Cell lines and culture condition

Glioma cell lines F98 and U87 were obtained from ATCC/LGC-2397 (Germany) and were cultured under standard condition containing DMEM medium (Biochrom, Berlin, Germany) supplemented with 10% fetale bovine serum (Biochrom), 1% Penicillin/Streptomycin (Biochrom) and 1% Glutamax (Gibco/Invitrogen). Cells were passaged at ~80% confluence by adding trypsin after one PBS wash step and incubated for 5 min, then centrifuged at 900 r.p.m./5 min. Cell lines were transfected according to Broggini et al.⁴⁶ Briefly, cells were plated at 20 000/cm² in six-well plates and held under standard conditions. Twenty  hours after seeding, transfection was performed using Roti-Fect (Roth) according to the manufacturer's protocol. Transfected cells were selected with geneticin sulfate 418 and positive cell were expanded (Sigma). For mycoplasma contamination was tested.