title: Comparison of two functional flow cytometric assays to assess P-gp activity in acute leukemia.
abstract: One of the possible causes of treatment failure in acute leukemia is the emergence of multidrug resistance caused by P-glycoprotein (P-gp) overexpression. We compared a flow cytometric assay using JC-1 with a technique using rhodamine 123 (rho123) to evaluate the P-gp function in acute leukemia. Samples from 50 acute leukemia patients were analyzed by both functional assays. The P-gp expression was assessed by an immunological flow cytometric test and the association between the P-gp status and the clinical outcome was evaluated. Of all samples, 28% showed a reversible JC-1 efflux and 36% scored positive for the rho123 assay. In two cases, the leukemic blasts showed a reversible JC-1 efflux whereas they were negative for rho123. These patients had blast cells with a very low P-gp activity. Six samples scored positive for the rho123 assay but were negative for the JC-1 test. Five of these samples did not express P-glycoprotein and were considered false positive. We found a strong correlation between the JC-1 and the rho123 test (R(s)=0.59, p<0.0001) and the JC-1 and the immunological assay (R(s)=0.29, P=0.05). There was also an association between the JC-1 status and the clinical outcome of adult patients (chi2=6.30, P=0.04). In conclusion, we recommend the JC-1 assay to study the P-gp activity in acute leukemia because it is more specific and less labor intensive than conventional functional flow cytometric tests using rhodamine 123. In addition, the JC-1 assay can be used to identify adult patients with an increased risk for adverse clinical outcome.
authors.affiliation: Department of Pediatric Hematology and Oncology, Ghent University Hospital, Ghent, Belgium. Katrien.Swerts@UGent.be
authors.forename: Katrien
authors.initials: K
authors.lastname: Swerts
authors.forename: Barbara
authors.initials: B
authors.lastname: de Moerloose
authors.forename: Catharina
authors.initials: C
authors.lastname: Dhooge
authors.forename: Lucien
authors.initials: L
authors.lastname: Noens
authors.forename: Geneviève
authors.initials: G
authors.lastname: Laureys
authors.forename: Yves
authors.initials: Y
authors.lastname: Benoit
authors.forename: Jan
authors.initials: J
authors.lastname: Philippé
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000328:Adult; D001562:Benzimidazoles / Q000494:pharmacology; D002232:Carbocyanines / Q000494:pharmacology; D002648:Child; D019008:Drug Resistance, Neoplasm; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000378:metabolism*; D008297:Male; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000378:metabolism*; D020112:Rhodamine 123 / Q000494:pharmacology; D012306:Risk; D016896:Treatment Outcome
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D001562:Benzimidazoles; D002232:Carbocyanines; D005456:Fluorescent Dyes; D020112:Rhodamine 123; C068624:5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine