Deletion Of PKM2 Research Articles

PKM2-Driven Lactate Overproduction Triggers Endothelial-To-Mesenchymal Transition in Ischemic Flap via Mediating TWIST1 Lactylation.

The accumulation of lactate is a rising risk factor for patients after flap transplantation. Endothelial-to-mesenchymal transition (EndoMT) plays a critical role in skin fibrosis. Nevertheless, whether lactate overproduction directly contributes to flap necrosis and its mechanism remain unknown. The current study reveals that skin flap mice exhibit enhanced PKM2 and fibrotic response. Endothelial-specific deletion of PKM2 attenuates flap necrosis and ameliorates flap fibrosis in mice. Administration of lactate or overexpressing PKM2 promotes dysfunction of endothelial cells and stimulates mesenchymal-like phenotype following hypoxia. Mechanistically, glycolytic-lactate induces a correlation between Twist1 and p300/CBP, leading to lactylation of Twist1 lysine 150 (K150la). The increase in K150la promotes Twist1 phosphorylation and nuclear translocation and further regulates the transcription of TGFB1, hence inducing fibrosis phenotype. Genetically deletion of endothelial-specific PKM2 in mice diminishes lactate accumulation and Twist1 lactylation, then attenuates EndoMT-associated fibrosis following flap ischemia. The serum lactate levels of flap transplantation patients are elevated and exhibit predictive value for prognosis. This findings suggested a novel role of PKM2-derived lactate in mediating Twist1 lactylation and exacerbates flap fibrosis and ischemia. Inhibition of glycolytic-lactate and Twist1 lactylation reduces flap necrosis and fibrotic response might become a potential therapeutic strategy for flap ischemia.

Aerobic glycolysis is the predominant means of glucose metabolism in neuronal somata, which protects against oxidative damage.

It is generally thought that under basal conditions, neurons produce ATP mainly through mitochondrial oxidative phosphorylation (OXPHOS), and glycolytic activity only predominates when neurons are activated and need to meet higher energy demands. However, it remains unknown whether there are differences in glucose metabolism between neuronal somata and axon terminals. Here, we demonstrated that neuronal somata perform higher levels of aerobic glycolysis and lower levels of OXPHOS than terminals, both during basal and activated states. We found that the glycolytic enzyme pyruvate kinase 2 (PKM2) is localized predominantly in the somata rather than in the terminals. Deletion of Pkm2 in mice results in a switch from aerobic glycolysis to OXPHOS in neuronal somata, leading to oxidative damage and progressive loss of dopaminergic neurons. Our findings update the conventional view that neurons uniformly use OXPHOS under basal conditions and highlight the important role of somatic aerobic glycolysis in maintaining antioxidant capacity.

Abstract 17777: Sorafenib Aggravates Atherosclerotic Progression Involving With Vascular Smooth Muscle Cell (VSMCs) Phenotypic Switching and Proliferation by PKM2-Mediated Glycolysis

Introduction: As a VEGF-targeting agent, sorafenib has been used to treat a number of solid tumors but can easily lead to adverse vascular effects, including hypertension, myocardiopathy and coronary artery spasm. Our previous study reveals that sorafenib impairs endothelium-dependent vasodilatation, whereas the effect of sorafenib on atherosclerotic progression has not been determined. Hypothesis: Hence, we hypothesize that sorafenib may promote atherosclerotic progression via such adverse vascular effects. Methods: ApoE -/- mice were orally administered by sorafenib for 12 weeks, indicating that sorafenib aggravates atherosclerotic progression via promoting the formation of foam cells and the accumulation of VSMCs in intima. To study the underlying mechanism, we used sorafenib to incubate VSMCs (0, 3 and 6 mg/L) for 48 h. Results: We found that sorafenib promoted the proliferation, migration and synthetic phenotype-related gene expression in VSMCs. More importantly, sorafenib increased lactate production, the extracellular acidification rate, PKM2 expression and PK activity in VSMCs. Interestingly, after deletion of PKM2 in VSMCs by AAV-CRISPR/Cas9 system, decreased lactate production and the extracellular acidification rate were found. Meanwhile, sorafenib-induced the proliferation, migration and phenotypic switching of VSMCs were suppressed. Conclusions: Sorafenib can aggravate atherosclerotic progression and smooth muscle cell phenotypic switching, which may be partly ascribed to PKM2-depended glycolysis.

Endothelial Cell-Derived Lactate Triggers Bone Mesenchymal Stem Cell Histone Lactylation to Attenuate Osteoporosis.

Blood vessels play a role in osteogenesis and osteoporosis; however, the role of vascular metabolism in these processes remains unclear. The present study finds that ovariectomized mice exhibit reduced blood vessel density in the bone and reduced expression of the endothelial glycolytic regulator pyruvate kinase M2 (PKM2). Endothelial cell (EC)-specific deletion of Pkm2 impairs osteogenesis and worsens osteoporosis in mice. This is attributed to the impaired ability of bone mesenchymal stem cells (BMSCs) to differentiate into osteoblasts. Mechanistically, EC-specific deletion of Pkm2 reduces serum lactate levels secreted by ECs, which affect histone lactylation in BMSCs. Using joint CUT&Tag and RNA sequencing analyses, collagen type I alpha 2 chain (COL1A2), cartilage oligomeric matrix protein (COMP), ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), and transcription factor 7 like 2 (TCF7L2) as osteogenic genes regulated by histone H3K18la lactylation are identified. PKM2 overexpression in ECs, lactate addition, and exercise restore the phenotype of endothelial PKM2-deficient mice. Furthermore, serum metabolomics indicate that patients with osteoporosis have relatively low lactate levels. Additionally, histone lactylation and related osteogenic genes of BMSCs are downregulated in patients with osteoporosis. In conclusion, glycolysis in ECs fuels BMSC differentiation into osteoblasts through histone lactylation, and exercise partially ameliorates osteoporosis by increasing serum lactate levels.

Glycolytic enzyme PKM2 regulates cell senescence but not inflammation in the process of osteoarthritis.

Chondrocyte senescence is an important mechanism underlying osteoarthritis in the senile population and is characterized by reduced expressions of the extracellular matrix proteins. The involvement of glycolysis and the tricarboxylic acid cycle in the development of osteoarthritis is inclusive. The present study aims to investigate the role of the glycolytic enzyme M2 isoform of pyruvate kinase (PKM2) in chondrocytes in senescence and inflammation. Primary chondrocytes are isolated from the knee joints of neonatal mice. Small interfering RNAs (siRNAs) against PKM2 are transfected using lipofectamine. RNA sequencing is conducted in primary chondrocytes with the PKM2 gene deleted. Cell apoptosis, autophagy, reactive oxygen species measurement, and senescent conditions are examined. The glycolytic rate in cells is measured by Seahorse examination. Interleukin 1-β (IL-1β) increases the protein expressions of matrix metallopeptidases (MMP)13 and PKM2 and reduces the protein expression of collagen type II (COL2A1) in primary chondrocytes. Silencing of PKM2 alters the protein expressions of MMP13, PKM2, and COL2A1 in the same pattern in quiescent and stimulated chondrocytes. RNA sequencing analysis reveals that PKM2 silencing reduces senescent biomarker p16 INK4a expression. Compared with low-passage chondrocytes, high-passage chondrocytes exhibit increased expression of p16 INK4a and reduced expression of COL2A1. Silencing of PKM2 reduces SA-β-Gal signals and increases COL2A1 expression in high-passage chondrocytes. Seahorse assay reveals that PKM2 deletion favors the tricarboxylic acid cycle in mitochondria in low- but not in high-passage chondrocytes. In summary, the glycolytic enzyme PMK2 modulates chondrocyte senescence but does not participate in the regulation of inflammation.

Abstract 10730: Pkm2 Ablation Dysregulates Cardiac Glucose Metabolism in Mice

Introduction: The predominant isoform of pyruvate kinase (PKM1) directs pyruvate to the Krebs cycle for oxidative metabolism in the healthy heart. Our lab described a hypoxia-mediated switch to the alternatively spliced isoform PKM2. The lower PKM activity of dimerized PKM2 redirects glycolytic metabolites to the pentose phosphate pathway (PPP) and lactate production. Recently, we have found that mice with deletion of Pkm2 had profound depletion of cardiac basal glucose and higher ROS levels compared to controls. Hypothesis: We hypothesize that glucose metabolism is dysregulated in the absence of Pkm2, where the remaining isoform PKM1 promotes oxidative metabolism, leading to accumulation of ROS. Methods: Global Pkm2 KO mice were used for this study. Transcript abundance was determined by RNA-seq and RT-qPCR. Cardiomyocytes were isolated according to an established Langendorff-free method, and metabolites were traced using [U- 13 C] glucose with LC/MS (n=3). ROS concentration was measured using DCFDA in cardiomyocytes incubated at 1% O 2 (n=4). Inflammatory marker C-reactive protein (CRP) was measured in plasma of mice before and after myocardial infarction (n=12). Results: Although glucose uptake was similar, glucose was redirected to fatty acid synthesis, the polyol pathway, and the PPP, and away from oxidative metabolism in Pkm2 KO cardiomyocytes. Despite the increased flux into the PPP, NADPH production was low. Assessment of ROS levels in normoxia revealed that Pkm2 KO cardiomyocytes had higher levels of ROS, possibly stimulating the inflammatory response in Pkm2 KO mice. CRP levels were higher in Pkm2 KO plasma at baseline. ROS remained high in Pkm2 KO cardiomyocytes after hypoxic treatment and CRP remained high in Pkm2 KO plasma after MI. Conclusions: Increased expression of Pkm1 in the Pkm2 KO mice increases flux of metabolites through oxidative metabolism, exacerbating mitochondrial ROS and activating the PPP. Although NADPH levels should have correlated with increased PPP flux, the low NADPH production in Pkm2 KO cardiomyocytes suggest rapid consumption of NADPH by ROS and fatty acid synthesis. This study suggests a role for hypoxia-stimulated PKM2 accumulation in stabilizing glucose flux to mitigate oxidative stress in the ischemic heart.

316-OR: Genetic Deletion of Beta-Cell Pkm1, Pkm2, and Pck2 Identifies PEP as an Essential Signal for Compartmentalized KATP Closure and Cycling of the Insulin Secretory Pathway

β-cells use pyruvate kinase to sense nutrients and respond with appropriate insulin secretion. Here, we used β-cell deletion to identify the functions of constitutively active PKm1 and allosterically recruitable PKm2, and assess their regulation by mitochondrial PEP from PCK2. We demonstrate that both PKm isoforms are present in the KATP channel microcompartment. Compartmentation nullifies the disparities in PK isoform expression and activity, allowing the minor but recruitable PKm2 isoform to fully participate in KATP regulation. However, this shared control does not extend to β-cell response to amino acids, which requires PKm1 for the initiation of Ca2+ influx and insulin secretion and PKm2 for their termination. Mitochondrial PEP is required for this cycling between “on” and “off” states, as demonstrated by β-cell-specific deletion of PCK2. PCK2 was revealed to be an essential mechanism of β-cell cataplerosis, possessing metabolic control over cytosolic ATP/ADP generation in response to anaplerotic fuels. Further, PCK2 is required for amino acid-stimulated Ca2+ influx (via PKm1) and efflux (via PKm2) . These data provide strong genetic evidence for a revised oscillatory model of β-cell metabolism in which PKM1- and PKM2-driven PEP cycles play unique roles in the initiation and termination of nutrient-stimulated insulin secretion. Disclosure H.R.Foster: None. T.Ho: None. E.Potapenko: None. R.L.Cardone: n/a. R.Kibbey: Consultant; Agios, Inc. M.J.Merrins: None. Funding NIH/NIDDK (R01DK113103) HRSA (T32HP10010) NIH/NIA (T32AG000213)

Pyruvate Kinase M1 Suppresses Development and Progression of Prostate Adenocarcinoma.

Differential expression of PKM1 and PKM2 impacts prostate tumorigenesis and suggests a potential therapeutic vulnerability in prostate cancer.

Myeloid Cell PKM2 Deletion Enhances Efferocytosis and Reduces Atherosclerosis

Myeloid Cell PKM2 Deletion Enhances Efferocytosis and Reduces Atherosclerosis

PKM2-dependent metabolic skewing of hepatic Th17 cells regulates pathogenesis of non-alcoholic fatty liver disease

Emerging evidence suggests a key contribution to non-alcoholic fatty liver disease (NAFLD) pathogenesis by Th17 cells. The pathogenic characteristics and mechanisms of hepatic Th17 cells, however, remain unknown. Here, we uncover and characterize a distinct population of inflammatory hepatic CXCR3+Th17 (ihTh17) cells sufficient to exacerbate NAFLD pathogenesis. Hepatic ihTh17 cell accrual was dependent on the liver microenvironment and CXCR3 axis activation. Mechanistically, the pathogenic potential of ihTh17 cells correlated with increased chromatin accessibility, glycolytic output, and concomitant production of IL-17A, IFNγ, and TNFα. Modulation of glycolysis using 2-DG or cell-specific PKM2 deletion was sufficient to reverse ihTh17-centric inflammatory vigor and NAFLD severity. Importantly, ihTh17 cell characteristics, CXCR3 axis activation, and hepatic expression of glycolytic genes were conserved in human NAFLD. Together, our data show that the steatotic liver microenvironment regulates Th17 cell accrual, metabolism, and competence toward an ihTh17 fate. Modulation of these pathways holds potential for development of novel therapeutic strategies for NAFLD.

Myeloid-Specific PKM2 Deletion Reduces Kidney Damage in Oxalate-Induced AKI

Myeloid-Specific PKM2 Deletion Reduces Kidney Damage in Oxalate-Induced AKI

Pkm2 Regulates Cardiomyocyte Cell Cycle and Promotes Cardiac Regeneration.

The adult mammalian heart has limited regenerative capacity, mostly attributable to postnatal cardiomyocyte cell cycle arrest. In the last 2 decades, numerous studies have explored cardiomyocyte cell cycle regulatory mechanisms to enhance myocardial regeneration after myocardial infarction. Pkm2 (Pyruvate kinase muscle isoenzyme 2) is an isoenzyme of the glycolytic enzyme pyruvate kinase. The role of Pkm2 in cardiomyocyte proliferation, heart development, and cardiac regeneration is unknown. We investigated the effect of Pkm2 in cardiomyocytes through models of loss (cardiomyocyte-specific Pkm2 deletion during cardiac development) or gain using cardiomyocyte-specific Pkm2 modified mRNA to evaluate Pkm2 function and regenerative affects after acute or chronic myocardial infarction in mice. Here, we identify Pkm2 as an important regulator of the cardiomyocyte cell cycle. We show that Pkm2 is expressed in cardiomyocytes during development and immediately after birth but not during adulthood. Loss of function studies show that cardiomyocyte-specific Pkm2 deletion during cardiac development resulted in significantly reduced cardiomyocyte cell cycle, cardiomyocyte numbers, and myocardial size. In addition, using cardiomyocyte-specific Pkm2 modified RNA, our novel cardiomyocyte-targeted strategy, after acute or chronic myocardial infarction, resulted in increased cardiomyocyte cell division, enhanced cardiac function, and improved long-term survival. We mechanistically show that Pkm2 regulates the cardiomyocyte cell cycle and reduces oxidative stress damage through anabolic pathways and β-catenin. We demonstrate that Pkm2 is an important intrinsic regulator of the cardiomyocyte cell cycle and oxidative stress, and highlight its therapeutic potential using cardiomyocyte-specific Pkm2 modified RNA as a gene delivery platform.

Loss of PKM2 in Lgr5+ intestinal stem cells promotes colitis-associated colorectal cancer

The regulatory properties of pyruvate kinase M2 isoform (PKM2), the key glycolytic enzyme, influence altered energy metabolism including glycolysis in cancer. In this study, we found that PKM2 was highly expressed in patients with ulcerative colitis or colorectal cancer (CRC). We then investigated the effectiveness of conditionally ablating PKM2 in Lgr5+ intestinal stem cells (ISC) using a mouse model of colitis-associated CRC (AOM plus DSS). Tamoxifen-inducible Lgr5-driven deletion of PKM2 in ISC (PKM2ΔLgr5-Tx) significantly promoted tumor incidence and size in the colon and lower body weight compared with findings in vehicle-treated mice (PKM2ΔLgr5-Veh). Histopathologic analysis revealed considerable high-grade dysplasia and adenocarcinoma in the colon of PKM2ΔLgr5-Tx mice while PKM2ΔLgr5-Veh mice had low- and high-grade dysplasia. Loss of PKM2 was associated with dominant expression of PKM1 in Lgr5+ ISC and their progeny cells. Further, the organoid-forming efficiency of whole cancer cells or Lgr5+ cells obtained from colon polyps of PKM2ΔLgr5-Tx mice was significantly increased when compared with PKM2ΔLgr5-Veh mice. Cancer organoids from PKM2ΔLgr5-Tx mice exhibited increased mitochondrial oxygen consumption and a shift of metabolites involved in energy metabolism. These findings suggest that loss of PKM2 function in ISC promotes colitis-associated CRC.

PKM2 is not required for pancreatic ductal adenocarcinoma

BackgroundWhile most cancer cells preferentially express the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2), PKM2 is dispensable for tumor development in several mouse cancer models. PKM2 is expressed in human pancreatic cancer, and there have been conflicting reports on the association of PKM2 expression and pancreatic cancer patient survival, but whether PKM2 is required for pancreatic cancer progression is unknown. To investigate the role of PKM2 in pancreatic cancer, we used a conditional allele to delete PKM2 in a mouse model of pancreatic ductal adenocarcinoma (PDAC).ResultsPDAC tumors were initiated in LSL-KrasG12D/+;Trp53flox/flox;Pdx-1-Cre (KP−/−C) mice harboring a conditional Pkm2 allele. Immunohistochemical analysis showed PKM2 expression in wild-type tumors and loss of PKM2 expression in tumors from Pkm2 conditional mice. PKM2 deletion had no effect on overall survival or tumor size. Loss of PKM2 resulted in pyruvate kinase M1 (PKM1) expression, but did not affect the number of proliferating cells. These findings are consistent with results in other cancer models.ConclusionsPKM2 is not required for initiation or growth of PDAC tumors arising in the KP−/−C pancreatic cancer model. These findings suggest that, in this mouse PDAC model, PKM2 expression is not required for pancreatic tumor formation or progression.

Activation of PKM2 Protects against Diabetic Kidney Disease from Mice to Men

We have reported that up-regulation of PKM2 in renal glomeruli isolated from patients with more than 50 years of type 1 diabetes (Joslin Medalist Study) correlated with preservation of renal function even in the presence of chronic hyperglycemia. Further, pharmacological activation of PKM2 in T1D mice and podocyte-specific deletion of PKM2 in cultured cells and in vivo strongly showed that PKM2 activation protects renal glomeruli from hyperglycemia/diabetes induced damage (Nat. Med 2017). To confirm these findings in type 1 and type 2 diabetes, we performed the following: 1. We showed the protein expressions of glycolytic (PKM1, PKM2, ENO1) and mitochondrial (MTCO2) enzymes to be significantly elevated in glomeruli of post mortem kidneys in people with T2D without DN compared to those with DN, or nondiabetic controls. 2. Plasma PKM2 levels (SomaLogic aptamer assay) in the Medalists (n=180) correlated with albumin-to-creatinine ratio (ACR;p=0.03) and eGFR (p=0.0002) at baseline. In a replication cohort (n=219) of patients with T1D in the longitudinal Joslin Kidney Study (JKS) baseline plasma PKM2 also correlated with ACR (p=0.0001). High baseline plasma PKM2 in JKS was independently associated with a slower decline in eGFR (p=0.004) and a slower progression to end-stage renal disease (p=0.0002). 3. TEPP-46, a PKM2 activator, prevented diabetes induced increases in mRNA expression of pro-fibrotic (Col3a1, Fn1, TGFb1) and inflammatory (Ccl2) genes, and enhanced key mitochondrial protein (Ppargc1a) in uninephrectomized T2D db/db mice. No differences in ACR were observed between TEPP-46 treated and untreated diabetic mice. These findings support the hypothesis that PKM2 activation may protect or even reverse the initiation and progression of diabetic glomerular dysfunction and pathology in both T1D and T2D, suggesting that activating PKM2 could be a clinically effective therapeutic target to stop the progression of DN. Disclosure D. Gordin: None. T. Shinjo: None. R. St-Louis: None. W. Qi: None. L.J. Tinsley: None. D.M. Pober: None. M.J. Brissett: None. M. Niewczas: None. J. Dreyfuss: None. H. Pan: None. T. Sadowski: Employee; Self; Sanofi. A. Kannt: Employee; Self; Sanofi. Stock/Shareholder; Self; Sanofi. H. Shah: None. H.A. Keenan: Research Support; Self; Sanofi. Employee; Self; Sanofi Genzyme. A. Krolewski: None. G.L. King: Research Support; Self; Sanofi-Aventis.

Isoform-specific deletion of PKM2 constrains tumor initiation in a mouse model of soft tissue sarcoma

BackgroundAlternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of the glycolytic enzyme pyruvate kinase. PKM2 expression is associated with embryogenesis, tissue regeneration, and cancer. PKM2 is also the pyruvate kinase isoform expressed in most wild-type adult tissues, with PKM1 restricted primarily to skeletal muscle, heart, and brain. To interrogate the functional requirement for PKM2 during tumor initiation in an autochthonous mouse model for soft tissue sarcoma (STS), we used a conditional Pkm2 allele (Pkm2fl) to abolish PKM2 expression.ResultsPKM2 deletion slowed tumor onset but did not abrogate eventual tumor outgrowth. PKM2-null sarcoma cells expressed PKM1 with tumors containing a high number of infiltrating PKM2 expressing stromal cells. End-stage PKM2-null tumors showed increased proliferation compared to tumors with a wild-type Pkm2 allele, and tumor metabolite analysis revealed metabolic changes associated with PKM2 loss.ConclusionsWhile PKM2 is not required for soft tissue sarcoma growth, PKM2 expression may facilitate initiation of this tumor type. Because these data differ from what has been observed in other cancer models where PKM2 has been deleted, they argue that the consequences of PKM2 loss during tumor initiation are dependent on the tumor type.

PKM2 is not required for colon cancer initiated by APC loss

BackgroundCancer cells express the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2). PKM2 expression is not required for some cancers, and PKM2 loss can promote cancer progression; however, PKM2 has been reported to be essential in other tumor contexts, including a proposed non-metabolic role in β-catenin nuclear translocation. PKM2 is expressed in colon cancers where loss of the Apc tumor suppressor results in β-catenin nuclear translocation and aberrant activation of the canonical Wnt signaling pathway. Whether PKM2 is required in this colon cancer context has not been investigated.ResultsColon tumorigenesis was induced in mice harboring conditional Apc and Pkm2 alleles, and tumor progression was monitored by serial colonoscopy. PKM2 deletion had no effect on overall survival, the number of mice that developed tumors, or the number of tumors that developed per animal. Immunohistochemical analysis demonstrated PKM2 expression in wild-type tumors and the expected loss of PKM2 expression in tumors from Pkm2 conditional mice. Loss of PKM2 resulted in pyruvate kinase M1 expression but had no effect on nuclear β-catenin staining. These findings are consistent with tumor growth and activated Wnt signaling despite PKM2 loss in this model. We also found a large fraction of human colon cancers had very low or undetectable levels of PKM2 expression.ConclusionsPKM2 is not required for Apc-deficient colon cancer or for nuclear translocation of β-catenin in Apc-null tumor cells. These findings suggest that PKM2 expression is not required for colon tumor formation or progression.

Pyruvate Kinase Inhibits Proliferation during Postnatal Cerebellar Neurogenesis and Suppresses Medulloblastoma Formation.

Aerobic glycolysis supports proliferation through unresolved mechanisms. We have previously shown that aerobic glycolysis is required for the regulated proliferation of cerebellar granule neuron progenitors (CGNP) and for the growth of CGNP-derived medulloblastoma. Blocking the initiation of glycolysis via deletion of hexokinase-2 (Hk2) disrupts CGNP proliferation and restricts medulloblastoma growth. Here, we assessed whether disrupting pyruvate kinase-M (Pkm), an enzyme that acts in the terminal steps of glycolysis, would alter CGNP metabolism, proliferation, and tumorigenesis. We observed a dichotomous pattern of PKM expression, in which postmitotic neurons throughout the brain expressed the constitutively active PKM1 isoform, while neural progenitors and medulloblastomas exclusively expressed the less active PKM2. Isoform-specific Pkm2 deletion in CGNPs blocked all Pkm expression. Pkm2-deleted CGNPs showed reduced lactate production and increased SHH-driven proliferation. 13C-flux analysis showed that Pkm2 deletion reduced the flow of glucose carbons into lactate and glutamate without markedly increasing glucose-to-ribose flux. Pkm2 deletion accelerated tumor formation in medulloblastoma-prone ND2:SmoA1 mice, indicating the disrupting PKM releases CGNPs from a tumor-suppressive effect. These findings show that distal and proximal disruptions of glycolysis have opposite effects on proliferation, and that efforts to block the oncogenic effect of aerobic glycolysis must target reactions upstream of PKM. Cancer Res; 77(12); 3217-30. ©2017 AACR.

PKM2 promotes tumor angiogenesis by regulating HIF-1α through NF-κB activation.

BackgroundInitially identified as a molecule that regulates the final step of glycolysis, the M2 isoform of pyruvate kinase (PKM2) was recently reported to have a central role in the metabolic reprogramming of cancer cells as well as participating in cell cycle progression and gene transcription. Despite intensive efforts, the intricate molecular mechanisms through which PKM2 regulates tumor progression remain elusive.MethodsThe proliferation and apoptosis of various pancreatic cancer cells using lentiviral-mediated PKM2 abrogation were assessed in vitro via Western blot and flow cytometric assay while the in vivo experiments involved tumor xenograft on chicken chorionallantoic membranes and immunohistochemistry on human tissue specimens. In order to decipher the molecular mechanism of HIF-1α and p65/RelA regulation by PKM2 in cancer cells cultivated in hypoxic atmosphere or normoxia we involved various biochemical assays such as Western blotting, immunoprecipitation, reporter gene assay and ELISA.ResultsStrong expression of PKM2 was observed in 68 % of human pancreatic adenocarcinoma specimens and almost all analyzed pancreatic cancer cell lines. Abrogation of PKM2 resulted in impaired proliferation and augmented apoptosis in vitro as well as impaired tumor growth and decreased blood vessel formation in vivo. Furthermore, deletion of PKM2 negatively impacted hypoxia-induced HIF-1α accumulation and promoter activity ultimately resulting in impaired secretion of VEGF.ConclusionsOur study suggests that in hypoxic pancreatic tumors PKM2 interferes both with NF-κB/p65 and HIF-1α activation that ultimately triggers VEGF-A secretion and subsequent blood vessel formation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-015-0490-2) contains supplementary material, which is available to authorized users.

PM-06 * DIFFERENTIAL SPLICING OF PYRUVATE KINASE REGULATES PROGENITOR CELL CYCLE AND MEDULLOBLASTOMA TUMORIGENESIS

BACKGROUND: We have previously shown that aerobic glycolysis, a hallmark of cancer metabolism, plays a physiological role in postnatal neurogenesis and is co-opted in medulloblastoma. Medulloblastoma, the most common malignant brain tumor in children, arises from cerebellar progenitors that normally proliferate in the first year of life then exit the cell cycle. Processes that regulate the developmental proliferation of neural progenitors may facilitate tumorigenesis when activated aberrantly. We have identified Pyruvate kinase isoform M2 (PKM2) as a developmentally-regulated enzyme that accelerates medulloblastoma tumorigenesis in a mouse model and is a potential target for novel cancer therapies. METHODS: We examined metabolism and proliferation in mice with and without a conditional deletion of PkM2 using NMR-based metabolomics, immunohistochemistry and Western blot. We examined the importance of PkM2 in medulloblastoma tumorigenesis by analyzing the survival of medulloblastoma-prone ND2: SmoA1 mice with and without PkM2 deletion. RESULTS: Brain progenitors specifically splice the PkM gene into the less catalytically active PkM2 isoform, while differentiated neurons uniformly express the constituently active isoform PkM1. Deletion of PkM2 altered energy metabolism, reducing lactic acid production and increasing glutamine consumption. Despite reduced aerobic glycolysis, PkM2-deleted progenitors proliferated more rapidly. In tumor-prone mice, PkM2 deletion accelerated medulloblastoma tumorigenesis and shortened survival. CONCLUSIONS: Our findings of increased tumorigenesis in PkM2-deleted mice demonstrate that PkM2 activity is not required for tumor formation. Further, the generation of lactic acid, per se, does not enhance tumorigenesis. Rather, we propose that PkM2 functions as a less active Pyruvate Kinase isozyme that channels glycolytic intermediates into alternative metabolic fates to support proliferation. Accordingly, splicing PkM into the PkM2 isoform reduces PkM activity in progenitors, and PkM2 deletion enhances this phenotype, accelerating tumor formation in ND2:SmoA1 mice. Strategies that increase PkM2 enzymatic activity may conversely inhibit medulloblastoma growth, providing a novel, metabolic approach to anti-tumor therapy.