ENHANCED EFFLUX OF [H-3]VINBLASTINE FROM CHINESE-HAMSTER OVARY CELLS TRANSFECTED WITH A FULL-LENGTH COMPLEMENTARY-DNA CLONE FOR THE MDR1 GENE

  • 15 July 1989
    • journal article
    • research article
    • Vol. 49  (14) , 3867-3871
Abstract
Multidrug-resistant Chinese hamster ovary cell clones stably transfected with, and overexpressing, the mouse mdr1 complementary DNA clone along with drug-sensitive Chinese hamster ovary control cells were characterized for their capacities to accumulate and retain [3H]vinblastine. Multidrug-resistant mdr1 transfectants show a 3- to 4-fold decrease in [3H]-vinblastine accumulation, compared to their drug-sensitive counterparts. After ATP depletion, this difference in [3H]vinblastine accumulation between mdr1 transfectants and control cells effectively disappears. This ATP-dependent decreased drug accumulation is paralleled in mdr1 transfectants by an enhanced capacity of these cells to extrude the drug in an ATP-dependent manner. In medium containing glucose and glutamine, the mdr1 transfectants release preloaded drug at a rate five times that of control, drug-sensitive cells. In ATP-depleted control and mdr1-transfected cells, there is little difference in the rate or extent of [3H]vinblastine release. The observation that the mdr1 transfectants show a decreased [3H]vinblastine accumulation and an increased vinblastine release, both of which are abolished when cellular ATP levels are reduced, provides a direct demonstration that the product of the transfected mdr1 gene is responsible for a mechanism controlling drug levels in an ATP-dependent manner. However, attempts to establish competition for [3H]vinblastine transport by vincristine, duanomycin, and actinomycin D were only part successful in mdr1 transfectants.