Effects of transforming growth factor-β1 and basic fibroblast growth factor on proliferation of cell cultures derived from human vestibular nerve schwannoma

The influence of transforming growth factor-beta 1 (TGF-beta 1) and basic fibroblast growth factor (bFGF) on growth of cell cultures derived from unilateral vestibular nerve schwannomas was investigated. Cell cultures were initiated from 9 schwannomas and characterized immunocytochemically with antibodies against S-100 and type IV collagen. The effects of TGF-beta 1 and bFGF on DNA synthesis in chemically defined serum-free medium were assessed by measuring the incorporation of 5-bromo-2'-deoxy-uridine (BRDU) into cellular DNA. Cell proliferation was evaluated with an electronic cell counter. Reverse transcription polymerase chain reaction (RT-PCR) was performed using oligonucleotide primers specific for TGF-beta 1 and TGF-beta 2. TGF-beta 1 stimulated DNA synthesis in a dose dependent manner. Maximal stimulation was observed at a concentration of 1 ng/ml, which induced a nearly 2-fold increase in DNA content. This effect was not seen when TGF-beta 1 was added in the presence of neutralizing antibodies. In addition, antibodies against TGF-beta 1 significantly reduced DNA synthesis in control cultures without supplemented exogenous growth factors, bFGF alone had no significant effects on DNA synthesis. In contrast, when TGF-beta 1 and bFGF were added together, the mitogenic response was much greater than produced by TGF-beta 1 alone. RT-PCR showed that the cultured cells expressed mRNA for both TGF-beta 1 and TGF-beta 2. We hypothesize that TGF-beta 1 is an autocrine growth factor for human vestibular nerve schwannomas in culture. A similar mechanism might be involved in the growth of these tumors in situ.