Coumarin in melanoma patients: An experimental and clinical study

Coumarin, a natural ingredient of higher plants, was studied for its effect on natural killer cell activity and for its binding properties to tumor cell surfaces in vitro. Furthermore, melanoma patients (State I and II) and patients with disseminated metastatic disease were followed up by a clinical protocol and screening programme when taking 100 mg coumarin daily. Coumarin exhibited an enhancement of natural killer cell activity in vitro, but in patients this effect was negligible. Coumarin bound to cell surfaces of a panel of tumor cells in vitro at different binding constants. To stimulate lytic activity of mononuclear cells of healthy donors, the whole set of immune competent cells has to be incubated with coumarin, which suggests intracellular cooperation phenomena. Coumarin seemed to be effective in extending recurrence-free intervals in surgically-treated Stage I and II patients (Clark II/IV), but so far proved ineffective in widespread disseminated disease. Coumarin is easy to apply and no discomfort was reported by the patients in the ongoing clinical trial for 18 months.