IDH1R132H Expression Research Articles

A patient-derived cell model for malignant transformation in IDH-mutant glioma

Malignant transformation (MT) is commonly seen in IDH-mutant gliomas. There has been a growing research interest in revealing its underlying mechanisms and intervening prior to MT at the early stages of the transforming process. Here we established a unique pair of matched 3D cell models: 403L, derived from a low-grade glioma (LGG), and 403H, derived from a high-grade glioma (HGG), by utilizing IDH-mutant astrocytoma samples from the same patient when the tumor was diagnosed as WHO grade 2 (tumor mutational burden (TMB) of 3.96/Mb) and later as grade 4 (TMB of 70.07/Mb), respectively. Both cell models were authenticated to a patient’s sample retaining endogenous expression of IDH1 R132H. DNA methylation profiles of the parental tumors referred to LGG and HGG IDH-mutant glioma clusters. The immunopositivity of SOX2, NESTIN, GFAP, OLIG2, and beta 3-Tubulin suggested the multilineage potential of both models. 403H was more prompt to cell invasion and developed infiltrative HGG in vivo. The differentially expressed genes (DEGs) from the RNA sequencing analysis revealed the tumor invasion and aggressiveness related genes exclusively upregulated in the 403H model. Pathway analysis showcased an enrichment of genes associated with epithelial-mesenchymal transition (EMT) and Notch signaling pathways in 403H and 403L, respectively. Mass spectrometry-based targeted metabolomics and hyperpolarized (HP) 1-13C pyruvate in-cell NMR analyses demonstrated significant alterations in the TCA cycle and fatty acid metabolism. Citrate, glutamine, and 2-HG levels were significantly higher in 403H. To our knowledge, this is the first report describing the development of a matched pair of 3D patient-derived cell models representative of MT and temozolomide (TMZ)-induced hypermutator phenotype (HMP) in IDH-mutant glioma, providing insights into genetic and metabolic changes during MT/HMP. This novel in vitro model allows further investigation of the mechanisms of MT at the cellular level.Graphic

A multivariate retrospective analysis of high-grade gliomas: Survival and prognostic factors.

High-grade gliomas (HGGs) are highly malignant, aggressive, and have a high incidence and mortality rate. The aim of this study was to investigate survival outcomes and prognostic factors in patients with HGGs. In this retrospective study, a total of 159 patients with histologically confirmed HGGs were included. The recruitment period was from January 2011 to December 2019. We evaluated patient demographic data, tumor characteristics, treatment methods, immunocytochemistry results, overall survival (OS) time, and progression-free survival (PFS) time using Kaplan-<>Meier survival analysis with log-rank testing. Additionally, we employed Cox regression analysis to identify independent factors associated with survival outcomes. Kaplan-Meier survival analysis revealed that the 1-, 2-, and 5-years OS rates were 81.8%, 50.3%, and 12.6%, respectively. Similarly, the 1-, 2-, and 5-years PFS rates were 50.9%, 22.4%, and 3.1%, respectively. The median OS duration was 35.0 months. The univariate analysis indicated that postoperative pathological classification, grade, and age were significantly associated with patient outcomes (p < 0.01). Among the patients, 147 received concurrent chemoradiotherapy, while 12 did not. The immunohistochemical markers of ki-67, MGMT, IDH1R132H, and p53 demonstrated statistically significant differences in their prognostic impact (p = 0.001, p = 0.020, p = 0.003, and p = 0.021, respectively). In conclusion, we found that grades, age, pathological classification, ki-67, MGMT, and IDH1R132H expression were statistically significantly associated with PFS (p < 0.01, p = 0.004, p = 0.003, p = 0.001, p = 0.036, and p = 0.028). Additionally, immunohistochemical expressions of TRIB3 and AURKA were significantly higher in patients with shorter survival (p = 0.015 and p = 0.023). Tumor grade and the use of concurrent chemoradiotherapy after surgery were independent prognostic factors that significantly influenced patient survival. Additionally, tumor grade and MGMT expression were found to be independent factors affecting progression-free survival (PFS). Notably, the expression of TRIB3 and AURKA was higher in patients with poor survival outcomes.

Abstract 2746: MAGE-A3 co-expression with IDH1-R132H and IL-1β in colon cancer

Abstract Colorectal cancer (CRC) remains a significant cause of cancer death worldwide with an estimated 52,000 deaths in 2023. Over the past few decades, the incidence rate of CRC in individuals younger than 50 has been steadily increasing. Currently, diagnostic biomarkers play an important role in the detection and treatment of CRC. MAGE-A3 has been shown to be expressed in many tumor types, including colon cancer by RNA expression. Due to their high sequence homology, members of the MAGEA family have been difficult to evaluate and screen for their protein expression. However, in a previous study, highly specific antibodies were identified using CytoSections for MAGE-A3 immunohistochemistry. IL-1β is a cytokine that induces inflammatory responses and when localized to the nucleus in colon cancer cells it can promote stemness. IL-1β expression has been shown to be increased in wildtype IDH1 positive glioblastoma. However, the relationship between IL-1β and IDH1 has not been studied in colon cancer. In this study, the difference in the expression of MAGE-A3, IL-1β, and wildtype IDH1 compared to mutant IDH1-R132H in colon cancer tissues was evaluated. The results show that IL-1β, wildtype IDH1, and MAGE-A3 were co-expressed in 27 of the 38 colon cancer tumors. However, IDH1-R132H expression was only seen in 20% of the tumors. This study suggests that MAGE-A3, IL-1β, and IDH1 are candidate biomarkers for immunotherapy due to their high expression in colon cancer tissues. Citation Format: Andy/Xi Han, Rachel Gonzalez, Jina Yom, Zhaoying Guo, Bailey Gilmore, Eden Zewdu, Tianli Qu, Hailey/YiChen Guo, Qi Ren, Xiaomin Hu, Ranran Zhang, Zhaohui Wu, Xuan Liu, Wei Fu. MAGE-A3 co-expression with IDH1-R132H and IL-1β in colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2746.

Prognostic Value of ATRX and p53 Status in High-Grade Glioma Patients in Morocco.

Glioblastoma and astrocytoma, grade 4, are the most common and aggressive brain tumors. Several biomarkers, such as the isocitrate dehydrogenase mutation (IDH-1), alpha-thalassemia/mental retardation, and the X-linked mutation (ATRX), enable more accurate glioma classification and facilitate patient management. This study aimed to determine the prognostic value of clinical and molecular factors (IDH, TP53, and ATRX mutations). We also studied the relationship between these molecular markers and the overall survival (OS) of 126 patients with grade 4 glioblastoma/astrocytoma. The immunohistochemical study was conducted using antibodies namely, IDH1, R132H, p53, and ATRX. Statistical tests were used to investigate factors that might influence overall survival using IBM SPSS Statistics, version 25.0 (IBM Corp., Armonk, NY). The median age at diagnosis was 51.5 years. Patients with a Karnofsky performance score (KPS) <70 presented less favorable survival outcomes compared to those with a KPS ≥70. The median OSfor patients was found to be 11.17 months. Expression ofIDH1 R132H was found in 13.5% of patients, p53 overexpression was identified in 55.6% of cases, and loss of ATRX expression was detected in 11.9%. The group of patients with IDH mutant/ATRX mutant/p53 wild-typehad the best prognosis (OS= 27.393 months; p = 0.015). Our results were in line with previous studies. The clinical value of IDH and ATRX mutations in prognostic assessment was confirmed (p ≤0.05). The overexpression of p53 had no significant impact on OS (p = 0.726). Therefore, p53 alone cannot predict survival in glioblastoma patients. Based on the results, these biomarkers may be a potential therapeutic target to prolong patient survival, hence the need for further investigations.

Evaluation of Immunohistochemical Expression of ALK-1 in Gliomas, WHO Grade 4 and Its Correlation with IDH1-R132H Mutation Status.

Glioblastoma (GB), a grade 4 glioma is the most common primary malignant brain tumor in adults. Recently, the mutation status of isocitrate dehydrogenase (IDH) has been crucial in the treatment of GB. IDH mutant cases display a more favorable prognosis than IDH-wild type ones. The anaplastic lymphoma kinase (ALK) is expressed as a receptor tyrosine kinase in both the developing central and peripheral nervous systems. Increasing lines of evidence suggest that ALK is over-expressed in GB and represents a potential therapeutic target. The goal of the current study was to investigate ALK-1 immunohistochemical expression in gliomas, grade 4, besides its correlation with IDH1-R132H mutation status and the clinicopathological parameters of the tumors. Seventy cases of gliomas, grade 4 were tested for immunohistochemical expression of ALK-1 & IDH1-R132H in the tumor cells. ALK-1 immunoexpression was detected in 22.9% of our cases and IDH1-R132H mutation was detected in 12.9% of them. ALK-1 expression (100%) was only detected in the more aggressive IDH R132H-negative GBs. ALK-1 expression was also noted in the larger-sized tumors, more in males and patients older than the mean age. Conclusion: Our results suggest that mutations in ALK-1 may predict a more dismal prognosis since ALK expression was only noted in IDH-R132H negative GBs known to have a considerably poorer outcome compared to IDH-R132H mutant cases. GBs with detectable ALK-protein expression could potentially experience substantial clinical advantages through the utilization of newly introduced ALK inhibitors allowing personalized treatment to a subset of patients. Hence, future studies targeting ALK in IDH wildtype Glioblastomas including clinical trials on larger scales are recommended.

IMMU-15. INTERPLAY BETWEEN ATRXAND IDH1 MUTATIONS GOVERNS INNATE IMMUNE RESPONSES IN DIFFUSE GLIOMAS

Abstract Stimulating the innate immune system has been explored as a therapeutic option for the treatment of gliomas. Inactivating mutations in alpha-thalassemia retardation X-linked (ATRX) are defining molecular alterations in IDH-mutant astrocytomas and have been implicated in dysfunctional immune signaling. However, little is known about the interplay between ATRX loss and IDH mutation on innate immunity. To explore this interaction, we used both CRISPR and the RCAS/tva system to generate murine models of ATRX-deficient glioma, in the presence and absence of the IDH1 R132H mutation. We found that ATRX-deficient glioma cells were exquisitely sensitive to dsRNA-based innate immune agonism, displaying increases in inflammatory gene expression and profound cytokine release in vitro, while mice bearing ATRX KO tumors displayed increased T-cell infiltration and improved survival. The presence of IDH1 R132H dampened baseline expression of key innate immune genes and cytokines, with genetic and pharmacological inhibition of IDH1 R132H partially rescuing this suppression. Despite the suppression observed at baseline, IDH1 R132H expression did not interfere with the ATRX KO-mediated sensitivity to dsRNA agonism. These results demonstrate that ATRX loss primes cells for recognition of and activation against dsRNA, while IDH1 R132H reversibly masks this priming. Thus, this study suggests that innate immunity is a potential therapeutic vulnerability of astrocytoma. Further studies are in progress to validate the influence of ATRX loss on immune signaling and tumor-immune coevolution within human tumors.

P19.02.A FUNCTIONAL CONSEQUENCES OF IDH1 AND CIC MUTATIONS ON OLIGODENDROGLIOMA CELLS OF ORIGIN

Abstract BACKGROUND Oligodendrogliomas are primitive tumors of the central nervous system characterized by mutations in isocitrate dehydrogenase 1 (IDH1R132H) gene, codeletion of 1p and 19q chromosomic arms and mutations in Capicua (CIC) gene. Oligodendrocyte precursor cells (OPCs) are potential cells of origin for oligodendrogliomas and OPC-like tumor cells are responsible for tumor amplification at early stages of gliomagenesis. Although genetic alterations are well characterized for these tumors, little is known about the roles of IDH1 and CIC in oligodendroglioma initiation and development. Individually, IDH1 and CIC mutations can induce neoplastic characteristics but are not sufficient for tumoral development. We aim to understand how IDH1 and CIC mutations impact OPC development and whether these alterations are sufficient for tumoral initiation. METHODS We have generated an inducible mouse model allowing endogenous expression of IDH1R132H and inactivation of CIC in postnatal OPCs. We analyzed by immunofluorescence the proliferation and differentiation status of mutated oligodendroglial cells and other brain cells, at postnatal and adult stages. RESULTS We describe distinct effects of these mutations on oligodendroglial cell number and proliferation, at early and late time points. In addition, we found that IDH1R132H increases the proliferation of other brain cell types, suggesting paracrine effects of this mutation in the brain. We find no evidence of tumor in the brain of mice mutated for both IDH1 and CIC at late time points. CONCLUSION Our study describes for the first time the phenotypic impact of the combined expression of IDH1 and CIC mutations on oligodendroglial lineage cells and other brain cells, leading to a better understanding of oligodendroglioma development.

Prognostic significance of HIF1-α immunohistochemical expression in gliomas and it's relation to IDH1 mutation status

BackgroundGliomas are the commonest primary adults’ brain tumors. Hypoxia performs an essential role in gliomas’ initiation as well as progression through hypoxia inducible factor (HIF-1α) activation, which could serve as a promising target in treatment of gliomas. Our study aimed to evaluate types and grades of glioma cases and detect isocitrate dehydrogenase 1 (IDH1) mutation status and expression of HIF-1α in all included cases and its correlation with clinical data and pathological parameters.ResultsSamples from 71 patients who were diagnosed with glioma were studied immunohistochemically for IDH1-R132H (if indicated) and HIF-1α expression. Expression of HIF-1α was detected in 73.2% of the included 71 gliomas. HIF-1α expression significantly increased in older patients, in high-grade gliomas and in tumors positive for necrosis. We studied IDH1 mutation in the histologically diagnosed grade 2, 3and 4 astrocytic and oligodendroglial tumors (51 cases out of the included 71 gliomas). IDH1-R132H immunohistochemical expression was positive in 62.7% of cases. IDH1 mutation was significantly higher with younger age. IDH1 mutation was noted also with lower tumor grade. A statistically significant relation was detected between negative IDH1-R132H expression and high level of HIF-1α immunohistochemical expression.ConclusionAbsence of IDH1 mutation with increased HIF-1α expression among high-grade gliomas suggesting both as predicting indicators for poor prognosis.

Expression of CD133 Cancer Stem Cell Marker in IDH-Mutant and IDH-wildtype (Isocitrate Dehydrogenase) Astrocytoma.

This study evaluated the differences between IDH1-R132H and CD133 expression in different categories of astrocytoma. This study used a cross-sectional design. Sixty-seven paraffin embedded block of Diffuse Astrocytoma (DA), Anaplastic Astrocytoma (AA) and Glioblastoma (GB) were assessed using using the monoclonal antibody IDH1-R132H and Rabbit polyclonal antibody CD133. It was found that there was a significant relationship between the expression of IDH1-R132H and CD133 in DA, AA and GB (p<0.001). Astrocytoma with IDH-mutant molecular status will express more markers of cancer stem cell CD133 than IDH-wildtype. The IDH1-R132H and CD133 can provide predictive value on treatment success, disease prognosis, recurrence and can be considered as target combination therapy with chemotherapy.

CLRM-07 A MULTIVARIATE RETROSPECTIVE ANALYSIS OF 159 PATIENTS WITH HIGH-GRADE GLIOMAS: OVERALL SURVIVAL, PROGRESSION-FREE SURVIVAL, AND PROGNOSTIC FACTORS

BACKGROUND AND PURPOSEHigh-grade gliomas are highly malignant, aggressive, high incidence rate, and mortality. The purpose of this study was to analyze retrospectively and identify prognostic factors of patients with high-grade gliomas diagnosed by biopsy or postoperative pathological examination. METHODSIn this retrospective study, we analyzed the patient’s demographic data, tumor characteristics, treatment approaches, immunocytochemistry results, the overall survival (OS) time, and the progression-free survival (PFS) time in a series of 159 histologically proven high-grade gliomas recruited from January 2011 to December 2019. OS time and PFS time were analyzed by Kaplan-Meier survival analysis with log-rank test and found the independent factors by using Cox regression analysis. RESULTSSurvival analysis showed that an OS of 84.90%, 55.35% and 13.20% was observed at 1, 2 and 5 years, respectively. And a PFS of 56.6%, 25.26% and 3.14% was observed at 1, 2 and 5 years, respectively. The mean OS was 52.73 months and mOS was 35 months. Univariate analysis showed that postoperative pathological classification and grade and age were statistically significant for patient outcome (P < 0.01). 147 patients underwent concurrent chemoradiotherapy and 80 of them died; 12 patients did not undergo concurrent chemoradiotherapy and 10 died (P = 0.03); There were statistically significant differences in the prognostic impact of Ki-67 expression, MGMT, IDH1R132H and p53 mutations by immunohistochemistry (P = 0.001; P = 0.016; P = 0.003; and P = 0.021, respectively). Similarly, we concluded that different grades, age, pathological classification, Ki-67 and IDH1R132H expression by immunohistochemistry were statistically significantly associated with PFS (P < 0.01; P = 0.004; P = 0.003; P = 0.001; P = 0.028). CONCLUSIONSTumor grade and concurrent chemoradiotherapy after surgery were independent prognostic factors affecting patients’ survival, and grade was also an independent factor affecting PFS.

Analysis of Isocitrate Dehydrogenase (IDH) expression in astrocytoma patients: cases of South Sulawesi, Indonesia

Background: Astrocytoma is the most common primary intracerebral tumor in adults and causes high morbidity and mortality. Most patients with astrocytomas, especially diffuse gliomas, have a poor prognosis. Recent genetic and epigenetic studies have shown that mutations in the Isocitrate Dehydrogenase (IDH) gene play an important role in the pathogenesis and prognosis of gliomas, thus facilitating IDH1 mutations in the population to become an important marker, not only to assist in the diagnosis and prognostic factors of these gliomas but also to develop therapeutic targets as currently available. This study aims to see differences in the expression of the IDH in each astrocytoma classification. Methods: A cross-sectional analytic study was conducted at the Anatomical Pathology Laboratory, Faculty of Medicine, Universitas Hasanuddin, from October 2020 to August 2021. The research sample came from 65 paraffin block preparations for primary brain tumors with the diagnosis of Diffuse Astrocytoma (DA), Anaplastic Astrocytoma (AA) and Glioblastoma (GB). The immunohistochemical staining was performed using the monoclonal antibody IDH1-R132H. The microscopic assessment was carried out using a light microscope. Data were analyzed using SPSS version 20 for Windows. Results: There was a significant relationship between the expression of IDH1-R132H in each astrocytoma classification (p=0.008). The prevalence of astrocytoma with negative IDH1-R132H expression (IDH-wildtype) is lower by 21 samples (32.3%) compared to astrocytoma with positive IDH1-R132H expression (IDH-mutant), which is 44 samples (67.7%). Conclusion: There are significant differences in the expression of IDH1-R132H in Diffuse Astrocytoma, Anaplastic Astrocytoma and Glioblastoma, where the proportion of IDH-mutant status is higher than IDH-wildtype and IDH1 mutation status has a significant relationship with tumor grade.

Clinical, Morphological, and Molecular Study of Diffuse WHO Grade II and III Astrocytomas: A Retrospective Analysis from a Single Tertiary Care Institute

Abstract Introduction Astrocytomas are the most common gliomas, classified on the basis of grade and IDH mutation status according to the World Health Organization (WHO) 2016 update. IDH mutations are seen in 70 to 80% of diffuse grade II and III astrocytomas and are associated with better outcome. They serve as predictive biomarker in IDH-targeted therapies such as small-molecule inhibitors or vaccines. Objective The aim of this study was to analyze the clinical, morphological, immunohistochemical, and molecular genetic characteristics of diffuse astrocytoma (DA: grades II and III). The IDH mutant and wild-type tumors are compared and contrasted with survival analysis on follow-up. Materials and Methods This was a retrospective study conducted on surgically resected tumor specimens. The hematoxylin and eosin-stained slides were examined for histologic features. Immunohistochemistry (IHC) was performed using IDH1R132H, ATRX, p53, and Ki67. All cases of negative immunohistochemical expression of IDH1R132H were subjected to IDH1 mutation analysis by Sanger sequencing. Overall survival was estimated by the Kaplan-Meier method using the log-rank (Mantel–Cox) test. Results The study included 51 cases of DA in the age of 17 to 66 years, mean ± standard deviation was 35.5 ± 9.7 years, and male:female ratio was 2:1.The IDH1R132H cytoplasmic immunopositivity was seen in 36 cases (70.5%), of which 63.6% were of grade II and 72.5% were of grade III. ATRX showed loss of expression in 50 cases (98%), and p53 showed diffuse strong immunohistochemical expression in all the cases of IDH mutant tumors. The difference in the age at presentation for IDH mutant (32.5 years) and wild type tumors (38 years) was statistically significant. Median survival was 55.3 months and 22.2 months in of IDH mutant and wild type cases, respectively. Conclusion IHC and sequencing for IDH mutations is helpful in making an integrated diagnosis and classifying definite molecular subgroups of astrocytic tumors. Mutations in IDH core-elate with survival. IDH mutant tumors showed longer survival duration and are good prognostic indicators.

Expression of CD44 and IDH1 R132H in Gliomas and their Prognostic Relevance

Abstract Gliomas are among the most common and aggressive primary brain tumours with dismal prognosis. A lot of research has been directed towards elucidating the molecular basis of these tumours, but few reliable prognostic markers are known. It is necessary to continue to study possible molecular factors that may be involved in development of gliomas or have a prognostic role. CD44 is a marker of neural stem cells and is involved in invasiveness of different tumours. In addition, IDH1 R132H mutant protein is expressed in secondary glioblastomas (GBMs) with much better prognosis. The goal of this study was to evaluate the expression and prognostic role of CD44 and IDH1 R132H in gliomas by immunohistochemistry. In this study, we found that CD44 expression was more prominent in glioblastomas than diffuse astrocytomas and it was not correlated with IDH1 mutational status. CD44 was not found to have a prognostic role in gliomas, in contrast with IDH1 R132H positive status, which was associated with better prognosis. Interestingly, higher CD44 expression values were associated with smaller size of GBMs and female gender indicating that the glioma stem cell population may be altered by gender specific factors and the growth rate of the tumour.

Mutant IDH1 Differently Affects Redox State and Metabolism in Glial Cells of Normal and Tumor Origin.

IDH1R132H (isocitrate dehydrogenase 1) mutations play a key role in the development of low-grade gliomas. IDH1wt converts isocitrate to α-ketoglutarate while reducing nicotinamide adenine dinucleotide phosphate (NADP+), whereas IDH1R132H uses α-ketoglutarate and NADPH to generate the oncometabolite 2-hydroxyglutarate (2-HG). While the effects of 2-HG have been the subject of intense research, the 2-HG independent effects of IDH1R132H are still ambiguous. The present study demonstrates that IDH1R132H expression but not 2-HG alone leads to significantly decreased tricarboxylic acid (TCA) cycle metabolites, reduced proliferation, and enhanced sensitivity to irradiation in both glioblastoma cells and astrocytes in vitro. Glioblastoma cells, but not astrocytes, showed decreased NADPH and NAD+ levels upon IDH1R132H transduction. However, in astrocytes IDH1R132H led to elevated expression of the NAD-synthesizing enzyme nicotinamide phosphoribosyltransferase (NAMPT). These effects were not 2-HG mediated. This suggests that IDH1R132H cells utilize NAD+ to restore NADP pools, which only astrocytes could compensate via induction of NAMPT. We found that the expression of NAMPT is lower in patient-derived IDH1-mutant glioma cells and xenografts compared to IDH1-wildtype models. The Cancer Genome Atlas (TCGA) data analysis confirmed lower NAMPT expression in IDH1-mutant versus IDH1-wildtype gliomas. We show that the IDH1 mutation directly affects the energy homeostasis and redox state in a cell-type dependent manner. Targeting the impairments in metabolism and redox state might open up new avenues for treating IDH1-mutant gliomas.

Synthetic Lethal Interaction between Apto-253 and IDH1/2 Mutations

APTO-253 is a small molecule with a novel mechanism of action and potent antiproliferative activity against cell lines derived from a wide range of human malignancies. A Phase 1 study of APTO-253 was completed in patients with advanced solid tumors. It was well tolerated and produced evidence of antitumor activity in patients but did not cause myelosuppression even at the maximum tested dose. A phase 1a/b trial of APTO-253 in patients with relapsed/refractory acute leukemias (including AML) and high-risk MDS (NCT02267863) is currently underway. We previously reported that APTO-253 was converted intracellularly to a complex containing one molecule of iron and three molecules of APTO-253 [Fe(253)3]. Both APTO-253 and Fe(253)3 stabilized DNA quadruplex (G4) structures in the Myc promotor region to reduce the expression of Myc (Figure 1). Stabilization of G4 structures has been reported to stall replication forks and produce DNA strand breaks. Treatment of cancer cells with APTO-253 produced time and concentration-dependent γH2AX foci formation and DNA double strand breaks that have to be repaired by homologous recombination. Loss of either BRCA1 or BRCA2 function in multiple isogenic paired cell lines resulted in hypersensitivity to APTO-253 whose magnitude was similar to the effects of PARP inhibitors, olaparib. Thus, APTO-253 is a member of the limited repertoire of drugs which can exploit defects in homologous recombination and is of particular interest because it does not produce myelosuppression. The goal of this project was to identify synthetic lethal interactions in addition to BRCA1/2 deficiency that can guide combination drug studies. The normal function of the isocitrate dehydrogenase (IDH) enzymes is to catalyze the conversion of isocitrate to α-ketoglutarate (αKG) in the citric acid cycle. IDH1 mutations occur in more than 70% of low-grade gliomas, 20% of high-grade glioblastomas and with a frequency of about 10% in AML, cholangiocarcinomas, melanomas and chondrosarcomas. Additionally, mutations are also identified in IDH2 in about 4% of gliomas and 10% of AMLs. IDH1/2 alterations are heterozygous missense mutations that confer a neomorphic activity on the encoded enzyme such that they covert αKG to (R)-2-hydroxyglutarate [(R)-2HG]. (R)-2HG is an oncometabolite with pleiotropic effects on cell biology including chromatin methylation and cellular differentiation. It was reported that IDH1/2 mutations induce a homologous recombination defect that renders tumor cells exquisitely sensitive to PARP inhibitors. We used 2 pairs of isogenic IDH1 wild type and mutant cell lines to test the hypothesis that cells carrying IDH1/2 mutations are hypersensitive to APTO-253. Induction of the expression of IDH1 R132H in THP-1 AML cells increased the 2-HG concentration ~150-fold whereas induction of wild-type IDH1 expression increased it only 2-fold (doi: 10.1038/nm.3788). THP-1 cells expressing the mutant IDH1 R132H were hypersensitive the treatment of APTO-253 compared to cells expressing the wild-type IDH1 (Figure 2). Comparison of wild-type and isogenic IDH1 R132H HCT116 cells disclosed a ~100-fold higher level of (R)-2-HG in the mutant cells (doi: 10.1126/scitranslmed.aal2463), and an increase in sensitivity to the cytotoxic effect of APTO-253 (Figure 3). These results are consistent with the observation that both APTO-253 and increased levels of 2-HG cause DNA damage that depends on homologous recombination for repair and that this favors a synthetic lethal interaction. We surmise that the ability of APTO-253 to markedly reduce the expression of Myc further contributes to the favorable interaction. This data further supports the conclusion that defects in homologous DNA repair can enhance the potency of APTO-253 and suggest the use of this non-myelosuppressive drug in both IDH1/2 mutant AML and solid tumors. Disclosures Zhang: Aptose Biosciences, Inc: Employment. Rice:Aptose Biosciences, Inc: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Howell:Aptose Biosciences, Inc: Consultancy, Research Funding.

Radiosensitization and a Less Aggressive Phenotype of Human Malignant Glioma Cells Expressing Isocitrate Dehydrogenase 1 (IDH1) Mutant Protein: Dissecting the Mechanisms.

The presence of an isocitrate dehydrogenase 1 (IDH1) mutation is associated with a less aggressive phenotype, increased sensitivity to radiation, and increased overall survival in patients with diffuse glioma. Based on in vitro experimentations in malignant glioma cell lines, the consequences on cellular processes of IDH1R132H expression were analyzed. The results revealed that IDH1R132H expression enhanced the radiation induced accumulation of residual γH2AX foci and decreased the amount of glutathione (GSH) independent of the oxygen status. In addition, expression of the mutant IDH1 caused a significant increase of cell stiffness and induced an altered organization of the cytoskeleton, which has been shown to reinforce cell stiffness. Furthermore, IDH1R132H expression decreased the expression of vimentin, an important component of the cytoskeleton and regulator of the cell stiffness. The results emphasize the important role of mutant IDH1 in treatment of patients with diffuse gliomas especially in response to radiation. Hence, detection of the genetic status of IDH1 before therapy massively expands the utility of immunohistochemistry to accurately distinguish patients with a less aggressive and radiosensitive IDH1-mutant diffuse glioma suitable for radiotherapy from those with a more aggressive IDH1-wildtype diffuse glioma who might benefit from an individually intensified therapy comprising radiotherapy and alternative medical treatments.

Molecular classification of diffuse gliomas.

In this study we assessed whether gliomas could be subdivided into different molecular subtypes by immunohistochemistry (IHC) reminiscent of those first described by Verhaak et al. in 2010 (classical, proneural, mesenchymal and neural). We also evaluated the prognostic significance of single molecular factors and searched for significant correlations between markers. In this study, we included 146 patients with glioblastomas (GBMs) and 26 with diffuse astrocytomas (DAs). The glioma samples were tested for PDGFRA, IDH1 R132H, CD44, p53, Ki-67, p21 and p27 expression. We found that gliomas could be subdivided into molecular subtypes by IHC. Fifty per cent of GBMs were of the proneural subtype, 18.5% of mesenchymal subtype and 31.5% were not otherwise classified. However, most of the DAs (92.3%) belonged to the proneural subtype. No prognostic role was found for the molecular subtypes, but predictive roles were noted. Both proneural and mesenchymal molecular subtypes showed a benefit from the addition of chemotherapy and radiotherapy; however, the mesenchymal subtype showed a greater response. Interestingly, the mesenchymal subtype did not receive any benefit from the addition of radiotherapy compared with palliative management and surgery alone. Regarding single molecular markers, only IDH1 R132H was found to have a prognostic role for GBMs. There was a trend towards better survival in tumours with lower PDGFRA expression (p = 0.066). In DAs, PDGFRA and Ki-67 expression had prognostic roles. The following statistically significant correlations were found in GBMs: Ki-67/p53, Ki-67/p27 and p53/PDGFRA; in DAs: p53/PDGFRA, CD44/PDGFRA, and p21/PDGFRA.

IDH1R132H is intrinsically tumor-suppressive but functionally attenuated by the glutamate-rich cerebral environment.

Recurrent heterozygous mutation of isocitrate dehydrogenase 1 gene (IDH1), predominantly resulting in histidine substitution at arginine 132, was first identified in glioma. The biological significance of IDH1R132H, however, has been controversial, and its prevalent association with glioma remains enigmatic. Although recent studies indicate that IDH1R132H is nonessential to tumor growth or even anti-tumor growth, whether IDH1R132H initiates gliomagenesis remains obscure. In this study, we report that IDH1R132H is intrinsically tumor-suppressive but the activity can be attenuated by glutamate—the cerebral neurotransmitter. We observed that IDH1R132H was highly suppressive of subcutaneous tumor growth driven by platelet-derived growth factor B (PDGFB), but IDH1R132H tumor growth and glioma penetrance were virtually indistinguishable from those of IDH1-wildtype tumors in orthotopic models. In vitro, addition of glutamate compromised IDH1R132H inhibition of neurosphere genesis, indicating glutamate promotion of oncogenic dominance. Furthermore, we observed that IDH1R132H expression was markedly decreased in tumors but became more permissible upon the deletion of tumor-suppressor gene Cdkn2a. To provide direct evidence for the opposing effect of IDH1R132H on PDGFB-driven glioma development, we explored tandem expression of the two molecules from a single transcript to preclude selection against IDH1R132H expression. Our results demonstrate that when juxtaposed with oncogenic PDGFB, IDH1R132H overrides the oncogenic activity and obliterates neurosphere genesis and gliomagenesis even in the glutamate-rich microenvironment. We propose therefore that IDH1R132H is intrinsically suppressive of glioma initiation and growth but such tumor-suppressive activity is compromised by the glutamate-rich cerebral cortex, thereby offering a unifying hypothesis for the perplexing role of IDH1R132H in glioma initiation and growth.

Cerebellar glioblastoma: a clinical series with contemporary molecular analysis.

Glioblastomas (GBM) are localized in only less than 1% of patients in the cerebellum. Therefore, tumor characteristics, survival, and the efficacy of therapies are not yet well defined. The present study aims to characterize the molecular features of cerebellar GBM (GBMc) in 8 patients treated with contemporary modality in our institution. Patients' treatment history, progression-free survival (PFS), and overall survival (OS) were analyzed. All histopathological specimens were re-investigated. EGFR amplification was determined by FISH, H3F3A, and HIST1H3B mutation status and MGMT promoter methylation after bisulfite treatment by pyrosequencing and BRAF V600E by pyrosequencing and immunohistochemistry. TERT promoter mutations were analyzed by Sanger sequencing, CDKN2A/B deletions by digital PCR. The expression of IDH1 R132H, ATRX, and p53 was determined through immunohistochemistry. Six adults and two children (mean age 36years) underwent tumor resection via medial or lateral suboccipital craniotomy. The median overall survival (mOS) of the adult patients was 7months. GBMc from two children demonstrated a H3F3A K27M mutation. One of these also harbored a BRAF V600E mutation and has already had a PFS of 74months. Mutated IDH1 R132H protein was expressed in 2 GBM from adult patients with previous supratentorial anaplastic astrocytoma. One patient carried a TERT promoter mutation. Another patient initially presented with a thalamic pilocytic astrocytoma. The cerebellar tumor revealed neither a BRAF V600E nor a H3F3A mutation but a homozygous CDKN2A/B deletion. GBM located in the cerebellum can be found in all age groups. We provide novel molecular genetic data on these rare tumors. Mutated IDH1 R132H protein and H3F3A K27M mutations indicate that a substantial number of GBMc are "metastatic" or "diaschismatic" lesions. Mutation of BRAF V600E may have a stronger biological significance than H3F3A K27M alterations. In a subset of patients, GBM may arise primarily as a distinct entity in the cerebellum.

Abstract 5583: Plasma levels of circulating MACC1 transcripts co-segregate with other prognostic markers and treatment response in glioblastoma patients

Abstract IDH1-mutation and MGMT-promoter methylation are established prognostic markers in Glioblastoma multiforme (GBM); however, invasive procedures are needed to obtain the required tumor tissue. Metastasis-associated in colon cancer-1 (MACC1) can easily be measured in peripheral blood and has been established as a prognostic plasma marker for several solid cancer entities. Further, MACC1 has been identified by us and others as a promising biomarker for prognostication for GBM, when detected in the tumor tissue. Here, we evaluated whether circulating MACC1 transcripts could be useful to predict clinical outcome and response to therapy in GBM. Plasma samples were collected from GBM patients (IDH1 wildtype (wt), IDH1R132H, and unspecified) before surgery. Samples from healthy volunteers served as controls. MACC1-transcript levels, determined by qRT-PCR, were correlated with patient overall survival (OS) and clinical data of known prognostic significance. Cut-off values for Kaplan-Meier analyses were determined by ROC calculations. Cluster analyses were performed. MACC1 transcripts were higher in plasma of GBM patients compared to healthy controls (P&amp;lt;0.0001), yet differentially distributed within the cohort. Low MACC1 levels clustered together with all other favorable markers, i.e. small tumor volume, young age, IDH1R132H and MGMT promoter methylation. MACC1 levels correlated with patient prognosis in conjunction with the IDH mutation status: patients with IDH1R132H mutation and low MACC1 levels showed the most favorable outcome (mean OS 54.0 months (m), SD=9.8; 95% CI 34.7-73.3), those with IDH1wt and high MACC1 had the worst prognosis (mean OS 10.5 m), while those with IDH1wt and low MACC1 were intermediate (mean OS 20.3 m). No patients in this cohort displayed IDH1R132H and high MACC1 expression. Interestingly, patients with low MACC1 levels receiving standard therapy (operation and radiochemotherapy according to Stupp) survived longest (mean OS 36.9 m, SD=6.5; 95% CI 24.1-49.7). Patients with high MACC1 showed shorter OS (mean OS 13.0 m). The worst prognosis had patients not receiving the standard regimen, independently of their MACC1 levels (MACC1 low: 5.2 m; MACC1 high: 5.5 m). The inclusion of circulating MACC1 transcript levels into the diagnostic workup might improve the accuracy of outcome prediction and thus help to define more precise risk categories of GBM patients. Whether pharmaceutical inhibition of MACC1 expression might be of general benefit for the treatment response and survival of GBM patients remains to be determined. Citation Format: Carsten Hagemann, Nikolas Neuhaus, Mathias Dahlmann, Almut F. Kessler, Dennis Kobelt, Pia Herrmann, Matthias Eyrich, Benjamin Freitag, Thomas Linsenmann, Camelia Monoranu, Ralf-Ingo Ernestus, Mario Löhr, Ulrike S. Stein. Plasma levels of circulating MACC1 transcripts co-segregate with other prognostic markers and treatment response in glioblastoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5583.