title: Effect of N-(phosphonacetyl)-L-aspartate on 5-azacytidine metabolism in P388 and L1210 cells.
abstract: The effect of N-phosphonacetyl-L-aspartate (PALA) pretreatment on the metabolism and cytotoxicity of 5-azacytidine (5-aza-Cyd) was studied in two murine leukemic cell lines. Exposure of P388 and L1210 cells to 3 mM PALA for 3 hr before adding 5-aza-Cyd at 75 microM was accompanied by a two-fold increment in acid-soluble and 3-fold increment in acid-insoluble incorporation of 5-aza-Cyd in both cell lines. RNA incorporation of 5-aza-Cyd increased from 97.5 +/- 3.4 pmol 5-aza-Cyd per microgram D-ribose in control cells to 299.2 +/- 4.2 pmol 5-aza-Cyd per microgram D-ribose in PALA-treated cells; a smaller increment in DNA incorporation of 5-aza-Cyd was also noted. Sequential treatment of cells with PALA and 5-aza-Cyd was associated with a 40% reduction in protein synthesis compared to only a 2 and 8% reduction, respectively, produced by the drugs given alone. Sequential administration of PALA and 5-aza-Cyd resulted in greater than additive cytotoxicity as measured by both growth inhibition and in vitro soft-agar cloning assays. Exposure of both cell lines to 3 mM PALA for 3 hr produced 50 and 65% reductions in intracellular levels of cytidine triphosphate and uridine triphosphate; intracellular accumulation of 5-azacytidine triphosphate, the lethal metabolite of 5-aza-Cyd, increased from 43.4 +/- 2.1 pmol/10(6) cells to 92.4 +/- 3.3 pmol/10(6) cells in PALA-treated cells. PALA was able to augment the metabolism and cytotoxicity of 5-aza-Cyd in a uridine-cytidine kinase-mutant 5-aza-Cyd-resistant L5178Y subline. This sequential drug combination has a rational biochemical basis and may offer significant advantages over either drug when administered alone, especially in cells which are resistant to 5-aza-Cyd.
mesh_terms: D000818:Animals; D001221:Aspartate Carbamoyltransferase / Q000037:antagonists & inhibitors*; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D001374:Azacitidine / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D003562:Cytidine / Q000378:metabolism; D004273:DNA, Neoplasm / Q000096:biosynthesis; D007939:Leukemia L1210 / Q000378:metabolism; D007942:Leukemia, Experimental / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000096:biosynthesis; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D012334:RNA, Neoplasm / Q000096:biosynthesis; D014529:Uridine / Q000378:metabolism
chemical_list: D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D009943:Organophosphorus Compounds; D012334:RNA, Neoplasm; D001224:Aspartic Acid; D003562:Cytidine; C013195:sparfosic acid; D001221:Aspartate Carbamoyltransferase; D001374:Azacitidine; D010746:Phosphonoacetic Acid; D014529:Uridine