title: Cyclopentenyl cytosine primes SK-N-BE(2)c neuroblastoma cells for cytarabine toxicity.
abstract: CPEC is a potent inhibitor of CTP synthetase and causes depletion of CTP and dCTP pools. AraC is an analog of dCyd and a chemotherapeutic agent. Here, we demonstrate that, upon incubation with CPEC, both the anabolism and cytostatic effect of AraC in SK-N-BE(2)c neuroblastoma cells were increased. Cotreatment of CPEC (50-250 nM) and AraC (37.5-500 nM) decreased the 4-day ED(50) value for AraC 2- to 8-fold in the SK-N-BE(2)c cell line, while pretreatment with CPEC followed by incubation with AraC alone decreased the 4-day ED(50) value for AraC 1- to 19-fold. Preincubation of SK-N-BE(2)c cells with 100 nM CPEC followed by incubation with 500 nM [(3)H]AraC increased the total amount of AraC nucleotides and incorporation of [(3)H]AraC into DNA by 392% and 337%, respectively, compared to non-CPEC-treated cells. When 20 nM [(3)H]AraC was used, the maximum incorporation of [(3)H]AraC into DNA was 1,378% compared to non-CPEC-treated cells. Incorporation of AraC into DNA correlated well with the accumulation of cells in S phase of the cell cycle caused by CPEC. DNA synthesis was almost completely inhibited (>91%) when 100 nM CPEC and 500 nM AraC were combined. CPEC alone and the combination of CPEC and AraC increased caspase-3 activity 3-fold, indicating induction of apoptosis in SK-N-BE(2)c cells. In contrast, AraC alone did not induce caspase-3 activity. Our results demonstrate that low concentrations of CPEC profoundly increase the cytostatic properties of AraC toward SK-N-BE(2)c human neuroblastoma cells.
authors.affiliation: Department of Clinical Chemistry, Emma Children's Hospital, Academic Medical Center, University of Amsterdam, the Netherlands.
authors.forename: Jörgen
authors.initials: J
authors.lastname: Bierau
authors.forename: Albert H
authors.initials: AH
authors.lastname: Van Gennip
authors.forename: René
authors.initials: R
authors.lastname: Leen
authors.forename: Jozien
authors.initials: J
authors.lastname: Helleman
authors.forename: Huib N
authors.initials: HN
authors.lastname: Caron
authors.forename: André B P
authors.initials: AB
authors.lastname: Van Kuilenburg
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D019731:Carbon-Nitrogen Ligases / Q000037:antagonists & inhibitors; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003561:Cytarabine / Q000633:toxicity*; D003562:Cytidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004273:DNA, Neoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects*
chemical_list: D000964:Antimetabolites, Antineoplastic; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D003561:Cytarabine; D003562:Cytidine; C045911:cyclopentenyl cytosine; D019731:Carbon-Nitrogen Ligases; C019951:CTP synthetase