Restoration of DKK1 expression by a demethylating agent 5-azacytidine in T98 GBM cells enhances their susceptibility to camptothecin- and etoposide-induced apoptosis (Foltz et al., 2010), suggesting that treatment of GBM cells with inhibitors of promoter methylation for tumor suppressors facilitates drug efficacy. This evidence concerns the gene DKK1 and glioblastoma.