IDH1-mutated Cancer Research Articles

Highly Recurrent IDH1 Mutations in Prostate Cancer With Psammomatous Calcification

Prostate cancer is a heterogeneous disease with several well-recognized morphologic subtypes and histologic variants—subsets of which are enriched for or associated with specific genomic alterations. Herein, we report a cohort of 4 unique prostate cancers characterized by intratumoral psammomatous calcification—which we have termed prostate cancer with psammomatous calcification (PCWPC). Clinicopathologic review demonstrates that PCWPCs are high-grade (grade group ≥3) tumors that involve the anterior prostate, and integrative targeted next-generation sequencing reveals recurrent hotspot IDH1 mutations. This morphology-molecular correlation is independently confirmed in The Cancer Genome Atlas prostatic adenocarcinoma cohort, with 3 of the 5 IDH1-mutant prostate cancers showing psammomatous calcification (rφ = 0.67; Fisher exact test, P < .0001). Overall, these findings suggest that PCWPC represents a novel subtype of prostate cancer enriched for an anterior location and the presence of hotspot IDH1 mutations. Recognition of these unique morphologic features could help identify IDH1-mutant prostate cancer cases retrospectively and prospectively—facilitating future large research studies and enabling clinical trial enrollment and precision medicine approaches for patients with advanced and/or aggressive disease.

Vaccines Targeting Gliomas: Antigens Matter.

Article Tools UNDERSTANDING THE PATHWAY Article Tools OPTIONS & TOOLS Export Citation Track Citation Add To Favorites Rights & Permissions COMPANION ARTICLES Phase IIa Study of SurVaxM Plus Adjuvant Temozolomide for Newly Diagnosed Glioblastoma. December 15, 2022 ARTICLE CITATION DOI: 10.1200/JCO.22.02616 Journal of Clinical Oncology - published online before print January 9, 2023 PMID: 36623232 Vaccines Targeting Gliomas: Antigens Matter Michael Platten , MD1,2,3,4xMichael PlattenSearch for articles by this author and Niklas Grassl, MD1,2,4xNiklas GrasslSearch for articles by this author Show More 1DKTK CCU Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Heidelberg, Germany2Department of Neurology, Medical Faculty Mannheim, MCTN, Heidelberg University, Mannheim, Germany3Helmholtz Institute for Translational Oncology (HI-TRON) Mainz, German Cancer Research Center, Mainz, Germany4DKFZ-Hector Cancer Institute at University Medical Center Mannheim, Mannheim, Germany https://doi.org/10.1200/JCO.22.02616 First Page Full Text PDF Figures and Tables © 2023 by American Society of Clinical OncologyAUTHOR CONTRIBUTIONSConception and design: Michael PlattenCollection and assembly of data: Niklas GrasslManuscript writing: All authorsFinal approval of manuscript: All authorsAccountable for all aspects of the work: All authorsAUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTERESTVaccines Targeting Gliomas: Antigens MatterThe following represents disclosure information provided by authors of this manuscript. All relationships are considered compensated unless otherwise noted. Relationships are self-held unless noted. I = Immediate Family Member, Inst = My Institution. Relationships may not relate to the subject matter of this manuscript. For more information about ASCO's conflict of interest policy, please refer to www.asco.org/rwc or ascopubs.org/jco/authors/author-center.Open Payments is a public database containing information reported by companies about payments made to US-licensed physicians (Open Payments).Michael PlattenStock and Other Ownership Interests: EvotechConsulting or Advisory Role: Novartis (Inst), Monte Rosa Therapeutics (Inst)Research Funding: Bayer (Inst), Merck (Inst), Pfizer (Inst), Novartis (Inst), Roche/Genentech (Inst)Patents, Royalties, Other Intellectual Property: Diagnosing and treating IDH1-mutant cancers, treating H3.3K27M-mutant cancers, treating cancers with AHR antagonistsNo other potential conflicts of interest were reported. Companion Phase IIa Study of SurVaxM Plus Adjuvant Temozolomide for Newly Diagnosed Glioblastoma

Hyperthermia as a Potential Cornerstone of Effective Multimodality Treatment with Radiotherapy, Cisplatin and PARP Inhibitor in IDH1-Mutated Cancer Cells.

Mutations in the isocitrate dehydrogenase 1 (IDH1MUT) gene occur in various types of malignancies, including ~60% of chondrosarcomas, ~30% of intrahepatic cholangiocarcinomas and &gt;80% of low-grade gliomas. IDH1MUT are causal in the development and progression of these types of cancer due to neomorphic production of the oncometabolite D-2-hydroxyglutarate (D-2HG). Intracellular accumulation of D-2HG has been implicated in suppressing homologous recombination and renders IDH1MUT cancer cells sensitive to DNA-repair-inhibiting agents, such as poly-(adenosine 5'-diphosphate-ribose) polymerase inhibitors (PARPi). Hyperthermia increases the efficacy of DNA-damaging therapies such as radiotherapy and platinum-based chemotherapy, mainly by inhibition of DNA repair. In the current study, we investigated the additional effects of hyperthermia (42 °C for 1 h) in the treatment of IDH1MUT HCT116 colon cancer cells and hyperthermia1080 chondrosarcoma cancer cells in combination with radiation, cisplatin and/or a PARPi on clonogenic cell survival, cell cycle distribution and the induction and repair of DNA double-strand breaks. We found that hyperthermia in combination with radiation or cisplatin induces an increase in double-strand breaks and cell death, up to 10-fold in IDH1MUT cancer cells compared to IDH1 wild-type cells. This vulnerability was abolished by the IDH1MUT inhibitor AGI-5198 and was further increased by the PARPi. In conclusion, our study shows that IDH1MUT cancer cells are sensitized to hyperthermia in combination with irradiation or cisplatin and a PARPi. Therefore, hyperthermia may be an efficacious sensitizer to cytotoxic therapies in tumors where the clinical application of hyperthermia is feasible, such as IDH1MUT chondrosarcoma of the extremities.

Loss of FBXW7 Correlates with Increased IDH1 Expression in Glioma and Enhances IDH1-Mutant Cancer Cell Sensitivity to Radiation.

F-box and WD repeat domain containing 7 (FBXW7) is a substrate receptor of the ubiquitin ligase SKP1-Cullin1-F-box complex and a potent tumor suppressor that prevents unregulated cell growth and tumorigenesis. However, little is known about FBXW7-mediated control of cell metabolism and related functions in cancer therapy. Here, we report that FBXW7 expression inversely correlates with the expression levels of the key metabolic enzyme isocitrate dehydrogenase 1 (IDH1) in patients with glioma and public glioma datasets. Deletion of FBXW7 significantly increased both wild-type (WT) and mutant IDH1 expression, which was mediated by blocking degradation of sterol regulatory element binding protein 1 (SREBP1). The upregulation of neomorphic mutant IDH1 by FBXW7 deletion stimulated production of the oncometabolite 2-hydroxyglutarate at the expense of increasing pentose phosphate pathway activity and NADPH consumption, limiting the buffering ability against radiation-induced oxidative stress. In addition, FBXW7 knockout and IDH1 mutations induced nonhomologous end joining and homologous recombination defects, respectively. In vitro and in vivo, loss of FBXW7 dramatically enhanced the efficacy of radiation treatment in IDH1-mutant cancer cells. Taken together, this work identifies FBXW7 deficiency as a potential biomarker representing both DNA repair and metabolic vulnerabilities that sensitizes IDH1-mutant cancers to radiotherapy. SIGNIFICANCE: Deficiency of FBXW7 causes defects in DNA repair and disrupts NADPH homeostasis in IDH1-mutant glioma cells, conferring high sensitivity to radiotherapy.

Vulnerability of IDH1-Mutant Cancers to Histone Deacetylase Inhibition via Orthogonal Suppression of DNA Repair.

Exploitation of DNA repair defects has enabled major advances in treating specific cancers. Recent work discovered that the oncometabolite 2-hydroxyglutarate (2-HG), produced by neomorphic isocitrate dehydrogenase 1/2 (IDH1/2) mutations, confers a homology-directed repair (HDR) defect through 2-HG-induced histone hypermethylation masking HDR signaling. Here, we report that IDH1-mutant cancer cells are profoundly sensitive to the histone deacetylase inhibitor (HDACi) vorinostat, by further suppressing the residual HDR in 2-HG-producing cells. Vorinostat downregulates repair factors BRCA1 and RAD51 via disrupted E2F-factor regulation, causing increased DNA double-strand breaks, reduced DNA repair factor foci, and functional HDR deficiency even beyond 2-HG's effects. This results in greater cell death of IDH1-mutant cells and confers synergy with radiation and PARPi, both against cells in culture and patient-derived tumor xenografts. Our work identifies HDACi's utility against IDH1-mutant cancers, and presents IDH1/2 mutations as potential biomarkers to guide trials testing HDACi in gliomas and other malignancies. IMPLICATIONS: IDH1-mutant cells show profound vulnerability to HDACi treatment, alone and with PARPi and radiation, via HDR suppression, presenting IDH1/2 mutations as biomarkers for HDACi use in gliomas and other malignancies.

A Phase Ib Clinical Trial of Metformin and Chloroquine in Patients with IDH1-Mutated Solid Tumors.

Simple SummaryMutations in the isocitrate dehydrogenase 1 (IDH1) gene occur in high-grade chondrosarcoma, high-grade glioma and intrahepatic cholangiocarcinoma. Due to the lack of effective treatment options, these aggressive types of cancer have a dismal outcome. The metabolism of IDH1-mutated cancer cells is reprogrammed in order to produce the oncometabolite D-2-hydroxyglutarate (D-2HG). In this clinical trial, we used the oral antidiabetic drug metformin and the oral antimalarial drug chloroquine to disrupt the vulnerable metabolism of IDH1-mutated solid tumors. We found that the combination regimen of metformin and chloroquine is well tolerated, but the combination did not induce a clinical response in this patient population. Secondly, we confirmed the clinical usefulness of D/L-2HG ratios in serum as a biomarker and the ddPCR-facilitated detection of an IDH1 mutation in circulating DNA from peripheral blood.Background: Mutations in isocitrate dehydrogenase 1 (IDH1) occur in 60% of chondrosarcoma, 80% of WHO grade II-IV glioma and 20% of intrahepatic cholangiocarcinoma. These solid IDH1-mutated tumors produce the oncometabolite D-2-hydroxyglutarate (D-2HG) and are more vulnerable to disruption of their metabolism. Methods: Patients with IDH1-mutated chondrosarcoma, glioma and intrahepatic cholangiocarcinoma received oral combinational treatment with the antidiabetic drug metformin and the antimalarial drug chloroquine. The primary objective was to determine the occurrence of dose-limiting toxicities (DLTs) and the maximum tolerated dose (MTD). Radiological and biochemical tumor responses to metformin and chloroquine were investigated using CT/MRI scans and magnetic resonance spectroscopy (MRS) measurements of D-2HG levels in serum. Results: Seventeen patients received study treatment for a median duration of 43 days (range: 7–74 days). Of twelve evaluable patients, 10 patients discontinued study medication because of progressive disease and two patients due to toxicity. None of the patients experienced a DLT. The MTD was determined to be 1500 mg of metformin two times a day and 200 mg of chloroquine once a day. A serum D/L-2HG ratio of ≥4.5 predicted the presence of an IDH1 mutation with a sensitivity of 90% and a specificity of 100%. By utilization of digital droplet PCR on plasma samples, we were able to detect tumor-specific IDH1 hotspot mutations in circulating tumor DNA (ctDNA) in investigated patients. Conclusion: Treatment of advanced IDH1-mutated solid tumors with metformin and chloroquine was well tolerated but did not induce a clinical response in this phase Ib clinical trial.

Blockade of Glutathione Metabolism in IDH1-Mutated Glioma.

Mutations in genes encoding isocitrate dehydrogenases (IDH) 1 and 2 are common cancer-related genetic abnormalities. Malignancies with mutated IDHs exhibit similar pathogenesis, metabolic pattern, and resistance signature. However, an effective therapy against IDH1-mutated solid tumor remains unavailable. In this study, we showed that acquisition of IDH1 mutation results in the disruption of NADP+/NADPH balance and an increased demand for glutathione (GSH) metabolism. Moreover, the nuclear factor erythroid 2-related factor 2 (Nrf2) plays a key protective role in IDH1-mutated cells by prompting GSH synthesis and reactive oxygen species scavenging. Pharmacologic inhibition of the Nrf2/GSH pathway via brusatol administration exhibited a potent tumor suppressive effect on IDH1-mutated cancer in vitro and in vivo Our findings highlight a possible therapeutic strategy that could be valuable for IDH1-mutated cancer treatment.

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

Abstract 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.

EXTH-03. TRIPTOLIDE, A NOVEL THERAPEUTIC AGENT FOR IDH1-MUTATED GLIOMA

Abstract BACKGROUND Isocitrate dehydrogenase (IDH1/2) mutations are common genetic abnormalities in human malignancies, which result in neomorphic enzyme activity that catalyzes 2-hydroxyglutarate (2-HG) production. While IDH mutations are recognized as critical cancer-associated genetic changes, the therapeutic options for IDH-mutated cancers remain limited. METHODS In the present study, we investigated the reactive oxygen species (ROS) scavenging pathways in patient-derived IDH1-mutated cells. Further, we investigated the protective role of glutathione de novo synthesis for IDH1-mutated cancer cells. Finally, we evaluated triptolide, a diterpenoid epoxide derived from Tripterygium wilfordii, as an experimental therapeutic for IDH1-mutated cells and xenografts. RESULTS We discovered that the neomorphic activity of IDH1 mutant enzyme triggers metabolic depletion and a substantial elevated burden of ROS scavenging in cancer cells. The nuclear factor erythroid 2-related factor 2 (NRF2)-guided antioxidant pathway plays a key role in maintaining redox homeostasis for IDH1-mutated cells. Triptolide serves as a potent inhibitor of NRF2 through enhancing the NRF2 ubiquitination and subsequently proteasomal degradation. Additionally, triptolide compromises the de novo synthesis of glutathione via suppression of NRF2-guided transcription of SLC7A11, which encodes cystine/glutamate transporter (xCT). Reduced availability of glutathione results in overwhelming oxidative damage in DNA and lipid, which translates into severe cytotoxicity and reduced xenograft expansion of IDH1-mutated cells. CONCLUSION Overall our findings highlight triptolide as a valuable synthetic lethality approach for IDH1-mutated malignancies by targeting NRF2-guided redox homeostasis.

Abstract 875: Targeting Nrf2 driven glutathione de novo synthesis as a novel strategy to suppresses IDH1-mutated glioma

Abstract Background: Isocitrate dehydrogenase (IDH) mutation frequently occurs in low grade glioma and secondary glioblastoma, characterizing by the abnormally catalyzation of alpha-ketoglutarate (α-KG) to D-2-hydroxyglutarate (D-2-HG), which induces CpG island methylator phenotype, as well as metabolic reprogramming and high reactive oxygen species (ROS) generation. Our previous data showed that nuclear factor-erythroid 2-related factor 2 (Nrf2) plays a crucial role in maintaining redox homeostasis of IDH1-mutated glioma cells, while the detail mechanism remains elusive. Our recent data showed that glutathione de novo synthesis is governed by Nrf2, which makes great contribution to ROS scavenging in IDH1-mutated tumors and could serve as a potential therapeutic target. Methods: In this study, we explored the important role of glutathione de novo synthetic pathway in maintaining ROS homeostasis by small RNA interference of key enzymes GCLC, GCLM and SLC7A11. We also investigated the correlation between Nrf2 and glutathione de novo synthetic pathway by Chromatin Immunoprecipitation. We further investigated the therapeutic value of Nrf2 inhibitor, Brusatol, in IDH1-mutated cancer both in vitro and in vivo. Results: Our data showed that IDH1 mutation cells exhibit high level steady-state of ROS generation and detoxification. Prolonged Nrf2 activity enhanced transcriptional activity of key enzymes in glutathione de novo synthesis, such as GCLC, GCLM and SLC7A11. Targeting Nrf2 using Brusatol suppressed glutathione synthesis in IDH1-mutated cells, resulted in cytotoxic effect and suppressed xenograft growth in vivo. Conclusions: IDH1-mutated glioma highly depends on Nrf2 activity to maintain ROS homeostasis. Enhanced glutathione de novo synthesis is an important mechanism that governed by Nrf2 and plays critical role in ROS scavenging. Targeting ROS scavenging might be a novel approach to treat gliomas with IDH1 mutation. Citation Format: Yang Liu, Di Yu, Sabrina Cai, Chunzhang Yang. Targeting Nrf2 driven glutathione de novo synthesis as a novel strategy to suppresses IDH1-mutated glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 875.

Targeting IDH1-Mutated Malignancies with NRF2 Blockade.

Neomorphic IDH1 mutations disrupt the redox balance by promoting reactive oxygen species (ROS) production. However, the mechanism by which IDH1-mutant cells maintain ROS homeostasis remains elusive. It is also not known whether reprogrammed ROS homeostasis establishes targetable vulnerability in IDH1-mutated cancers. We investigated ROS homeostasis in wild-type (GSC827, GSC923, GSC627, and GSC711) and IDH1-mutated cells (IDH1R132C- and IDH1R132H-transduced U87, U251; MGG152, and TS603 cells). We analyzed the stability and transcriptional activity of NRF2 in IDH1-mutated cells. The oxidative DNA damage was analyzed using NRF2-targeting small interfering RNA. Moreover, we evaluated the effect of the NRF2 inhibitor brusatol in an IDH1-mutated subcutaneous xenograft nude mouse model (control group, n = 5; brusatol-treated group, n = 6). All statistical tests were two-sided. We showed that IDH1-mutated cells develop a dependency on the NRF2 antioxidative pathway. Genetic or pharmacologic blockade of NRF2 not only disrupted ROS homeostasis (mean [SD] ROS levels increased by 317 [42.1]%, P = .001, in IDH1R132C and by 286. 5 [48.7]%, P = .003, in IDH1R132H cells) but also enhanced oxidative DNA damage and decreased proliferation of IDH1-mutated cells. Brusatol selectively suppressed IDH1-mutated cancer progression in vivo (mean [SD] final tumor volume was 761.6 [391.6] mm3 in the control and 246.2 [215] mm3 in the brusatol-treated group, P = .02). IDH1 mutation reprograms ROS homeostasis in cancer cells, which leads to dependency on the NRF2 antioxidant pathway for ROS scavenging. NRF2 blockade might be a novel therapeutic approach to treat malignancies with IDH1 mutation.

RNA-Binding Protein HuR Regulates Both Mutant and Wild-Type IDH1 in IDH1-Mutated Cancer.

Isocitrate dehydrogenase 1 (IDH1) is the most commonly mutated metabolic enzyme in human malignancy. A heterozygous genetic alteration, arginine 132, promotes the conversion of α-ketoglutarate to D-2-hydroxyglutarate (2-HG). Although pharmacologic inhibitors of mutant IDH1 are promising, resistance mechanisms to targeted therapy are not understood. Additionally, the role of wild-type IDH1 (WT.IDH1) in cancer requires further study. Recently, it was observed that the regulatory RNA-binding protein, HuR (ELAVL1), protects nutrient-deprived cancer cells without IDH1 mutations, by stabilizing WT.IDH1 transcripts. In the present study, a similar regulatory effect on both mutant (Mut.IDH1) and WT.IDH1 transcripts in heterozygous IDH1-mutant tumors is observed. In ribonucleoprotein immunoprecipitation assays of IDH1-mutant cell lines, wild-type and mutant IDH1 mRNAs each bound to HuR. Both isoforms were profoundly downregulated at the mRNA and protein levels after genetic suppression of HuR (siRNAs or CRISPR deletion) in HT1080 (R132C IDH1 mutation) and BT054 cells (R132H). Proliferation and invasion were adversely affected after HuR suppression and metabolomic studies revealed a reduction in Pentose Phosphate Pathway metabolites, nucleotide precursors, and 2-HG levels. HuR-deficient cells were especially sensitive to stress, including low glucose conditions or a mutant IDH1 inhibitor (AGI-5198). IDH1-mutant cancer cells were rescued by WT.IDH1 overexpression to a greater extent than Mut.IDH1 overexpression under these conditions. This study reveals the importance of HuR's regulation of both mutant and wild-type IDH1 in tumors harboring a heterozygous IDH1 mutation with implications for therapy. IMPLICATIONS: This study highlights the HuR-IDH1 (mutant and wild-type IDH1) regulatory axis as a critical, actionable therapeutic target in IDH1-mutated cancer, and incomplete blockade of the entire HuR-IDH1 survival axis would likely diminish the efficacy of drugs that selectively target only the mutant isoenzyme.

Abstract 5429: Targeting Nrf2 anti-oxidative pathway as a novel strategy to suppress IDH1-mutated cancer

Abstract Background: Reactive oxygen species are recently recognized as a second messenger that affects many aspects in cell biology. In cancer cells, ROS has been proof closely related to metabolic reprogramming, tumor proliferation, progression and metastasis. In tumors with isocitrate dehydrogenase (IDH) mutations, the neomorphic enzyme results in unusual accumulation of ROS in cancer cells, suggesting distinctive vulnerabilities may be established in these types of cancer. However, the biologic function of ROS in IDH1-mutated cancers remains elusive. Methods: In this study, we explored the ROS homeostasis in IDH1 mutated glioma. We investigated the correlation between ROS scavenging genes and overall survival in 530 IDH1-mutated glioma cases. Mechanistically, we focused on nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway and seek for novel therapeutic strategy by targeting ROS burden in cancer cells. We further investigated the therapeutic value of Nrf2 inhibitor, Brusatol, in IDH1 mutated cancer in vitro and in vivo. Results: We found IDH1 mutation leads to substantial reprogramming in ROS homeostasis, highlighted with prompted ROS generation and detoxification. Stronger expression of ROS scavenging gene predicts drug resistance and poor disease outcome. Enhanced Nrf2-associated scavenging pathway was found essential to maintain reasonable intracellular ROS level during cancer progression. Targeting Nrf2 scavenging pathway not only led to ROS overload, DNA/protein oxidative damage, but also reduced tumor cell proliferation and xenograft growth in vivo. Conclusions: IDH1 mutant glioma highly depend on Nrf2 scavenging pathway to maintain ROS homeostasis. Targeting ROS scavenging might be a novel approach to treat gliomas with IDH1 mutation. Citation Format: Yang Liu. Targeting Nrf2 anti-oxidative pathway as a novel strategy to suppress IDH1-mutated cancer [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 5429.

Abstract 872: IDH1-mutated cancer cells are sensitive to cisplatin and an IDH1-mutant inhibitor counteracts this sensitivity

Abstract Isocitrate dehydrogenase 1 (IDH1) is mutated in various types of human cancer and predicts improved response to treatment with irradiation or chemotherapy. Mutated IDH1 enzymes catalyze neomorphic conversion of α-ketoglutarate (α-KG) to the oncometabolite D-2-hydroxyglutarate (D-2HG) with concomitant consumption of NADPH, resulting in decreased reducing power needed for detoxification of e.g. reactive oxygen species (ROS). We report that a small-molecule inhibitor of IDH1-mutation (IDH1MUT) that is being investigated for cancer therapy may limit efficacy of treatment when co-administered with cisplatin. In the present study, we investigated whether the efficacy of treatment with cisplatin, which is a widely-used chemotherapeutic agent, induces DNA strand breaks and oxidative damage in IDH1MUT cancer cells. We found that exposure to cisplatin induced higher levels of ROS, DNA double-strand breaks, and cell death in IDH1MUT cancer cells as compared to IDH1 wild-type (IDH1WT) cancer cells. Besides these cytotoxic effects, mechanistic investigations revealed that cisplatin treatment causes dose-dependent reduction of oxygen consumption and thus the oxidative respiration in lDH1MUT cells and not in lDH1WT cells, which was accompanied by disturbed mitochondrial proteostasis and impaired mitochondrial activity. These effects were abolished by the IDH1MUT inhibitor AGI-5198 and were recapitulated by treatment with D-2HG. Thus, our study shows that altered oxidative stress responses due to a vulnerable oxidative metabolism underlie the sensitivity of IDH1MUT cancer cells to cisplatin. Furthermore, our data offer an explanation for the relatively longer survival of patients with IDH1-mutated tumors, and imply that administration of IDH1MUT inhibitors in these patients limit efficacy of cisplatin treatment. Citation Format: Mohammed Khurshed, Remco J. Molenaar, Johanna W. Wilmink, Hanneke W. van Laarhoven, Cornelis J. van Noorden. IDH1-mutated cancer cells are sensitive to cisplatin and an IDH1-mutant inhibitor counteracts this sensitivity [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 872.

Immunohistochemically detected IDH1R132H mutation is rare and mostly heterogeneous in prostate cancer

IDH1 mutations are oncogenic through induction of DNA damage and genome instability. They are of therapeutic interest because they confer increased sensitivity to radiation and cytotoxic therapy and hold potential for vaccination therapy. In this study, we analyzed more than 17,000 primary prostate cancer tissues with a mutation-specific antibody for the IDH1R132H mutation. IDH1 mutation-specific staining was found in 42 of 15,531 (0.3%) interpretable cancers. IDH1 mutation was associated with higher preoperative PSA and Gleason grade (p<0.05, each) but was unrelated to PSA recurrence. A comparison with other molecular tumor features available from earlier studies revealed that TMPRSS2-ERG fusion as well as deletion of PTEN, 5q21, 6q15, and 3p13 was less frequent in IDH1-mutated than in non-mutated cancer. Increased lethality of genetically instable, "aberration-rich" cancer cells in the presence of IDH1 mutations could possibly explain this observation. Heterogeneity analysis revealed a homogeneous mutation in only 1 of 16 IDH1-mutated cancers. This high degree of heterogeneity may profoundly limit therapeutic targeting of IDH1 mutations in prostate cancer. The data show that 0.3% of prostate cancers have an IDH1R132H mutation and that these are mostly heterogeneous. Once specific anti-IDH1 therapy becomes reality, only a very small group of prostate cancer patients may benefit from such a treatment.

The Alkylating Chemotherapeutic Temozolomide Induces Metabolic Stress in IDH1-Mutant Cancers and Potentiates NAD+ Depletion-Mediated Cytotoxicity.

IDH1-mutant gliomas are dependent upon the canonical coenzyme NAD+ for survival. It is known that PARP activation consumes NAD+ during base excision repair (BER) of chemotherapy-induced DNA damage. We therefore hypothesized that a strategy combining NAD+ biosynthesis inhibitors with the alkylating chemotherapeutic agent temozolomide could potentiate NAD+ depletion-mediated cytotoxicity in mutant IDH1 cancer cells. To investigate the impact of temozolomide on NAD+ metabolism, patient-derived xenografts and engineered mutant IDH1-expressing cell lines were exposed to temozolomide, in vitro and in vivo, both alone and in combination with nicotinamide phosphoribosyltransferase (NAMPT) inhibitors, which block NAD+ biosynthesis. The acute time period (<3 hours) after temozolomide treatment displayed a burst of NAD+ consumption driven by PARP activation. In IDH1-mutant-expressing cells, this consumption reduced further the abnormally lowered basal steady-state levels of NAD+, introducing a window of hypervulnerability to NAD+ biosynthesis inhibitors. This effect was selective for IDH1-mutant cells and independent of methylguanine methyltransferase or mismatch repair status, which are known rate-limiting mediators of adjuvant temozolomide genotoxic sensitivity. Combined temozolomide and NAMPT inhibition in an in vivo IDH1-mutant cancer model exhibited enhanced efficacy compared with each agent alone. Thus, we find IDH1-mutant cancers have distinct metabolic stress responses to chemotherapy-induced DNA damage and that combination regimens targeting nonredundant NAD+ pathways yield potent anticancer efficacy in vivo Such targeting of convergent metabolic pathways in genetically selected cancers could minimize treatment toxicity and improve durability of response to therapy. Cancer Res; 77(15); 4102-15. ©2017 AACR.

Abstract 2675: Metabolic addiction in IDH1 mutant cancers

Abstract Introduction: Recent efforts have revealed IDH1 mutation not only results in marked accumulation of 2-hydroxyglutarate (2-HG), it generates genomic chromatin alterations, altered HIF activity and reprogrammed metabolic flux. We characterized the metabolic perturbations caused by heterozygous mutant IDH1 by comparing endogenous IDH1 mutant glioma cells treated with direct inhibitors of mutant IDH1 (IDH1i) to control cells without treatment, with the overall aim of identifying novel metabolic therapeutic targets. Experimental Procedures: We tested the effect of IDH1i on the in vitro and in vivo phenotype of a panel of patient-derived endogenous IDH1 mutant solid cancer cells (including gliomas, melanoma, and sarcomas). We then assessed the effect of IDH1i on the metabolome of endogenous IDH1 mutant glioma cells using liquid chromatography-mass spectrometry. We further investigated specifically perturbed metabolic pathways using lentiviral knockdown and overexpression systems. Results: We found that IDH1i exposure and the resulting 2-HG depletion had a mixed effect in 12 endogenous mutant IDH1 lines studied both in vitro or in vivo, including an orthotopic glioma xenograft model. For 10 of 12 lines, IDH1i treatment had no demonstrable effect on proliferation or survival, while 2 lines displayed growth inhibition after IDH1i treatment. However, no significant changes were detected in the genomic DNA methylation profiles or the global levels of histone tail marks including H3K4me3, H3K9me2, H3K9me3 and H3K27me3 in IDH1 mutant glioma lines, even after inhibition of mutant IDH1 for 12 months in vitro. Broader metabolite profiling revealed that inhibition of mutant IDH1 significantly altered levels of the canonical metabolite NAD+. We tested the effect of NAD+ depletion using NAD+ biosynthesis inhibitors, and found that endogenously mutant IDH1 cells were highly dependent on NAD+ for survival, whereas proliferation and survival of IDH1/2 wild-type cancer cells were unaffected by NAD+ depletion. Using an inducible mutant IDH1 expression system we discovered that mutant IDH1 reduced intracellular NAD+ levels, rendering mutant IDH1 cells susceptible to further NAD+ depletion. Lack of sufficient NAD+ induced metabolic crisis with reduced ATP levels in IDH1 mutant cells, triggering the intracellular energy sensor AMPK and autophagy. In vivo, NAD+ depletion significantly extended the survival of mice bearing IDH1 mutant xenograft tumors, including intracerebral gliomas. Conclusions: Although most IDH1 mutant cell lines derived from solid cancers were resistant to direct IDH1 inhibition, a subset of IDH1 mutant cancers were found to be sensitive. Mutant IDH1 reprograms metabolism and renders cancer cells highly dependent on NAD+ for survival. This metabolic addiction presents a potential opportunity for metabolically targeted therapeutic development. Citation Format: Andrew S. Chi, Kensuke Tateishi, Wakimoto Hiroaki, Tracy T. Batchelor, Anthony J. Iafrate, Daniel P. Cahill. Metabolic addiction in IDH1 mutant cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2675.

Abstract 1847: The mRNA-binding protein HuR, regulates mutant and wild type IDH1 expression in IDH1-mutated cancer

Abstract Introduction: Isocitrate dehydrogenase 1 (IDH1) is mutated in various types of human cancers, predominantly an arginine to histidine amino acid change at codon 132. This structural alteration drives the catalysis of α-ketoglutarate to the oncometabolite D-2-hydroxyglutarate (2HG), which enhances DNA and protein hypermethylation and cellular dedifferentiation. Pharmacologic inhibitors of the mutant IDH1 protein show promise in clinical trials, yet the regulation of IDH1 has not been fully elucidated. We recently discovered in wild type IDH1 tumors that the regulatory RNA-binding and stress response protein, HuR (ELAVL1), protects cancer cells under nutrient deprivation by regulating the expression of core metabolic enzymes, including IDH1. We mapped the regulatory HuR binding site on the IDH1 transcript to the 3’-untranslated region. Since wild type and mutant IDH1 alleles both contain this binding sequence, we hypothesize that HuR is an important regulator of both isozymes and is biologically important in mutant IDH1 tumors. Methods: HuR expression was suppressed by siRNA in a fibrosarcoma cell line (HT-1080) harboring a natural heterozygous IDH1 mutation and cell viability was determined by PicoGreen and Trypan blue exclusion assays. Sensitivity to pharmacologic inhibition of the mutant IDH1 protein was assessed. Sanger sequencing and mRNP-IP were performed to determine HuR's impact on the expression of each IDH1 allele. To further characterize the post-transcriptional regulation of IDH1 by HuR, CRISPR/CAS 9 editing of the HuR gene was performed. Results: Sanger sequencing of IDH1 after depletion of HuR in HT1080 cells, as well as after HuR mRNP-IP, revealed that HuR regulates both the mutant and wild type IDH1. Drug sensitivity assays to a mutant IDH1 inhibitor (AGI-5198) under varying glucose concentrations revealed glucose deprivation to be a novel driver of chemo-resistance. However, HuR silencing abrogated HT1080 resistance to AGI-5198 under these conditions. Targeted knockout of HuR using the CRISPR/CAS9 system resulted in potent suppression of mutant and wild type IDH1, at both the mRNA and protein levels when compared to CRISPR/Cas9 control. Conclusions: These findings reveal that harsh metabolic conditions present in the tumor microenvironment induce chemo-resistance in an IDH1 mutant cell line to a mutant IDH1 inhibitor, in an HuR dependent manner. Moreover, both mutant and wild type IDH1 alleles are potently regulated by HuR. Therapeutic strategies that target the HuR-IDH1 axis and block this resistance mechanism may enhance the efficacy of mutant IDH1 inhibitors for relevant tumors. Citation Format: Mahsa Zarei, Shruti Lal, Nicole C. Mambelli-Lisboa, Edwin Cheung, Saswati N. Chand, Charles J. Yeo, Jonathan R. Brody, Jordan M. Winter. The mRNA-binding protein HuR, regulates mutant and wild type IDH1 expression in IDH1-mutated cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1847.

Extreme Vulnerability of IDH1 Mutant Cancers to NAD+ Depletion

Heterozygous mutation of IDH1 in cancers modifies IDH1 enzymatic activity, reprogramming metabolite flux and markedly elevating 2-hydroxyglutarate (2-HG). Here, we found that 2-HG depletion did not inhibit growth of several IDH1 mutant solid cancer types. To identify other metabolic therapeutic targets, we systematically profiled metabolites in endogenous IDH1 mutant cancer cells after mutant IDH1 inhibition and discovered aprofound vulnerability to depletion of the coenzyme NAD+. Mutant IDH1 lowered NAD+ levels by downregulating the NAD+ salvage pathway enzyme nicotinate phosphoribosyltransferase (Naprt1), sensitizing to NAD+ depletion via concomitant nicotinamide phosphoribosyltransferase (NAMPT) inhibition. NAD+ depletion activated the intracellular energy sensor AMPK, triggered autophagy, and resulted in cytotoxicity. Thus, we identify NAD+ depletion as a metabolic susceptibility of IDH1 mutant cancers.

Radioprotection of IDH1-Mutated Cancer Cells by the IDH1-Mutant Inhibitor AGI-5198.

Isocitrate dehydrogenase 1 (IDH1) is mutated in various types of human cancer to IDH1(R132H), a structural alteration that leads to catalysis of α-ketoglutarate to the oncometabolite D-2-hydroxyglutarate. In this study, we present evidence that small-molecule inhibitors of IDH1(R132H) that are being developed for cancer therapy may pose risks with coadministration of radiotherapy. Cancer cells heterozygous for the IDH1(R132H) mutation exhibited less IDH-mediated production of NADPH, such that after exposure to ionizing radiation (IR), there were higher levels of reactive oxygen species, DNA double-strand breaks, and cell death compared with IDH1 wild-type cells. These effects were reversed by the IDH1(R132H) inhibitor AGI-5198. Exposure of IDH1 wild-type cells to D-2-hydroxyglutarate was sufficient to reduce IDH-mediated NADPH production and increase IR sensitivity. Mechanistic investigations revealed that the radiosensitivity of heterozygous cells was independent of the well-described DNA hypermethylation phenotype in IDH1-mutated cancers. Thus, our results argue that altered oxidative stress responses are a plausible mechanism to understand the radiosensitivity of IDH1-mutated cancer cells. Further, they offer an explanation for the relatively longer survival of patients with IDH1-mutated tumors, and they imply that administration of IDH1(R132H) inhibitors in these patients may limit irradiation efficacy in this setting.