Sodium arsenite administration via drinking water increases genome-wide and Ha-ras DNA hypomethylation in methyl-deficient C57BL/6J mice

• Published in: Carcinogenesis (New York) Vol. 23; no. 5; pp. 777 - 785
• Main Authors: Okoji, R.S., Yu, R.C., Maronpot, R.R., Froines, J.R.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.05.2002; Oxford Publishing Limited (England)
• Subjects: Animals; Arsenites - administration & dosage; Arsenites - pharmacology; Base Sequence; Biological and medical sciences; Carcinogenesis, carcinogens and anticarcinogens; Chemical agents; DNA Methylation - drug effects; DNA Primers; Genes, ras; Genome; Male; MDD; Medical sciences; methyl-deficient diet; methyl-sufficient diet; Mice; Mice, Inbred C57BL; MSD; S-adenosyl-methionine; SAM; Sodium Compounds - administration & dosage; Sodium Compounds - pharmacology; Tumors; Water Supply; Deficient diet; Arsenic; Sodium Arsenites; Nucleotide sequence; Transcription promoter; Toxicity; Rodentia; Oral administration; Carcinogen; Gene silencing; Vertebrata; Mammalia; Mouse; GC rich sequence; Animal; DNA; Methyl group; Onc gene; Methylation
• ISSN: 0143-3334; 1460-2180; 1460-2180
• DOI: 10.1093/carcin/23.5.777

Arsenic is an established human carcinogen. Deficiencies in available animal models have inhibited a detailed analysis of the mechanism of arsenic induced cancer. This study sought to determine the role of a methyl-deficient diet in combination with sodium arsenite on the genomic methylation status and Ha-ras methylation status of C57BL/6J male mice hepatic DNA. Mice were administered arsenic as sodium arsenite via drinking water at 0, 2.6, 4.3, 9.5 or 14.6 mg sodium arsenite/kg/day. Administration occurred 7 days a week for 130 days. Dose-related effects on the liver were evident in mice administered arsenic and methyl-deficient diets. Most prominent were observations of steatosis and microgranulomas. Sodium arsenite increased genomic hypomethylation in a dose dependent manner and methyl-deficiency and sodium arsenite reduced the frequency of methylation at several cytosine sites within the promoter region of the oncogenic gene, Ha-ras. Methylation changes were prominent in a 500 bp non-CpG island-like region of the Ha-ras promoter and less prominent in a 525 bp CpG island-like region. DNA methylation plays an important role in the physiological expression of many genes including Ha-ras. Significantly reduced methylation at a key regulatory region of Ha-ras in the mouse liver may have relevance to understanding arsenic-induced perturbations in the methylation patterns of cellular growth genes involved in the formation of tumors. These findings highlight the effect of sodium arsenite on inherent methylation processes within the hepatic cell.