Received for publication April 21, 2004.
Revised June 30, 2004.
Accepted for publication June 30, 2004.

The copper influx transporter hCTR1 regulates the uptake of cisplatin in human ovarian carcinoma cells

Abstract

Cells selected for resistance to cisplatin (DDP) are often cross-resistant to copper (Cu) and vice versa, and the major Cu influx transporter hCTR1 has been shown to regulate the uptake of DDP, carboplatin and oxaliplatin in yeast. To further define the role of hCTR1 in human tumor cells, the ovarian carcinoma cell line A2780 was molecularly engineered to increase expression of hCTR1 by a factor of 20-fold. Enhanced expression of hCTR1 in the A2780/hCTR1 cells was associated with a 6.5-fold increase in basal steady-state Cu content and a 13.7-fold increase in initial Cu influx demonstrating that the exogenously expressed hCTR1 was functional in altering Cu homeostasis. The A2780/hCTR1 cells accumulated 46 % more platinum following a 1 hr exposure to 2 µM DDP, and 55 % more following a 24 hr exposure, than the control A2780/EV cells. The initial uptake of DDP was 81% higher in the A2780/hCTR1 cells when measured at 5 min. Thus, increased expression of hCTR1 had a substantially larger effect on the cellular pharmacology of Cu than DDP. Interestingly, the increased uptake of Cu and DDP was accompanied by only a marginal increase in sensitivity to the cytotoxic effect of Cu and DDP, and there was no increase in the extent of DDP-DNA adduct formation. Thus, although increased expression of hCTR1 mediates greater cellular accumulation of Cu and DDP, hCTR1 delivers these compounds into intracellular compartments from which they do not have ready access to their key cytotoxic targets.

Key words: Mass Spectroscopy, Protein-binding, Pharmacokinetics, metabolism & activation

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