MGMT and glioblastoma: However, excluding from the analysis the GSC and GBM cell lines resistant to TMZ for mechanisms unrelated to MGMT status, such as the extremely low proliferation rate (i.e., #23 GSC) or MMR deficiency (i.e., SJGBM-2), sensitivity to TMZ inversely correlated with MGMT activity levels (Spearman’s correlation = 0.79, P = 0.006; n = 10).