Oxidative stress to DNA is recognized as a mechanism underlying carcinogenic effects of some environmental agents. Here, we hypothesized that dimethylarsinic acid (DMAV), an organic metabolite of inorganic arsenic in humans, might exert carcinogenic potential in a mouse line carrying a mutant Mmh allele of the Mmh/OGG1 gene encoding the enzyme 8-hydroxyguanine DNA glycosylase 1 (OGG1). Ogg1 mutant and wild type mice were treated with DMAV in their drinking water at a dose of 200 ppm for up to 72 weeks. All DMAV-treated Ogg1-/-animals developed tumors, with a tendency for lower total incidences in the Ogg1+/+ cases. Lung tumors in particular were induced as compared to the lack in non-carcinogen controls and were significantly more frequent in the homozygotes. At week 4, the levels of DNA 8-OH-dG and cell proliferation were significantly elevated in the lungs of non-treated Ogg1-/- as compared to Ogg1+/+ mice and were strongly enhanced by DMAV treatment. Marked induction of Pola1, Cyp7b1, Ndfua3, Mmp13 and other genes specific for cell proliferation, cell signaling and xenobiotic metabolism in the lung of DMAV-treated Ogg1-/- mice was found. Electron microscopic examination revealed the growth of microvilli, with increased numbers of mitochondria only in lungs and lung tumors of DMAV-exposed Ogg1-/- mice. Therefore, we strongly suggest that DMAV exerts carcinogenicity in the lungs of Ogg1-/- mutant mice, with a possible role for persistent accumulation of DNA oxidative adducts.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA