Previous studies showed that
2-butoxyethanol increased liver
tumors in B6C3F1 mice following chronic exposure. While the mechanism of 2-butoxyethanol-induced liver carcinogenicity has not been defined,
2-butoxyethanol has been shown to induce
hemolysis in rodents via
2-butoxyacetic acid, the major metabolite of
2-butoxyethanol. This toxic effect, coupled with the observation that continued treatment with
2-butoxyethanol results in
hemosiderin deposition in the liver, has led to our hypothesis that liver carcinogenicity by 2-butoxyethnaol is mediated via oxidative stress (
iron catalyzed) and Kupffer cell activation. The present study used Syrian Hamster Embryo (SHE) cell transformation, a surrogate in vitro model for
carcinogenesis in vivo, to examine whether
2-butoxyethanol,
2-butoxyacetic acid, or
iron (
ferrous sulfate) produced cell transformation. SHE cells were treated with either
2-butoxyethanol (0.5-20 mM),
2-butoxyacetic acid (0.5-20 mM), or
ferrous sulfate (0.5-75 microg/ml) for 7 days.
2-Butoxyethanol and
2-butoxyacetic acid did not induce cellular transformation. In contrast, treatment with
ferrous sulfate (2.5 and 5.0 microg/ml) increased morphological transformation. Cotreatment of
ferrous sulfate with the
antioxidants alpha-tocopherol (
vitamin E) or (-)-epigallocatechin-3-gallate (EGCG) prevented
ferrous sulfate-induced transformation, suggesting the involvement of oxidative stress in SHE cell transformation. The level of oxidative DNA damage (OH8dG) increased following
ferrous sulfate treatment in SHE cells; additionally, using single cell gel electrophoresis (comet assay),
ferrous sulfate treatment produced an increase in DNA damage. Both DNA lesions were decreased by cotreatment of
ferrous sulfate with
antioxidants. These data support our proposal that
iron, produced indirectly through
hemolysis, and not
2-butoxyethanol or its metabolite
2-butoxyacetic acid, is responsible for the observed carcinogenicity of
2-butoxyethanol.