Modulation of plasma cyst(e)ine by cisplatin

Some types of human malignant cells are cyst(e)ine auxotrophs. In 8 cancer patients given 10 courses of treatment cisplatin caused a mean (+/- S.D.) 83 +/- 17% decrease in plasma cyst(e)ine when measured before and 6 hr after drug infusion. The magnitude of the decrease correlated with peak plasma cisplatin concentration, and serial measurements demonstrated that in some patients plasma cyst(e)ine was still decreasing at 6 hr. The mean 6-hr plasma cyst(e)ine was low enough (9 +/- 9 microM) to prevent the proliferation of human promyelocytic (HL-60) cells in culture.