Role of phosphoinositide 3OH-kinase in autocrine transformation by PDGF-BB

Phosphoinositide 30H-kinases (P13K) are a family of lipid kinases that acti vates signalling pathways important for migration, cytoskeletal rearrangeme nts, and cell survival. These processes are important hallmarks in transfor mation. We have evaluated the functional role of P13K for development of a transformed morphology and migratory responses of murine fibroblasts (NIH/s is and COL1A1/NIH3T3 cell lines) stimulated in an autocrine fashion by cons titutive expression of platelet-derived growth factor-BB (PDGF-BB). We show that prolonged treatment with the specific P13K inhibitor LY294002, induce d a reversion of the transformed morphology, and prevented density-independ ent growth and focus formation. Functional P13K was also required for devel opment of the transformed morphology of NIH/sis and COL1A1/NIH3T3. Furtherm ore, treatment with LY294002 completely perturbed random migration of the c ells. In addition our data show that, in the signalling pathways downstream of P13K, activation of the small GTPase Rac was a prerequisite for the tra nsformation signal. Our data also indicate the presence of a suramin-insens itive P13K activity. Most likely this was due to the presence of a suramin- insensitive intracellular PDGFR pool that allowed activation of P13K locate d in intracellular compartments. In conclusion these data show that intact P13K activity was required for the morphological alterations and the enhanc ed migratory response that are hallmarks for PDGF induced autocrine transfo rmation.