Heterogeneous methylation of the O6-methylguanine-DNA methyltransferase promoter in immortalized IMR90 cell lines

Danam,Rebecca P.; Howell,Sherie R.; Remack,Joanna S.; Brent,Thomas P.

doi:10.3892/ijo.18.6.1187

June 2001 Volume 18 Issue 6

Full Size Image

Cover Legend PDF

Journals

International Journal of Molecular Medicine

International Journal of Molecular Medicine is an international journal devoted to molecular mechanisms of human disease.

International Journal of Oncology

International Journal of Oncology is an international journal devoted to oncology research and cancer treatment.

Molecular Medicine Reports

Covers molecular medicine topics such as pharmacology, pathology, genetics, neuroscience, infectious diseases, molecular cardiology, and molecular surgery.

Oncology Reports

Oncology Reports is an international journal devoted to fundamental and applied research in Oncology.

Experimental and Therapeutic Medicine

Experimental and Therapeutic Medicine is an international journal devoted to laboratory and clinical medicine.

Oncology Letters

Oncology Letters is an international journal devoted to Experimental and Clinical Oncology.

Biomedical Reports

Explores a wide range of biological and medical fields, including pharmacology, genetics, microbiology, neuroscience, and molecular cardiology.

Molecular and Clinical Oncology

International journal addressing all aspects of oncology research, from tumorigenesis and oncogenes to chemotherapy and metastasis.

World Academy of Sciences Journal

Multidisciplinary open-access journal spanning biochemistry, genetics, neuroscience, environmental health, and synthetic biology.

International Journal of Functional Nutrition

Open-access journal combining biochemistry, pharmacology, immunology, and genetics to advance health through functional nutrition.

International Journal of Epigenetics

Publishes open-access research on using epigenetics to advance understanding and treatment of human disease.

Medicine International

An International Open Access Journal Devoted to General Medicine.

June 2001 Volume 18 Issue 6

Full Size Image

Cover Legend PDF

Article

Heterogeneous methylation of the O6-methylguanine-DNA methyltransferase promoter in immortalized IMR90 cell lines

Authors:
- Rebecca P. Danam
- Sherie R. Howell
- Joanna S. Remack
- Thomas P. Brent
View Affiliations / Copyright

Affiliations: Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
Pages: 1187-1193
|
Published online on: June 1, 2001

https://doi.org/10.3892/ijo.18.6.1187
Expand metrics +

Abstract

Transcriptional silencing of the DNA repair protein, O6-methylguanine-DNA methyltransferase (MGMT), occurs only in malignant or transformed cell lines, and such MGMT-deficient cells are hypersensitive to chemotherapeutic alkylating agents such as 1, 3-bis (2-chloroethyl)-1-nitrosourea (BCNU) and temozolomide. Previously we demonstrated in a panel of established cell lines that the lack of gene expression correlated with methylation within the CpG island in the MGMT 5' gene flank. Now, we investigated the relationship between CpG methylation, MGMT suppression and drug-sensitivity in normal, diploid MGMT-expressing IMR90 cells and five immortalized sublines (AA, EE, J, KK and Pool), four of which have silenced MGMT. As expected, the MGMT-expressing parental cells were most drug-resistant and free of promoter methylation, whereas the MGMT-silenced immortal sublines were more drug-sensitive and promoter-methylated. Surprisingly, the sole MGMT-positive immortal subline, (AA) showed some promoter methylation although it was relatively drug-resistant; and an apparently MGMT-negative subline, (EE) showed unexpectedly low levels of methylation. We determined if these discrepancies were due to heterogeneity (cellular or allelic) and if this reflected transitional states between expressing and silenced phenotypes. Analysis of the methylation status of CpGs by genomic sequencing of cloned single copy DNA confirmed heterogeneity in both these sublines. With increasing cell culture passage, CpG methylation progressively increased with a concomitant trend to a completely MGMT-silenced phenotype in these sublines.

Journals

International Journal of Molecular Medicine

International Journal of Oncology

Molecular Medicine Reports

Oncology Reports

Experimental and Therapeutic Medicine

Oncology Letters

Biomedical Reports

Molecular and Clinical Oncology

World Academy of Sciences Journal

International Journal of Functional Nutrition

International Journal of Epigenetics

Medicine International

Heterogeneous methylation of the O6-methylguanine-DNA methyltransferase promoter in immortalized IMR90 cell lines

This article is mentioned in:

Abstract

Related Articles