IDH1 and central nervous system cancer: As a well-known prognostic marker, glioblastomas with hypermethylated promoter regions for O6-methylguanine DNA methyltransferase (MGMT), a gene responsible for DNA repair of O6-methylguanosine, are associated with better response to TMZ and improved survival rates.2,303 Furthermore, genome-wide methylation profiling has shown that gliomas with an overall hypermethylated pattern at CpG islands (the CpG island methylator phenotype or G-CIMP) are strongly associated with other prediction markers, including IDH1 mutation and MGMT promoter methylation status.