Mutant IDH inhibitors induce lineage differentiation in IDH-mutant oligodendroglioma

A subset of patients with IDH-mutant glioma respond to inhibitors of mutant IDH (IDHi), yet the molecular underpinnings of such responses are not understood. Here, we profiled by single-cell or single-nucleus RNA-sequencing three IDH-mutant oligodendrogliomas from patients who derived clinical benefit from IDHi. Importantly, the tissues were sampled on-drug, four weeks from treatment initiation. We further integrate our findings with analysis of single-cell and bulk transcriptomes from independent cohorts and experimental models. We find that IDHi treatment induces a robust differentiation toward the astrocytic lineage, accompanied by a depletion of stem-like cells and a reduction of cell proliferation. Furthermore, mutations in NOTCH1 are associated with decreased astrocytic differentiation and may limit the response to IDHi. Our study highlights the differentiating potential of IDHi on the cellular hierarchies that drive oligodendrogliomas and suggests a genetic modifier that may improve patient stratification.

Multidrug chemotherapy, whole-brain radiation and cytarabine therapy for primary central nervous system lymphoma in elderly patients with dose modification based on geriatric assessment: study protocol for a phase II, multicentre, non-randomised study

INTRODUCTION

Multidrug chemoimmunotherapy with rituximab, high-dose methotrexate, procarbazine and vincristine (R-MPV) is a standard therapy for younger patients with primary central nervous system lymphoma (PCNSL); however, prospective data regarding its use in elderly patients are lacking. This multi-institutional, non-randomised, phase II trial will assess the efficacy and safety of R-MPV and high-dose cytarabine (HD-AraC) for geriatric patients with newly diagnosed PCNSL.

METHODS AND ANALYSIS

Forty-five elderly patients will be included. If R-MPV does not achieve complete response, the patients will undergo reduced-dose, whole-brain radiotherapy comprising 23.4 Gy/13 fractions, followed by local boost radiotherapy comprising 21.6 Gy/12 fractions. After achieving complete response using R-MPV with or without radiotherapy, the patients will undergo two courses of HD-AraC. All patients will undergo baseline geriatric 8 (G8) assessment before HD-AraC and after three, five and seven R-MPV courses. Patients with screening scores of ≥14 points that decrease to <14 points during subsequent treatment, or those with screening scores <14 points that decrease from the baseline during subsequent treatment are considered unfit for R-MPV/HD-AraC. The primary endpoint is overall survival, and the secondary endpoints are progression-free survival, treatment failure-free survival and frequency of adverse events. The results will guide a later phase III trial and provide information about the utility of a geriatric assessment for defining chemotherapy ineligibility.

ETHICS AND DISSEMINATION

This study complies with the latest Declaration of Helsinki. Written informed consent will be obtained. All participants can quit the study without penalty or impact on treatment. The protocol for the study, statistical analysis plan and informed consent form have been approved by the Certified Review Board at Hiroshima University (CRB6180006) (approval number: CRB2018-0011). The study is ongoing within nine tertiary and two secondary hospitals in Japan. The findings of this trial will be disseminated through national and international presentations and peer-reviewed publications.

TRIAL REGISTRATION

jRCTs061180093.

2-Hydroxyglutarate magnetic resonance spectroscopy in adult brainstem glioma

OBJECTIVE

Adult brainstem gliomas (BSGs) are rare tumors of the CNS that are poorly understood. Upregulation of the oncometabolite 2-hydroxyglutarate (2HG) in the tumor indicates the mutation of isocitrate dehydrogenase (IDH), which can be detected by magnetic resonance spectroscopy (MRS). Although histological examination is required for the definitive diagnosis of BSG, 2HG-optimized MRS (2HG-MRS) may be useful, considering the difficult nature of brainstem lesion biopsy. The aim of this study was to evaluate the utility of 2HG-MRS for diagnosing IDH-mutant adult BSG.

METHODS

Patients with a radiographically confirmed brainstem tumor underwent 3T MRS. A single voxel was set in the lesion with reference to the T2 or fluid-attenuated inversion recovery image and analyzed according to the 2HG-tailored MRS protocol (point-resolved spectroscopic sequence; echo time 35 msec). All patients underwent intraoperative navigation-guided or CT-guided stereotactic biopsy for histopathological diagnosis. The status of IDH and H3K27M mutations was confirmed by immunohistochemistry and direct DNA sequencing. In addition, the authors examined the relationship between patients' 2HG concentrations and survival time.

RESULTS

Ten patients (7 men, 3 women; median age 33.5 years) underwent 2HG-MRS and biopsy. Four patients had an H3K27M mutation and 4 had an IDH1 mutation (1 R132H canonical IDH mutation, 2 R132S and 1 R132G noncanonical IDH mutations). Two had neither H3K27M nor IDH mutations. The H3K27M and IDH mutations were mutually exclusive. Most tumors were located in the pons. There was no significant radiological difference between mutant H3K27M and IDH on a conventional MRI sequence. A 2HG concentration ≥ 1.8 mM on MRS demonstrated 100% (95% CI 28%-100%) sensitivity and 100% (95% CI 42%-100%) specificity for IDH-mutant BSG (p = 0.0048). The median overall survival was 10 months in IDH-wild-type BSG patients (n = 6) and could not be estimated in IDH-mutant BSG patients (n = 4) due to the small number of deaths (p = 0.008).

CONCLUSIONS

2HG-MRS demonstrated high sensitivity and specificity for the prediction of IDH-mutant BSG. In addition, 2HG-MRS may be useful for predicting the prognosis of adult BSG patients.

MPC-16 CHARACTERISTICS AND PROGNOSTIC FACTORS OF H3K27M-MUTANT DIFFUSE MIDLINE GLIOMA

H3 K27M-mutant diffuse midline gliomas (DMG) is a still challenging disease with no effective medical therapies. We analyzed the characteristics and prognostic factors of 64 patients with midline gliomas including 18 patients with H3 K27M-mutant DMG treated in Kobe University Hospital from 2006 to 2021. The median age at diagnosis in midline gliomas was 50.1 years (range: 14-82 y). All tumors were located in thalamus n=25, corpus callosum n=8, brainstem n=8, spinal cord n=6, cerebellum n=15, and pineal region n=2. Isocitrate dehydrogenase 1 (IDH1) and H3 K27 mutation was recognized in 6 and 18 patients, respectively, which was mutually exclusive. In all midline gliomas, the identification of an H3 K27M mutation was significantly a poor prognosis factor (median 19.8 months vs 27.9 months, p=0.042). Compared to midline gliomas without histone H3 and IDH1 mutations (IDH1/H3 wild type), however, H3 K27M-mutant DMG had no worse overall survival (median 19.8 months vs 15.9 months, p=0.51). H3 K27M-mutant DMG is considered as a distinct WHO Grade 4 regardless of histological features, but the biological properties of H3 K27M mutation is not yet defined in IDH1 wild-type midline gliomas.

Ror1 is expressed inducibly by Notch and hypoxia signaling and regulates stem cell-like property of glioblastoma cells

Ror1 plays a crucial role in cancer progression by regulating cell proliferation and migration. Ror1 is expressed abundantly in various types of cancer cells and cancer stem-like cells. However, the molecular mechanisms regulating expression of Ror1 in these cells remain largely unknown. Ror1 and its putative ligand Wnt5a are expressed highly in malignant gliomas, especially in glioblastomas, and the extents of Ror1 expression are correlated positively with poorer prognosis in patients with gliomas. We show that Ror1 expression can be upregulated in glioblastoma cells under spheroid culture, but not adherent culture conditions. Notch and hypoxia signaling pathways have been shown to be activated in spheroid-forming glioblastoma stem-like cells (GSCs), and Ror1 expression in glioblastoma cells is indeed suppressed by inhibiting either Notch or hypoxia signaling. Meanwhile, either forced expression of the Notch intracellular domain (NICD) in or hypoxic culture of glioblastoma cells result in enhanced expression of Ror1 in the cells. Consistently, we show that both NICD and hypoxia-inducible factor 1 alpha bind to upstream regions within the Ror1 gene more efficiently in GSCs under spheroid culture conditions. Furthermore, we provide evidence indicating that binding of Wnt5a to Ror1, upregulated by Notch and hypoxia signaling pathways in GSCs, might promote their spheroid-forming ability. Collectively, these findings indicate for the first time that Notch and hypoxia signaling pathways can elicit a Wnt5a-Ror1 axis through transcriptional activation of Ror1 in glioblastoma cells, thereby promoting their stem cell-like property.

EXTH-39. BIOMARKER DRIVEN TARGETING OF RECURRENT IDH MUTANT GLIOMA WITH ABEMACICLIB

Despite initial responsiveness to standard treatments like radiation and chemotherapy, IDH mutant gliomas inevitably recur, become more clinically aggressive, and lead to untimely death. The aggressive change in clinical outcome is driven by insensitivity to conventional methods of treatment, necessitating an improved therapeutic strategy at this stage of the disease. Greater than 20% of recurrent IDH mutant gliomas exhibit homozygous loss of CDKN2A, leading to the loss of the endogenous CDK4/6 inhibitor p16 and aberrant signaling through the CDK-RB pathway. We hypothesized that CDKN2A loss leads to enhanced sensitivity to CDK4/6 inhibitors which have been approved for use in a variety of other cancer types. We examined the sensitivity of a panel of patient-derived IDH mutant gliomas with either endogenous CDKN2A loss or CRISPR-mediated gene deletion to treatment with CDK4/6 inhibitors. We observed a correlation between CDKN2A loss and enhanced cytotoxicity following abemaciclib treatment in these glioma models. We have characterized the cell cycle profile following abemaciclib treatment by flow cytometry and western blotting in both sensitive and resistant lines. Further, abemaciclib treatment resulted in significant slowing of tumor growth rate in a subcutaneous patient-derived IDH mutant glioma model. Survival studies in an intracranial model are ongoing. These preclinical results provide foundational data to support a biomarker-driven clinical trial of CDK4/6 inhibitors in patients with recurrent IDH mutant glioma.

RBIO-07. HIGHER CSF IL-10 CORRELATE WITH BRAIN ATROPHY AFTER WHOLE BRAIN RADIATION THERAPY IN PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA

Whole brain radiation therapy (WBRT) to primary central nervous system lymphoma (PCNSL) correlate with brain atrophy and leukoencephalopathy on serial computed tomography or MRI scans, negatively impacting cognitive function and quality of life. We retrospectively evaluated 53 patients with histologically proven PCNSL who underwent cerebrospinal fluid (CSF) examination including β2-MG, sIL2R, CXCL13, and IL-10 preoperatively. All patients were newly diagnosed and followed up every 3 months from the day they were discharged from the hospital. Follow up period is at least 1 year from last day of chemotherapy. Clinical data included patient demographics, radiological and characteristics; whole brain volume (mm2) calculated from BainLabTM automatically, Global Cortical Atrophy (GCA) for global brain atrophy, Medial Temporal Atrophy (MTA) for temporal atrophy, and Fazekas scale for white matter lesions. The unpaired t test and multivariable liner regression were used to examine the clinical, CSF and radiological characteristics of patients. The mean age at symptom onset was 65.2 years (47-85 years). Thirty three of 53 (62%) patients underwent WBRT with chemotherapy (WBRT group). In all patients, multivariable analysis revealed WBRT correlate with brain volume reduction (p=0.0005) and progression of temporal lobe atrophy (p=0.0056). In addition, Age correlated with increasing white matter lesions at 1 year after chemotherapy (p=0.0422). In WBRT group, multivariable analysis indicated that high CSF IL-10 level accelerated brain volume reduction (p=0.0122) and temporal lobe atrophy (p=0.0343) at 6 months after chemotherapy. However, there were no significant factor for influencing brain atrophy at 1 year. Higher IL-10 ( &gt; 100mg/ml) level demonstrated higher brain atrophy rate (p=0.0366) and severe temporal atrophy at 1 year (p=0.0214). In elderly patients with high preoperative CSF IL-10 levels, cerebral atrophy and toxic leukoencephalopathy may progress in short period of time after WBRT. We should consider treatment strategy that avoid WBRT, such as R-MPV chemotherapy, for PCNSL patients.

TMIC-20. SERINE AND ONE-CARBON METABOLISM ADAPTING GLIOMA CELLS TO LOW GLUTAMINE MICROENVIRONMENT

Cancer cells optimize nutrient utilization to supply energetic and biosynthetic pathways. This metabolic process also includes redox maintenance and epigenetic regulation through nucleic acid and protein methylation, which enhance tumorigenicity and clinical resistance. However, less is known about how cancer cells exhibit metabolic flexibility to sustain cell growth and survival from low nutrient microenvironment. Here, we find that serine and glycine levels were higher in low-nutrient regions of tumors in glioblastoma multiforme (GBM) patients than they were in other regions. Metabolic and functional studies in malignant glioma cells demonstrated that serine availability and one-carbon metabolism support glioma cell survival following glutamine deprivation. Serine synthesis was mediated through autophagy rather than glycolysis. Gene expression analysis identified upregulation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) to regulate one-carbon metabolism in malignant glioma cells and GBM patient-derived sphere cells. In clinical samples, MTHFD2 expression was highest in the nutrient-poor areas around “pseudopalisading necrosis.” Genetic and pharmacological suppression of MTHFD2 caused tumor cell death and growth inhibition of glioma cells upon glutamine deprivation as well as autophagy inhibition did. These results may have important implications for serine-dependent one-carbon metabolism for glioma cells to survive glutamine starvation and suggest a new therapeutic strategy for patients with malignant glioma.

BIOM-40. COMPARATIVE STUDY OF INFLAMMATORY MARKERS IN THE CEREBROSPINAL FLUID OF PATIENTS WITH GLIOMA AND CENTRAL NERVOUS SYSTEM MALIGNANT LYMPHOMA

INTRODUCTION

Cytokines in the cerebrospinal fluid (CSF) are useful as markers for primary central nervous system malignant lymphoma (PCBSL). However, there are few reports of CSF markers in glioma. We analyzed and examined glioma and PCNSL CSF inflammation-related mediators.

MATERIALS AND METHODS

The patients with glioma and PCNSL who were operated on at Kobe University between 2006 and 2017 and whose histology was diagnosed, and whose CSF was stored at -80 °C before treatment. Using Bio-Plex Pro Human Inflammation Assays (Bio-Rad Laboratories, Inc.), 37 types of inflammation-related molecules such as TNF superfamilies, interferonss, and Interleukines were measured and compared with glioma and PCNSL.

RESULTS

The subjects were 53 glioma patients and 24 PCNSL patients. There were 22 types of significant differences between glioma and PCNSL, 18 with high PCNSL and 4 with high glioma. In addition to IL-10, which has been reported so far, the significant higher concentrations in PCNSL was found in Osteopontin, TNFSF8, TNFSF12, TNFSF13, TNFSF13B, TNFSF14, sTNF-R1, sTNF-R2, IL-6Ra, IL-8, IL-12(p40), IL-20, IL-27, sCD163, MMP2, MMP3, CHI3L1. On the other hand, IL-2, Il-12(p70), IL-22, and MMP-1 levels were significant higher in CSF in glioma. Although CD163 is an important molecule as a marker for M2 macrophages, immunostaining of tissues showed no significant difference in infiltration between Glioblastoma and PCNSL. This suggests that M2 macrophages infiltrating PCNSL and Glioblastoma have different activation states.

CONCLUSION

PCNSL had higher levels of inflammatory mediators such as TNF-related molecules. PCNSL was significantly higher in sCD163 than in glioblastoma, suggesting different activation of intratumoral M2 macrophages.

Effect of coordinator-based osteoporosis intervention on quality of life in patients with fragility fractures: a prospective randomized trial

We examined the effects of the coordinator-based intervention on quality of life (QOL) in the aftermath of a fragility fracture, as well as factors predictive of post-fracture QOL. The coordinator-based interventions mitigated the decrease in QOL. Secondary fracture after primary fracture, however, was a significant predictor of lower QOL.

PURPOSE

This study aimed to determine the effects of the coordinator-based intervention on QOL in the aftermath of a fragility fracture, as well as factors predictive of post-fracture QOL, in an Asian population.

METHODS

Patients with new fractures in the intervention group received the coordinator-based intervention by a designated nurse certified as a coordinator, within 3 months of injury. QOL was evaluated using the Japanese version of the EuroQol 5 Dimension 5 Level (EQ-5D-5L) scale  before the fracture (through patient recollections) and at 0.5, 1, and 2 years after the primary fracture.

RESULTS

Data for 141 patients were analyzed: 70 in the liaison intervention (LI) group and 71 in the non-LI group. Significant intervention effects on QOL were observed at 6 months after the fracture; the QOL score was 0.079 points higher in the LI group than in the non-LI group (p=0.019). Further, the LI group reported significantly less pain/discomfort at 2 years after the fracture, compared to the non-LI group (p=0.037). In addition, secondary fractures were found to significantly prevent improvement and maintenance of QOL during the recovery period (p=0.015).

CONCLUSION

Short-term intervention effects were observable 6 months after the primary fracture, with the LI group mitigated the decrease in QOL. Few patients in the LI group reported pain/discomfort 2 years after the fracture, but there is uncertainty regarding its clinical significance. Secondary fracture after initial injury was a significant predictor of lower QOL after a fracture.

CBMS-5 One-carbon metabolism protect glioma cells under glutamine starvation through upregulation of MTHFD2

Cancer cells optimize nutrient utilization to supply energetic and biosynthetic pathways. However, less is known about how cancer cells exhibit metabolic flexibility to sustain cell growth and survival from nutrient starvation. Here, we find that serine and glycine levels were higher in low-nutrient regions of tumors in glioblastoma multiforme (GBM) patients than they were in other regions. Metabolic and functional studies demonstrated that serine availability and one-carbon metabolism support glioma cell survival following glutamine deprivation. Serine synthesis was mediated through autophagy rather than glycolysis. Gene expression analysis identified upregulation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) to regulate one-carbon metabolism. In clinical samples, MTHFD2 expression was highest in the nutrient-poor areas around pseudopalisading necrosis. Genetic suppression of MTHFD2 and autophagy inhibition caused tumor cell death and growth inhibition of glioma cells upon glutamine deprivation. These results suggest new therapeutic targets for glioma cells adapting to a low-nutrient microenvironment.

NI-7 Diffusion-weighted imaging for monitoring acute response and recurrence after photodynamic therapy in malignant gliomas

Background

Photodynamic therapy (PDT) subsequent to surgical tumor removal is a novel light-activated localized treatment for malignant glioma. Although PDT provides effective local control, even PDT cannot completely suppress local recurrence of malignant glioma. We previously reported that the acute response of malignant glioma to PDT could be detected as linear hyperintense signals on diffusion-weighted imaging (DWI) and a decline in apparent diffusion coefficient (ADC) values that were asymptomatic and transient. However, their long-term clinical significance has not yet been examined. This study aimed to clarify the link between the hyperintense signal on DWI as an acute response and recurrence after PDT in malignant glioma.

Methods

Thirty consecutive patients (16 men, 14 women; median age 60.5 years) underwent PDT for malignant glioma at our institution between 2017 and 2020. We analyzed signal changes on DWI after PDT and the link between these findings and the recurrence pattern.

Results

In all patients, linear hyperintense signals of 5–7 mm on DWI were detected at the surface of the resected cavity from day 1 after PDT. These changes matched the PDT-irradiated area and disappeared in about 30 days without any neurological deterioration. Of the 30 patients, 19 (63%) exhibited recurrence: local recurrence in 10 (33%), distant recurrence in 1 (3%), and dissemination in 8 (27%). All local recurrences arose from areas that did not show a hyperintense signal on DWI obtained on day 1 after PDT. Patients with distant recurrence or dissemination tended to have uninterrupted hyperintense signal on DWI obtained on day 1 after PDT.

Conclusion

The local recurrence in malignant glioma after PDT occurred in the areas without hyperintense signal on DWI as the acute response to PDT. This characteristic finding could aid in the monitoring of not only PDT-irradiated area but also local recurrence site after PDT.

TAMI-20. GLIOMA CELLS REPROGRAM SERINE-DEPENDENT ONE-CARBON METABOLISM TO SURVIVE GLUTAMINE STARVATION

Cancer cells optimize nutrient utilization to supply energetic and biosynthetic pathways. This metabolic process also includes redox maintenance and epigenetic regulation through nucleic acid and protein methylation, which enhance tumorigenicity and clinical resistance. However, less is known about how cancer cells exhibit metabolic flexibility to sustain cell growth and survival from nutrient starvation. Here, we find that serine and glycine levels were higher in low-nutrient regions of tumors in glioblastoma multiforme (GBM) patients than they were in other regions. Metabolic and functional studies in GBM cells demonstrated that serine availability and one-carbon metabolism support glioma cell survival following glutamine deprivation. Serine synthesis was mediated through autophagy rather than glycolysis. Gene expression analysis identified upregulation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) to regulate one-carbon metabolism in GBM patient-derived sphere cells as well as in GBM cells. In clinical samples, MTHFD2 expression was highest in the nutrient-poor areas around “pseudopalisading necrosis.” Genetic suppression of MTHFD2 and autophagy inhibition caused tumor cell death and growth inhibition of glioma cells upon glutamine deprivation. These results may have important implications for serine-dependent one-carbon metabolism for glioma cells to survive glutamine starvation and suggest a new therapeutic strategy for patients with malignant glioma.

EXTH-55. TARGETING RECURRENT IDH MUTANT GLIOMA WITH CDK4/6 INHIBITION

Despite initial responsiveness to standard treatments like radiation and chemotherapy, IDH mutant gliomas inevitably recur, become more clinically aggressively and lead to untimely death. Recurrent IDH mutant tumors are less responsive to conventional treatments, highlighting the need for improved therapeutic strategies at this stage of the disease. At least 20% of recurrent IDH mutant gliomas exhibit homozygous loss of CDKN2A, which results in aberrant signaling through the CDK-RB pathway. We hypothesized that CDKN2A loss leads to enhanced sensitivity to CDK4/6 inhibitors, which are approved for use in a variety of other cancer types. We examined the relationship between CDK4/6 inhibitor sensitivity and CDKN2A loss using patient-derived models of IDH mutant glioma with endogenous CDKN2A homozygous deletion as well as with CRIPSR-mediated gene deletion. We observed enhanced cytotoxicity in glioma models with CDKN2A loss in vitro. Studies to examine the efficacy of CDK4/6 inhibitor treatment on slowing tumor growth in patient-derived xenograft models are ongoing. These preclinical results provide foundational data for design of a biomarker-driven clinical trial of CDK4/6 inhibitors in patients with recurrent IDH mutant glioma.

NIMG-15. 2-HYDROXYGLUTARATE MAGNETIC RESONANCE SPECTROSCOPY IN ADULT BRAINSTEM GLIOMA PATIENTS

OBJECTIVE

The onco-metabolite, 2-Hydroxyglutarate (2HG), is non-invasive biomarker for detecting isocitrate dehydrogenase (IDH) mutant glioma by MR-Spectroscopy. Especially 2HG-MRS may be useful in patients with brainstem lesions, where surgical biopsy presents high risk of neurological injury. Here, we examined the utility of 2HG-MRS for diagnosis of IDH mutant adult brainstem glioma.

METHODS

We conducted 3 tesla -MRS (3T-MRS) in 8 radiographically identified brainstem tumor (7 male and 1 female, median age 39). Single-voxel was localized from the T2-FLAIR using a 2HG-tailored MRS protocol (Philips, Achieva, PRESS, TE 35 ms). All patients underwent tumor biopsy using an intraoperative navigation system (Brain LABTM) or stereotactic biopsy system (Komai’s CT-stereotactic frame) before initial treatment. IDH and H3K27M status were diagnosed by IHC and DNA sequence.

RESULTS

3 cases were H3K27M and 4 cases were IDH mutant (R132H 1 case, R132S 2 cases, and R132G 1 case). 1 case were neither H3K27M nor IDH mutant. H3-K27 and IDH1 mutations were mutually exclusive. All tumor located at pons. There were no significant radiological difference between H3K27M and IDH mutant in conventional MRI sequence. Pearson's chi-square test demonstrated that 2HG concentrations &gt;1.5 mM were 100% sensitive and 75% specific for IDH mutant glioma (p = 0.0285). The median overall survival survival were 127 month in IDH mutant glioma (n=4) and 22.5 months in IDH wild-type glioma (n=4), respectively.

CONCLUSIONS

2HG in adult brainstem glioma was detected by conventional 3T-MRS successfully. A noninvasive 2HG-MRS may be useful diagnostic modality for evaluating molecular status and prognosis in brainstem glioma noninvasively.

Hyperintense signal on diffusion-weighted imaging for monitoring the acute response and local recurrence after photodynamic therapy in malignant gliomas

PURPOSE

Photodynamic therapy (PDT) subsequent to surgical tumor removal is a novel localized treatment for malignant glioma that provides effective local control. The acute response of malignant glioma to PDT can be detected as linear transient hyperintense signal on diffusion-weighted imaging (DWI) and a decline in apparent diffusion coefficient values without symptoms. However, their long-term clinical significance has not yet been examined. The aim of this study was to clarify the link between hyperintense signal on DWI as an acute response and recurrence after PDT in malignant glioma.

METHODS

Thirty patients (16 men; median age, 60.5 years) underwent PDT for malignant glioma at our institution between 2017 and 2020. We analyzed the signal changes on DWI after PDT and the relationship between these findings and the recurrence pattern.

RESULTS

All patients showed linear hyperintense signal on DWI at the surface of the resected cavity from day 1 after PDT. These changes disappeared in about 30 days without any neurological deterioration. During a mean post-PDT follow-up of 14.3 months, 19 patients (63%) exhibited recurrence: 10 local, 1 distant, and 8 disseminated. All of the local recurrences arose from areas that did not show hyperintense signal on DWI obtained on day 1 after PDT.

CONCLUSIONS

The local recurrence in malignant glioma after PDT occurs in an area without hyperintense signal on DWI as an acute response to PDT. This characteristic finding could aid in the monitoring of local recurrence after PDT.

Sirtuin activation targets IDH-mutant tumors

BACKGROUND

Isocitrate dehydrogenase (IDH)-mutant tumors exhibit an altered metabolic state and are critically dependent upon nicotinamide adenine dinucleotide (NAD+) for cellular survival. NAD+ steady-state levels can be influenced by both biosynthetic and consumptive processes. Here, we investigated activation of sirtuin (SIRT) enzymes, which consume NAD+ as a coenzyme, as a potential mechanism to reduce cellular NAD+ levels in these tumors.

METHODS

The effect of inhibition or activation of sirtuin activity, using (i) small molecules, (ii) clustered regularly interspaced short palindromic repeat/CRISPR associated protein 9 gene editing, and (iii) inducible overexpression, was investigated in IDH-mutant tumor lines, including patient-derived IDH-mutant glioma lines.

RESULTS

We found that Sirt1 activation led to marked augmentation of NAD+ depletion and accentuation of cytotoxicity when combined with inhibition of nicotinamide phosphoribosyltransferase (NAMPT), consistent with the enzymatic activity of SIRT1 as a primary cellular NAD+ consumer in IDH-mutant cells. Activation of Sirt1 through either genetic overexpression or pharmacologic Sirt1-activating compounds (STACs), an existing class of well-tolerated drugs, led to inhibition of IDH1-mutant tumor cell growth.

CONCLUSIONS

Activation of Sirt1 can selectively target IDH-mutant tumors. These findings indicate that relatively nontoxic STACs, administered either alone or in combination with NAMPT inhibition, could alter the growth trajectory of IDH-mutant gliomas while minimizing toxicity associated with cytotoxic chemotherapeutic regimens.

Efficiency of coordinator-based osteoporosis intervention in fragility fracture patients: a prospective randomized trial

We examined the effectiveness of coordinators' interventions to prevent secondary fractures in patients with fragility fractures. These coordinator-based interventions improved bone density assessment implementation and treatment rates, and enhanced treatment persistence rates in the early stages following fractures.

INTRODUCTION

This study aimed to determine the efficiency of coordinator-based osteoporosis intervention in fragility fracture patients during a 2-year period.

METHODS

A prospective intervention randomized control study was conducted at seven medical facilities from January 2015 to March 2017. Postmenopausal women and men over 50 years old with fragility fractures were randomly divided into the coordinator intervention (LI; 70 patients) and without intervention (non-LI; 71 patients) groups. The osteoporosis treatment rate, osteoporosis treatment persistence rate, fall rate, fracture incidence rate, and bone density measurement rate 3 months, 6 months, 1 year, and 2 years after registration were compared between the two groups. Non-parametric tests were used to analyze data at each inspection period.

RESULTS

The osteoporosis treatment initiation rate was significantly higher in the LI group than in the non-LI group (85.7% vs. 71.8%; p = 0.04). The LI group had significantly higher bone density assessment implementation rates than the non-LI group at the time of registration (90.0% vs. 69.0%; p = 0.00) and 6 months after registration (50.0% vs. 29.6%; p = 0.01), but not 1 or 2 years after registration. In addition, no significant differences in fall or fracture incidence rates were found between the two groups.

CONCLUSION

The coordinator-based interventions for fragility fractures improved bone density assessment implementation and treatment rates and enhanced treatment persistence rates in the early stages following bone fractures. The findings suggest that liaison intervention may help both fracture and osteoporosis physicians for the evaluation of osteoporosis and initiation and continuation of osteoporosis medication.

The Histopathologic and Radiologic Features of T2-FLAIR Mismatch Sign in IDH-Mutant 1p/19q Non-codeleted Astrocytomas

OBJECTIVE

The T2-FLAIR mismatch sign is a useful imaging sign in clinical magnetic resonance imaging studies for detecting isocitrate dehydrogenase (IDH)-mutant 1p/19q non-codeleted astrocytomas. However, the association between the mismatch sign and pathologic findings is poorly understood. Therefore, the aim of this study was to elucidate the relationship of histopathologic and radiologic features with the mismatch sign in IDH-mutant 1p/19q non-codeleted astrocytomas.

METHODS

We divided 17 IDH-mutant 1p/19q non-codeleted patients into 2 groups according to mismatch sign presence (WITH, n = 9; WITHOUT, n = 8) and retrospectively analyzed their pathologic findings and apparent diffusion coefficient (ADC) values. We also compared these findings between the tumor Core (central area) and Rim (marginal area).

RESULTS

In the pathologic analysis, Core of the WITH group contained numerous microcysts whereas Rim had abundant neuroglial fibrils and cellularity. In contrast, Core of the WITHOUT group had highly concentrated neuroglial fibrils. In ADC analysis, Core of the WITH group had significantly higher ADC values compared with Rim (P < 0.001). However, there was no significant difference between Core and Rim in the WITHOUT group (P = 0.12). The WITH group had a significantly higher Core/Rim ratio of ADC values compared with the WITHOUT group (P < 0.001).

CONCLUSIONS

This study provides evidence that a region-dependent microstructural difference could reflect the mismatch sign in IDH-mutant 1p/19q non-codeleted astrocytomas. Core of the mismatch sign characteristically had microcystic changes accompanied by higher ADC values, whereas Rim had abundant neuroglial fibrils and cellularity accompanied by lower ADC values.

Glioma cells require one-carbon metabolism to survive glutamine starvation

Cancer cells optimize nutrient utilization to supply energetic and biosynthetic pathways. This metabolic process also includes redox maintenance and epigenetic regulation through nucleic acid and protein methylation, which enhance tumorigenicity and clinical resistance. However, less is known about how cancer cells exhibit metabolic flexibility to sustain cell growth and survival from nutrient starvation. Here, we find that serine and glycine levels were higher in low-nutrient regions of tumors in glioblastoma multiforme (GBM) patients than they were in other regions. Metabolic and functional studies in GBM cells demonstrated that serine availability and one-carbon metabolism support glioma cell survival following glutamine deprivation. Serine synthesis was mediated through autophagy rather than glycolysis. Gene expression analysis identified upregulation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) to regulate one-carbon metabolism. In clinical samples, MTHFD2 expression was highest in the nutrient-poor areas around “pseudopalisading necrosis.” Genetic suppression of MTHFD2 and autophagy inhibition caused tumor cell death and growth inhibition of glioma cells upon glutamine deprivation. These results highlight a critical role for serine-dependent one-carbon metabolism in surviving glutamine starvation and suggest new therapeutic targets for glioma cells adapting to a low-nutrient microenvironment.

Metabolic changes and anti-tumor effects of a ketogenic diet combined with anti-angiogenic therapy in a glioblastoma mouse model

The ketogenic diet (KD) is a high fat and low carbohydrate diet that produces ketone bodies through imitation of starvation. The combination of KD and Bevacizumab (Bev), a VEGF inhibitor, is considered to further reduce the supply of glucose to the tumor. The metabolite changes in U87 glioblastoma mouse models treated with KD and/or Bev were examined using gas chromatography-mass spectrometry. The combination therapy of KD and Bev showed a decrease in the rate of tumor growth and an increase in the survival time of mice, although KD alone did not have survival benefit. In the metabolome analysis, the pattern of changes for most amino acids are similar between tumor and brain tissues, however, some amino acids such as aspartic acid and glutamic acid were different between tumors and brain tissues. The KD enhanced the anti-tumor efficacy of Bev in a glioblastoma intracranial implantation mouse model, based on lowest levels of microvascular density (CD31) and cellular proliferation markers (Ki-67 and CCND1) in KD + Bev tumors compared to the other groups. These results suggested that KD combined with Bev may be a useful treatment strategy for patients with GBM.

TAMI-30. LOCAL TARGETING OF NAD+ SALVAGE PATHWAY ALTERS THE IMMUNE TUMOR MICROENVIRONMENT AND ENHANCES CHECKPOINT IMMUNOTHERAPY IN GLIOBLASTOMA

The aggressive primary brain tumor glioblastoma (GBM) is characterized by aberrant metabolism that fuels its malignant phenotype. Diverse genetic sub-types of malignant glioma are sensitive to selective inhibition of the NAD+ salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT). However, the potential impact of NAD+ depletion on the brain tumor microenvironment has not been elaborated. In addition, systemic toxicity of NAMPT inhibition remains a significant concern. Here, we show that microparticle-mediated intratumoral delivery of NAMPT inhibitor GMX1778 induces specific immunological changes in the tumor microenvironment of murine GBM, characterized by upregulation of immune checkpoint PD-L1, recruitment of CD3+, CD4+ and CD8+ T cells and reduction of M2-polarized immunosuppressive macrophages. NAD+ depletion and autophagy induced by NAMPT inhibitors mediated the upregulation of PD-L1 transcripts and cell surface protein levels in GBM cells. NAMPT inhibitor modulation of the tumor immune microenvironment was therefore combined with PD-1 checkpoint blockade in vivo, significantly increasing the survival of GBM bearing animals. Thus, the therapeutic impacts of NAMPT inhibition extended beyond neoplastic cells, shaping surrounding immune effectors. Microparticle delivery and release of NAMPT inhibitor at the tumor site offers a safe and robust means to alter an immune tumor microenvironment that could potentiate checkpoint immunotherapy for glioblastoma.

TAMI-36. CONNEXIN 43 BLOCKADE INHIBITS PROLIFERATION IN IDH1-MUTANT GLIOMA CELLS

IDH1-mutant gliomas are characteristically sensitive to NAD+ depletion. It is known that NAD+ can move between cells through gap junctions, which provides an opportunity for treatments that prevent NAD+ sharing across tumor cells, effectively decreasing available NAD+. Previous studies have also shown the role of connexin 43 (Cx43) in mediating communication in glioma cell networks and have identified Cx43 as a potential mediator of temozolomide resistance in glioma. We hypothesized that blocking Cx43 would prevent intercellular NAD+ sharing in IDH-mutant gliomas, causing tumor cells to be more vulnerable to metabolic NAD+ depletion via nicotinamide phosphoribosyltransferase (NAMPT) inhibitors and temozolomide (TMZ) treatment. Here, we show that blockade of Cx43 with α-connexin carboxyl-terminal (ACT1) is able to inhibit growth of patient-derived IDH1-mutant tumor cells. ACT1 sensitizes cells to TMZ and inhibits growth of IDH1-mutant gliomas via an NAD-dependent mechanism. We also found that ACT1 can be used in combination with other NAD-depleting drugs, such as NAMPT inhibitors, to enhance its effect and provide a viable therapeutic window. Overall, our results suggest that ACT1 may enhance the efficacy of treatments for IDH1-mutant tumors by blocking metabolic buffering through tumor cell gap junctions.

TAMI-20. POLY(ADP-RIBOSE) GLYCOHYDROLASE INHIBITION SEQUESTERS NAD+ TO POTENTIATE THE METABOLIC LETHALITY OF ALKYLATING CHEMOTHERAPY IN IDH MUTANT TUMOR CELLS

Mutations in IDH1 or IDH2 characterize the majority of diffuse infiltrative gliomas of younger adulthood. DNA alkylator chemotherapy has proven to be an effective treatment for IDH mutant glioma, yet recurrences remain frequent and improved treatments are needed. Upon exposure of cancer cells to DNA alkylating agents, poly(ADP-ribose) polymerases (PARPs) catalyze the transient oligomerization of nicotinamide adenine dinucleotide (NAD+) into poly-ADP-ribose (PAR) chain-assemblies, which stimulate the DNA damage response. Here, we find that, in IDH mutant glioma cells, alkylator-induced cytotoxicity is dramatically augmented by pharmacologic inhibition or genetic knockout of the PAR breakdown enzyme poly(ADP-ribose) glycohydrolase (PARG). Mechanistically, we show this augmentation is driven by a metabolic state pairing amplified alkylator-induced DNA damage with catastrophic depletion of NAD+. IDH mutant cancer cells have low basal levels of NAD+, rendering them vulnerable to prolonged NAD+ depletion. Either of two clinically-utilized monofunctional alkylators, procarbazine (PCZ) or temozolomide (TMZ), when exposed to multiple IDH mutant lines, activated PARP conversion of cellular NAD+ monomers into polymerized PAR. Subsequent PAR breakdown and recycling of NAD+ monomers was then halted by concomitant PARG inactivation, amplifying PARylation-mediated DNA damage signaling and critically depleting free NAD+, resulting in profound cytotoxicity. This effect was partially reversed by NAD+ rescue supplementation, confirming the key contribution of metabolic stress. Combined alkylator treatment and PARG inhibition in vivo maximized both NAD+ depletion and cytotoxicity in an endogenous IDH mutant cancer model. Thus, alkyating DNA damaging agents expose a metabolic liability in IDH mutant cancers, and subsequent targeted blockade of PAR breakdown and NAD+ metabolite recovery can exploit this vulnerability to provide genotype-specific therapeutic benefit.

Local Targeting of NAD+ Salvage Pathway Alters the Immune Tumor Microenvironment and Enhances Checkpoint Immunotherapy in Glioblastoma

The aggressive primary brain tumor glioblastoma (GBM) is characterized by aberrant metabolism that fuels its malignant phenotype. Diverse genetic subtypes of malignant glioma are sensitive to selective inhibition of the NAD⁺ salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT). However, the potential impact of NAD⁺ depletion on the brain tumor microenvironment has not been elaborated. In addition, systemic toxicity of NAMPT inhibition remains a significant concern. Here we show that microparticle-mediated intratumoral delivery of NAMPT inhibitor GMX1778 induces specific immunologic changes in the tumor microenvironment of murine GBM, characterized by upregulation of immune checkpoint PD-L1, recruitment of CD3⁺, CD4⁺, and CD8⁺ T cells, and reduction of M2-polarized immunosuppressive macrophages. NAD⁺ depletion and autophagy induced by NAMPT inhibitors mediated the upregulation of PD-L1 transcripts and cell surface protein levels in GBM cells. NAMPT inhibitor modulation of the tumor immune microenvironment was therefore combined with PD-1 checkpoint blockade in vivo, significantly increasing the survival of GBM-bearing animals. Thus, the therapeutic impacts of NAMPT inhibition extended beyond neoplastic cells, shaping surrounding immune effectors. Microparticle delivery and release of NAMPT inhibitor at the tumor site offers a safe and robust means to alter an immune tumor microenvironment that could potentiate checkpoint immunotherapy for glioblastoma. SIGNIFICANCE: Microparticle-mediated local inhibition of NAMPT modulates the tumor immune microenvironment and acts cooperatively with anti-PD-1 checkpoint blockade, offering a combination immunotherapy strategy for the treatment of GBM.

IDH-mutant gliomas harbor fewer regulatory T cells in humans and mice

The metabolic gene isocitrate dehydrogenase 1 (IDH1) is commonly mutated in lower grade glioma (LGG) and secondary glioblastoma (GBM). Regulatory T cells (Tregs) play a significant role in the suppression of antitumor immunity in human glioma. Given the importance of Tregs in the overall framework of designing immune-based therapies, a better understanding on their association with IDH mutational status remains of critical clinical importance. Using multispectral imaging analysis, we compared the incidence of Tregs in IDH-mutant and IDH wild-type glioma from patient tumor samples of LGG. An orthotopic IDH-mutant murine model was generated to evaluate the role of mutant IDH on Treg infiltration by immunohistochemistry. When compared to IDH wild-type controls, Tregs are disproportionally underrepresented in mutant disease, even when taken as a proportion of all infiltrating T cells. Our findings suggest that therapeutic agents targeting Tregs may be more appropriate in modulating the immune response to wild-type disease.

Poly(ADP-ribose) Glycohydrolase Inhibition Sequesters NAD+ to Potentiate the Metabolic Lethality of Alkylating Chemotherapy in IDH-Mutant Tumor Cells

NAD⁺ is an essential cofactor metabolite and is the currency of metabolic transactions critical for cell survival. Depending on tissue context and genotype, cancer cells have unique dependencies on NAD⁺ metabolic pathways. PARPs catalyze oligomerization of NAD⁺ monomers into PAR chains during cellular response to alkylating chemotherapeutics, including procarbazine or temozolomide. Here we find that, in endogenous IDH1-mutant tumor models, alkylator-induced cytotoxicity is markedly augmented by pharmacologic inhibition or genetic knockout of the PAR breakdown enzyme PAR glycohydrolase (PARG). Both in vitro and in vivo, we observe that concurrent alkylator and PARG inhibition depletes freely available NAD⁺ by preventing PAR breakdown, resulting in NAD⁺ sequestration and collapse of metabolic homeostasis. This effect reversed with NAD⁺ rescue supplementation, confirming the mechanistic basis of cytotoxicity. Thus, alkylating chemotherapy exposes a genotype-specific metabolic weakness in tumor cells that can be exploited by PARG inactivation. SIGNIFICANCE: Oncogenic mutations in the isocitrate dehydrogenase genes IDH1 or IDH2 initiate diffuse gliomas of younger adulthood. Strategies to maximize the effectiveness of chemotherapy in these tumors are needed. We discover alkylating chemotherapy and concurrent PARG inhibition exploits an intrinsic metabolic weakness within these cancer cells to provide genotype-specific benefit.See related commentary by Pirozzi and Yan, p. 1629.This article is highlighted in the In This Issue feature, p. 1611.

Intraoperative 3-T Magnetic Resonance Spectroscopy for Detection of Proliferative Remnants of Glioma

BACKGROUND

Few studies have examined the usefulness of intraoperative magnetic resonance spectroscopy (iMRS) for identifying abnormal signals at the resection margin during glioma surgery. The aim of this study was to assess the value of iMRS for detecting proliferative remnants of glioma at the resection margin.

METHODS

Fifteen patients with newly diagnosed glioma underwent single-voxel 3-T iMRS concurrently with intraoperative magnetic resonance imaging-assisted surgery. Volumes of interest (VOIs) were placed at T2-hyperintense or contrast-enhancing lesions at the resection margin. In addition to technical verification, the correlation between the MIB-1 labeling index (a pathologic feature) and metabolites measured using iMRS (N-acetyl-L-aspartate [NAA], choline [Cho], and Cho/NAA ratio) was analyzed.

RESULTS

iMRS was performed for 20 VOIs in 15 patients. Fourteen (70%) of these VOIs were confirmed to be MIB-1-positive. There was a significant positive correlation between the Cho/NAA ratio and MIB-1 index (r = 0.46, P = 0.04). Cho level (P = 0.003) and Cho/NAA ratio (P = 0.002) were significantly higher in VOIs that were MIB-1-positive than in those that were MIB-1-negative. Detection of a Cho level >1.074 mM and a Cho/NAA ratio >0.48 using iMRS resulted in high diagnostic accuracy for MIB-1-positive remnants (Cho level: sensitivity 86%, specificity 100%; Cho/NAA ratio: sensitivity 79%, specificity 100%).

CONCLUSIONS

This study provides evidence that 3-T iMRS can detect proliferative remnants of glioma at the resection margin using the Cho level and Cho/NAA ratio, suggesting that intraoperative magnetic resonance imaging-assisted surgery with iMRS would be practicable in glioma.

Restoration of Temozolomide Sensitivity by PARP Inhibitors in Mismatch Repair Deficient Glioblastoma is Independent of Base Excision Repair

PURPOSE

Emergence of mismatch repair (MMR) deficiency is a frequent mechanism of acquired resistance to the alkylating chemotherapeutic temozolomide (TMZ) in gliomas. Poly(ADP-ribose) polymerase inhibitors (PARPi) have been shown to potentiate TMZ cytotoxicity in several cancer types, including gliomas. We tested whether PARP inhibition could re-sensitize MSH6-null MMR-deficient gliomas to TMZ, and assessed the role of the base excision repair (BER) DNA damage repair pathway in PARPi-mediated effects.

EXPERIMENTAL DESIGN

Isogenic pairs of MSH6 wild-type and MSH6-inactivated human glioblastoma (GBM) cells (including both IDH1/2 wild-type and IDH1 mutant), as well as MSH6-null cells derived from a patient with recurrent GBM were treated with TMZ, the PARPi veliparib or olaparib, and combination thereof. Efficacy of PARPi combined with TMZ was assessed in vivo. We used genetic and pharmacological approaches to dissect the contribution of BER.

RESULTS

While having no detectable effect in MSH6 wild-type GBMs, PARPi selectively restored TMZ sensitivity in MSH6-deficient GBM cells. This genotype-specific restoration of activity translated in vivo, where combination treatment of veliparib and TMZ showed potent suppression of tumor growth of MSH6-inactivated orthotopic xenografts, compared with TMZ monotherapy. Unlike PARPi, genetic and pharmacological blockage of BER pathway did not re-sensitize MSH6-inactivated GBM cells to TMZ. Similarly, CRISPR PARP1 knockout did not re-sensitize MSH6-inactivated GBM cells to TMZ.

CONCLUSIONS

PARPi restoration of TMZ chemosensitivity in MSH6-inactivated glioma represents a promising strategy to overcome acquired chemoresistance caused by MMR deficiency. Mechanistically, this PARPi-mediated synthetic phenotype was independent of BER blockage and was not recapitulated by loss of PARP1.

SPDR-05 PARP INHIBITORS RESTORE TEMOZOLOMIDE SENSITIVITY IN MSH6-DEFICIENT TEMOZOLOMIDE-RESISTANT GLIOBLASTOMA CELLS

INTRODUCTION

Mismatch repair (MMR) deficiency through MSH6 inactivation has been identified in approximately 25% of recurrent gliomas. This MMR deficiency represents a key molecular mechanism of acquired resistance to the alkylating chemotherapeutic agent temozolomide (TMZ). Potentiation of TMZ-induced cytotoxicity by PARP inhibitors (PARPi) has been reported in several cancers including gliomas. However, mechanisms that underlie the PARPi-mediated chemo-potentiation and biomarkers that predict benefit from this combination treatment have not been identified in gliomas. We investigated whether PARPis could restore TMZ sensitivity of MSH6-deficient chemoresistant gliomas and assessed the role of the base excision repair (BER) DNA damage repair pathway in PARPi-mediated effects.

METHODS

We engineered glioblastoma cell lines and patient-derived glioblastoma neurosphere lines to knockdown MSH6 expression, resulting in acquired MMR-deficient resistance to TMZ. We treated these isogenic pairs of MSH6 wild type and MSH6-inactivated cells with TMZ, PARPi Veriparib or Olaparib, and combination. Using MSH6-deficient glioma xenografts, we tested the in vivo efficacy of veliparib in combination with TMZ. We used genetic and pharmacological approaches to assess the role of BER pathway in PARPi-mediated effects.

RESULTS

We found that combination with PARPi restored TMZ sensitivity in MSH6-inactivated TMZ resistant cells whereas only subtle combination effects were seen in control MMR-proficient cells at the same PARPi concentrations. In vivo, combination treatment of TMZ with Veliparib demonstrated potent suppression of tumor growth of MSH6-inactivated orthotopic and flank xenografts, compared with TMZ monotherapy. Unlike PARPi, genetic and pharmacological blockage of BER pathway did not re-sensitize MSH6-inactivated cells to TMZ.

CONCLUSION

PARPis restore TMZ sensitivity in MSH6-deficient glioblastoma cells. This combination treatment is a promising strategy to target acquired chemoresistance caused by MMR deficiency.

DWI for Monitoring the Acute Response of Malignant Gliomas to Photodynamic Therapy

BACKGROUND AND PURPOSE

Photodynamic therapy is a novel treatment that provides effective local control, but little is known about photodynamic therapy-induced changes on MR imaging. The aim of this study was to assess the utility of DWI and ADC in monitoring the response of malignant gliomas to photodynamic therapy.

MATERIALS AND METHODS

Time-dependent changes in DWI and ADC values after photodynamic therapy were analyzed in a group that received photodynamic therapy in comparison with a group that did not.

RESULTS

Twenty-four patients were enrolled (photodynamic therapy, n = 14; non-photodynamic therapy, n = 10). In all patients who received photodynamic therapy, linear high signals on DWI in the irradiated area were detected adjacent to the resection cavity and were 5-7 mm in depth from 1 day posttreatment and disappeared in about 30 days without any neurologic deterioration. The non-photodynamic therapy group did not show this change. The photodynamic therapy group had significantly lower ADC values from 1 day posttreatment (P < .001), which increased steadily and disappeared by 30 days. There was no decline or time-dependent change in ADC values in the non-photodynamic therapy group.

CONCLUSIONS

The acute response of malignant gliomas to photodynamic therapy was detected as linear high signals on DWI and as a decrease in ADC values. These findings were asymptomatic and transient. Although the photodynamic therapy-induced acute response on MR imaging disappeared after approximately 30 days, it may be helpful for confirming the photodynamic therapy-irradiated area.

DRES-05. PREDICTORS OF SENSITIVITY TO COMBINED TEMOZOLOMIDE AND PARP INHIBITOR IN GLIOMA

Agents targeting the PARP enzyme family are under active development for the treatment of gliomas. PARP inhibitors (PARPi) can enhance the effect of temozolomide (TMZ) in IDH wild-type glioblastomas, and in addition recent studies have shown that PARP inhibitors can be selectively lethal in IDH1 mutant cancers. Here, we sought to identify predictors of sensitivity and resistance to PARP inhibition in gliomas. We treated 4 IDH1 mutant and 8 IDH wild-type glioma lines, as well as IDH1 mutant fibrosarcoma line HT1080, with TMZ, the PARPi olaparib, or the combination, and assessed cellular growth and survival. In dose response assessments, 7 out of 13 lines were sensitive to olaparib monotherapy (3 IDH1 mutant and 4 IDH wild-type). Combination with TMZ resulted in 6 of 13 lines responding to dual therapy, with an additive effect seen in 5 PARPi monotherapy sensitive gliomas. Notably, 5 of the 6 lines responsive to the combination harbored CDKN2A deletion, compared to none of the non-responsive lines (p=.0021). Treatment with CDK inhibitor palbociclib partially reversed sensitivity to TMZ+PARPi in HT1080, supporting a mechanistic basis for this association. PARPi sensitivity in glioma lines can be augmented by the addition of TMZ. CDKN2A deletion may serve as a potential biomarker identifying tumors sensitive to this combination therapy.

CBMT-47. MODULATION OF NAD PATHWAYS AS A THERAPEUTIC STRATEGY FOR TARGETING IDH MUTANT GLIOMA

BACKGROUND

IDH mutant tumors exhibit an altered metabolic state which may be exploited for use as a novel therapeutic approach. Our previous work has shown the IDH mutant cancer survival is dependent on the biosynthetic enzyme, nicotinamide phosphoribosyltransferase (NAMPT), for the production of nicotinamide adenine (NAD). Inhibition of NAMPT activity (NAMPTi) efficiently targets IDH mutant cells. NAD steady-state is also influenced by consumptive processes that utilize NAD as a coenzyme, including Sirtuin (SIRT) signaling. To avoid concerns surrounding NAMPT inhibitor toxicity at high doses, we sought to investigate whether modulation of SIRT activity can effectively target IDH mutant cells.

METHODS

IDH1 mutant cancer cells and patient-derived glioma lines were engineered for loss of SIRT gene expression using CRISPR/Cas9 gene editing or SIRT1 overexpression using a tetracycline-inducible expression system. The effect of silenced or enhanced SIRT1 activity was then assessed in IDH1 mutant cells alone or in combination with NAMPT inhibitors.

RESULTS

Loss of SIRT1 expression, but not other SIRT family members, confers resistance to NAMPT inhibition in IDH1 mutant cells. Consistent with the hypothesis that SIRT1 is a major consumer of NAD, we observed a significantly smaller decline in NAD when SIRT1 is deleted. In agreement with these findings, when SIRT1 activity is enhanced from baseline by tetracycline-mediated induction of SIRT1 expression, IDH mutant cell growth is slowed. Further, overexpression of SIRT1 leads to decreased cell viability and enhanced NAD depletion when induced in combination with NAMPTi.

CONCLUSIONS

IDH mutant tumors are vulnerable to NAD depletion. Our results show that this metabolic liability can be targeted by a combination of enhanced NAD consumption via SIRT1 activation and inhibition of NAD synthesis. Importantly, compounds to enhance SIRT1 activity are relatively non-toxic and in development for aging and neurologic disease, allowing potential for rapid translation to an IDH mutant-directed treatment.

NIMG-14. THE RELATION BETWEEN T2-FLAIR MISMATCH SIGN AND ADC VALUES REFLECTING PATHOLOGICAL MICROSTRUCTURE IN LOWER-GRADE GLIOMAS

BACKGROUND

Although the recent studies have identified “T2-FLAIR mismatch sign” specific to IDH-mutant and 1p/19q-intact gliomas, it is unclear what the mismatch sign represents. We aimed to investigate the mechanisms and validate the clinical utility.

METHODS

We identified 79 lower-grade gliomas treated at Kobe University Hospital, and classified into three groups: (i) LGGIDH(m),1p19q(-) (n = 18): IDH-mutant and 1p/19q-intact, (ii) LGGIDH(m),1p19q(+) (n=26): IDH-mutant and 1p/19q co-deleted, (iii) LGGIDH(w) (n=35): IDH wild-type. We retrospectively analyzed the relation with apparent diffusion coefficient (ADC) values, metabolites in magnetic resonance spectroscopy and pathological features, and examined the influence of the presence of the mismatch sign on progression-free survival (PFS) and overall survival in LGGIDH(m),1p19q(-).

RESULTS

Compared to the rim presenting hyperintense on T2WI and FLAIR, the core presenting hyperintense on T2WI and reversely hypointense on FLAIR had significantly higher ADC values (p = 0.002). The core/rim ratios of ADC values were significantly higher in the cases with the mismatch sign (p = 0.001), not depending on IDH status, 1p/19q status and WHO grade. There was no significant difference in metabolites changing between the presence and absence of the mismatch sign. The cases with the mismatch sign in LGGIDH(m),1p19q(-) had abundant microcysts as a pathological feature, and longer PFS than those without the mismatch sign (5-yr PFS: 100% vs 37.5%). Multivariate analysis found the mismatch sign to be the only significant predictor for preferable PFS in LGGIDH(m),1p19q(-) (p = 0.044).

CONCLUSION

Our study provided the new evidence that the T2-FLAIR mismatch sign had the significantly different ADC values between the core and the rim, suggesting that the mismatch sign reflected the difference of the tumor cellularity and the microenvironment.

Tumor-associated macrophage related interleukin-6 in cerebrospinal fluid as a prognostic marker for glioblastoma

Interleukin-6 (IL-6) is one of the pleiotropic cytokines and has received attention as a critical factor implicated in the invasion and the angiogenesis of various cancers. In glioma, IL-6 is known to be associated with the prognosis; however, the roles of IL-6 in cerebrospinal fluid (CSF) has not been studied sufficiently. We examined the concentration of CSF IL-6 using 75 CSF samples of glioma (54 glioblastomas (GBMs) and 21 other grades of gliomas) and analyzed the association CSF IL-6 with infiltration levels of tumor-associated macrophages (TAMs) and prognosis. The concentration of CSF IL-6 in GBM patients was significantly higher than that in other grades of gliomas. CSF IL-6 levels were associated with the infiltration rate of TAMs in GBMs, and IL-6 levels were increased in the GBM cells co-cultured with TAM-like macrophages. The CSF of GBM patients, which contained high concentration of IL-6, promoted the migration ability of GBM cells, and neutralization antibodies of IL-6 inhibited its migration ability. Finally, in both univariate and multivariate analysis, higher CSF IL-6 levels were associated with poorer prognosis in GBM patients. These results indicated that the concentration of CSF IL-6 is associated with TAMs' infiltration level and may be a useful prognostic biomarker for the GBM patients.

Medial lingual lymph node metastasis in carcinoma of the tongue

Lingual lymph node metastases are rarely seen in carcinoma of the tongue, and these nodes are not removed during neck dissection. Lingual lymph nodes are classified into medial and lateral groups, and metastasis to the former is extremely rare. A 55-year-old male with squamous cell carcinoma of the tongue, (stage T4aN0M0), underwent hemiglossectomy with neck dissection and free flap reconstruction. The lingual septum had a mass, 8 mm in size, which was diagnosed as medial lingual lymph node metastasis on histopathology. The patient developed multiple distant metastases and died of disease 18 months after the initial surgery. The presence of medial lymph node metastasis could result in contralateral neck metastases and worsen prognosis. Such cases may warrant more intensive therapy than recommended by current guidelines.

MicroRNA regulating stanniocalcin-1 is a metastasis and dissemination promoting factor in glioblastoma

BACKGROUND

MicroRNAs (miRs) regulate many biological processes, such as invasion, angiogenesis, and metastasis. Glioblastoma (GBM) patients with metastasis/metastatic dissemination have a very poor prognosis; therefore, inhibiting metastasis/metastatic dissemination has become an important therapeutic strategy for GBM treatment.

METHODS

Using 76 GBM tissues, we examined the expression levels of 23 GBM-related miRs and compared the miRs' expression levels between GBMs with metastasis/metastatic dissemination and GBMs without metastasis/metastatic dissemination. Using the bioinformatics web site, we searched the target genes of miRs. To analyze the function of target gene, several biological assays and survival analysis by the Kaplan-Meier method were performed.

RESULTS

We found that eight miRs were significantly decreased in GBM with metastasis/metastatic dissemination. By the bioinformatics analysis, we identified stanniocalcin-1 (STC1) as the most probable target gene against the combination of these miRs. Four miRs (miR-29B, miR-34a, miR-101, and miR-137) have predictive binding sites in STC1 mRNA, and mRNA expression of STC1 was downregulated by mimics of these miRs. Also, mimics of these miRs and knockdown of STC1 by siRNA suppressed invasion in GBM cells. GBM with metastasis/metastatic dissemination had significantly higher levels of STC1 than GBM without metastasis/metastatic dissemination. Finally, Kaplan-Meier analysis demonstrated that GBMs with high STC1 level had significantly shorter survival than GBMs with low STC1 level.

CONCLUSIONS

STC1 may be a novel metastasis/metastatic dissemination promoting factor regulated by several miRs in GBM. Because STC1 is a secreted glycoprotein and functions via the autocrine/paracrine signals, inhibiting STC1 signal may become a novel therapeutic strategy for GBM.

[Clinical Features and Treatment Strategy of Vertebral Artery Injury Associated with Cervical Spine Trauma]

OBJECTIVE

Vertebral artery injury(VAI)associated with cervical spine trauma has the potential to cause catastrophic vertebrobasilar stroke. However, there are no well-defined treatment recommendations for VAI. The purpose of this study was to identify an effective treatment strategy for VAI following cervical spine trauma.

METHODS

Ninety-seven patients with blunt cervical spine trauma were treated at Hyogo Prefectural Kakogawa Medical Center between January 2013 and September 2017. Of these patients, 49 underwent computed tomographic angiography or magnetic resonance angiography for evaluation of the vertebral artery. Eighteen patients(36.7%)had a diagnosis of VAI. We retrospectively analyzed the clinical features, treatment, and outcomes in these 18 patients.

RESULTS

Seven patients(38.9%)had bilateral VAI, 16(88.9%)had cervical dislocation, and 2(11.1%)had transverse process fractures extending into the transverse foramen. Surgical reduction was performed in 14 patients. Five patients with either bilateral or unilateral occlusion underwent parent artery occlusion before reduction. There were no complications after this procedure. Two patients with bilateral VAI had a stroke before treatment. There were no infarctions in the distribution of the vertebrobasilar artery after intervention. The perioperative stroke rate was relatively good, and almost all Glasgow Outcome Scale scores were related to the degree of spinal cord injury.

CONCLUSIONS

Aggressive screening for VAI is important in patients with cervical spine trauma in order to ensure adequate treatment. Although the treatment strategy described here could yield good results, it may require modification according to the needs of the individual patient.

Pentose phosphate pathway activation via HSP27 phosphorylation by ATM kinase: A putative endogenous antioxidant defense mechanism during cerebral ischemia-reperfusion

Molecular mechanism underlying ischemic stroke remains poorly understood. We previously reported glucose 6-phosphate dehydrogenase (G6PD) activity in pentose phosphate pathway (PPP) is activated via heat shock protein 27 (HSP27) phosphorylation at serine 85 (S85) by ataxia telangiectasia mutated (ATM) kinase during cerebral ischemia. This mechanism seems to be endogenous antioxidative system. To determine whether this system also works during reperfusion, we performed comparative metabolic analysis of reperfusion effect on metabolism in rat cortex using middle cerebral artery occlusion (MCAO). Metabolic profiling using gas-chromatography/mass-spectrometry analysis showed changes in metabolic state that depended on reperfusion time. Enrichment analysis showed PPP was significantly upregulated during ischemia-reperfusion. Significant increases in fructose 6-phosphate and ribulose 5-phosphate after reperfusion also suggested enhancement of PPP. In relation to PPP, ischemia-reperfusion induced an increase of up to 69-fold in HSP27 transcripts after 24-h reperfusion. Immunoblotting showed gradual increase in HSP27 protein and marked increase in HSP27 phosphorylation (S85) that were time-dependent (4.5-fold after 24-h reperfusion). G6PD activity was significantly elevated after 1-h MCAO (20%), reduced after 1-h reperfusion, increased gradually thereafter and significantly elevated after 24-h reperfusion. The NADPH/NAD⁺ ratio displayed similar increasing pattern. Intracerebroventricular injection of ATM kinase inhibitor (KU-55933) significantly reduced HSP27 phosphorylation and G6PD activity, significantly increased protein carbonyl, and resulted in increase in infarct size (100%) 24-h after reperfusion following 90-min MCAO. Consequently, G6PD activation via HSP27 phosphorylation by ATM kinase may be part of endogenous antioxidant defense neuroprotection mechanism that is activated during ischemia-reperfusion. These findings have important implications for treatment of stroke.

A molecular dynamics study of nuclear quantum effect on diffusivity of hydrogen molecule

In this paper, the nuclear quantum effect of the hydrogen molecule on its diffusivity was analyzed using the molecular dynamics (MD) method. The centroid MD (CMD) method was applied to reproduce the time evolution of the molecules. The diffusion coefficient of hydrogen was calculated using the Green-Kubo method over a wide temperature region, and the temperature dependence of the quantum effect of the hydrogen molecule on its diffusivity was addressed. The calculated results were compared with classical MD results based on the principle of corresponding state (PCS). It was confirmed that the difference in the diffusion coefficient calculated in the CMD and classical MD methods was small, and the PCS appears to be satisfied on the temperature dependence of the diffusion coefficient, even though the quantum effect of the hydrogen molecules was taken into account. It was clarified that this result did not suggest that the quantum effect on the diffusivity of the hydrogen molecule was small but that the two changes in the intermolecular interaction of hydrogen due to the quantum effect offset each other. Moreover, it was found that this tendency was related to the temperature dependence of the ratio of the kinetic energy of the quantum fluctuational motion to the classical kinetic energy.

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma with squamous differentiation: a novel histological finding

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (TL-LGNPPA) is an extremely rare neoplasm originating from the nasopharyngeal surface epithelium. Histopathologically, TL-LGNPPA is characterized by cuboidal/columnar tumor cells forming papillary fronds and thyroid transcription factor-1 (TTF-1) expression resembling papillary thyroid carcinoma. To date, the recorded histological features of TL-LGNPPA have been almost uniform, and the range of histological variations in this tumor type has not been sufficiently understood. Here, we report on a 68-year-old man with TL-LGNPPA. Microscopic examination of the resected tumor revealed findings typical of papillary adenocarcinoma of this type, and moreover, this case showed scattered squamous cell foci as a hitherto unreported finding. The squamous cells showed no obvious nuclear atypia or proliferating activity, and their presence was similar to the "squamous metaplasia" of papillary thyroid carcinoma. Immunohistochemically, p40 and TTF-1 coexpression was observed in the squamous cell nuclei, indicating their origin from the glandular tumor cells of TL-LGNPPA.

Magnetic Resonance Spectroscopy Findings in Patients with Dural Arteriovenous Fistulas: Three Case Reports

BACKGROUND

Magnetic resonance spectroscopy (MRS) is a potentially useful modality for evaluating brain metabolites in patients with dural arteriovenous fistula (dAVF). Here we describe a different pattern of MRS-based cerebral metabolism findings in patients with dAVF.

CASE DESCRIPTIONS

We performed MRS in 3 patients with transverse sigmoid sinus dAVF associated with cortical venous reflux. In case 1, which was associated with vasogenic edema on T2-weighted magnetic resonance imaging (MRI), decreased preoperative N-acetylaspartate (NAA)/creatine (Cr) and myo-inositol (mIns)/Cr and increased lactate (Lac)/Cr ratios improved after treatment. In case 2, a decreased preoperative NAA/Cr ratio improved after treatment. These 2 patients presented with seizures. In case 3, the patient presented with headache and showed no metabolic changes on preoperative or postoperative MRS.

CONCLUSIONS

Our results suggest that patients with dAVF can be classified based on a combination of metabolic and signal changes seen on T2-weighted MRI. MRS may allow significantly expanded evaluation of the metabolic changes associated with dAVF for appropriate classification and management.