Abstract 1886: Selenium prevents specific iron-mediated hepatic cellular changes associated with antioxidant defense and proliferation
Authors: Emily McDevitt, Mi Sun Moon, Susan Kocher, Jacek Krzeminski, Arun Das, Shantu Amin, Karam El-Bayoumy, Harriet C. Isom
Journal: Cancer Research (2010)

Abstract Hepatocellular carcinoma (HCC), one of the most common causes of cancer death, is on the rise in the United States. HCC is a slow process occurring in the setting of liver cell injury that can be induced by oxidative stress leading to DNA damage and resulting in mutations that accumulate with time. Although many risk factors for HCC are known, the molecular pathogenesis of HCC is not well understood. In many chronic liver diseases that culminate in HCC, including hereditary hemochromatosis and chronic hepatitis C, excess iron deposition is observed. However, little is known about the effects of iron overload in the liver on cellular pathways. We generated a mouse model of chronic hepatic iron overload of liver by supplementing the diet with the iron donor 3,5,5-trimethyl-hexanoyl ferrocene (TMHF). Histological examination of livers from mice fed a TMHF diet for as long as 9 weeks showed no signs of inflammation or necrosis. Hepatocytes underwent expected physiological responses to iron in that ferritin levels were increased and hemosiderin accumulated with time. TMHF treated mice developed hepatomegaly and had elevated hepatic cyclin D1 and PCNA expression. TMHF treatment also resulted in a time-dependent decrease in hepatic levels of the antioxidant protein glutathione peroxidase 1 (GPX-1) but had no effect on Cu/Zn superoxide dismutase (SOD) or Mn-SOD. TMHF treatment also led to activation of β-catenin, induction of matrilysin (MMP7), and increased levels of cyp2b10. In this study, we tested the ability of selenium to specifically restore molecular and cellular changes induced by chronic hepatic iron overload. Mice were fed a diet supplemented with or without TMHF in the presence or absence of selenium for periods of time ranging from one to nine weeks. Selenium was provided as sodium selenite (15 ppm) or the synthetic organoselenium 1,4-phenylenebis (methylene) selenocyanate, p-XSC (15 ppm). Treatment of control mice, not fed TMHF, with selenium had no effect on the measured end points. As expected, supplementation with selenium in either form had no effect on TMHF induced ferritin expression or hemosiderin accumulation. However, dietary supplementation with selenium, simultaneously with TMHF treatment, markedly reduced TMHF mediated induction of cyclin D1 and PCNA expression and prevented iron mediated decrease in GPX-1 levels. Selenium had no effect on iron-induced hepatomegaly, activation of β-catenin, induction of MMP7, or increased cyp2b10. We conclude that (1) selenium restores the levels of the antioxidant defense enzyme GPX-1 and reduces iron induced stimulation of proliferation in a mouse model of hepatic iron overload; (2) the effects of selenium on these pathways occur by a mechanism other than simply reduction in hepatic iron levels; and (3) the effects of selenium are specific to some and not all iron-mediated changes in hepatic cellular signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1886.