A non-catalytic role of choline kinase alpha is important in promoting cancer cell survival

Abstract

Choline kinase alpha (ChoKα) is regarded as an attractive cancer target. The enzyme catalyses the formation of phosphocholine (PCho), an important precursor in the generation of phospholipids essential for cell growth. ChoKα has oncogenic properties and is critical for the survival of cancer cells. Overexpression of the ChoKα protein can transform noncancer cells into cells with a cancerous phenotype, and depletion of the ChoKα protein can result in cancer cell death. However, the mechanisms underlying the tumourigenic properties of ChoKα are not fully understood. ChoKα was recently demonstrated to associate with other oncogenic proteins, raising the possibility that a non-catalytic protein scaffolding function drives the tumourigenic properties of ChoKα rather than a catalytic function. In order to differentiate these two roles, we compared the impact on cancer cell survival using two tools specific for ChoKα: (1) small interfering RNA (siRNA) to knockdown the ChoKα protein levels; and (2) compound V-11-0711, a novel potent and selective ChoKα inhibitor (ChoKα IC50 20 nℳ), to impede the catalytic activity. Both treatments targeted the endogenous ChoKα protein in HeLa cells, as demonstrated by a substantial reduction in the PCho levels. siRNA knockdown of the ChoKα protein in HeLa cells resulted in significant cell death through apoptosis. In contrast, compound V-11-0711 caused a reversible growth arrest. This suggests that inhibition of ChoKα catalytic activity alone is not sufficient to kill cancer cells, and leads us to conclude that there is a role for the ChoKα protein in promoting cancer cell survival that is independent of its catalytic activity.

Overexpression of CHKA contributes to tumor progression and metastasis and predicts poor prognosis in colorectal carcinoma

“…Their discovery not only offers one explanation for the effect of CHKA knockdown in prostate cancer, but also supports the importance of a non-catalytic scaffolding function of CHKA protein, rather than or in addition to its catalytic activity, in promoting cancer cell survival, which has also been demonstrated recently in other epithelial malignancies [53, 56]. Although in this study we did not observe a significant effect of CHKA knockdown on EGFR distribution or c-Src levels in HCT116 cells (data no shown), it would be interesting to examine whether CHKA could interact with EGFR in CRC, and if so whether this interaction is also dependent on c-Src activity.…”

Preclinical Characterization of RSM-932A, a Novel Anticancer Drug Targeting the Human Choline Kinase Alpha, an Enzyme Involved in Increased Lipid Metabolism of Cancer Cells

“…Thus, inhibition of ChoKa expression or its enzymatic activity is related to inhibition of mitogenic signals such as the PI3K/Akt and MAPK pathway (27,45,46), and ChoKa has been found to form a functional complex with EGFR (47). Furthermore, the interaction of different inhibitors with the ChoKa enzyme follows diverse mechanisms including both choline competitive and noncompetitive inhibition (30,33) and as a consequence, may induce differential in vivo outcomes as recently proposed (48).…”

The novel choline kinase inhibitor ICL-CCIC-0019 reprograms cellular metabolism and inhibits cancer cell growth

“…To date, attention in the field of cancer has focused on the requirement of choline together with channeling of fatty acids into PC synthesis to support the increased need for membrane synthesis; however, this mechanism alone does not explain the effects of chemical inhibitors. CHKA chemical inhibitors developed to date phenocopy CHKA knockdown showing a decrease in PCho levels, however, only minimal cytotoxicity is seen with ATP-site binding, relative to choline-site or mixed ATP-site/choline-site inhibitors, leading to the suggestion that a CHKA-independent or non-catalytic role for CHKA is important for promoting cell survival [37]. We report the pharmacology of a new CHKA inhibitor, and demonstrate that CHKA chemical inhibition can induce profound ER stress response and inhibit mitochondrial respiration as additional potential mechanisms for reduced survival.…”

“…It should be noted, however, that using a novel CHKA inhibitor, V-11–0711 [37], two independent laboratories have shown that drug-induced reductions of steady state PCho occurring after 24 h in HeLa and MDA-MB-231 were not sufficient to decrease cell viability, compared to CHKA RNAi [37, 38]; cell viability was lost only in SUM149 cells at similar drug concentrations. The groups infer that it is the depletion of CHKA protein - acting through non-catalytic functions [39] - but not inhibition of CHKA catalytic activity that is able to decrease cell survival.…”