title: Methylation Status of the O6-Methylguanine-Deoxyribonucleic Acid Methyltransferase Gene Promoter in World Health Organization Grade III Gliomas.
abstract: OBJECTIVE
  We analyzed the methylation status of the O6-methylguanine-DNA methyltransferase (MGMT) gene promoter in World Health Organization (WHO) grade III gliomas in association with other molecular markers to evaluate their prevalence.
  
  
  METHODS
  The samples of a total of 36 newly WHO grade III glioma patients including 19 anaplastic oligodendrogliomas (AO), 7 anaplastic oligoastrocytomas (AOA), and 10 anaplastic astrocytomas (AA) were analyzed. The methylation status of the MGMT gene promoter was confirmed by methylation-specific polymerase chain reaction. The 1p/19q chromosomal deletion status and EGFR amplification were assessed by Fluorescence In-Situ Hybridization. MGMT, EGFR, EGFRvIII, and p53 expression were analyzed by immunohistochemical staining.
  
  
  RESULTS
  The MGMT gene promoter was methylated in 32 (88.9%) and unmethylated in 4 (11.2%). Among them, all of the AO and AOA had methylated MGMT gene promoter without exception. Significant associations between MGMT gene promoter hypermethylation and 1p/19q deletion was observed (p = 0.003). Other molecular markers failed to show significant associations between MGMT gene promoter statuses.
  
  
  CONCLUSIONS
  There was extensive epigenetic silencing of MGMT gene in high grade gliomas with oligodendroglial component. Together with frequent 1p/19q co-deletion in oligodendroglial tumors, this may add plausible explanations supporting the relative favorable prognosis in oligodendroglial tumors compared with pure astrocytic tumors.
authors.affiliation: Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Seung-Heon
authors.initials: SH
authors.lastname: Yang
authors.forename: Yong Hwy
authors.initials: YH
authors.lastname: Kim
authors.forename: Jin Wook
authors.initials: JW
authors.lastname: Kim
authors.forename: Chul-Kee
authors.initials: CK
authors.lastname: Park
authors.forename: Sung-Hye
authors.initials: SH
authors.lastname: Park
authors.forename: Hee-Won
authors.initials: HW
authors.lastname: Jung