TM-1 CELLS FROM AN ESTABLISHED HUMAN-MALIGNANT GLIOMA CELL-LINE PRODUCE PDGF, TGF-ALPHA, AND TGF-BETA WHICH COOPERATIVELY PLAY A STIMULATORY ROLE FOR AN AUTOCRINE GROWTH PROMOTION

We have previously established a human malignant glioma cell line, TM- 1. TM-1 cells could proliferate in the serum-free medium. In the prese nt study, immunochemical analysis demonstrated that platelet-derived g rowth factor (PDGF), transforming growth factor (TGF)-alpha, and TGF-b eta are present in the serum-free medium conditioned by growing TM-1 c ells. While the cells appeared to possess a single type of binding sit es for epidermal growth factor (EGF) with properties comparable to tho se determined for other tumor cells, the conditioned medium did not co ntain EGF. PDGF, TGF-alpha, and EGF added exogenously to serum-free me dia stimulated thymidine incorporation into DNA of TM-1 cells. In addi tion, antibodies specific for PDGF and TGF-alpha suppressed this activ ity. These results indicate autocrine and stimulatory roles of PDGF an d TGF-alpha for the proliferation of TM-1 cells. As observed for other tumor cells, TGF-beta by itself weakly suppressed thymidine incorpora tion by TM-1 cells. However, TGF-beta employed in combination with TGF -alpha or EGF appeared to stimulate thymidine incorporation, suggestin g that a cooperative action of TGF-beta with different growth factors may be involved in the stimulatory growth regulation at least for TM-1 cells.