title: Malonate as a ROS product is associated with pyruvate carboxylase activity in acute myeloid leukaemia cells.
abstract: BACKGROUND
  The role of anaplerotic nutrient entry into the Krebs cycle via pyruvate carboxylase has been the subject of increased scrutiny and in particular whether this is dysregulated in cancer. Here, we use a tracer-based NMR analysis involving high-resolution (1)H-(13)C-HSQC spectra to assess site-specific label incorporation into a range of metabolite pools, including malate, aspartate and glutamate in the acute myeloid leukaemia cell line K562. We also determine how this is affected following treatment with the redeployed drug combination of the lipid-regulating drug bezafibrate and medroxyprogesterone (BaP).
  
  
  RESULTS
  Using the tracer-based approach, we assessed the contribution of pyruvate carboxylase (PC) vs. pyruvate dehydrogenase (PDH) activity in the derivation of Krebs cycle intermediates. Our data show that PC activity is indeed high in K562 cells. We also demonstrate a branched entry to the Krebs cycle of K562 cells with one branch running counterclockwise using PC-derived oxaloacetate and the other clockwise from the PDH activity. Finally, we show that the PC activity of K562 cells exclusively fuels the ROS-induced decarboxylation of oxaloacetate to malonate in response to BaP treatment; resulting in further Krebs cycle disruption via depletion of oxaloacetate and malonate-mediated inhibition of succinate dehydrogenase (SDH) resulting in a twofold reduction of fumarate.
  
  
  CONCLUSIONS
  This study extends the interest in the PC activity in solid cancers to include leukaemias and further demonstrates the value of tracer-based NMR approaches in generating a more accurate picture of the flow of carbons and metabolites within the increasingly inappropriately named Krebs cycle. Moreover, our studies indicate that the PC activity in cancer cells can be exploited as an Achilles heel by using treatments, such as BaP, that elevate ROS production.
authors: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, B15 2TT UK.
authors: Michelle A C
authors: MAC
authors: Reed
authors: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, B15 2TT UK.|Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, B15 2TT UK.
authors: Christian
authors: C
authors: Ludwig
authors: School of Biosciences, University of Birmingham, Birmingham, B15 2TT UK.
authors: Christopher M
authors: CM
authors: Bunce
authors: School of Biosciences, University of Birmingham, Birmingham, B15 2TT UK.
authors: Farhat L
authors: FL
authors: Khanim
authors: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, B15 2TT UK.
authors: Ulrich L
authors: UL
authors: Günther
keywords: AML; Cancer metabolism; Malonate; Pyruvate carboxylase