Interferon-alpha sensitizes human hepatoma cells to TRAIL-induced apoptosis through DR5 upregulation and NF-kappa B inactivation

Caspase-8 dependent apoptosis induction in malignant myeloid cells by TLR stimulation in the presence of IFN-alpha

Pro-apoptotic signalling upon toll-like receptor (TLR) stimulation in myeloid cells is normally antagonized by the simultaneous activation of anti-apoptotic pathways. We have previously reported that IFN-alpha can sensitize human monocytes to apoptosis induction by lipopolysaccharide (LPS). Based on these results we investigated whether similarly apoptosis can be cooperatively induced in myeloid tumor cells. When testing established acute myeloid leukemia (AML) cell lines we found the monocytic cell line THP-1 to be sensitive to IFN-alpha plus LPS induced apoptosis, which was partially dependent on caspase-8 and was associated with an enhanced expression of Fas/CD95. We extended our study to 29 short term blast lines from patients with AML and observed additive effects of IFN-alpha and LPS on cell death only with few samples indicating that sensitivity to IFN-alpha plus LPS inducible apoptosis is present in a fraction of AML samples only with no obvious correlation with certain FAB phenotypes.

Anticancer activity of oncolytic adenovirus vector armed with IFN-alpha and ADP is enhanced by pharmacologically controlled expression of TRAIL

We have previously described oncolytic adenovirus (Ad) vectors KD3 and KD3-interferon (IFN) that were rendered cancer-specific by mutations in the E1A region of Ad; these mutations abolish binding of E1A proteins to p300/CBP and pRB. The antitumor activity of the vectors was enhanced by overexpression of the Adenovirus Death Protein (ADP, E3-11.6K) and by replication-linked expression of IFN-alpha. We hypothesized that the anticancer efficacy of the KD3-IFN vector could be further improved by expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). E1-deleted Ad vectors were constructed carrying reporter genes for enhanced green fluorescent protein or secreted placental alkaline phosphatase (SEAP) and a therapeutic gene for TRAIL under control of the TetON system. Expression of the genes was increased in the presence of a helper virus and the inducer doxycycline such that up to 231-fold activation of expression for the TetON-SEAP vector was obtained. Coinfection with TetON-TRAIL augmented oncolytic activity of KD3 and KD3-IFN in vitro. Induction of TRAIL expression did not reduce the yield of progeny virus. Combination of TetON-TRAIL and KD3-IFN produced superior antitumor activity in vivo as compared with either vector alone demonstrating the efficacy of a four-pronged cancer gene therapy approach, which includes Ad oncolysis, ADP overexpression, IFN-alpha-mediated immunotherapy, and pharmacologically controlled TRAIL activity.

Abrogation of constitutive STAT3 activity sensitizes human hepatoma cells to TRAIL-mediated apoptosis

BACKGROUND/AIMS

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated and regulates cell growth and survival of various cancer cells. We investigated the anti-tumor effect of AG490, a Janus kinase 2 specific inhibitor, inhuman hepatoma cells.

METHODS

Effects of AG490 on STAT3 activation, on cell-growth and survival, and on the expression of cell-cycle- and apoptosis-related proteins were evaluated in Huh-1, Huh-7, HepG2 and Hep3B cells. Next, whether AG490 renders hepatoma cells susceptible to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was examined in vitro and in vivo.

RESULTS

Constitutively activated STAT3 through tyrosine phosphorylation was detected in all hepatoma cells. AG490 inhibited the phosphorylation of STAT3 and its activity. AG490 induced cell cycle arrest in Huh-1, Huh-7 and HepG2 through cyclin D1 downregulation, and induced marked apoptosis in Hep3B. AG490 downregulated at least one of the anti-apoptotic proteins, Bcl-xL, survivin or XIAP in all hepatoma cells. AG490 sensitized Huh-1, Huh-7 and HepG2 to TRAIL-induced apoptosis in vitro. Intraperitoneal injection of AG490, the combination of AG490 and TRAIL more greatly, repressed the growth of subcutaneous Huh-7 tumors in athymic mice.

CONCLUSIONS

Abrogation of constitutive activation of STAT3 by AG490 enhances the anti-tumor activity of TRAIL against human hepatoma cells.

Human agonistic antibody to tumor necrosis factor-related apoptosis-inducing ligand receptor 2 induces cytotoxicity and apoptosis in prostate cancer and bladder cancer cells

OBJECTIVES

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a variety of tumor cells through two of its receptors: TRAIL-R1 and TRAIL-R2. In this study, we investigated the susceptibility of human prostate cancer and bladder cancer cells to HGS-ETR2, a human monoclonal agonistic antibody specific for TRAIL-R2.

METHODS

The cell surface expression of TRAIL-R1 and TRAIL-R2 on prostate cancer and bladder cancer cells was determined using flow cytometry. Cytotoxicity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and caspase activities were measured by a quantitative colorimetric assay.

RESULTS

HGS-ETR2 effectively induced apoptotic cell death in DU145, PC3, and LNCaP human prostate cancer cells and J82 and T24 human bladder cancer cells. The increased effectiveness of HGS-ETR2 for inducing cell death might have been affected by differences in the cell surface expression of the two TRAIL receptors, in that TRAIL-R2, but not TRAIL-R1, was frequently expressed in the prostate cancer and bladder cancer cells. HGS-ETR2 significantly activated the caspase cascade, including caspase-3, -6, -8, and -9, which were the downstream molecules of the death receptors in prostate cancer cells. Caspase-3, -6, and -9 were also significantly activated with HGS-ETR2-induced apoptosis in the bladder cancer cells.

CONCLUSIONS

These findings suggest the potential utility of TRAIL-R2 antibody as a novel therapeutic agent against prostate cancer and bladder cancer.

Interferon-alpha induces sensitization of cells to inhibition of protein synthesis by tumour necrosis factor-related apoptosis-inducing ligand

Tumour cells are often sensitized by interferons to the effects of tumour necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL). We have demonstrated previously that TRAIL has an inhibitory effect on protein synthesis [Jeffrey IW, Bushell M, Tilleray VJ, Morley S & Clemens MJ (2002) Cancer Res62, 2272-2280] and we have therefore examined the consequences of prior interferon-alpha treatment for the sensitivity of translation to inhibition by TRAIL. Interferon treatment alone has only a minor effect on protein synthesis but it sensitizes both MCF-7 cells and HeLa cells to the downregulation of translation by TRAIL. The inhibition of translation is characterized by increased phosphorylation of the alpha subunit of eukaryotic initiation factor eIF2 and dephosphorylation of the eIF4E-binding protein 4E-BP1. Both of these effects, as well as the decrease in overall protein synthesis, require caspase-8 activity, although they precede overt apoptosis by several hours. Interferon-alpha enhances the level and/or the extent of activation of caspase-8 by TRAIL, thus providing a likely explanation for the sensitization of cells to the inhibition of translation.

Preclinical differentiation between apparently safe and potentially hepatotoxic applications of TRAIL either alone or in combination with chemotherapeutic drugs

PURPOSE

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) exhibits potent antitumor activity on systemic administration in nonhuman primates without deleterious side effects for normal tissue. However, there is a controversy about the potential toxicity of TRAIL on human hepatocytes. The use of different recombinant TRAIL forms only partially explains the contradicting reports on TRAIL sensitivity in primary human hepatocytes (PHH).

EXPERIMENTAL DESIGN

To clarify this issue, we comprehensively tested four different recombinant forms of TRAIL for their apoptosis-inducing capacity on PHH obtained from a total of 55 human livers between day 1 and day 8 of in vitro culture.

RESULTS

One day after single-cell isolation, all but one recombinant form of TRAIL [i.e., an untagged form of TRAIL (TRAIL.0)] induced apoptosis in PHH. Apoptosis induction by TRAIL in these cells could only be fully inhibited by concomitant blockade of TRAIL receptor 1 and TRAIL receptor 2. At day 4 of in vitro culture, when surrogate markers indicated optimal hepatocyte in vitro function, only high doses of cross-linked FLAG-TRAIL killed PHH whereas the other three recombinant TRAIL forms did not. Strikingly, cotreatment of day 4 PHH with cisplatin sensitized for TRAIL-induced apoptosis whereas 5-fluorouracil, etoposide, gemcitabine, irinotecan, or oxaliplatin, which are commonly used in the treatment of gastrointestinal cancers, did not.

CONCLUSION

Our data show that whereas TRAIL alone or together with selected chemotherapeutic drugs seems to be safe, the combination of TRAIL with cisplatin is toxic to PHH.

Postoperative interferon alpha treatment postponed recurrence and improved overall survival in patients after curative resection of HBV-related hepatocellular carcinoma: a randomized clinical trial

BACKGROUND/AIMS

Recurrence after resection of hepatocellular carcinoma (HCC) is a frequent event. This study evaluated the effect of postoperative interferon alpha (IFN alpha) treatment on recurrence and survival in patients with hepatitis B virus (HBV)-related HCC.

METHOD

Two hundred and thirty six patients were randomized after resection into IFN alpha treatment (5 micro i.m. tiw for 18 months) and control groups. Treatment was terminated if recurrence was diagnosed, and recurrence was managed the same way in both groups. Statistical analysis was based on the method of intent-to-treat.

RESULTS

The two groups were comparable in all clinicopathological parameters. The median overall survival was 63.8 months in the treatment group and 38.8 months in the control group (P=0.0003); the median disease-free survival period was 31.2 versus 17.7 months (P=0.142). Fever, leucocytopenia, and thrombocytopenia were adverse effects in the treatment group, but were mostly manageable.

CONCLUSIONS

IFN alpha treatment improved the overall survival of patients with HBV-related HCC after curative resection, probably by postponing recurrence.

Natural killer cells: primary target for hepatitis C virus immune evasion strategies?

Liver cirrhosis and hepatocellular carcinoma secondary to chronic hepatitis C virus (HCV) infection requiring transplantation represents a significant public health problem. The most remarkable feature of hepatitis C virus is the ability to establish chronic infection in the vast majority of cases. Efforts to define clinical correlates of HCV persistence have focused primarily on CD4 and CD8 T cell responses. Until recently, the role of innate immunity in determining the outcome of HCV infection had received relatively little attention. Natural killer (NK) cells are an important antiviral effector population eliminating virus through direct killing and cytokine production. Recent studies highlighting the cross-talk between NK cells, dendritic cells (DCs) and T cells have prompted reevaluation of the important role NK cells play in regulating and maintaining specific immune responses. Like many other viruses, HCV has evolved strategies to evade detection and elimination by NK cells. T cell defects observed in HCV infection may be a consequence of inhibition of NK:DC interactions. We propose a theoretical model for HCV persistence that places the NK cell at the center of HCV immune evasion strategies. While this model is only theoretical, it provides a plausible interpretation of many published observations and a useful working model to test the role of NK cells in HCV persistence. In conclusion, the role of innate immune cells and their regulation of antigen-specific responses by the initial innate response to the virus, in particular NK cells, may prove to be an informative and clinically relevant avenue of investigation.

Virus or TLR agonists induce TRAIL-mediated cytotoxic activity of plasmacytoid dendritic cells

Among dendritic cells, plasmacytoid dendritic cells (PDC) represent a functionally distinct lineage. Regarding innate immunity, PDC secrete large amounts of type I IFN upon viral exposure or stimulation by microbial products such as unmethylated CpG-motif containing oligo-DNA due to their selective expression of TLR7 and TLR9. We asked whether they could acquire cytotoxic functions during the early phases of infection or after activation with TLR7 or TLR9 agonists. In the present study, we describe a human PDC cell line called GEN2.2, derived from leukemic PDC, that shares most of the phenotypic and functional features of normal PDC. We show that after contact with the influenza virus, GEN2.2, as well as normal PDC, acquires TRAIL and killer activity against TRAIL-sensitive target cells. Moreover, we show that activation of GEN2.2 cells by CpG-motif containing oligo-DNA or R848 also induces TRAIL and endows them with the ability to kill melanoma cells. Therefore, PDC may represent a major component of innate immunity that could participate to the clearance of infected cells and tumor cells. This phenomenon could be relevant for the efficacy of TLR7 or TLR9 agonists in the therapy of infectious disease and cancer.

Sulforaphane Sensitizes Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand (TRAIL)–Resistant Hepatoma Cells to TRAIL-Induced Apoptosis through Reactive Oxygen Species–Mediated Up-regulation of DR5

Sulforaphane is a chemopreventive agent present in various cruciferous vegetables, including broccoli. Here, we show that treatment with tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in combination with subtoxic doses of sulforaphane significantly induces rapid apoptosis in TRAIL-resistant hepatoma cells. Neither TNF-alpha- nor Fas-mediated apoptosis was sensitized in hepatoma cells by cotreatment with sulforaphane, suggesting that sulforaphane can selectively sensitize cells to TRAIL-induced apoptosis but not to apoptosis mediated by other death receptors. We found that sulforaphane treatment significantly up-regulated mRNA and protein levels of DR5, a death receptor of TRAIL. This was accompanied by an increase in the generation of reactive oxygen species (ROS). Pretreatment with N-acetyl-l-cysteine and overexpression of catalase inhibited sulforaphane-induced up-regulation of DR5 and almost completely blocked the cotreatment-induced apoptosis. Furthermore, the sulforaphane-mediated sensitization to TRAIL was efficiently reduced by administration of a blocking antibody or small interfering RNAs for DR5. These results collectively indicate that sulforaphane-induced generation of ROS and the subsequent up-regulation of DR5 are critical for triggering and amplifying TRAIL-induced apoptotic signaling. We also found that sulforaphane can sensitize both Bcl-xL- and Bcl-2-overexpressing hepatoma cells to TRAIL-induced apoptosis, indicating that treatment with a combination of TRAIL and sulforaphane may be a safe strategy for treating resistant hepatomas.

Methionine-stress: A pleiotropic approach in enhancing the efficacy of chemotherapy

Malignant cells fail to utilize homocysteine (HCYS) in place of methionine (MET) and they are dependent on exogenous MET for growth. In animals, reduction of plasma MET to <5 microM can be induced by combined dietary restriction of MET and administration of L-methionine-alpha-deamino-gamma-lyase (methioninase). This treatment, termed as MET-stress, inhibits the growth of brain tumor xenografts in athymic mice and enhances the efficacy of DNA alkylating chemotherapeutic agents. The response of tumors to MET-stress depends on their mutational status, however, it always involves inhibition of CDK1 and in most cases the upregulation of p21, p27, GADDs and 14-3-3sigma in response to upregulation of TGF-beta, IRF-1, TNF-alpha, Rb and/or MDA-7 and the downregulation of PI3K, RAS and NF-kappaB. Although inhibition of the cell cycle and mitosis is not necessarily dependent on the tumor's p53 status, the expression of p21, GADD45 and apoptosis related genes (BAX, BCL-2) are regulated by wt-p53, in addition to their regulation by TGF-beta or MDA-7 in mutated p53 tumors. Mutational variability determines the mode of death (mitotic catastrophe versus apoptosis) in tumor cells subjected to MET-stress. The increase of the efficacy of alkylating agents is related to marked inhibition of O6-methylguanine-DNA methyltransferase (MGMT) expression, the induction of cell cycle check points and the inhibition of pro-survival pathways by MET-stress.

Interferon-alpha enhances TRAIL-mediated apoptosis by up-regulating caspase-8 transcription in human hepatoma cells

BACKGROUND/AIMS

IFNalpha is an approved treatment option for patients chronically infected with the hepatitis B and C viruses. Additionally, there is an indication for tumor therapy. The exact mechanisms underlying the antiviral and antitumor effects of IFNalpha are not completely understood. In this study, we investigated if the pro-apoptotic factor caspase-8 is a target gene of IFNalpha signalling.

METHODS

Huh7 hepatoma cells were used for measuring caspase-8 promoter activity in luciferase reporter assays after IFNalpha stimulation. Caspase-8 expression was monitored by RT-PCR, immunoblotting and measurement of enzymatic activity. Functional caspase-8 promoter elements were identified in gelshift assays and by site directed mutagenesis. Caspase-8 was inhibited using siRNA.

RESULTS

IFNalpha treatment induced caspase-8 promoter activity and mRNA expression. We identified a unique promoter element mediating the IFNalpha-dependent increase in caspase-8 transcription. Up-regulation of caspase-8 expression by IFNalpha had no impact on the rate of apoptosis per se. However, co-stimulation with IFNalpha doubled TRAIL-mediated apoptosis and enzymatic caspase-8 activity. The synergistic effect of TRAIL and IFNalpha could be blocked by inhibiting caspase-8 expression.

CONCLUSIONS

We demonstrate that caspase-8 is a target gene of IFNalpha and provide evidence showing that IFNalpha treatment sensitizes cells for apoptosis via enhanced caspase-8 transcription.

Liver disease in patients with diabetes mellitus

Diabetes mellitus is a growing health concern in our society. In addition to the well-known cardiovascular, renal, and ophthalmologic complications of diabetes, liver-related complications occur commonly and are often underrecognized. The ensuing article will review the relationship between diabetes mellitus and two common liver diseases: chronic hepatitis C and nonalcoholic fatty liver disease. The association with diabetes and cirrhosis, acute liver failure, hepatocellular carcinoma, and outcomes following orthotopic liver transplantation will also be discussed.

PKCdelta protects human breast tumor MCF-7 cells against tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a number of tumorogenic or transformed cells, yet is relatively non-toxic to most normal cells, therefore, it is a promising agent for cancer therapy. However, some cancer cell lines were resistant to TRAIL cytoxicity, including MCF-7 breast cancer cells. The mechanism is not clear. Here, we report that protein kinase C delta (PKCdelta) protects MCF-7 cells from the recombinant soluble TRAIL (rsTRAIL)- mediated apoptosis. It was demonstrated that rottlerin, a PKCdelta inhibitor, sensitized MCF-7 cells to rsTRAIL cytoxicity. Combination of rottlerin and rsTRAIL inhibited PKCdelta translocation from the cytosol to membrane, and PKCdelta kinase activity on the cell membrane was kept pace with the change of PKCdelta expression. Moreover, inhibition of PKCdelta by interference RNA could facilitate apoptosis of MCF-7 cells induced by rsTRAIL. Further experiments on the signal machinery showed that rottlerin increased the sensitivity of MCF-7 cells to rsTRAIL by suppressing the transcription activity of NF-kappaB, and enhancing the caspase-processing to generate executive apoptotic signals. These findings indicate that PKCdelta functions as a survival factor protecting MCF-7 cells from the apoptosis induced by rsTRAIL.

Chemopreventive agent-induced modulation of death receptors

The goals of chemoprevention of cancer are to inhibit the initiation or suppress the promotion and progression of preneoplastic lesions to invasive cancer through the use specific natural or synthetic agents. Therefore, a more desirable and aggressive approach is to eliminate aberrant clones by inducing apoptosis rather than merely slowing down their proliferation. The increased understanding of apoptosis pathways has directed attention to components of these pathways as potential targets not only for chemotherapeutic but also for chemopreventive agents. Activation of death receptors triggers an extrinsic apoptotic pathway, which plays a critical role in tumor immunosurveillance. An increasing number of previously identified chemopreventive agents were found to induce apoptosis in a variety of premalignant and malignant cell types in vitro and in a few animal models in vivo. Some chemopreventive agents such as non-steroidal anti-inflammatory drugs, tritepenoids, and retinoids increase the expression of death receptors. Thus, understanding the modulation of death receptors by chemopreventive agents and their implications in chemoprevention may provide a rational approach for using such agents alone or in combination with other agents to enhance death receptor-mediated apoptosis as a strategy for effective chemoprevention of cancer.

Apoptotic events induced by naturally occurring retinoids ATRA and 13-cis retinoic acid on human hepatoma cell lines Hep3B and HepG2

Two hepatoma cell lines were incubated for 72 h with ATRA and its analog 13cisRA and according to MTT assay, Hep3B cells were highly susceptible whereas HepG2 cells were more resistant to the treatment. At the high concentration of 166 microM, retinoids were able to induce apoptosis in both cell lines and the highest effect was observed in HepG2 cells treated with ATRA. TUNEL-based photometric ELISA showed that at the same retinoid concentration tested by flow cytometry, both cell lines showed apoptosis whereas plasma membranes were not significantly disrupted. Inhibitors of apoptosis Bcl-xL and survivin were downregulated in Hep3B cells by treatment with both retinoids. Bax, a pro-apoptotic protein, was not significantly upregulated in Hep3B cells, but was slightly increased in HepG2 cells treated with 13cisRA. Both procaspase-3 and procaspase-8 were cleaved in Hep3B cells, suggesting apoptosis could be triggered through the extrinsic pathway. In the case of HepG2 cells, lack of caspase activation suggests a mechanism dependent on other kind of proteases.

Role of interleukin-18 and its receptor in hepatocellular carcinoma associated with hepatitis C virus infection

Interleukin (IL)-18 is a proinflammatory cytokine that is up-regulated in patients with hepatitis C virus (HCV) infection, which is the most common underlying disease in hepatocellular carcinoma (HCC). The purpose of our study was to investigate the role of IL-18 in HCC associated with HCV infection. Sixty-five patients with HCC and HCV infections who received curative surgical resections were examined in our study. The expression of the IL-18 receptor was investigated in HCC tissues obtained from these patients and in 2 HCC cell lines. Nuclear factor (NF)-kappaB activity and the expression of Bcl-xL and xIAP mRNA were tested in the cell lines using recombinant human (rh) IL-18. The IL-18 receptor was expressed in both the HCC tissues and the cell lines. NF-kappaB activation and the expression of Bcl-xL and xIAP mRNA were increased by rhIL-18. Moreover, rhIL-18 suppressed the apoptosis of HCC cells which was induced by etoposide in vitro. The overall survival rate (55.4%) was significantly worse in the IL-18 receptor-positive patients than in the IL-18 receptor-negative patients (p = 0.015). In a Cox multivariate analysis, the expression of the IL-18 receptor was found to be a significant predictor of a poor outcome in HCC patients. The expression of the IL-18 receptor and an antiapoptotic mechanism involving NF-kappaB activation in HCC cells may be implicated in a poor patient outcome.

Apoptotic and anti-angiogenic strategies in liver and gastrointestinal malignancies

Inappropriate suppression of apoptosis is strongly implicated in tumorigenesis. Tumor development is heralded by the mutation of tumor suppressor genes and overexpression of anti-apoptotic genes permitting cell survival. Thus, inducing the apoptotic process in various ways can be applied to cancer management. Besides, angiogenesis is a crucial process for tumor growth and metastasis. New strategies targeting fundamental play-markers of the angiogenic process are currently under investigation.

TRAIL is a key target in S-phase slowing-dependent apoptosis induced by interferon-beta in cervical carcinoma cells

Interferon (IFN)-beta induces S-phase slowing and apoptosis in human papilloma virus (HPV)-positive cervical carcinoma cell line ME-180. Here, we show that apoptosis is a consequence of the S-phase lengthening imposed by IFN-beta, demonstrating the functional correlation between S-phase alteration and apoptosis induction. In ME-180 cells, where p53 function is inhibited by HPV E6 oncoprotein, IFN-beta effects on cell cycle and apoptosis occur independently of p53. The apoptosis due to IFN-beta is mediated by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in a manner dependent on the S-phase deregulation. IFN-beta appears to increase TRAIL expression both directly at the mRNA level and indirectly by augmenting surface protein levels as a consequence of the induced S-phase cell accumulation. Moreover, the alteration of the S-phase due to IFN-beta promotes TRAIL-dependent apoptosis by potentiating cell sensitivity to TRAIL, possibly through induction of a proapoptotic NF-kappaB activity and TRAIL-R2 receptor expression. Interestingly, IFN-beta-induced TRAIL-dependent apoptotic events strongly differ in the requirement of caspase activity. These results show that IFN-beta may induce an apoptotic response by deregulating cell cycle. Understanding the linkage between these mechanisms appears to be of primary importance in the search for new IFN-based therapeutic strategies to circumvent cancer disease or improve clinical outcome.

Dengue virus-induced apoptosis in hepatic cells is partly mediated by Apo2 ligand/tumour necrosis factor-related apoptosis-inducing ligand

Although hepatic injury is reported in cases with dengue haemorrhagic fever and dengue shock syndrome, its mechanism remains poorly understood. Several findings suggest that dengue virus (DEN) induces apoptosis of hepatocytes in vivo. In this work, DEN type 2 (DEN-2) strain NGC was shown to induce apoptosis in the hepatic cell line HepG2, and infection of HepG2 cells was found to induce Apo2 ligand (Apo2L, also known as tumour necrosis factor-related apoptosis-inducing ligand or TRAIL) expression. Furthermore, Apo2L/TRAIL induced apoptosis in HepG2 cells, which expressed the Apo2L/TRAIL receptor DR5/TRAIL-R2 on their surface. Analysis of the Apo2L/TRAIL promoter revealed that this gene was activated by DEN-2 infection, whose responsive element was overlapping NF-kappaB- and Sp1-binding sites located at nt -75 to -65. The proteasome inhibitor N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal (LLnL) inhibited Apo2L/TRAIL mRNA expression, and LLnL and anti-Apo2L/TRAIL antibody inhibited DEN-2-induced apoptosis. It was proposed that DEN infection promotes apoptosis partly through the induction of Apo2L/TRAIL expression.

Nuclear factor-kappaB inhibitors as sensitizers to anticancer drugs

The cytotoxicity of chemotherapeutic agents is attributed to apoptosis. Acquired resistance to the effects of chemotherapy has emerged as a significant impediment to effective cancer therapy. One feature that cytotoxic treatments of cancer have in common is their activation of the transcription factor nuclear factor-kappaB (NF-kappaB), which regulates cell survival. NF-kappaB activation suppresses the apoptotic potential of chemotherapeutic agents and contributes to resistance. What evidence is there that inhibitors of NF-kappaB might promote apoptosis in cancer cells and can NF-kappaB inhibitors be used to overcome resistance to chemotherapeutic agents?

Absence of gene mutation in TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2) in chronic myelogenous leukemia and myelodysplastic syndrome, and analysis of mRNA Expressions of TRAIL and TRAIL-related genes in chronic myelogenous leukemia

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an interferon (IFN)-induced molecule with apoptotic activity. We examined gene mutations in the death domains of TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2), and in the TRAIL gene promoter in 46 chronic myelogenous leukemia (CML) patients. In 23 of the 46 patients, all the coding regions of TRAIL-R2 were also examined. However, no mutation or loss of heterozygosity was found. Furthermore, no mutation in the death domains of TRAIL-R1 and TRAIL-R2 genes, which causes amino acid change, was found in 18 myelodysplastic syndrome (MDS) patients. Ribonuclease protection assay (RPA) and real-time quantitative polymerase chain reaction using polymorphonuclear neutrophils of five new CML patients showed that the TRAIL mRNA expression was very low before in vitro IFN-alpha stimulation and markedly upregulated after IFN-alpha stimulation. FAS mRNA was also upregulated with IFN-alpha stimulation but the fold induction was far lower than that of TRAIL mRNA. In addition, RPA revealed that the ratio of (TRAIL-R1 plus TRAIL-R2) to TRAIL-R3 was also increased after IFN-alpha stimulation. Taken together, gene mutations of TRAIL-R1, TRAIL-R2 are infrequent in patients with CML and MDS. And so is the TRAIL promoter for CML. These mutations seem unrelated to tumorigenesis, disease progression, and response to IFN-alpha therapy in CML. A markedly high induction of TRAIL mRNA by IFN-alpha may have some relevance to IFN-alpha action in CML patients.

Alpha-interferon and its effects on signal transduction pathways

Interferon-alpha (IFNalpha) is a recombinant protein widely used in the therapy of several neoplasms such as myeloma, renal cell carcinoma, epidermoid cervical and head and neck tumors, and melanoma. IFNalpha, the first cytokine to be produced by recombinant DNA technology, has emerged as an important regulator of cancer cell growth and differentiation, affecting cellular communication and signal transduction pathways. However, the way by which tumor cell growth is directly suppressed by IFNalpha is not well known. Wide evidence exists on the possibility that cancer cells undergo apoptosis after the exposure to the cytokine. Here we will review the consolidate signal transducer and activator of transcription (STAT)-dependent mechanism of action of IFNalpha. We will discuss data obtained by us and others on the triggering of the stress-dependent kinase pathway induced by IFNalpha and its correlations with the apoptotic process. The regulation of the expression of proteins involved in apoptosis occurrence will be also described. In this regard, IFNalpha is emerging as a post-translational controller of the intracellular levels of the apoptosis-related protein tissue transglutaminase (tTG). This new way of regulation of tTG occurs through the modulation of their proteasome-dependent degradation induced by the cytokine. Until today, inconsistent data have been obtained regarding the clinical effectiveness of IFNalpha in the therapy of solid tumors. In fact, the benefit of IFNalpha treatment is limited to some neoplasms while others are completely or partially resistant. The mechanisms of tumor resistance to IFNalpha have been studied in vitro. The alteration of JAK-STAT components of the IFNalpha-induced signaling, can be indeed a mechanism of resistance to IFN. However, we have recently described a reactive mechanism of protection of tumor cells from the apoptosis induced by IFNalpha dependent on the epidermal growth factor (EGF)-mediated Ras/extracellular signal regulated kinase (Erk) signaling. The involvement of the Ras-->Erk pathway in the protection of tumor cells from the apoptosis induced by IFNalpha is further demonstrated by both Ras inactivation by RASN17 transfection and mitogen extracellular signal regulated kinase 1 (Mek-1) inhibition by exposure to PD098059. These data strongly suggest that the specific disruption of the latter could be a useful approach to potentiate the antitumour activity of IFNalpha against human tumors based on the new mechanistic insights achieved in the last years.

The GRIMs: a new interface between cell death regulation and interferon/retinoid induced growth suppression

Cytokines and vitamins play a central role in controlling neoplastic cell growth. The interferon (IFN) family of cytokines regulates antiviral, anti-tumor, antimicrobial, differentiation, and immune responses in mammals. Significant advances have been made with respect to IFN-induced signal transduction pathways and antiviral responses. However, the IFN-induced anti-tumor actions are poorly defined. Although IFNs themselves inhibit tumor growth, combination of IFNs with retinoids (a class of Vitamin A related compounds) strongly potentiates the IFN-regulated anti-tumor action in a number of cell types. To define the molecular mechanisms involved in IFN/retinoid (RA)-induced apoptosis we have employed a genetic approach and identified several critical genes. In this review, I provide the current picture of IFN- RA- and IFN/RA-regulated growth suppressive pathways. In particular, I focus on a novel set of genes, the genes-associated with retinoid-interferon induced mortality (GRIM). GRIMs may be novel types of tumor suppressors, useful as biological response markers and potentially novel targets for drug development.

Emerging non-apoptotic functions of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/Apo2L

Tumor necrosis factor (TNF) is a cytokine that mediates tumor necrosis. To date, 20 different members of the TNF super-family and 21 different receptors have been identified. All ligands of the TNF super-family have been found to activate transcription factor NF-kappa B and c-Jun kinase. Members of this family have diverse biological effects, including induction of apoptosis, promotion of cell survival, and regulation of the immune system and hematopoiesis. The current review focuses on the biological effects of TNF-related apoptosis-inducing ligand (TRAIL), a TNF super-family member which, a few years ago, generated considerable enthusiasm for its anticancer activity, not accompanied by general toxicity in most normal tissues and organs.

Interferon Therapy for 2 Years or Longer Reduces the Incidence of Hepatocarcinogenesis in Patients with Chronic Hepatitis C Viral Infection

OBJECTIVE

The purpose of this clinical study was to determine the effect of long-term interferon (IFN) administration on the incidence of hepatocellular carcinomas (HCC) in chronic hepatitis C patients, without eradication of hepatitis C virus (HCV) by IFN therapy.

METHODS

The number of patients with biopsy-proven chronic hepatitis with moderate or severe staging, HCV genotype 1b, a high viral load exceeding 1 MEq/ml (mega equivalents per milliliter), who received 6 MU of natural IFN-alpha daily for 2-8 weeks, followed by three times/week for 16-22 weeks, as initial IFN therapy, and positivity for HCV RNA during IFN administration was 131. 47 of the 131 patients continued to be treated with IFN (long-term IFN group, dose 3 or 6 MU twice or three times weekly for 1.5-10.5 years, median 4.0 years) after initial IFN therapy, while 84 patients did not receive any IFN therapy apart from the initial 6-month course (no-add-IFN group). The patients were prospectively monitored, and the cumulative incidence of HCC and risk factors for HCC were examined.

RESULTS

The 5- and 10-year cumulative rates of HCC were 1.9 and 6.4% and 1.9 and 26.8% for long-term IFN and no-add-IFN groups, respectively. Cox regression analysis indicated that the relative risk of HCC in the patients of the no-add-IFN group was 8.72 times of that in patients of the long-term IFN group.

CONCLUSION

Long-term IFN therapy in patients with chronic HCV infection is effective in preventing hepatocarcinogenesis.

Susceptibility of peritoneal macrophages to infection by Theiler's virus

Theiler's murine encephalomyelitis virus (TMEV) strains fall into two groups: high-neurovirulence GDVII virus results in rapidly fatal encephalitis, while low-neurovirulence BeAn and DA viruses produce persistent central nervous system (CNS) infection and inflammatory demyelinating disease. Because macrophages (Mphis) are key components in BeAn virus-induced demyelinating disease, we examined the susceptibility of primary peritoneal macrophages (pMphis) to BeAn infection in vitro. Freshly isolated, thioglycollate-elicited pMphis were resistant to BeAn virus infection even at high multiplicity of infection. In contrast, after incubation of thioglycollate-elicited pMphis at 37 degrees C for 4 days before infection, approximately half of the cells expressed virus antigen(s) and contained nicked DNA indicative of apoptosis. However, BeAn virus RNA replication and virus yields were highly restricted. Interestingly, about one-third of the cells were apoptotic but negative for virus RNA and antigen(s). Tumor necrosis factor-alpha (TNF-alpha) and interferon-alpha (IFN-alpha) were elevated in BeAn-infected pMphi cultures suggesting that bystander killing may be responsible for the apoptosis seen in BeAn virus antigen-negative cells. These data show for the first time that pMphis are susceptible to BeAn virus infection, although the infection is highly restricted and most of these cells undergo BeAn-induced apoptosis.

Modulation of Gene Expression in Human Central Nervous System Tumors under Methionine Deprivation-induced Stress

Methionine deprivation imposes a metabolic stress, termed methionine stress, that inhibits mitosis and induces cell cycle arrest and apoptosis. The methionine-dependent central nervous system tumor cell lines DAOY (medulloblastoma), SWB61 (anaplastic oligodendroglioma), SWB40 (anaplastic astrocytoma), and SWB39 (glioblastoma multiforme) were compared with methionine-stress resistant SWB77 (glioblastoma multiforme). The cDNA-oligoarray analysis and reverse transcription-PCR verification indicated common changes in gene expression in methionine-dependent cell lines to include up-regulation/induction of cyclin D1, mitotic arrest deficient (MAD)1, p21, growth arrest and DNA-damage-inducible (GADD)45 alpha, GADD45 gamma, GADD34, breast cancer (BRCA)1, 14-3-3sigma, B-cell CLL/lymphoma (BCL)1, transforming growth factor (TGF)-beta, TGF-beta-induced early response (TIEG), SMAD5, SMAD7, SMAD2, insulin-like growth factor binding protein (IGFBP7), IGF-R2, vascular endothelial growth factor (VEGF), TNF-related apoptosis-inducing ligand (TRAIL), TNF-alpha converting enzyme (TACE), TRAIL receptor (TRAIL-R)2, TNFR-related death receptor (DR)6, TRAF interacting protein (I-TRAF), IL-6, MDA7, IL-1B convertase (ICE)-gamma, delta and epsilon, IRF1, IRF5, IRF7, interferon (IFN)-gamma and receptor components, ISG15, p65-NF-kappaB, JUN-B, positive cofactor (PC)4, C/ERB-beta, inositol triphosphate receptor I, and methionine adenosyltransferase II. On the other hand, cyclins A1, A2, B1 and B2, cell division cycle (CDC)2 and its kinase, CDC25 A and B, budding uninhibited by benzimidazoles (BUB)1 and 3, MAD2, CDC28 protein kinase (CKS)1 and 2, neuroepithelial cell transforming gene (NET)1, activator of S-phase kinase (ASK), CDC14B phosphatase, BCL2, TGF-beta activated kinase (TAK)1, TAB1, c-FOS, DNA topoisomerase II, DNA polymerase alpha, dihydrofolate reductase, thymidine kinase, stathmin, and MAP4 were down-regulated. In the methionine stress-resistant SWB77, only 20% of the above genes were affected, and then only to a lesser extent. In addition, some of the changes observed in SWB77 were opposite to those seen in methionine-dependent tumors, including expression of p21, TRAIL-R2, and TIEG. Despite similarities, differences between methionine-dependent tumors were substantial, especially in regard to regulation of cytokine expression. Western blot analysis confirmed that methionine stress caused the following: (a) a marked increase of GADD45alpha and gamma in the wt-p53 cell lines SWB61 and 40; (b) an increase in GADD34 and p21 protein in all of the methionine-dependent lines; and (c) the induction of MDA7 and phospho-p38 in DAOY and SWB39, consistent with marked transcriptional activation of the former under methionine stress. It was additionally shown that methionine stress down-regulated the highly active phosphatidylinositol 3'-kinase pathway by reducing AKT phosphorylation, especially in DAOY and SWB77, and also reduced the levels of retinoblastoma (Rb) and pRb (P-ser780, P-ser795, and P-ser807/811), resulting in a shift in favor of unphosphorylated species in all of the methionine-dependent lines. Immunohistochemical analysis showed marked inhibition of nuclear translocation of nuclear factor kappaB under methionine stress in methionine-dependent lines. In this study we show for the first time that methionine stress mobilizes several defined cell cycle checkpoints and proapoptotic pathways while coordinately inhibiting prosurvival mechanisms in central nervous system tumors. It is clear that methionine stress-induced cytotoxicity is not restricted by the p53 mutational status.

Histone deacetylase inhibitors upregulate death receptor 5/TRAIL-R2 and sensitize apoptosis induced by TRAIL/APO2-L in human malignant tumor cells

Death receptor 5 (DR5) is a receptor for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). TRAIL is a promising candidate for cancer therapeutics due to its ability to induce apoptosis selectively in cancer cells. Here, we report that histone deacetylase inhibitors (HDACIs) such as trichostatin A (TSA), sodium butyrate, and suberoylanilide hydroxamic acid (SAHA) upregulated DR5 expression in various human malignant tumor cells. An RNase protection assay demonstrated that HDACIs induced DR5 mRNA markedly but not that of other death receptor family members in Jurkat cells. HDACIs increased DR5 mRNA and protein in a dose- and time-dependent manner. We also show TSA increased DR5 promoter activity using a luciferase promoter assay. Furthermore, we demonstrated that HDACIs strongly sensitized exogenous soluble recombinant human TRAIL-induced apoptosis synergistically in Jurkat and HL-60 cells that were tolerant to TRAIL alone. The combined use of HDACIs and TRAIL in suboptimal concentrations induced Bid cleavage and activation of caspase-8, -10, -3, and -9. Human recombinant DR5/Fc chimera protein, zVAD-fmk pancaspase inhibitor, and caspase-8 and -10 inhibitors efficiently reduced apoptosis induced by cotreatment with HDACIs and TRAIL. Furthermore, TSA did not significantly induce DR5 protein and HDACIs did not enhance TRAIL-induced apoptosis in normal human peripheral blood mononuclear cells. These results suggest that this combined treatment with HDACIs and TRAIL is a promising strategy for new cancer therapeutics.

Norepinephrine regulates hepatic innate immune system in leptin-deficient mice with nonalcoholic steatohepatitis

It is not known why natural killer T (NKT) cells, which modulate liver injury by regulating local cytokine production, are reduced in leptin-deficient ob/ob mice. NKT cells express adrenoceptors. Thus, we hypothesize that the low norepinephrine (NE) activity of ob/ob mice promotes depletion of liver NKT cells, thereby sensitizing ob/ob livers to lipopolysaccharide (LPS) toxicity. To evaluate this hypothesis, hepatic NKT cells were quantified in wild-type mice before and after treatment with NE inhibitors, and in dopamine beta-hydroxylase knockout mice (which cannot synthesize NE) and ob/ob mice before and after 4 weeks of NE supplementation. Decreasing NE activity consistently reduces liver NKT cells, while increasing NE has the opposite effect. Analysis of hepatic and thymic NKT cells in mice of different ages demonstrate an age-related accumulation of hepatic NKT cells in normal mice, while liver NKT cells become depleted after birth in ob/ob mice, which have increased apoptosis of hepatic NKT cells. NE treatment inhibits apoptosis and restores hepatic NKT cells. In ob/ob mice with reduced hepatic NKT cells, hepatic T and NKT cells produce excessive T helper (Th)-1 proinflammatory cytokines and the liver is sensitized to LPS toxicity. NE treatment decreases Th-1 cytokines, increases production of Th-2 cytokines, and reduces hepatotoxicity. Studies of CD1d-deficient mice, which lack the receptor required for NKT cell development, demonstrate that they are also unusually sensitive to LPS hepatotoxicity. In conclusion, low NE activity increases hepatic NKT cell apoptosis and depletes liver NKT cells, promoting proinflammatory polarization of hepatic cytokine production that sensitizes the liver to LPS toxicity.

Transcriptional regulation of the TRAIL-R3 gene

TRAIL-R3 is a decoy receptor for TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), a member of the tumor necrosis factor (TNF) ligand family. TRAIL induces apoptosis in a broad range of cancer cell lines, but not in many normal cells-a finding that generated extraordinary excitement about its potential as a specific antitumor agent. In several cell types, decoy receptors inhibit TRAIL-induced apoptosis by binding to it and preventing its binding to TRAIL proapoptotic or death receptors. However, recently published data regarding the role of these receptors in TRAIL-induced cellular death are contradictory. The key to resolving this controversy may lie in the regulation and cellular localization of TRAIL receptors. In this regard, cloning and analysis of the TRAIL-R3 promoter will help to identify the cellular factors that regulate its transcriptional expression. This chapter summarizes current knowledge in this field and outlines directions for future research.

Chemotherapy induces death receptor 5 in epithelial ovarian carcinoma

OBJECTIVES

Defects in the apoptotic pathway are a general cause for drug resistance. Chemotherapy in combination with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has proven to be an effective strategy to induce apoptosis in vitro in ovarian tumor cells. Systemic TRAIL administration might be a therapeutic option, since no toxicity was observed in nonhuman primates. In the present study, expression of TRAIL and its apoptosis-inducing death receptors (DR4 and DR5) and inhibitory decoy receptor (DcR1) was studied in normal ovaries and in malignant ovarian tumors before and after chemotherapy to investigate the therapeutic potential of TRAIL.

METHODS

DR4, DR5, DcR1, and TRAIL were studied immunohistochemically in 5 normal ovaries, 15 stages I/II, and 26 stages III/IV primary ovarian cancers, including 19 paired tumor samples (pre- and post-chemotherapy).

RESULTS

Surface epithelium of normal ovaries expressed TRAIL and its receptors; ovarian stromal cells expressed only DcR1. Of the ovarian cancers, 73% expressed DR4, 51% DR5, 46% DcR1, and 34% TRAIL. Most primary ovarian cancers (88%) expressed at least one death receptor. TRAIL expression was lower in stage III/IV than in stage I/II tumors (P<0.05). In paired samples, DR5 immunostaining was more frequently (P=0.05) and stronger (P<0.01) expressed in residual tumors.

CONCLUSION

Early stage tumors expressed TRAIL more frequently than advanced stage tumors. Most primary and residual ovarian tumors expressed at least one TRAIL death receptor, while in residual tumors following chemotherapy, DR5 was more frequently expressed. Therefore, human recombinant TRAIL administration might be an interesting treatment option.

Nitric oxide sensitizes prostate carcinoma cell lines to TRAIL-mediated apoptosis via inactivation of NF-κB and inhibition of Bcl-xL expression

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to be selective in the induction of apoptosis in cancer cells with minimal toxicity to normal tissues and this prompted its potential therapeutic application in cancer. However, not all cancers are sensitive to TRAIL-mediated apoptosis and, therefore, TRAIL-resistant cancer cells must be sensitized first to become sensitive to TRAIL. Treatment of prostate cancer (CaP) cell lines (DU145, PC-3, CL-1, and LNCaP) with nitric oxide donors (e.g. (Z)-1-[2-(2-aminoethyl)-N-(2-ammonio-ethyl)amino]diazen-1-ium-1, 2-diolate (DETANONOate)) sensitized CaP cells to TRAIL-induced apoptosis and synergy was achieved. The mechanism by which DETANONOate mediated the sensitization was examined. DETANONOate inhibited the constitutive NF-kappa B activity as assessed by EMSA. Also, p50 was S-nitrosylated by DETANONOate resulting in inhibition of NF-kappa B. Inhibition of NF-kappa B activity by the chemical inhibitor Bay 11-7085, like DETANONOate, sensitized CaP to TRAIL apoptosis. In addition, DETANONOate downregulated the expression of Bcl-2 related gene (Bcl-(xL)) which is under the transcriptional regulation of NF-kappa B. The regulation of NF-kappa B and Bcl-(xL) by DETANONOate was corroborated by the use of Bcl-(xL) and Bcl-x kappa B reporter systems. DETANONOate inhibited luciferase activity in the wild type and had no effect on the mutant cells. Inhibition of NF-kappa B resulted in downregulation of Bcl-(xL) expression and sensitized CaP to TRAIL-induced apoptosis. The role of Bcl-(xL) in the regulation of TRAIL apoptosis was corroborated by inhibiting Bcl-(xL) function by the chemical inhibitor 2-methoxyantimycin A(3) and this resulted in sensitization of the cells to TRAIL apoptosis. Signaling by DETANONOate and TRAIL for apoptosis was examined. DETANONOate altered the mitochondria by inducing membrane depolarization and releasing modest amounts of cytochrome c and Smac/DIABLO in the absence of downstream activation of caspases 9 and 3. However, the combination of DETANONOate and TRAIL resulted in activation of the mitochondrial pathway and activation of caspases 9 and 3, and induction of apoptosis. These findings demonstrate that DETANONOate-mediated sensitization of CaP to TRAIL-induced apoptosis is via inhibition of constitutive NF-kappa B activity and Bcl-(xL) expression.

Inhibitory effects of celecoxib on proliferation of human liver and gastric carcinoma cells in vitro

AIM: To study the inhibitory effects of celecoxib on proliferation of human hepatoma SMMC-7721 cells and gastric cancer SGC-7901 cells in vitro.

METHODS: The two carcinoma cells were cultured with celecoxib at various concentrations(0, 20, 40, 80, 160 and 320 mmol/L). Growth suppression was detected with MTT colorimetric assay, cell apoptotic alterations were evaluated by transmission electron microscopy(TEM), and quantity of Cox-2 was evaluated by cytochemical staining.

RESULTS: The inhibition of proliferation on two carcinoma cells was observed(49.1% and 42.9% by 320 mmol/L celecoxib). The inhibitory effect was dose-dependent. Apoptotic cells were observed under transmission electron microscope. The different quantities of Cox-2 protein in cells were observed by cytochemical staining.

CONCLUSION: Celecoxib inhibits proliferation, induces apoptosis of human two carcinoma cells in vitro, and the effects have close relation to the quantities of Cox-2 protein in cells.

Promoter of TRAIL-R2 Gene

TRAIL-R2 promoter does not have a typical TATA-box but two functional Sp1-binding sites. TRAIL-R2 promoter belongs to the class of TATA-less and GC-box-containing promoters. The minimal promoter element is contained in the region spanning -198 to -116 upstream of translational initiation codon ATG. Computer analysis shows putative transcription factor binding sites such as c-Ets, AML-1a, c-Myb, Sp1, and GATA-1 in TRAIL-R2 promoter. Hypermethylation of TRAIL-R2 is not frequent compared with that of TRAIL-R3 and TRIAL-R4. There are no potential transcription factor binding sites in highly homologous regions between TRAIL-R2 promoter and TRAIL-R1 promoter, or between TRAIL-R2 promoter and mouse homologue mouse killer (MK) promoter. TRAIL-R2 is known to be a downstream gene of p53, a tumor-suppressor gene, and a p53-binding site in TRAIL-R2 intron 1 is responsible for p53-dependent transcription. Thapsigargin, endoplasmic reticulum Ca(2+)-ATPase inhibitor calcium releaser, upregulates TRAIL-R2 expression via the promoter region. Many regulators of TRAIL-R2 have been reported. However, it has not been demonstrated whether they regulate TRAIL-R2 via the promoter region. Here, we show a list of these regulators. Finally, we demonstrate the possibility of cancer therapy using regulation of TRAIL-R2 promoter.

Interferon alpha inhibits the nuclear factor kappa B activation triggered by X gene product of hepatitis B virus in human hepatoma cells

X gene product of hepatitis B virus (HBV) (HBx) regulates many transcription factors including nuclear factor kappa B (NF-kappaB) and plays a key role in hepatocarcinogenesis. In this study, we demonstrated that the expression of full HBV genome and HBx gene similarly stimulated the transcriptional activity of NF-kappaB in HuH-7 human hepatoma cells, and that interferon (IFN)-alpha as well as dominant negative mutant of IkappaB kinase-alpha effectively inhibited the HBx-mediated NF-kappaB activation, but IFN-gamma did not. These results suggest that IFN-alpha may have a function to block the NF-kappaB activating pathway triggered by HBx in HBV hepatocytes.

Effects of hydroxyapatite nanoparticles on proliferation and apoptosis of human hepatoma BEL-7402 cells

AIM: To study the effect of hydroxyapatite (HAP) nanoparticles on human hepatoma cell line BEL-7402 in vitro.

METHODS: The human hepatoma cell line BEL-7402 was cultured and treated with HAP nanoparticles at various concentrations. Growth suppression was detected with MTT colorimetric assay, cell apoptotic alterations were evaluated by cytochemical staining (Hoechst 33258), transmission electron microscopy (TEM), and flow cytometry (FCM).

RESULTS: HAP nanoparticles inhibited the growth of hepatoma cells in a dose-dependent manner, with IC₅₀ values of 29.30 mg/L. Treated with 50-200 mg/L HAP nanoparticles for 48 h, BEL-7402 cells apoptosis with nuclear chromatin condensation and fragmentation as well as cell shrinkage and the formation of apoptotic bodies were observed under cytochemical staining and transmission electron microscopy. FCM analysis showed hypodiploid peaks on histogram, the apoptotic rates at the concentrations of 50, 75, 100, 150 and 200 mg/L of HAP nanoparticles were 20.35 ± 2.23%, 25.35 ± 1.92%, 29.34 ± 4.61%, 44.92 ± 3.78% and 53.64 ± 3.49%, respectively, which were all significantly higher than that of control group 2.23 ± 0.14%. There was a significant correlation between HAP nanoparticle concentration and apoptotic rate (r = 0.994, P < 0.01).

CONCLUSION: HAP nanoparticles not only inhibit proliferation but also induce apoptosis of human hepatoma cell line BEL-7402 in vitro.