Covalent Binding of Elliptinium Acetate (NSC 264137) to Nucleic Acids of L1210 Cells in Culture1

I Ilipiiiiiiiin acétate(9-OH-NME; Celiptium) is an antineoplastic agent currently used in the treatment of metastatic breast cancer and is known to intercalate into DNA. Previous studies have demonstrated that this molecule can be oxidized, yielding a reactive electrophilic form, which is able to bind covalently to a nucleophilic biological molecule. In this work, we evidenced a covalent binding of this drug to nucleic acids of LI 210 cells in culture. A high performance liquid chromatography technique allowed us to distinguish between reversible and nonreversible interaction and to determine the binding ratio (i>) of covalently bound elliptinium versus bases of nucleic acids extracted from cells. After an 8-h incubation of 11210 cells with 0.1 pM elliptinium (the dose corresponding to the 50% inhibitory dose), we obtained 2.4 x 10"* and 3.4 x 10~* as the r»for RNA and DNA, respectively. The kinetics of binding was also studied. The dose-response relationship obtained is linear in a concentration range of 0.025 to 0.5 UM 9-OH-NME. Further more, we demonstrated that the covalent binding of 9-OH-NME to DNA is not repaired during a period of 40 h (during this period, the cell population has undergone two doublings). The nonhydroxylated and nonantitumoral derivative of 9-OH-NME, /V2-methylelHpticinium, is 20 to 30 times less active in terms of covalent binding to nucleic acids, compared to the antitumor compound 9-OH-NME. The implication of the covalent binding of 9-OH-NME is discussed with respect to its mechanism of