title: Sensitization of ara-C-resistant lymphoma cells by a pronucleotide analogue.
abstract: Adequate intracellular concentrations of ara-CMP, the monophosphorylated derivative of ara-C, are essential for its cytotoxicity. The critical step for ara-CMP formation is intracellular phosphorylation of ara-C by deoxycytidine kinase (dCK). A common nucleoside resistance mechanism is mutation affecting the expression or the specificity of dCK. We describe the ability of a tert-butyl S-acyl-thioethyl (SATE) derivative of ara-CMP (UA911) to circumvent ara-C resistance in a dCK-deficient human follicular lymphoma cell line (RL-G). The RL-G cell line was produced by continuous exposure to gemcitabine and displayed low dCK mRNA and protein expression that conferred resistance both to ara-C (2,250-fold) and to gemcitabine (2,092-fold). RL-G cells were able to take up the UA911 pronucleotide by diffusion and metabolize it to the corresponding ara-CMP and ara-CTP nucleotides, exhibiting a 199-fold reduction in resistance ratios, and a similar cell cycle arrest to the parental RL-7 cells. Exposures to 10, 50 or 100 microM concentrations of UA911 produced 160 +/- 7, 269 +/- 8 and 318 +/- 62 pmol ara-CTP/mg protein in RL-7 cells, and 100 +/- 12, 168 +/- 10 and 217 +/- 39 pmol ara-CTP/mg protein in RL-G cells, respectively. Exposure of RL-G cells to underivatized, radiolabeled ara-C produced no detectable amounts of the active triphosphate metabolites. We conclude that the UA911 pronucleotide is capable of overcoming dCK-mediated resistance. This result can be attributed to the unique cellular metabolism of the SATE pronucleotides giving rise to the intracellular delivery of ara-CMP to dCK-deficient cells.
authors.affiliation: INSERM 590, Laboratoire de Cytologie Analytique, Faculté de Médecine Rockefeller, Lyon, France. fgalma@rockefeller.univ-lyon1.fr
authors.forename: Carlos María
authors.initials: CM
authors.lastname: Galmarini
authors.forename: Marilyn L
authors.initials: ML
authors.lastname: Clarke
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Santos
authors.forename: Lars
authors.initials: L
authors.lastname: Jordheim
authors.forename: Christian
authors.initials: C
authors.lastname: Perigaud
authors.forename: Gilles
authors.initials: G
authors.lastname: Gosselin
authors.forename: Emeline
authors.initials: E
authors.lastname: Cros
authors.forename: John R
authors.initials: JR
authors.lastname: Mackey
authors.forename: Charles
authors.initials: C
authors.lastname: Dumontet
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000378:metabolism / Q000494:pharmacology*; D001085:Arabinofuranosylcytosine Triphosphate / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003561:Cytarabine / Q000494:pharmacology*; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D003842:Deoxycytidine Kinase / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008224:Lymphoma, Follicular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011355:Prodrugs / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D019384:Nucleic Acid Synthesis Inhibitors; D011355:Prodrugs; D003561:Cytarabine; D003841:Deoxycytidine; D001085:Arabinofuranosylcytosine Triphosphate; D003842:Deoxycytidine Kinase; D000093542:Gemcitabine