Transcriptional study of ARN8 cells treated with novel DHODH inhibitors
Ontology highlight
ABSTRACT: We have previously observed protein level changes after treating human cells with two novel inhibitors of the enzyme DHODH. This study was designed to study up to what degree these protein differences can be also observed at level of mRNA. As part of the de novo pyrimidine synthesis pathway, DHODH inhibition is expected to decrease the levels of total RNA in cells. However, some effector proteins associated with the p53 pathway are increased after treatment with these inhibitors. This study aims to answer if the observed protein differences are based on an increased transcription or due to protein stabilization.
Project description:Children with relapsed or refractory T-cell acute lymphoblastic leukemia (T-ALL) have a poor prognosis with few therapeutic options. Multiple lines of evidence point towards the enzyme dihydroorotate dehydrogenase (DHODH) as a metabolic vulnerability in dysregulated and malignant T‑cells. DHODH catalyzes the fourth step of de novo pyrimidine nucleotide synthesis (e.g., uridine, cytidine). Therefore, inhibiting DHODH via small molecule inhibitors (DHODHi) rapidly leads to the depletion of intracellular pyrimidine pools and forces cells to rely on extracellular salvage. In the absence of sufficient salvage, this intracellular nucleotide starvation results in the inhibition of DNA and RNA synthesis, cell cycle arrest, and ultimately death. T‑lymphoblasts appear to be specifically and exquisitely sensitive to nucleotide starvation following DHODHi. We have confirmed this sensitivity in vitro as well as in vivo in three murine models of T‑ALL. Additionally, we have identified that certain subsets of T-ALL seem to have an increased reliance on oxidative phosphorylation when treated with DHODHi. Through a series of metabolic assays, we show that leukemia cells, in the setting of nucleotide starvation, have changes in their mitochondrial membrane potential and may be more highly dependent on alternative fuel sources. We hope these changes point to a metabolic vulnerability that may distinguish them from normal T-cells and other normal hematopoietic cells and offer an exploitable therapeutic opportunity. The availability of clinical-grade DHODH inhibitors currently in human clinical trials speaks to the potential for rapidly advancing this work into the clinic.
Project description:The ability of cancer cells to evade immune destruction is governed by various intrinsic factors including their metabolic state. Here we demonstrate that inactivation of dihydroorotate dehydrogenase (DHODH), a pyrimidine synthesis enzyme, increases cancer cell sensitivity to T cell cytotoxicity through induction of ferroptosis. Lipidomic and metabolomic analyses revealed that DHODH inhibition reduces CDP-choline level and attenuates the synthesis of phosphocholine (PC) via the CDP-choline-dependent Kennedy pathway. To compensate this loss, there was increased synthesis from phosphatidylethanolamine via the phospholipid methylation pathway resulting in increased generation of very long chain polyunsaturated fatty acid-containing PCs. Importantly, inactivation of Dhodh in cancer cells promoted the infiltration of interferong-secreting CD8+ T cells and enhanced the anti-tumor activity of PD-1 blockade in mouse models. Our findings reveal the importance of DHODH in regulating immune evasion through a CDP-choline dependent mechanism and implicate DHODH as a promising target to improve the efficacy of cancer immunotherapies.
Project description:Neuroblastoma is an embryonal tumor which originates from neural crest progenitor cells that fail to differentiate along their predefined route to sympathetic neurons or sympatho-adrenergic adrenal cells. It is the most common extracranial tumor of childhood and accounts for 15% of all childhood cancer deaths. Especially patients suffering from high grade or relapsed neuroblastoma have poor outcome in spite of aggressive treatment regimens including autologous stem cell transplantation. Those patients are in urgent need of additional effective therapies which demands the development of targeted approaches. Dihydroorotatedehydrogenase (DHODH) is the fourth enzyme of the pyrimidine synthesis pathway which oxidizes dihydroorotate to orotate. In recent past it became a potential drug target for cancer treatment because of its keyrole in processing essential pyrimidine nucleotides. On the basis of the existing data, functional inhibition of DHODH is considered to be promising therapeutic option for several tumor entities like advanced colorectal, breast or lung-cancers. Leflunomide is an established drug in treatment of the autoimmune diseases rheumatoid arthritis and multiple sclerosis. In the liver Leflunomide becomes converted to its active metabolite called Teriflunomide, which inhibits the activity of DHODH directly. In recent times Leflunomide is also used for therapy against the Cytomegalovirus and the BK virus. Also for Melanoma was shown recently a decreased growth rate due to Leflunomide treatment in a zebrafish and a mouse model. As Melanoma is a malignant tumor of the skin, which derives also from neural crest progenitor cells, a coherent investigation of effictivity of Leflunomide in neuroblastoma celllines showed first promising results. The aim of our study was to reanalyse the effectivity of Leflunomide in Neuroblastoma and to shed further light in its biological mode of action. Three+B52 biological samples of the human neuroblastoma cell line IMR32 were treated with DMSO or Teriflunomide [118 ᅡᄉM]
Project description:Despite intensive therapy, children with high-risk neuroblastoma are at risk of treatment failure. We applied a multi-omic system approach to evaluate metabolic vulnerabilities in human neuroblastoma. We combined metabolomics, CRISPR screening and transcriptomic data across >700 solid tumor cell lines and identified dihydroorotate dehydrogenase (DHODH), a critical enzyme in pyrimidine synthesis, as a potential treatment target. Of note, DHODH inhibition is currently under clinical investigation in patients with hematologic malignancies. In neuroblastoma, DHODH expression was identified as an independent risk factor for aggressive disease, and high DHODH levels correlated to worse overall and event-free survival. A subset of tumors with the highest DHODH expression was associated with a dismal prognosis, with a 5-year survival of <10%. In xenograft and transgenic neuroblastoma mouse models treated with the DHODH inhibitor brequinar, tumor growth was dramatically reduced, and survival was extended. Furthermore, brequinar treatment was shown to reduce the expression of MYC targets in three different neuroblastoma models in vivo. A combination of brequinar and temozolomide was curative in the majority of transgenic TH-MYCN neuroblastoma mice, indicating a highly active clinical combination therapy. Overall, DHODH inhibition combined with temozolomide has therapeutic potential in neuroblastoma and we propose this combination for clinical testing.
Project description:Despite intensive therapy, children with high-risk neuroblastoma are at risk of treatment failure. We applied a multi-omic system approach to evaluate metabolic vulnerabilities in human neuroblastoma. We combined metabolomics, CRISPR screening and transcriptomic data across >700 solid tumor cell lines and identified dihydroorotate dehydrogenase (DHODH), a critical enzyme in pyrimidine synthesis, as a potential treatment target. Of note, DHODH inhibition is currently under clinical investigation in patients with hematologic malignancies. In neuroblastoma, DHODH expression was identified as an independent risk factor for aggressive disease, and high DHODH levels correlated to worse overall and event-free survival. A subset of tumors with the highest DHODH expression was associated with a dismal prognosis, with a 5-year survival of <10%. In xenograft and transgenic neuroblastoma mouse models treated with the DHODH inhibitor brequinar, tumor growth was dramatically reduced, and survival was extended. Furthermore, brequinar treatment was shown to reduce the expression of MYC targets in three different neuroblastoma models in vivo. A combination of brequinar and temozolomide was curative in the majority of transgenic TH-MYCN neuroblastoma mice, indicating a highly active clinical combination therapy. Overall, DHODH inhibition combined with temozolomide has therapeutic potential in neuroblastoma and we propose this combination for clinical testing.
Project description:Analysis of cellular response to DHODH inhibition at gene expression level. The NS1 protein of influenza virus is a major virulence factor essential for virus replication as it re-directs the host cell to promote viral protein expression. NS1 inhibits cellular mRNA processing and export, down-regulating host gene expression and enhancing viral gene expression. We report here the identification of a non-toxic quinoline carboxylic acid that reverts the inhibition of mRNA nuclear export by NS1, in the absence or presence of virus. This quinoline carboxylic acid directly inhibited dihydroorotate dehydrogenase (DHODH), a host enzyme required for *de novo* pyrimidine biosynthesis, and partially reduced pyrimidine levels. This effect induced NXF1 expression, which promoted mRNA nuclear export in the presence of NS1. The release of NS1-mediated mRNA export block by DHODH inhibition also occurred in the presence of VSV M protein, another viral inhibitor of mRNA export. This reversal of mRNA export block allowed expression of antiviral factors. Thus, pyrimidines play a necessary role in the inhibition of mRNA nuclear export by virulence factors. Total RNA obtained from HBEC cells subjected to compound 1/compound 1-14 treatment compared to DMSO treatment.
Project description:Analysis of cellular response to DHODH inhibition at gene expression level. The NS1 protein of influenza virus is a major virulence factor essential for virus replication as it re-directs the host cell to promote viral protein expression. NS1 inhibits cellular mRNA processing and export, down-regulating host gene expression and enhancing viral gene expression. We report here the identification of a non-toxic quinoline carboxylic acid that reverts the inhibition of mRNA nuclear export by NS1, in the absence or presence of virus. This quinoline carboxylic acid directly inhibited dihydroorotate dehydrogenase (DHODH), a host enzyme required for *de novo* pyrimidine biosynthesis, and partially reduced pyrimidine levels. This effect induced NXF1 expression, which promoted mRNA nuclear export in the presence of NS1. The release of NS1-mediated mRNA export block by DHODH inhibition also occurred in the presence of VSV M protein, another viral inhibitor of mRNA export. This reversal of mRNA export block allowed expression of antiviral factors. Thus, pyrimidines play a necessary role in the inhibition of mRNA nuclear export by virulence factors. Total RNA obtained from HBEC cells subjected to 3 hours compound 1 treatment compared to DMSO treatment.
Project description:PTC299 was identified as an inhibitor of VEGFA mRNA translation in a phenotypic screen and evaluated in the clinic for treatment of solid tumors. To guide precision cancer treatment, we performed extensive biological characterization of the activity of PTC299 and demonstrated that inhibition of VEGF production and cell proliferation by PTC299 is linked to a decrease in uridine nucleotides by targeting dihydroorotate dehydrogenase (DHODH), a rate limiting enzyme for de novo pyrimidine nucleotide synthesis. Unlike previously reported DHODH inhibitors that were identified using in vitro enzyme assays, PTC299 is a more potent inhibitor of DHODH in isolated mitochondria suggesting that mitochondrial membrane lipid engagement in the DHODH conformation in situ is required for its optimal activity. PTC299 has broad and potent activity against hematological cancer cells in preclinical models, reflecting a reduced pyrimidine nucleotide salvage pathway in leukemia cells. Archived serum samples from patients treated with PTC299 demonstrated increased levels of dihydroorotate, the substrate of DHODH, indicating target engagement in patients. PTC299 has advantages over previously reported DHODH inhibitors, including greater potency, good oral bioavailability and lack of off-target kinase inhibition and myelosuppression, and thus may be useful for the targeted treatment of hematologic malignancies.
Project description:Neuroblastoma is an embryonal tumor which originates from neural crest progenitor cells that fail to differentiate along their predefined route to sympathetic neurons or sympatho-adrenergic adrenal cells. It is the most common extracranial tumor of childhood and accounts for 15% of all childhood cancer deaths. Especially patients suffering from high grade or relapsed neuroblastoma have poor outcome in spite of aggressive treatment regimens including autologous stem cell transplantation. Those patients are in urgent need of additional effective therapies which demands the development of targeted approaches. Dihydroorotatedehydrogenase (DHODH) is the fourth enzyme of the pyrimidine synthesis pathway which oxidizes dihydroorotate to orotate. In recent past it became a potential drug target for cancer treatment because of its keyrole in processing essential pyrimidine nucleotides. On the basis of the existing data, functional inhibition of DHODH is considered to be promising therapeutic option for several tumor entities like advanced colorectal, breast or lung-cancers. Leflunomide is an established drug in treatment of the autoimmune diseases rheumatoid arthritis and multiple sclerosis. In the liver Leflunomide becomes converted to its active metabolite called Teriflunomide, which inhibits the activity of DHODH directly. In recent times Leflunomide is also used for therapy against the Cytomegalovirus and the BK virus. Also for Melanoma was shown recently a decreased growth rate due to Leflunomide treatment in a zebrafish and a mouse model. As Melanoma is a malignant tumor of the skin, which derives also from neural crest progenitor cells, a coherent investigation of effictivity of Leflunomide in neuroblastoma celllines showed first promising results. The aim of our study was to reanalyse the effectivity of Leflunomide in Neuroblastoma and to shed further light in its biological mode of action.
Project description:The mitochondrial respiratory chain assembles into higher order complexes termed supercomplexes (SCs) under certain physiological or metabolic stimuli. A small molecule screen developed by the lab identified DHODH inhibitors as potent activators of SC assembly in cancer cells. To investigate the proteomic regulation of SCs under nucleotide deficiency, we treated U2OS cells for 48 hours with Brequinar (500 nM). Proteomic analysis highlighted strong signatures of respiratory chain subunit abundance and peroxisomal-derived ether phospholipid synthesis enzymes. Bypassing DHODH inhibition through uridine supplementation prevented these alterations. These findings establish a coordinated cellular response to reduced nucleotide pools that stimulates ether phospholipid synthesis and respiratory chain supra-assembly.