Y. Kataoka et al., Reversal of vinblastine resistance in human leukemic cells by haloperidol and dihydrohaloperidol, BIOL PHAR B, 24(6), 2001, pp. 612-617
Haloperidol, an antipsychotic, was investigated in cells overexpressing P-g
lycoprotein to determine whether it was a clinically effective drug to reve
rse for reversing multidrug resistance (MDR) mediated by P-glycoprotein. A
nontoxic concentration of haloperidol (1-30 mum) enhanced the cytotoxic eff
ects of vinblastine (VBL) concentration-dependently in VBL-resistant human
leukemia (K562/VBL) cells, but had no effect in the parent cells. Haloperid
ol also enhanced the cytotoxicities of epirubicin, doxorubicin and actinomy
cin D in the K562/VBL cells, but not those of idarubicin or cisplatin; this
enhancement was less than that of the VBL, toxicity in the VBL-resistant t
umor line. Haloperidol increased the intracellular accumulation of VBI. in
the K562/VBL, cells, and the binding of [H-3]-azidopine to the cell-surface
protein, P-glycoprotein, was inhibited by haloperidol in a concentration-d
ependent manner. Haloperidol was less potent than verapamil. Thus, haloperi
dol appeared to potentiate anticancer agents through the reversal of MDR by
competitively inhibiting drug-binding to P-glycoprotein. In contrast, the
main metabolite of haloperidol, dihydrohaloperidol, without antipsychotic a
ctivity had less of an effect, Therefore, haloperidol might be useful in re
versing drug-resistance.