Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transforming growth factor-beta (TGF-beta), found at the site of most tumors, has been recognized as one of the mechanisms involved in tumor immunological escape. To evaluate its impact on adoptive immunotherapy against cancer, we examined the susceptibility of tumor-specific T cells to TGF-beta in the setting of these T cells being prepared for adoptive transfer. Hepatitis B virus (HBV)-specific CD4(+) T cells were ex vivo generated by activating with HBV-transfected dendritic cells and selecting with antibodies to CD25 activation molecules, and then expanded with antibodies to CD3/CD28. These T cells expressed higher levels of the type II TGF-beta receptor than nai;ve T cells and exhibited enhanced apoptosis when exposed to TGF-beta. The underlying apoptotic pathway was linked to the dissipation of the mitochondrial inner membrane potential and activation of caspase-9. The absence of caspase-8 activity in TGF-beta-treated T cells suggests that the death receptor system may not be involved in this type of apoptosis. Interleukin-2 (IL-2), which is concomitantly administered with tumor-specific T cells in adoptive immunotherapy, was unable to protect HBV-specific CD4(+) T cells from the pro-apoptotic effect of TGF-beta when added simultaneously with TGF-beta. Interesting, IL-2-pretreated T cells displayed the type II TGF-beta receptor at lower levels and were more resistant to TGF-beta. Together, our findings indicate that the effectiveness of adoptive cancer immunotherapy may be impaired by tumor-derived TGF-beta and appropriate manipulation of exogenous IL-2 might overcome this hurdle.
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PMID:Transforming growth factor-beta induces apoptosis in antigen-specific CD4+ T cells prepared for adoptive immunotherapy. 1260 Jul 43

Despite its implication in the progression of hepatitis B virus (HBV)-associated liver disease, the pro-apoptotic function of HBx protein remains poorly understood. We show that the expression of HBx leads to hyperactivation of caspase-8 and caspase-3 upon treatment with tumor necrosis factor-alpha (TNF-alpha) or anti-Fas antibody, and this activation is correlated with the sensitivity to apoptosis. We demonstrate cytoplasmic co-localization and direct interaction between HBx and the cellular FLICE inhibitory protein (c-FLIP), a key regulator of the death-inducing signaling complex (DISC). Deletion analysis shows that the death effector domain 1 (DED1) of c-FLIP is important for the observed interaction. Overexpression of c-FLIP rescued the cells from HBx-mediated apoptosis, with both the full-length HBV genome and HBx expression vectors. Moreover, c-FLIP and caspase-8 inhibitor considerably protected cells from HBx-mediated apoptosis. These data suggest that HBx abrogates the apoptosis-inhibitory function of c-FLIP and renders the cell hypersensitive towards the TNF-alpha apoptotic signal even below threshold concentration. This provides a novel mechanism for deregulation of hepatic cell growth in HBV patients and a new target for intervention in HBV-associated liver cancer and disease.
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PMID:Pro-apoptotic function of HBV X protein is mediated by interaction with c-FLIP and enhancement of death-inducing signal. 1272 77

Although tightly regulated programmed cell death (apoptosis) possesses great importance for tissue homeostasis, several pathologic processes are associated with organ failure due to adversely activated cell apoptosis. Transient increase in apoptosis has been shown to cause organ damage during fulminant hepatitis B, autoimmune diseases, ischemia-reperfusion injury, sepsis, or allograft rejection. A defined and temporary inhibition of cell apoptosis may therefore be of high clinical relevance. Activation of death receptors results in caspase-8 recruitment to the death-inducing signaling complex, which initiates the apoptotic process through cleavage of caspase-8 and downstream substrates. This initial step may be inhibited by the caspase-8 inhibitor FLIP (FLICE inhibitory protein). To specifically inhibit the initiation of death receptor-mediated apoptosis we constructed a fusion protein containing FLIP fused N-terminally to the human immunodeficiency virus TAT domain. This TAT domain allows the fusion protein to cross the cell membrane and thus makes the FLIP domain able to interfere with the death-inducing signaling complex inside of the cell. We observed that incubation of lymphocytic Jurkat or BJAB cells with TAT-FLIPS proteins significantly inhibits Fas-induced activation of procaspase-8 and downstream caspases, preventing cells from undergoing apoptosis. Systemic application of TAT-FLIPS prolongs survival and reduces multi-organ failure due to Fas-receptor-mediated lethal apoptosis in mice. Therefore, application of cellular FLIPS in the form of a TAT fusion protein may open a promising, easily applicable new tool for providing protection against transient, pathologically increased apoptosis in various diseases.
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PMID:Transduction of the TAT-FLIP fusion protein results in transient resistance to Fas-induced apoptosis in vivo. 1530 99

Activation of the cellular stress pathways (c-Jun N-terminal kinase [JNK] and p38 mitogen-activated protein [MAP] kinase) is linked to apoptosis. However, whether both pathways are required for apoptosis remains unresolved. Hepatitis B virus X protein (pX) activates p38 MAP kinase and JNK pathways and, in response to weak apoptotic signals, sensitizes hepatocytes to apoptosis. Employing hepatocyte cell lines expressing pX, which was regulated by tetracycline, we investigated the mechanism of apoptosis by p38 MAP kinase and JNK pathway activation. Inhibition of the p38 MAP kinase pathway rescues by 80% the initiation of pX-mediated apoptosis, whereas subsequent apoptotic events involve both pathways. pX-mediated activation of p38 MAP kinase and JNK pathways is sustained, inducing the transcription of the death receptor family genes encoding Fas/FasL and tumor necrosis factor receptor 1 (TNFR1)/TNF-alpha and the p53-regulated Bax and Noxa genes. The pX-dependent expression of Fas/FasL and TNFR1/TNF-alpha mediates caspase 8 activation, resulting in Bid cleavage. In turn, activated Bid, acting with pX-induced Bax and Noxa, mediates the mitochondrial release of cytochrome c, resulting in the activation of caspase 9 and apoptosis. Combined antibody neutralization of FasL and TNF-alpha reduces by 70% the initiation of pX-mediated apoptosis. These results support the importance of the pX-dependent activation of both the p38 MAP kinase and JNK pathways in pX-mediated apoptosis and suggest that this mechanism of apoptosis occurs in vivo in response to weak apoptotic signals.
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PMID:Sustained activation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase pathways by hepatitis B virus X protein mediates apoptosis via induction of Fas/FasL and tumor necrosis factor (TNF) receptor 1/TNF-alpha expression. 1554 43

Hepatitis B virus (HBV) infection afflicts >300 million people worldwide and is a leading cause of hepatocyte death, cirrhosis, and hepatocellular carcinoma. While the morphological characteristics of dying hepatocytes are well documented, the molecular mechanisms leading to the death of hepatocytes during HBV infection are not well understood. TRAIL, the TNF-related apoptosis-inducing ligand, has recently been implicated in the death of hepatocytes under certain inflammatory but not normal conditions. To determine the potential roles of TRAIL in HBV-induced hepatitis, we examined the effects of HBV and its X protein (HBx) on TRAIL-induced hepatocyte apoptosis both in vivo and in vitro. We found that hepatitis and hepatic cell death in HBV transgenic mice were significantly inhibited by a soluble TRAIL receptor that blocks TRAIL function. We also found that HBV or HBx transfection of a hepatoma cell line significantly increased its sensitivity to TRAIL-induced apoptosis. The increase in TRAIL sensitivity were associated with a dramatic up-regulation of Bax protein expression. Knocking down Bax expression using Bax-specific small interference RNA blocked HBV-induced hepatitis and hepatocyte apoptosis. The degradation of caspases 3 and 9, but not that of Bid or caspase-8, was preferentially affected by Bax knockdown. These results establish that HBV sensitizes hepatocytes to TRAIL-induced apoptosis through Bax and that Bax-specific small interference RNA can be used to inhibit HBV-induced hepatic cell death.
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PMID:Hepatitis B virus sensitizes hepatocytes to TRAIL-induced apoptosis through Bax. 1718 90

The TNF-related apoptosis-inducing ligand (TRAIL) has recently been implicated in the death of hepatocytes under infectious but not normal conditions. Infectious agents, such as hepatitis B virus (HBV), may play important roles in regulating the sensitivity of hepatocytes to TRAIL. Our previous studies showed that HBx, a protein encoded by the HBV genome, enhanced TRAIL-induced apoptosis through upregulating Bax. We report here that another HBV protein called MHBs(t) (C-terminally truncated middle hepatitis B surface protein) is also a potent regulator of TRAIL-induced apoptosis. Overexpressing MHBs(t) in hepatoma cells enhanced TRAIL-induced apoptosis. Mechanistic studies reveal that MHBs(t) had no effect on Bax or TRAIL receptor expression or procaspase-8 activation, but selectively enhanced the activation of ERK2 (extracellular signal-regulated kinase 2) and the degradation of procaspases-3 and 9. ERK2 activation is required for the MHBs(t) effect because ERK2 inhibition by its inhibitor PD98059 significantly reversed TRAIL-induced apoptosis of MHBs(t)-transfected cells. These results establish that unlike HBx, MHBs(t) enhances TRAIL-induced hepatocyte apoptosis through a novel mechanism that involves ERK2. Therefore, manipulating the ERK2 signaling pathway may provide new therapeutic opportunities to contain hepatic cell death during HBV infection.
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PMID:The hepatitis B virus protein MHBs(t) sensitizes hepatoma cells to TRAIL-induced apoptosis through ERK2. 1770 Oct 86

The aim of this study was to test whether long-term ethanol consumption confers therapeutic resistance to human liver cancer patients infected with hepatitis B virus (HBV). Chronic ethanol-treated cells were established by consecutively culturing a human hepatocellular carcinoma cell line, Hep 3B, which contains integrated HBV sequences, for 20-40 passages with or without 10 mM ethanol (designated as E20-E40 and C20-C40, respectively). Flow cytometry analysis demonstrated that a growth promoting effect of long-term ethanol treatment was induced in the E40 cells through preferential acceleration of S-phase in these cells. Lower protein expression levels of p16, p21/Cip1, and p27/Kip1 were detected in the ethanol-treated E40 cells. We further demonstrated that long-term ethanol-treated E40 cells develop drug resistance in response to mitomycin C (MMC) treatment (>8 microM). Immunoblot analysis revealed that caspase-8-mediated mitochondrial apoptotic signals (such as Bad) were inactivated in the MMC-resistant E40 cells. Immunoprecipitation experiments demonstrated that the sequestration of phosphorylated Bad (Ser-112) through its binding with 14-3-3 was detected more profoundly in the MMC-resistant E40 cells. Next, we examined the therapeutic efficacy of MMC (10 mg MMC/kg body weight, three times per week) in severe combined immunodeficient (SCID) mice bearing E40- and C40-xenografted tumors. Significant reductions (>3-fold) in tumor growth were detected in MMC-treated C40-xenografted mice. In vivo and in vitro studies demonstrated that AKT- and extracellular signal-regulated kinase (ERK)-mediated survival factors inhibited the Bad-induced mitochondrial apoptotic signals that were involved in E40 tumor cells and that conferred resistance to MMC.
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PMID:Long-term ethanol exposure causes human liver cancer cells to become resistant to mitomycin C treatment through the inactivation of bad-mediated apoptosis. 2867 44

Agents commonly used in cancer chemotherapy rely on the induction of cell death via apoptosis, mitotic catastrophe, premature senescence and autophagy. Chemoresistance is the major factor limiting long-term treatment success in patients with hepatocellular carcinoma (HCC). Recent studies have revealed that the hepatitis B virus X protein (HBx) exerts anti-apoptotic effects, resulting in an increased drug resistance in HCC cells. In this study, we showed that etoposide treatment activated caspase-8 and caspase-3, leading to cleavages of p53, Bid and PARP, which subsequently induced apoptosis. Furthermore, p53 and Bid were accumulated in cytoplasm following etoposide treatment. However, HBx significantly attenuated etoposide-induced cell death. In HBx-expressing cells, despite the translocation of p53 and Bid to cytoplasm, the activation of caspases was inhibited. Furthermore, the phosphorylation of extracellular-signal-regulated kinase (ERK) was markedly increased in HBx-expressing cells. Moreover, the pretreatment with trichostatin A (TSA, a histone deacetylase inhibitor) or TSA in combination with etoposide significantly sensitized HCC cells to apoptosis by inhibiting ERK phosphorylation, reactivating caspases and PARP, and inducing translocation of p53 and Bid to cytoplasm. Collectively, HBx reduces the sensitivity of HCC cells to chemotherapy. TSA in combination with etoposide can significantly overcome the increased resistance of HBx-expressing HCC cells to chemotherapy.
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PMID:Trichostatin A sensitizes HBx-expressing liver cancer cells to etoposide treatment. 2146 63

The hepatitis B virus X protein (HBx) critically modulates cell growth by inducing apoptosis or proliferation. We sought to clarify whether HBx-mediated apoptosis in a CCL13 stable cell line (Chang-HBx) with inducible HBx expression proceeds through the extrinsic (death receptor-mediated) and/or intrinsic (mitochondrial-mediated) pathways of apoptosis. We used western blotting, cell viability assays, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, caspase activity assays, JC-1 staining and DNA fragmentation analysis to study the role of HBx in apoptosis. The expression of the pro-apoptotic proteins Bax and Bad and the release of cytochrome c also increased slightly upon HBx induction. JC-1 staining showed a loss of mitochondrial membrane potential upon HBx induction. Additionally, induction of HBx increased the levels of cleaved caspase-9 (intrinsic pathway), caspase-8 (extrinsic pathway) and the common effector caspase-3 as measured by western blotting. This elevation of cleaved caspase-8 or caspase-3 and caspase-9 or caspase-3 decreased in the presence of caspase-8 inhibitor Z-IETD-FMK or caspase-9 inhibitor Z-LEHD-FMK, respectively. Both inhibitors also rescued cell growth, and the caspase-8 inhibitor Z-IETD-FMK prevented apoptotic phenomena including the TUNEL signal. DNA fragmentation analysis showed that these phenomena were not detected in the presence of higher concentration of inhibitors. Our data suggest that HBx induces apoptosis through both extrinsic and intrinsic pathways.
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PMID:Apoptosis induced by hepatitis B virus X protein in a CCL13-HBx stable cell line. 2255 76

Hepatitis B virus (HBV) is a major etiological factor of hepatocellular carcinoma (HCC). However, the precise pathogenetic mechanisms linking HBV infection and HCC remain uncertain. It has been reported that decreased antioxidant enzyme activities are associated with severe liver injury and hepatocarcinogenesis in mouse models. It is unclear if HBV can interfere with the activities of antioxidant enzymes. We established a HBV transgenic mouse line, which spontaneously developed HCC at 2 years of age. We studied the activities of the antioxidant enzymes in the liver of the HBV transgenic mice. Our results showed that the antioxidant enzymes glutathione peroxidase and superoxide dismutase 2 were down-regulated in HBV transgenic mice and correlated with JNK activation. HBV enhanced the Fas-mediated activation of caspase 6, caspase 8 and JNK without enhancing the activation of caspase 3 and hepatocellular apoptosis. As a proper redox balance is important for maintaining cellular homeostasis, these effects of HBV on the host antioxidant system and Fas-signaling may play an important role in HBV-induced hepatocarcinogenesis.
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PMID:Hepatitis B virus alters the antioxidant system in transgenic mice and sensitizes hepatocytes to Fas signaling. 2260 92


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