Hepatocellular carcinoma (HCC) is among the most frequent malignancies worl
dwide. Hepatitis viruses, such as the hepatitis B virus (HBV) and hepatitis
C virus (HCV) are undoubtedly listed in the etiology of HCC. Studies show
that, in the near future, viral hepatitis will carry increasing weight in t
he etiology of HCC. This review briefly discusses the known carcinogenic ef
fects of HBV and HCV in the light of experimental and human studies. The da
ta show that viral proteins may directly interfere with gene products respo
nsible for cell proliferation and cell growth. Many other signal transducti
on cascades may be affected as well. Direct integration of HBV viral sequen
ces into the host genome increases the genomic instability. The genomic inb
alance allows the development and survival of malignant clones bearing defe
cted genomic information. HBV and HCV infection induces indirect and direct
mechanisms through cellular damage, increased regeneration and cell prolif
eration, therefore enhancing the development of HCC. (C) 2001 Elsevier Scie
nce Ltd. All rights reserved.