Nuclear factor-kappa B-inducible death effector domain-containing protein suppresses tumor necrosis factor-mediated apoptosis by inhibiting caspase-8 activity

Variance of TNFAIP8 expression between tumor tissues and tumor-infiltrating CD4+ and CD8+ T cells in non-small cell lung cancer

Tumor necrosis factor alpha-induced protein 8 (TNFAIP8) has been recently documented in various malignancies, but its role in non-small cell lung cancer (NSCLC) remains uncertain. In the current study, we investigated the level of TNFAIP8 in NSCLC tissues, adjacent noncancerous lung tissues, healthy lung tissues, CD4+ T cells, and CD8+ T cells by real-time reverse transcription PCR (RT-PCR) and Western blot analysis. Results revealed that the mRNA level of TNFAIP8 was significantly increased in cancer tissue than in healthy lung tissue from donors (p < 0.001). Interestingly, adjacent noncancerous lung tissues also showed higher mRNA level of TNFAIP8 than healthy lung tissue from donors (p < 0.01). Similarly, protein level of TNFAIP8 was elevated in NSCLC tissues and adjacent noncancerous lung tissues. We further analyzed TNFAIP8 expression in CD4+ T cells and CD8+ T cells. Data demonstrated that both mRNA level and protein level were significantly decreased in tumor-infiltrating CD4+ and CD8+ T cells than in peripheral CD4+ and CD8+ T cells. Moreover, patients with advanced stages presented lower protein expression of TNFAIP8 in tumor-infiltrating CD8+ T cells than patients with primary stages (p < 0.05). These results provide evidence that TNFAIP8 plays critical roles in NSCLC and may be used as a therapeutic target for the disease.

TNFAIP8 as a predictor of metastasis and a novel prognostic biomarker in patients with epithelial ovarian cancer

Background:

Tumour necrosis factor-α-induced protein 8 (TNFAIP8) has been recently documented in various malignancies, but its role in epithelial ovarian cancer (EOC) remains unknown.

Methods:

Tumour necrosis factor-α-induced protein 8 expression was determined by real-time reverse transcription PCR and western blot analysis. Tumour tissues, consisting of serous, mucinous, endometrioid and clear cell histotypes, from 202 EOC patients (International Federation of Gynecologists and Obstetricians I–IV) who underwent primary cytoreduction were collected. Then, we examined the immunohistochemical expression of TNFAIP8 and evaluated its clinical significances.

Results:

Tumour necrosis factor-α-induced protein 8 overexpression was significantly associated with high histologic grade (P=0.005), large residual tumour size (P=0.014), recurrence (P=0.024) and response to chemotherapy (P<0.001). Multivariate analysis showed that TNFAIP8 overexpression was independently correlated with the presence of lymph node (odds ratio (OR): 4.129; 95% confidence interval (CI): 1.491–11.435; P=0.006) and intraperitoneal metastasis (OR: 2.209; 95% CI: 1.174–4.156; P=0.014). Moreover, results revealed that the status of TNFAIP8 expression was an independently prognostic factor for both cancer-specific survival (hazard ratio (HR): 1.852; 95% CI: 1.322–2.594; P<0.001) and disease-free survival (HR: 1.724; 95% CI: 1.235–2.407; P=0.001) in patients with EOC.

Conclusion:

The present data provide evidence that TNFAIP8 predicts EOC metastasis and poor survival, highlighting its potential function as a therapeutic target for EOCs.

Discovering the infectome of human endothelial cells challenged with Aspergillus fumigatus applying a mass spectrometry label-free approach

Blood vessel invasion is a key feature of invasive aspergillosis. This angioinvasion process contributes to tissue thrombosis, which can impair the access of leukocytes and antifungal drugs to the site of infection. It has been demonstrated that human umbilical vein endothelial cells (HUVECs) are activated and assume a prothrombotic phenotype following contact with Aspergillus fumigatus hyphae or germlings, a process that is independent of fungus viability. However, the molecular mechanisms by which this pathogen can activate endothelial cells, together with the endothelial pathways that are involved in this process, remain unknown. Using a label-free approach by High Definition Mass Spectrometry (HDMS(E)), differentially expressed proteins were identified during HUVEC-A. fumigatus interaction. Among these, 89 proteins were determined to be up- or down-regulated, and another 409 proteins were exclusive to one experimental condition: the HUVEC control or HUVEC:AF interaction. The in silico predictions provided a general view of which biological processes and/or pathways were regulated during HUVEC:AF interaction, and they mainly included cell signaling, immune response and hemostasis pathways. This work describes the first global proteomic analysis of HUVECs following interaction with A. fumigatus germlings, the fungus morphotype that represents the first step of invasion and dissemination within the host.

BIOLOGICAL SIGNIFICANCE

A. fumigatus causes the main opportunistic invasive fungal infection related to neutropenic hematologic patients. One of the key steps during the establishment of invasive aspergillosis is angioinvasion but the mechanism associated with the interaction of A. fumigatus with the vascular endothelium remains unknown. The identification of up- and down-regulated proteins expressed by human endothelial cells in response to the fungus infection can contribute to reveal the mechanism of endothelial response and, to understand the physiopathology of this high mortality disease. This article is part of a Special Issue entitled: Trends in Microbial Proteomics.

TIPE2 mRNA overexpression correlates with TNM staging in renal cell carcinoma tissues

Tumor necrosis factor α-induced protein-8 like-2 (TIPE2) is a gene that maintains immune homeostasis. The aim of the present study was to determine whether TIPE2 is associated with renal cell carcinoma (RCC) progression. The mRNA expression levels of TIPE2 and myxoma resistance protein 1 (MX1; a type I interferon-inducible gene) were investigated in renal cancer tissues. A total of 46 patients who fulfilled the RCC criteria of the World Health Organization (WHO; revised in 2004) and 39 control patients with renal contusions requiring surgical extraction were enrolled. Tumor and normal renal tissues were sampled from all subjects through surgery. Total RNA was extracted and the expression of the TIPE2 and MX1 genes was evaluated by quantitative polymerase chain reaction (qPCR) analysis. TIPE2 mRNA expression was significantly upregulated in the RCC patients compared with the controls (P=0.001), while MX1 mRNA expression was decreased in the RCC patients compared with the controls (P=0.0001). Furthermore, the TIPE2 mRNA expression levels were positively correlated with TNM staging (r=0.803, P=0.001) and showed a negative correlation with the MX1 mRNA expression levels (r=−0.763, P=0.001) in the RCC patients. These results indicate that the increased expression of the TIPE2 gene is markedly associated with RCC and suggests an important role for the TIPE2 gene in the pathogenesis of RCC.

Functional variants in TNFAIP8 associated with cervical cancer susceptibility and clinical outcomes

Tumor necrosis factor-α-induced protein 8 (TNFAIP8) is an anti apoptotic and pro-oncogenic signaling molecule involved in the process of immunity, carcinogenesis and tumor progression. Single nucleotide polymorphisms (SNPs) at microRNA-binding sites may change messenger RNA target gene function, thus leading to cancer susceptibility and tumor progression. In this study of 1584 cervical cancer cases and 1394 cancer-free female controls, we investigated associations between three potentially functional SNPs in TNFAIP8 family genes and cervical cancer risk as well as platinum resistance and clinical outcomes in Eastern Chinese women. We found that the TNFAIP8-rs11064 variant GG genotype was associated with an increased risk of cervical cancer compared with AA/AG genotypes (adjusted odds ratio = 2.16, 95% confidence interval = 1.16-4.03, P = 0.015). Further in vitro and ex vivo functional experiments demonstrated that the TNFAIP8-rs11064 variant G allele weakened the binding affinity of miR-22 to the TNFAIP8 3'-untranslated region (UTR) in four cancer cell lines, resulting in increased production of the TNFAIP8 protein in the patients' cervical tissues. In the survival subset, the high TNFAIP8 protein expression was significantly associated with both resistance to cisplatin and nedaplatin, recurrence and death from cervical cancer. Taken together, in the absence of information on human papillomavirus (HPV) infection, the TNFAIP8-rs11064 SNP may function by affecting the affinity of miR-22 binding to the 3'-UTR of TNFAIP8 and regulating TNFAIP8 expression, thus contributing to cervical cancer risk. Additionally, the increased TNFAIP8 protein expression may predict platinum resistance and clinical outcomes in cervical cancer patients. Larger, prospective studies with detailed HPV infection data are warranted to validate our findings.

Gene transcription and biomarker responses in the clam Ruditapes philippinarum after exposure to ibuprofen

Pharmaceuticals are a class of emerging environmental contaminants that continuously enter aquatic environments. Presently, little information is available about the effects of these substances on non-target organisms, such as bivalves. We investigated the effects of ibuprofen (IBU) on the clam Ruditapes philippinarum. Clams were exposed for 1, 3, 5 and 7 days to 0, 100 and 1000 μgIBU/L, and established biomarker responses (haemolymph lysozyme, gill acetylcholinesterase and digestive gland superoxide dismutase activities) as well as digestive gland transcriptome were evaluated. A two-way ANOVA revealed significant effects of both "IBU concentration" and "exposure duration" on biomarker responses. Overall, the enzyme activities were generally lower in IBU-exposed clams than in controls. Although limited knowledge of the mollusc transcriptome makes it difficult to interpret the effects of IBU on clams, the gene transcription analysis using DNA microarrays enabled the identification of the putative molecular mode of action of the IBU. The functional analysis of differentially transcribed genes suggests that IBU can interfere with various signalling pathways in clams, such as arachidonic acid metabolism, apoptosis, peroxisomal proliferator-activated receptors, and nuclear factor-kappa B. In addition, several genes involved in the metabolism of xenobiotics (e.g., glutathione S-transferase, sulfotransferase, cytochrome P450) were also found to be significantly affected by IBU exposure. In summary, the integrated approach of gene transcription analysis and biomarker responses facilitated the elucidation of the putative mechanisms of action of IBU in non-target species.

The significance of TNFAIP8 in prostate cancer response to radiation and docetaxel and disease recurrence

TNFAIP8 is a NF-κB-inducible, oncogenic molecule. Previous "promoter array" studies have identified differential methylation and regulation of TNFAIP8 in prostate epithelial and cancer cell lines. Here we demonstrate that TNFAIP8 expression is induced by androgen in hormone-responsive LNCaP prostate cancer cells. In athymic mice bearing hormone-refractory PC-3 prostate tumor xenografts, intravenous treatment with a liposomal formulation of TNFAIP8 antisense oligonucleotide (LE-AS5) caused reduced expression of TNFAIP8 in tumor tissues, and a combination of LE-AS5 and radiation or docetaxel treatment resulted in significant inhibition of PC-3 tumor growth as compared to single agents. The immunohistochemical evaluation of TNFAIP8 expression revealed correlation of both cytoplasmic and nuclear TNFAIP8 overexpression with high grade prostatic adenocarcinomas, while nuclear overexpression was found to be an independent predictor of disease recurrence controlling for tumor grade. Increased nuclear TNFAIP8 expression was statistically significantly associated with a 2.44 fold (95 % confidence interval: 1.01-5.91) higher risk of prostate cancer recurrence. Mechanistically, TNFAIP8 seems to function as a scaffold (or adaptor) protein. In the antibody microarray analysis of proteins associated with the TNFAIP8 immune-complex, we have identified Karyopherin alpha2 as a novel binding partner of nuclear TNFAIP8 in PC-3 cells. The Ingenuity Pathway Analysis of the TNFAIP8 interacting proteins suggested that TNFAIP8 influences cancer progression pathways and networks involving integrins and matrix metalloproteinases. Taken together, present studies demonstrate that TNFAIP8 is a novel therapeutic target in prostate cancer, and indicate a potential relationship of the nuclear trafficking of TNFAIP8 with adverse outcomes in a subset of prostate cancer patients.

The Effect of Tumor Necrosis Factor-α-Induced Protein 8 Like-2 on Immune Response of CD4+T Lymphocytes in Mice after Thermal Injury

The status of cellular immunity has been shown to be associated with the occurrence and development of sepsis. Accumulating evidence has demonstrated that tumor necrosis factor-α-induced protein 8 like-2 (TIPE2) plays an important role in maintaining homeostasis of immune function. The present study, with the use of a controlled in vivo approach, demonstrated the effect of TIPE2 on cell-mediated immunity of CD4+ T lymphocytes in thermal injury murine model. One hundred and twenty-eight male mice were randomly allocated into four groups, which were sham burn group (n=48), burn group (n=48), burn with lentivirus-RNAi-TIPE2 transfection group (n=16), burn with negative control transfection group (n=16), and they were sacrificed at the designated time points. CD4+ T lymphocytes were isolated from the spleen using MACS microbeads. Phenotypes were analyzed by flow cytometry analysis, and cytokines were determined using ELISA kits. We found that the expression of TIPE2 was markedly increased in CD4+T lymphocytes in mice at 24,48 and 72 hours postburn. Down-regulation of TIPE2 by lentivirus-RNAi-TIPE2 attenuated the suppressive effect of CD4+T lymphocytes, which was associated with profound elevation of nuclear factor of activated T cell (NF-AT) activity. These results demonstrate that TIPE2 appear to be involved in the immune regulation of CD4+ T lymphocytes, and the decrease in TIPE2 expression on CD4+T lymphocytes in vivo can enhance peripheral T lymphocyte function after thermal injury. These data might provide a valid strategy to prevent the development of immunosuppressive state resulted from major burns.

Morin inhibits STAT3 tyrosine 705 phosphorylation in tumor cells through activation of protein tyrosine phosphatase SHP1

The major goal of cancer drug discovery is to find an agent that is safe and affordable, yet effective against cancer. Here we show that morin (3,5,7,2',4'-pentahydroxyflavone) has potential against cancer cells through suppression of the signal transducer and activator of transcription 3 (STAT3) pathway, which is closely linked to the transformation, survival, proliferation, and metastasis of cancer. We found that morin completely suppressed inducible and constitutively activated STAT3 and blocked the nuclear translocation of STAT3 and its DNA binding in multiple myeloma and head and neck squamous carcinoma cells. Morin inhibited activated Src, JAK-1, and JAK-2, all of which are linked to STAT3 activation, while up-regulating a protein inhibitor of activated STAT3, PIAS3. Pervanadate reversed the effects of morin on STAT3 phosphorylation, indicating the role of a protein tyrosine phosphatase. Furthermore, morin induced SHP1 expression at both the mRNA and protein levels, and silencing of SHP1 abrogated the effect of morin on STAT3 phosphorylation, indicating that morin mediates its effects on STAT3 through SHP1. Suppression of STAT3 correlated with the down-regulation of various gene products linked to tumor survival, proliferation, and angiogenesis and led to sensitization of tumor cells to thalidomide and bortezomib. Comparing the activities of morin with those of four structurally related flavonols demonstrated the importance of hydroxyl groups in the B ring in inhibiting STAT3 activation. These findings suggest that morin suppresses the STAT3 pathway, leading to the down-regulation of STAT3-dependent gene expression and chemosensitization of tumor cells.

Expression of tumor necrosis factor-alpha-induced protein 8 in pancreas tissues and its correlation with epithelial growth factor receptor levels

Tumor necrosis factor (TNF)-alpha-induced protein 8 (TNFAIP8 or TIPE) is a recently identified protein considered to be associated with carcinogenesis. To investigate its expression pattern in pancreatic cancer patients and to analyse its correlation with clinicopathological significance and the expression levels of epithelial growth factor receptor (EGFR), immunohistochemistry was performed to detect the TNFAIP8 and EGFR proteins in pancreatic cancers, pancreatitis tissues, and healthy controls. The results showed stronger staining of TNFAIP8 protein in pancreatic cancer tissues compared with normal pancreas tissue. Furthermore, in 56 patients with pancreatic cancer, the expression levels of TNFAIP8 in patients with low tumor stage was higher than that with high tumor stage, and correlated with tumor staging and lymph node metastasis (P<0.05). Furthermore, TNFAIP8 expression positively correlated with EGFR levels (r=0.671135, P<0.05). These results indicate that TNFAIP8 may play important roles in the progression of pancreatic cancer.

SCC-S2 is overexpressed in colon cancers and regulates cell proliferation

SCC-S2 was recently reported to be overexpressed in various cancers and associated with the malignant behavior of cancer cells. However, the expression of SCC-S2 and its biological roles in colon cancers have not been reported. The aim of this study is to investigate the expression and clinical significance of SCC-S2 in colon cancers and explore its biological function in colon cancer cells. We analyzed the expression pattern of SCC-S2 in 92 colon cancer tissues by immunohistochemistry and found that SCC-S2 was overexpressed in 45 (48.9 %) of 92 colon cancer specimens. There was a significant association between SCC-S2 overexpression and TNM stage (p = 0.0387), lymph node metastasis (p = 0.0219), and proliferation index (p = 0.0279). siRNA knockdown of SCC-S2 expression in CACO2 and HCT116 cells decrease cell proliferation, colony formation, and soft agar colony formation ability. Furthermore, western blot analysis showed that SCC-S2 depletion decreased cyclin D1 and phospho-Rb levels. In conclusion, we demonstrated that SCC-S2 is overexpressed in colon cancers and contributes to malignant cell growth by cyclin D1 and phospho-Rb modulation, which makes SCC-S2 a candidate therapeutic target in colon cancer.

Tumor necrosis factor-α induced protein 8 polymorphism and risk of non-Hodgkin's lymphoma in a Chinese population: a case-control study

BACKGROUND

Non-Hodgkin's lymphoma (NHL) has been reported to be associated with autoimmune and pro-inflammatory response, and genetic polymorphisms of candidate genes involved in autoimmune and pro-inflammatory response may influence the susceptibility to NHL. To evaluate the role of such genetic variations in risk of NHL, we conducted a case-control study of 514 NHL patients and 557 cancer-free controls in a Chinese population.

METHOD

We used the Taqman assay to genotype six potentially functional single nucleotide polymorphisms (SNPs) in six previously reported inflammation and immune-related genes (TNF rs1799964T>C, LTA rs1800683G>A, IL-10 rs1800872T>G, LEP rs2167270G>A, LEPR rs1327118C>G, TNFAIP8 rs1045241C>T). Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CI).

RESULTS

We observed a significantly increased risk of NHL associated with the TNFAIP8 rs1045241C>T polymorphism (adjusted OR = 3.03; 95% CI = 1.68-5.45 for TT vs. CC and adjusted OR = 2.03; 95% CI = 1.53-2.69 for CT/TT vs. CC). The risk associated with the T allele was more evident in subgroups of 40-60 year-old, non-smokers or light-smokers (less than 25 pack-years), and subjects with normal weight or overweight. Risk for both B and T cell non-Hodgkin's lymphoma was elevated for CT/TT genotypes (adjusted OR = 1.95, 95% CI = 1.41-2.70 for B cell NHL and adjusted OR = 2.22, 95% CI = 1.49-3.30 for T cell NHL), particularly for DLBCL (adjusted OR = 2.01, 95%CI = 1.41-2.85) and FL (adjusted OR = 2.53, 95% CI = 1.17-5.45). These risks were not observed for variant genotypes of other five SNPs compared with their common homozygous genotypes.

CONCLUSIONS

The polymorphism of TNFAIP8 rs1045241C>T may contribute to NHL susceptibility in a Chinese population. Further large-scale and well-designed studies are needed to confirm these results.

TNFAIP8 overexpression: clinical relevance to esophageal squamous cell carcinoma

BACKGROUND

Tumor necrosis factor alpha-induced protein 8 (TNFAIP8) is a suppressor of TNF-α mediated apoptosis, and its expression is induced by NF-κB activation. TNFAIP8 expression is significantly increased in various cancer cell lines. A correlation between TNFAIP8 overexpression, cancer progression, and poor prognosis has been described in many reports of human solid cancers.

METHODS

To clarify the functional and clinical significance of the cancer progression-related gene, TNFAIP8, in esophageal squamous cell carcinoma (ESCC), we used immunohistochemistry to demonstrate TNFAIP8 expression in ESCC. Next, TNFAIP8 expression was depleted by using siRNA to examine the function of TNFAIP8 in the proliferation and apoptosis induction of ESCC cell lines.

RESULTS

We detected correlations between TNFAIP8 expression and TNM stage (P < 0.001), tumor depth (P = 0.002), lymph node metastasis (P = 0.013), distant metastasis (P = 0.001), lymphatic invasion (P < 0.001), and venous invasion (P < 0.001) among the clinicopathological characteristics of ESCC patients, and high TNFAIP8 expression was found in poor survival. TNFAIP8 depletion was significantly associated with apoptosis induction after cisplatin administration and reduced proliferation.

CONCLUSIONS

Our results suggest that TNFAIP8 might be an effective therapeutic target for ESCC in the future.

Early response of bovine alveolar macrophages to infection with live and heat-killed Mycobacterium bovis

Bovine tuberculosis (TB) is a disease of economic importance and a significant animal health and welfare issue. The alveolar macrophage (AlvMϕ) plays a vital role in the immune response to TB and recent studies provide insights into the interactions between Mϕ and Mycobacterium bovis. Here we reveal the early transcriptional response of bovine AlvMϕ to M. bovis infection. We demonstrate up-regulation of immune response genes, including chemokines, members of the NF-κB pathway which may be involved in their transcription and also pro- and anti-apoptotic genes. M. bovis may therefore induce multiple mechanisms to manipulate the host immune response. We compared the response of AlvMϕ to infection with live and heat-killed M. bovis to determine transcriptional differences dependent on the viable pathogen. Several chemokines up-regulated following live M. bovis infection were not up-regulated after heat-killed M. bovis stimulation; hence the Mϕ seems to differentiate between the two stimuli.

TNFAIP8: a new effector for Galpha(i) coupling to reduce cell death and induce cell transformation

Galpha(i)-coupled receptors comprise a diverse family of receptors that induce transformation by largely unknown mechanisms. We previously found that the Galpha(i)-coupled dopamine-D2short (D2S) receptor transforms Balb-D2S cells via Gαi3. To identify new Gαi effectors, a yeast two-hybrid screen was done using constitutively active Gαi3-Q204L as bait, and tumor necrosis factor-alpha (TNFα)-induced protein 8 (TNFAIP8, SCC-S2/NDED/GG2-1) was identified. In contrast, TNFAIP8-related TIPE1 and TIPE2 showed a very weak interaction with Gαi3. In yeast mating, in vitro pull-down, co-immunoprecipitation and bioluminescence resonance energy transfer (BRET) assays, TNFAIP8 preferentially interacted with activated Gαi proteins, consistent with direct Gαi-TNFAIP8 coupling. Over-expression or depletion of TNFAIP8 using antisense constructs in Balb-D2S cells did not affect D2S-induced signaling to Gαi-dependent inhibition of cAMP. In contrast, antisense depletion of TNFAIP8 completely inhibited spontaneous and D2S-induced foci formation, consistent with a role for TNFAIP8 in Gαi-dependent transformation. To address possible mechanisms, the effect of D2S signaling via TNFAIP8 on TNFα action was examined. D2S receptor activation inhibited TNFα-induced cell death in Balb-D2S cells, but not in cells depleted of TNFAIP8. However, depletion of TNFAIP8 did not prevent D2S-induced inhibition of TNFα-mediated caspase activation, suggesting that D2S/TNFAIP8-induced protection from TNFα-induced cell death is caspase-independent. The data suggest that Gαi-TNFAIP8-mediated rescue of pre-oncogenic cells enhances progression to oncogenic transformation, providing a selective target to inhibit cellular transformation.

Overexpression of SCC-S2 correlates with lymph node metastasis and poor prognosis in patients with non-small-cell lung cancer

The objective of the current study was to investigate the expression pattern and clinicopathological significance of SCC-S2 in patients with non-small-cell lung cancer (NSCLC). The expression profile of SCC-S2 in NSCLC tissues and adjacent noncancerous lung tissues was detected by real-time RT-PCR, western blot analysis, and immunohistochemistry. In 25 lung cancer tissues examined, 18 (72%) of them exhibited stronger levels of SCC-S2 mRNA compared with their corresponding normal tissues. SCC-S2 protein level was up-regulated in cancerous lung tissues compared to adjacent normal tissue. Moreover, the expression level of SCC-S2 in 93 archived NSCLC tissues was measured by immunohistochemical staining. SCC-S2 was found to be overexpressed in 71 of 93 (76.3%) human lung cancer samples and correlated with lymph node metastasis (P = 0.0181), p-TNM stage (P = 0.0042), Ki-67 expression (P = 0.0028), and poor survival (P = 0.012). In addition, depleting SCC-S2 expression by small-interfering RNA inhibited growth and invasion in lung cell lines. These results indicate that SCC-S2 plays an important role in NSCLC and might be a useful therapeutic target of NSCLC.

Microarray analysis of Shigella flexneri-infected epithelial cells identifies host factors important for apoptosis inhibition

Background

Shigella flexneri inhibits apoptosis in infected epithelial cells. In order to understand the pro-survival effects induced by the bacteria, we utilized apoptosis-specific microarrays to analyze the changes in eukaryotic gene expression in both infected and uninfected cells in the presence and absence of staurosporine, a chemical inducer of the intrinsic pathway of apoptosis. The goal of this research was to identify host factors that contribute to apoptosis inhibition in infected cells.

Results

The microarray analysis revealed distinct expression profiles in uninfected and infected cells, and these changes were altered in the presence of staurosporine. These profiles allowed us to make comparisons between the treatment groups. Compared to uninfected cells, Shigella-infected epithelial cells, both in the presence and absence of staurosporine, showed significant induced expression of JUN, several members of the inhibitor of apoptosis gene family, nuclear factor κB and related genes, genes involving tumor protein 53 and the retinoblastoma protein, and surprisingly, genes important for the inhibition of the extrinsic pathway of apoptosis. We confirmed the microarray results for a selection of genes using in situ hybridization analysis.

Conclusion

Infection of epithelial cells with S. flexneri induces a pro-survival state in the cell that results in apoptosis inhibition in the presence and absence of staurosporine. The bacteria may target these host factors directly while some induced genes may represent downstream effects due to the presence of the bacteria. Our results indicate that the bacteria block apoptosis at multiple checkpoints along both pathways so that even if a cell fails to prevent apoptosis at an early step, Shigella will block apoptosis at the level of caspase-3. Apoptosis inhibition is most likely vital to the survival of the bacteria in vivo. Future characterization of these host factors is required to fully understand how S. flexneri inhibits apoptosis in epithelial cells.

Resistance to ErbB2 tyrosine kinase inhibitors in breast cancer is mediated by calcium-dependent activation of RelA

The widespread clinical use of therapies targeting the ErbB2 receptor tyrosine kinase oncogene represents a significant advance in breast cancer treatment. However, the development of therapeutic resistance represents a dilemma limiting their clinical efficacy, particularly small-molecule tyrosine kinase inhibitors that block ErbB2 autophosphorylation and activation. Here, we show that lapatinib (GW572016), a highly selective, small-molecule inhibitor of the ErbB2 and epidermal growth factor receptor tyrosine kinases, which was recently approved for the treatment of advanced-stage ErbB2(+) breast cancer, unexpectedly triggered a cytoprotective stress response in ErbB2(+) breast cancer cell lines, which was mediated by the calcium-dependent activation of RelA, the prosurvival subunit of NF-kappaB. Abrogation of lapatinib-induced RelA activation using either small interfering RNA constructs or an intracellular calcium chelator enhanced the apoptotic effects of lapatinib in parental ErbB2(+) breast cancer cells and overcame therapeutic resistance to lapatinib in ErbB2(+) breast cancer lines that had been rendered resistant to lapatinib through chronic exposure to the drug, mimicking the clinical setting. In addition, analysis of changes in phospho-RelA expression in sequential clinical biopsies from ErbB2(+) breast cancers treated with lapatinib monotherapy revealed marginally statistically significant differences between responders and nonresponders, which was consistent with our preclinical findings. Elucidating the regulation of RelA by lapatinib in ErbB2(+) breast cancers, and showing its role in the development of therapeutic resistance to lapatinib, identifies another therapeutic target to overcome or prevent the onset of resistance to lapatinib in some women with ErbB2(+) breast cancers.

A chicken ovalbumin upstream promoter transcription factor I (COUP-TFI) complex represses expression of the gene encoding tumor necrosis factor alpha-induced protein 8 (TNFAIP8)

The orphan nuclear receptor chicken ovalbumin upstream promoter transcription factor I (COUP-TFI) plays key roles in development and homeostasis. A tandem affinity purification procedure revealed that COUP-TFI associated with a number of transcriptional regulatory proteins in HeLa S3 cells, including the nuclear receptor corepressor (NCoR), TIF1beta/KAP-1, HDAC1, and the SWI/SNF family member Brahma. The proapoptotic protein DBC1 was also identified in COUP-TFI complexes. In vitro experiments revealed that COUP-TFI interacted directly with NCoR but in a manner different from that of other nuclear receptors. DBC1 stabilized the interaction between COUP-TFI and NCoR by interacting directly with both proteins. The gene encoding the anti-apoptotic protein TNFAIP8 (tumor necrosis factor alpha (TNFalpha)-induced protein 8) was identified as being repressed by COUP-TFI in a manner that required several of the component proteins of the COUP-TFI complex. Finally, our studies highlight a central role for COUP-TFI in the induction of the TNFAIP8 promoter by TNFalpha. Together, these studies identify a novel COUP-TFI complex that functions as a repressor of transcription and may play a role in the TNFalpha signaling pathways.

Wnt/beta-catenin inhibits dental pulp stem cell differentiation

Dental pulp stem cells (DPSCs) are a unique precursor population isolated from postnatal human dental pulp and have the ability to regenerate a reparative dentin-like complex. Canonical Wnt signaling plays a critical role in tooth development and stem cell self-renewal through beta-catenin. In this study, the regulation of odontoblast-like differentiation of DPSCs by canonical Wnt signaling was examined. DPSCs were stably transduced with canonical Wnt-1 or the active form of beta-catenin, with retrovirus-mediated infection. Northern blot analysis found that Wnt-1 strongly induced the expression of matricellular protein osteopontin, and modestly enhanced the expression of type I collagen in DPSCs. Unexpectedly, Wnt-1 inhibited alkaline phosphatase (ALP) activity and the formation of mineralized nodules in DPSCs. Moreover, over-expression of beta-catenin was also sufficient to suppress the differentiation and mineralization of DPSCs. In conclusion, our results suggest that canonical Wnt signaling negatively regulates the odontoblast-like differentiation of DPSCs.

Midkine is a NF-kappaB-inducible gene that supports prostate cancer cell survival

Background

Midkine is a heparin-binding growth factor that is over-expressed in various human cancers and plays important roles in cell transformation, growth, survival, migration, and angiogenesis. However, little is known about the upstream factors and signaling mechanisms that regulate midkine gene expression.

Methods

Two prostate cancer cell lines LNCaP and PC3 were studied for their expression of midkine. Induction of midkine expression in LNCaP cells by serum, growth factors and cytokines was determined by Western blot analysis and/or real-time quantitative reverse-transcription – polymerase chain reaction (RT-PCR). The cell viability was determined by the trypan blue exclusion assay when the LNCaP cells were treated with tumor necrosis factor alpha (TNFα) and/or recombinant midkine. When the LNCaP cells were treated with recombinant midkine, activation of intracellular signalling pathways was determined by Western blot analysis. Prostate tissue microarray slides containing 129 cases (18 normal prostate tissues, 40 early stage cancers, and 71 late stage cancers) were assessed for midkine expression by immunohistochemical staining.

Results

We identified that fetal bovine serum, some growth factors (epidermal growth factor, androgen, insulin-like growth factor-I, and hepatocyte growth factor) and cytokines (TNFα and interleukin-1beta) induced midkine expression in a human prostate cancer cell line LNCaP cells. TNFα also induced midkine expression in PC3 cells. TNFα was the strongest inducer of midkine expression via nuclear factor-kappa B pathway. Midkine partially inhibited TNFα-induced apoptosis in LNCaP cells. Knockdown of endogenous midkine expression by small interfering RNA enhanced TNFα-induced apoptosis in LNCaP cells. Midkine activated extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase pathways in LNCaP cells. Furthermore, midkine expression was significantly increased in late stage prostate cancer, which coincides with previously reported high serum levels of TNFα in advanced prostate cancer.

Conclusion

These findings provide the first demonstration that midkine expression is induced by certain growth factors and cytokines, particularly TNFα, which offers new insight into understanding how midkine expression is increased in the late stage prostate cancer.

Osteoblasts express NLRP3, a nucleotide-binding domain and leucine-rich repeat region containing receptor implicated in bacterially induced cell death

Bacterially induced osteoblast apoptosis may be a major contributor to bone loss during osteomyelitis. We provide evidence for the functional expression in osteoblasts of NLRP3, a member of the NLR family of cytosolic receptors that has been implicated in the initiation of programmed cell death.

INTRODUCTION

Osteoblasts undergo apoptosis after exposure to intracellular bacterial pathogens commonly associated with osteomyelitis. Death of this bone-forming cell type, in conjunction with increased numbers and activity of osteoclasts, may underlie the destruction of bone tissue at sites of bacterial infection. To date, the mechanisms responsible for bacterially induced apoptotic osteoblast cell death have not been resolved.

MATERIALS AND METHODS

We used flow cytometric techniques to determine whether intracellular invasion is needed for maximal apoptotic cell death in primary osteoblasts after challenge with Salmonella enterica. In addition, we used real-time PCR and immunoblot analyses to assess osteoblast expression of members of the nucleotide-binding domain leucine-rich repeat region-containing family of intracellular receptors (NLRs) that have been predicted to be involved in the induction of programmed cell death. Furthermore, we have used co-immunoprecipitation and siRNA techniques to confirm the functionality of such sensors in this cell type.

RESULTS

In this study, we showed that invasion of osteoblasts by Salmonella is necessary for maximal induction of apoptosis. We showed that murine and human osteoblasts express NLRP3 (previously known as CIAS1, cryopyrin, PYPAF1, or NALP3) but not NLRC4 (IPAF) and showed that the level of expression of this cytosolic receptor is modulated after bacterial challenge. We showed that osteoblasts express ASC, an adaptor molecule for NLRP3, and that these molecules associate after Salmonella infection. In addition, we showed that a reduction in the expression of NLRP3 attenuates Salmonella-induced reductions in the activity of an anti-apoptotic transcription factor in osteoblasts. Furthermore, we showed that NLRP3 expression is needed for caspase-1 activation and maximal induction of apoptosis in osteoblasts after infection with Salmonella.

CONCLUSIONS

The functional expression of NLRP3 in osteoblasts provides a potential mechanism underlying apoptotic cell death of this cell type after challenge with intracellular bacterial pathogens and may be a significant contributory factor to bone loss at sites of infection.

Down-regulation of c-FLIP increases reactive oxygen species, induces phosphorylation of serine/threonine kinase Akt, and impairs motility of cancer cells

The role of c-FLIP in cell motility was investigated using RNA interference. Down-regulation of c-FLIP increased amounts of reactive oxygen species (ROS), while over-expression of c-FLIP produced opposite effect. ROS induced phosphorylation of Akt and impaired cell motility.

A dominant function of IKK/NF-kappaB signaling in global lipopolysaccharide-induced gene expression

Porphyromonas gingivalis is an etiologic pathogen of periodontitis that is one of the most common inflammatory diseases. Recently, we found that P. gingivalis LPS activated the transcription factor nuclear factor-kappaB (NF-kappaB) through the IkappaB kinase complex (IKK). NF-kappaB is a transcription factor that controls inflammation and host responses. In this study, we examined the role of IKK/NF-kappaBin P. gingivalis LPS-induced gene expression on a genome-wide basis using a combination of microarray and biochemical approaches. A total of 88 early response genes were found to be induced by P. gingivalis LPS in a human THP.1 monocytic cell lines. Interestingly, the induction of most of these genes was abolished or attenuated under the inactivation of IKK/NF-kappaB. Among those IKK/NF-kappaB-dependent genes, 20 genes were NF-kappaB-inducible genes reported previously, and 59 genes represented putative novel NF-kappaB target genes. Using transcription factor binding analysis, we found that most of these putative NF-kappaB target genes contained one or multiple NF-kappaB-binding sites. Also, some transcription factor-binding motifs were overrepresented in the promoter of both known and putative NF-kappaB-dependent genes, indicating that these genes may be regulated in a similar fashion. Furthermore, we found that several transcription factors associated with metabolic and inflammatory responses, including nuclear receptors, activator of protein-1, and early growth responses, were induced by P. gingivalis LPS through IKK/NF-kappaB, indicating that IKK/NF-kappaB may utilize these transcription factors to mediate secondary responses. Taken together, our results demonstrate that IKK/NF-kappaB signaling plays a dominant role in P. gingivalis LPS-induced early response gene expression, suggesting that IKK/NF-kappaB is a therapeutic target for periodontitis.

Involvement of alpha1beta1 integrin in insulin-like growth factor-1-mediated protection of PC12 neuronal processes from tumor necrosis factor-alpha-induced injury

Insulin-like growth factor 1 receptor (IGF-1R) supports neuronal survival against a wide variety of insults. This includes tumor necrosis factor-alpha (TNFalpha)-mediated neuronal damage, which represents one of the factors suspected to play a role in HIV-associated dementia (HAD). PC12 neurons engineered to express human IGF-1R (PC12/IGF-1R) maintain neuronal processes on collagen IV for several weeks. However, prolonged treatment with TNFalpha caused degeneration of neuronal processes, with no apparent signs of apoptosis. In this process, TNFalpha did not affect IGF-1-mediated phosphorylation of IRS-1, IRS-2, Akt, or Erks. In addition, PC12/IGF-1R cells were found to express predominantly alpha1beta1 integrin, which has high affinity to collagen IV. The treatment of PC12/IGF-1R neurons with a specific alpha1beta1 integrin inhibitor, obtustatin, also caused loss of neuronal processes, accompanied by a quick cell detachment and extensive apoptosis. In the presence of IGF-1, both TNFalpha-induced and obtustatin-induced degeneration of neuronal processes were effectively inhibited. Furthermore, TNFalpha-mediated neuronal degeneration correlated with decreased attachment of PC12/IGF-1R cells to collagen IV and with a reduced level of alpha1beta1 integrin, consistent with a role for this surface protein in the maintenance of neuronal processes. Thus the neuroprotective effects of IGF-1 are not restricted to its antiapoptotic properties but also involve an additional neuroprotective mechanism, by which IGF-1 counteracts the negative effect of TNFalpha on alpha1beta1 integrin-mediated attachment to collagen IV.

Interleukin-17 receptor-like gene is a novel antiapoptotic gene highly expressed in androgen-independent prostate cancer

We have recently identified a new gene, interleukin-17 receptor-like (IL-17RL), which is expressed in normal prostate and prostate cancer. This investigation is focused on the role of IL-17RL in prostate cancer. We found that IL-17RL was expressed at significantly higher levels in several androgen-independent prostate cancer cell lines (PC3, DU145, cds1, cds2, and cds3) and tumors compared with the androgen-dependent cell lines (LNCaP and MLC-SV40) and tumors. In an in vivo model of human prostate tumor growth in nude mice (CWR22 xenograft model), IL-17RL expression in tumors was induced by androgen deprivation. The relapsed androgen-independent tumors expressed higher levels of IL-17RL compared with the androgen-dependent tumors. Overexpression of IL-17RL in tumor necrosis factor alpha (TNFalpha)-sensitive LNCaP cells inhibited TNFalpha-induced apoptosis by blocking activation of caspase-3 downstream to caspase-2 and caspase-8. Reciprocally, knocking down IL-17RL expression by small interfering RNA induced apoptosis in all the prostate cancer cell lines studied. Taken together, these results show that IL-17RL is a novel antiapoptotic gene, which may confer partially the property of androgen-independent growth of prostate cancer by promoting cell survival. Thus, IL-17RL is a potential therapeutic target in the treatment of prostate cancer.

Inhibition of NF-kappaB enhances the cytotoxicity of virus-directed enzyme prodrug therapy and oncolytic adenovirus cancer gene therapy

Virus-directed enzyme prodrug therapy utilizing the bacterial enzyme nitroreductase delivered by a replication-defective adenovirus vector to activate the prodrug CB1954 is a promising strategy currently undergoing clinical trials in patients with a range of cancers. Similarly, selectively replicating oncolytic adenoviruses are entering clinical trials. An understanding of interactions between vector and target cell are critical to the development of these strategies. We demonstrate that adenovirus vectors activate cellular pathways that promote cell survival in an NF-kappaB-dependent manner, and consequently have a negative effect on the efficacy of cell killing induced by cancer gene therapy strategies. This provides a potential therapeutic target to enhance the cytotoxicity of these approaches.

Role of SCC-S2 in experimental metastasis and modulation of VEGFR-2, MMP-1, and MMP-9 expression

SCC-S2/GG2-1/NDED (approved gene symbol TNFAIP8) is a transcription factor NF-kappaB-inducible, antiapoptotic, and oncogenic molecule. In this study, we examined the role of SCC-S2 in invasion and experimental metastasis. We demonstrate that expression of SCC-S2 cDNA in MDA-MB 435 human breast cancer cells is associated with enhanced invasion in vitro and increased frequency of pulmonary colonization of tumor cells in athymic mice. Systemic treatment of athymic mice with a cationic liposomal formulation of SCC-S2 antisense oligo led to decreased incidence of pulmonary metastasis and inhibition of SCC-S2 expression in vivo. Antisense inhibition of endogenous SCC-S2 expression correlated with decreased expression of VEGF receptor-2 in tumor cells and human lung microvascular endothelial cells and loss of endothelial cell viability. In addition, downregulation of SCC-S2 expression in tumor cells was associated with decreased expression of known metastasis-related molecules MMP-1 and MMP-9. These results demonstrate a novel role for SCC-S2 in tumor progression, involving multiple effectors, and provide a basis for SCC-S2-targeted cancer gene therapy.

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.

NF-kappaB activation in human dental pulp stem cells by TNF and LPS

Post-natal human dental pulp stem cells (DPSCs) represent a unique precursor population in the dental pulp, which has multipotential and can regenerate a dentin/pulp-like structure. Because the dental pulp is frequently infected by oral bacteria due to dental decay, in this study, we examined whether lipopolysaccharide (LPS) and tumor necrosis factor (TNF) activated the immunologic transcription factor nuclear factor kappa B (NF-kappaB) in DPSCs. We found that both TNF and LPS activated the I-kappa B kinase complex (IKK) in DPSCs to induce the phosphorylation and degradation of IkappaBalpha, resulting in the nuclear translocation of NF-kappaB. Consistently, both TNF and LPS rapidly induced the expression of the NF-kappaB-dependent gene interleukin-8 (IL-8). However, unlike in monocytes, we found that LPS could not induce the phosphorylation of the NF-kappaB active subunit p65 in DPSCs. In summary, our studies suggest that DPSCs may be involved in immune responses during pulpal infection through activating NF-kappaB.

Tumour necrosis factor-mediated cell death pathways do not contribute to muscle fibre death in dystrophinopathies

There is evidence that apoptotic cell death mechanisms contribute to muscle fibre loss in dystrophinopathies, but little knowledge about the activators of the final degrading caspase cascade in muscle fibre apoptosis. As mitochondria-related activation of this caspase cascade, through e.g. APAF-1, could not be proven in dystrophin-deficient muscle, this study searches for other prospective candidates that may directly trigger apoptotic cell degradation by mitochondria-independent pathways involving the interaction of tumour necrosis factor-alpha (TNF-alpha) and TRAIL with death receptors and subsequent activation of caspase-8. The expression of TNF-alpha, TNF-R1, TRAIL, NF-(kappa)B and caspase-8 were studied in muscle biopsy specimens from 14 patients with a dystrophinopathy [10 Duchenne muscular dystrophies (DMD), 2 Becker MD, and 2 DMD carriers] by immunohistochemistry and Western blotting. In all types of dystrophinopathies, necrotic muscle fibres undergoing myophagocytosis displayed strong expression of TNF-alpha, TNF-R1, and TRAIL, which, however, was attributed to phagocytosing cells and not to the muscle fibres themselves. There was no up-regulation in normal-shaped or atrophic non-necrotic muscle fibres, or in intact muscle fibre segments adjacent to segmental necrosis and myophagocytosis. The expression profiles of caspase-8 and NF-(kappa)B resembled that of normal control muscle. There were likewise no significant differences in the Western blot analyses between normal control and dystrophin-deficient muscle. Based on these findings, a contribution of TNF-alpha or TRAIL-mediated cell death pathways to muscle fibre apoptosis or necrosis in dystrophinopathies could not be confirmed.

Muscle-fiber apoptosis in neuromuscular diseases

Muscle-fiber loss is a characteristic of many progressive neuromuscular disorders. Over the past decade, identification of a growing number of apoptosis-associated factors and events in pathological skeletal muscle provided increasing evidence that apoptotic cell-death mechanisms account significantly for muscle-fiber atrophy and loss in a wide spectrum of neuromuscular disorders. It became obvious that there is not one specific pathway for muscle fibers to undergo apoptotic degradation. In contrast, certain neuromuscular diseases seem to involve characteristic expression patterns of apoptosis-related factors and pathways. Furthermore, there are some characteristics of muscle-fiber apoptosis that rely on the muscle fiber itself as an extremely specified cell type. Multinucleated muscle fibers with successive muscle-fiber segments controlled by individual nuclei display some specifics different from apoptosis of mononucleated cells. This review focuses on the expression patterns of apoptosis-associated factors in different primary and secondary neuromuscular disorders and gives a synopsis of current knowledge.

Human immunodeficiency virus 1 favors the persistence of infection by activating macrophages through TNF

Macrophages play a major role in HIV-1 persistence. In the present paper, we demonstrate that the absence of apoptosis in HIV-1-infected primary human monocyte-differentiated macrophages (MDM) correlates with an increase in anti-apoptotic (Bcl-2 and Bcl-x(L)) and a decrease in pro-apoptotic (Bax and Bad) proteins. This is associated with macrophage activation as shown by tumor necrosis factor (TNF) production and NF-kappaB activation upon infection. TNF production was shown to be involved in the upregulation of Bcl-2 and Bcl-x(L) because this increase was abolished by an anti-TNF anti-serum or an inhibitor of TNF synthesis. In parallel, inhibition of TNF production induced an increase in the number of apoptotic cells. Furthermore, using an inhibitor of NF-kappaB activation, we demonstrated that TNF-induced upregulation of Bcl-x(L) and Bcl-2 occurs, respectively, through a NF-kappaB-dependent and an NF-kappaB-independent pathway.

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.

The zinc finger mutation C417R of I-kappa B kinase gamma impairs lipopolysaccharide- and TNF-mediated NF-kappa B activation through inhibiting phosphorylation of the I-kappa B kinase beta activation loop

The activation of the I-kappaB kinase (IKK) complex by TNF or LPS stimulates phosphorylation and degradation of I-kappaBalpha, leading to the nuclear translocation of NF-kappaB. The IKK complex is mainly composed of two catalytic subunits, IKKalpha and IKKbeta, and a chaperon subunit IKKgamma. Although IKKgamma does not have catalytic activity, it is essential for IKK activation induced by multiple stimuli. Importantly, the key residue cysteine 417 at the zinc finger domain of IKKgamma has been found to be mutated to arginine (IKKgammaC417R) in a human genetic disorder called the anhydrotic ectodermal dysplasia with immunodeficiency. To understand the underlying mechanisms of immunodeficiency, we examined whether the IKKgammaC417R mutant modified IKK activation and NF-kappaB transcription stimulated by LPS or TNF in human monocytes. We found that overexpression of IKKgammaC417R severely impaired LPS- and TNF-induced I-kappaBalpha phosphorylation and degradation in a dominant-negative fashion. Also, LPS- and TNF-induced NF-kappaB transcription was inhibited by IKKgammaC417R. The reconstitution of IKKgamma, but not IKKgammaC417R, in IKKgamma-deficient cells restored NF-kappaB signaling, indicating the zinc finger structure of IKKgamma plays a key role in IKK activation. Moreover, C417R mutation in IKKgamma abolished both LPS- and TNF-induced phosphorylation of the activation loop of IKKbeta. Collectively, our results indicated that the zinc finger structure of IKKgamma plays a key role in LPS- and TNF-induced NF-kappaB activation. The anhydrotic ectodermal dysplasia with immunodeficiency patients' immunodeficiency may be associated with NF-kappaB defect in response to bacterial stimulation.

Xenopus Death Receptor-M1 and -M2, New Members of the Tumor Necrosis Factor Receptor Superfamily, Trigger Apoptotic Signaling by Differential Mechanisms

Signaling through the tumor necrosis factor receptor (TNFR) superfamily can lead to apoptosis or promote cell survival, proliferation, and differentiation. A subset of this family, including TNFR1 and Fas, signals cell death via an intracellular death domain and therefore is termed the death receptor (DR) family. In this study, we identified new members of the DR family, designated xDR-M1 and xDR-M2, in Xenopus laevis. The two proteins, which show high homology (71.7% identity), have characteristics of the DR family, that is, three cysteine-rich domains, a transmembrane domain, and a death domain. To elucidate how members of xDR-M subfamily regulate cell death and survival, we examined the intracellular signaling mediated by these receptors in 293T and A6 cells. Overexpression of xDR-M2 induced apoptosis and activated caspase-8, c-Jun N-terminal kinase, and nuclear factor-kappaB, although its death domain to a greater extent than did that of xDR-M1 in 293T cells. A caspase-8 inhibitor potently blocked this apoptosis induced by xDR-M2. In contrast, xDR-M1 showed a greater ability to induce apoptosis through its death domain than did xDR-M2 in A6 cells. Interestingly, a general serine protease inhibitor, but not the caspase-8 inhibitor, blocked the xDR-M1-induced apoptosis. These results imply that activation of caspase-8 or serine protease(s) may be required for the xDR-M2- or xDR-M1-induced apoptosis, respectively. Although xDR-M1 and xDR-M2 are very similar to each other, the difference in their death domains may result in diverse signaling, suggesting distinct roles of xDR-M1 and xDR-M2 in cell death or survival.

Expression of SCC-S2, an antiapoptotic molecule, correlates with enhanced proliferation and tumorigenicity of MDA-MB 435 cells

SCC-S2/GG2-1/NDED is a recently discovered antiapoptotic molecule induced by the activation of the transcription factor NF-kappaB. Here we have examined a role of SCC-S2 in cell growth regulation in vitro and in vivo. Western blotting using an antipeptide antibody revealed endogenous SCC-S2 as a approximately 21 kDa cytosolic protein in human breast cancer cells (MDA-MB 231) and renal carcinoma cells (RCC-RS). The immunofluorescence detection method showed the cytosolic localization of FLAG-tagged human SCC-S2 in COS-1 transfectants. MDA-MB 435 human cancer cells stably transfected with the FLAG-tagged SCC-S2 cDNA exhibited increased growth rate as compared to control vector transfectants, as measured by the cell viability (>twofold; n=3; P<0.005) and thymidine-labeling procedures ( approximately sixfold; n=3; P<0.0001). SCC-S2 transfectants also displayed an increase in cell migration in collagen I as compared to control transfectants ( approximately twofold; n=3; P<0.005). In athymic mice, SCC-S2 transfectants showed significantly enhanced tumor growth as compared to control transfectants (mean tumor volumes, day 16: control, 56.86+/-19.82 mm(3); SCC-S2, 127.54+/-18.78 mm(3); n=5; P<0.03). The examination of a limited number of clinical specimens revealed higher expression levels of SCC-S2 protein in certain human tumor tissues as compared to the matched normal adjacent tissues. Taken together, the present studies demonstrate SCC-S2 as a novel oncogenic factor in cancer cells.

TRAIL and NFkappaB signaling--a complex relationship

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) or Apo2L is a ligand of the TNF family interacting with five different receptors of the TNF receptor superfamily, including two death receptors. It has attracted wide interest as a potential anticancer therapy because some recombinant soluble forms of TRAIL induce cell death predominantly in transformed cells. The nuclear factor-kappaB (NFkappaB)?Rel family of proteins are composed of a group of dimeric transcription factors that have an outstanding role in the regulation of inflammation and immunity. Control of transcription by NFkappaB proteins can be of relevance to the function of TRAIL in three ways. First, induction of antiapoptotic NFkappaB dependent genes critically determines cellular susceptibility toward apoptosis induction by TRAIL-R1, TRAIL-R2, and other death receptors. Each of the multiple of known NFkappaB inducers therefore has the potential to interfere with TRAIL-induced cell death. Second, TRAIL and some of its receptors are inducible by NFkappaB, disclosing the possibility of autoamplifying TRAIL signaling loops. Third, the TRAIL death receptors can activate the NFkappaB pathway. This chapter summarizes basic knowledge regarding the understanding of the NFkappaB pathway and focuses on its multiple roles in TRAIL signaling.

Novel tumor necrosis factor ?-regulated genes in rheumatoid arthritis

OBJECTIVE

To determine novel genes regulated by tumor necrosis factor alpha (TNFalpha) signaling in primary rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

Oligonucleotide microarrays were used to measure gene expression levels in 6 independent replicate samples of RASFs. RASFs were transfected for 18 hours with AdIkappaB-dominant negative (AdIkappaB-DN) (n = 3) or with control AdTet expressing the reverse tetracycline trans-activator (n = 3). The cells were stimulated for 3 hours with TNFalpha, and total RNA was prepared. Several novel parametric and nonparametric methods were used to rank genes in terms of the magnitude and significance of intergroup differences. Microarray expression differences were confirmed by real-time quantitative reverse transcription-polymerase chain reaction. Small interfering RNA (siRNA) was used to specifically down-modulate microarray-identified genes to demonstrate their role in the promotion of apoptosis, proliferation, or matrix metalloproteinase (MMP) expression.

RESULTS

Blocking of NF-kappaB by AdIkappaB-DN was associated with a down-modulation of antiapoptosis genes, including BIRC-3, and several novel genes, including GG2-1, a TNFalpha-inducible FLIP-like gene. Other families of genes that were significantly down-regulated by AdIkappaB-DN included cytokines/chemokines (interleukin-1beta [IL-1beta], IL-8, IL-15, and RANTES), adhesion molecule (vascular cell adhesion molecule 1, intercellular adhesion molecule 1), and unique genes that have not previously been reported to be regulated by TNFalpha in RA. Inhibition of the GG2-1 gene using the siRNA technique resulted in significantly enhanced apoptosis, decreased proliferation, and decreased production of MMP-1 in TNFalpha-stimulated RASFs.

CONCLUSION

These studies provide a comprehensive analysis of genes that are differentially regulated by TNFalpha signaling and NF-kappaB nuclear translocation in RASFs and demonstrate methods for confirming the expression and functional significance of such genes.

The death effector domain protein family

Apoptosis signaling is regulated and executed by specialized proteins that often carry protein/protein interaction domains. One of these domains is the death effector domain (DED) that is predominantly found in components of the death-inducing signaling complex, which forms at the members of the death receptor family following their ligation. Both proapoptotic- and antiapoptotic-DED-containing proteins have been identified, which makes these proteins exquisitely suited to the regulation of apoptosis. Aside from their pivotal role in the control of the apoptotic program, DED-containing proteins have recently been demonstrated to exert their influence on other cellular processes as well, including cell proliferation. These data highlight the multiple roles for the members of this family, suggesting that they are suited to control both life and death decisions of cells. Additionally, because they can act proapoptotically, antiapoptotically, or in the regulation of the cell cycle, this family of proteins may be excellent candidates for cancer therapy targets. Oncogene (2003) 22, 8634-8644. doi:10.1038/sj.onc.1207103

Zoledronate sensitizes endothelial cells to tumor necrosis factor-induced programmed cell death: evidence for the suppression of sustained activation of focal adhesion kinase and protein kinase B/Akt

Bisphosphonates are potent inhibitors of osteoclast function widely used to treat conditions of excessive bone resorption, including tumor bone metastases. Recent evidence indicates that bisphosphonates have direct cytotoxic activity on tumor cells and suppress angiogenesis, but the associated molecular events have not been fully characterized. In this study we investigated the effects of zoledronate, a nitrogen-containing bisphosphonate, and clodronate, a non-nitrogen-containing bisphosphonate, on human umbilical vein endothelial cell (HUVEC) adhesion, migration, and survival, three events essential for angiogenesis. Zoledronate inhibited HUVEC adhesion mediated by integrin alphaVbeta3, but not alpha5beta1, blocked migration and disrupted established focal adhesions and actin stress fibers without modifying cell surface integrin expression level or affinity. Zoledronate treatment slightly decreased HUVEC viability and strongly enhanced tumor necrosis factor (TNF)-induced cell death. HUVEC treated with zoledronate and TNF died without evidence of enhanced annexin-V binding, chromatin condensation, or nuclear fragmentation and caspase dependence. Zoledronate inhibited sustained phosphorylation of focal adhesion kinase (FAK) and in combination with TNF, with and without interferon (IFN) gamma, of protein kinase B (PKB/Akt). Constitutive active PKB/Akt protected HUVEC from death induced by zoledronate and TNF/IFNgamma. Phosphorylation of c-Src and activation of NF-kappaB were not affected by zoledronate. Clodronate had no effect on HUVEC adhesion, migration, and survival nor did it enhanced TNF cytotoxicity. Taken together these data demonstrate that zoledronate sensitizes endothelial cells to TNF-induced, caspase-independent programmed cell death and point to the FAK-PKB/Akt pathway as a novel zoledronate target. These results have potential implications to the clinical use of zoledronate as an anti-angiogenic or anti-cancer agent.

Mechanism of cell death induced by the novel enzyme-prodrug combination, nitroreductase/CB1954, and identification of synergism with 5-fluorouracil

Virus-directed enzyme prodrug therapy (VDEPT) utilising the bacterial enzyme nitroreductase delivered by a replication-defective adenovirus vector to activate the prodrug CB1954 is a promising strategy currently undergoing clinical trials in patients with a range of cancers. An understanding of the mechanism of tumour cell death induced by activated CB1954 will facilitate this clinical development. Here, we report that activated CB1954 kills cells predominantly by caspase-dependent apoptosis. This may have important implications for the generation of immune-mediated bystander effects. Further, the use of a replication-defective adenovirus vector to deliver nitroreductase may negatively affect cellular apoptotic pathways stimulated by activated CB1954. Finally, examination of nitroreductase/CB1954 in combination with conventional chemotherapy reveals a synergistic interaction with 5-fluorouracil. These data will facilitate the further development and future clinical trial design of this novel therapy.

IKK beta plays an essential role in the phosphorylation of RelA/p65 on serine 536 induced by lipopolysaccharide

Activation of the I kappa B kinase (IKK) complex by LPS induces phosphorylation and degradation of I kappa B alpha, leading to the nuclear translocation of NF-kappa B. Although it is essential for NF-kappa B activation, emerging evidence has indicated that the nuclear translocation of NF-kappa B is not sufficient to activate NF-kappa B-dependent transcription. Here, we reported that LPS induced the phosphorylation of the p65 trans-activation domain on serine 536 in monocytes/macrophages. Using mouse embryonic fibroblasts lacking either IKK alpha or IKK beta, we found that IKK beta played an essential role in LPS-induced p65 phosphorylation on serine 536, while IKK alpha was partially required for the p65 phosphorylation. The LPS-induced p65 phosphorylation on serine 536 was independent of the phosphatidylinositol 3'-kinase/Akt signaling pathway. Furthermore, we found that the phosphorylation on serine 536 increased the p65 transcription activity. In summary, our results demonstrate that IKK beta plays an essential role in the LPS-induced p65 phosphorylation on serine 536, which may represent a mechanism to regulate the NF-kappa B transcription activity by LPS.

Neuroprotective effects of IGF-I against TNFalpha-induced neuronal damage in HIV-associated dementia

Human immunodeficiency virus type 1 (HIV-1) infection often results in disorders of the central nervous system, including HIV-associated dementia (HAD). It is suspected that tumor necrosis factor-alpha (TNFalpha) released by activated and/or infected macrophages/microglia plays a role in the process of neuronal damage seen in AIDS patients. In light of earlier studies showing that the activation of the insulin-like growth factor I receptor (IGF-IR) exerts a strong neuroprotective effect, we investigated the ability of IGF-I to protect neuronal cells from HIV-infected macrophages. Our results demonstrate that the conditioned medium from HIV-1-infected macrophages, HIV/CM, causes loss of neuronal processes in differentiated PC12 and P19 neurons and that these neurodegenerative effects are associated with the presence of TNFalpha. Furthermore, we demonstrate that IGF-I rescues differentiated neurons from both HIV/CM and TNFalpha-induced damage and that IGF-I-mediated neuroprotection is strongly enhanced by overexpression of the wt IGF-IR cDNA and attenuated by the antisense IGF-IR cDNA. Finally, IGF-I-mediated antiapoptotic pathways are continuously functional in differentiated neurons exposed to HIV/CM and are likely supported by TNFalpha-mediated phosphorylation of I(kappa)B. All together these results suggest that the balance between TNFalpha and IGF-IR signaling pathways may control the extent of neuronal injury in this HIV-related experimental setting.

THP-1 cell apoptosis in response to Mycobacterial infection

We previously reported that Mycobacterium tuberculosis infection primes human alveolar macrophages (HAM) for tumor necrosis factor alpha (TNF-alpha)-mediated apoptosis and that macrophage apoptosis is associated with killing internalized bacilli. Virulent mycobacterial strains elicit much less apoptosis than attenuated strains, implying that apoptosis is a defense against intracellular infection. The present study evaluated the potential for phorbol myristate acetate-differentiated THP-1 cells to mimic this response of primary macrophages. Consistent with the behavior of alveolar macrophages, attenuated M. tuberculosis H37Ra and Mycobacterium bovis BCG strongly induce THP-1 apoptosis, which requires endogenous TNF. THP-1 apoptosis is associated with reduced viability of infecting BCG. In contrast, virulent wild-type M. tuberculosis H37Rv and M. bovis do not increase THP-1 apoptosis over baseline. BCG induced early activation of caspase 10 and 9, followed by caspase 3. In contrast, wild-type M. bovis infection failed to activate any caspases in THP-1 cells. BCG-induced THP-1 apoptosis is blocked by retroviral transduction with vectors expressing crmA but not bcl-2. We conclude that differentiated THP-1 cells faithfully model the apoptosis response of HAM. Analysis of the THP-1 cell response to infection with virulent mycobacteria suggests that TNF death signals are blocked proximal to initiator caspase activation, at the level of TNF receptor 1 or its associated intracytoplasmic adaptor complex. Interference with TNF death signaling may be a virulence mechanism that allows M. tuberculosis to circumvent innate defenses leading to apoptosis of infected host cells.

c-Myc sensitizes cells to tumor necrosis factor-mediated apoptosis by inhibiting nuclear factor kappa B transactivation

Nuclear factor kappaB (NF-kappaB) plays a key role in suppression of tumor necrosis factor (TNF)-mediated apoptosis by inducing a variety of anti-apoptotic genes. Expression of c-Myc has been shown to sensitize cells to TNF-mediated apoptosis by inhibiting NF-kappaB activation. However, the precise step in the NF-kappaB signaling pathway and apoptosis modified by c-Myc has not been identified. Using the inducible c-MycER system and c-Myc null fibroblasts, we found that expression of c-Myc inhibited NF-kappaB activation by interfering with RelA/p65 transactivation but not nuclear translocation of NF-kappaB. Activation of c-Myc promoted TNF-induced release of cytochrome c from mitochondria to the cytosol because of the inhibition of NF-kappaB. Furthermore, we found that NF-kappaB-inducible gene A1 was attenuated by expression of c-Myc and that the restoration of A1 expression suppressed c-Myc-induced TNF sensitization. Our results elucidate the molecular mechanisms by which c-Myc increases cell susceptibility to TNF-mediated apoptosis, indicating that c-Myc may exhibit its pro-apoptotic activities by repression of cell survival genes.

Wnt signaling promotes oncogenic transformation by inhibiting c-Myc-induced apoptosis

Aberrant activation of the Wnt/beta-catenin signaling pathway is associated with numerous human cancers and often correlates with the overexpression or amplification of the c-myc oncogene. Paradoxical to the cellular transformation potential of c-Myc is its ability to also induce apoptosis. Using an inducible c-MycER expression system, we found that Wnt/beta-catenin signaling suppressed apoptosis by inhibiting c-Myc-induced release of cytochrome c and caspase activation. Both cyclooxygenase 2 and WISP-1 were identified as effectors of the Wnt-mediated antiapoptotic signal. Soft agar assays showed that neither c-Myc nor Wnt-1 alone was sufficient to induce cellular transformation, but that Wnt and c-Myc coordinated in inducing transformation. Furthermore, coexpression of Wnt-1 and c-Myc induced high-frequency and rapid tumor growth in nude mice. Extensive apoptotic bodies were characteristic of c-Myc-induced tumors, but not tumors induced by coactivation of c-Myc and Wnt-1, indicating that the antiapoptotic function of Wnt-1 plays a critical role in the synergetic action between c-Myc and Wnt-1. These results elucidate the molecular mechanisms by which Wnt/beta-catenin inhibits apoptosis and provide new insight into Wnt signaling-mediated oncogenesis.