Effect of copper and role of the copper transporters ATP7A and CTR1 in intracellular accumulation of cisplatin.

An investigation was carried out as to whether copper affected the intracellular accumulation of cisplatin (cis-diamminedichloroplatinum(II); CDDP) and whether changes in the expression of ATP7A and CTR1 were related to acquired resistance using CDDP-sensitive (KB) and -resistant (KBR/0.8, KBR/1.2) cells. Intracellular platinum accumulation and platinum-DNA adducts were significantly lower in the CDDP-resistant sublines compared with KB cells. Treatment with 750 microM CuSO4 increased the amount of intracellular platinum 1.8-, 3.2-, and 3.9-fold in KB, KBR/0.8, and KBR/1.2 cells respectively, and increased the platinum-DNA adducts by 1.9-fold in KB cells and by 3.2-fold in KBR/1.2 cells. The level of ATP7A was greatly reduced and CTR1 expression slightly decreased in KBR/1.2 cells compared with KB cells. ATP7A expression was markedly increased by exposure to CDDP with or without copper in KB cells but not in KBR/1.2 cells. CDDP and copper did not increase the level of CTR1 in KB or KBR/1.2 cells. These results indicate that a high concentration of copper causes a significant increase in the cellular accumulation of CDDP and binding of platinum to DNA independently of CTR1 expression in KB cells and CDDP-resistant sublines thereof and that the acquisition of CDDP resistance is associated with a greatly reduced level of ATP7A and a marginally lower expression of CTR1.