Published in Cancer Detection and Prevention 1997; 21(1):78-82.

Comparison of Daunorubicin and Fluo-3 for Detection of Multidrug Resistance in Human Tumor Cells

Eric E O Gheuens MD, Sylke A M van der Heyden PhD, Hilde E. Elst, Allan T Van Oosterom, MD PhD, Ernst A DeBruijn MD PhD

Laboratory for Cancer Research & Clinical Oncology, University of Antwerp, Wilrijk, Belgium

Address all correspondence and reprint requests to: Ernst A. De Bruijn, MD, Ph.D., Laboratory for Cancer Research & Clinical Oncology, University of Antwerp, Universiteitsplein 1 (T-3), 2610 Wilrijk, Belgium.

ABSTRACT: The detection of multidrug resistance (MDR) in clinical samples is still a topic for discussion. One method, proven extremely useful for detection of membrane proteins in patients with hematological malignancies is the flow cytometrical analysis of individual tumor cells. Recently an assay was described based on the labeling of the P-glycoprotein (P-gp) with the monoclonal antibody MRK16, combined with detection of active daunorubicin (DNR) extrusion. In order to improve the specificity of the assay, on line with the results obtained by Wall et al., we exploited staining with Fluo-3. Both assays prove to be able to discriminate between drug-resistant and drug-sensitive cells. A major drawback of labeling with Fluo-3 in combination with the monoclonal antibody MRKl6 is the important overlap of emission spectra of both fluorochromes. Moreover, using Fluo-3 for the detection of MDR might be complicated by the fact that differences in fluorescence intensities are not solely dependent on the presence of P-gp, but also on the activity of cytosolic esterases and the intracellular calcium concentration. Combination of the detection of structural and functional aspects of the MDR-associated protein may lead to a more precise detection of the MDR-positive patient.

KEY WORDS: flow cytometry, double labeling, P-glycoprotein, Fluo-3.