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Vanadium limits the expression of proliferating cell nuclear antigen and inhibits early DNA damage during diethylnitrosamine‐induced hepatocellular preneoplasia in rats

Previous studies from our laboratory have shown that vanadium stabilizes xenobiotic metabolizing enzymes and antioxidant status and suppresses DNA‐protein crosslinks during chemically‐induced hepatocarcinogenesis in rats. In the present study, we have further investigated the in vivo antitumor potential of this micronutrient by determining the effect of 0.5 ppm vanadium in drinking water on biomarkers for the early stages of hepatocarcinogenesis; the biomarkers included γ‐glutamyl transpeptidase (GGT)‐positive foci and glycogen‐storage foci, in situ expression of proliferating cell nuclear antigen (PCNA), and genotoxic DNA damage assessed by the alkaline Comet assay. Histomorphometry also was assessed during the study. Hepatocarcinogenesis was induced by treating 4‐week‐old male Sprague‐Dawley rats with a single, necrogenic, intraperitoneal (i.p.) injection of 200 mg/kg body weight diethylnitrosamine (DEN). Compared to the carcinogen control, vanadium administration over the 32 weeks of the experiment reduced the relative liver weight by 30%, the incidence of nodules by 69.34%, the total number and multiplicity of nodules by 80.77%, and remodeled the hepatocellular premalignant architecture towards a normal phenotype. Moreover, long‐term vanadium treatment reduced the development of GGT foci by 76.2% (P < 0.001), decreased periodic acid‐Schiff's reactivity by 59.49% (P < 0.01), and decreased PCNA expression, with the concomitant reduction in PCNA immunolabeling index by 93.36% (P < 0.001). Finally, vanadium inhibited early DNA damage (DNA strand‐breaks) in DEN‐treated rat hepatocytes as expressed in the Comet assay by a 60.04% reduction in the length:width value of DNA mass (P < 0.01) and a 51.54% reduction in the tail length of the DNA comets (P < 0.001). Our results indicate that continuous supplementation with 0.5 ppm vanadium suppresses hepatocellular neoplastic transformation in rats. Environ. Mol. Mutagen., 2006. © 2006 Wiley‐Liss, Inc.