Selective inhibition of choline kinase simultaneously attenuates MAPK and PI3K/AKT signaling

A. Yalcin, B. Clem, S. Makoni, A. Clem, K. Nelson, J. Thornburg, D. Siow, A. N. Lane, S. E. Brock, U. Goswami, J. W. Eaton, S. Telang, J. Chesney

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

Choline is an essential anabolic substrate for the synthesis of phospholipids. Choline kinase phosphorylates choline to phosphocholine that serves as a precursor for the production of phosphatidylcholine, the major phospholipid constituent of membranes and substrate for the synthesis of lipid signaling molecules. Nuclear magnetic resonance (NMR)-based metabolomic studies of human tumors have identified a marked increase in the intracellular concentration of phosphocholine relative to normal tissues. We postulated that the observed intracellular pooling of phosphocholine may be required to sustain the production of the pleiotropic lipid second messenger, phosphatidic acid. Phosphatidic acid is generated from the cleavage of phosphatidylcholine by phospholipase D2 and is a key activator of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/AKT survival signaling pathways. In this study we show that the steady-state concentration of phosphocholine is increased by the ectopic expression of oncogenic H-Ras V12 in immortalized human bronchial epithelial cells. We then find that small interfering RNA (siRNA) silencing of choline kinase expression in transformed HeLa cells completely abrogates the high concentration of phosphocholine, which in turn decreases phosphatidylcholine, phosphatidic acid and signaling through the MAPK and PI3K/AKT pathways. This simultaneous reduction in survival signaling markedly decreases the anchorage-independent survival of HeLa cells in soft agar and in athymic mice. Last, we confirm the relative importance of phosphatidic acid for this pro-survival effect as phosphatidic acid supplementation fully restores MAPK signaling and partially rescues HeLa cells from choline kinase inhibition. Taken together, these data indicate that the pooling of phosphocholine in cancer cells may be required to provide a ready supply of phosphatidic acid necessary for the feed-forward amplification of cancer survival signaling pathways.

Original languageEnglish (US)
Pages (from-to)139-149
Number of pages11
JournalOncogene
Volume29
Issue number1
DOIs
StatePublished - Jan 2010

Bibliographical note

Funding Information:
We gratefully acknowledge helpful discussions with Drs Binks Wattenberg, Mary Roth and Otto Grubraw. This work was supported by the James Graham Brown Cancer Center and by the following grants: NIH 1 R01 CA11642801 (JC) and the Kentucky Lung Cancer Research Program (JC).

Keywords

  • Phosphatidic acid
  • Phosphocholine
  • Ras

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