Correlations between promoter methylation and favorabletreatment response after chemotherapy with TMZ or other alkylating agents areexplained by the assumption that DNA methylation of a cysteine-phosphate-guanine(CpG) island (CGI) within the MGMT promoter directly leads to arepression of MGMT transcriptional activity and MGMT proteinexpression [6];determination of the promoter methylation status may thus serve as a“chemosensitivity sensor” in glioma patients. The gene discussed is MGMT; the disease is glioma.