In vitro and in vivo effects of clinically important camptothecin analogues on multidrug-resistant cells

Oncol Res. 1993;5(12):467-74.


The cytotoxic alkaloid camptothecin (CPT) and several of its analogues, including the clinically relevant topotecan (TPT), irinotecan (CPT-11), and 9-aminocamptothecin, were evaluated for differential cytotoxic effect and DNA damage induction in multidrug-sensitive (AuxB1) and multidrug-resistant (MDR) (CHRC5) Chinese hamster ovary cells. CPT, 10-hydroxycamptothecin, and 10,11-methylenedioxycamptothecin produced equivalent amounts of cell growth inhibition and/or DNA single-strand breakage in the two cell lines. TPT, SN-38 (the active metabolite of CPT-11), and 9-aminocamptothecin were 12-, 9-, and 10-fold, respectively, less toxic to the MDR than to the wild-type cells. These findings are consistent with differences in yields of DNA single-strand breaks produced in AuxB1 and CHRC5 cells by 2-hr incubations with the various compounds. In both assays, the resistance ratios of the topoisomerase I inhibitors were approximately one-tenth those of known MDR drugs such as vinblastine or amsacrine. Thus, cultured cells that overexpress P-glycoprotein have the potential to develop some level of cross-resistance to all three topoisomerase I inhibitors currently in the clinic. The chemical basis for cross-resistance of cultured MDR cell lines to certain CPT analogues is not yet understood, but is likely more complex than positive charge alone. TPT had a reasonable therapeutic effect on B6D2F1 female mice implanted with MDR sublines of P388 leukemia, compared with its effect on mice implanted with wild-type P388 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • CHO Cells
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacology*
  • Cell Survival / drug effects
  • Cricetinae
  • DNA Damage
  • Drug Resistance
  • Female
  • Irinotecan
  • Leukemia P388 / drug therapy
  • Mice
  • Topotecan


  • Antineoplastic Agents
  • 9-aminocamptothecin
  • Irinotecan
  • Topotecan
  • Camptothecin