Fig. 2
Induction of mitochondrial O2 − generation and oxidative stress response in glioblastoma stem cells. a Effect of serum on mitochondrial O2 − and total cellular ROS in GSC11 cells. Cells were incubated without or with 5 % FBS for 1, 3, or 7 days (D1, D3, D7). Mitochondrial O2 − was measured by flow cytometry analysis after cells were stained with MitoSOX-Red, and total cellular ROS were detected by using CM-H2-DCFDA staining followed by flow cytometry analysis. The numbers in parentheses indicate the median fluorescent intensity. b Effect of serum exposure (1–7 days) on mitochondrial O2 − and total cellular ROS in GBM3752 cells. c Effect of serum on mitochondrial O2 − and total cellular ROS in primary tumor cells isolated from fresh GBM tumor tissue. The freshly isolated tumor cells were divided into two portions for incubation in stem cell medium without or with serum (5 % FBS) for 7 days, and mitochondrial O2 − and total cellular ROS were then measured. The shaded curve shows the background (Bkg) fluorescent without dye. d Western blot analysis of SOD1, SOD2, and catalase in GSC11 cells before and after exposure to serum for 1, 3, and 7 days. e Cellular glutathione in GSC11 cells cultured in stem cell medium without or with serum for 1, 3, and 7 days. *P < 0.05. Cont control, DCF-DA 5-(and-6)-chloromethyl-2,7-dichlorodihydrofluorescein diacetate acetyl ester, FBS fetal bovine serum, GBM glioblastoma multiforme, GSH glutathione, GSC glioma stem cell, O 2 − superoxide, ROS reactive oxygen species, SOD cytosolic superoxide dismutase