. The X gene-encoded protein (HBx), consisting of 154 amino acid residues with a molecular weight of 17 kd, is detected after overexpression in some eukaryotic expression systems 3-6 and localized mainly within the cytoplasm. 3,6 The function of HBx is largely obscure, but it has been shown to transactivate many viral and cellular genes, including some transcriptional factors (reviewed by Caselmann, 1 Hildt et al., 2 and Rossner 7 ) and growth-regulating genes such as ras, 8,9 c-myc, 10 c-fos, 10,11 c-jun, 12 and the gene coding for the epidermal growth factor receptor. 13 Recent studies indicate that HBx is also associated with elevated expression of insulin-like growth factor II 14 and insulin-like growth factor I receptor 15 in hepatocytes and hepatocellular carcinoma (HCC). HBx has been reported to be capable of binding p53, 16-22 the TATA-binding protein 23 and a cellular protein associated with DNA repair. 24 These findings indicate a possible role of HBx in HBV replication, in accordance with the well-established mechanism of replication of the woodchuck hepatitis virus, 25 as well as the potential to disturb growth control and DNA repair in the host cells. Malignant transformation has been observed in some X gene-transfected cell lines 1,26,27 and in an X gene-transgenic mouse model. 28,29 The X gene is, therefore, considered to play a decisive role in neoplastic transformation of hepatocytes in HBV-infected liver. 29,30 Transactivation of the growthregulating genes and functional inactivation of p53 by HBx have been proposed as alternative mechanisms. 1,2,7,16,21,30 Expression of the X gene in liver tissue has been established in woodchucks carrying the woodchuck hepatitis virus. 31,32 However, only indirect evidence for the expression of X gene in HBV-infected human liver has so far been obtained. RNA, containing components of the X region, has been demonstrated by reverse-transcription polymerase chain reaction. 33,34 Circulating antibodies reactive to recombinant HBx, [35][36][37][38][39][40][41][42] and HBx-specific cellular immune response, 43 may be detected in patients with chronic hepatitis B. By means of antibodies against recombinant HBx or its fragments, some immunoreactivity has been demonstrated in HBV-infected livers, 14,39,[44][45][46][47][48][49][50][51] with three polypeptides identified as the HBx antigen in HCC-bearing livers of HBV-infected Chinese patients. 16 While interactions between HBx and the p53 protein are documented, 17-22,52 a dissenting view was expressed recently by Henkler et al., 53 who did not show either HBx expression in, or coprecipitation of HBx and p53 protein from, HCC specimens of 31 Chinese patients with chronic HBV infection. These conflicting results may at least partly be caused by the application of different anti-HBx antibodies. In the present study, 11 anti-HBx antibodies prepared in five laboratories were therefore characterized comparatively. With Abbreviations: HBV, hepatitis B virus; HBx, hepatitis B virus X protein; HCC, hepatocellular carcinoma; PB...

No abstract

Foci of altered hepatocytes (FAH) represent preneoplastic lesions, as shown in various animal models of hepatocarcinogenesis, but their significance in the human liver has not been established. The cellular composition, size distribution and proliferation kinetics of FAH in 163 explanted and resected human livers with or without hepatocellular carcinoma (HCC) and their possible association with small-cell change of hepatocytes (SCC) were therefore studied. FAH, including glycogen-storing foci, were found in 84 of 111 cirrhotic livers, demonstrating higher incidences in cases with (29/32) than in those without HCC (55/79). FAH were observed more frequently in HCC-free cirrhosis associated with hepatitis B or C virus or chronic alcoholic abuse (high-risk group) (37/47) than in that due to other causes (low-risk group) (12/21). MCF, predominant in cirrhotic livers of the high-risk group, were more proliferative, larger and more often involved in formation of nodules of altered hepatocytes (39.3%) than were GSF (8.5%). The results suggest that the FAH are preneoplastic lesions, MCF being more advanced than GSF. Oncocytic and amphophilic cell foci were also observed, but their significance remains to be clarified. Two types of SCC, namely diffuse and intrafocal SCC, were identified, but only intrafocal SCC was found to be related to increased proliferative activity and more frequent nodular transformation of the FAH involved, suggesting a close association with progression from FAH to HCC.