Isocitrate Dehydrogenase 1 Expression Research Articles

Proteomic Profiling Identifies Predictive Signatures for Progression Risk in Patients with Advanced-Stage Follicular Lymphoma.

Background: Follicular lymphoma (FL) is characterized by an indolent nature and generally favorable prognosis, yet poses a particular clinical challenge, since disease progression is observed in a notable subset of patients. Currently, it is not possible to anticipate which patients will be at risk of progression, highlighting the need for reliable predictive biomarkers that can be detected early in the disease. Methods: We applied tandem-mass-tag labelled nano-liquid chromatography tandem mass spectrometry (nLC-MS/MS) on 48 diagnostic formalin-fixed, paraffin-embedded tumor samples from patients with advanced-stage FL. Of these, 17 experienced subsequent progression (subsequently-progressing, sp-FL) while 31 did not (non-progressing, np-FL). Results: We identified 99 proteins that were significantly differentially expressed between sp-FL samples and np-FL samples (p < 0.05; log2-fold changes between 0.2 and -1.3). Based on this subset of proteins, we classified patients into high-risk and low-risk subgroups using unsupervised machine learning techniques. Pathway analyses of the identified proteins revealed aberrancies within the immune system and cellular energy metabolism. In addition, two proteins were selected for immunohistochemical evaluation, namely stimulator of interferon genes 1 (STING1) and isocitrate dehydrogenase 2 (IDH2). Notably, IDH2 retained significantly lower expression levels in sp-FL samples compared with np-FL samples (p = 0.034). Low IDH2 expression correlated with shorter progression-free survival (PFS, p = 0.020). Conclusions: This study provides evidence for some of the biological mechanisms likely to be involved in FL progression and, importantly, identifies potential predictive biomarkers for improvement of risk stratification up-front at time of FL diagnosis.

IDH2 regulates macrophage polarization and tumorigenesis by modulating mitochondrial metabolism in macrophages

BackgroundTargeting the tumor microenvironment represents an emerging therapeutic strategy for cancer. Macrophages are an essential part of the tumor microenvironment. Macrophage polarization is modulated by mitochondrial metabolism, including oxidative phosphorylation (OXPHOS), the tricarboxylic acid (TCA) cycle, and reactive oxygen species content. Isocitrate dehydrogenase 2 (IDH2), an enzyme involved in the TCA cycle, reportedly promotes cancer progression. However, the mechanisms through which IDH2 influences macrophage polarization and modulates tumor growth remain unknown.MethodsIn this study, IDH2-deficient knockout (KO) mice and primary cultured bone marrow-derived macrophages (BMDMs) were used. Both in vivo subcutaneous tumor experiments and in vitro co-culture experiments were performed, and samples were collected for analysis. Western blotting, RNA quantitative analysis, immunohistochemistry, and flow cytometry were employed to confirm changes in mitochondrial function and the resulting polarization of macrophages exposed to the tumor microenvironment. To analyze the effect on tumor cells, subcutaneous tumor size was measured, and growth and metastasis markers were identified.ResultsIDH2-deficient macrophages co-cultured with cancer cells were found to possess increased mitochondrial dysfunction and fission than wild-type BMDM. Additionally, the levels of M2-associated markers decreased, whereas M1-associated factor levels increased in IDH2-deficient macrophages. IDH2-deficient macrophages were predominantly M1. Tumor sizes in the IDH2-deficient mouse group were significantly smaller than in the wild-type mouse group. IDH2 deficiency in macrophages was associated with inhibited tumor growth and epithelial–mesenchymal transition.ConclusionsOur findings suggest that IDH2 deficiency inhibits M2 macrophage polarization and suppresses tumorigenesis. This study underlines the potential contribution of IDH2 expression in macrophages and tumor microenvironment remodeling, which could be useful in clinical cancer research.

Nanographene Oxide Promotes Angiogenesis by Regulating Osteoclast Differentiation and Platelet-Derived Growth Factor Secretion.

An imbalanced system of angiogenesis-osteoblasts-osteoclasts is regarded as the main factor in bone remodeling dysfunction diseases or osseointegration loss. Osteoclast precursors are the key cells that accelerate bone-specific angiogenesis and maintain normal osteoblast and osteoclast function. Graphene oxide is an effective scaffold surface modification agent with broad application prospects in bone tissue engineering. However, the effect of graphene oxide on the interaction between osteoclasts and angiogenesis has not yet been elucidated. In this study, a rat calvarial defect model was established and treated with an electrochemically derived nanographene oxide (ENGO) hydrogel. Higher angiogenesis and platelet-derived growth factor (PDGF) B in preosteoclasts were observed in the ENGO group compared with that in the control group. Moreover, in vitro experiments demonstrate the efficacy of ENGO in substantially reducing the expression of the receptor activator of nuclear factor-kappaB ligand (RANKL)-induced osteoclast-associated markers and inhibiting bone resorption activity. Additionally, ENGO enhances the secretion of the osteoclast-derived coupling factor PDGF-BB and promotes angiogenesis. Our investigation revealed the crucial role of isocitrate dehydrogenase 1 (IDH1) in the ENGO-mediated regulation of osteoclast differentiation and PDGF-BB secretion. The decreased expression of IDH1 reduces the level of histone lysine demethylase 7A (KDM7A) and subsequently increases the H3K9me2 level in the cathepsin K promoter region. In summary, we found that ENGO promotes angiogenesis by inhibiting the maturity of RANKL-induced osteoclasts and enhancing PDGF-BB secretion. These results indicate that ENGO holds promise for the application in fostering osteoclast-endothelial cell crosstalk, providing an effective strategy for treating bone resorption and osteoclast-related bone loss diseases.

RIOK3 sustains colorectal cancer cell survival under glucose deprivation via an HSP90α-dependent pathway

Glucose oxidation via the pentose phosphate pathway serves as the primary cellular mechanism for generating nicotinamide adenine dinucleotide phosphate (NADPH). The central regions of solid tumors typically experience glucose deficiency, emphasizing the need for sustained NADPH production crucial to tumor cell survival. This study highlights the crucial role of RIOK3 in maintaining NADPH production and colorectal cancer (CRC) cell survival during glucose deficiency. Our findings revealed upregulated RIOK3 expression upon glucose deprivation, with RIOK3 knockout significantly reducing cancer cell survival. Mechanistically, RIOK3 interacts with heat shock protein 90α (HSP90α), a chaperone integral to various cellular processes, thereby facilitating HSP90α binding to isocitrate dehydrogenase 1 (IDH1). This interaction further upregulates IDH1 expression, enhancing NADPH production and preserving redox balance. Furthermore, RIOK3 inhibition had no discernible effect on intracellular NADPH levels and cell death rates in HSP90α-knockdown cells. Collectively, our findings suggest that RIOK3 sustains colon cancer cell survival in low-glucose environments through an HSP90α-dependent pathway. This highlights the significance of the RIOK3–HSP90α–IDH1 cascade, providing insights into potential targeted therapeutic strategies for CRC in metabolic stress conditions.

A novel NR4A2-HuR axis promotes pancreatic cancer growth and tumorigenesis that is inhibited by NR4A2 antagonists.

Pancreatic ductal adenocarcinoma (PDAC) patients' express higher levels of the orphan Nuclear Receptor 4A2 (NR4A2, NURR1) compared to normal pancreas and NR4A2 is a prognostic factor for patient survival. Knockdown of NR4A2 by RNA interference (RNAi) inhibited cell proliferation, invasion, and migration. RNA sequencing performed in NR4A2(+/+) and NR4A2(-/-) MiaPaCa2 cells demonstrated that NR4A2 played a significant role in cellular metabolism. Human antigen R (HuR) and isocitrate dehydrogenase 1 (IDH1) were identified as NR4A2 target genes. HuR is a pro-oncogenic RNA binding protein and silencing of HuR by RNAi significantly downregulated expression of NR4A2. Expression of HuR and IDH1 were significantly downregulated after treatment with NR4A2 inverse agonist, 1,1-bis(3'-indolyl)-1-(p-chlorophenyl)methane resulting in significant inhibition of tumor growth in an athymic nude mouse xenograft model. This study demonstrates that NR4A2 and HuR regulate genes and signaling pathways that enhance tumorigenesis and targeting NR4A2 and HuR expression with an NR4A2 inverse agonist represents a novel regimen for treating PDAC.

THE EMERGING ROLE OF IDH2-MEDIATED MITOPHAGY AND MTUPR IN ATHEROSCLEROSIS

Objective: Mitochondrial dysfunction is a risk factor for vascular disease by overexpressing ROS caused by some stimuli in mitochondria which causes oxidative stress and enhances vascular inflammatory response. Isocitrate dehydrogenase 2 (IDH2) is NADP+ dependent mitochondrial enzyme and an antioxidant enzyme that produces NADPH in the antioxidant system. Mitophagy and mitochondrial Unfolding Protein Response (mtUPR) are internal defense mechanism in mitochondria. In this study, we investigated whether IDH2 knockdown causes mitochondrial dysfunction then Mitophagy and mtUPR in vitro in HUVECs and in vivo in IDH2 knock out mice. Design and method: We examined expression of mitophagy and mtUPR-related gene in IDH2-deficient human umbilical vein endothelial cells (HUVECs) and its role in mitophagy and mtUPR in the endothelial cell and IDH2 KO animal tissues. Mitophagy and mtUPR were measured using the western blotting and qPCR. Results: We showed that knockdown of IDH2 expression induced depolarization of mitochondrial membrane potential (MMP). Mitochondrial dynamics is mitochondrial fusion and fission. Knockdown of IDH2 increased Drp1 (fission protein) and mfn1 (fusion protein) compared with Tom20 (control). IDH2 deficiency increase Mitophagy related protein PINK-1 and Parkin expression and mRNA level (PINK-1, Parkin, BNIP3, NIX, FUNDC-1). Moreover, knockdown of IDH2 induced mtUPR mRNA level (USP30, Clpp) in vitro. In addition, IDH2 deficiency increases mtUPR mRNA level and decreases PINK-1 and Parkin protein expression in vivo. Conclusions: Our data show that IDH2 deficiency induces mitochondrial dysfunction and then Mitophagy and mtUPR expression in endothelial cells. These findings provide novel strategy for the development of therapeutic agents for restoring mitochondrial and endothelial function.

Abstract 3701: Targeting wild-type IDH1 enhances chemosensitivity in pancreatic cancer

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer mortality in the United States. The poor prognosis is in part due to development of chemotherapy resistance, despite improvements in multiagent regimens. Our previous work demonstrated that oxidative stress plays an important role in drug resistance. Wild-type isocitrate dehydrogenase 1 (IDH1) is an important enzyme that generates cytosolic NADPH to maintain redox homeostasis and protect cancer cells from oxidative damage. Additionally, we demonstrated that ivosidenib (AG-120), an FDA-approved mutant IDH1 inhibitor, is actually a potent inhibitor of wild-type IDH1, under low magnesium and nutrient levels that are present in the tumor microenvironment. Methods: We evaluated IDH1 expression in PDAC using The Cancer Genome Atlas (TCGA). Cell viability was assessed by Trypan blue and PicoGreen in drug combination assays. Cellular reactive oxygen species (ROS) levels were determined by the DCFDA method. To further assess the therapeutic potential of AG-120 in combination with chemotherapy, tumor volume analyses were performed using patient-derived xenografts (PDX) in athymic nude mice, and survival studies were performed in C57BL/6J mice transplanted with orthotopic murine pancreatic cancer. Results: Analysis of TCGA data indicated that IDH1 is overexpressed in pancreatic cancer tumors. Treatment of MiaPaca2 and Panc1 cancer cells with 5- fluorouracil (5-FU) induced expression of wild-type IDH1 in vitro. Short-term cell viability data demonstrated that targeting IDH1 with AG-120 when combined with DNA-damaging agents (5-FU, oxaliplatin) had a synergistic effect with a positive synergy score and Bliss score greater than 1. Additionally, we assessed long-term cell survival using colony formation assays, which yielded a dramatic reduction in cell survival for both Panc1 and MiaPaCa-2 cells when 5-FU was combined with AG-120, as compared to single-agent controls. Inhibiting IDH1 impairs the ability of pancreatic cancer cells to scavenge ROS levels, enhances chemotherapy-induced apoptosis in pancreatic cancer cells via ROS-mediated damage in vitro. Both PDX tumor volume studies and overall survival analyses revealed that the combination of these AG-120 and chemotherapy synergistically enhanced anti-tumor activity and doubled the survival benefits as compared to single-agent alone. Conclusion: IDH1 plays a critical role in tumorigenesis and chemoresistance in pancreatic cancer. Our data demonstrate that IDH1 inhibition with AG-120 may enhance chemotherapy efficacy and represents an important area for future investigation in the form of clinical trials. Citation Format: Mehrdad Zarei, Omid Hajihassani, Jonathan J. Hue, Hallie J. Graor, Arian Hajihassani, Alexander W. Loftus, Luke D. Rothermel, Jordan M. Winter. Targeting wild-type IDH1 enhances chemosensitivity in pancreatic cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3701.

Targeting Mitochondrial IDH2 Enhances Antitumor Activity of Cisplatin in Lung Cancer via ROS-Mediated Mechanism

Mitochondrial isocitrate dehydrogenase 2 (IDH2) is an important metabolic enzyme in the tricarboxylic acid cycle (TCA) cycle. Our previous study showed that high expression of wild-type IDH2 promotes the proliferation of lung cancer cells. This study aims to test the potential of targeting IDH2 as a therapeutic strategy to inhibit lung cancer in vitro and in vivo. First, we analyzed the available data from the databases gene expression omnibus (GEO) database to evaluate the clinical relevance of IDH2 expression in affecting lung cancer patient survival. We then generated a stable IDH2-knockdown lung cancer cell line using a lentivirus-based method for in vitro and in vivo study. Cell growth, apoptosis, cell viability, and colony formation assays were conducted to test the sensitivity of lung cancer cells with different IDH2 expression status to cisplatin or radiation treatment in vitro. For mechanistic study, Cellular oxygen consumption and extracellular acidification rates were measured using a Seahorse metabolic analyzer, and reactive oxygen species (ROS) generation was analyzed using flow cytometry. An animal study using a xenograft tumor model was performed to further evaluate the in vivo therapeutic effect on tumor growth. We found that high IDH2 expression was associated with poor survival in lung cancer patients undergoing chemotherapy. Inhibition of IDH2 significantly enhanced the anticancer activity of cisplatin and also increased the effect of radiation against lung cancer cells. IDH2 was upregulated in cisplatin-resistant lung cancer cells, which could be sensitized by targeted inhibition of IDH2. Mechanistic study showed that abrogation of IDH2 caused only minimal changes in oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in lung cancer cells, but induced a significant increase in ROS, which rendered the cancer cells more sensitive to cisplatin. Pretreatment of lung cancer cells with the ROS scavenger N-acetyl-cysteine could partially rescue cells from the cytotoxic effect of cisplatin and IDH2 inhibition. Importantly, abrogation of IDH2 significantly increased the sensitivity of lung cancer cells to cisplatin in vivo.

IDH2, a novel target of OGT, facilitates glucose uptake and cellular bioenergy production via NF-κB signaling to promote colorectal cancer progression.

Although isocitrate dehydrogenase 2 (IDH2) mutations have been the hotspots in recent anticancer studies, the impact of wild-type IDH2 on cancer cell growth and metabolic alterations is still elusive. IDH2 expression in CRC tissues was evaluated by immunohistochemistry, and the correlation between the expression level and the patient's survival rate was analyzed. Cell functional assays included CCK8 and colony formation for cell proliferation in vitro and ectopic xenograft as in vivo experimental model for tumor progression. A targeted metabolomic procedure was performed by liquid chromatography/tandem mass spectrometry to profile the metabolites from glycolysis and tricarboxylic acid (TCA) cycle. Mitochondrial function was assessed by measuring cellular oxygen consumption (OCR) and mitochondrial membrane potential (ΔΨ). Confocal microscope analysis and Western blotting were applied to detect the expression of GLUT1 and NF-κB signaling. O-GlcNAcylation and the interaction of IDH2 with OGT were confirmed by co-immunoprecipitation, followed by Western blotting analysis. IDH2 protein was highly expressed in CRC tissues, and correlated with poor survival of CRC patients. Wild-type IDH2 promoted CRC cell growth in vitro and tumor progression in xenograft mice. Overexpression of wild-type IDH2 significantly increased glycolysis and TCA cycle metabolites, the ratios of NADH/NAD+ and ATP/ADP, OCR and mitochondrial membrane potential (ΔΨ) in CRC cells. Furthermore, α-KG activated NF-κB signaling to promote glucose uptake by upregulating GLUT1. Interesting, O-GlcNAcylation enhanced the protein half-time of IDH2 by inhibiting ubiquitin-mediated proteasome degradation. The O-GlcNAc transferase (OGT)-IDH2 axis promoted CRC progression. Wild-type IDH2 reprogrammed glucose metabolism and bioenergetic production via the NF-κB signaling pathway to promote CRC development and progression. O-GlcNAcylation of IDH2 elevated the stability of IDH2 protein. And the axis of OGT-IDH2 played an essential promotive role in tumor progression, suggesting a novel potential therapeutic strategy in CRC treatment.

Cooperative Inhibitory Effect of IDH1 Mutation and ASXL1 Mutation on Normal Myeloid Differentiation

Somatic mutations in the additional sex comb-like 1, ASXL1, have been described in various types of myeloid malignancies, including myelodysplastic syndromes, chronic myelomonocytic leukemia, and acute myeloid leukemia (AML). In addition, ASXL1 mutations are frequently found in healthy population, which predispose them to not only myeloid malignancies, but also cardiovascular diseases. This condition is known as clonal hematopoiesis with intermediate potential (CHIP), although the full etiology of this preleukemic condition is not elucidated. As for AML, patients with ASXL1 mutations are known to have very poor prognosis compared to non-mutated patients. Although previous studies demonstrated that mutant ASXL1 promoted myeloid leukemogenesis via both loss-of-function and gain-of-function manners, mechanisms how ASXL1 mutations induce myeloid transformation is not fully elucidated. We analyzed publicly available datasets of AML patients, and found that isocitrate dehydrogenase 1 (IDH1) is co-mutated in 13% of AML with ASXL1. As the mechanism by which ASXL1 and IDH1 mutations cooperate to promote AML is not understood, we generated a model of AML with ASXL1 and IDH1 mutations using 32D-cl3 cells and discovered that mutant IDH1 could block myeloid differentiation only when mutant ASXL1 was present. At first, in our experiments, we retrovirally overexpressed mutant (G646WfsX12) or normal form of ASXL1 in 32D-cl3, which is a commonly used IL-3 dependent cell-line of murine myeloid precursor cell. We found that Gr.1 expression levels were decreased in these cells compared to 32D-cl3 with mutant ASXL1 (11.1% vs 26.5%, respectively; p=0.014), and that the proportion of cells in which Gr1 expression was induced by treatment with G-CSF was significantly lower (29.1% vs 54.8%, respectively; p=0.003). Next, we generated a tetracycline-inducible mutant (R132H) form of IDH1 lentiviral vector, and transfected them to these 32D-cl3 cells. We found that tetracycline-inducible mutant IDH1 inhibited G-CSF induced Gr.1 expression in the presence of mutant ASXL1 (7.1% with doxycycline vs 29.9% without doxycycline, respectively; p<0.01), while in the absence of mutant ASXL1, forced expression of mutant IDH1 could not block G-CSF induced Gr.1 expression (59.6% with doxycycline vs 59.2% without doxycycline, respectively; p=0.035). In accordance to these analyses of surface markers, we found that reduction of expression levels of CEBPβ induced by tetracycline-inducible ectopic expression of mutant IDH1 was only observed in 32D-cl3 cells with mutant ASXL1. Furthermore, we found that growth rate of 32D-cl3 cells with mutant ASXL1 and mutant IDH1 was significantly higher than those with mutant ASXL1 alone. These findings suggested that mutant IDH1 can exert its inhibitory effect of normal myeloid differentiation only when mutant ASXL1 is present. Herein, we hypothesized that mutant ASXL1 and mutant IDH1 had unknown cooperative mechanisms to suppress normal differentiation and promote leukemogenesis, and performed transcriptome analysis of the 32D-cl3 cells treated with G-CSF. Tendency toward decreased expression of genes associated with myeloid differentiation in the presence of IDH1 was only observed in cells with mutant ASXL1. Further, it was revealed that specifically dysregulated genes such as HDAC6 or KMT2A in leukemic stem cells were enriched in 32D-cl3 cells with mutant ASXL1, which suggested that mutant IDH1 could induce leukemogenesis only in the presence of ASXL1. In our study, we found that the presence of IDH1 R132H mutation in 32D-cl3 cells had an inhibitory effect on normal myeloid differentiation only in the presence of ASXL1 mutation. Transcriptome analysis was performed to explore genes dysregulated by cooperation of mutant ASXL1 and mutant IDH1. We demonstrated that there might be cooperative mechanisms between ASXL1 and IDH1 to induce differentiation and promote leukemogenesis. Our study would not only provide a new role for IDH1 mutation in ASXL1 mutated AML, but also identify a new therapeutic target for ASXL1-mutatated AML.

Differential role of Pax6 and its interaction with Shh-Gli1-IDH2 axis in regulation of glioma growth and chemoresistance.

Glioma is a major brain tumor, and the associated mortality rate is very high. Contemporary therapies provide a chance of survival for 9-12 months. Therefore, a novel approach is essential to improve the survival rate. Sonic hedgehog (Shh) cell signaling is critical for early development in various tumors. This investigation attempted to explore the potential interaction and regulation of Shh-Gli1 cell signaling in association with paired box 6 (Pax6) and isocitrate dehydrogenase 2(IDH2). The expression pattern of Shh, Gli1, Pax6, and IDH2 was examined by transcriptome analysis, immunohistochemistry, and confocal images. The results suggest the interaction of Shh-Gli1 cell signaling pathway with Pax6 and IDH2 and potential regulation. Thereafter, we performed protein-protein docking and molecular dynamic simulations (MDS) of Gli1 with Pax6 and IDH2. The results suggest differential dynamic interactions of Gli1-IDH2 and Gli1-Pax6. Gli1 knockdown downregulated the expression of Pax6 and upregulated the expression of IDH2. Moreover, Gli1 knockdown decreased the expression of the drug resistance gene MRP1. The knockdown of Pax6 gene in glioma cells downregulated the expression of Gli1 and IDH2 and promoted cell proliferation. Moreover, the efficacy of the treatment of glioma cells with temozolomide (TMZ) and Gli1 inhibitor GANT61 was higher than that of TMZ alone. MDS results revealed that the interactions of Gli1 with IDH2 were stronger and more stable than those with Pax6. Intriguingly, inhibition of Pax6 promoted glioma growth even in the presence of TMZ. However, the tumor-suppressive nature of Pax6 was altered when Gli1 was inhibited by GANT61, and it showed potential oncogenic character, as observed in other cancers. Therefore, we conclude that Pax6 interacted with IDH2 and Gli1 in glioma. Moreover, the Shh-Gli1-IDH2/Pax6 cell signaling axis provides a new therapeutic approach for inhibiting the progression of the disease and mitigating drug resistance in glioma.

Nrf2 transcriptional upregulation of IDH2 to tune mitochondrial dynamics and rescue angiogenic function of diabetic EPCs

Endothelial progenitor cells (EPCs) are reduced in number and impaired in function in diabetic patients. Whether and how Nrf2 regulates the function of diabetic EPCs remains unclear. In this study, we found that the expression of Nrf2 and its downstream genes were decreased in EPCs from both diabetic patients and db/db mice. Survival ability and angiogenic function of EPCs from diabetic patients and db/db mice also were impaired. Gain- and loss-of-function studies, respectively, showed that knockdown of Nrf2 increased apoptosis and impaired tube formation in EPCs from healthy donors and wild-type mice, while Nrf2 overexpression decreased apoptosis and rescued tube formation in EPCs from diabetic patients and db/db mice. Additionally, proangiogenic function of Nrf2-manipulated mouse EPCs was validated in db/db mice with hind limb ischemia. Mechanistic studies demonstrated that diabetes induced mitochondrial fragmentation and dysfunction of EPCs by dysregulating the abundance of proteins controlling mitochondrial dynamics; upregulating Nrf2 expression attenuated diabetes-induced mitochondrial fragmentation and dysfunction and rectified the abundance of proteins controlling mitochondrial dynamics. Further RNA-sequencing analysis demonstrated that Nrf2 specifically upregulated the transcription of isocitrate dehydrogenase 2 (IDH2), a key enzyme regulating tricarboxylic acid cycle and mitochondrial function. Overexpression of IDH2 rectified Nrf2 knockdown- or diabetes-induced mitochondrial fragmentation and EPC dysfunction. In a therapeutic approach, supplementation of an Nrf2 activator sulforaphane enhanced angiogenesis and blood perfusion recovery in db/db mice with hind limb ischemia. Collectively, these findings indicate that Nrf2 is a potential therapeutic target for improving diabetic EPC function. Thus, elevating Nrf2 expression enhances EPC resistance to diabetes-induced oxidative damage and improves therapeutic efficacy of EPCs in treating diabetic limb ischemia likely via transcriptional upregulating IDH2 expression and improving mitochondrial function of diabetic EPCs.

Abstract P3011: Nrf2 Transcriptional Upregulation Of Idh2 To Tune Mitochondrial Dynamics And Rescue Angiogenic Function Of Diabetic Epcs

Endothelial progenitor cells (EPCs) are reduced in number and impaired in function in diabetic patients. Whether and how Nrf2 regulates the function of diabetic EPCs remains unclear. In this study, we found that the expression of Nrf2 and its downstream genes were decreased in EPCs from both diabetic patients and db/db mice. Survival ability and angiogenic function of EPCs from diabetic patients and db/db mice also were impaired. Gain- and loss-of-function studies, respectively, showed that knockdown of Nrf2 increased apoptosis and impaired tube formation in EPCs from healthy donors and wild-type mice, while Nrf2 overexpression decreased apoptosis and rescued tube formation in EPCs from diabetic patients and db/db mice. Additionally, proangiogenic function of Nrf2-manipulated mouse EPCs was validated in db/db mice with hind limb ischemia. Mechanistic studies demonstrated that diabetes induced mitochondrial fragmentation and dysfunction of EPCs by dysregulating the abundance of proteins controlling mitochondrial dynamics; upregulating Nrf2 expression attenuated diabetes-induced mitochondrial fragmentation and dysfunction and rectified the abundance of proteins controlling mitochondrial dynamics. Further RNA-sequencing analysis demonstrated that Nrf2 specifically upregulated the transcription of isocitrate dehydrogenase 2 (IDH2), a key enzyme regulating tricarboxylic acid cycle and mitochondrial function. Overexpression of IDH2 rectified Nrf2 knockdown- or diabetes-induced mitochondrial fragmentation and EPC dysfunction. In a therapeutic approach, supplementation of an Nrf2 activator sulforaphane enhanced angiogenesis and blood perfusion recovery in db/db mice with hind limb ischemia. Collectively, these findings indicate that Nrf2 is a potential therapeutic target for improving diabetic EPC function. Thus, elevating Nrf2 expression enhances EPC resistance to diabetes-induced oxidative damage and improves therapeutic efficacy of EPCs in treating diabetic limb ischemia likely via transcriptional upregulation of IDH2 expression and improving mitochondrial function of diabetic EPCs.

IDH2: A novel biomarker for environmental exposure in blood circulatory system disorders.

As the risk of harmful environmental exposure is increasing, it is important to find suitable targets for the diagnosis and treatment of the diseases caused. Isocitrate dehydrogenase 2 (IDH2) is an enzyme located in the mitochondria; it plays an important role in numerous cell processes, including maintaining redox homeostasis, participating in the tricarboxylic acid cycle and indirectly taking part in the transmission of the oxidative respiratory chain. IDH2 mutations promote progression in acute myeloid leukemia, glioma and other diseases. The present review mainly summarizes the role and mechanism of IDH2 with regard to the biological effects, such as the mitophagy and apoptosis of animal or human cells, caused by environmental pollution such as radiation, heavy metals and other environmental exposure factors. The possible mechanisms of these biological effects are described in terms of IDH2 expression, reduced nicotine adenine dinucleotide phosphate content and reactive oxygen species level, among other variables. The impact of environmental pollution on human health is increasingly attracting attention. IDH2 may therefore become useful as a potential diagnostic and therapeutic target for environmental exposure-induced diseases.

Abstract 3038: IDH1 facilitates melanoma cell survival under metabolic stress

Abstract Introduction: Novel immunotherapies and targeted therapies have generated remarkable responses for patients with melanoma relative to historic treatments, but these responses are only seen in about 50% of patients. This suggests that treatment resistance is an ongoing challenge for a significant number of patients with melanoma, leaving an urgent need for improved therapeutic strategies. In our previous studies, we demonstrated that oxidative stress has an important role in drug resistance, and that wild type isocitrate dehydrogenase 1 (IDH1) is a major source of cytosolic NADPH that maintains redox homeostasis of cells under hypoxic and metabolic stress. This critical enzyme has not been thoroughly evaluated in melanoma. Herein, we explored the expression and function of IDH1 in human melanoma and the role of IDH1 in regulating melanoma metabolism. Methods: We evaluated IDH1 expression in primary and metastatic melanoma using The Cancer Genome Atlas (TCGA). We performed IDH1 knockdown by siRNA oligos, and evaluated cell viability by Trypan blue and PicoGreen assays under normal and nutrient-deprived conditions. Cellular reactive oxygen species (ROS) levels were determined by the DCFDA method. Metastatic activity of these cells was measured by transwell migration assays. In order to determine the impact of IDH1 in cellular metabolism, metabolomics profiling was performed by using LC-MS. These experiments were performed in A375 and SK-Mel 28 cell lines. Results: Analysis of TCGA data from melanoma samples showed IDH1 is highly overexpressed in primary and metastatic melanoma, and higher levels are associated with decreased progression-free survival in patients. Further, we validated that IDH1 is overexpressed in tumors by comparing normal skin tissue versus tumor samples by IHC and protein expression arrays. Silencing IDH1 impaired cell proliferation and migration (vs. control) in a nutrient-deprived microenvironment, but this effect was not seen in nutrient abundance. Metabolomics revealed that inhibiting IDH1 significantly decreased NADPH, α-ketoglutarate (αKG), and GSH levels with a corresponding increase in ROS levels and an impairment of mitochondrial function. In addition, silencing IDH1 sensitized melanoma cells to temozolomide (TMZ), a DNA-alkylating agent, as indicated by a decrease in relative cell survival compared with controls. Conclusion: IDH1 plays a critical role in tumorigenesis and chemoresistance in melanoma. Our data show that IDH1 inhibition sensitizes melanoma cells to TMZ therapy. Our study suggests that IDH1 is a potential target in melanoma as a monotherapy or in combination with existing chemotherapies. Citation Format: Mehrdad Zarei, Ali Vaziri-Gohar, Jonathan Hue, Omid Hajihassani, Erryk Katayama, Hallie Graor, Jordan Winter, Luke Rothermel. IDH1 facilitates melanoma cell survival under metabolic stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3038.

Differential metabolic requirement governed by transcription factor c-Maf dictates innate γδT17 effector functionality in mice and humans.

Cellular metabolism has been proposed to govern distinct γδ T cell effector functions, but the underlying molecular mechanisms remain unclear. We show that interleukin-17 (IL-17)–producing γδ T (γδT17) and interferon-γ (IFN-γ)–producing γδ T (γδT1) cells have differential metabolic requirements and that the rate-limiting enzyme isocitrate dehydrogenase 2 (IDH2) acts as a metabolic checkpoint for their effector functions. Intriguingly, the transcription factor c-Maf regulates γδT17 effector function through direct regulation of IDH2 promoter activity. Moreover, mTORC2 affects the expression of c-Maf and IDH2 and subsequent IL-17 production in γδ T cells. Deletion of c-Maf in γδ T cells reduces metastatic lung cancer development, suggesting c-Maf as a potential target for cancer immune therapy. We show that c-Maf also controls IL-17 production in human γδ T cells from peripheral blood and in oral cancers. These results demonstrate a critical role of the transcription factor c-Maf in regulating γδT17 effector function through IDH2-mediated metabolic reprogramming.

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.

A radiomics model based on DCE-MRI and DWI may improve the prediction of estimating IDH1 mutation and angiogenesis in gliomas

PurposeTo investigate the value of a radiomics model based on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion weighted imaging (DWI) in estimating isocitrate dehydrogenase 1 (IDH1) mutation and angiogenesis in gliomas. MethodOne hundred glioma patients with DCE-MRI and DWI were enrolled in this study (training and validation groups with a ratio of 7:3). The IDH1 genotypes and expression of vascular endothelial growth factor (VEGF) in gliomas were assessed by immunohistochemistry. Radiomics features were extracted by an open source software (3DSlicer) and reduced using Least absolute shrinkage and selection operator (Lasso). The support vector machine (SVM) model was developed based on the most useful predictive radiomics features. The conventional model was built by the selected clinical and morphological features. Finally, a combined model including radiomics signature, age and enhancement degree was established. Receiver operator characteristic (ROC) curve was implemented to assess the diagnostic performance of the three models. ResultsFor IDH1 mutation, the combined model achieved the highest area under curve (AUC) in comparison with the SVM and conventional models (training group, AUC = 0.967, 0.939 and 0.906; validation group, AUC = 0.909, 0.880 and 0.842). Furthermore, the SVM model showed good diagnostic performance in estimating gliomas VEGF expression (validation group, AUC = 0.919). ConclusionsThe radiomics model based on DCE-MRI and DWI can have a considerable effect on the evaluation of IDH1 mutation and angiogenesis in gliomas.

Correlation of immunohistochemical expression of HIF-1alpha and IDH1 with clinicopathological and therapeutic data of moroccan glioblastoma and survival analysis

IntroductionGlioblastomas are aggressive primary intracranial tumours of the central nervous system causing significant mortality and morbidity worldwide. ObjectiveThis study aims to evaluate the prognostic value of tissue expression by immunostaining of hypoxia-inducible factor (HIF-1α), isocitrate dehydrogenase 1 (IDH1), and tumour protein p53 in glioblastoma in Moroccan patients. The association of HIF-1α, IDH1, and p53 expression with the clinicopathological data and overall patient survival (OS) was also evaluated. Materials and methodsConfirmed glioblastomas were included in this study. Twenty-two tissue samples were obtained by neurosurgical intervention resulting from total resection, and subtotal resection or biopsy. Karnofsky index, histological type of tumour, and the status of IDH1, p53 protein, and HIF-1α expression by immunostaining were reported. ResultsThe majority of the patients were males (64%) with a sex ratio of 1.75. The average age was 54 ± 13. Median follow-up was 10.10 months and median overall survival was 10 months. The expression of HIF-1α was high in 10 samples (45%) and low in 12 (55%). There was a statistically significant difference in OS of 85% at 12 months for the subgroup of patients “HIF-1α negative IDH1 positive” p = 0.038, the unadjusted analysis showed that the group “HIF-1α positive, IDH1 positive” was a poor prognostic factor, the HR was 0.08 (95% CI: 0.009–0.756, p = 0.027). ConclusionPatients with negative HIF-1α expression and positive IDH1 expression have a better prognosis, suggesting that these two biomarkers may be useful in the search for new approaches for targeted therapy in glioblastoma.

IDH2 contributes to tumorigenesis and poor prognosis by regulating m6A RNA methylation in multiple myeloma.

Epigenetic alterations have been previously shown to contribute to multiple myeloma (MM) pathogenesis via DNA methylations and histone modifications. RNA methylation, a novel epigenetic modification, is required for cancer cell survival, and targeting this pathway has been proposed as a new therapeutic strategy. The extent to the N6-methyladenosine (m6A)-regulatory pathway functions in MM remains unknown. Here, we show that an imbalance of RNA methylation may underlies the tumorigenesis of MM. Mechanistically, isocitrate dehydrogenase 2 (IDH2) is highly expressed in CD138+ cells from MM and its levels appear a progressive increase in the progression of plasma cell dyscrasias. Downregulation of IDH2 increases global m6A RNA levels and reduces myeloma cell growth in vitro, decreases the burden of disease and prolongs overall survival in vivo. IDH2 regulates RNA methylation by activating the RNA demethylase FTO, which is an α-KG-dependent dioxygenase. Furthermore, IDH2-mediated FTO activation decreases the m6A level on WNT7B transcripts, then increases WNT7B expression and thus activated Wnt signaling pathway. Moreover, survival analysis indicates that the elevated expression of IDH2 predicts a poor prognosis. Higher expression of FTO is related to higher International Staging System (ISS) stage and higher Revised-ISS (R-ISS) stage of MM. Collectively, our studies reveal that IDH2 regulates global m6A RNA modification in MM via targeting RNA demethylases FTO. The imbalance of m6A methylation activates the Wnt signaling pathway by enhancing the WNT7B expression, and thus promoting tumorigenesis and progression of MM. IDH2 might be used as a therapeutic target and a possible prognostic factor for MM.