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

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 feedforward amplification of cancer survival signaling pathways.

Choline-releasing glycerophosphodiesterase EDI3 drives tumor cell migration and metastasis

“…Both LPA and PA (Fig. 3A) are known to activate the MAPK and PI3K signaling pathways (29)(30)(31), and inhibition of CK in cells was shown to significantly decrease both pAKT and pERK levels (26). However, EDI3 knockdown in MCF-7 cells showed no effect on either pathway (Fig.…”

“…The precise rationale for the high levels of PC in cancer is still not well understood (26). Choline metabolism not only provides membrane phospholipids essential for neoplastic cells, but is essential for the production and activation of a number of lipid second messengers and downstream signaling proteins (27,28).…”

Organ-Specific Cancer Metabolism and Its Potential for Therapy

“…Thus the expression of asparaginase depletes the availability of asparagine because it degrades it to aspartate [194]. The same concept of depletion applies to more recently found inhibitors of fatty acid synthase or choline kinase [198,199], which are in various (pre)clinical phases. Thereby, the concept of depletion goes always along with the risk that either the metabolites that are synthesized can be taken up from the environment or that the pathway is also essential for nontumorigenic cells.…”

Choline Kinase Alpha (CHKα) as a Therapeutic Target in Pancreatic Ductal Adenocarcinoma: Expression, Predictive Value, and Sensitivity to Inhibitors

“…To determine whether overexpression of CHKa results from a high metabolic rate or is required for cell growth, we inhibited the enzyme using MN58b, a specific CHKa inhibitor whose selectivity has recently been shown in vivo by magnetic resonance spectroscopy (34), and by genetic knockdown. CHKa inhibition by both strategies led to decreased cell proliferation, possibly due to reduced PI3K/AKT and MAPK signaling (35).…”