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:The tumor suppressor TP53 is mutated in the majority of human cancers, including over 70% of pancreatic ductal adenocarcinoma (PDAC). Wild-type p53 accumulates in response to cellular stress and regulates the expression of genes that alter cell fate and constrain tumorigenesis. p53 also modulates several cellular metabolic pathways, though it remains unclear whether particular p53-regulated metabolites contribute to tumor suppression or whether metabolic alterations driven by p53 mutation sustain cancer progression. Here, we show that restoring endogenous p53 function in cancer cells derived from a murine PDAC model driven by oncogenic Kras and a regulatable p53 short hairpin RNA (shRNA) rewires glucose and glutamine metabolism leading to the accumulation of α-ketoglutarate (αKG), an obligate substrate for several chromatin modifying enzymes. p53 induces transcriptional programs characteristic of premalignant differentiation, an effect that can be partially recapitulated by addition of cell permeable αKG. Similarly, enforcing αKG accumulation in p53-deficient PDAC cells though the inhibition of oxoglutarate (αKG) dehydrogenase (Ogdh), the enzyme that consumes αKG in the tricarboxylic acid cycle, reduces tumor-initiating capacity and promotes tumor cell differentiation. Decreases in 5-hydroxymethylcytosine (5hmC), an αKG-dependent chromatin modification, are associated with the appearance of p53 mutations in the transition from premalignant to de-differentiated malignant lesions, whereas increases in 5hmC accompany tumor cell differentiation triggered by either p53 restoration or Ogdh depletion. Together these data nominate αKG as an effector of p53-mediated tumor suppression whose accumulation in p53-deficient tumors can drive tumor cell differentiation and antagonize malignant progression.
Project description:Tet3 is an Fe2+-dependent enzyme that oxidizes genomic 5-methylcytosine to 5-hydroxymethylcytosine with the help of alpha-ketoglutarate and oxygen. It is the most abundant Tet enzyme in differentiated tissues including brain. Adult brain contains the highest 5-hydroxymethylcytosine levels. How alpha-ketoglutarate is made available for the oxidation of mC in brain cells and how the Tet activity is linked to neural activity are unsolved questions. Our experiments with full mouse brains show that Tet3 interacts in the nucleus directly with selected enzymes of the mitochondrial citric acid cycle. This leads to the formation of isocitrate. Tet3 also interacts with aspartate aminotransferase, which produces oxaloacetate. Although oxaloacetate and isocitrate are biosynthetic alpha-ketoglutarate precursors, they function as inhibitors of Tet3 and are needed to protect the reactive Fe2+ center from degrading DNA. The supply of Tet3 with alpha-ketoglutarate is established by a direct interaction of Tet3 with glutamate dehydrogenase (Glud1), which converts the neurotransmitter glutamate directly into alpha-ketoglutarate. This links Tet3 function to neural activity.
Project description:We conducted gene expression analysis of naive and polarized macrophages from wild type C57BL6/J mice. In this project, we also compared how glutamine deprivation and production of alpha-ketoglutarate during LPS priming affects gene expression profiles in bone marrow-derived macrophages.
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:In order to investigate the effect of Alpha-Ketoglutarate (AKG) on p-α-synuclein in substantia nigra of Parkinson's disease (PD) model mice (C57BL/6), we profiled substantia nigra from wild-type (WT), AAV-α-synuclein (α-Syn), AKG and α-Syn-AKG in male mice by RNA sequencing (RNA-seq).