title: Cellular pharmacology of multi- and duplex drugs consisting of ethynylcytidine and 5-fluoro-2'-deoxyuridine.
abstract: Prodrugs can have the advantage over parent drugs in increased activation and cellular uptake. The multidrug ETC-L-FdUrd and the duplex drug ETC-FdUrd are composed of two different monophosphate-nucleosides, 5-fluoro-2'deoxyuridine (FdUrd) and ethynylcytidine (ETC), coupled via a glycerolipid or phosphodiester, respectively. The aim of the study was to determine cytotoxicity levels and mode of drug cleavage. Moreover, we determined whether a liposomal formulation of ETC-L-FdUrd would improve cytotoxic activity and/or cleavage. Drug effects/cleavage were studied with standard radioactivity assays, HPLC and LC-MS/MS in FM3A/0 mammary cancer cells and their FdUrd resistant variants FM3A/TK(-). ETC-FdUrd was active (IC(50) of 2.2 and 79 nM) in FM3A/0 and TK(-) cells, respectively. ETC-L-FdUrd was less active (IC(50): 7 nM in FM3A/0 vs 4500 nM in FM3A/TK(-)). Although the liposomal formulation was less active than ETC-L-FdUrd in FM3A/0 cells (IC(50):19.3 nM), resistance due to thymidine kinase (TK) deficiency was greatly reduced. The prodrugs inhibited thymidylate synthase (TS) in FM3A/0 cells (80-90%), but to a lower extent in FM3A/TK(-) (10-50%). FdUMP was hardly detected in FM3A/TK(-) cells. Inhibition of the transporters and nucleotidases/phosphatases resulted in a reduction of cytotoxicity of ETC-FdUrd, indicating that this drug was cleaved outside the cells to the monophosphates, which was verified by the presence of FdUrd and ETC in the medium. ETC-L-FdUrd and the liposomal formulation were neither affected by transporter nor nucleotidase/phosphatase inhibition, indicating circumvention of active transporters. In vivo, ETC-FdUrd and ETC-L-FdURd were orally active. ETC nucleotides accumulated in both tumor and liver tissues. These formulations seem to be effective when a lipophilic linker is used combined with a liposomal formulation.
authors: Department Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands.
authors: Irene V
authors: IV
authors: Bijnsdorp
authors: Reto A
authors: RA
authors: Schwendener
authors: Herbert
authors: H
authors: Schott
authors: Iduna
authors: I
authors: Fichtner
authors: Kees
authors: K
authors: Smid
authors: Adrie C
authors: AC
authors: Laan
authors: Sarah
authors: S
authors: Schott
authors: Nienke
authors: N
authors: Losekoot
authors: Richard J
authors: RJ
authors: Honeywell
authors: Godefridus J
authors: GJ
authors: Peters
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003562:Cytidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005467:Floxuridine / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D005468:Fluorodeoxyuridylate / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D008081:Liposomes / Q000378:metabolism; D051379:Mice; D033703:Nucleoside Transport Proteins / Q000378:metabolism; D009705:Nucleosides / Q000378:metabolism; D013940:Thymidylate Synthase / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: C103084:1-(3-C-ethynylribopentofuranosyl)cytosine; D008081:Liposomes; D033703:Nucleoside Transport Proteins; D009705:Nucleosides; D005467:Floxuridine; D005468:Fluorodeoxyuridylate; D003562:Cytidine; D013940:Thymidylate Synthase