Probenecid reverses multidrug resistance in multidrug resistance-associated protein-overexpressing HL60/AR and H69/AR cells but not in P-glycoprotein-overexpressing HL60/Tax and P388/ADR cells.
OBJECTIVE
To determine whether probenecid, an inhibitor of organic anion transport, is able to reverse multidrug resistance (MDR) through modulation of the drug transport function of MDR-associated protein (MRP) and P-glycoprotein (P-gP).


METHODS
Two MRP-overexpressing cell lines (HL60/AR and H69/AR) and two P-gP-overexpressing cell lines (HL60/Tax and P388/ADR) were cultured with different concentrations of daunorubicin (DNR) or vincristine (VCR) in the presence or absence of various concentrations of probenecid (0.01-10 mM). Drug sensitivity was determined using an MTT assay. DNR accumulation and subcellular distribution were determined by flow cytometry and confocal microscopy respectively. VCR accumulation was determined by scintillation spectrometry.


RESULTS
Probenecid, in a concentration-dependent manner, reversed resistance to DNR and VCR in HL60/AR and H69/AR tumor cell lines. This effect of probenecid on MDR was associated with an increased accumulation of DNR and VCR and correction of the altered subcellular distribution of DNR. The concentrations of probenecid that reversed MDR are clinically achievable in vivo. In contrast, probenecid did not reverse MDR in either HL60/Tax or P388/ADR tumor cell lines that overexpress P-gP.


CONCLUSIONS
These results suggest that probenecid is an effective chemosensitizer of MRP-associated MDR tumor cells and is a potential candidate for clinical use to reverse MDR.
Gollapudi
S
S
Division of Basic and Clinical Immunology, University of California, Irvine 92717, USA.
Kim
C H
CH
Tran
B N
BN
Sangha
S
S
Gupta
S
S
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis*; D018528:ATP-Binding Cassette Transporters / Q000032:analysis*; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000032:analysis; D000972:Antineoplastic Agents, Phytogenic / Q000032:analysis; D002460:Cell Line; D003630:Daunorubicin / Q000032:analysis; D018432:Drug Resistance, Multiple; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D007941:Leukemia P388; D051379:Mice; D018613:Microscopy, Confocal; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000032:analysis*; D011339:Probenecid / Q000494:pharmacology*; D014750:Vincristine / Q000032:analysis
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000903:Antibiotics, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D003630:Daunorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D011339:Probenecid; D014750:Vincristine