Suppression of Early Stages of Neoplastic Transformation in a Two-Stage Chemical Hepatocarcinogenesis Model: Supplementation of Vanadium, a Dietary Micronutrient, Limits Cell Proliferation and Inhibits the Formations of 8-Hydroxy-2′-deoxyguanosines and DNA Strand-Breaks in the Liver of Sprague-Dawley Rats

Abstract

Previous studies from our laboratory have demonstrated the potential anticarcinogenicity of vanadium, a dietary micronutrient in rat liver, colon, and mammary carcinogenesis models in vivo. In this paper, we have investigated further the antihepatocarcinogenic role of this essential trace element by studying several biomarkers of chemical carcinogenesis with special reference to cell proliferation and oxidative DNA damage. Hepatocarcinogenesis was induced in male Sprague-Dawley rats by chronic feeding of 2-acetylaminofluorene (2-AAF) at a dose of 0.05% in basal diet daily for 5 days a week. Vanadium in the form of ammonium metavanadate (0.5 ppm equivalent to 4.27 μ mol/l) was supplemented ad lib to the rats. Continuous vanadium administration reduced relative liver weight, nodular incidence (79.99%), total number and multiplicity (P < 0.001; 68.17%) along with improvement in hepatocellular architecture when compared to carcinogen control. Vanadium treatment further restored hepatic uridine diphosphate (UDP)-glucuronosyl transferase and UDP-glucose dehydrogenase activities, inhibited lipid peroxidation, and prevented the development of glycogen-storage preneoplastic foci (P < 0.01; 63.29%) in an initiation-promotion model. Long-term vanadium treatment also reduced BrdU-labelling index (P < 0.02) and inhibited cell proliferation during hepatocellular preneoplasia. Finally, short-term vanadium exposure abated the formations of 8-hydroxy-2′-deoxyguanosines (P < 0.001; 56.27%), length:width of DNA mass (P < 0.01), and the mean frequency of tailed DNA (P < 0.001) in preneoplastic rat liver. The study indicates the potential role of vanadium in suppressing cell proliferation and in preventing early DNA damage in vivo. Vanadium is chemopreventive against the early stages of 2-AAF-induced hepatocarcinogenesis in rats.

Acknowledgments and Notes

Dr. Tridib Chakraborty is highly indebted to the Council of Scientific and Industrial Research (CSIR), Government of India for financial assistance. A part of the total cost for this work was defrayed from the Department of Science and Technology (Project No. P-1/RS/34/2001) and CSIR [Grant No. 9/96(470)2K5-EMR-I] Projects, Government of India; T. Chakraborty is a Post-doctoral Fellow (Direct) in the CSIR Project]. Generous help from Dr. P. K. Sen, Department of Mathematics, Jadavpur University, Kolkata for his excellent guidance in statistical interpretation of the data is truly acknowledged.

Notes

a: Values represent mean ± SE. Abbreviation is as follows: 2-AAF, 2-acetylaminofluorene.

b: Liver weight (g)/body weight (g) × 100.

c:P < 0.001 when compared to normal control (Group a).

d: P < 0.001.

e: P < 0.01 when compared to 2-AAF control (Group A).

a: Values represent mean ± SE. Abbreviation is as follows: 2-AAF, 2-acetylaminofluorene.

b: Average number of nodules/nodule-bearing liver.

c: P < 0.001.

d: P < 0.05 when compared with 2-AAF control (Group A).

a: Values represent mean ± SE. Abbreviations are as follows: UDP, uridine diphosphate; UDPGT, UDP-glucuronosyl transferase; UDPGDH, UDP-glucose dehydrogenase; LPO, lipid peroxidation; 2-AAF, 2-acetylaminofluorene; MDA, malondialdehyde.

b: P < 0.001.

c: P < 0.0001 when compared to normal control (Group a).

d: P < 0.01.

e: P < 0.001 when compared to 2-AAF control (Group A).

f: P < 0.05.

a: Values represent mean ± SE. Abbreviation is as follows: 2-AAF, 2-acetylaminofluorene.

b: P < 0.01 when compared to 2-AAF control (Group A).

a: Values represent mean ± SE (n = 15). Abbreviations are as follows: 2-AAF, 2-acetylaminofluorene; 8-OHdG, 8-Hydroxy-2′-deoxyguanosine.

b: P < 0.0001 when compared to normal control (Group A).

c: P < 0.001 when compared to 2-AAF control (Group C).