title: Biochemical and molecular effects of UCN-01 in combination with 5-fluorodeoxyuridine in A431 human epidermoid cancer cells.
abstract: Concurrent and pre-exposure of A431 human epidermoid cancer cells to UCN-01, an investigational anticancer drug, with 5-fluoro--2'-deoxyuridine (FdUrd), which targets thymidylate synthase, produced more than additive cytotoxicty. A 24-h exposure to 10 nM FdUrd led to inhibition of TS, a 2.5-fold increase in total thymidylate synthase protein content, profound dTTP depletion and a 6.3-fold increase in the ratio of dATP to dTTP, but did not cause single-strand breaks in DNA. However, FdUrd enhanced UCN-01-associated DNA strand breaks. Concurrent thymidine exposure led to repletion of dTTP pools, and cytoprotection against FdUrd alone and with UCN-01. UCN-01 arrested cells in G1, decreased the percentage of FdUrd-treated cells in S phase and reduced FdUrd-DNA incorporation, suggesting the latter was not important for cytotoxicity. Delayed induction of high molecular mass DNA fragmentation and poly(ADP-ribose) polymerase cleavage was observed with the combination of UCN-01 and FdUrd. These findings suggest that while FdUrd-mediated deoxynucleotide imbalance alone was insufficient to induce apoptosis in this p53-mutant cell line, it magnified UCN-01's effects, most likely by interfering with DNA repair. The clinical evaluation of UCN-01 combined with 5-fluoropyrimidines may be of interest.
authors: Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute-Navy Medical Oncology, National Naval Medical Center, Bethesda, MD 20889-5105, USA. gremj@mail.nih.gov
authors: Jean L
authors: JL
authors: Grem
authors: Kathleen D
authors: KD
authors: Danenberg
authors: Vivian
authors: V
authors: Kao
authors: Peter V
authors: PV
authors: Danenberg
authors: Diana
authors: D
authors: Nguyen
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D004249:DNA Damage / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism; D003854:Deoxyribonucleotides / Q000378:metabolism; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005467:Floxuridine / Q000494:pharmacology*; D016158:Genes, p53; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D019311:Staurosporine / Q000031:analogs & derivatives; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000201:enzymology
chemical_list: D000470:Alkaloids; D000964:Antimetabolites, Antineoplastic; D004273:DNA, Neoplasm; D003854:Deoxyribonucleotides; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D005467:Floxuridine; C054852:7-hydroxystaurosporine; D013940:Thymidylate Synthase; D019311:Staurosporine