Germline loss of PKM2 promotes metabolic distress and hepatocellular carcinoma
Ontology highlight
ABSTRACT: Alternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of pyruvate kinase, and PKM2 expression is closely linked to embryogenesis, tissue regeneration, and cancer. To interrogate the functional requirement for PKM2 during development and tissue homeostasis, we generated germline PKM2 null mice (Pkm2-/-). Unexpectedly, despite being the primary isoform expressed in most wild-type adult tissues, we found that Pkm2-/- mice are viable and fertile. Thus, PKM2 is not required for embryonic or postnatal development. Loss of PKM2 leads to compensatory expression of PKM1 in the tissues that normally express PKM2. Strikingly, PKM2 loss leads to spontaneous development of hepatocellular carcinoma (HCC) with high penetrance that is accompanied by progressive changes in systemic metabolism characterized by altered systemic glucose homeostasis, inflammation, and hepatic steatosis. Therefore, in addition to its role in cancer metabolism, PKM2 plays a role in controlling systemic metabolic homeostasis and inflammation, thereby preventing HCC by a non-cell-autonomous mechanism. RNA was isolated from flash frozen ground whole liver tissue of 35 week old PKM2 KO and WT mice. Three independent mice from each condition were used as biological replicates.
Project description:Alternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of pyruvate kinase, and PKM2 expression is closely linked to embryogenesis, tissue regeneration, and cancer. To interrogate the functional requirement for PKM2 during development and tissue homeostasis, we generated germline PKM2 null mice (Pkm2-/-). Unexpectedly, despite being the primary isoform expressed in most wild-type adult tissues, we found that Pkm2-/- mice are viable and fertile. Thus, PKM2 is not required for embryonic or postnatal development. Loss of PKM2 leads to compensatory expression of PKM1 in the tissues that normally express PKM2. Strikingly, PKM2 loss leads to spontaneous development of hepatocellular carcinoma (HCC) with high penetrance that is accompanied by progressive changes in systemic metabolism characterized by altered systemic glucose homeostasis, inflammation, and hepatic steatosis. Therefore, in addition to its role in cancer metabolism, PKM2 plays a role in controlling systemic metabolic homeostasis and inflammation, thereby preventing HCC by a non-cell-autonomous mechanism.
Project description:The pyruvate kinase M2 isoform (PKM2) is preferentially expressed in cancer to regulate anabolic metabolism. However, the metabolic requirements of PKM2 in tumorigenesis have yielded contradictory results. Herein we discovered that this glycolytic enzyme regulates lipid homeostasis in cancer cell autonomous manner and at systemic levels. Transmembrane protein 33 (TMEM33) was identified as a downstream effector of PKM2, whose expression level positively correlates with plasma total cholesterol level in vivo. Loss of PKM2 leads to up-regulation of TMEM33, which recruits ring finger protein 5 (RNF5) to promote SCAP ubiquitination and degradation, thereby inhibiting Golgi translocation and activation of sterol regulatory element binding protein 1 (SREBP1). Moreover, global PKM2 knockout promoted allografted tumor growth, at least partially attributes to the elevated plasma cholesterol level caused by increased intestinal Niemann-Pick C1-Like 1 (NPC1L1) to facilitate cholesterol absorption. Collectively, PKM2-TMEM33 axis modulates cell autonomous lipid metabolism by regulating SREBP activation. PKM2 in small intestine plays critical functions in controlling systemic cholesterol level. Overall, our results underscore unappreciated functions of PKM2 in lipid homeostasis and imply that combining an allosteric activator of PKM2 with NPC1L1 inhibitor represents a therapeutic invention for cancer treatment.
Project description:Atglflox/flox (B6N.129S-Pnpla2tm1Eek/J), S100A8-cre+/- (B6.Cg-Tg(S100A8-cre,-EGFP)1Ilw/J) mice were obtained from The Jackson Laboratory. Atglflox/flox mice were bred to S100A8-cre+/- mice to generate Atglflox/WTS100A8-cre+/- mice, which were backcrossed onto Atglflox/flox mice to generate Atglflox/floxS100A8-cre+/- mice (Atgl neutrophils-specific knock out, Atgl-cKO). Age-matched littermate Atglflox/flox mice were used as wild-type (WT) controls. To compare of the gene expression of the lung-infiltrating neutrophils isolated from Atgl-cKO mice and their WT littermates, AT3-g-csf cells were injected into the fourth mammary fat pads of female WT and Atgl-cKO mice (10-week-old, n = 4/group). The AT3-g-csf cell line is based on a murine breast cancer cell line (AT3) derived from MMTV-PyMT tumors in the C57BL/6 background, and further constructed to overexpress granulocyte-colony stimulating factor (G-CSF) for induction of the host inflammatory condition. At day 10 (pre-metastatic stage), the mice were euthanized and then Ly6G+ neutrophils were isolated from lung by using anti-Ly6G MicroBead Kit (Miltenyi Biotec) following manufacturer’s instructions. The isolated neutrophils were analyzed by flow cytometry and the cells with a > 95% purity were used for the next procedure. Total RNA was isolated from neutrophils using the miRNeasy Mini kit (Qiagen) and the transcriptional profiles of neutrophils were analyzed by RNA sequencing.
Project description:Generation of organ-infiltrating neutrophils occurs in hematopoietic tissues and organs, such as bone marrow and spleen, in response to tumor- and host-derived factors. The de novo expanded neutrophils then egress from hematopoietic sites, circulate through the blood vessels and infiltrate into the organ interstitia and parenchyma. During above trafficking process, neutrophils can undergo phenotypic and functional changes in response to tissue environments. To determine the difference among neutrophils residing in the hematopoietic site—BM, circulating in the blood, and those infiltrating in the metastatic organ, the transcriptional profiles of neutrophils were analyzed by RNA sequencing. 4T1 cells were injected into the fourth mammary fat pads of female syngeneic BALB/cJ mice (8-week-old, n = 3). At day 10 (pre-metastatic stage), the mice were euthanized and then CD45+CD11b+Ly6G<high>Ly6C<med> neutrophils from bone marrow (BM), peripheral blood (PB) and lung were isolated by fluorescence-activated cell sorting. Total RNA was isolated from neutrophils using the miRNeasy Mini kit (Qiagen) and the transcriptional profiles of neutrophils were analyzed by RNA sequencing
Project description:To comprehensively understand how dendritic cells (DCs) are reprogrammed by lung fibroblasts- and their derived COX-2/PGE2, we employed lung fibroblasts isolated from WT or Ptgs2-/- mice, and collect their conditioned medium (CM) to stimulate the ex vivo cultured bone marrow (BM)-derived DCs (BM-DCs), with the PGE2 treatment as a control. After the treatment, BM-DCs were harvested for RNA extraction and the transcriptional profiles were analyzed by RNA sequencing (RNA-seq).
Project description:Purpose: PKM2-mediated metabolic switch to aerobic glycolysis plays a critical role in promoting cell survival and proliferation. However, little is known about the function of intestinal epithelial PKM2 in intestinal homeostasis. Here we investigated whether and how intestinal epithelial PKM2 modulates the morphology and function of the adult intestine in experimental murine colitis. Methods: Colonoscopic biopsies from the Crohn’s disease (CD) and ulcerative colitis (UC) patients (10 each) were analyzed for PKM2 expression. We also generated intestinal epithelial-specific Pkm2 knockout mice and employed them to examine PKM2 function. Mouse intestinal inflammation was induced with dextran sulfate sodium (DSS) in drinking water. Disease phenotypes were investigated by mouse survival, body weight, colon length and analysis of immune cell infiltration in colon, intestinal epithelial cell gene profiling and signal pathway. Results: Intestinal epithelial PKM2 level in UC and CD patients was significantly decreased compared to that from non-inflamed intestinal epithelium. Similar reduction of intestinal epithelial PKM2 was observed in mice with experimental colitis. Supporting the notion that PKM2 serves as a safeguard against colitis, intestinal epithelial-specific Pkm2-deficient (Pkm2-/-) mice displayed a severer intestinal inflammation, companying with shortened colon, disruption of epithelial tight junction, higher permeability, elevation of inflammatory cytokines and immune cell infiltration, compared with wild-type mice. Gene profiling and western blot analysis indicated that cell survival signaling, particularly the Akt/β-catenin pathways, were downregulated in Pkm2-/- mice. Functional assay using mouse primary colonic epithelial cells confirmed that Pkm2 reduction decreased proliferation and migration of epithelial cells, while enhanced expression of Pkm2 was associated with increased transcriptional activity of β-catenin. Moreover, increasing mouse intestinal epithelial Pkm2 expression via delivery of Pkm2-expressing plasmid attenuated DSS-induced experimental colitis. Conclusions: Intestinal epithelial PKM2, through activating Wnt/β-catenin signaling, induces a strong proliferative and migratory response that increases cell survival and wound healing under colitic condition.
Project description:Altered glycolysis is the most fundamental metabolic change associated with the Warburg effect. However, the precise mechanisms are not completely understood. Here we dissect how MNX1-AS1 reinforces the Warburg effect through facilitating the non-glycolytic actions of PKM2 in the nucleus. We found that MNX1-AS1 expression was frequently overexpressed in hepatocellular carcinoma (HCC). In the context of HCC, we show MNX1-AS1 acts as a scaffold to promote interactions between PKM2 and importin α5. Upon EGFR activation, the resulting ternary complex drives the translocation of PKM2 into the nucleus. In consequence, glycolytic pathway components including key mediators of the Warburg effect (LDHA, Glut1 and PDK1) are upregulated. Manipulating MNX1-AS1 elicited robust effects on glycolysis associated with marked changes in HCC growth in vitro and in vivo, indicative of the significant contribution of MNX1-AS1 to tumorigenesis. Moreover, while MNX1-AS1 expression is driven by c-Myc, its actions associated with PKM2 were shown to be downstream and independent of c-Myc. Given the status of MNX1-AS1 as a pan-cancer upregulated lncRNA, this implicitly highlights the potential of targeting MNX1-AS1 to selectively counter the Warburg effect in a range of tumor types.
Project description:Hepatocellular carcinoma (HCC) is one of the leading causes of mortality related to cancer all over the world. The poor prognosis of HCC is mostly due to recurrence and tumor metastasis. In order to better understand the molecular mechanisms of HCC metastasis, we analyzed the proteome of three HCC cell lines with different metastasis potentials by using quantitative proteomics and bioinformatics analysis. As a result, we identified 331 cellular proteins potentially associated to HCC metastasis, and constructed a highly connected protein-protein interaction (PPI) network. Functional annotation of the network uncovered prominent pathways and key roles of these proteins, suggesting that metabolism and cytoskeleton biological progresses are greatly involved with HCC metastasis. Furthermore, integrative network analysis revealed a rich-club organization in the PPI network indicating a hub center of connections, including several well-known cancer related proteins, such as SRC proto-oncogene, non-receptor tyrosine kinase (SRC) and pyruvate kinase M2 (PKM2). Moreover, the differential expressions of two identified proteins, including PKM2 and actin-related protein 2/3 complex subunit 4 (ARPC4), were validated using Western blotting. These two proteins were identified as potential prognostic markers for HCC by using survival rate analysis.
Project description:Vascular endothelial cells (ECs) senescence correlates with the increase of cardiovascular diseases in ageing population. Although ECs rely glycolysis for energy production, little is known about the role of glycolysis in ECs senescence. Here, we report a critical role for glycolysis-derived serine biosynthesis in preventing ECs senescence. During senescence, the expression of serine biosynthetic enzyme PHGDH is significantly reduced due to decreased transcription of the activating transcription factor ATF4, which leads to decreased intracellular serine. PHGDH prevents premature senescence primarily by enhancing the stability and activity of pyruvate kinase M2 (PKM2). Mechanistically, PHGDH interacts with PKM2, which prevents PCAF-catalyzed PKM2 K305 acetylation and subsequent degradation by autophagy. In addition, PHGDH facilitates p300-catalyzed PKM2 K433 acetylation, which promotes PKM2 nuclear translocation and stimulates its activity to phosphorylate H3T11 and regulate the transcription of senescence-associated genes. Vascular endothelium-targeted expression of PHGDH and PKM2 ameliorates the mice ageing phenotype. Our findings reveal that enhancing serine biosynthesis could become a novel therapy to promote healthy ageing.
Project description:Vascular endothelial cells (ECs) senescence correlates with the increase of cardiovascular diseases in ageing population. Although ECs rely glycolysis for energy production, little is known about the role of glycolysis in ECs senescence. Here, we report a critical role for glycolysis-derived serine biosynthesis in preventing ECs senescence. During senescence, the expression of serine biosynthetic enzyme PHGDH is significantly reduced due to decreased transcription of the activating transcription factor ATF4, which leads to decreased intracellular serine. PHGDH prevents premature senescence primarily by enhancing the stability and activity of pyruvate kinase M2 (PKM2). Mechanistically, PHGDH interacts with PKM2, which prevents PCAF-catalyzed PKM2 K305 acetylation and subsequent degradation by autophagy. In addition, PHGDH facilitates p300-catalyzed PKM2 K433 acetylation, which promotes PKM2 nuclear translocation and stimulates its activity to phosphorylate H3T11 and regulate the transcription of senescence-associated genes. Vascular endothelium-targeted expression of PHGDH and PKM2 ameliorates the mice ageing phenotype. Our findings reveal that enhancing serine biosynthesis could become a novel therapy to promote healthy ageing.