Project description:In order to propagate a solid tumor, cancer cells must adapt to and survive under various tumor microenvironment (TME) stresses, such as hypoxia or lactic acidosis. To systematically identify genes that modulate cancer cell survival under stresses, we performed genome-wide shRNA screens under hypoxia or lactic acidosis. We discovered that genetic depletion of acetyl-CoA carboxylase (ACACA or ACC1) or ATP citrate lyase (ACLY) protected cancer cells from hypoxia-induced apoptosis. Additionally, loss of ACLY or ACC1 reduced levels and activities of the oncogenic transcription factor ETV4. Silencing ETV4 also protected cells from hypoxia-induced apoptosis and led to remarkably similar transcriptional responses as with silenced ACLY or ACC1, including an anti-apoptotic program. Metabolomic analysis found that while α-ketoglutarate levels decrease under hypoxia in control cells, α-ketoglutarate is paradoxically increased by hypoxia when ACC1 or ACLY are depleted. Supplementation with α-ketoglutarate rescued the hypoxia-induced apoptosis and recapitulated the decreased expression and activity of ETV4 via an epigenetic mechanism. Therefore, ACC1 and ACLY regulate the levels of ETV4 under hypoxia via increased α-ketoglutarate. These results reveal that ACC1/ACLY- α-ketoglutarate-ETV4 is a novel means by which metabolic states regulate transcriptional output for life vs. death decisions under hypoxia. Since many lipogenic inhibitors are under investigation as cancer therapeutics, our findings suggest that the use of these inhibitors will need to be carefully considered with respect to oncogenic drivers, tumor hypoxia, progression and dormancy. More broadly, our screen provides a framework for studying additional tumor cell stress-adaption mechanisms in the future. DESIGN: H1975 lung cancer cells transduced with a scramble shRNA hairpin or two different shRNAs against ACLY, ACC1, or ETV4 under hypoxia.
Project description:In order to propagate a solid tumor, cancer cells must adapt to and survive under various tumor microenvironment (TME) stresses, such as hypoxia or lactic acidosis. To systematically identify genes that modulate cancer cell survival under stresses, we performed genome-wide shRNA screens under hypoxia or lactic acidosis. We discovered that genetic depletion of acetyl-CoA carboxylase (ACACA or ACC1) or ATP citrate lyase (ACLY) protected cancer cells from hypoxia-induced apoptosis. Additionally, loss of ACLY or ACC1 reduced levels and activities of the oncogenic transcription factor ETV4. Silencing ETV4 also protected cells from hypoxia-induced apoptosis and led to remarkably similar transcriptional responses as with silenced ACLY or ACC1, including an anti-apoptotic program. Metabolomic analysis found that while α-ketoglutarate levels decrease under hypoxia in control cells, α-ketoglutarate is paradoxically increased by hypoxia when ACC1 or ACLY are depleted. Supplementation with α-ketoglutarate rescued the hypoxia-induced apoptosis and recapitulated the decreased expression and activity of ETV4 via an epigenetic mechanism. Therefore, ACC1 and ACLY regulate the levels of ETV4 under hypoxia via increased α-ketoglutarate. These results reveal that ACC1/ACLY- α-ketoglutarate-ETV4 is a novel means by which metabolic states regulate transcriptional output for life vs. death decisions under hypoxia. Since many lipogenic inhibitors are under investigation as cancer therapeutics, our findings suggest that the use of these inhibitors will need to be carefully considered with respect to oncogenic drivers, tumor hypoxia, progression and dormancy. More broadly, our screen provides a framework for studying additional tumor cell stress-adaption mechanisms in the future.
Project description:Differentiation of cardiac fibroblasts (CFs) to myofibroblasts is necessary for matrix remodeling and fibrosis in heart failure. We previously reported mitochondrial calcium signaling drives α-ketoglutarate-dependent histone demethylation, promoting the myofibroblast gene program. Here, we investigated the role of ATP-citrate lyase (ACLY), a key enzyme for acetyl-CoA biosynthesis, in histone acetylation regulating myofibroblast formation and persistence in cardiac fibrosis. Inactivation of ACLY prevented, and importantly reversed, myofibroblasts towards quiescence. Genetic deletion of Acly in activated myofibroblasts prevented fibrosis and preserved cardiac function in murine pressure-overload. TGFβ stimulation enhanced ACLY nuclear localization and increased H3K27ac at fibrotic gene loci. Pharmacological inhibition of ACLY or forced nuclear expression of dominant-negative ACLY mutant prevented myofibroblast formation and H3K27ac. Our data indicate nuclear ACLY activity is necessary for myofibroblast differentiation and persistence by maintaining histone acetylation at TGFβ-induced myofibroblast genes. These findings provide novel clinical rational to prevent and reverse pathological fibrosis. CUT&RUN Sequencing for H3K27ac on the role of ACLY in myofibroblast differentiaton.
Project description:In this study we report the gene expression profile and MISO analysis for alternative splicing events such as exon skipping in iPSC-derived cardiomyocytes which were treated with a drug inhibiting α-ketoglutarate-dependent hydroxylases (dimethyloxalylglycine) and compared to vehicle control. α-ketoglutarate-dependent hydroxylase inhibition plays a central role in cardiac hypoxia and the goal of this study was to identify new pathways in hypoxia beyond HIF-1α.
Project description:2-oxoglutarate (2-OG or α-ketoglutarate) relates mitochondrial metabolism to cell function by modulating the activity of 2-OG dependent dioxygenases involved in the hypoxia response and DNA/histone modifications. However, metabolic pathways that regulate these oxygen and 2-OG sensitive enzymes remain poorly understood. Here, using CRISPR Cas9 genome-wide utagenesis to screen for genetic determinants of 2-OG levels, we uncover a redox sensitive mitochondrial lipoylation pathway, dependent on the mitochondrial hydrolase ABHD11, that signals changes in mitochondrial 2-OG metabolism to 2-OG dependent dioxygenase function. ABHD11 loss or inhibition drives a rapid increase in 2-OG levels by impairing lipoylation of the 2-OG dehydrogenase complex (OGDHc) – the rate limiting step for mitochondrial 2-OG metabolism. Rather than facilitating lipoate conjugation, ABHD11 associates with the OGDHc and maintains catalytic activity of lipoyl domain by preventing the formation of lipoyl adducts, highlighting ABHD11 as a regulator of functional lipoylation and 2-OG metabolism.
Project description:The tumor suppressor p53 is mutated in the majority of human cancers, including pancreatic ductal adenocarcinoma (PDAC)1,2. Wild-type p53 accumulates in response to cellular stress and acts to regulate the expression of genes that influence cell fate and constrain tumorigenesis2. p53 also can modulate cellular metabolism3, though it remains unclear how the metabolic effects of p53 influence tumor suppression or whether the metabolic consequences of p53 loss play a role in disease maintenance. Here, we show that restoring endogenous p53 function in cancer cells derived from a mouse model of PDAC driven by oncogenic Kras and a regulatable p53 short hairpin RNA (shRNA) rewires glucose and glutamine metabolism to support the accumulation of the metabolite alpha-ketoglutarate, an obligate substrate for several enzymes that regulate chromatin methylation. p53 restoration induces transcriptional programs characteristic of pre-neoplastic differentiation, an effect that can be partially recapitulated by addition of cell permeable alpha-ketoglutarate. Consequently, enforcing alpha-ketoglutarate accumulation in p53 deficient cells by inhibiting expression of oxoglutarate dehydrogenase (Ogdh), the enzyme that consumes alpha-ketoglutarate in the tricarboxylic acid cycle, reduces tumor-initiating capacity and promotes tumor differentiation in vivo. In both mouse and human pancreatic cancer, decreasing levels of the alpha-ketoglutarate-dependent chromatin modification 5-hydroxymethylcytosine (5hmC) marks progression from prenoplastic to de-differentiated malignant lesions. p53 restoration or Ogdh suppression promotes accumulation of 5hmC specifically in differentiated tumor cells in vivo. Together, these results nominate alpha-ketoglutarate as an effector of p53-mediated tumor suppression that promotes pre-neoplastic differentiation and suppresses malignant progression.
Project description:De novo lipogenesis is activated in most cancers. Several lipogenic enzymes are implicated in oncogenesis and represent potential cancer therapeutic targets. RNA interference-mediated depletion of ATP citrate lyase (ACLY), the enzyme that catalyzes the first step of de novo lipogenesis, leads to growth suppression in a subset of human cancer cells. Here we demonstrate the molecular basis and potential biomarkers for ACLY-targeting therapy. First, suppression of cancer cell growth by ACLY depletion involves down-regulation of fatty acid elongase ELOVL6 at the transcriptional level. Lipid profiling revealed that ACLY depletion alters fatty acid composition in triglyceride; increased palmitate and decreased longer fatty acids, in accordance with ELOVL6 down-regulation. Second, ACLY depletion increases reactive oxygen species (ROS), whereas addition of antioxidant reduces ROS and attenuates the growth suppression. Third, ACLY depletion or ROS stimulation induce phosphorylation of AMP-activated protein kinase (AMPK), a sensor of energy and lipid metabolism. Analysis of various cancer cell lines revealed that the levels of AMPK phosphorylation (p-AMPK) correlate with the basal ROS levels, and that cancer cells with low basal p-AMPK (i.e., low basal ROS) levels are highly susceptible to ACLY depletion-mediated growth suppression. Finally, in clinical colon cancer tissues, p-AMPK levels are significantly decreased in aggressive tumors and correlate with the levels of 8-hydroxydeoxyguanosine, a hallmark of ROS stimulation. Together, these data suggest that ACLY inhibition suppresses cancer growth via palmitate-mediated lipotoxicity, and p-AMPK could be a predictive biomarker for its therapeutic outcome. Two cell lines are treated with ACLY siRNA. The samples include controls of each cell line.
Project description:ABL1 kinase inhibitors such as imatinib mesylate (IM) are effective in managing chronic myelogenous leukemia (CML) but incapable of eliminating leukemia stem cells (LSCs), suggesting that kinase−independent pathways support LSC survival. Given that the bone marrow hypoxic microenvironment supports hematopoietic stem cells, we investigated if hypoxia similarly contributes to LSC persistence. Importantly, we found that while BCR−ABL1 kinase remained effectively inhibited by IM under hypoxia, apoptosis became partially suppressed. Furthermore, hypoxia enhanced the clonogenicity of CML cells, as well as their efficiency in repopulating immunodeficient mice, both in the presence and absence of IM. HIF1−α, which is the master regulator of the hypoxia transcriptional response is expressed in the bone marrow specimens of CML individuals. In vitro, HIF1−α is stabilized during hypoxia and its expression and transcriptional activity can be partially attenuated by concurrent IM treatment. Expression analysis demonstrates at the whole transcriptome level that hypoxia and IM regulate distinct subsets of genes. Functionally, knockdown of HIF1−α abolished the enhanced clonogenicity during hypoxia. Taken together, our results suggest that in the hypoxic microenvironment, HIF1−α signaling supports LSC persistence independently of BCR−ABL1 kinase activity. Thus targeting HIF1−α and its pathway components may be therapeutically important for the complete eradication of LSCs.