Abstract
One-carbon (1C) units for purine and thymidine synthesis can be generated from serine by cytosolic or mitochondrial folate metabolism. The mitochondrial 1C pathway is consistently overexpressed in cancer. Here, we show that most but not all proliferating mammalian cell lines use the mitochondrial pathway as the default for making 1C units. Clustered regularly interspaced short palindromic repeats (CRISPR)-mediated mitochondrial pathway knockout activates cytosolic 1C-unit production. This reversal in cytosolic flux is triggered by depletion of a single metabolite, 10-formyl-tetrahydrofolate (10-formyl-THF), and enables rapid cell growth in nutrient-replete conditions. Loss of the mitochondrial pathway, however, renders cells dependent on extracellular serine to make 1C units and on extracellular glycine to make glutathione. HCT-116 colon cancer xenografts lacking mitochondrial 1C pathway activity generate the 1C units required for growth by cytosolic serine catabolism. Loss of both pathways precludes xenograft formation. Thus, either mitochondrial or cytosolic 1C metabolism can support tumorigenesis, with the mitochondrial pathway required in nutrient-poor conditions.
Copyright © 2016 Elsevier Inc. All rights reserved.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, Non-U.S. Gov't
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Research Support, N.I.H., Extramural
MeSH terms
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Aminoimidazole Carboxamide / analogs & derivatives
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Aminoimidazole Carboxamide / metabolism
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CRISPR-Cas Systems / genetics
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Carbon / metabolism*
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Cell Compartmentation / drug effects
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Cell Proliferation / drug effects
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Colonic Neoplasms / pathology
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Cytosol / drug effects
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Cytosol / metabolism*
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Folic Acid / metabolism*
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Formates / metabolism
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Gene Knockout Techniques
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Gene Library
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Glycine / pharmacology
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Glycine Hydroxymethyltransferase / metabolism
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HCT116 Cells
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HEK293 Cells
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Humans
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Leucovorin / analogs & derivatives
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Leucovorin / metabolism
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Metabolic Networks and Pathways* / drug effects
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Methylenetetrahydrofolate Dehydrogenase (NADP) / deficiency
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Methylenetetrahydrofolate Dehydrogenase (NADP) / metabolism
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Mitochondria / drug effects
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Mitochondria / metabolism*
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Mutation / genetics
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NADP / metabolism
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Ribonucleotides / metabolism
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Serine / pharmacology
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Xenograft Model Antitumor Assays
Substances
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Formates
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Ribonucleotides
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formic acid
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10-formyltetrahydropteroylglutamic acid
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Aminoimidazole Carboxamide
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Serine
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NADP
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Carbon
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Folic Acid
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Methylenetetrahydrofolate Dehydrogenase (NADP)
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Glycine Hydroxymethyltransferase
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SHMT protein, human
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AICA ribonucleotide
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Leucovorin
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Glycine