Interferon-alpha induces transient upregulation of c-FLIP through NF-kappaB activation

Combined inhibition of NF-κB and Bcl-2 triggers synergistic reduction of viability and induces apoptosis in melanoma cells

Constitutive activation of nuclear factor κB (NF-κB) characterizes melanoma cells. To explore the molecular mechanism of melanoma cell survival by constitutive NF-κB activation, we used the NF-κB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ), which directly binds to NF-κB. DHMEQ abrogated constitutive NF-κB activity, which included RelA (p65)/p50 in melanoma cell lines G361 and HMV-II; however, the reduction of the viability was marginal. Expression of c-FLIP was not observed in the melanoma cell lines tested, and DHMEQ could not repress the expression of the Bcl-2 family proteins Bcl-2 and Bcl-xL. Concomitant treatment with DHMEQ and the inhibitor of antiapoptotic Bcl-2 family proteins, GX15-070, triggered synergistic reduction of the viability and induced apoptosis of G361 cells. These results indicate that abrogation of the NF-κB pathway alone is not sufficient to suppress the survival of melanoma cells. The NF-κB and the antiapoptotic Bcl-2 pathways cooperatively support the survival, and the dual targeting triggers synergistic reduction of the viability and induces apoptosis of melanoma cells.

c-FLIP protects eosinophils from TNF-α-mediated cell death in vivo

Understanding the signals that regulate eosinophil survival and death is critical to developing new treatments for asthma, atopy, and gastrointestinal disease. Previous studies suggest that TNF-α stimulation protects eosinophils from apoptosis, and this TNF-α-mediated protection is mediated by the upregulation of an unknown protein by NF-κB. Here, we show for the first time that eosinophils express the caspase 8-inhibitory protein c-FLIP, and c-FLIP expression is upregulated upon TNF-α stimulation. Considering that c-FLIP expression is regulated by NF-κB, we hypothesized that c-FLIP might serve as the “molecular switch” that converts TNFRI activation to a pro-survival signal in eosinophils. Indeed, we found that one c-FLIP isoform, c-FLIP_L, is required for mouse eosinophil survival in the presence of TNF-α both in vitro and in vivo. Importantly, our results suggest c-FLIP as a potential therapeutic target for the treatment of eosinophil-mediated disease.

Expression of c-FLIP in pulmonary metastases in osteosarcoma patients and human xenografts

OBJECTIVE(S)

We have previously shown that Fas expression inversely correlates with the metastatic potential of osteosarcoma (OS) to the lung. FasL is constitutively expressed in the lung microenvironment and eliminates Fas(+) OS cells leaving Fas(-) cells to form metastases. Absence of FasL in the lung epithelium or blocking the Fas-signaling pathway interfered with this clearance mechanism allowing Fas(+) cells to remain and form lung metastases. We also demonstrated that while the majority of patient OS lung metastases were Fas(-), 10-20% of the lesions contained Fas(+) cells, suggesting that these cells were not sensitive to FasL-induced apoptosis. The expression of c-FLIP, an inhibitor of the Fas pathway, has been associated with tumor development, progression, and resistance to chemotherapy. We therefore evaluated the expression of c-FLIP in OS patient tumor specimens and human xenograft lung metastases.

METHODS

OS patient tissues, which included both primary and metastatic lesions, were evaluated for the expression of c-FLIP. In addition, tumors from human OS xenografts were examined for c-FLIP expression.

RESULTS

c-FLIP expression was significantly higher in the lung metastases than in the primary tumors.

CONCLUSION(S)

c-FLIP may play an important role in the metastatic potential of OS to the lung. Inhibition of c-FLIP may be a future therapeutic target.

Oncogenic fusion E2A-HLF sensitizes t(17;19)-positive acute lymphoblastic leukemia to TRAIL-mediated apoptosis by upregulating the expression of death receptors

t(17;19)-acute lymphoblastic leukemia (ALL) shows extremely poor prognosis. E2A-HLF derived from t(17;19) blocks apoptosis induced by the intrinsic mitochondrial pathway and has a central role in leukemogenesis and chemoresistance. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is expressed on cytotoxic T cells and natural killer cells and binds with death receptors (DR4/DR5), inducing apoptosis by dual activation of intrinsic and extrinsic pathways, and TRAIL mediates the graft-versus-leukemia (GVL) effect after allogeneic stem cell transplantation (allo-SCT). We found that cell lines and patients' samples of t(17;19)-ALL expressed death receptors for TRAIL, and recombinant soluble TRAIL immediately induced apoptosis into t(17;19)-ALL cell lines. E2A-HLF induced gene expression of DR4/DR5, which was dependent on the DNA-binding and transactivation activities of E2A-HLF through the 5' upstream region of the start site at least in the DR4 gene. Introduction of E2A-HLF into non-t(17;19)-ALL cell line upregulated DR4 and DR5 expression, and sensitized to proapoptotic activity of recombinant soluble TRAIL. Finally, a newly diagnosed t(17;19)-ALL patient underwent allo-SCT immediately after induction of first complete remission, and the patient has survived without relapse for over 3-1/2 years after allo-SCT. These findings suggest that E2A-HLF sensitizes t(17;19)-ALL to the GVL effect by upregulating death receptors for TRAIL.

PKC-δ mediates interferon-α-induced apoptosis through c-Jun NH₂-terminal kinase activation

Background

Interferon-α (IFN-α) exerts an anti-tumor effect at least through induction of apoptosis in a variety of types including B lymphoma cells. We recently found that IFN-α induced a sustained activation of c-Jun NH₂-terminal kinase1 (JNK1), which is implicated in activation of the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) promoter. In the present study, we explored upstream component(s) of the prolonged IFN-α-initiated activation of JNK1.

Results

IFN-α caused activation of PKC-δ in Daudi B lymphoma cells and myeloma U266 cells, as detected by Western blotting using a monoclonal antibody specific for the phosphorylated form of PKC-δ. The dominant-negative form of mutant PKC-δ (dnPKC-δ) reduced the IFN-α-induced JNK1 activation, TRAIL promoter activity, loss of mitochondrial membrane potential (ΔΨm), and increase in propidium iodide (PI) positive cells. The IFN-α-induced activation of JNK1 and the TRAIL promoter was also attenuated by the PKC-δ inhibitor rottlerin. Moreover, a constitutively active form of mutant PKC-δ enhanced the IFN-α-induced TRAIL promoter activity and loss of ΔΨm in Daudi B lymphoma cells. In addition, IFN-α-induced Ser727 phosphorylation of Stat1 was also abrogated by dnPKC-δ.

Conclusions

IFN-α induced JNK1 activation via PKC-δ, leading to upregulation of TRAIL. The interaction of the consequent enhanced TRAIL expression with TRAIL-receptor results in a loss of ΔΨm and increase in PI positive cells. The IFN-α-induced apoptotic events may also be affected by the Ser727-Stat1 induced by PKC-δ-mediated signaling component(s).

Cardiac extrinsic apoptotic pathway is silent in young but activated in elder mice overexpressing bovine GH: interplay with the intrinsic pathway

Apoptosis may occur through the mitochondrial (intrinsic) pathway and activation of death receptors (extrinsic pathway). Young acromegalic mice have reduced cardiac apoptosis whereas elder animals have increased cardiac apoptosis. Multiple intrinsic apoptotic pathways have been shown to be modulated by GH and other stimuli in the heart of acromegalic mice. However, the role of the extrinsic apoptotic pathways in acromegalic hearts is currently unknown. In young (3-month-old) acromegalic mice, expression of proteins of the extrinsic apoptotic pathway did not differ from that of wild-type animals, suggesting that this mechanism did not participate in the lower cardiac apoptosis levels observed at this age. On the contrary, the extrinsic pathway was active in elder (9-month-old) animals (as shown by increased expression of TRAIL, FADD, TRADD and increased activation of death inducing signaling complex) leading to increased levels of active caspase 8. It is worth noting that changes of some pro-apoptotic proteins were induced by GH, which seemed to have, in this context, pro-apoptotic effects. The extrinsic pathway influenced the intrinsic pathway by modulating t-Bid, the cellular levels of which were reduced in young and increased in elder animals. However, in young animals this effect was due to reduced levels of Bid regulated by the extrinsic pathway, whereas in elder animals the increased levels of t-Bid were due to the increased levels of active caspase 8. In conclusion, the extrinsic pathway participates in the cardiac pro-apoptotic phenotype of elder acromegalic animals either directly, enhancing caspase 8 levels or indirectly, increasing t-Bid levels and conveying death signals to the intrinsic pathway.

Febrile-range hyperthermia augments lipopolysaccharide-induced lung injury by a mechanism of enhanced alveolar epithelial apoptosis

Fever is common in critically ill patients and is associated with worse clinical outcomes, including increased intensive care unit mortality. In animal models, febrile-range hyperthermia (FRH) worsens acute lung injury, but the mechanisms by which this occurs remain uncertain. We hypothesized that FRH augments the response of the alveolar epithelium to TNF-alpha receptor family signaling. We found that FRH augmented LPS-induced lung injury and increased LPS-induced mortality in mice. At 24 h, animals exposed to hyperthermia and LPS had significant increases in alveolar permeability without changes in inflammatory cells in bronchoalveolar lavage fluid or lung tissue as compared with animals exposed to LPS alone. The increase in alveolar permeability was associated with an increase in alveolar epithelial apoptosis and was attenuated by caspase inhibition with zVAD.fmk. At 48 h, the animals exposed to hyperthermia and LPS had an enhanced lung inflammatory response. In murine lung epithelial cell lines (MLE-15, LA-4) and in primary type II alveolar epithelial cells, FRH enhanced apoptosis in response to TNF-alpha but not Fas ligand. The increase in apoptosis was caspase-8 dependent and associated with suppression of NF-kappaB activity. The FRH-associated NF-kappaB suppression was not associated with persistence of IkappaB-alpha, suggesting that FRH-mediated suppression of NF-kappaB occurs by means other than alteration of IkappaB-alpha kinetics. These data show for the first time that FRH promotes lung injury in part by increasing lung epithelial apoptosis. The enhanced apoptotic response might relate to FRH-mediated suppression of NF-kappaB activity in the alveolar epithelium with a resultant increase in susceptibility to TNF-alpha-mediated cell death.

The nutrigenomics of asthma: molecular mechanisms of airway neutrophilia following dietary antioxidant withdrawal

Depletion of antioxidants through consumption of a low antioxidant diet has been reported to increase neutrophilic airway inflammation and worsen symptoms of asthma. Using a nutrigenomics approach, this study explores the mechanisms of airway neutrophilic inflammation due to depletion of dietary antioxidants. Induced sputum samples were collected at baseline and after participants consumed a low antioxidant diet for 14 days. Genome-wide gene expression profiles were generated from sputum RNA samples from participants with a >10% change in sputum neutrophils using Illumina Humanref-8 expression microarrays. There were 104 genes differentially expressed following the dietary change. Upregulated genes were involved in the innate immune response and included the innate immune receptors TLR2, IL1R2, CD93, the signaling molecules IRAK2, IRAK3, and neutrophil proteases MMP25 and CPD. Downregulated genes included those involved in endogenous antioxidant defenses (GSTA1, GSTA2) and protease inhibition (SLPI, SERPINB3). Altered expression of five genes (TLR2, IRAK2, IL1R2, C20orf114, and SERPINB3) was confirmed using real-time polymerase chain reaction (PCR). These observations suggest that depletion of dietary antioxidants in asthma may result in upregulation of genes involved in the innate immune response. A diet low in antioxidants may be contributing to the development of neutrophilic asthma through activation of the innate immune response.

Novel expression signatures identified by transcriptional analysis of separated leucocyte subsets in systemic lupus erythematosus and vasculitis

Objective

To optimise a strategy for identifying gene expression signatures differentiating systemic lupus erythematosus (SLE) and antineutrophil cytoplasmic antibody-associated vasculitis that provide insight into disease pathogenesis and identify biomarkers.

Methods

44 vasculitis patients, 13 SLE patients and 25 age and sex-matched controls were enrolled. CD4 and CD8 T cells, B cells, monocytes and neutrophils were isolated from each patient and, together with unseparated peripheral blood mononuclear cells (PBMC), were hybridised to spotted oligonucleotide microarrays.

Results

Using expression data obtained from purified cells a substantial number of differentially expressed genes were identified that were not detectable in the analysis of PBMC. Analysis of purified T cells identified a SLE-associated, CD4 T-cell signature consistent with type 1 interferon signalling driving the generation and survival of tissue homing T cells and thereby contributing to disease pathogenesis. Moreover, hierarchical clustering using expression data from purified monocytes provided significantly improved discrimination between the patient groups than that obtained using PBMC data, presumably because the differentially expressed genes reflect genuine differences in processes underlying disease pathogenesis.

Conclusion

Analysis of leucocyte subsets enabled the identification of gene signatures of both pathogenic relevance and with better disease discrimination than those identified in PBMC. This approach thus provides substantial advantages in the search for diagnostic and prognostic biomarkers in autoimmune disease.

Stromal anti-apoptotic androgen receptor target gene c-FLIP in prostate cancer

PURPOSE

The tumor microenvironment significantly influences prostate cancer progression. Androgen receptor exerts its effect through downstream target genes to regulate prostate cancer cell proliferation. The c-FLIP gene was recently shown to be an androgen receptor target gene. c-FLIP is an inactive homologue of caspase-8 and, thus, it inhibits the death receptor mediated apoptosis pathway. c-FLIP over expression was shown to accelerate the progression of prostate cancer cells to androgen independence. We evaluated the role of c-FLIP expression in stromal cells in prostate cancer development.

MATERIALS AND METHODS

We examined c-FLIP expression in 53 androgen dependent and 21 androgen independent prostate cancer stromal cells by immunohistochemical analysis. The effects of c-FLIP over expression in stromal cells on the growth and invasion of LNCaP and PC3 prostate cancer cells were determined in indirect coculture systems.

RESULTS

At the androgen dependent stage the stromal c-FLIP level was increased in prostate cancer tissue. The expression level of stromal c-FLIP was associated with tumor differentiation. However, stromal c-FLIP expression was not increased in androgen independent human prostate cancer. c-FLIP over expression in stromal cells stimulated the growth and invasion of prostate cancer, including LNCaP and PC3 cells in vitro.

CONCLUSIONS

These results indicate the over expression of stromal c-FLIP and its function for promoting prostate cancer growth and invasion.

TNF-alpha mediates pseudorabies virus-induced apoptosis via the activation of p38 MAPK and JNK/SAPK signaling

PRV infection causes apoptosis in vitro and in vivo. However, the significance of PRV-induced apoptosis and its signaling pathways is still unknown. This work investigates the role of MAPK pathways in mediating PRV-induced apoptosis. Flow cytometry, apoptosis ELISA and western blotting using antibodies against cleaved caspase-3, -6 and PARP demonstrated that PRV induces apoptosis in a time- and dose-dependent manner. p38 and JNK/SAPK inhibitors significantly protected cells from PRV-induced apoptosis. Inhibitor treatment did not affect Us3a gene transcription and progeny virus production. Western blotting revealed that PRV activates p38 and JNK/SAPK signaling. Inhibition of NF-kappaB had no effect on PRV-mediated apoptosis. Non-replicative PRV failed to activate p38 and JNK/SAPK or induce apoptosis. PRV infection increases TNF-alpha transcription, translation and secretion, as well as TNF-alpha receptor expression. Inhibition of p38 and JNK/SAPK reduced PRV-induced TNF-alpha up-regulation. Neutralization assay confirmed that TNF-alpha is a key mediator involved in PRV-induced apoptosis.