GSS and glioblastoma: We also analyzed expression of proteins involved in oxidative stress response, e.g., GSS, GSTO1, hMTH1, SOD1, SOD2, APE1, and NRF2, by comparing U87MG neurospheres, differentiated U87MG cells and 4 other GBM cell lines: T98G, LN18, M059K, and M059J.