Competitive Inhibition by Genistein and ATP Dependence of Daunorubicin Transport in Intact MRP Overexpressing Human Small Cell Lung Cancer Cells

Biochem Pharmacol. 1994 Sep 15;48(6):1129-36. doi: 10.1016/0006-2952(94)90149-x.

Abstract

In several multidrug resistant tumor cell lines without overexpression of P-glycoprotein (non-Pgp MDR), a decreased accumulation of drugs has been shown to contribute to resistance. We have recently reported that daunorubicin (DNR) accumulation was decreased in the multidrug resistance-associated protein overexpressing GLC4/ADR non-Pgp MDR small cell lung cancer cell line due to an enhanced energy-dependent efflux which could be inhibited by the isoflavonoid genistein. The purpose of this work was 2-fold: (i) to investigate the mechanism by which genistein inhibits the DNR efflux in the GLC4/ADR cells; and (ii) to characterize the dependence of DNR transport on ATP concentration in intact GLC4/ADR cells. The active transport of DNR in GLC4/ADR cells appeared to be a saturable process with an apparent Km of DNR of 1.4 +/- 0.4 microM. Genistein increased the apparent Km value of DNR, suggesting that this agent is a competitive inhibitor of DNR transport. These data provide additional evidence that energy-dependent DNR transport in GLC4/ADR cells is a protein-mediated process. In addition, genistein decreased cellular ATP concentration in a dose-dependent manner in sensitive as well as in resistant cells. Marked inhibition of DNR transport activity in intact GLC4/ADR cells was found when cellular ATP concentration was decreased below 2 mM by sodium azide or 2-deoxy-D-glucose. Thus, since DNR transport in intact GLC4/ADR is already inhibited at modest cellular ATP depletion, a limitation in ATP supply might open ways to make MDR cells more susceptible to drug toxicity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / deficiency
  • Adenosine Triphosphate / pharmacology*
  • Biological Transport / drug effects
  • Carcinoma, Small Cell / metabolism
  • Daunorubicin / metabolism*
  • Daunorubicin / pharmacology
  • Drug Resistance
  • Genistein
  • Humans
  • Isoflavones / pharmacology*
  • Lung Neoplasms / metabolism
  • Tumor Cells, Cultured / drug effects

Substances

  • Isoflavones
  • Adenosine Triphosphate
  • Genistein
  • Daunorubicin