ABSTRACT
Renal medullary carcinoma (RMC) is an aggressive kidney cancer that almost exclusively develops in individuals with sickle cell trait (SCT) and is always characterized by loss of the tumor suppressor SMARCB1. Because renal ischemia induced by red blood cell sickling exacerbates chronic renal medullary hypoxia inĀ vivo, we investigated whether the loss of SMARCB1 confers a survival advantage under the setting of SCT. Hypoxic stress, which naturally occurs within the renal medulla, is elevated under the setting of SCT. Our findings showed that hypoxia-induced SMARCB1 degradation protected renal cells from hypoxic stress. SMARCB1 wild-type renal tumors exhibited lower levels of SMARCB1 and more aggressive growth in mice harboring the SCT mutation in human hemoglobin A (HbA) than in control mice harboring wild-type human HbA. Consistent with established clinical observations, SMARCB1-null renal tumors were refractory to hypoxia-inducing therapeutic inhibition of angiogenesis. Further, reconstitution of SMARCB1 restored renal tumor sensitivity to hypoxic stress inĀ vitro and inĀ vivo. Together, our results demonstrate a physiological role for SMARCB1 degradation in response to hypoxic stress, connect the renal medullary hypoxia induced by SCT with an increased risk of SMARCB1-negative RMC, and shed light into the mechanisms mediating the resistance of SMARCB1-null renal tumors against angiogenesis inhibition therapies.
Subject(s)
Carcinoma, Renal Cell , Kidney Neoplasms , Sickle Cell Trait , Animals , Humans , Mice , Carcinoma, Renal Cell/pathology , Hypoxia/genetics , Hypoxia/metabolism , Kidney/metabolism , Kidney Neoplasms/pathology , Sickle Cell Trait/genetics , Sickle Cell Trait/metabolism , SMARCB1 Protein/genetics , SMARCB1 Protein/metabolismABSTRACT
Pancreatic ductal adenocarcinoma (PDAC) remains recalcitrant to all forms of cancer treatment and carries a five-year survival rate of only 8%1. Inhibition of oncogenic KRAS (hereafter KRAS*), the earliest lesion in disease development that is present in more than 90% of PDACs, and its signalling surrogates has yielded encouraging preclinical results with experimental agents2-4. However, KRAS*-independent disease recurrence following genetic extinction of Kras* in mouse models anticipates the need for co-extinction strategies5,6. Multiple oncogenic processes are initiated at the cell surface, where KRAS* physically and functionally interacts to direct signallingĀ that is essential for malignant transformation and tumour maintenance. Insights into the complexity of the functional cell-surface-protein repertoire (surfaceome) have been technologically limited until recently and-in the case of PDAC-the genetic control of the function and composition of the PDAC surfaceome in the context of KRAS* signalling remains largely unknown. Here we develop an unbiased, functional target-discovery platform to query KRAS*-dependent changes of the PDAC surfaceome, which reveals syndecan 1 (SDC1, also known as CD138) as a protein that is upregulated at the cell surface by KRAS*. Localization of SDC1 at the cell surface-where it regulates macropinocytosis, an essential metabolic pathway that fuels PDAC cell growth-is essential for disease maintenance and progression. Thus, our study forges a mechanistic link between KRAS* signalling and a targetable molecule driving nutrient salvage pathways in PDAC and validates oncogene-driven surfaceome annotation as a strategy to identify cancer-specific vulnerabilities.
Subject(s)
Carcinoma, Pancreatic Ductal/pathology , Pancreatic Neoplasms/pathology , Pinocytosis , Syndecan-1/metabolism , ADP-Ribosylation Factor 6 , ADP-Ribosylation Factors/metabolism , Animals , Carcinoma, Pancreatic Ductal/genetics , Carcinoma, Pancreatic Ductal/metabolism , Cell Proliferation , Disease Progression , Female , Guanine Nucleotide Exchange Factors/metabolism , Humans , Male , Mice , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/metabolism , Proto-Oncogene Proteins p21(ras)/genetics , Proto-Oncogene Proteins p21(ras)/metabolism , Signal TransductionABSTRACT
Complex genomic rearrangements (CGRs) are a hallmark of many human diseases. Recently, CGRs were suggested to result from microhomology-mediated break-induced replication (MMBIR), a replicative mechanism involving template switching at positions of microhomology. Currently, the cause of MMBIR and the proteins mediating this process remain unknown. Here, we demonstrate in yeast that a collapse of homology-driven break-induced replication (BIR) caused by defective repair DNA synthesis in the absence of Pif1 helicase leads to template switches involving 0-6 nt of homology, followed by resolution of recombination intermediates into chromosomal rearrangements. Importantly, we show that these microhomology-mediated template switches, indicative of MMBIR, are driven by translesion synthesis (TLS) polymerases PolĆĀ¶ and Rev1. Thus, an interruption of BIR involving fully homologous chromosomes in yeast triggers a switch to MMBIR catalyzed by TLS polymerases. Overall, our study provides important mechanistic insights into the initiation of MMBIR associated with genomic rearrangements, similar to those promoting diseases in humans.
Subject(s)
Chromosome Aberrations , DNA Breaks, Single-Stranded , Nucleotidyltransferases/metabolism , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae/genetics , Chromosomes, Fungal , DNA Helicases/metabolism , DNA Replication , DNA-Directed DNA Polymerase/metabolism , Genes, Fungal , Humans , Saccharomyces cerevisiae/enzymology , Sequence HomologyABSTRACT
BACKGROUND & AIMS: Understanding the mechanisms by which tumors adapt to therapy is critical for developing effective combination therapeutic approaches to improve clinical outcomes for patients with cancer. METHODS: To identify promising and clinically actionable targets for managing colorectal cancer (CRC), we conducted a patient-centered functional genomics platform that includes approximately 200 genes and paired this with a high-throughput drug screen that includes 262 compounds in four patient-derived xenografts (PDXs) from patients with CRC. RESULTS: Both screening methods identified exportin 1 (XPO1) inhibitors as drivers of DNA damage-induced lethality in CRC. Molecular characterization of the cellular response to XPO1 inhibition uncovered an adaptive mechanism that limited the duration of response in TP53-mutated, but not in TP53-wild-type CRC models. Comprehensive proteomic and transcriptomic characterization revealed that the ATM/ATR-CHK1/2 axes were selectively engaged in TP53-mutant CRC cells upon XPO1 inhibitor treatment and that this response was required for adapting to therapy and escaping cell death. Administration of KPT-8602, an XPO1 inhibitor, followed by AZD-6738, an ATR inhibitor, resulted in dramatic antitumor effects and prolonged survival in TP53-mutant models of CRC. CONCLUSIONS: Our findings anticipate tremendous therapeutic benefit and support the further evaluation of XPO1 inhibitors, especially in combination with DNA damage checkpoint inhibitors, to elicit an enduring clinical response in patients with CRC harboring TP53 mutations.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/administration & dosage , Ataxia Telangiectasia Mutated Proteins/antagonists & inhibitors , Biomarkers, Tumor/genetics , Colorectal Neoplasms/drug therapy , Karyopherins/antagonists & inhibitors , Mutation , Protein Kinase Inhibitors/administration & dosage , Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors , Tumor Suppressor Protein p53/genetics , Animals , Ataxia Telangiectasia Mutated Proteins/metabolism , Colorectal Neoplasms/genetics , Colorectal Neoplasms/metabolism , Colorectal Neoplasms/pathology , Databases, Genetic , HCT116 Cells , HT29 Cells , Humans , Indoles/administration & dosage , Karyopherins/metabolism , Mice , Morpholines/administration & dosage , Piperazines/administration & dosage , Pyridines/administration & dosage , Pyrimidines/administration & dosage , Receptors, Cytoplasmic and Nuclear/metabolism , Sulfonamides/administration & dosage , Xenograft Model Antitumor Assays , Exportin 1 ProteinABSTRACT
Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in western countries, with a median survival of 6 months and an extremely low percentage of long-term surviving patients. KRAS mutations are known to be a driver event of PDAC, but targeting mutant KRAS has proved challenging. Targeting oncogene-driven signalling pathways is a clinically validated approach for several devastating diseases. Still, despite marked tumour shrinkage, the frequency of relapse indicates that a fraction of tumour cells survives shut down of oncogenic signalling. Here we explore the role of mutant KRAS in PDAC maintenance using a recently developed inducible mouse model of mutated Kras (Kras(G12D), herein KRas) in a p53(LoxP/WT) background. We demonstrate that a subpopulation of dormant tumour cells surviving oncogene ablation (surviving cells) and responsible for tumour relapse has features of cancer stem cells and relies on oxidative phosphorylation for survival. Transcriptomic and metabolic analyses of surviving cells reveal prominent expression of genes governing mitochondrial function, autophagy and lysosome activity, as well as a strong reliance on mitochondrial respiration and a decreased dependence on glycolysis for cellular energetics. Accordingly, surviving cells show high sensitivity to oxidative phosphorylation inhibitors, which can inhibit tumour recurrence. Our integrated analyses illuminate a therapeutic strategy of combined targeting of the KRAS pathway and mitochondrial respiration to manage pancreatic cancer.
Subject(s)
Carcinoma, Pancreatic Ductal/metabolism , Carcinoma, Pancreatic Ductal/pathology , Mitochondria/metabolism , Pancreatic Neoplasms/metabolism , Pancreatic Neoplasms/pathology , Proto-Oncogene Proteins p21(ras)/genetics , Animals , Autophagy , Carcinoma, Pancreatic Ductal/drug therapy , Carcinoma, Pancreatic Ductal/genetics , Cell Respiration/drug effects , Cell Survival/drug effects , Disease Models, Animal , Female , Gene Expression Regulation, Neoplastic , Genes, p53/genetics , Glycolysis , Lysosomes/metabolism , Mice , Mitochondria/drug effects , Mutation/genetics , Neoplasm Recurrence, Local/prevention & control , Neoplastic Stem Cells/drug effects , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/pathology , Oxidative Phosphorylation/drug effects , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/genetics , Proto-Oncogene Proteins p21(ras)/metabolism , Recurrence , Signal Transduction , Pancreatic NeoplasmsABSTRACT
The repair of chromosomal double strand breaks (DSBs) is crucial for the maintenance of genomic integrity. However, the repair of DSBs can also destabilize the genome by causing mutations and chromosomal rearrangements, the driving forces for carcinogenesis and hereditary diseases. Break-induced replication (BIR) is one of the DSB repair pathways that is highly prone to genetic instability. BIR proceeds by invasion of one broken end into a homologous DNA sequence followed by replication that can copy hundreds of kilobases of DNA from a donor molecule all the way through its telomere. The resulting repaired chromosome comes at a great cost to the cell, as BIR promotes mutagenesis, loss of heterozygosity, translocations, and copy number variations, all hallmarks of carcinogenesis. BIR uses most known replication proteins to copy large portions of DNA, similar to S-phase replication. It has therefore been suggested that BIR proceeds by semiconservative replication; however, the model of a bona fide, stable replication fork contradicts the known instabilities associated with BIR such as a 1,000-fold increase in mutation rate compared to normal replication. Here we demonstrate that in budding yeast the mechanism of replication during BIR is significantly different from S-phase replication, as it proceeds via an unusual bubble-like replication fork that results in conservative inheritance of the new genetic material. We provide evidence that this atypical mode of DNA replication, dependent on Pif1 helicase, is responsible for the marked increase in BIR-associated mutations. We propose that the BIR mode of synthesis presents a powerful mechanism that can initiate bursts of genetic instability in eukaryotes, including humans.
Subject(s)
Chromosome Breakage , DNA Breaks, Double-Stranded , DNA Replication/genetics , DNA, Fungal/biosynthesis , Saccharomyces cerevisiae/genetics , DNA Helicases/metabolism , DNA Repair/genetics , DNA, Fungal/genetics , Genomic Instability/genetics , Mutagenesis/genetics , S Phase/genetics , Saccharomyces cerevisiae/cytology , Saccharomyces cerevisiae/enzymology , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae Proteins/metabolismABSTRACT
Break-induced replication (BIR) is a mechanism to repair double-strand breaks (DSBs) that possess only a single end that can find homology in the genome. This situation can result from the collapse of replication forks or telomere erosion. BIR frequently produces various genetic instabilities including mutations, loss of heterozygosity, deletions, duplications, and template switching that can result in copy-number variations (CNVs). An important type of genomic rearrangement specifically linked to BIR is half-crossovers (HCs), which result from fusions between parts of recombining chromosomes. Because HC formation produces a fused molecule as well as a broken chromosome fragment, these events could be highly destabilizing. Here we demonstrate that HC formation results from the interruption of BIR caused by a damaged template, defective replisome or premature onset of mitosis. Additionally, we document that checkpoint failure promotes channeling of BIR into half-crossover-initiated instability cascades (HCC) that resemble cycles of non-reciprocal translocations (NRTs) previously described in human tumors. We postulate that HCs represent a potent source of genetic destabilization with significant consequences that mimic those observed in human diseases, including cancer.
Subject(s)
DNA Breaks, Double-Stranded , DNA Replication/genetics , Recombination, Genetic , Telomere/genetics , DNA Copy Number Variations/genetics , DNA Repair/genetics , Genomic Instability , Humans , Neoplasms/etiology , Neoplasms/genetics , Saccharomyces cerevisiae , Telomere/pathologyABSTRACT
Chromosomal structural change triggers carcinogenesis and the formation of other genetic diseases. The breakpoint junctions of these rearrangements often contain small overlapping sequences called "microhomology," yet the genetic pathway(s) responsible have yet to be defined. We report a simple genetic system to detect microhomology-mediated repair (MHMR) events after a DNA double-strand break (DSB) in budding yeast cells. MHMR using >15 bp operates as a single-strand annealing variant, requiring the non-essential DNA polymerase subunit Pol32. MHMR is inhibited by sequence mismatches, but independent of extensive DNA synthesis like break-induced replication. However, MHMR using less than 14 bp is genetically distinct from that using longer microhomology and far less efficient for the repair of distant DSBs. MHMR catalyzes chromosomal translocation almost as efficiently as intra-chromosomal repair. The results suggest that the intrinsic annealing propensity between microhomology sequences efficiently leads to chromosomal rearrangements.
Subject(s)
DNA Breaks, Double-Stranded , DNA End-Joining Repair , DNA Replication/genetics , Translocation, Genetic/genetics , Chromosome Aberrations , Chromosomes/metabolism , DNA Repair , DNA-Binding Proteins , DNA-Directed DNA Polymerase/genetics , DNA-Directed DNA Polymerase/metabolism , Recombination, Genetic , Saccharomyces cerevisiaeABSTRACT
DNA must be synthesized for purposes of genome duplication and DNA repair. While the former is a highly accurate process, short-patch synthesis associated with repair of DNA damage is often error-prone. Break-induced replication (BIR) is a unique cellular process that mimics normal DNA replication in its processivity, rate, and capacity to duplicate hundreds of kilobases, but is initiated at double-strand breaks (DSBs) rather than at replication origins. Here we employed a series of frameshift reporters to measure mutagenesis associated with BIR in Saccharomyces cerevisiae. We demonstrate that BIR DNA synthesis is intrinsically inaccurate over the entire path of the replication fork, as the rate of frameshift mutagenesis during BIR is up to 2,800-fold higher than during normal replication. Importantly, this high rate of mutagenesis was observed not only close to the DSB where BIR is less stable, but also far from the DSB where the BIR replication fork is fast and stabilized. We established that polymerase proofreading and mismatch repair correct BIR errors. Also, dNTP levels were elevated during BIR, and this contributed to BIR-related mutagenesis. We propose that a high level of DNA polymerase errors that is not fully compensated by error-correction mechanisms is largely responsible for mutagenesis during BIR, with Pol ĆĀ“ generating many of the mutagenic errors. We further postulate that activation of BIR in eukaryotic cells may significantly contribute to accumulation of mutations that fuel cancer and evolution.
Subject(s)
DNA Breaks , DNA Replication/physiology , Saccharomyces cerevisiae/genetics , Base Sequence , DNA Mismatch Repair , DNA Repair , DNA-Directed DNA Polymerase/physiology , Deoxyribonucleotides/metabolism , Frameshift Mutation , Molecular Sequence Data , MutagenesisABSTRACT
The therapeutic benefit of recently developed mutant KRAS (mKRAS) inhibitors has been limited by the rapid onset of resistance. Here, we aimed to delineate the mechanisms underlying acquired resistance to mKRAS inhibition and identify actionable targets for overcoming this clinical challenge. Previously, we identified Syndecan-1 (SDC1) as a key effector for pancreatic cancer progression whose surface expression is driven by mKRAS. By leveraging both pancreatic and colorectal cancer models, we found that surface SDC1 expression was initially diminished upon mKRAS inhibition, but recovered in tumor cells that bypass mKRAS dependency. Functional studies showed that these tumors depended on SDC1 for survival, further establishing SDC1 as a driver for the acquired resistance to mKRAS inhibition. Mechanistically, we revealed that the YAP1-SDC1 axis was the major driving force for bypassing mKRAS dependency to sustain nutrient salvage machinery and tumor maintenance. Specifically, YAP1 activation mediated the recovery of SDC1 localization on cell surface that sustained macropinocytosis and enhanced the activation of multiple RTKs, promoting resistance to KRAS-targeted therapy. Overall, our study has provided the rationale for targeting the YAP-SDC1 axis to overcome resistance to mKRAS inhibition, thereby revealing new therapeutic opportunities for improving the clinical outcome of patients with KRAS-mutated cancers.
ABSTRACT
Tumors represent ecosystems where subclones compete during tumor growth. While extensively investigated, a comprehensive picture of the interplay of clonal lineages during dissemination is still lacking. Using patient-derived pancreatic cancer cells, we created orthotopically implanted clonal replica tumors to trace clonal dynamics of unperturbed tumor expansion and dissemination. This model revealed the multifaceted nature of tumor growth, with rapid changes in clonal fitness leading to continuous reshuffling of tumor architecture and alternating clonal dominance as a distinct feature of cancer growth. Regarding dissemination, a large fraction of tumor lineages could be found at secondary sites each having distinctive organ growth patterns as well as numerous undescribed behaviors such as abortive colonization. Paired analysis of primary and secondary sites revealed fitness as major contributor to dissemination. From the analysis of pro- and nonmetastatic isogenic subclones, we identified a transcriptomic signature able to identify metastatic cells in human tumors and predict patients' survival.
Subject(s)
Ecosystem , Pancreatic Neoplasms , Humans , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/pathology , Gene Expression Profiling , TranscriptomeABSTRACT
It is unclear how cells counteract the potentially harmful effects of uncoordinated DNA replication in the context of oncogenic stress. Here, we identify the WRAD (WDR5/RBBP5/ASH2L/DPY30) core as a modulator of DNA replication in pancreatic ductal adenocarcinoma (PDAC) models. Molecular analyses demonstrated that the WRAD core interacts with the replisome complex, with disruption of DPY30 resulting in DNA re-replication, DNA damage, and chromosomal instability (CIN) without affecting cancer cell proliferation. Consequently, in immunocompetent models, DPY30 loss induced T cell infiltration and immune-mediated clearance of highly proliferating cancer cells with complex karyotypes, thus improving anti-tumor efficacy upon anti-PD-1 treatment. In PDAC patients, DPY30 expression was associated with high tumor grade, worse prognosis, and limited response to immune checkpoint blockade. Together, our findings indicate that the WRAD core sustains genome stability and suggest that low intratumor DPY30 levels may identify PDAC patients who will benefit from immune checkpoint inhibitors.
ABSTRACT
Inefficient and inaccurate repair of DNA damage is the principal cause of DNA mutations, chromosomal aberrations, and carcinogenesis. Numerous multiple-step DNA repair pathways exist whose deployment depends on the nature of the DNA lesion. Common to all eukaryotic DNA repair pathways is the need to unravel the compacted chromatin structure to facilitate access of the repair machinery to the DNA and restoration of the original chromatin state afterward. Accordingly, our cells utilize a plethora of coordinated mechanisms to locally open up the chromatin structure to reveal the underlying DNA sequence and to orchestrate the efficient and accurate repair of DNA lesions. Here we review changes to the chromatin structure that are intrinsic to the DNA damage response and the available mechanistic insight into how these chromatin changes facilitate distinct stages of the DNA damage repair pathways to maintain genomic stability.
Subject(s)
Chromatin Assembly and Disassembly/physiology , DNA Breaks, Double-Stranded , DNA Repair/genetics , Epigenesis, Genetic/genetics , Genomic Instability/genetics , Histones/metabolism , Models, Biological , Chromatin Assembly and Disassembly/geneticsABSTRACT
Mitochondria are hubs where bioenergetics, redox homeostasis, and anabolic metabolism pathways integrate through a tightly coordinated flux of metabolites. The contributions of mitochondrial metabolism to tumor growth and therapy resistance are evident, but drugs targeting mitochondrial metabolism have repeatedly failed in the clinic. Our study in pancreatic ductal adenocarcinoma (PDAC) finds that cellular and mitochondrial lipid composition influence cancer cell sensitivity to pharmacological inhibition of electron transport chain complex I. Profiling of patient-derived PDAC models revealed that monounsaturated fatty acids (MUFAs) and MUFA-linked ether phospholipids play a critical role in maintaining ROS homeostasis. We show that ether phospholipids support mitochondrial supercomplex assembly and ROS production; accordingly, blocking de novo ether phospholipid biosynthesis sensitized PDAC cells to complex I inhibition by inducing mitochondrial ROS and lipid peroxidation. These data identify ether phospholipids as a regulator of mitochondrial redox control that contributes to the sensitivity of PDAC cells to complex I inhibition.
Subject(s)
Carcinoma, Pancreatic Ductal , Pancreatic Neoplasms , Humans , Reactive Oxygen Species/metabolism , Phospholipid Ethers/metabolism , Mitochondria/metabolism , Phospholipids/metabolism , Pancreatic Neoplasms/pathology , Carcinoma, Pancreatic Ductal/metabolism , HomeostasisABSTRACT
Cellular dedifferentiation is a key mechanism driving cancer progression. Acquisition of mesenchymal features has been associated with drug resistance, poor prognosis, and disease relapse in many tumor types. Therefore, successful targeting of tumors harboring these characteristics is a priority in oncology practice. The SWItch/Sucrose non-fermentable (SWI/SNF) chromatin remodeling complex has also emerged as a critical player in tumor progression, leading to the identification of several SWI/SNF complex genes as potential disease biomarkers and targets of anticancer therapies. AT-rich interaction domain-containing protein 1A (ARID1A) is a component of SWI/SNF, and mutations in ARID1A represent one of the most frequent molecular alterations in human cancers. ARID1A mutations occur in approximately 10% of pancreatic ductal adenocarcinomas (PDAC), but whether these mutations confer a therapeutic opportunity remains unclear. Here, we demonstrate that loss of ARID1A promotes an epithelial-mesenchymal transition (EMT) phenotype and sensitizes PDAC cells to a clinical inhibitor of HSP90, NVP-AUY922, both in vitro and in vivo. Although loss of ARID1A alone did not significantly affect proliferative potential or rate of apoptosis, ARID1A-deficient cells were sensitized to HSP90 inhibition, potentially by promoting the degradation of intermediate filaments driving EMT, resulting in cell death. Our results describe a mechanistic link between ARID1A defects and a quasi-mesenchymal phenotype, suggesting that deleterious mutations in ARID1A associated with protein loss exhibit potential as a biomarker for patients with PDAC who may benefit by HSP90-targeting drugs treatment. SIGNIFICANCE: This study identifies ARID1A loss as a promising biomarker for the identification of PDAC tumors that are potentially responsive to treatment with proteotoxic agents.
Subject(s)
Antineoplastic Agents/pharmacology , DNA-Binding Proteins/metabolism , Epithelial-Mesenchymal Transition , Gene Expression Regulation, Neoplastic/drug effects , HSP90 Heat-Shock Proteins/antagonists & inhibitors , Isoxazoles/pharmacology , Pancreatic Neoplasms/drug therapy , Resorcinols/pharmacology , Transcription Factors/metabolism , Animals , Apoptosis , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , Carcinoma, Pancreatic Ductal/drug therapy , Carcinoma, Pancreatic Ductal/metabolism , Carcinoma, Pancreatic Ductal/pathology , Cell Proliferation , DNA-Binding Proteins/genetics , Female , Humans , Mice , Mice, Nude , Pancreatic Neoplasms/metabolism , Pancreatic Neoplasms/pathology , Prognosis , Transcription Factors/genetics , Tumor Cells, Cultured , Xenograft Model Antitumor AssaysABSTRACT
Glioblastoma (GBM) is highly resistant to chemotherapies, immune-based therapies, and targeted inhibitors. To identify novel drug targets, we screened orthotopically implanted, patient-derived glioblastoma sphere-forming cells using an RNAi library to probe essential tumor cell metabolic programs. This identified high dependence on mitochondrial fatty acid metabolism. We focused on medium-chain acyl-CoA dehydrogenase (MCAD), which oxidizes medium-chain fatty acids (MCFA), due to its consistently high score and high expression among models and upregulation in GBM compared with normal brain. Beyond the expected energetics impairment, MCAD depletion in primary GBM models induced an irreversible cascade of detrimental metabolic effects characterized by accumulation of unmetabolized MCFAs, which induced lipid peroxidation and oxidative stress, irreversible mitochondrial damage, and apoptosis. Our data uncover a novel protective role for MCAD to clear lipid molecules that may cause lethal cell damage, suggesting that therapeutic targeting of MCFA catabolism may exploit a key metabolic feature of GBM. SIGNIFICANCE: MCAD exerts a protective role to prevent accumulation of toxic metabolic by-products in glioma cells, actively catabolizing lipid species that would otherwise affect mitochondrial integrity and induce cell death. This work represents a first demonstration of a nonenergetic role for dependence on fatty acid metabolism in cancer.This article is highlighted in the In This Issue feature, p. 2659.
Subject(s)
Acyl-CoA Dehydrogenase , Glioblastoma , Lipid Peroxidation , Mitochondria , Acyl-CoA Dehydrogenase/metabolism , Apoptosis , Fatty Acids/metabolism , Glioblastoma/enzymology , Glioblastoma/genetics , Humans , Mitochondria/metabolism , Oxidative StressABSTRACT
Inflammation is a major risk factor for pancreatic ductal adenocarcinoma (PDAC). When occurring in the context of pancreatitis, KRAS mutations accelerate tumor development in mouse models. We report that long after its complete resolution, a transient inflammatory event primes pancreatic epithelial cells to subsequent transformation by oncogenic KRAS. Upon recovery from acute inflammation, pancreatic epithelial cells display an enduring adaptive response associated with sustained transcriptional and epigenetic reprogramming. Such adaptation enables the reactivation of acinar-to-ductal metaplasia (ADM) upon subsequent inflammatory events, thereby limiting tissue damage through a rapid decrease of zymogen production. We propose that because activating mutations of KRAS maintain an irreversible ADM, they may be beneficial and under strong positive selection in the context of recurrent pancreatitis.
Subject(s)
Acinar Cells/pathology , Carcinogenesis , Carcinoma, Pancreatic Ductal/pathology , Genes, ras , Pancreas/pathology , Pancreatitis/physiopathology , Animals , Carcinoma, Pancreatic Ductal/genetics , Carcinoma, Pancreatic Ductal/immunology , Carcinoma, Pancreatic Ductal/physiopathology , Cell Transformation, Neoplastic , Cells, Cultured , Cellular Reprogramming , Chromatin/metabolism , Early Growth Response Protein 1/genetics , Early Growth Response Protein 1/metabolism , Enzyme Precursors/metabolism , Epigenesis, Genetic , Epithelial Cells/pathology , Epithelial Cells/physiology , Female , MAP Kinase Signaling System , Male , Metaplasia , Mice , Mutation , Pancreas/metabolism , Pancreatitis/genetics , Pancreatitis/immunology , Spheroids, Cellular , TranscriptomeABSTRACT
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer that has remained clinically challenging to manage. Here we employ an RNAi-based in vivo functional genomics platform to determine epigenetic vulnerabilities across a panel of patient-derived PDAC models. Through this, we identify protein arginine methyltransferase 1 (PRMT1) as a critical dependency required for PDAC maintenance. Genetic and pharmacological studies validate the role of PRMT1 in maintaining PDAC growth. Mechanistically, using proteomic and transcriptomic analyses, we demonstrate that global inhibition of asymmetric arginine methylation impairs RNA metabolism, which includes RNA splicing, alternative polyadenylation, and transcription termination. This triggers a robust downregulation of multiple pathways involved in the DNA damage response, thereby promoting genomic instability and inhibiting tumor growth. Taken together, our data support PRMT1 as a compelling target in PDAC and informs a mechanism-based translational strategy for future therapeutic development.Statement of significancePDAC is a highly lethal cancer with limited therapeutic options. This study identified and characterized PRMT1-dependent regulation of RNA metabolism and coordination of key cellular processes required for PDAC tumor growth, defining a mechanism-based translational hypothesis for PRMT1 inhibitors.
Subject(s)
Carcinoma, Pancreatic Ductal/genetics , DNA Damage , Pancreatic Neoplasms/genetics , Protein-Arginine N-Methyltransferases/genetics , RNA/genetics , Repressor Proteins/genetics , Animals , Biocatalysis/drug effects , Carcinoma, Pancreatic Ductal/metabolism , Carcinoma, Pancreatic Ductal/prevention & control , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Proliferation/genetics , Enzyme Inhibitors/pharmacology , Female , Humans , Mice, Inbred NOD , Mice, Knockout , Mice, SCID , Pancreatic Neoplasms/metabolism , Pancreatic Neoplasms/prevention & control , Protein-Arginine N-Methyltransferases/metabolism , RNA/metabolism , RNA Interference , Repressor Proteins/metabolism , Tumor Burden/drug effects , Xenograft Model Antitumor Assays/methodsABSTRACT
Break-induced replication (BIR) is an important process of DNA metabolism that has been implicated in the restart of collapsed replication forks, as well as in various chromosomal instabilities, including loss of heterozygosity, translocations, and alternative telomere lengthening. Therefore, knowledge of how BIR is carried out and regulated is important for better understanding the maintenance of genomic stability in eukaryotes. Here we present a new yeast experimental system that enables the genetic control of BIR to be investigated. Analysis of mutations selected on the basis of their sensitivity to various DNA-damaging agents demonstrated that deletion of POL32, which encodes a third, nonessential subunit of polymerase delta, significantly reduced the efficiency of BIR, although some POL32-independent BIR was still observed. Importantly, the BIR defect in pol32Delta cells was associated with the formation of half-crossovers. We propose that these half-crossovers resulted from aberrant processing of BIR intermediates. Furthermore, we suggest that the half-crossovers observed in our system are analogous to nonreciprocal translocations (NRTs) described in mammalian tumor cells and, thus, our system could represent an opportunity to further study the NRT mechanism in yeast.
Subject(s)
DNA Breaks, Double-Stranded , DNA Replication , Saccharomyces cerevisiae/genetics , DNA-Directed DNA Polymerase/genetics , DNA-Directed DNA Polymerase/metabolism , Models, Genetic , Mutation , Saccharomyces cerevisiae/enzymology , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolismABSTRACT
OBJECTIVE: To determine whether a 6-week Positivity Program could impact employee cardiovascular inflammation, blood sugars, cortisol, dehydroepiandrosterone (DHEA), and/or life satisfaction. METHODS: Pre- and post-study blood draw and life satisfaction questionnaire tracked changes in 10 cardiovascular and inflammatory biomarkers for 63 employees who participated in a 6-week Positivity Program comprised of three interventions: gratitude, HeartMath's Heart Lock-In, and yoga stretches with guided imagery. RESULTS: Improvements were recorded in life satisfaction as well as in seven of 10 cardiovascular and inflammatory biomarkers, including high sensitivity C-reactive protein (HsCRP) (-27%), hemoglobin A1c (HbA1c) (-1%), glucose (-2%), myeloperoxidase (MPO) (-5%), lipoprotein-associated phospholipase-A2 (Lp-PLA2) (-9%), apolipoprotein B (ApoB) (-6%), and DHEA (1%). No improvements were recorded in cortisol (11%), small-dense LDL (sdLDL) (0%), or oxidized LDL (OxLDL) (7%). CONCLUSIONS: Data suggest that engaging in 6 weeks of a workplace Positivity Program may improve employee life satisfaction, blood sugar levels, and some markers of cardiovascular inflammation.