IDH-mutant Tumors Research Articles

PATH-14. GENETIC SUSCEPTIBILITY AND OUTCOMES OF PEDIATRIC, ADOLESCENT AND YOUNG ADULT IDH-MUTANT ASTROCYTOMAS

INTRODUCTIONPreviously thought to be rare, recent case series have shown that IDH mutations in young patients are more common than previously described. In this study, we analyzed IDH-mutant tumors to determine clinical significance of these mutations in children, adolescents and young adults.METHODSThrough this multi-institution study (10 institutions), we collected 64 IDH1/2-mutant infiltrating astrocytoma specimens from 58 patients aged 4–26 (M:F, 0.4:0.6). Specimens included 46 low-grade (LGG) and 18 high-grade (HGG) astrocytomas. Tumor sequencing data (n=45), germline sequencing data (n=37) and outcome data (n=40) was analyzed.RESULTSSimilar to adults, most sequenced tumors had a co-mutation in the TP53 gene, while ATRX mutations were less common and primarily seen in HGGs. Approximately 60% (n=21) of patients with germline data available had a mutation in a cancer predisposition gene. Mismatch repair (MMR) mutations were most common (n=12; MSH6 n=9), followed by TP53mutations (n=7). All patients with MMR gene mutations had HGGs and poor progression free (PFS=10% at 2 years, mean TTP=9 months) and overall (OS <30% at 2 years) survival. Despite an OS of 90% at 5 years, many LGG patients had tumor progression/recurrence requiring additional treatment (PFS= 80% at 2 yrs, 40% at 5 yrs, mean TTP=3.5 years). Four LGG tumors (2 with TP53+ATRXloss, 2 with TP53 loss+1p19q co-deletion) underwent malignant transformation.CONCLUSION IDH-mutant tumors in pediatric patients are strongly associated with cancer predisposition and increased risk for progression/recurrence or malignant transformation. Routine screening for IDH1/2 mutations in children with grade 2–4 astrocytomas could greatly impact patient management.

Molecular Classification of Gliomas is Associated with Seizure Control: A Retrospective Analysis.

Classically, histologic grading of gliomas has been used to predict seizure association, with low-grade gliomas associated with an increased incidence of seizures compared to high-grade gliomas. In 2016, WHO reclassified gliomas based on histology and molecular characteristics. We sought to determine whether molecular classification of gliomas is associated with preoperative seizure presentation and/or post-operative seizure control across multiple glioma subtypes. All gliomas operated at our institution from 2007 to 2017 were identified based on ICD 9 and 10 billing codes and were retrospectively assessed for molecular classification of the IDH1 mutation, and 1p/19q codeletion. Logistic regression models were performed to assess associations of seizures at presentation as well as post-operative seizures with IDH status and the new WHO integrated classification. Our study included 376 patients: 82 IDH mutant and 294 IDH wildtype. The presence of IDH mutation was associated with seizures at presentation [OR 3.135 (1.818-5.404), p<0.001]. IDH-mutant glioblastomas presented with seizures less often than other IDH-mutant glioma subtypes grade II and III [OR 0.104 (0.032-0.340), p<0.001]. IDH-mutant tumors were associated with worse post-operative seizure outcomes, demonstrated by Engel Class [OR 2.666 (1.592-4.464), p<0.001]. IDH mutation in gliomas is associated with an increased risk of seizure development and worse post-operative seizure control, in all grades except for GBM.

NIMG-54. DIFFUSE TUMOR GROWTH PATTERN IS ASSOCIATED WITH WORSE OUTCOME ONLY IN IDH WILDTYPE BUT NOT IN IDH MUTANT GLIOMAS WHO II AND III

Abstract BACKGROUND Magnetic resonance imaging (MRI) based characterization has previously shown heterogeneity in tumor appearance according to IDH mutation status. We have recently investigated the relevance of contrast enhancement to be dependent on IDH mutation status in glioma WHO II and III. Here, we aimed at further characterizing tumor growth patterns and their prognostic value in these tumors. METHODS MRI and clinical data of patients with newly diagnosed glioma WHO II and III from two different centers were retrospectively reviewed. Radiological data such as localization, presence of contrast enhancement, T2-volume as well as tumor growth pattern (“diffuse” vs. “circumscript”) were obtained. Progression-free (PFS) and overall survival (OS) were determined and correlated with clinical, radiological and molecular characteristics using univariate and multivariate regression analyses. RESULTS 390 patients were included, 69% thereof having an IDH mutation. The median T2-volume was 46.0 ml, IDH mutant tumors being larger (50.7 ml) than IDH wildtype tumors (36.0 ml), p = 0.01. A total of 172 tumors were classified as “circumscript” and 218 as “diffuse”; the majority of IDH wildtype tumors (71%) were well delineated compared to 51% in the IDH mutant group (p&amp;lt; 0.0001). Apart from clinical parameters such as younger age, lower KPS, complete resection and delayed treatment, “circumscript” tumor growth pattern was associated with improved survival in the entire group (p = 0.016). When analyzed according to IDH mutation status, “circumscript” tumor growth pattern was significantly associated with OS and PFS (p = 0.006 and p = 0.002) in the IDH wildtype, but not in the IDH mutant group (p = 0.34 and p = 0.81). CONCLUSION IDH wildtype tumors present more often with a ”circumscript” growth pattern on initial T2 MRI. However, this “circumscript” growth pattern was associated with improved survival only in the IDH wiltdtype but not in the IDH mutant group.

EPCO-29. EPIGENOMICS OF THE GLIOMA LONGITUDINAL ANALYSIS (GLASS) CONSORTIUM

Abstract Adult diffuse gliomas are central nervous system (CNS) tumors that arise from the malignant transformation of glial cells. Nearly all gliomas will recur despite standard treatment however, current histopathological grading fails to predict which of them will relapse and/or progress. The Glioma Longitudinal AnalySiS (GLASS) consortium is a large-scale collaboration that aims to investigate the molecular profiling of matched primary and recurrent glioma samples from multiple institutions in order to better understand the dynamic evolution of these tumors. At this time, the cohort comprises 946 samples across 11 institutions and among those, 864 have DNA methylation data available. The current molecular classification based on 7 subtypes published by TCGA in 2016 was applied to the dataset. Among the IDH wildtype tumors, 33% (16/49) of the patients showed a change of subtype upon recurrence, whereas most of them (9/16) were Classic-like at the primary stage but changed to either Mesenchymal-like or PA-like at the recurrent level. Among the IDH mutant tumors, 15% (22/142) showed a change of subtype at recurrent stage, in which 16 out of 22 progressed from G-CIMP-high to G-CIMP-low. Although some tumors progressed to a different subtype upon recurrence, an unsupervised analysis showed that the samples tend to cluster by patient instead of by subtype. By estimating the copy number alterations of these tumors using DNA methylation, the overall copy number profile of the recurrent samples remains similar to their primary counterpart. From this initial analysis using epigenomic data, we were able to characterize some aspects of glioma evolution and how the DNA methylation is associated with the progression of these tumors to different subtypes. These findings corroborate the importance of epigenetics in gliomas and can potentially lead to the identification of new biomarkers that can reflect tumor burden and predict its development.

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

Abstract 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-07. THE IMMUNE MICROENVIRONMENT IN LOWER GRADE GLIOMAS

Abstract The determinants of the tumor-associated immune response in brain tumors are poorly understood. Using tumor samples from two molecularly distinct subtypes of lower grade glioma, MAPK-driven glioma with biallelic inactivation of CDKN2A (n=30) and IDH-mutant, 1p/19q-intact astrocytoma (n=29), we demonstrate qualitative and quantitative differences in the tumor-associated immune response and we investigate the molecular mechanisms involved. Histologically the MAPK-driven gliomas were comprised of pleomorphic xanthoastrocytoma (PXA) (n=11) and anaplastic PXA (n=19). Seven patients had paired samples from two sequential surgeries. Immune cell populations and their activity were determined by quantitative multiplex immunostaining and Digital Spatial Profiling and gene expression was analyzed by Nanostring. Functional studies were performed using established cell lines and two new patient-derived lines from MAPK-driven LGGs. MAPK-driven tumors exhibited an increased number of CD8+ T cells and tumor-associated microglial/macrophage (TAMs), including CD163+ TAMs, as compared to IDH-mutant astrocytoma. In contrast, IDH-mutant tumors had increased FOXP3+ immunosuppressive T regulatory cells. Transcriptional and protein level analyses in MAPK-driven tumors suggested an active cytotoxic T cell response with robust expression of granzyme B, present on 27% of CD8+ T cells, increased MHC class I expression, and altered cytokine profiles. Interestingly, MAPK-driven tumors also had increased expression of immunosuppressive molecules, including CXCR4, PD-L1, and VEGFA. Expression differences for cell surface and secreted proteins were confirmed in patient-derived tumor lines and functional relationships between altered chemokine expression and immune cell infiltration was investigated. Our data provide novel insights into the immune contexture of MAPK driven LGGs and suggest MAPK driven gliomas with biallelic inactivation of CDKN2A may be particularly vulnerable to immunotherapeutic modulation

NCMP-10. IDH MUTATION STATUS AND THE DEVELOPMENT OF VENOUS THROMBOEMBOLISM IN ASTROCYTOMA PATIENTS

Abstract OBJECTIVE Examine whether the status of the isocitrate dehydrogenase (IDH) gene is a risk factor for the development of venous thromboembolism (VTE) in astrocytoma patients. BACKGROUND The risk of venous thromboembolism (VTE) is high for patients with gliomas (10–30%). Unfortunately, biomarkers and predictive models for development of a VTE in brain cancer have not been validated. Prior research has suggested that IDH wildtype gliomas are at higher risk for development of VTE compared to IDH mutant tumors. DESIGN/METHODS We conducted a retrospective chart review of glioma patients enrolled in the PROACTIVE (Prospective Assessment of Correlative Biomarker) study at MD Anderson Cancer Center (MDACC). We obtained demographics, date of tumor diagnosis, initial pathology, IDH status (mutated or wildtype), extent of initial resection, KPS at time of initial resection, history of VTE, development of VTE, type of VTE (PE/DVT), KPS at time of VTE, treatment for VTE, bleeding complications, glioma treatments, date of last follow up and/or death. RESULTS We identified 282 astrocytoma patients consisting of 49 IDH mutant and 233 IDH wildtype astrocytomas. Glioblastoma was the histopathologic diagnosis in 30 (61.2%) of the IDH mutated astrocytomas compared to 227(97.4%) of the IDH wild type astrocytomas. VTE was identified in 52 (18.4%) of patients. VTE was diagnosed in 7 (14.3%) of the IDH mutated astrocytomas compared to 45 (19.3%) of the IDH wild type astrocytomas (p = 0.4094). Median time to VTE from diagnosis was 2.71 months. Median time to VTE from diagnosis was 2.6 months for IDH mutated astrocytomas compared to 3.06 months for the IDH wild type astrocytomas (p =0.8663). CONCLUSIONS IDH gene status did not appear as a significant risk factor for the development of venous thromboembolism (VTE) in our cohort of astrocytoma patients. Further research into potential biomarkers for VTE may be warranted.

NIMG-24. GLYCINE AND GLUTAMINE BY MR SPECTROSCOPY ARE IMAGING BIOMARKERS OF GLIOMA AGGRESSIVENESS

Abstract Cancers reprogram their metabolism and the resulting alterations in metabolite concentrations may be closely related to the clinical behavior of the tumors. We evaluated glycine, glutamine and 2-hydroxyglutarate (2HG) in 16 adult subjects with glioblastomas (9 male and 7 female; age 43-64 years, median 58) noninvasively using proton magnetic resonance spectroscopy and examined their association with the cell proliferation rate (MIB-1 labeling index) and overall survival. MRS was acquired using point-resolved spectroscopy (PRESS TE 97ms) at 3T. Metabolite levels were quantified with reference to water. The concentrations of glycine and glutamine were both positively correlated with MIB-1 (p=.002 and .0008 respectively). The sum of glycine and glutamine levels showed stronger association with MIB-1 (p&amp;lt; .0001). In the Kaplan-Meier overall survival analysis, the median survival was significantly shorter in patients with glycine levels higher than 2.3 mM than those with concentrations less than 2.3 mM. For glutamine, the patients with higher than 5.7 mM showed association with poor survival. The log-rank p value was substantially smaller in glutamine compared to glycine (p=.008 vs .04). The sum of glycine and glutamine levels showed stronger association with overall survival. 2HG level greater than 1 mM was associated with long survival, which was as expected since elevation of 2HG represents IDH mutant tumors and IDH mutation carries favorable prognosis. Given the association of low 2HG with poor survival, we tested metabolic ratios to 2HG, in which 2HG estimates &amp;lt; 1 mM were put as 1 mM. The glycine/2HG, glutamine/2HG, and (glycine+glutamine)/2HG showed stronger association with overall survival, compared to glycine, glutamine, and glycine+glutamine. Our data suggested that increased metabolism of glycine and glutamine is closely associated with rapid cell proliferation and poor clinical outcome, suggesting the metabolites as an MRS imaging biomarker of glioma aggressiveness.

NIMG-36. AUTOMATIC STRATIFICATION OF ENHANCING AND NON-ENHANCING GLIOMAS INTO GENETIC SUBTYPES USING DEEP NEURAL NETWORKS AND DIFFUSION-WEIGHTED IMAGING

Abstract INTRODUCTION Current WHO guidelines emphasize classification of diffuse gliomas by genetic alterations into three subgroups: 1) IDH-wildtype; 2) IDH-mutant, 1p/19q-codeleted; and 3) IDH-mutant, 1p/19q-non-codeleted. Non-invasive genetic characterization can benefit patients with inoperable lesions or who are administered molecularly-targeted therapy before surgery. Prior studies that use anatomical images and convolutional neural networks (CNNs) to distinguish either IDH-mutant from IDH-wildtype tumors, or 1p/19q-codeleted from non-codeleted tumors have resulted in misclassification of nonenhancing IDH-wildtype and enhancing IDH-mutant tumors. This study investigated the benefit of a priori separation of enhancing from nonenhancing lesions and the inclusion of ADC maps from diffusion MRI to genetic subgroup classification. METHODS 3D T2-weighted, T2-FLAIR, and post-contrast T1-weighted images were acquired preoperatively from 254 patients with newly-diagnosed gliomas. IDH1R132H mutations[VJ1] [CJ2], 1p19q-codeletions, ATRX alterations, and p53 mutations were assessed from the resected tissue to determine subtype stratification: IDH-wildtype (n=95), IDH-mutant, 1p/19q-codeleted (n=62), and IDH-mutant, non-codeleted (n=97). 3-channel input images were constructed for each patient using T2-FLAIR, T1-post-contrast, and either T2-weighted or ADC images. Three VGG-16 CNNs pre-trained on ImageNet were re-trained for: 1) lesions without enhancement, 2) enhancing lesions, and 3) all lesions together[VJ3]. RESULTS A network trained on only enhancing lesions predicted the IDH-wildtype subtype with the highest class accuracy (ADC 94%, T2-weighted 100%) compared to using all lesions combined (ADC 90%, T2-weighted 90%). Models trained using non-enhancing lesions and ADC yielded the highest accuracy classifying 1p/19q-codeleted/non-codeleted subgroups (87%/90% for the non-enhancing network vs 83%/81% for combined network). CONCLUSIONS Our results support a strategy that first considers whether a lesion is enhancing when predicting molecular subgroup and includes ADC if the lesion is non-enhancing. Analysis is underway to test this model framework on independent TCIA data.

EPID-11. A MULTI-INSTITUTIONAL COMPARATIVE ANALYSIS OF THE CLINICAL, GENOMIC, AND SURVIVAL CHARACTERISTICS OF PEDIATRIC, YOUNG ADULT AND OLDER ADULT PATIENTS WITH IDH-MUTANT GLIOMA

Abstract BACKGROUND Prognostic significance of IDH-mutation in glioma is incompletely understood in children and adolescents/young adults (YAs). We compared the clinico-genomic features, outcomes and prognostic factors observed in IDH-mutant gliomas across age groups. METHODS Clinical, histologic and molecular data of patients with IDH-mutant gliomas from 8 pediatric institutions (spanning twenty years) and adult patients from two institutions (from 2013–2019) were identified. Patients were grouped as pediatric (&amp;lt; 19y), YA (19y to &amp;lt; 40y) or older adult (≥ 40y). Genomic alterations, including somatic mutations and copy number variants, were captured with institutional next generation sequencing. Factors were compared across age categories using Fisher’s exact test or analysis-of-variance. Cox proportional-hazards regression tested factors for association with overall (OS) and progression-free survival (PFS). RESULTS Of 379 patients, 48(13%) were pediatric, 204(54%) YA and 127(33%) older adult. Histological subtype differed significantly by age group (p&amp;lt; 0.0001). YAs had higher rates of malignant transformation (p=0.01) and shorter time-from-diagnosis-to-malignant transformation (p=0.01) compared to other age groups. Analysis of genomic alterations revealed an age-related difference in distribution in ATRX mutations only (p=0.0018). Median PFS and OS for the entire cohort were 4.62 and 17.19 years. In univariate models, PFS differed by age group (p=0.0012), with YAs having the worst outcomes. Lack of MGMT methylation (p=0.024) predicted poorer OS. Upfront observant management was predictive of poorer PFS. Gene mutations were not associated with PFS. In multi-variable models, YAs had shorter PFS compared to pediatric (hazard ratio [HR]=2.03, p=0.01) and older adults (HR=1.59, p=0.003) after adjusting for histology, extent of resection, and initial therapy. Age at diagnosis was not associated with OS in multi-variable analysis. CONCLUSIONS Within our cohort, YA with IDH-mutant tumors progressed more quickly compared to their pediatric counterparts. Further study of YA patients with IDH-mutant glioma is critical to better define best practices for this group.

BIOM-18. TUMOR LOCATION IS ASSOCIATED WITH CDKN2A STATUS IN IDH-MUTANT ASTROCYTOMAS

Abstract BACKGROUND Astrocytomas with isocitrate dehydrogenase (IDH) mutations have a better prognosis and response to therapy than matching tumors without IDH mutations. IDH-mutant tumors of any grade or histology that carry homozygous deletions in cyclin-dependent kinase inhibitor (CDKN2A) have a worse prognosis compared to tumors with intact CDKN2A. Within a retrospective cohort of IDH-mutant astrocytomas with known CDKN2A status, we examined whether there was any correlation of CDKN2A status with anatomic location. METHODS Astrocytomas of any grade carrying IDH mutations with further molecular sequencing that included CDKN2A status were identified from a tissue database, as well as a clinical cohort of patients seen at the neuro-oncology clinic who had genomic analysis by clinical request. Imaging was reviewed for tumor location. Fisher’s exact test was used to analyze differences between groups. RESULTS Six of 35 IDH-mutant astrocytomas (17%) had CDKN2A deletions. None of the six patients with CDKN2A mutant tumors had contact with the insula, whereas 16 of 29 tumors (55%) with intact CDKN2A contacted the insula (p=0.02). The majority of tumors in both groups were located completely or partially in the frontal lobe, as is common in IDH-mutant astrocytomas, and all CDKN2A deleted tumors were in the frontal lobe. DISCUSSION Astrocytomas with IDH mutations that also carry CDKN2A deletions have been shown to have a worse prognosis than similar grade tumors with intact CDKN2A status. This has important prognostic implications, but CDKN2A testing is not standard currently or used to stratify patients in clinical trials. Our sample size is small, but if confirmed in a larger cohort could help guide efficient testing for CDKN2A status and improve prognostication.

Linking epigenetic signature and metabolic phenotype in IDH mutant and IDH wildtype diffuse glioma.

Changes in metabolism are known to contribute to tumour phenotypes. If and how metabolic alterations in brain tumours contribute to patient outcome is still poorly understood. Epigenetics impact metabolism and mitochondrial function. The aim of this study is a characterisation of metabolic features in molecular subgroups of isocitrate dehydrogenase mutant (IDHmut) and isocitrate dehydrogenase wildtype (IDHwt) gliomas. We employed DNA methylation pattern analyses with a special focus on metabolic genes, large-scale metabolism panel immunohistochemistry (IHC), qPCR-based determination of mitochondrial DNA copy number and immune cell content using IHC and deconvolution of DNA methylation data. We analysed molecularly characterised gliomas (n=57) for in depth DNA methylation, a cohort of primary and recurrent gliomas (n=22) for mitochondrial copy number and validated these results in a large glioma cohort (n=293). Finally, we investigated the potential of metabolic markers in Bevacizumab (Bev)-treated gliomas (n=29). DNA methylation patterns of metabolic genes successfully distinguished the molecular subtypes of IDHmut and IDHwt gliomas. Promoter methylation of lactate dehydrogenase A negatively correlated with protein expression and was associated with IDHmut gliomas. Mitochondrial DNA copy number was increased in IDHmut tumours and did not change in recurrent tumours. Hierarchical clustering based on metabolism panel IHC revealed distinct subclasses of IDHmut and IDHwt gliomas with an impact on patient outcome. Further quantification of these markers allowed for the prediction of survival under anti-angiogenic therapy. A mitochondrial signature was associated with increased survival in all analyses, which could indicate tumour subgroups with specific metabolic vulnerabilities.

Pharmacotranscriptomic Analysis Reveals Novel Drugs and Gene Networks Regulating Ferroptosis in Cancer.

Simple SummaryFerroptosis is increasingly recognized as a promising avenue for cancer therapy, while the biomarkers that predict the sensitivity and/or resistance of ferroptosis and the molecular mechanisms that can be therapeutically exploited to modulate ferroptosis are not yet known. Here, we perform an integrated pharmacotranscriptomic analysis to systematically identify compounds and gene networks that regulate ferroptosis. Our results provide mechanistic insights into the deregulation of ferroptosis in cancer and suggest new approaches for ferroptosis-based cancer therapy.(1) Background: Ferroptosis is an apoptosis-independent cell death program implicated in many diseases including cancer. Emerging evidence suggests ferroptosis as a promising avenue for cancer therapy, but the paucity of mechanistic understanding of ferroptosis regulation and lack of biomarkers for sensitivity to ferroptosis inducers have significantly hampered the utility of ferroptosis-based therapy. (2) Methods: We performed integrated dataset analysis by correlating the sensitivity of small-molecule compounds (n = 481) against the transcriptomes of solid cancer cell lines (n = 659) to identify drug candidates with the potential to induce ferroptosis. Generalizable gene signatures of ferroptosis sensitivity and resistance are defined by interrogating drug effects of ferroptosis inducers (n = 7) with transcriptomic data of pan-solid cancer cells. (3) Results: We report, for the first time, the comprehensive identification of drug compounds that induce ferroptosis and the delineation of generalizable gene signatures of pro- and anti-ferroptosis in pan-cancer. We further reveal that small cell lung cancer (SCLC) and isocitrate dehydrogenase (IDH1/2)-mutant brain tumors show enrichment of pro-ferroptosis gene signature, suggesting a unique vulnerability of SCLC and IDH-mutant tumors to ferroptosis inducers. Finally, we demonstrate that targeting class I histone deacetylase (HDAC) significantly enhances ferroptotic cell death caused by Erastin, an ferroptosis inducer, in lung cancer cells, revealing a previously underappreciated role for HDAC in ferroptosis regulation. (4) Conclusions: Our work reveals novel drug compounds and gene networks that regulate ferroptosis in cancer, which sheds light on the mechanisms of ferroptosis and may facilitate biomarker-guided stratification for ferroptosis-based therapy.

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.

Association of supratotal resection with progression-free survival, malignant transformation, and overall survival in lower-grade gliomas.

Supratotal resection is advocated in lower-grade gliomas (LGGs) based on theoretical advantages but with limited verification of functional risk and data on oncological outcomes. We assessed the association of supratotal resection in molecularly defined LGGs with oncological outcomes. Included were 460 presumptive LGGs; 404 resected; 347 were LGGs, 319 isocitrate dehydrogenase (IDH)-mutated, 28 wildtype. All patients had clinical, imaging, and molecular data. Resection aimed at supratotal resection without any patient or tumor a priori selection. The association of extent of resection (EOR), categorized on volumetric fluid attenuated inversion recovery images as residual tumor volume, along with postsurgical management with progression-free survival (PFS), malignant (M)PFS, and overall survival (OS) assessed by univariate, multivariate, and propensity score analysis. The study mainly focused on IDH-mutated LGGs, the "typical LGGs." Median follow-up was 6.8 years (interquartile range, 5-8). Out of 319 IDH-mutated LGGs, 190 (59.6%) progressed, median PFS: 4.7 years (95% CI: 4-5.3). Total and supratotal resection obtained in 39% and 35% of patients with IDH1-mutated tumors. In IDH-mutated tumors, most patients in the partial/subtotal group progressed, 82.4% in total, only 6 (5.4%) in supratotal. Median PFS was 29 months (95% CI: 25-36) in subtotal, 46 months (95% CI: 38-48) in total, while at 92 months, PFS in supratotal was 94.0%. There was no association with molecular subtypes and grade. At random forest analysis, PFS strongly associated with EOR, radiotherapy, and previous treatment. In the propensity score analysis, EOR associated with PFS (hazard ratio, 0.03; 95% CI: 0.01-0.13). MPFS occurred in 32.1% of subtotal total groups; 1 event in supratotal. EOR, grade III, previous treatment correlated to MPFS. At random forest analysis, OS associated with EOR as well. Supratotal resection strongly associated with PFS, MPFS, and OS in LGGs, regardless of molecular subtypes and grade, right from the beginning of clinical presentation.

Vessel Size Imaging is Associated with IDH Mutation and Patient Survival in Diffuse Lower-Grade Glioma.

BackgroundPatients with isocitrate dehydrogenase (IDH) mutant gliomas have better survival and appear to be more sensitive to chemotherapy than their IDH wild-type counterparts. We attempted to assess the correlations of vessel size imaging (VSI) values with IDH mutation status and patient survival in diffuse lower-grade glioma (LGG).MethodsWe enrolled 60 patients with diffuse LGGs, among which 43 had IDH-mutant tumors. All patients underwent VSI examination and VSI values for active tumors were calculated. Receiver operating characteristic (ROC) curves were established to evaluate the detection efficiency. Logistic regression was employed to determine the ability of variables to discriminate IDH mutational status. Kaplan–Meier survival analysis and Cox proportional hazards models were utilized to estimate the correlations of VSI values and other risk factors with patient survival.ResultsWe observed that VSI values were lower in IDH-mutant LGGs than IDH wild-type LGGs. The VSImax and VSImean values had AUC values of 0.7305 and 0.7401, respectively, in distinguishing IDH-mutant LGGs from IDH wild-type LGGs. Logistic regression showed that VSImean values, age and tumor location were associated with IDH-mutant status, and the formula integrating the three factors had an AUC value of 0.7798 when distinguishing IDH-mutant LGGs from IDH wild-type LGGs. Moreover, LGG patients with high VSI values exhibited worse survival rates than those with low VSI values for both progression-free survival (PFS) and overall survival (OS). Multivariate Cox proportional hazards regression analysis suggested that IDH mutation status, VSImean values and multiple lesions or lobes were risk factors for PFS of LGG patients.ConclusionVSI value is associated with IDH genotype and maybe an independent predictor of the survival of patients with LGGs.

26 Poster Discussion - Poly(ADP-ribose) glycohydrolase inhibition sequesters NAD+ to potentiate the metabolic lethality of alkylating chemotherapy in IDH mutant tumor cells

Background: Mutations in IDH1 or IDH2 characterize the most prevalent diffuse glioma of younger adulthood. DNA alkylator chemotherapy is an effective treatment for IDH mutant glioma, yet recurrences remain common and improved treatments are needed. Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor metabolite, serving as the currency of metabolic transactions critical for cell survival. IDH mutant cancer cells have unique dependencies on NAD+-dependent metabolic pathways, which include poly(ADP-ribose) polymerases (PARPs). PARPs catalyze oligomerization of NAD+ monomers into poly(ADP-ribose) (PAR) chains during cellular response to alkylating chemotherapeutics such as temozolomide (TMZ). We hypothesized that we could exploit the intrinsic metabolic vulnerability of IDH mutant cancer cells with combined treatment: TMZ would promote PARP activation and outflow consumption of cellular NAD+ pools, while concomitant inactivation of the PAR breakdown enzyme poly(ADP-ribose) glycohydrolase (PARG) would then sequester NAD+ as polymerized PAR, by blocking subsequent breakdown.

Isocitrate Dehydrogenase, Patient-Reported Outcomes, and Cognitive Functioning of Glioma Patients: a Systematic Review

Isocitrate dehydrogenase (IDH) mutation status has important prognostic implications in glioma patients, with IDH wild-type (IDH-WT) gliomas being associated with worse prognosis and shorter survival when compared with IDH mutant (IDH-mut) gliomas. Optimization of quality of life is a priority in the management of glioma patients. The goal of this systematic review was to identify studies that explored the association of IDH mutation status with patient-reported outcomes (PROs) and cognitive functioning of glioma patients. Studies that evaluated the association of IDH mutation status with PROs and/or cognitive functioning of glioma patients were identified from the Pubmed/MEDLINE, Clarivate analytics, and Google Scholar databases. Eight studies (7 journal articles and 2 conference abstracts) with a total of 658 low-grade glioma and high-grade glioma patients investigated the association of cognitive functioning and/or QoL with IDH status. IDH-WT status was associated with greater cognitive impairment relative to IDH-Mut status in three studies, while one study did not find the association between IDH status and perioperative cognitive functioning. One study reported worse postoperative cognitive functioning patients with IDH-WT vs. IDH-mut gliomas. In one study, IDH-WT status was linked to greater impairment on physical and communication functioning after surgery. IDH-WT gliomas are associated with greater cognitive burden than IDH-Mut tumors. The association of IDH status with QoL remains less clear. Assessment of IDH status should be considered when evaluating QoL and cognitive complaints of glioma patients. Further studies linking glioma molecular phenotypes with PROs and cognitive functioning are encouraged.

Comparison of Genetic Profiles and Prognosis of High-Grade Gliomas Using Quantitative and Qualitative MRI Features: A Focus on G3 Gliomas.

ObjectiveTo evaluate the association of MRI features with the major genomic profiles and prognosis of World Health Organization grade III (G3) gliomas compared with those of glioblastomas (GBMs).Materials and MethodsWe enrolled 76 G3 glioma and 155 GBM patients with pathologically confirmed disease who had pretreatment brain MRI and major genetic information of tumors. Qualitative and quantitative imaging features, including volumetrics and histogram parameters, such as normalized cerebral blood volume (nCBV), cerebral blood flow (nCBF), and apparent diffusion coefficient (nADC) were evaluated. The G3 gliomas were divided into three groups for the analysis: with this isocitrate dehydrogenase (IDH)-mutation, IDH mutation and a chromosome arm 1p/19q-codeleted (IDHmut1p/19qdel), IDH mutation, 1p/19q-nondeleted (IDHmut1p/19qnondel), and IDH wildtype (IDHwt). A prediction model for the genetic profiles of G3 gliomas was developed and validated on a separate cohort. Both the quantitative and qualitative imaging parameters and progression-free survival (PFS) of G3 gliomas were compared and survival analysis was performed. Moreover, the imaging parameters and PFS between IDHwt G3 gliomas and GBMs were compared.ResultsIDHmut G3 gliomas showed a larger volume (p = 0.017), lower nCBF (p = 0.048), and higher nADC (p = 0.007) than IDHwt. Between the IDHmut tumors, IDHmut1p/19qdel G3 gliomas had higher nCBV (p = 0.024) and lower nADC (p = 0.002) than IDHmut1p/19qnondel G3 gliomas. Moreover, IDHmut1p/19qdel tumors had the best prognosis and IDHwt tumors had the worst prognosis among G3 gliomas (p < 0.001). PFS was significantly associated with the 95th percentile values of nCBV and nCBF in G3 gliomas. There was no significant difference in neither PFS nor imaging features between IDHwt G3 gliomas and IDHwt GBMs.ConclusionWe found significant differences in MRI features, including volumetrics, CBV, and ADC, in G3 gliomas, according to IDH mutation and 1p/19q codeletion status, which can be utilized for the prediction of genomic profiles and the prognosis of G3 glioma patients. The MRI signatures and prognosis of IDHwt G3 gliomas tend to follow those of IDHwt GBMs.

Abstract 3737: Mutant isocitrate dehydrogenase driven metabolic reprogramming results in therapeutic vulnerability to lactate dehydrogenase inhibition

Abstract Mutant isocitrate dehydrogenase (mIDH), with a gain-of-function in the production of an oncometabolite (R)-2-hydroxyglutarate (2-HG), is considered as a promising target for cancers carrying IDH mutations. IDH1 mutations, typically involving an amino acid substitution in the active site of the enzyme in codon 132, have been identified in a broad spectrum of solid tumors. The massive production of 2-HG remodels the metabolic network in cancer cells and results in epigenetic alterations facilitating malignant phenotypes. Of note, while the pharmacological inhibition of mIDH1 effectively leads to the remarkable reduction in the intracellular 2-HG level, it seems not associated with the sufficient suppression of solid tumor growth. We hence asked whether it is possible to identify extra metabolic vulnerability in IDH1 mutant tumors. To this end, we performed 13C isotope tracing analysis of glucose and glutamine, two major nutrient supply for 2-HG production, in solid tumor cell lines including HT1080 cells with spontaneous IDH1 mutation and IDH1 mutant glioma cell lines expressing mIDH1. [U-13C6]-glucose tracking enabled us to discover that IDH1 mutated tumors exhibit increased glycolysis and decreased tricarboxylic acid (TCA) metabolism, which can be reversed by mIDH1 inhibition. Meanwhile, cell mitochondrial stress test indicated decreased oxygen consumption rate (OCR) compared with the wildtype counterpart. These data suggest that 2-HG production paralyzes TCA metabolism and subsequent oxidative phosphorylation but enhances aerobic glycolysis, thus reprogramming tumor cells prone to Warburg effect. In line with this hypothesis, lactate dehydrogenase (LDH) inhibition that shut down lactate production increased 2-HG levels in IDH1 mutant cells. Further, LDH inhibition obtained the improved response in IDH1 mutant tumors while combined inhibition of mIDH1 abolished this effect. Together, we discovered that mutant IDH1 impaired TCA cycle by production of millimolar level 2HG which may lead to more dependency on glycolysis. Citation Format: Aiwei Bi, Jun Xu, Nan Jin, Xiaojing Lan, Shuai Tang, Matthew Shou, Jia Liu, Jian Ding, Meiyu Geng, Shuhai Lin, Min Huang. Mutant isocitrate dehydrogenase driven metabolic reprogramming results in therapeutic vulnerability to lactate dehydrogenase inhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3737.