Effects of growth factors on a human glioma cell line during invasion into rat brain aggregates in culture

Cultures of fetal rat brain cell aggregates and tumor spheroids from the human glioma cell line GaMG were treated with epidermal growth factor (EGF), fibroblast growth factor (FGF) or isoforms of platelet-derived growth factor (PDGF AA or BB). Radioreceptor binding studies displayed a high binding capacity for EGF and FGF, but not binding of PDGF isoforms in the glioma cells. In serum-free culture, 10 ng/ml of both EGF and FGF caused increased growth and cell shedding in the tumor spheroids, whereas PDGF produced no such effect. Similarly, EGF and FGF stimulated tumor cell migration. EGF increased the proliferation and outgrowth of glial fibrillary acidic protein (GFAP)-positive cells in brain cell aggregates, while PDGF AA and BB both stimulated the outgrowth of oligodendrocyte-like cells which were negative for GFAP and neuron-specific enolase. FGF stimulated GFAP⁺ as well as GFAP^- cell types. In co-culture experiments using brain aggregates and tumor spheroids, both EGF and FGF treatment caused increased tumor cell invasion. PDGF had no effect on the tumor cells, but instead stimulated the proliferation of oligodendrocyte-like cells in the brain aggregates. The present results indicate that growth factors may facilitate glioma growth as well as invasiveness, and cause reactive changes in the surrounding normal tissue.