Role of environmental factors in the etiology of hepatocellular carcinoma

Abstract

Chronic B and C virus hepatitis (HBV and HCV) are the most important risk factors in the development of hepatocellular carcinoma (HCC). About 40-50% of HCC is induced by these two chronic viral infections. Prevalence of HCC is slowly increasing in the United States and in Western-Europe, whereas alcohol consumption is gradually decreasing in the majority of these countries. However, the most important environmental risk factor for HCC is still the heavy long-term alcohol use. The risk of cirrhosis and HCC increases linearly, wherever ethanol intake is greater than 60 g/day for men and women. Aflatoxin, which contaminates grains, mostly in China and Africa, is a well-known mycotoxin. Since geographical distribution of aflatoxin as well as HBV overlaps with each other, they have a synergistic effect on inducing HCC. Cigarette smoking has also hepatocarcinogenic effect, which is significantly enhanced by the concomitant alcohol use or chronic viral hepatitis. Obesity, non-alcoholic fatty liver and steatohepatitis as well as diabetes mellitus together also form a significant risk for HCC, due to the gradually increasing number of patients. Insulin resistance and oxidative stress are the major pathogenetic mechanisms leading to hepatic cell injury in these patients. Oral contraceptive drugs may also play a role in the development of HCC. The long-term exposure to organic solvents is also a risk factor for HCC. Dietary antioxidants, selenium, statins and coffee drinking have protective effect against HCC.