Cytosine methylation and suppression of O6-methylguanine-DNA methyltransferase expression in human rhabdomyosarcoma cell lines and xenografts.

Published

Journal Article

Human tumor cell lines that do not express O6-methylguanine-DNA methyltransferase (MGMT) in detectable quantities (Mer-) are hypersensitive to the effects of O6-guanine-alkylating agents. Because the Mer- phenotype enhances tumor response to such agents, we investigated possible mechanisms involved in regulation of MGMT expression in a panel of Mer+ and Mer- pediatric rhabdomyosarcoma xenograft and cell lines. All Mer- cell and xenograft lines lacked not only MGMT activity but also the protein and mRNA as well, suggesting that its expression is transcriptionally regulated. Transfection of Mer+ and Mer- rhabdomyosarcoma cell lines with MGMT gene promoter-CAT constructs yielded similar levels of CAT expression, indicating that Mer- cells possessed the necessary factors to support transcription. Methylation in the 5'-untranslated region of the MGMT gene was assayed by Southern analysis using methylation-sensitive restriction enzymes. Digestion with HpaII and its methylation-insensitive isoschizomer, MspI, revealed little overall correlation between methylation and MGMT expression. However, methylation in a single SmaI site at position-69 was observed in all MGMT deficient lines but not in any MGMT expressing lines. These results suggest that methylation of specific cytosines in the MGMT promoter may play a role in suppressing its expression, as well as being a potentially useful marker for the Mer- phenotype.

Full Text

Duke Authors

Cited Authors

  • von Wronski, MA; Harris, LC; Tano, K; Mitra, S; Bigner, DD; Brent, TP

Published Date

  • 1992

Published In

Volume / Issue

  • 4 / 4-5

Start / End Page

  • 167 - 174

PubMed ID

  • 1504376

Pubmed Central ID

  • 1504376

International Standard Serial Number (ISSN)

  • 0965-0407

Language

  • eng

Conference Location

  • United States