One classical example is that methylation of the MGMT (O6-methylguanine-DNA methyltransferase) promoter in gliomas is a useful predictor of the responsiveness of the tumors to alkylating agent carmustine [1,3-bis(2-chloroethyl)-1-nitrosourea], as well as of overall and disease-free survival in gliomas [6]. Here, MGMT is linked to central nervous system cancer.