Comparison of intracellular drug retention, DNA damage and cytotoxicity of derivatives of doxorubicin and daunorubicin in a human colon adenocarcinoma cell line (LoVo)

Giorgio Belvedere, Antonio Suarato, Cristina Geroni, Fernando C. Guiliani, Maurizio D'Incalci

Research output: Contribution to journalArticlepeer-review

Abstract

Formation of DNA single strand breaks (SSB) was assayed by alkaline elution in LoVo cells treated with doxorubicin, daunorubicin and six derivatives of these drugs modified either in the chromophore or the sugar. Seven compounds showed a biphasic relationship (initial increase and then a decrease) for the formation of DNA-SSB over the concentration range 0.05-10 μg/ml. At a drug concentration in the range causing an increase of DNA damage very fast repair of DNA-SSB was observed for 4′-deoxydoxorubicin and 4-demethoxydaunorubicin; the kinetics of DNA-SSB investigated after drug removal at a drug concentration reducing DNA-SSB showed a time dependent increase of DNA damage for both drugs although with different patterns. 4′-Deoxydoxorubicin reduced the effect of radiations on the rate of elution of DNA in a way resembling the formation of DNA interstrand cross links (ISC) at concentrations at which DNA-SSB were reduced. DNA-ISC were not produced by chemical reactions occuring during sample processing for alkaline elution and this derivative was not metabolized by LoVo cells. The ic50 of the anthracyclines were on a several log range, though for most of the derivatives the cytotoxicity curve showed a plateau at growth inhibition of about 15-30% at increasing intracellular drug levels. A relationship between DNA damage and cytotoxicity was observed only in a very small range of DNA-SSB. It is likely that the different effects of these anthracyclines on the formation of DNA-SSB depend on a qualitatively different interaction between drug-DNA and topoisomerase II when the drug concentration is raised.

Original languageEnglish
Pages (from-to)3713-3721
Number of pages9
JournalBiochemical Pharmacology
Volume38
Issue number21
DOIs
Publication statusPublished - Nov 1 1989

ASJC Scopus subject areas

  • Pharmacology

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