Chemopreventive effect of vanadium in a rodent model of chemical hepatocarcinogenesis: reflections in oxidative DNA damage, energy-dispersive X-ray fluorescence profile and metallothionein expression

In the present study, we investigated the antitumour efficacy of vanadium in a defined rodent model of experimental hepatocarcinogenesis. Hepatic preneoplasia was induced in male Sprague-Dawley rats with a single, necrogenic, intraperitoneal injection of diethylnitrosamine (DEN) (200 mg/kg body weight) followed by promotion with phenobarbital (PB). The levels of modified DNA bases 8-hydroxy-2'-deoxyguanosine (8-OHdG), a potential marker involved in the initiation of carcinogenesis, were measured by high-performance liquid chromatography, whereas tissue trace element status and expression of metallothionein (MT), a Cu-Zn metalloprotein associated with neoplastic cell growth and subsequent development of premalignant phenotype of the cell, were studied by energy-dispersive X-ray fluorescence spectrometry and enzyme-coupled immunohistochemistry, respectively. There was a significant and steady elevation of modified bases (8-OHdG) along with substantial increase in MT immunoexpression and disturbance in trace element homeostasis following DEN exposure. Supplementation of vanadium at a dose of 0.5 ppm for four consecutive weeks strictly abated the formation of 8-OHdG (P < 0.0001; 81.28%) in preneoplastic rat liver. In a long-term DEN plus PB regimen, vanadium was able to limit in situ MT expression with a concomitant decrease in MT immunoreactivity (P < 0.05). Furthermore, vanadium treatment throughout the study restored hepatic levels of essential trace elements and decreased nodular incidence (58.34%) and nodule multiplicity (P < 0.001; 66.89%) in rats treated with DEN plus PB. Taken together, the study provides evidence in support of the chemopreventive potential of vanadium in limiting neoplastic transformation during the preneoplastic stages of hepatocarcinogenesis in rats.