PHOSPHOLIPASE-A(2)-INDUCED STIMULATION OF A549 LUNG ADENOCARCINOMA CELL-LINE PROLIFERATION

Phospholipase A2 (PLA2) activity was found in the cytosolic fraction o f the A549 human lung adenocarcinoma line. This PLA2 had a molecular m ass of approximately 70 kDa as assessed by gel filtration chromatograp hy and required submicromolar concentrations of calcium concentrations for optimal activity. These characteristics are consistent with the c ytosolic PLA2 recently reported in other cell types, such as U937 cell s. We have now demonstrated that A549 cell PLA2 (PLA2 activity: 1 unit /ml) partially purified by gel filtration stimulated proliferation of A549 cells by 50% after 3 days of culture. Similarly, porcine pancreat ic PLA2 (0-1 unit/ml) also promoted proliferation of A549 cell culture s by 42%. Furthermore, A549 cell PLA2 stimulated prostaglandin E2 rele ase (approx. 7-fold increase). Both PLA2s lost activity when treated w ith p-bromophenacyl bromide. Neither porcine pancreatic PLA2 nor A549 cell PLA2 reversed the inhibitory activities of dexamethasone and indo methacin on cell growth. These results suggest that both of these PLA2 s stimulate A549 cell growth, and that this is likely to be mediated b y increased eicosanoid production.