title: Modulation of the cytotoxicity of the antitumor antibiotic peplomycin by membrane-interacting drugs and by increased levels of calcium ions.
abstract: The cytotoxic effect of peplomycin (PEP), a new derivative of bleomycin glycopeptide antibiotics, toward HeLa cells and mouse FM3A cells was markedly enhanced by combination of PEP with non-toxic doses of the membrane-interacting drugs verapamil (0.1-0.2mM) and dibucaine (0.15-0.25mM), or with CaCl2 (10-16 mM). Treatment with verapamil or CaCl2 following PEP treatment also effectively enhanced the cytotoxic effect of PEP, suggesting an interaction with PEP-induced damage. Cellular uptake of PEP did not increase in dibucaine-treated cells, suggesting no correlation between membrane permeability to PEP and enhanced cytotoxicity. Increased Ca2+ did not enhance the cytotoxic effects of adriamycin, mitomycin C, cis-diamminedichloroplatinum (II), vinblastine or macromomycin, thus suggesting a unique interaction with PEP. The enhancing action of verapamil and Ca2+ was greatly promoted by 41 degrees hyperthermia, although 41 degrees alone scarcely enhanced PEP cytotoxicity. Cytochalasin B and alpha-tocopherol, but not cytochalasin D, reversed the enhanced cytotoxicity produced by PEP and verapamil or dibucaine, but did not reverse the enhanced cytotoxicity by PEP combined with increased Ca2+. The enhancing action of Ca2+ was, however, antagonized by ruthenium red and lanthanum chloride, which are potent inhibitors of Ca2+ uptake by cells, or by magnesium chloride. Verapamil and increased Ca2+ promoted the decomposition of the DNA-membrane complex induced by PEP in HeLa cells, and also impaired the regeneration of the decomposed DNA complex.
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001761:Bleomycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003992:Dibucaine / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D008325:Mammary Neoplasms, Experimental / Q000473:pathology; D051379:Mice; D017663:Peplomycin; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000903:Antibiotics, Antineoplastic; D007473:Ion Channels; D001761:Bleomycin; D017663:Peplomycin; D014700:Verapamil; D003992:Dibucaine; D002118:Calcium