Choline kinase activity in cancer and normal human mammary epithelial cells.

G. Eliyahu, E. Rushkin, Prof H. Degani

Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.

Aim: In many human cancers and transformed cell lines the intracellular concentration of phosphocholine (PCho) is well above the normal level. Investigations in our laboratory using magnetic resonance spectroscopy (MRS) revealed a ten fold increase in PCho level in human breast cancer, but only a two fold increase in the rate of choline transport as compared to human mammary epithelial cells (HMEC). In here we present studies aimed at searching for mechanism(s) that are involve in the specific augmentation of PCho level in cancer cells. Method: The enzyme choline kinase catalyzes the phosphorylation of choline to form PCho. The activity of choline kinase was determined using a radioactive assay (C14-choline) in crude extracts from four human breast cancer cell lines: MCF-7, T47D, MDA-MB-231, and ZR-75-1 as well as from HMEC. Excess radioactive choline was washed out by phase-separation with tetraphenylboron in butyronitrile. Results and conclusion: The final activities of choline kinase (in cpm / µg protein * min) for all cell types were as follow: HMEC: 1.152+/-0.19; MDA-MB-231: 2.12+/-0.31; MCF-7; 2.8+/-0.42; T47D: 2.8+/-0.23; and ZR-75-1: 5.53+/-0.73. The results clearly show stimulation of choline kinase activity (2-4 fold) in malignant human mammary epithelial cells and indicate a major role for this enzyme in increasing PCho in cancer. Further studies to elucidate the regulation of this stimulation and its association with malignant transformation are now underway.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Molecular Pathology.