether cancer metabolism, especially asparagine, could be a new target of treatment in primary and recurrent glioblastoma. Glioblastoma cells (U251 and U87) were treated with L-asparaginase and/or 6-diazo-5-oxo-L-norleucine (DON). L-asparaginase converts asparagine into aspartate and depletes asparagine. DON is a glutamine analog that inhibits several glutamine-utilizing enzymes, including asparagine synthetase. L-asparaginase or DON suppressed the proliferation of U251, and U87 cells in a dose-dependent manner. Combined treatment with these drugs had a synergistic antiproliferative effect in these cell lines. The effect was counteracted by exogenous asparagine. The combined treatment induced greater apoptosis and autophagy than did single-drug treatment. Several clones of TMZ-resistant U251 were obtained after long treatment of TMZ to U251. The expression of MSH6, one of the mismatch repair proteins, was suppressed in these resistant clones. The synergistic effect of L-asparaginase and DON was detected in these U251-derived TMZ-resistant clones. These results suggest that the combination of L-asparaginase and DON could be a new therapeutic option for patients with primary and recurrent glioblastoma.

The Correlation of Fluorescence of Protoporphyrinogen IX and Status of Isocitrate Dehydrogenase in Gliomas

BACKGROUND

The extent of resection has been reported to be associated with overall survival in gliomas. The use of 5-aminolevulinic acid (5-ALA) has been recognized to increase the extent of tumor resection.

OBJECTIVE

To evaluate what factors affect the intraoperative fluorescence after administration of 5-ALA in gliomas.

METHODS

Correlation of intraoperative fluorescence and several clinical, radiographic, molecular biologic, and histopathologic characters was retrospectively evaluated in 104 patients (53 males and 51 females; mean age 54.2 yr) with gliomas at our institution. To clarify the mechanisms that mutant isocitrate dehydrogenase (IDH) affect the intraoperative fluorescence, in Vitro experiments using genetically engineered glioma cells harboring mutant IDH1 were performed.

RESULTS

Intraoperative fluorescence was observed in 82 patients (78.8%). In addition to age, magnetic resonance imaging enhancement, World Health Organization grades, and MIB-1 index, the status of IDH was revealed to be correlated with intraoperative fluorescence. In Vitro assay revealed that mutant IDH indirectly reduced the amount of exogenous 5-ALA-derived protoporphyrinogen IX in glioma cells by increasing activity of ferrochelatase and heme oxygenase 1.

CONCLUSION

Mutant IDH1/2-induced metabolite changes of exogenous 5-ALA were suggested to contribute to the lesser intraoperative fluorescence in gliomas with mutant IDH1/2 than in those without.

MODL-15. THE COMBINATION TREATMENT OF PARP INHIBITOR AND TMZ, OR DAG WILL BE PROMISING TREATMENT IN SF8628

Diffuse midline glioma, H3 K27M-mutant (DMG) is a newly defined entity. The prognosis of DMG is poor. Because surgical resection is often incomplete for DMG, radiotherapy and chemotherapy are important. Temozolomide (TMZ) is an alkylating agent that adds a methyl group to DNA (O6-guanine, N7-guanine, and N3-adenine). TMZ-induced cytotoxicity is mainly derived from O6-methylguanine, which is repaired by O6-methylguanine DNA methyltransferase (MGMT). It has been reported that most of DMG lacked MGMT promoter hypermethylation, which is thought to contribute to less effectiveness of TMZ to DMG. The purpose of the study is to explore the way to inhibit the proliferation of DMG. A DMG cell line, SF8628, was used for the experiments. SF8628 had the expression of MGMT and was revealed to be resistant to TMZ. Because N7-methylguanine and N3-methyladenine are repaired via base excision repair, poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitor combined with TMZ was considered to be effective to suppress the proliferation of SF8628. As expected, PARP inhibitor enhanced TMZ-induced cytotoxicity in SF8628. Dianhydrogalactiol (DAG) is a bifunctional DNA-targeting agent forming N7-alkylguanine and inter-strand DNA crosslinks. DAG reduced the clonogenicity of SF8628. Moreover, inhibition of homologous recombination enhanced the DAG-induced cytotoxicity in SF8629. The combination treatment of PARP inhibitor and TMZ, or DAG were revealed to be promising treatments in SF8628.

ML-23 The outcome of malignant lymphoma of the central nervous system in a single institution

Background: Although high dose-methotrexate therapy has been performed for primary central nervous system malignant lymphoma (PCNSL), R-MPV (rituximab, methotrexate (MTX), procarbazine and vincristine) therapy is currently the first line therapy for (PCNSL) in our hospital. This study examines the results of R-MPV therapy comparing with past treatment. Method/Subjects: Thirty-seven patients treated at our hospital from 2009 to 2020 were included. Overall survival time, progression free survival time, and toxicities were evaluated. Results: The average age of patients was 65.7 years. Patients included 21 males and 16 females. Thirty-six patients were diagnosed DLBCL by resected brain tumor tissues, and one was diagnosed DLBCL by vitreous biopsy. As initial treatment, rituximab±HD-MTX therapy (R±MTX group) was performed in 20 cases, HD-MTX therapy plus radiation (R±MTX+RT group) was performed in 12 cases, and RMPV therapy was performed in 5 cases (R-MPV group). Median OS of all cases was 69 months and median PFS was 38 months. Median OS was 69 months in R±MTX group and could not be calculated in R±MTX+RT, and R-MPV groups. Median PFS was 16 months and 56 months in R±MTX group and R±MTX+RT, respectively, and could not be calculated in the R-MPV group. Although the R-MPV group had a short follow-up period, the results were considered to be comparable to those of the R±MTX+RT group. On the other hand, grade 3/4 adverse events occurred in 50%, 25%, and 100%, respectively. Conclusion: R-MPV therapy may delay the timing of radiation and reduce the amount of radiation. On the other hand, the frequency of adverse events is high, and more strict management of treatment is required.

CBMS-02 Phosphoglycerate mutase 1 (PGAM1) controls DNA damage repair via regulation of WIP1 activity

Phosphoglycerate Mutase 1 (PGAM1) is overexpressed in different forms of cancer and has been suggested to have additional functions beyond its role in metabolism. We here report that PGAM1 is overexpressed in GBMs and indirectly regulates activation of ATM, Chk1 and Chk2 but not ATR, thereby increasing the efficiency of DNA damage repair and resistance to radiation (IR) and temozolomide (TMZ) treatment. Genetic suppression of PGAM1 in multiple GBM cell lines resulted in decrease proliferation, apoptosis and colony formation after radiation and temozolomide treatment compared to parental cells. Moreover, parental cells demonstrated DNA damage (gH2AX foci) whereas isogenic PGAM1 knockdown cells exhibited no DNA damage repair activation and a significant increase in sub-G0 apoptotic cells that expressed annexin-V, cleaved caspase-3 and cleaved PARP-1. Mechanistically, suppression of PGAM1 expression inhibited phosphorylation of ATM at s1981 and the subsequent downstream phosphorylation of Chk2 and cdc25C. Moreover, PGAM1 co-immunoprecipitated with WIP1, a phosphatase reported to bind and dephosphorylate ATM, Chk1, and Chk2. Cytoplasmic binding of WIP1 with PGAM1 prevented nuclear localization of WIP1, leaving ATM and its downstream substrates phosphorylated, which is required for DNA damage repair activity. Consistent with these observations, mice intracranially implanted with PGAM1 knockdown GBM cells and treated with TMZ and IR had longer survival than similarly treated mice implanted with matched control cells. These results therefore define PGAM1 as an activator of DNA damage repair pathway and link tumor metabolism to drug response in GBM.

DDRE-15. THE COMBINATION THERAPY OF PARP INHIBITOR AND TMZ IN DIFFUSE MIDLINE GLIOMA HARBORING H3 K27M-MUTANT

Diffuse midline glioma harboring H3 K27M-mutant (DMG) is a newly defined entity, and the prognosis of DMG is very poor. Combined of radiotherapy and chemotherapy is a standard therapeutic approach, because surgical debulking for providing relief to patients is not an option. Temozolomide (TMZ) is often used for the treatment of gliomas. TMZ is an alkylating agent that adds a methyl group to DNA (O6-guanine, N7-guanine, and N3-adenine). TMZ-induced cytotoxicity is mainly derived from O6-methylguanine, which is repaired by O6-methylguanine DNA methyltransferase (MGMT). Unfortunately, most DMG lacks MGMT promoter hypermethylation, which contributes to less effectiveness of TMZ in DMG. Because N7-methylguanine and N3-methyladenine are repaired via base excision repair, poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitor combined with TMZ was considered to be effective to suppress the proliferation of DMG. The purpose of the study is to evaluate whether PARP inhibitor sensitizes DMG to TMZ. A patient-derived DMG cell line, SF8628, showed the expression of MGMT, resulted in resistant to TMZ. We evaluated the effects of multiple PARP inhibitors: talazoparib, olaparib, niraparib, A-966492 in SF8628 DMG cells. These PARP inhibitors suppressed the proliferation of SF8628 cells in a dose dependent manner. Moreover, PARP inhibitors enhanced TMZ-induced cytotoxicity in SF8628. The combined treatment of PARP inhibitor and TMZ induced apoptosis. These results would support a possibility that the combination treatment of PARP inhibitor and TMZ is an effective approach in DMG.

CSIG-19. THE DEUBIQUITINASE BRCC3 LINKS ALT TELOMERES TO SUPPRESSION OF INNATE IMMUNITY IN IDH1-MUTANT GLIOMA

Approximately 10% of tumors including all IDH1-mutant lower-grade glioma resolve telomeric shortening using Alternative Lengthening of Telomere (ALT) mechanism. Although the ALT process lengthens telomeres, it also generates small bits of extrachromosomal, telomere-containing DNA (ECTRs). These ECTRs can bind and activate cyclic GMP-AMP synthase (cGAS), the major cytosolic sensor of double-stranded DNA, which in turn can activate expression of stimulator of IFN genes (STING) and the interferon-based innate immune response. To limit the immune response, ALT cells inactivate the cGAS-STING pathway, although the mechanism by which this occurs is unknown. Here we show that the deubiquitinase BRCC3 links ALT telomeres to suppression of the cGAS-STING pathway and the innate immune response. Astrocytoma cells dependent on the ALT-mechanism (IDH1-mutant and ATRX-deficient genetically-modified human astrocytes and MGG119 PDX) contained ECTR and had reduced expression of the cGAS and the downstream components of the cGAS-STING pathway (STING, and IFN-β) relative to matched non-ALT (isogenic ATRX WT astrocytes and MGG152 PDX) cells lacking ECTRs. Decreased levels of cGAS in ALT cells were in turn associated with deubiquitiantion and destabilization of cGAS. The telomere-derived ECTR in ALT-dependent cells lacked two proteins normally found in ALT telomeres (TRF2 or PARP), but retained two other proteins, Mre11 and its binding partner, normally nuclear deubiquitinase BRCC3. Furthermore, either pharmacologic inhibition or genetic suppression of BRCC3 levels had no effect on ECTR levels but stabilized cGAS and activated the cGAS-STING pathway. This cGAS-mediated activation could be blocked by exogenous expression of WT BRCC3, but not by expression of a mutant BRCC3 incapable of deubiquitination. These results show that BRCC3 translocated along with ECTRs to the cytoplasm degrades cGAS and protects ALT-dependent cells from activating the innate immune response. The BRCC3-controlled cGAS-STING pathway may therefore represent a therapeutically targetable means to enhance the immune response in IDH1-mutant lower grade glioma.

Human Glioma Cells Acquire Temozolomide Resistance After Repeated Drug Exposure Via DNA Mismatch Repair Dysfunction

BACKGROUND/AIM

Temozolomide (TMZ) induces prolonged arrest of human glioma cells in the G₂/M phase and inhibition of the G₂ checkpoint intensifies the effect of TMZ. These findings suggest that the G₂ checkpoint is linked to DNA repair mechanisms.

MATERIALS AND METHODS

To clarify the mechanism of TMZ resistance, we established TMZ-resistant (TR) clones by serial treatment of U87MG cells with TMZ. We evaluated TMZ-induced cell cycle arrest and the effect of various G₂ checkpoint inhibitors.

RESULTS

We observed that longer exposure (over 6 months) to TMZ enriched the proportion of TR clones that underwent only minimal G₂ arrest following TMZ treatment compared to short exposure (4 months) to TMZ. Expression of MSH6 was reduced in these clones. None of the G₂ checkpoint inhibitors could resensitize TR clones to TMZ.

CONCLUSION

Longer drug treatment may induce resistance of cells to DNA damaging agent(s) by means of mismatch repair modification.

Phosphoglycerate Mutase 1 Activates DNA Damage Repair via Regulation of WIP1 Activity

The metabolic enzyme phosphoglycerate mutase 1 (PGAM1) is overexpressed in several types of cancer, suggesting an additional function beyond its established role in the glycolytic pathway. We here report that PGAM1 is overexpressed in gliomas where it increases the efficiency of the DNA damage response (DDR) pathway by cytoplasmic binding of WIP1 phosphatase, thereby preventing WIP1 nuclear translocation and subsequent dephosphorylation of the ATM signaling pathway. Silencing of PGAM1 expression in glioma cells consequently decreases formation of γ-H2AX foci, increases apoptosis, and decreases clonogenicity following irradiation (IR) and temozolomide (TMZ) treatment. Furthermore, mice intracranially implanted with PGAM1-knockdown cells have significantly improved survival after treatment with IR and TMZ. These effects are counteracted by exogenous expression of two kinase-dead PGAM1 mutants, H186R and Y92F, indicating an important non-enzymatic function of PGAM1. Our findings identify PGAM1 as a potential therapeutic target in gliomas.

SPDR-01 INHIBITION OF HOMOLOGOUS RECOMBINATION, PARP INHIBITOR, OR DIANHYDROGALACTITOL OVERCOMES TEMOZOLOMIDE-RESISTANCE IN GLIOMA CELLS

Glioblastoma is one of the most aggressive tumors, with 5-year survival rates of less than 10%. The standard therapy for glioblastomas is maximal safe resection, followed by radiation therapy and chemotherapy with temozolomide (TMZ). The poor prognosis is partially contributed to the acquisition of resistance to TMZ and intratumoral heterogeneity. The mechanisms of resistance to TMZ are various due to tumor heterogeneity. TMZ is a DNA-methylating agent, delivering a methyl group to DNA (O6-guanine, N7-guanine and N3-adenine). The primary cytotoxic lesion, O6-methylguanine, mispairs with thymine, leading to futile DNA mismatch repair (MMR), formation of double strand breaks (DSBs) and eventual cell death, when O6-methylguanine DNA methyltransferase (MGMT) is absent. N7-methylguanine and N3-methyladenine are repaired by base excision repair (BER). The object of the study was to reveal the mechanisms of resistance to TMZ and to find the way to overcome the resistance in glioma. Several clones of TMZ-resistant U251 or U87 were obtained and analyzed. Increased homologous recombination (HR) and deficiency of MMR system, not MGMT were revealed to be contributed to the resistance to TMZ. Inhibition of HR resensitized cells with high HR to TMZ, but it could not resensitize cells with deficient MMR. For the cells with deficient MMR, Inhibition of BER by PARP inhibitor was revealed to potentiate the TMZ-induced cytotoxicity. PARP inhibitors also potentiate the cytotoxicity of TMZ to cells with expressed MGMT. Dianhydrogalactitol (DAG) is a bifunctional DNA-targeting agent, forming N7 alkylguanine and inter-strand DNA crosslinks. DAG reduced the proliferation of cells independent of MGMT and MMR, inducing DNA DSBs, G2/M arrest, and apoptosis in TMZ-resistant glioma cells. Inhibition of chk1, or HR could enhance the cytotoxicity of DAG, increasing apoptosis cells. By selecting the appropriate treatments to the types of resistant mechanisms, these new treatments have the potential to improve the prognosis of glioblastoma.

DRES-03. PARP INHIBITOR, INHIBITION OF HOMOLOGOUS RECOMBINATION, OR DIANHYDRODULCITOL CAN OVERCOME TEMOZOLOMIDE-RESISTANCE IN GLIOMA CELLS

Glioblastoma is one of the most aggressive tumors in the central nervous system tumors, with 5-year survival rates of less than 10%. The standard therapy for glioblastomas is maximal safe resection, followed by radiation therapy and chemotherapy with temozolomide (TMZ). The acquisition of resistance to TMZ and the heterogeneity of the tumor are considered to be associated with poor prognosis. TMZ is a DNA-methylating agent, delivering a methyl group to DNA (O6-guanine, N7-guanine and N3-adenine). The primary cytotoxic lesion, O6-methylguanine, mispairs with thymine, leading to futile DNA mismatch repair (MMR), formation of double strand breaks and eventual cell death, when O6-methylguanine DNA methyltransferase (MGMT) is absent. N7-methylguanine and N3-methyladenine are repaired by base excision repair (BER). The object of the study was to reveal the mechanisms of resistance to TMZ and to find the way to overcome the resistance in glioma. Several clones of TMZ-resistant U251 were obtained and analyzed. A clone showed high homologous recombination (HR), and inhibition of HR resensitized the clone to TMZ. MMR system was suppressed in the other clones. Inhibition of BER by PARP inhibitor resensitized them to TMZ. PARP inhibitor enhanced the TMZ-induced cytotoxicity in glioma cells with high expression of MGMT. Dianhydrodulcitol, alkylating agent, suppressed the proliferation in U251 and even U251-derived resistant clones. These effects were shown in U87MG-dereived resistant clones and MGMT-proficient cell lines. Moreover, inhibition of HR enhanced the cytotoxicity of dianhydrodulcitol. To select the appropriate treatment according to the mechanisms of resistance to TMZ can overcome the resistance in glioma cells.

CBMT-19. THE ALTERNATIVE LENGTHENING OF TELOMERE (ALT) MECHANISM PROVIDES COLLATERAL SENSITIVITY TO LETHAL TELOMERIC FUSION INDUCED BY TRAPPING PARP INHIBITORS

A subset of human tumors, including all IDH1-mutant astrocytomas, use a homologous recombination-based alternative lengthening of telomere (ALT) pathway to resolve telomeric dysfunction in the absence of TERT. Because ALT is not used by normal cells, targeting of the process may provide new therapeutic options for patients with ALT-dependent tumors. We here report that reliance on the ALT mechanism makes tumors collaterally hypersensitive to clinically-available trapping PARPi (t-PARPi). Specifically we noted that astrocytoma cells dependent on the ALT-mechanism (IDH1-mutant and ATRX-deficient genetically-modified human astrocytes and MGG119 PDX) were significantly more sensitive to trapping PARPi than matched ALT-independent isogenic ATRXWT astrocytes and MGG152 PDX cells, respectively) both in vitro and in vivo. Surprisingly this hypersensitivity was not associated with BRCA-ness, the extent of PARP inhibition, or with t-PARPi-created genomic DNA damage as is the case in most PARPi-sensitive populations. Rather the enhanced activity of t-PARPi in ALT-dependent cells was associated with a novel t-PARPi-induced, lethal telomere fusion. Furthermore, the extent of chromosomal fusion was proportional to the PARP-trapping ability of the five PARP inhibitors tested, and could be prevented by exogenous expression of TERT, which eliminated reliance on ALT but did not alter levels of PARPi-induced genomic DNA damage. The extent of tPARPi-induced telomeric fusion in ALT-dependent cells, which could be directly measured in small amounts of DNA using a q-PCR approach, was also directly proportional to tPARPi-induced cell death in vitro and to prolonged survival of tumor-bearing mice in vivo. These results therefore identify clinically available tPARPi as a new treatment modality for a select and easily genetically definable group of ALT tumors, and also define telomeric fusion as a biomarker of drug action in these tumors.

Clinical, histopathological, and molecular analyses of IDH-wild-type WHO grade II-III gliomas to establish genetic predictors of poor prognosis

The genetic features of isocitrate dehydrogenase-wild-type (IDH-wt) lower-grade gliomas (LGGs; World Health Organization grades II and III) are not well defined. This study analyzed the genetic and other features of IDH-wt LGGs to develop a subclassification that can be used to predict their prognosis. Clinical, histopathological, and genetic features of 35 cases of diffuse IDH-wt astrocytoma and IDH-wt anaplastic astrocytoma were analyzed. The following genetic factors were examined: mutations of B-rapidly accelerated fibrosarcoma, telomerase reverse transcriptase promoter (TERTp), histone 3 family 3A, and alpha-thalassemia/mental retardation syndrome, X-linked; and copy number aberrations. In the univariate analysis, the following factors were associated with poor overall survival (OS): the histopathological diagnosis, TERTp mutation, the gain of chromosome 7 (+ 7), and the loss of chromosome 10q (- 10q). In the multivariate analysis, + 7, - 10q, and TERTp mutation were independent prognostic factors associated with poor OS. The median OS was significantly worse for patients who harbored at least one of these factors than for those without any of them (18.5 vs. 54.5 months, P = 0.002). The subclassification of IDH-wt LGGs according to the genetic factors + 7, - 10q, and TERTp mutation is potentially useful for predicting the prognosis.

An epilepsy-associated glioneuronal tumor with mixed morphology harboring FGFR1 mutation

Glioneuronal tumor (GNT) is a rare central nervous system neoplasm composed of glial and neuronal components. Making the specific diagnosis of GNT can be challenging due to histopathological and genetical similarities among some GNTs and low-grade gliomas. We report a case of GNT with rosette-forming glioneuronal tumor, dysembryoplastic neuroepithelial tumor, and pilocytic astrocytoma-like morphology harboring FGFR1 mutation. A 16-year-old female presented with absence seizures. Magnetic resonance imaging revealed a right temporal lobe mass with multinodular enhancement by gadolinium administration. The tumor was mostly composed of oligodendrocyte-like cells (OLCs) with variable perinuclear haloes. Abundant Rosenthal fibers and eosinophilic granular bodies were identified. Neither mitotic figures nor areas of necrosis were seen. Focal neurocytic rosette features, involving ring-like arrays of OLCs around eosinophilic cores, were observed. Direct sequencing showed a missense mutation in FGFR1 K656E, whereas FGFR1 N546K, PIK3CA, and BRAF V600E were intact. KIAA1549-BRAF fusion was not detected by fluorescence in situ hybridization analysis.

Magnetic Resonance Imaging and Proton Magnetic Resonance Spectroscopy for Differentiating Between Enhanced Gliomas and Malignant Lymphomas

BACKGROUND

Although the treatment strategies for malignant lymphomas and gliomas differ, it is usually difficult to preoperatively distinguish between them. Magnetic resonance spectroscopy (MRS) was recently reported to be useful for preoperative diagnoses; however, MRS data analysis using LCModel, which is a quantitative and objective method, was performed in only a few of the existing reports.

METHODS

The clinical characteristics, conventional magnetic resonance imaging findings, and MRS parameters using LCModel were evaluated to identify the factors that can help distinguish between malignant lymphomas and enhanced gliomas.

RESULTS

In total, 59 cases were evaluated, including 13 cases of malignant lymphoma, 1 case of pilocytic astrocytoma, 5 cases of grade Ⅱ glioma, 5 cases of grade Ⅲ glioma, and 35 cases of glioblastoma. There was no correlation between clinical characteristics (sex and age) and diagnosis. Neither T1- nor T2-weighted image was useful for differentiation between the 2 forms of tumors, but the apparent diffusion coefficient minimum value was useful for distinguishing malignant lymphomas from gliomas, with an area under the curve (AUC) value of 0.852. MRS analysis using LCModel revealed differences in glutamate (Glu), N-acetylaspartate (NAA) + N-acetylaspartylglutamate (NAAG), Glu + glutamine, and Lipid (Lip) 13a + Lip13b between malignant lymphomas and gliomas. The largest AUC was 0.904, which was obtained for the Glu level, followed by 0.883 and 0.866 for NAA + NAAG and Lip13a + Lip13b, respectively.

CONCLUSIONS

Quantitative analysis of proton-MRS using LCModel is considered to be a valuable method for distinguishing between gliomas and malignant lymphomas.

c-Met Expression Is a Useful Marker for Prognosis Prediction in IDH-Mutant Lower-Grade Gliomas and IDH-Wildtype Glioblastomas

OBJECTIVE

c-Met has been shown to be associated with tumor growth in several human cancers. This study aims to evaluate the correlation between the c-Met expression and histopathologic/clinical characteristics.

METHODS

A total of 153 patients with histologically defined World Health Organization grade II-IV diffuse astrocytic and oligodendroglial tumors were analyzed.

RESULTS

For each histopathologic diagnosis, the number of cases and positive rate of c-Met expression are as follows: oligodendroglioma, IDH-mutant, and 1p19q codeletion (OD): 16 cases, 6.3%; anaplastic oligodendroglioma, IDH-mutant, and 1p19q codeletion (AO): 11 cases, 36.4%; diffuse astrocytoma (DA), IDH-mutant: 21 cases, 28.6%; anaplastic astrocytoma (AA), IDH- mutant: 15 cases, 20%; glioblastoma, IDH-mutant: 2, 100%, DA, IDH-wildtype: 9 cases, 33.3%; AA, IDH-wildtype: 20 cases, 30.0%; and glioblastoma, IDH-wildtype: 59 cases, 52.5%. c-Met expression was correlated with progression-free survival in oligodendroglial tumors and glioblastoma, IDH-wildtype. Furthermore, it was correlated with overall survival in AO, oligodendroglial tumors, DA, IDH-mutant, DA, IDH-wildtype, and glioblastoma, IDH-wildtype, and tend to be correlated with overall survival in IDH-mutant lower-grade astrocytic tumors.

CONCLUSIONS

c-Met expression was revealed to be a useful marker for prognosis prediction in IDH-mutant lower-grade gliomas and glioblastoma, IDH-wildtype, representing a new independent prognostic marker that can be easily measured.

Significance of molecular classification of ependymomas: C11orf95-RELA fusion-negative supratentorial ependymomas are a heterogeneous group of tumors

Extensive molecular analyses of ependymal tumors have revealed that supratentorial and posterior fossa ependymomas have distinct molecular profiles and are likely to be different diseases. The presence of C11orf95-RELA fusion genes in a subset of supratentorial ependymomas (ST-EPN) indicated the existence of molecular subgroups. However, the pathogenesis of RELA fusion-negative ependymomas remains elusive. To investigate the molecular pathogenesis of these tumors and validate the molecular classification of ependymal tumors, we conducted thorough molecular analyses of 113 locally diagnosed ependymal tumors from 107 patients in the Japan Pediatric Molecular Neuro-Oncology Group. All tumors were histopathologically reviewed and 12 tumors were re-classified as non-ependymomas. A combination of RT-PCR, FISH, and RNA sequencing identified RELA fusion in 19 of 29 histologically verified ST-EPN cases, whereas another case was diagnosed as ependymoma RELA fusion-positive via the methylation classifier (68.9%). Among the 9 RELA fusion-negative ST-EPN cases, either the YAP1 fusion, BCOR tandem duplication, EP300-BCORL1 fusion, or FOXO1-STK24 fusion was detected in single cases. Methylation classification did not identify a consistent molecular class within this group. Genome-wide methylation profiling successfully sub-classified posterior fossa ependymoma (PF-EPN) into PF-EPN-A (PFA) and PF-EPN-B (PFB). A multivariate analysis using Cox regression confirmed that PFA was the sole molecular marker which was independently associated with patient survival. A clinically applicable pyrosequencing assay was developed to determine the PFB subgroup with 100% specificity using the methylation status of 3 genes, CRIP1, DRD4 and LBX2. Our results emphasized the significance of molecular classification in the diagnosis of ependymomas. RELA fusion-negative ST-EPN appear to be a heterogeneous group of tumors that do not fall into any of the existing molecular subgroups and are unlikely to form a single category.

Abstract 2845: The mechanisms of resistance to temozolomide in glioma cells

Glioblastoma is one of the most aggressive tumor in the central nervous system tumors, with 5-year survival rates of less than 10%. The standard therapy for glioblastomas is maximal safe resection, followed by radiation therapy and chemotherapy with temozolomide (TMZ). One of the reasons of the worse prognosis of the tumor is the acquisition of resistance to TMZ in glioma cells. TMZ is a DNA-methylating agent. TMZ-induced O6-methylguanine adducts, in the absence of repair by O6-methylguanine DNA methyltransferase (MGMT), mispair with thymine during the next DNA replication cycle, leading to futile DNA mismatch repair (MMR) by the MMR system, formation of double strand breaks (DSBs) and eventual cell death of glioma cells. Several mechanisms have been proposed about the acquisition of resistance to TMZ in glioblastomas, such as changes of expression of MGMT, MMR, nucleotide excision repair and homologous recombination (HR). To clarify the mechanisms of resistance to TMZ and to find the way to overcome the resistance to TMZ, several clones of U251 cells resistant to TMZ were obtained and analyzed. FACS analyses showed several patterns of cell cycle distributions of the cells treated with TMZ. #3 resistant clone showed G2 arrest at day3 after TMZ exposure and this arrest was abrogated sooner compared to the G2 arrest of parental U251. TMZ did not induce G2 arrest in #8 resistant clone. Consistent with the results, TMZ-induced DSBs in #3 resistant cells were rapidly disappeared compared to those in U251 cells, and the DSBs were least induced by TMZ in #8 resistant cells. The expression of MGMT was not found in U251 parental cells, #3 cells nor #8 cells, which mean MGMT was not associated with the resistance to TMZ in those cells. The protein levels of MSH6, which was associated with MMR, was reduced in #8 cells. The inhibitor of PLK1 or PARP reduced the cell growth independent of MMR. The ability of HR was increased in #3 resistant clone. By suppression of Rad51, which was major factor associated with HR, the resistant #3 clone was re-sensitized to TMZ, however #8 was not. These results suggested that inhibition of HR may be a viable means to resensitize some kinds of temozolomide-resistant gliomas to TMZ.

Citation Format: Shigeo Ohba, Yuichi Hirose. The mechanisms of resistance to temozolomide in glioma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2845.

Mutant IDH1 Cooperates with ATRX Loss to Drive the Alternative Lengthening of Telomere Phenotype in Glioma

A subset of tumors use a recombination-based alternative lengthening of telomere (ALT) pathway to resolve telomeric dysfunction in the absence of TERT. Loss-of-function mutations in the chromatin remodeling factor ATRX are associated with ALT but are insufficient to drive the process. Because many ALT tumors express the mutant isocitrate dehydrogenase IDH1 R132H, including all lower grade astrocytomas and secondary glioblastoma, we examined a hypothesized role for IDH1 R132H in driving the ALT phenotype during gliomagenesis. In p53/pRb-deficient human astrocytes, combined deletion of ATRX and expression of mutant IDH1 were sufficient to create tumorigenic cells with ALT characteristics. The telomere capping complex component RAP1 and the nonhomologous DNA end joining repair factor XRCC1 were each downregulated consistently in these tumorigenic cells, where their coordinate reexpression was sufficient to suppress the ALT phenotype. RAP1 or XRCC1 downregulation cooperated with ATRX loss in driving the ALT phenotype. RAP1 silencing caused telomere dysfunction in ATRX-deficient cells, whereas XRCC1 silencing suppressed lethal fusion of dysfunctional telomeres by allowing IDH1-mutant ATRX-deficient cells to use homologous recombination and ALT to resolve telomeric dysfunction and escape cell death. Overall, our studies show how expression of mutant IDH1 initiates telomeric dysfunction and alters DNA repair pathway preferences at telomeres, cooperating with ATRX loss to defeat a key barrier to gliomagenesis.Significance: Studies show how expression of mutant IDH1 initiates telomeric dysfunction and alters DNA repair pathway preferences at telomeres, cooperating with ATRX loss to defeat a key barrier to gliomagenesis and suggesting new therapeutic options to treat low-grade gliomas. Cancer Res; 78(11); 2966-77. ©2018 AACR.

A retrospective study of bevacizumab for treatment of brainstem glioma with malignant features

Brainstem glioma is impossible to resect completely, and patients with this type of glioma show a poor prognosis. Therefore, a more effective adjuvant therapy is required to prolong survival. Bevacizumab is an endothelial growth factor monoclonal antibody with strong anti-vascular effects, which may suppress tumor progression. We performed a retrospective study of data from 6 patients with brainstem glioma showing malignant features who were treated with bevacizumab. Tumor-associated lesions, as evaluated by T2 weighted or fluid-attenuated inversion-recovery magnetic resonance imaging, were reduced in all patients, although the timing of the start of bevacizumab administration and pretreatment were not uniform. Clinical symptoms improved in 4 patients and progression was inhibited in 2 patients. The Karnofsky performance status improved from 56.7 to 71.7 on average. The median reduction ratio of tumor-associated lesions was 76.3%, but tumor suppression did not last in any of the cases. Furthermore, 5 patients died of tumor progression, and 1 patient died of a complication of necrotizing colitis. The median progression-free survival after bevacizumab administration was 7 months. The median overall survival after diagnosis was 16.5 months. Bevacizumab might be a potential therapeutic option for progressive brainstem gliomas with malignant features.

Current and Future Drug Treatments for Glioblastomas

Glioblastomas are the most aggressive of all gliomas and have the worst prognosis, with 5-year survival rates of less than 10%. Temozolomide (TMZ) is a DNA-methylating agent. Now that TMZ is available, the standard treatment is maximal safe resection, followed by treatment with radiation and TMZ. TMZ has also been used for maintenance therapy. Recently, bevacizumab, which is a monoclonal antibody to vascular endothelial growth factor, has been used for the initial treatment of glioblastomas and for the treatment of recurrent glioblastomas. A 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) wafer can also be placed on the surface of the cavity after near-complete tumor resection. These are currently the three drugs that are most often used to treat glioblastomas. In the near future, other therapeutic options such as immunotherapy may be used to treat glioblastomas.