title: Activity of cyclosporin A and a non-immunosuppressive cyclosporin against multidrug resistant leukemic cell lines.
abstract: Cyclosporin A (CsA) has been shown to increase the sensitivity of multidrug resistant (MDR) cells to chemotherapeutic agents. Although the concentration of drug required to produce this effect is clinically achievable, the use of this drug would be hampered by significant immunosuppression. We report a comparison of the effects of 11-methyl-leucine cyclosporin (11-met-leu CsA), a non-immunosuppressive homolog to the parent drug, on MDR cell lines. Both cyclosporins sensitized resistant cell lines to doxorubicin, including P388 murine leukemia and GM 3639 human T-cell leukemia. The action of the cyclosporins was more pronounced with resistant cells than with sensitive ones. 11-Met-leu CsA was less potent than, but equally effective as, the parent drug. Both agents increased the intracellular accumulation and retention of doxorubicin in MDR cells. The sensitization caused by the cyclosporins was independent of their effects on cyclophilin, calmodulin, and protein kinase C. Furthermore, there were no differences in the binding of labelled CsA to MDR cells compared to the binding to sensitive cells, suggesting that P-glycoprotein was also not the molecular site of action. These studies demonstrate that a non-immunosuppressive cyclosporin can modulate multidrug resistance and suggest its further evaluation for use in clinical trials.
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, CT 06510.
authors.forename: W N
authors.initials: WN
authors.lastname: Hait
authors.forename: J M
authors.initials: JM
authors.lastname: Stein
authors.forename: A J
authors.initials: AJ
authors.lastname: Koletsky
authors.forename: M W
authors.initials: MW
authors.lastname: Harding
authors.forename: R E
authors.initials: RE
authors.lastname: Handschumacher
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003524:Cyclosporins / Q000378:metabolism / Q000494:pharmacology*; D004317:Doxorubicin / Q000378:metabolism / Q000494:pharmacology*; D004351:Drug Resistance; D006801:Humans; D007165:Immunosuppression Therapy; D007700:Kinetics; D007941:Leukemia P388; D051379:Mice; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: C065029:11-methylleucine cyclosporin A; D003524:Cyclosporins; D004317:Doxorubicin