TGFB1 and glioma: Repeatedquantification (n ≥ 7) of absolute TGF-β1 levels following cultivation of glioma cells for 48 hours in serum-free mediumrevealed that all cell lines investigated secrete TGF-β1 (F98: 8.45 ± 1.59 ng/mL; SMA-560: 2.7 ± 0.54 ng/mL; U-87 MG: 2.55 ± 0.68 ng/mL, U-373 MG: 0.43 ± 0.08 ng/mL), while both troglitazone and Δ2-troglitazone inhibitTGF-β1 release in a dose-dependent manner (Figures 1(b), 1(d)).