TM-1 cells from an established human malignant glioma cell line produce PDGF, TGF-?, and TGF-? which cooperatively play a stimulatory role for an autocrine growth promotion

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Abstract
We have previously established a human malignant glioma cell line, TM-1. TM-1 cells could proliferate in the serum-free medium. In the present study, immunochemical analysis demonstrated that platelet-derived growth factor (PDGF), transforming growth factor (TGF)-α, and TGF-β are present in the serum-free medium conditioned by growing TM-1 cells. While the cells appeared to possess a single type of binding sites for epidermal growth factor (EGF) with properties comparable to those determined for other tumor cells, the conditioned medium did not contain EGF. PDGF, TGF-α, and EGF added exogenously to serum-free media stimulated thymidine incorporation into DNA of TM-1 cells. In addition, antibodies specific for PDGF and TGF-α suppressed this activity. These results indicate autocrine and stimulatory roles of PDGF and TGF-α for the proliferation of TM-1 cells. As observed for other tumor cells, TGF-β by itself weakly suppressed thymidine incorporation by TM-1 cells. However, TGF-β employed in combination with TGF-α or EGF appeared to stimulate thymidine incorporation, suggesting that a cooperative action of TGF-β with different growth factors may be involved in the stimulatory growth regulation at least for TM-1 cells.