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Abstract: ZBP-89, a Krüppel-type zinc-finger transcription factor that binds to GC-rich sequences, is involved in the regulation of cell growth and cell death. It maps to chromosome 3q21 and is composed of 794 residues. Having bifunctional regulatory domains, ZBP-89 may function as a transcriptional activator or repressor of variety of genes such as p16 and vimentin. ZBP-89 arrests cell proliferation through its interactions with p53 and p21waf1. It is able to stabilize p53 through directly binding and enhance p53 transcriptional activity by retaining it in the nucleus. In addition, ZBP-89 potentiates in butyrate-induced endogenous p21waf1 up-regulation. ZBP-89 is usually over-expressed in human cancer cells, where it can efficiently induce apoptosis through p53-dependent and -independent mechanisms. Moreover, ZBP-89 is capable of enhancing killing effects of several anti-cancer drugs. Therefore, ZBP-89 may be served as a potential target in cancer therapy. [Copyright &y& Elsevier]

Abstract: The oncogenic hepatitis B virus X protein (HBx) and cyclooxygenase (COX)-2 are highly co-expressed in chronic hepatitis, cirrhosis and well-differentiated hepatocellular carcinoma (HCC). Although HBx is shown to activate COX-2, the functional consequences of this interaction in hepatocarcinogenesis remain unknown. Using an engineered hepatoma cell system in which the expression of wild-type p53 can be chemically modulated, we show here that COX-2 mediates HBx actions in opposing p53. Enforced expression of HBx sequestrates p53 in the cytoplasm and significantly abolishes p53-induced apoptosis. The anti-apoptotic Mcl-1 protein is suppressed by p53 but reactivated by HBx. The abrogation of apoptosis is completely reversed by specific COX-2 inhibition, suggesting that HBx blocks p53-induced apoptosis via activation of COX-2/PGE2 pathway. We further show that COX-2 inhibition blocks HBx reactivation of Mcl-1, linking this protein to the anti-apoptotic function of COX-2. These results demonstrate that COX-2 is an important survival factor mediating the oncogenic actions of HBx. Over-expression of HBx and COX-2 may provide a selective clonal advantage for preneoplastic or neoplastic hepatocytes and contribute to the initiation and progression of HCC. [Copyright &y& Elsevier]

Abstract: Zinc-binding protein-89 regulates Bak to facilitate apoptosis in cancer cells. This study examined if zinc-binding protein-89 regulates Bak through an epigenetic mechanism in hepatocellular carcinoma. We first demonstrated that the expression of Bak was reduced but the levels of deoxyribonucleic acid methyltransferase 1 and histone deacetylase 3 were increased in hepatocellular carcinoma cancer tissues compared to the corresponding non-cancer tissues. Moreover, there was a negative correlation between Bak expression and deoxyribonucleic acid methyltransferase 1 levels in hepatocellular carcinoma. Administration of zinc-binding protein-89 downregulated histone deacetylase 3 expression and suppressed the activities of histone deacetylase and deoxyribonucleic acid methyltransferase, which led to maintenance of histone acetylation status, inhibited the binding of methyl-CpG-binding protein 2 to genomic deoxyribonucleic acid and demethylated CpG islands in the Bak promoter in hepatocellular carcinoma cells. Using the xenograft mouse tumor model, we demonstrated that zinc-binding protein-89 or inhibitors of either epigenetic enzymes could stimulate Bak expression, induce apoptosis, and arrest tumor growth and that the maximal effort was achieved when zinc-binding protein-89 and the enzyme inhibitors were used in combination. Conclusively, zinc-binding protein-89 upregulates the expression of Bak by targeting multiple components of the epigenetic pathway in hepatocellular carcinoma. [Copyright &y& Elsevier]

Abstract: The expression of bone morphogenic protein 4 (BMP4), a new pro-inflammatory marker, is increased by disturbed flow in endothelial cells (ECs). BMP4 stimulates production of reactive oxygen species (ROS) and causes endothelial cell dysfunction. The present study examined BMP4-induced apoptosis in ECs and isolated arteries from rat, mouse, and human, and the signaling pathways mediating BMP4-induced apoptosis. Apoptosis was assessed by flow cytometry to detect Annexin-V positive cells, and terminal deoxynucleotidyl transferase dUTP nick end (TUNEL) labeling. The superoxide production was measured by dihydroethidium fluorescence. BMP4 induced EC apoptosis in human mesenteric arteries, mouse aortic endothelium, rat primary ECs, and human ECs. BMP4-induced EC apoptosis was mediated through ROS production by activation of NADPH oxidase, which led to cleaved caspase-3 expression. BMP4 also induced sequential activation of p38 MAPK and JNK which was upstream of caspase 3 activation. Knockdown of BMP receptor 1A by lentiviral shRNA or NOX4 siRNA transfection inhibited BMP4-induced ROS production, p38 and JNK phosphorylation, and caspase-3 activation in ECs. JNK siRNA inhibited BMP4-induced JNK phosphorylation and caspase-3 activation. The present study delineates that BMP4 causes EC apoptosis through activation of caspase-3 in a ROS/p38MAPK/JNK-dependent signaling cascade. [Copyright &y& Elsevier]

Abstract: ZBP-89 can enhance tumor cells to death stimuli. However, the molecular mechanism leading to the inhibitory effect of ZBP-89 is unknown. In this study, 4 liver cell lines were used to screen for the target of ZBP-89 on cell death pathway. The identified Bak was further analyzed for its role in ZBP-89-mediated apoptosis. The result showed that ZBP-89 significantly and time-dependently induced apoptosis. It significantly upregulated the level of pro-apoptotic Bak. ZBP-89 targeted a region between -457 and -407 of human Bak promoter to stimulate Bak expression based on the findings of Bak promoter luciferase report gene assay and electrophoretic mobility shift assay. ZBP-89-induced Bak increase and ZBP-89-mediated apoptosis were markedly suppressed by Bak siRNA, confirming that Bak was specifically targeted by ZBP-89 to facilitate apoptosis. In conclusion, this study demonstrated that ZBP-89 significantly induced apoptosis of HCC cells via promoting Bak level. [ABSTRACT FROM AUTHOR]

Abstract: tBid is a pro-apoptotic molecule. Apoptosis inducers usually act in a cell cycle-specific fashion. The aim of this study was to elucidate whether effect of tBid on hepatocellular carcinoma (HCC) Hep3B cells was cell cycle phase specific. We synchronized Hep3B cells at G0/G1, S or G2/M phases by chemicals or flow sorting and tested the susceptibility of the cells to recombinant tBid. Cell viability was measured by MTT assay and apoptosis by TUNEL. The results revealed that tBid primarily targeted the cells at G0/G1 phase of cell cycle, and it also increased the cells at the G2/M phase. 5-Fluorouracil (5-FU), on the other hand, arrested Hep3B cells at the G0/G1 phase, but significantly reduced cells at G2/M phase. The levels of cell cycle-related proteins and caspases were altered in line with the change in the cell cycle. The combination of tBid with 5-FU caused more cells to be apoptotic than either agent alone. Therefore, the complementary effect of tBid and 5-FU on different phases of the cell cycle may explain their synergistric effect on Hep3B cells. The elucidation of the phase-specific effect of tBid points to a possible therapeutic option that combines different phase specific agents to overcome resistance of HCC. [ABSTRACT FROM AUTHOR]