A novel bioassay for P-glycoprotein functionality using cytochalasin D

Cytometry. 1998 Mar 1;31(3):187-98. doi: 10.1002/(sici)1097-0320(19980301)31:3<187::aid-cyto6>3.0.co;2-i.


The functional contribution of both P-glycoprotein (P-gp) and the multidrug resistance-associated protein (MRP) to multidrug resistance (MDR) in tumor cells is commonly determined by drug cytotoxicity and/or accumulation/efflux tests. We report on a bioassay developed for the specific detection of functional P-gp levels and the efficacy of related chemosensitizers (CD-P-gp-assay). The assay is based on the flow cytometric measurement of changes in the > or = G2M cell cycle compartment which are due to the induction of polykaryons after exposure of proliferating cells to three defined cytochalasin D (CD) concentrations with and without verapamil. As demonstrated in 13 well-characterized MDR cell models (20 resistant sublines), there is a significant correlation between cytokinesis-blocking CD doses, as well as responsiveness to chemosensitizers and MDR1 gene expression (mRNA and P-gp) allowing discrimination between different levels of P-gp-MDR. CD-P-gp-assay specificity was assessed by testing 23 compounds: 19 known as potent inhibitors of P-gp-MDR, some of them, though to a lesser extent, also of MRP-MDR; 1 inhibiting MRP-but not P-gp-MDR; 3 inactive in both types of MDR. A modulation of CD activity was confined exclusively to both P-gp-expressing cell lines and P-gp chemosensitizers. CD cytoskeletal activity measured by FACS is a specific and sensitive tool with which to detect functional P-gp and related chemosensitizers.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / analysis*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / antagonists & inhibitors
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • ATP-Binding Cassette Transporters / analysis
  • ATP-Binding Cassette Transporters / genetics
  • Animals
  • Antineoplastic Agents / pharmacology
  • CHO Cells
  • Cell Nucleus
  • Cricetinae
  • Cytochalasin D* / toxicity
  • DNA, Neoplasm / analysis
  • Drug Resistance, Multiple
  • Drug Resistance, Neoplasm
  • Flow Cytometry / methods*
  • G2 Phase / drug effects
  • Humans
  • Mitosis
  • Multidrug Resistance-Associated Proteins
  • RNA, Messenger / analysis
  • Sensitivity and Specificity
  • Substrate Specificity
  • Tumor Cells, Cultured
  • Verapamil / pharmacology


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • ATP-Binding Cassette Transporters
  • Antineoplastic Agents
  • DNA, Neoplasm
  • Multidrug Resistance-Associated Proteins
  • RNA, Messenger
  • Cytochalasin D
  • Verapamil