AraC Metabolism in Fresh Leukemic Blasts/ Normal Bone Marrow/ Hematopoetic Stem Cells and its Impact on the Lipid Composition of Leukemic Cells (HL60)
Metabolites of tritium labeled AraC (AraCMP, -CDP, CTP, -CDP-choline) were determined by HPLC analysis. No significant differences in the formation of these metabolites could be found between fresh leukemic blasts, mononuclear cells from normal bone marrow and CD34/ 38 positive hematopoetic stem cells. AraCTP half-life, which has previously been shown to correlate with clinical parameters like CR duration, was longest in leukemic blasts. The intracellular pool of AraCTP precursors (AraCMP, -CDP) was similar and of low abundance (13–20% of AraCTP at all tested AraC concentrations) in all investigated cell types and therefore did not explain the differences in AraCTP half-life.
AraCDP-choline formation seemed to be saturated at higher AraC incubation levels than AraCTP and might therefore have a significance for AraC pharmacodynamics of high dose AraC regimens. Since this metabolite is structurally similar to CDP-choline — a precursor of phospholipid metabolism — the effect of AraC on cellular lipid metabolism of HL60 cells was investigated: AraC induced a significant reduction (30%) in cellular phosphatidylcholine (PC) content. Antagonism of these alterations by lysoPC resulted in almost complete reversal of the AraC induced loss of viability (tested by trypan blue exclusion). The AraC induced loss of viability at high AraC concentrations might be caused partially by the de stabilization of cell membranes, which has also been observed after PC alterations from other causes.
KeywordsLeukemia Choline Sine Sorting Pyrimidine
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