|
Blockage
of drug resistance in vitro by disulfiram, a drug used to treat alcoholism
Loo TW,
Clarke DM
Departments
of Medicine, University of Toronto, ON, Canada
Background.
P-glycoprotein (P-gp) pumps a wide range of cytotoxic drugs out of cells.
Inhibiting maturation of P-gp would be a novel method for circumventing
P-gp-mediated multidrug resistance, which complicates cancer chemotherapy and
treatment of patients infected with human immunodeficiency virus.
We examined the effect of disulfiram (Antabuse(TM)) on the maturation and
activity of P-gp.
Methods.
Embryonic kidney cells were transfected with a complementary DNA for the P-pg
gene, and the effects of disulfiram on the sensitivity of the transfected cells
to cytotoxic agents were determined.
Enzyme assays were used to determine the effects of disulfiram on the
verapamil-stimulated adenosine triphosphatase (ATPase) activity of P-gp.
Disulfiram modifies cysteine residues, and mutant forms of P-gp that lack
individual cysteines were used to determine whether particular cysteine residues
mediate disulfiram's effects on P-gp activity.
Maturation of recombinant P-gp was followed on immunoblots.
Results.
Disulfiram increased the sensitivity of P-gp-transfected cells to vinblastine
and colchicine and inhibited P-gp's verapamil-stimulated ATPase activity.
Half-maximal inhibition of ATPase activity occurred at 13.5 &mgr;M
disulfiram.
Disulfiram (at 100 &mgr;M) inhibited a P-gp mutant by 43% (95% confidence
interval [CI] = 37%-48%) when cysteine was present at position 431 only and by
72% (95% CI = 66%-77%) when cysteine was present at position 1074 only.
Treatment of P-gp-transfected cells with 50 nM disulfiram blocked maturation of
recombinant P-gp.
Conclusions.
Disulfiram can potentially reduce P-gp-mediated drug resistance by inhibiting
P-gp activity (possibly via cysteine modification) and/or by blocking its
maturation.
These results suggest that disulfiram has the potential to increase the efficacy
of drug therapies for cancer and acquired immunodeficiency syndrome.
PMID:
10841824 [PubMed - indexed for MEDLINE]
Source:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10841824&dopt=Abstract |
