For example, while histone H3 lysine 27 trimethylation (H3K27me3) is associated with the silencing of tumor suppressor genes,20, 21 histone acetylation, specifically H3K27 acetylation (H3K27ac), has been linked to enhanced MGMT expression and consequently increased resistance to TMZ, irrespective of the promoter's methylation status.22 This evidence concerns the gene MGMT and neoplasm.