MGMT and glioblastoma: The downregulation of MGMT expression through promoter methylation has been shown in various human cancers, including lung cancer, glioblastoma, gastric carcinoma, and salivary gland carcinoma (Cabrini, Fabbri, Lo Nigro, Dechecchi, & Gambari, 2015; Lee et al., 2008; Pulling et al., 2003; Yousuf et al., 2014).