Epigenetic Mechanisms of Drug Resistance: Drug-Induced DNA Hypermethylation and Drug Resistance

In a model system employing Chinese hamster V-79 cells, the DNA synthesis inhibitor 3'-azido-3'-deoxythymidine (BW A509U, AZT) was shown to induce genome-wide DNA hypermethylation, low-frequency silencing of thymidine kinase (TK; EC 2.7.1.21) gene expression, and resistance to AZT. Twenty-...

Full description

Saved in:

Bibliographic Details
Published in:	Proceedings of the National Academy of Sciences - PNAS Vol. 90; no. 7; pp. 2960 - 2964
Main Authors:	Nyce, Jonathan, Leonard, Sherry, Canupp, Dawn, Schulz, Stefan, Wong, So
Format:	Journal Article
Language:	English
Published:	Washington, DC National Academy of Sciences of the United States of America 01-04-1993 National Acad Sciences National Academy of Sciences
Subjects:	AIDS/HIV Animals Antibiotics. Antiinfectious agents. Antiparasitic agents Antiviral agents Antivirals Biological and medical sciences Cell culture techniques Cell Line Cell lines Chromatography, High Pressure Liquid Cricetinae Cricetulus Deoxyribonucleic acid DNA DNA - genetics DNA - metabolism DNA Replication - drug effects Drug Resistance - genetics Drug therapy Floxuridine - pharmacology Gene Expression Regulation, Enzymologic - drug effects Genes Genetic mutation Genetics Genome HIV 1 Kinetics Medical research Medical sciences Messenger RNA Methylation Nucleotides Nucleotides - isolation & purification Nucleotides - metabolism Pharmacology. Drug treatments Thymidine Kinase - genetics Zidovudine - metabolism Zidovudine - pharmacology Thymidine kinase Transcription Enzyme Lung Rodentia Repression In vitro Mechanism Vertebrata Mammalia Sensitivity resistance Mutagenesis Animal DNA Epigenetics Antiviral Methylation Hamster
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	In a model system employing Chinese hamster V-79 cells, the DNA synthesis inhibitor 3'-azido-3'-deoxythymidine (BW A509U, AZT) was shown to induce genome-wide DNA hypermethylation, low-frequency silencing of thymidine kinase (TK; EC 2.7.1.21) gene expression, and resistance to AZT. Twenty-four hours of exposure of V-79 cells to 150 μM AZT led to >2-fold enhancement of genomic 5-methylcytosine levels and produced TK-epimutants at a rate ≈43-fold above background. Such AZT-induced TK-epimutants were shown to be severely reduced in their capacity to activate AZT to its proximate antiviral form, AZT 5'-monophosphate, as compared with the TK+parental cell line from which they were derived. TK-clones isolated under these conditions were shown to be 9- to 24-fold more resistant to the cytotoxic effects of AZT than the parental TK+cell line and showed collateral resistance to 5-fluoro-2'-deoxyuridine. Three of four TK-epimutants could be reactivated at very high frequency (8-73%) to the TK+AZT-sensitive phenotype by 24 hr of exposure to the demethylating agent 5-azadeoxycytidine (5-azadC), implying that drug-induced DNA hypermethylation, rather than classical mutation, was involved in the original gene-silencing event in these three clones. These 5-azadC-induced TK+revertants concomitantly regained the ability to metabolize AZT to its 5'-monophosphate. RNA slot blot analyses indicated that the four AZT-induced TK-clones expressed 8.9%, 15.6%, 17.8%, and 11.1% of the parental level of TK mRNA. The three clones that were reactivatable by 5-azadC showed reexpression of TK mRNA to levels 84.4%, 51.1%, and 80.0% that of the TK+parental cell line. These experiments show that one potential mechanism of drug resistance involves drug-induced DNA hypermethylation and resulting transcriptional inactivation of cellular genes whose products are required for drug activation.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0027-8424 1091-6490
DOI:	10.1073/pnas.90.7.2960