MODULATION OF LIPOXIDASE ACTIVITY BY UROKINASE-TYPE PLASMINOGEN-ACTIVATOR

Malignant cells show increased urokinase (UK) activity and decreased p eroxidation of essential fatty acids (EFA). In order to explore this p henomenon the effect of UK on the liposidase activity was spectrophoto metrically investigated. Decreased lipoxidase activity was obtained wi th increased UK concentrations (r = -1.000, p < 0.0001). This proteoly tic effect of UK on lipoxidase was eliminated with the addition of the UK inhibitor leupeptin. These results suggest that the increase in UK activity in malignant cells may decrease the liposidase activity and thus peroxidation of EFA. The effectiveness of a given EFA in killing cancer cells would therefore depend on the modulation of the lipoxidas e activity by the UK-type plasminogen activator.