Excluding from the analysis the slow proliferating #23 GSC line, which is resistant to TMZ even though it lacks MGMT activity, MGMT activity/expression by GSCs inversely correlated with the overall survival of patients from whom the tumor cells were derived (for MGMT activity, Spearman’s correlation = −0.79, P = 0.01; for MGMT protein expression, Spearman’s correlation = −0.85, P = 0.003; n = 9). Here, MGMT is linked to neoplasm.