Differential effect of acetyltransferase expression on the genotoxicity of heterocyclic amines in CHO cells

Rebekah W. Wu, James D. Tucker, Karen J. Sorensen, Larry H. Thompson, James S. Felton

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

We earlier developed the Chinese hamster ovary UV5P3 cell line that expresses cytochrome P4501A2 and lacks nucleotide excision repair for studying metabolism and mutagenicity of heterocyclic amines. The Chinese hamster ovary UV5P3 cells are approximately 50-fold more sensitive to the cooked food mutagen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) than 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), another genotoxic compound found in cooked food, with respect to cytotoxicity and mutation induction at the adenine phosphoribosyltransferase (aprt) locus. To test the hypothesis that the important missing activity in our CHO system for IQ genotoxicity was acetyltransferase, we transfected the UV5P3 cells with cDNA plasmids of either the human NAT2 N-acetyltransferase gene or a bacterial O-acetyltransferase gene. Functionally transformed clones were determined by the differential cytotoxicity assay using IQ, and confirmed by measuring the enzyme activity with isoniazid as substrate. Two clones designated 5P3NAT2 and 5P3YG (expressing human. and bacterial transferases, respectively) were characterized. Both cell lines were sensitive to killing by IQ at concentrations as low as 4 ng/ml. Based on the D37 value, the dose that reduced the survival to 37% relative to untreated controls, the acetyltransferase expressing lines showed ~ 1000-fold increase in sensitivity to the killing effects of IQ over the parental UV5P3 cell line. The same dramatic change in sensitivity was also seen in mutation response at the aprt locus and with chromosomal aberrations and sister chromatid exchanges. In contrast, these cell lines showed cytotoxicity to PhIP similar to that of the parental line UV5P3. These results suggest that PhIP does not require acetyltransferase for metabolic activation leading to genotoxicity in these cells. These new cell lines constitute a sensitive cell system for assessing genotoxicity of compounds requiring metabolic activation by both P450IA2 and acetyltransferase, as well as for studying the molecular processes by which DNA damage can lend to mutation and cancer.

Original languageEnglish (US)
Pages (from-to)93-103
Number of pages11
JournalMutation Research - Genetic Toxicology and Environmental Mutagenesis
Volume390
Issue number1-2
DOIs
StatePublished - Apr 24 1997
Externally publishedYes

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Keywords

  • 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine
  • 2-Amino-3-methylimidazo[4,5-f]quinoline
  • Acetyltransferase
  • Chinese hamster ovary
  • Cytogenetic testing
  • Food mutagen
  • Mutagenesis

ASJC Scopus subject areas

  • Health, Toxicology and Mutagenesis
  • Genetics

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