Methylation of selected CpGs in the human O6-methylguanine-DNA methyltransferase promoter region as a marker of gene silencing
✍ Scribed by Rebecca Prapurna Danam; Xilin C. Qian; Sherie R. Howell; Thomas P. Brent
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 116 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0899-1987
No coin nor oath required. For personal study only.
✦ Synopsis
O 6 -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 MGMT gene 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.