Inhibition of P-glycoprotein activity in human leukemic cells by mifepristone.
The antiprogestatin drug mifepristone has previously been shown to potentiate anti-cancer drug activity in rodent multidrug-resistant cell lines through inhibition of P-glycoprotein (P-gp) function. In order to characterize P-gp-mifepristone interactions in human tumoral cells, we have studied the effect of the antiprogestatin agent on P-gp activity in human CD34+ leukemic cells known to display high levels of P-gp-related drug efflux. P-gp-mediated transport of the fluorescent dye rhodamine 123 occurring in the CD34+ KG1a myeloid leukemia cell line was found to be strongly inhibited by mifepristone in a dose-dependent manner. Similarly to verapamil, a well-known chemosensitizer agent, the antiprogestatin drug increased doxorubicin cytotoxicity in KG1a cells. Mifepristone, when used at a 10 microM concentration thought to be achievable in vivo without major toxicity, was also able to markedly decrease cellular rhodamine 123 efflux occurring in CD34+ blast cells isolated from six patients suffering from myeloid acute leukemias. These results thus indicate that mifepristone can strongly inhibit P-gp activity in human cells, including tumoral cells freshly isolated from patients, therefore suggesting that the clinical use of this compound may contribute to down-modulate P-gp-mediated drug resistance.
Fardel
O
O
Groupe Détoxication et Réparation Tissulaire, Faculté de Pharmacie, Rennes, France.
Courtois
A
A
Drenou
B
B
Lamy
T
T
Lecureur
V
V
le Prisé
P Y
PY
Fauchet
R
R
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D006727:Hormone Antagonists / Q000494:pharmacology*; D006801:Humans; D007938:Leukemia / Q000188:drug therapy* / Q000378:metabolism; D015735:Mifepristone / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D006727:Hormone Antagonists; D015735:Mifepristone; D004317:Doxorubicin