The translation initiation factor, hu-Sui1 may be a target of hepatitis B X antigen in hepatocarcinogenesis

The role of hepatitis B virus X antigen in the development of hepatocellula r carcinoma was explored by stably transfecting HepG2 cells with an X antig en expression vector, and identifying the differences in gene expression th at distinguish X positive from X negative cells by subtractive PCR, One dif ferentially expressed gene, the human homolog of sdl (hu-sui1), encodes a t ranslation initiation factor whose expression was suppressed by X antigen i n HepG2 cells. Hu-Sui1 was also expressed in nontumor liver but not in tumo r cells from patients with hepatocellular carcinoma. Introduction of hu-sui 1 into HepG2 cells inhibited cell growth in culture, in soft agar, and part ially inhibited tumor formation in nude mice. Hence, the suppression of hu- sui1 by X antigen may result in the abrogation of negative growth regulatio n and contribute to the development of hepatocellular carcinoma.