Project description:Ferroptosis, a form of regulated cell death that is induced by excessive lipid peroxidation, is a key tumour suppression mechanism1-4. Glutathione peroxidase 4 (GPX4)5,6 and ferroptosis suppressor protein 1 (FSP1)7,8 constitute two major ferroptosis defence systems. Here we show that treatment of cancer cells with GPX4 inhibitors results in acute depletion of N-carbamoyl-L-aspartate, a pyrimidine biosynthesis intermediate, with concomitant accumulation of uridine. Supplementation with dihydroorotate or orotate-the substrate and product of dihydroorotate dehydrogenase (DHODH)-attenuates or potentiates ferroptosis induced by inhibition of GPX4, respectively, and these effects are particularly pronounced in cancer cells with low expression of GPX4 (GPX4low). Inactivation of DHODH induces extensive mitochondrial lipid peroxidation and ferroptosis in GPX4low cancer cells, and synergizes with ferroptosis inducers to induce these effects in GPX4high cancer cells. Mechanistically, DHODH operates in parallel to mitochondrial GPX4 (but independently of cytosolic GPX4 or FSP1) to inhibit ferroptosis in the mitochondrial inner membrane by reducing ubiquinone to ubiquinol (a radical-trapping antioxidant with anti-ferroptosis activity). The DHODH inhibitor brequinar selectively suppresses GPX4low tumour growth by inducing ferroptosis, whereas combined treatment with brequinar and sulfasalazine, an FDA-approved drug with ferroptosis-inducing activity, synergistically induces ferroptosis and suppresses GPX4high tumour growth. Our results identify a DHODH-mediated ferroptosis defence mechanism in mitochondria and suggest a therapeutic strategy of targeting ferroptosis in cancer treatment.
Project description:Polyamines are a class of small polycationic alkylamines that play essential roles in both normal and cancer cell growth. Polyamine metabolism is frequently dysregulated and considered a therapeutic target in cancer. However, targeting polyamine metabolism as monotherapy often exhibits limited efficacy, and the underlying mechanisms are incompletely understood. Here we report that activation of polyamine catabolism promotes glutamine metabolism, leading to a targetable vulnerability in lung cancer. Genetic and pharmacological activation of spermidine/spermine N1-acetyltransferase 1 (SAT1), the rate-limiting enzyme of polyamine catabolism, enhances the conversion of glutamine to glutamate and subsequent glutathione (GSH) synthesis. This metabolic rewiring ameliorates oxidative stress to support lung cancer cell proliferation and survival. Simultaneous glutamine limitation and SAT1 activation result in ROS accumulation, growth inhibition, and cell death. Importantly, pharmacological inhibition of either one of glutamine transport, glutaminase, or GSH biosynthesis in combination with activation of polyamine catabolism synergistically suppresses lung cancer cell growth and xenograft tumor formation. Together, this study unveils a previously unappreciated functional interconnection between polyamine catabolism and glutamine metabolism and establishes cotargeting strategies as potential therapeutics in lung cancer.
Project description:Despite advances in various chemotherapy regimens, current therapeutic options are limited for ovarian cancer patients. Oxidative stress-induced growth inhibitor 1 (OSGIN1), which is a tumor suppressor gene known to regulate the cellular stress response and apoptosis, is associated with ovarian cancer development. However, the underlying mechanisms involved in ferroptosis regulation have not been elucidated. Thus, this study aimed to investigate the effect and underlying regulatory mechanism of the OSGIN1 gene on ovarian cancer cells. Our results demonstrated that loss of the OSGIN1 gene promoted ovarian cancer growth and conferred resistance to drug-induced ferroptosis. Mechanistically, the loss of OSGIN1 activates AMPK signaling through ATM, leading to the upregulation of SLC2A3, which protects cells from ferroptosis and renders them insensitive to ferroptosis inducers. Notably, an SLC2A3-neutralizing antibody enhances the ferroptosis-inducing and anticancer effects of sorafenib on ovarian cancer patient-derived xenograft tumors. Overall, anti-SLC2A3 therapy is a promising method to improve ovarian cancer treatment by targeting ferroptosis.
Project description:Ferroptosis has emerged as an attractive strategy in cancer therapy. Understanding the operational networks regulating ferroptosis may unravel vulnerabilities that could be harnessed for therapeutic benefit. Using CRISPR-activation screens in ferroptosis hypersensitive cells, we identify the selenoprotein P (SELENOP) receptor, LRP8, as a key determinant protecting MYCN-amplified neuroblastoma cells from ferroptosis. Genetic deletion of LRP8 leads to ferroptosis as a result of an insufficient supply of selenocysteine, which is required for the translation of the anti-ferroptotic selenoprotein GPX4. This dependency is caused by low expression of alternative selenium uptake pathways such as system Xc-. The identification of LRP8 as a specific vulnerability of MYCN-amplified neuroblastoma cells was confirmed in constitutive and inducible LRP8 knockout orthotopic xenografts. These findings disclose a yet-unaccounted mechanism of selective ferroptosis induction that might be explored as a therapeutic strategy for high-risk neuroblastoma and potentially other MYCN-amplified entities.
Project description:BackgroundGastric cancer patients harboring a TP53 mutation exhibit a more aggressive and chemoresistant phenotype. Unfortunately, efforts to identify the vulnerabilities to overcome these aggressive malignancies have made minimal progress in recent years. Therefore, there is an urgent need to explore the novel therapeutic strategies for this subclass. Histone methylation modulators are critical epigenetic targets for cancer therapies that help maintain the malignancies of cancers harboring TP53 mutations and senescence evasion. Triggering senescence is now considered to benefit multiple cancer therapies. Furthermore, senescence-based "one-two punch" therapy was validated in clinical trials. Therefore, we hypothesized that screening epigenetic modulators might help identify a novel vulnerability to trigger senescence in gastric cancer harboring TP53 mutations.ResultsWe developed a novel efficient approach to identify senescence inducers by sequentially treating cells with drug candidates and senolytic agents. Based on this, we demonstrated that QC6352 (a selective KDM4C inhibitor) efficiently triggered cellular senescence in gastric cancer harboring TP53 mutations. More importantly, the "one-two punch' therapy consisting of QC6352 and SSK1 eliminates tumor cells harboring TP53 mutations. This finding highlights a potential therapeutic strategy for the aggressive subgroup of gastric cancer. Besides, the functions of QC6352 were totally unknown. We demonstrated that QC6352 might possess far more powerful anti-tumor capacities compared to the traditional genotoxic drugs, 5-Fu and Oxaliplatin.ConclusionsThis initial investigation to identify a senescence inducer revealed that QC6352 triggers senescence in gastric cancer cells harboring TP53 mutations by regulating the SP1/CDK2 axis through suppressing KDM4C. QC6352 and senolytic agent-SSK1 represent a novel 'one-two punch' therapeutic strategy for the more malignant gastric cancer subtypes.
Project description:The growing knowledge of ferroptosis has suggested the role and therapeutic potential of ferroptosis in cancer, but has not been translated into effective therapy. Liver cancer, primarily hepatocellular carcinoma (HCC), is highly lethal with limited treatment options. LIFR is frequently downregulated in HCC. Here, by studying hepatocyte-specific and inducible Lifr-knockout mice, we show that loss of Lifr promotes liver tumorigenesis and confers resistance to drug-induced ferroptosis. Mechanistically, loss of LIFR activates NF-κB signaling through SHP1, leading to upregulation of the iron-sequestering cytokine LCN2, which depletes iron and renders insensitivity to ferroptosis inducers. Notably, an LCN2-neutralizing antibody enhances the ferroptosis-inducing and anticancer effects of sorafenib on HCC patient-derived xenograft tumors with low LIFR expression and high LCN2 expression. Thus, anti-LCN2 therapy is a promising way to improve liver cancer treatment by targeting ferroptosis.
Project description:CTNNB1, encoding β-catenin protein, is the most frequently altered proto-oncogene in hepatic neoplasms. In this study, we studied the significance and pathological mechanism of CTNNB1 gain-of-function mutations in hepatocarcinogenesis. Activated β-catenin not only triggered hepatic tumorigenesis but also exacerbated Tp53 deletion or hepatitis B virus infection-mediated liver cancer development in mouse models. Using untargeted metabolomic profiling, we identified boosted de novo pyrimidine synthesis as the major metabolic aberration in β-catenin mutant cell lines and livers. Oncogenic β-catenin transcriptionally stimulated AKT2, which then phosphorylated the rate-limiting de novo pyrimidine synthesis enzyme CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamoylase, dihydroorotase) on S1406 and S1859 to potentiate nucleotide synthesis. Moreover, inhibition of β-catenin/AKT2-stimulated pyrimidine synthesis axis preferentially repressed β-catenin mutant cell proliferation and tumor formation. Therefore, β-catenin active mutations are oncogenic in various preclinical liver cancer models. Stimulation of β-catenin/AKT2/CAD signaling cascade on pyrimidine synthesis is an essential and druggable vulnerability for β-catenin mutant liver cancer.
Project description:Anticancer therapies can induce cellular senescence or drug-tolerant persistence, two types of proliferative arrest that differ in their stability. While senescence is highly stable, persister cells efficiently resume proliferation upon therapy termination, resulting in tumor relapse. Here, we used an ATP-competitive mTOR inhibitor to induce and characterize persistence in human cancer cells of various origins. Using this model and previously described models of senescence, we compared the same cancer cell lines under the two types of proliferative arrest. Persister and senescent cancer cells shared an expanded lysosomal compartment and hypersensitivity to BCL-XL inhibition. However, persister cells lacked other features of senescence, such as loss of lamin B1, senescence-associated β-galactosidase activity, upregulation of MHC-I, and an inflammatory and secretory phenotype (senescence-associated secretory phenotype or SASP). A genome-wide CRISPR/Cas9 screening for genes required for the survival of persister cells revealed that they are hypersensitive to the inhibition of one-carbon (1C) metabolism, which was validated by the pharmacologic inhibition of serine hydroxymethyltransferase, a key enzyme that feeds methyl groups from serine into 1C metabolism. Investigation into the relationship between 1C metabolism and the epigenetic regulation of transcription uncovered the presence of the repressive heterochromatic mark H4K20me3 at the promoters of SASP and IFN response genes in persister cells, whereas it was absent in senescent cells. Moreover, persister cells overexpressed the H4K20 methyltransferases KMT5B/C, and their downregulation unleashed inflammatory programs and compromised the survival of persister cells. In summary, this study identifies distinctive features and actionable vulnerabilities of persister cancer cells and provides mechanistic insight into their low inflammatory activity. Significance: Cell persistence and senescence are distinct states of proliferative arrest induced by cancer therapy, with persister cells being characterized by the silencing of inflammatory genes through the heterochromatic mark H4K20me3. See related commentary by Schmitt, p. 7.
Project description:Ferroptosis has emerged as an attractive strategy in cancer therapy. Understanding the operational networks regulating ferroptosis may unravel vulnerabilities that could be harnessed for therapeutic benefit. Using CRISPR-activation screens in ferroptosis hypersensitive cells, we identify the selenoprotein P (SELENOP) receptor, LRP8, as a key determinant protecting MYCN-amplified neuroblastoma cells from ferroptosis. Genetic deletion of LRP8 leads to ferroptosis as a result of an insufficient supply of selenocysteine, which is required for the translation of the antiferroptotic selenoprotein GPX4. This dependency is caused by low expression of alternative selenium uptake pathways such as system Xc- . The identification of LRP8 as a specific vulnerability of MYCN-amplified neuroblastoma cells was confirmed in constitutive and inducible LRP8 knockout orthotopic xenografts. These findings disclose a yet-unaccounted mechanism of selective ferroptosis induction that might be explored as a therapeutic strategy for high-risk neuroblastoma and potentially other MYCN-amplified entities.
Project description:Pro-survival members of the BCL-2 family, including MCL-1, are emerging as important proteins during the development and therapeutic response of solid tumors. Notably, high levels of MCL-1 occur in breast cancer, where functional dependency has been demonstrated using cell lines and mouse models. The utility of restoring apoptosis in cancer cells through inhibition of pro-survival BCL-2 proteins has been realized in the clinic, where the first specific inhibitor of BCL-2 is approved for use in leukemia. A variety of MCL-1 inhibitors are now undergoing clinical trials for blood cancer treatment and application of this new class of drugs is also being tested in solid cancers. On-target compounds specific to MCL-1 have demonstrated promising efficacy in preclinical models of breast cancer and show potential to enhance the anti-tumor effect of conventional therapies. Taken together, this makes MCL-1 an extremely attractive target for clinical evaluation in the context of breast cancer.Abbreviations: ADC (antibody-drug conjugate); AML (Acute myeloid leukemia); APAF1 (apoptotic protease activating factor 1); bCAFs (breast cancer associated fibroblasts); BCL-2 (B-cell lymphoma 2); BH (BCL-2 homology); CLL (chronic lymphocytic leukemia); EGF (epidermal growth factor); EMT (epithelial to mesenchymal transition); ER (estrogen receptor); FDA (food and drug administration); GEMM (genetically engineered mouse model); HER2 (human epidermal growth factor 2); IL6 (interleukin 6); IMM (inner mitochondrial membrane); IMS (intermembrane space); MCL-1 (myeloid cell leukemia-1); MOMP (mitochondrial outer membrane permeabilisation); MM (multiple myeloma); PDX (patient-derived xenograft); OMM (outer mitochondrial membrane); PROTAC (proteolysis-targeting chimeras) TNBC (triple negative breast cancer); UPS (ubiquitin mediated proteolysis system).