Inhibition of choline kinase renders a highly selective cytotoxic effect in tumour cells through a mitochondrial independent mechanism.
Tumour cells are frequently altered in their phospholipid metabolism. Choline kinase (ChoK, E.C. 2.7.1.32) activity, the first enzyme involved in the synthesis of phosphatidylcholine, is increased in a large number of human tumours and tumour-derived cell lines. We have previously reported that MN58b, a specific inhibitor of ChoK, has anti-tumoral activity. Here we show the high specificity of MN58b as a cytotoxic drug towards tumour cells, and explore further the basis of its mechanism of action in order to provide a rational understanding for its antitumoral activity. A dramatic difference in the response to the treatment of primary, normal and non-tumorigenic human cells when compared to tumour-derived cell lines was observed. In normal cells, blockage of de novo PCho synthesis by MN58b results in a reversible cell cycle arrest at G0/G1 phase. In contrast, ChoK inhibition in tumour cells promotes the induction of apoptosis. This effect depends on the cell cycle phase, being G1 the critical phase. Regarding the mechanism of apoptosis engagement, a loss of mitochondrial potential was observed 10-20 min after cytochrome c release, but caspase 3 activation preceded the loss of mitochondrial potential, indicating that activation of caspase 3 is independent of cytochrome c release. Our results are consistent with a non-intrinsic process as the mechanism underlying the induction of apoptosis by ChoK inhibition in tumoral cells.
Rodríguez-González
Agustín
A
Translational Oncology Unit, Department of Molecular and Cellular Biology of Cancer, Instituto de Investigaciones Biomédicas, CSIC, Arturo Duperier 4, 28029 Madrid, Spain.
Ramírez de Molina
Ana
A
Bañez-Coronel
Mónica
M
Megias
Diego
D
Lacal
Juan Carlos
JC
D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle; D002797:Choline Kinase / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000473:pathology*; D009369:Neoplasms / Q000473:pathology*; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D002797:Choline Kinase