Cisplatin rapidly down-regulates its own influx transporter hCTR1 in cultured human ovarian carcinoma cells.
OBJECTIVE
Cisplatin (DDP)-resistant cells commonly exhibit reduced drug accumulation. Previous studies have shown that the major copper (Cu) influx transporter CTR1 controls the uptake of DDP in yeast and mammalian cells. The goal of this study was to examine the effect of Cu and DDP on the level and subcellular localization of hCTR1 protein in human ovarian carcinoma cells.


METHODS
Cultured human ovarian carcinoma A2780 cells were exposed to DDP and Cu, and the effect on hCTR1 was determined using Western blot analysis and confocal digital deconvolution microscopy.


RESULTS
Loss of hCTR1 was triggered by DDP exposure in a concentration and time-dependent manner. Exposure to 0.5 micromol/L DDP for 5 minutes reduced hCTR1 levels and exposure to DDP concentrations > or =2 micromol/L caused almost complete disappearance. The loss of hCTR1 was observed within 1 minute of the start of exposure to 2 micromol/L DDP. Treatment of cells with 100 micromol/L Cu for 5 minutes produced a smaller effect. Pretreatment of cells with 2 micromol/L DDP for 5 minutes resulted in a 50% decrease in 64Cu uptake, demonstrating that the DDP-induced loss of hCTR1 detected by Western blot analysis and imaging was functionally significant.


CONCLUSIONS
DDP down-regulated the amount of its major influx transporter in cultured human ovarian carcinoma cells in a concentration- and time-dependent manner. The effect was observed at DDP concentrations within the range found in the plasma of patients being treated with DDP, and it occurred very quickly relative to the half-life of the drug.
Department of Medicine and the Rebecca and John Moores Cancer Center, University of California at San Diego, La Jolla, California 92093-0058, USA.
Alison K
AK
Holzer
Kuniyuki
K
Katano
Leo W J
LW
Klomp
Stephen B
SB
Howell
D000970:Antineoplastic Agents / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D015153:Blotting, Western; D027682:Cation Transport Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D003300:Copper / Q000493:pharmacokinetics / Q000494:pharmacology; D000079923:Copper Transporter 1; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005260:Female; D006801:Humans; D018613:Microscopy, Confocal / Q000379:methods; D010051:Ovarian Neoplasms / Q000378:metabolism / Q000473:pathology; D013997:Time Factors
D000970:Antineoplastic Agents; D027682:Cation Transport Proteins; D000079923:Copper Transporter 1; D003300:Copper; D002945:Cisplatin