GSTM1 and glioblastoma: Furthermore, the expression of GSTM1 was significantly correlated with overall survival in this GBM cohort (Fig. 3d, p = 0.0055 and 0.0088 by log-rank and Wilcoxon test, respectively), indicating that GSTM1 could serve as a biomarker to predict GBM patients’ clinical outcome.