Methylation of selected CpGs in the human O6-methylguanine-DNA methyltransferase promoter region as a marker of gene silencing

Mol Carcinog. 1999 Feb;24(2):85-9.


O6-methylguanine-DNA methyltransferase (MGMT) is a major determinant of susceptibility to methylating carcinogens and of tumor resistance to anticancer methylating and chloroethylating drugs. The silencing of MGMT expression that occurs in 20-30% of human tumor lines is tightly linked to methylation within the MGMTgene 5'CpG island. Previous studies on a very limited number of cell lines showed that such methylation was uneven, with hot-spots where methylation almost invariably occurred and intervening regions with very low incidences of methylation. To ascertain if such hot-spot methylation is in fact a ubiquitous hallmark of MGMT-silenced cells, we determined the methylation status of selected hot-spot CpGs in an extensive panel of MGMT-expressing and -silenced cell lines and xenografts. Using two simple and rapid bisulfite-polymerase chain reaction-based assays, we confirmed that in MGMT-silenced cells, methylation occurred at these sites whereas it was essentially absent in MGMT-expressing cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • Chromosome Mapping
  • CpG Islands / genetics*
  • DNA Methylation
  • Genome, Human*
  • Humans
  • O(6)-Methylguanine-DNA Methyltransferase / genetics*
  • Promoter Regions, Genetic / genetics


  • O(6)-Methylguanine-DNA Methyltransferase