Potentiation of anticancer-drug cytotoxicity by multidrug-resistance chemosensitizers involves alterations in membrane fluidity leading to increased membrane permeability

Eur J Biochem. 1995 Mar 15;228(3):1020-9. doi: 10.1111/j.1432-1033.1995.tb20352.x.


We are studying the mechanism underlying chemosensitization of anticancer-drug cytotoxicity in wild-type and multidrug-resistant (MDR) mammalian cells. We show here that the chemosensitizers, reserpine and verapamil, display a dramatic potentiation of taxol, anthracycline and Vinca alkaloids cytotoxicity in P-glycoprotein-(P-gp)-deficient hamster and human nasopharyngeal carcinoma cells. We have therefore utilized this phenomenon to probe for the putative P-gp-independent component of cytotoxicity chemosensitization. These chemosensitizers yielded a marked increase in the accumulation of taxol in parental hamster and human carcinoma cells that are devoid of P-gp. These chemosensitizers and non-ionic detergents brought about a pronounced increase in the accumulation of structurally and mechanistically diverse lipophilic chromophores in parental and MDR hamster cells. Furthermore, non-toxic concentrations of these non-ionic detergents yielded a marked potentiation of taxol cytotoxicity in parental cells. These findings were consistent with a chemosensitizer-mediated, P-gp-independent increase in membrane permeability. Thus, several aspects of chemosensitizers' interaction with lipid bilayers and biomembranes were studied. In this respect, like various mild detergents, chemosensitizers induced a dose-dependent leakage of carboxyfluorescein encapsulated in liposomes. Like specialized membrane fluidizers, various chemosensitizers induced a dose-dependent membrane fluidization (and sometimes rigidification) in both liposomes and various wild-type and MDR animal and human cells, as revealed by diphenylhexatriene fluorescence polarization. Furthermore, a favorable correlation was observed between the ability of chemosensitizers to permeabilize lipid bilayers and their capacity to potentiate anticancer-drug cytotoxicity. Thus, we propose that chemosensitizer-mediated changes in the physical properties of biomembranes, including altered fluidity and increased permeability, may be important factors in achieving potentiation of anticancer-drug cytotoxicity in wild-type and MDR mammalian cells. This study offers a basis for the chemosensitizer-mediated potentiation of drug toxicity to healthy tissues, thus emphasizing the importance of a prior evaluation of the potential untoward toxicity when simultaneously using MDR chemosensitizers and cytotoxic agents in the clinic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Animals
  • Antineoplastic Agents / pharmacology*
  • CHO Cells
  • Cell Membrane Permeability / drug effects*
  • Cricetinae
  • Drug Resistance, Multiple*
  • Drug Synergism
  • Humans
  • Membrane Fluidity / drug effects*
  • Reserpine / pharmacology*
  • Tumor Cells, Cultured
  • Verapamil / pharmacology*


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents
  • Reserpine
  • Verapamil