Hepatitis C virus (HCV) causes a persistent infection, chronic hepatitis and hepatocellular carcinoma. HCV NS5A, one of non-structural proteins of HCV, was suggested to play a role in oncogenic transformation. Since the tumor suppressor p53 is important for preventing neoplastic transformation, we investigated the functional effects of HCV NS5A on p53. In vitro and in vivo coimmunoprecipitation and confocal microscopy were used to determine the interaction of NS5A and p53. HCV NS5A binds directly to p53 and colocalizes p53 in the perinuclear region. NS5A inhibits transcriptional transactivation by p53 in a dose-dependent manner by use of a reporter assay. Down regulation of endogenous p21/waf1 expression, which is activated by p53 in Hep3B cells, by NS5A was demonstrated by using FLAG-and FLAG-NS5A Hep3B stable cell lines. The effect of NS5A on p53-mediated apoptosis was determined by flow cytometry in both NS5A permanently and transiently transfected Hep3B cells with exogenous p53. The p53-induced apoptosis was abrogated by NS5A and the inhibition effect correlates well with the binding ability of NS5A to p53. In addition, HCV NS5A protein interacts with and colocalizes hTAF II 32, a component of TFIID and an essential coactivator of p53, in vivo. These results suggest that HCV NS5A interacts with and partially sequestrates p53 and hTAF II 32 in the cytoplasm and suppresses p53-mediated transcriptional transactivation and apoptosis during HCV infection, which may contribute to the hepatocarcinogenesis of HCV infection.

Preoperative serum VEGF is a significant independent predictor of tumor recurrence, DFS, and OS in patients with resectable HCC.

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Treatment of hepatocellular carcinoma (HCC) cells with butyrate can induce apoptosis irrespective of hepatitis B virus integration.No information is available, however, regarding the effect of butyrate on HCC in the presence of hepatitis C virus (HCV) because some HCV proteins can regulate cell survival. By gene transfer, we found that HCV core enhances but HCV NS5A antagonizes sodium phenylbutyrate (NaPB)-induced apoptosis in HCC cells, which is independent of p53. We then chose the p53-negative Hep3B HCC cell to investigate the mechanism of anti-apoptosis mediated by NS5A. In the NaPB-treated Hep3B cells without NS5A expression, induction of apoptosis was associated with Bax redistribution from the cytosol to the nucleus interior and subsequently, to a nuclear membrane-bound form. In the NS5A expressing Hep3B cells, NaPB treatment also triggered relocalization of both Bax and NS5A from the cytosol to the nucleus interior but Bax retained inside the nucleus and did not finally move to the nuclear membrane. Using double immunofluorescence and coimmunoprecipitation, we demonstrated that NS5A co-localizes and interacts with Bax in the nucleus. The HCV NS5A protein was further found to contain Bcl-2 homology domains (BH3, BH1 and BH2). Additional studies using deleted NS5A constructs were carried out to determine whether the BH2 domain or nuclear localization signal (NLS) in NS5A is required for interaction with Bax in the nucleus or inhibition of apoptosis. NS5A with deletion of both BH2 domain and NLS localized in the cytoplasm, dissociated with Bax, and lost anti-apoptosis activity during NaPB treatment. In contrast, NS5A with intact BH domains except NLS still bound directly to Bax in the perinuclear region or the nucleus, but showed less association with Bax in the nucleus and lower effect in apoptosis inhibition than full-length NS5A. These results suggest that HCV NS5A as a Bcl-2 homologue interacts with Bax to protect p53-negative HCC cells from NaPB-induced apoptosis. © 2003 Wiley-Liss, Inc. Key words: hepatocellular carcinoma; hepatitis C virus; NS5A; Bax; phenylbutyrateThe majority of patients with hepatocellular carcinoma (HCC) are associated with chronic hepatitis B virus (HBV, a DNA virus) or hepatitis C virus (HCV, a RNA virus) infection. 1 They usually present with inoperable or unresectable diseases accompanied by various degrees of liver function impairment. 2 The most currently active anti-cancer drugs are not only ineffective in inhibiting HCC but also toxic to the liver. 3 Identification of effective drugs with less hepatic toxicity for advanced HCC remains the challenging areas of study. Experimental studies have shown that sodium butyrate, a low toxic histone deacetylase inhibitor, can remodel chromatins to epigenetically activate or repress multiple genes to suppress growth and induce apoptosis in HCC cells in vitro and in vivo, which is irrespective of the status of p53 mutation and HBV integration. 4 No information is available so far, however, regarding the effect of butyrate on HCC in th...