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Updated: Aug 15, 2026

Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein
10:43

Expression, Detergent Solubilization, and Purification of a Membrane Transporter, the MexB Multidrug Resistance Protein

Published on: December 3, 2010

DiOC2(3) is not a substrate for multidrug resistance protein (MRP)-mediated drug efflux

H Minderman1, U Vanhoefer, K Toth

  • 1Department of Experimental Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.

Cytometry
|September 1, 1996
PubMed

Insights

Doxorubicin and Rhodamine-123 can evaluate Multidrug Resistance Protein (MRP) function by measuring cellular drug retention. DiOC2(3) is not suitable for assessing MRP-mediated drug efflux.

Area of Science:

  • Molecular Biology
  • Pharmacology
  • Cell Biology

Background:

  • Multidrug resistance (MDR) is a significant challenge in cancer therapy, often mediated by efflux pumps like P-glycoprotein (Pgp) and Multidrug Resistance Protein (MRP).
  • Flow cytometry is a common method to assess Pgp-mediated MDR by measuring the cellular retention of fluorescent substrates.

Purpose of the Study:

  • To investigate whether fluorescent agents used for evaluating Pgp function can also be utilized to assess MRP function.
  • To determine the suitability of doxorubicin (Dox), Rhodamine-123 (Rh-123), and DiOC2(3) for evaluating MRP-mediated drug efflux.

Main Methods:

  • Cellular retention assays were performed using flow cytometry on MRP-expressing cell lines (HL60/Adr, HT1080/DR4) and a Pgp-expressing cell line (A2780/Dx5).
  • Retention of Dox, Rh-123, and DiOC2(3) was measured after varying reincubation periods in drug-free medium.
  • The effect of a Multidrug Resistance modulator, PAK-104P, on drug efflux and cellular sensitivity was evaluated.

Main Results:

  • While Pgp overexpression inversely correlated with retention of all three agents, MRP-expressing cells showed no significant difference in retention at 1-hour reincubation.
  • Extended reincubation (4-24 hours) revealed efflux of Dox and Rh-123 in MRP-expressing cells, but DiOC2(3) efflux was not detected.
  • PAK-104P treatment negated drug efflux in both Pgp and MRP expressing cells, increasing sensitivity to doxorubicin.

Conclusions:

  • Doxorubicin and Rhodamine-123 are suitable fluorescent substrates for evaluating MRP function through cellular retention assays.
  • DiOC2(3) is not appropriate for assessing MRP-mediated drug efflux due to lack of detectable retention differences.
  • These findings aid in selecting appropriate agents for MDR mechanism elucidation and therapeutic strategy development.

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