Enzymocytochemical staining showing the senescence of glioblastoma cells cultured under various conditions.

SA-β-Gal-positive cells were observed in all tested conditions. (A) An early passage of GB cells under monolayer serum conditions; (B) A late passage of GB cells under monolayer serum conditions; (C) A late passage of GB cells under monolayer serum-free conditions; (D) The cells in an early spheroid; (E) The cells in a late spheroid; (F) The cells in a late floating spheroid.