Partial cross-resistance between auranofin and sodium aurothiomalate in cultured human cells

Cross-resistance between auranofin and sodium aurothiomalate was tested in two substrains of cultured human epithelial cells. The HEAF cells were previously made resistant to the otherwise lethal concentration of 2 mumol auranofin per litre of culture medium. The HEmyo cells were made resistant to the otherwise lethal effect of 300 mumol sodium aurothiomalate/l. After 4 days of continuous treatment with 2 mumol auranofin/l, 4.6% of the parent HE cells, 55.7% of the HEAF cells and 51.7% of the HEMyo cells continued to grow, compared with controls grown without drug supplement. After 4 days on 300 mumol sodium aurothiomalate/l, 17.6% of the HE cells, 101.0% of the HEMyo cells and 45.3% of the HEAF cells continued to grow. Thus, there was an almost complete cross-resistance to auranofin in the HEMyo cells, and a relative cross-resistance to sodium aurothiomalate in the HEAF cells. The cross-resistance was not found to be related to decreased cytosolic concentration of total gold in the cross-resistant lines.