Choline kinase inhibitors as a novel approach for antiproliferative drug design

Abstract

Recent progress in deciphering the molecular basis of carcinogenesis is of utmost importance to the development of new anticancer strategies. To this end, it is essential to understand the regulation of both normal cell proliferation and its alterations in cancer cells. We have previously demonstrated that in ras-transformed cells there is an increased level of phosphorylcholine (PCho) resulting from a constitutive activation on choiline kinase (ChoK). The importance of ChoK for the regulation of cell proliferation has also been proposed since an inhibitor for this enzyme, hemicholinium-3 (HC-3), drastically reduces entry into the S phase after stimulation with growth factors. Here we report the synthesis of several new compounds which are highly speci®c inhibitors for ChoK, with up to 1000-fold or 600-fold increased inhibitory activity, compared to HC-3 under ex vivo or in vitro conditions respectively. These novel compounds also drastically reduce entry into the S phase after stimulation with speci®c growth factors. A more profound inhibition of cell proliferation was observed in ras-, src-and mos-transformed cells in the presence of ChoK inhibitors, compared to their parental, untransformed NIH3T3 cells. By contrast, this e ect was not observed in fos-transformed cells. While ras, src and mos transformation is associated with elevated levels of ChoK activity, fos-induced transformation does not a ect ChoK activity. The inhibitory e ect on proliferation of the new compounds correlates with their ability to inhibit the production of phosphorylcholine in whole cells, a proposed novel second messenger for cell proliferation. These results strongly support a critical role of choline kinase in the regulation of cell growth and makes this enzyme a novel target for the design of new antiproliferative and anticancer drugs.

Modulation of phospholipase D by hexadecylphosphorylcholine: a putative novel mechanism for its antitumoral activity

“…In a attempt to clarify this issue, we have analysed the e ect of HePC on the basal and phorbol-ester stimulated PLD activity and on ChoK, two enzymes involved in PC metabolism recently reported to play a role in cellular transformation (Herna ndez-Alcoceba et al, 1997;Lu et al, 2000). The results obtained indicate the existence of PKC-dependent or independent mechanisms for PLD activation, depending on cell type, and a general loss of response of PLD activation after chronic treatment with HePC.…”

“…Thus, this drug with a phospholipid-related structure a ects one of the critical enzymes involved in the PLD/ ChoK pathway but has no e ect on the other. ChoK inhibitors that interfere with ChoK function but have no e ect on PLD, also show antiproliferative and antitumoral actions (Herna ndez-Alcoceba et al, 1997. Alterations in the balance of the pathways regulating the generation of mitogenic (PCho) and structural signals (PC) may be critical for the integrity of the cells (Lacal and Carnero, 1994;Lacal, 1997).…”

Inhibition of choline kinase as a specific cytotoxic strategy in oncogene-transformed cells

“…We have previously demonstrated that inhibition of ChoK by hemicholinium-3 interferes with the mitogenic action of growth factors such as platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF) in mouse fibroblasts (Cuadrado et al, 1993;Jime´nez et al, 1995;Herna´ndez-Alcoceba et al, 1997). However, there is evidence that HC-3 may not be specific for ChoK interfering with other signalling pathways (Lacal, 2001).…”

“…The intracellular levels of PCho are increased not only in stably transfected cells (Lacal et al, 1987;Macara, 1989;Herna´ndez-Alcoceba et al, 1997) but also in transient expression systems (Lacal, 1990;Ratmant and Kent, 1995). PC degradation and synthesis are activated in ras-transformed (Yang et al, 1990a, b;Oikawa et al, 1991) and src-transformed cells (Yang et al, 1990b), suggesting a role for the Kennedy pathway in cell division.…”

“…Furthermore, the relevance of PCho production is supported by additional experiments. Thus, the exogenous addition of PCho to the culture medium induces the G1-S transition in murine fibroblasts (Cuadrado et al, 1993;Jime´nez et al, 1995;Herna´ndez-Alcoceba et al, 1997), and cooperates with other mitogens and related compounds for mitogenic activity (Kiss and Chung, 1996;Chung et al, 1997Chung et al, , 2000.…”