Changes in the Expression of Various Transporters as Influencing Factors of Resistance to Cisplatin.

BACKGROUND: Changes in the expression of transporters have been reported as factors in resistance to cisplatin (CDDP). This study was designed to clarify whether CDDP-resistant strains isolated from a cell line had the same characteristics, and whether these characteristics could be therapeutic targets. MATERIALS AND METHODS: Intracellular platinum levels were determined by the inductively-coupled plasma method. mRNA expression levels were determined using the real-time polymerase chain reaction. RESULTS: Some CDDP-resistant HepG2 cell lines exhibited changes in the expression of copper transporter 1, multidrug resistant protein (MRP)2, and/or MRP3, resulting in decreased intracellular platinum amounts, while others showed no change in platinum accumulation. Expression of these transporters was not necessarily maintained in a constant direction within the cell population isolated from the same origin. CONCLUSION: These results suggest that the CDDP-resistant tumors caused by a decrease in intracellular platinum content consist of a heterogeneous cell population showing expression changes of several transporters.