title: Cyclopentenyl cytosine induces apoptosis and increases cytarabine-induced apoptosis in a T-lymphoblastic leukemic cell-line.
abstract: Cyclopentenyl cytosine (CPEC) is a nucleoside-analogue that decreases the concentrations of cytidine triphosphate (CTP) and deoxycytidine triphosphate (dCTP) in leukemic cells by inhibiting the enzyme CTP synthetase, resulting in a decreased synthesis of RNA and DNA. Low concentrations of dCTP facilitate the phosphorylation of 1-beta-D arabinofuranosyl cytosine (araC) and the incorporation of arabinofuranosyl cytosine triphosphate (araCTP) into DNA. Apoptosis and necrosis were analyzed by flow cytometric detection of fluorescence-labeled Annexin V in a human T-lymphoblastic MOLT-3 cell-line after incubations with CPEC and/or araC. CPEC induced apoptosis and necrosis in a concentration- (50-300 nM) and time-dependent (8-16 h) way. The observed necrosis proved to be secondary to apoptosis as the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk) completely blocked the CPEC-induced apoptosis and necrosis. Coincubation of various concentrations of CPEC and araC for 16h showed a significant additive effect on the occurrence of apoptosis and (secondary) necrosis. In contrast, a preincubation with 37.5 nM of CPEC for 24 h, which by itself caused only minor apoptosis (4%), followed by a coincubation for 16 h with 62.5 nM of araC (7% of apoptotic cells), showed a synergistic effect on the induction of apoptosis (27%, P<0.001). Growth-inhibition experiments with CPEC and araC under various conditions showed an additive effect on the araC-induced growth-inhibition after 48 h. The results indicate that the cytotoxicity of araC can be increased in T-lymphoblasts by CPEC.
authors.affiliation: Laboratory of Genetic Metabolic Diseases, Divisions of Clinical Chemistry and Pediatrics, Academic Medical Centre, University of Amsterdam, Emma Kinderziekenhuis AMC, P.O. Box 22700, 1100 DE, Amsterdam, The Netherlands. a.c.verschuur@amc.uva.nl
authors.forename: A C
authors.initials: AC
authors.lastname: Verschuur
authors.forename: J
authors.initials: J
authors.lastname: Brinkman
authors.forename: A H
authors.initials: AH
authors.lastname: Van Gennip
authors.forename: R
authors.initials: R
authors.lastname: Leen
authors.forename: R J
authors.initials: RJ
authors.lastname: Vet
authors.forename: L M
authors.initials: LM
authors.lastname: Evers
authors.forename: P A
authors.initials: PA
authors.lastname: Voûte
authors.forename: A B
authors.initials: AB
authors.lastname: Van Kuilenburg
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology*; D003562:Cytidine / Q000031:analogs & derivatives / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D015458:Leukemia, T-Cell / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D009336:Necrosis; D014407:Tumor Cells, Cultured / Q000187:drug effects*
chemical_list: D017304:Annexin A5; D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D003561:Cytarabine; D003562:Cytidine; C045911:cyclopentenyl cytosine