TY - JOUR
T1 - Evidence for impaired mitoxantrone and vinblastine binding in P388 murine leukemia cells with multidrug resistance
AU - Pincus, Rosemarie
AU - Goldman, I. David
PY - 1990/12/15
Y1 - 1990/12/15
N2 - Multidrug resistance is associated with a P170 glycoprotein efflux pump that limits net drug accumulation in resistant cell lines. Other evidence has suggested that diminished net drug uptake in multidrug resistant (MDR) cells is due to decreased drug binding as well. To assess the contribution of binding differences to net drug accumulation and retention in MDR cells, mitoxantrone and vinblastine, two agents commonly associated with the MDR phenotype but with different mechanisms of action and intracellular binding sites, were studied in P388 murine leukemia cells. For both drugs, resistance was associated with a marked reduction in tightly bound drug which can account for the diminished net drug accumulation in this cell line; even at 1 μM vinblastine when the exchangeable component was one-half that of the sensitive cells, the nonexchangeable component was only one-seventh. For mitoxantrone, the exchangeable drug component was greater in resistant cells at low drug levels (1 μM) and similar at high drug levels (10 μM). For vinblastine, the exchangeable drug component was decreased in the resistant cells at 1 μM, but the difference compared to sensitive cells became neglible at 10 μM. The data indicate that diminished net drug uptake in the P388 MDR cell line was associated with a marked decrease in tightly bound, i.e. nonexchangeable, drug fractions for both mitoxantrone and vinblastine. Therefore, alterations in intracellular binding are an important factor in the decreased cellular uptake and retention of drugs in the multidrug resistance phenomenon. The relationship between these changes and the P170 efflux pump requires further clarification.
AB - Multidrug resistance is associated with a P170 glycoprotein efflux pump that limits net drug accumulation in resistant cell lines. Other evidence has suggested that diminished net drug uptake in multidrug resistant (MDR) cells is due to decreased drug binding as well. To assess the contribution of binding differences to net drug accumulation and retention in MDR cells, mitoxantrone and vinblastine, two agents commonly associated with the MDR phenotype but with different mechanisms of action and intracellular binding sites, were studied in P388 murine leukemia cells. For both drugs, resistance was associated with a marked reduction in tightly bound drug which can account for the diminished net drug accumulation in this cell line; even at 1 μM vinblastine when the exchangeable component was one-half that of the sensitive cells, the nonexchangeable component was only one-seventh. For mitoxantrone, the exchangeable drug component was greater in resistant cells at low drug levels (1 μM) and similar at high drug levels (10 μM). For vinblastine, the exchangeable drug component was decreased in the resistant cells at 1 μM, but the difference compared to sensitive cells became neglible at 10 μM. The data indicate that diminished net drug uptake in the P388 MDR cell line was associated with a marked decrease in tightly bound, i.e. nonexchangeable, drug fractions for both mitoxantrone and vinblastine. Therefore, alterations in intracellular binding are an important factor in the decreased cellular uptake and retention of drugs in the multidrug resistance phenomenon. The relationship between these changes and the P170 efflux pump requires further clarification.
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U2 - 10.1016/0006-2952(90)90580-E
DO - 10.1016/0006-2952(90)90580-E
M3 - Article
C2 - 1979735
AN - SCOPUS:0025688982
SN - 0006-2952
VL - 40
SP - 2625
EP - 2635
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 12
ER -