NF-kappaB in cancer: a marked target

The AKT/IκB kinase pathway promotes angiogenic/metastatic gene expression in colorectal cancer by activating nuclear factor-κB and β-catenin

Our laboratory has delineated that the phosphatidylinositol 3' kinase (PI3K)/AKT/I kappa B kinase (IKK) pathway positively regulates NF kappa B and beta-catenin, both important transcriptional regulators in colorectal cancer (CRC). Therefore, we investigated the effect of inhibiting the PI3K/AKT/IKK alpha pathway in regulating the inappropriate constitutive activation of NF kappa B and beta-catenin in CRC cell lines. SW480 and RKO CRC cell lines demonstrate constitutive activation of AKT as well as both NF kappa B- and beta-catenin-dependent transcription. The constitutive activation of NF kappa B- and beta-catenin-dependent transcription is inhibited by transiently transfecting either kinase dead (KD) IKK alpha, which blocks IKK alpha kinase activity, KD AKT, which blocks AKT activity, or wildtype (WT) PTEN, which inhibits PI3K and AKT activity. The ability of KD IKK alpha, KD AKT or WT PTEN to decrease beta-catenin-dependent transcription is independent of their effects on NF kappa B. Inducible expression of either KD IKK alpha or WT PTEN strongly inhibits both the constitutive NF kappa B- and beta-catenin-dependent promoter and endogenous gene activation. Targeted array-based gene expression analysis of this inducible system reveals that many of the genes downregulated upon inhibition of this pathway are involved in tumor angiogenesis and metastasis. The activation of this pathway and the expression of the three most repressed genes was further analysed in samples of CRC. These results indicate a role of this pathway in controlling gene expression important in tumor progression and metastasis.

Proteasome inhibitor PS-341 induces apoptosis through induction of endoplasmic reticulum stress-reactive oxygen species in head and neck squamous cell carcinoma cells

PS-341, also known as Velcade or Bortezomib, represents a new class of anticancer drugs which has been shown to potently inhibit the growth and/or progression of human cancers, including head and neck squamous cell carcinoma (HNSCC). Although it has been logically hypothesized that NF-kappaB is a major target of PS-341, the underlying mechanism by which PS-341 inhibits tumor cell growth is unclear. Here we found that PS-341 potently activated the caspase cascade and induced apoptosis in human HNSCC cell lines. Although PS-341 could inhibit NF-kappaB activation, the inhibition of NF-kappaB was not sufficient to initiate apoptosis in HNSCC cells. Using biochemical and microarray approaches, we found that proteasome inhibition by PS-341 induced endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) in HNSCC cells. The inhibition of ROS significantly suppressed caspase activation and apoptosis induced by PS-341. Consistently, PS-341 could not induce the ER stress-ROS in PS-341-resistant HNSCC cells. Taken together, our results suggest that in addition to the abolishment of the prosurvival NF-kappaB, PS-341 might directly induce apoptosis by activating proapoptotic ER stress-ROS signaling cascades in HNSCC cells, providing novel insights into the PS-341-mediated antitumor activity.

The nuclear factor kappaB subunits RelA/p65 and c-Rel potentiate but are not required for Ras-induced cellular transformation

Extensive data indicate that oncoproteins, such as oncogenic H-Ras, initiate signal transduction cascades that ultimately lead to the activation of specific transcription factors. We and others have previously demonstrated that Ras activates the inherent transcriptional activation function of the transcription factor nuclear factor kappaB (NF-kappaB). Supportive of the importance of NF-kappaB in transformation, Ras-induced cellular transformation can be suppressed by expression of IkappaBalpha, an inhibitor of NF-kappaB, or by dominant-negative forms of the upstream activator IkappaB kinase (IKK). However, conclusive evidence for a requirement for NF-kappaB subunits in oncogenic transformation has not been reported. Furthermore, there is little understanding of the gene targets controlled by NF-kappaB that might support oncogenic conversion. The data presented here demonstrate that, although both p65 and c-Rel enhance the frequency of Ras-induced cellular transformation, these NF-kappaB subunits are not essential for Ras to transform spontaneously immortalized murine fibroblasts. Microarray analysis identified a set of genes induced by Ras that is dependent on NF-kappaB for their expression and that likely play contributory roles in promoting Ras-induced oncogenic transformation.

Sustained activation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase pathways by hepatitis B virus X protein mediates apoptosis via induction of Fas/FasL and tumor necrosis factor (TNF) receptor 1/TNF-alpha expression

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

NF-kappaB protects lung epithelium against hyperoxia-induced nonapoptotic cell death-oncosis

Prolonged exposure to hyperoxia induces pulmonary epithelial cell death and acute lung injury. Although both apoptotic and nonapoptotic morphologies are observed in hyperoxic animal lungs, nonapoptotic cell death had only been recorded in transformed lung epithelium cultured in hyperoxia. To test whether the nonapoptotic characteristics in hyperoxic animal lungs are direct effects of hyperoxia, the mode of cell death was determined both morphologically and biochemically in human primary lung epithelium exposed to 95% O(2). In contrast to characteristics observed in apoptotic cells, hyperoxia induced swelling of nuclei and an increase in cell size, with no evidence for any augmentation in the levels of either caspase-3 activity or annexin V incorporation. These data suggest that hyperoxia can directly induce nonapoptotic cell death in primary lung epithelium. Although hyperoxia-induced nonapoptotic cell death was associated with NF-kappaB activation, it is unknown whether NF-kappaB activation plays any causal role in nonapoptotic cell death. This study shows that inhibition of NF-kappaB activation can accelerate hyperoxia-induced epithelial cell death in both primary and transformed lung epithelium. Corresponding to the reduced cell survival in hyperoxia, the levels of MnSOD were also low in NF-kappaB-deficient cells. These results demonstrate that NF-kappaB protects lung epithelial cells from hyperoxia-induced nonapoptotic cell death.

Cell signaling pathways altered by natural chemopreventive agents

Epidemiological studies have indicated a significant difference in the incidence of cancers among ethnic groups, who have different lifestyles and have been exposed to different environmental factors. It has been estimated that more than two-thirds of human cancers, which are contributed by mutations in multiple genes, could be prevented by modification of lifestyle including dietary modification. The consumption of fruits, soybean and vegetables has been associated with reduced risk of several types of cancers. The in vitro and in vivo studies have demonstrated that some dietary components such as isoflavones, indole-3-carbinol (I3C), 3,3'-diindolylmethane (DIM), curcumin, (-)-epigallocatechin-3-gallate (EGCG), apigenin, etc., have shown inhibitory effects on human and animal cancers, suggesting that they may serve as chemopreventive agents. Experimental studies have also revealed that these components regulate the molecules in the cell signal transduction pathways including NF-kappaB, Akt, MAPK, p53, AR, and ER pathways. By modulating cell signaling pathways, these components, among other mechanisms, activate cell death signals and induce apoptosis in precancerous or cancer cells, resulting in the inhibition of cancer development and/or progression. This article reviews current studies regarding the effects of natural chemopreventive agents on cancer-related cell signaling pathways and provides comprehensive knowledge of the biological and molecular roles of chemopreventive agents in cancer cells.

N-Acetyl-l-cysteine Enhances Apoptosis through Inhibition of Nuclear Factor-κB in Hypoxic Murine Embryonic Fibroblasts

In this study, we investigated the role of reduced glutathione (GSH) and nuclear factor-kappaB (NFkappaB) in hypoxia-induced apoptosis. Hypoxia caused p53-dependent apoptosis in murine embryonic fibroblasts transfected with Ras and E1A. N-Acetyl-l-cysteine (NAC) but not other antioxidants, such as the vitamin E analog trolox and epigallocatechin-3-gallate, enhanced hypoxia-induced caspase-3 activation and apoptosis. NAC also enhanced hypoxia-induced apoptosis in two human cancer cell lines, MIA PaCa-2 pancreatic cancer cells and A549 lung carcinoma cells. In murine embryonic fibroblasts, all three antioxidants blocked hypoxia-induced reactive oxygen species formation. NAC did not enhance hypoxia-induced cytochrome c release but did enhance poly-(ADP ribose) polymerase cleavage, indicating that NAC acted at a post-mitochondrial level. NAC-mediated enhancement of apoptosis was mimicked by incubating cells with GSH monoester, which increased intracellular GSH similarly to NAC. Hypoxia promoted degradation of an inhibitor of kappaB(IkappaBalpha), NFkappaB-p65 translocation into the nucleus, NFkappaB binding to DNA, and subsequent transactivation of NFkappaB, which increased X chromosome-linked inhibitor of apoptosis protein levels. NAC failed to block degradation by IkappaBalpha and sequestration of the p65 subunit of NFkappaB to the nucleus. However, NAC did abrogate hypoxia-induced NFkappaB binding to DNA, NFkappaB-dependent gene expression, and induction of X chromosome-linked inhibitor of apoptosis protein. In conclusion, NAC enhanced hypoxic apoptosis by a mechanism apparently involving GSH-dependent suppression of NFkappaB transactivation.

Negative regulation of JNK signaling by the tumor suppressor CYLD

CYLD is a tumor suppressor that is mutated in familial cylindromatosis, an autosomal dominant predisposition to multiple tumors of the skin appendages. Recent studies suggest that transfected CYLD has deubiquitinating enzyme activity and inhibits the activation of transcription factor NF-kappaB. However, the role of endogenous CYLD in regulating cell signaling remains poorly defined. Here we report a critical role for CYLD in negatively regulating the c-Jun NH(2)-terminal kinase (JNK). CYLD knockdown by RNA interference results in hyper-activation of JNK by diverse immune stimuli, including tumor necrosis factor-alpha, interleukin-1, lipopolysaccharide, and an agonistic anti-CD40 antibody. The JNK-inhibitory function of CYLD appears to be specific for immune receptors because the CYLD knockdown has no significant effect on stress-induced JNK activation. Consistently, CYLD negatively regulates the activation of MKK7, an upstream kinase known to mediate JNK activation by immune stimuli. We further demonstrate that CYLD also negatively regulates IkappaB kinase, although this function of CYLD is seen in a receptor-dependent manner. These findings identify the JNK signaling pathway as a major downstream target of CYLD and suggest a receptor-dependent role of CYLD in regulating the IkappaB kinase pathway.

Role of F-box protein betaTrcp1 in mammary gland development and tumorigenesis

The F-box protein betaTrcp1 controls the stability of several crucial regulators of proliferation and apoptosis, including certain inhibitors of the NF-kappaB family of transcription factors. Here we show that mammary glands of betaTrcp1(-/-) female mice display a hypoplastic phenotype, whereas no effects on cell proliferation are observed in other somatic cells. To investigate further the role of betaTrcp1 in mammary gland development, we generated transgenic mice expressing human betaTrcp1 targeted to epithelial cells under the control of the mouse mammary tumor virus (MMTV) long terminal repeat promoter. Compared to controls, MMTV betaTrcp1 mammary glands display an increase in lateral ductal branching and extensive arrays of alveolus-like protuberances. The mammary epithelia of MMTV betaTrcp1 mice proliferate more and show increased NF-kappaB DNA binding activity and higher levels of nuclear NF-kappaB p65/RelA. In addition, 38% of transgenic mice develop tumors, including mammary, ovarian, and uterine carcinomas. The targeting of betaTrcp1 to lymphoid organs produces no effects on these tissues. In summary, our results support the notion that betaTrcp1 positively controls the proliferation of breast epithelium and indicate that alteration of betaTrcp1 function and expression may contribute to malignant behavior of breast tumors, at least in part through NF-kappaB transactivation.

Activation of nuclear factor kappaB In vivo selectively protects the murine small intestine against ionizing radiation-induced damage

Exposure of mice to total body irradiation induces nuclear factor kappaB (NFkappaB) activation in a tissue-specific manner. In addition to the spleen, lymph nodes, and bone marrow, the tissues that exhibit NFkappaB activation now include the newly identified site of the intestinal epithelial cells. NFkappaB activated by total body irradiation mainly consists of NFkappaB p50/RelA heterodimers, and genetically targeted disruption of the NFkappaB p50 gene in mice significantly decreased the activation. By comparing tissue damage and lethality in wild-type and NFkappaB p50 knockout (p50-/-) mice after they were exposed to increasing doses of total body irradiation, we additionally examined the role of NFkappaB activation in total body irradiation-induced tissue damage. The results show that p50-/- mice are more sensitive to total body irradiation-induced lethality than wild-type mice (LD50/Day 7: wild-type = 13.12 Gy versus p50-/- = 7.75 Gy and LD50/Day 30: wild-type = 9.31 Gy versus p50-/- = 7.81 Gy). The increased radiosensitivity of p50-/- mice was associated with an elevated level of apoptosis in intestinal epithelial cells and decreased survival of the small intestinal crypts compared with wild-type mice (P < 0.01). In addition, RelA/TNFR1-deficient (RelA/TNFR1-/-) mice also exhibited a significant increase in intestinal epithelial cell apoptosis after they were exposed to total body irradiation as compared with TNFR1-deficient (TNFR1-/-) mice (P < 0.01). In contrast, no significant increase in total body irradiation-induced apoptosis or tissue injury was observed in bone marrow cells, spleen lymphocytes, and the liver, heart, lung, and kidney of p50-/- mice in comparison with wild-type mice. These findings indicate that activation of NFkappaB selectively protects the small intestine against ionizing radiation-induced damage.

Identification of a novel mechanism of NF-kappaB inactivation by progesterone through progesterone receptors in Hec50co poorly differentiated endometrial cancer cells: induction of A20 and ABIN-2

OBJECTIVE

Nuclear factor kappa B (NFkappaB) is a strong anti-apoptotic factor, which is constitutively active in human endometrial cancer cells. Progesterone is the principal growth inhibitory hormone in the endometrial epithelium and promotes apoptosis. To identify the pathways through which progesterone controls NFkappaB function, we explored its genomic and non-genomic effects in endometrial cancer cells.

METHODS

PR-negative Hec50co endometrial cancer cells were engineered to express high levels of the A or B isoform of PR (PRA or PRB) by adenoviral infection. Cells were treated with progesterone or vehicle alone, and RNA was isolated. Affymetrix microarrays were performed and transcriptional control of the genes of highest interest was confirmed by semi-quantitative RT-PCR. To assess the non-genomic effects of PR on inflammation associated with NF-kappaB, electromobility shift assays (EMSAs) were performed.

RESULTS

Expression analysis demonstrated a significant effect of progesterone after 12- and 24-h treatment on several genes; in particular, A20 and ABIN-2 were induced through PRB. These factors bind in a complex and inhibit NFkappaB transcriptional activity. In addition, EMSAs revealed the complete inhibition of NFkappaB dimer binding to DNA by both PRA and PRB.

CONCLUSIONS

Progesterone is the principal differentiating hormone in the endometrium. We have now identified several down-stream pathways of action, one of which is the control of genes involved in NFkappaB activity. The tumorigenic inflammatory and anti-apoptotic effects of NFkappaB are inhibited by progesterone/PRB through the transcriptional control of binding proteins A20 and ABIN-2. This pathway offers interesting targets for future therapeutic development.

NF-kappaB functions as a tumour promoter in inflammation-associated cancer

The causes of sporadic human cancer are seldom recognized, but it is estimated that carcinogen exposure and chronic inflammation are two important underlying conditions for tumour development, the latter accounting for approximately 20% of human cancer. Whereas the causal relationship between carcinogen exposure and cancer has been intensely investigated, the molecular and cellular mechanisms linking chronic inflammation to tumorigenesis remain largely unresolved. We proposed that activation of the nuclear factor kappaB (NF-kappaB), a hallmark of inflammatory responses that is frequently detected in tumours, may constitute a missing link between inflammation and cancer. To test this hypothesis, we studied the Mdr2-knockout mouse strain, which spontaneously develops cholestatic hepatitis followed by hepatocellular carcinoma, a prototype of inflammation-associated cancer. We monitored hepatitis and cancer progression in Mdr2-knockout mice, and here we show that the inflammatory process triggers hepatocyte NF-kappaB through upregulation of tumour-necrosis factor-alpha (TNFalpha) in adjacent endothelial and inflammatory cells. Switching off NF-kappaB in mice from birth to seven months of age, using a hepatocyte-specific inducible IkappaB-super-repressor transgene, had no effect on the course of hepatitis, nor did it affect early phases of hepatocyte transformation. By contrast, suppressing NF-kappaB inhibition through anti-TNFalpha treatment or induction of IkappaB-super-repressor in later stages of tumour development resulted in apoptosis of transformed hepatocytes and failure to progress to hepatocellular carcinoma. Our studies thus indicate that NF-kappaB is essential for promoting inflammation-associated cancer, and is therefore a potential target for cancer prevention in chronic inflammatory diseases.

CD95 ligand induces motility and invasiveness of apoptosis-resistant tumor cells

The apoptosis-inducing death receptor CD95 (APO-1/Fas) controls the homeostasis of many tissues. Despite its apoptotic potential, most human tumors are refractory to the cytotoxic effects of CD95 ligand. We now show that CD95 stimulation of multiple apoptosis-resistant tumor cells by CD95 ligand induces increased motility and invasiveness, a response much less efficiently triggered by TNFalpha or TRAIL. Three signaling pathways resulting in activation of NF-kappaB, Erk1/2 and caspase-8 were found to be important to this novel activity of CD95. Gene chip analyses of a CD95-stimulated tumor cell line identified a number of potential survival genes and genes that are known to regulate increased motility and invasiveness of tumor cells to be induced. Among these genes, urokinase plasminogen activator was found to be required for the CD95 ligand-induced motility and invasiveness. Our data suggest that CD95L, which is found elevated in many human cancer patients, has tumorigenic activities on human cancer cells. This could become highly relevant during chemotherapy, which can cause upregulation of CD95 ligand by both tumor and nontumor cells.

An introduction to the molecular mechanisms of apoptosis

Apoptosis is a type of cell death that has been observed and studied for more than a century. The process of apoptosis was described as "programmed cell death" in 1964, and the term apoptosis, from a Greek word meaning "to fall away from" and describing the fall of dead leaves from trees in autumn, was only coined in 1972. During the last 30 years, this type of cell death has been extensively investigated and the molecular mechanisms underlying this cell suicide well characterized. Apoptosis is a physiological phenomenon necessary to tissue and body genesis and homeostasis, but defects in its regulation may cause numerous diseases, including cancer. Investigating the mechanisms of apoptosis is thus important to discover new cellular regulators that could be potential targets for new death-inducing drugs.

Active repression of antiapoptotic gene expression by RelA(p65) NF-kappa B

With the emerging role of NF-kappa B in cancer it is important that its responses to stimuli relevant to tumor progression and therapy are understood. Here, we demonstrate that NF-kappa B induced by cytotoxic stimuli, such as ultraviolet light (UV-C) and the chemotherapeutic drugs daunorubicin/doxorubicin, is functionally distinct to that seen with the inflammatory cytokine TNF and is an active repressor of antiapoptotic gene expression. Surprisingly, these effects are mediated by the RelA(p65) NF-kappa B subunit. Furthermore, UV-C and daunorubicin inhibit TNF-induced NF-kappa B transactivation, indicating that this is a dominant effect. Consistent with this, mechanistic studies reveal that UV-C and daunorubicin induce the association of RelA with histone deacetylases. RelA can therefore be both an activator and repressor of its target genes, dependent upon the manner in which it is induced. This has important implications for the role of NF-kappa B in tumorigenesis and the use of NF-kappa B inhibitors in cancer therapy.

Mechanism of processing of the NF-kappa B2 p100 precursor: identification of the specific polyubiquitin chain-anchoring lysine residue and analysis of the role of NEDD8-modification on the SCF(beta-TrCP) ubiquitin ligase

Processing of the NF-kappa B2 precursor p100 to the mature p52 subunit is regulated via a unique pathway. NF-kappa B-inducing kinase (NIK) induces I kappa B kinase alpha (IKK alpha)-mediated phosphorylation of specific serine residues in the C-terminal domain of p100, leading to recruitment of the SCF(beta-TrCP) ubiquitin ligase. We identified a single lysine residue, K855, that serves as the ubiquitin-anchoring residue required for signal-induced processing of p100. In a reconstituted system containing purified components, p100-K855R could not be ubiquitinated. In a crude extract and cells, only residual, signal-independent ubiquitination and processing were retained. Importantly, K855 is located in a site homologous to K22 that serves as an ubiquitination site in I kappa B alpha. This suggests a common recognition mechanism for the two molecules. In contrast, p105, the p100 homologue, lacks a similar Lys residue. We also demonstrate that the NEDD8 pathway is essential for the SCF(beta-TrCP) activity. In a reconstituted system, efficient ubiquitination of p100 required all three components of the pathway - E1, the UBC12 E2 and NEDD8. Experiments in reconstituted systems and in cells demonstrated that SCF(beta-TrCP), which contains a mutant Cul-1 that cannot be NEDDylated, cannot stimulate ubiquitination and processing. Similarly, dominant negative UBC12 inhibits, in a reversible manner, both ubiquitination and processing of p100.

Involvement of NF-kappa B activation in P-glycoprotein expression in vincristine-resistant human gastric cancer cells

AIM: To investigate the effect of vincristine on activation of nuclear factor-kappa B (NF-κB) and expression of p-glycoprotein (P-gp) in vincristine-resistant human gastric cancer SGC7901 cells (SGC7901/VCR) and the parent sensitive clone (SGC7901).

METHODS: NF-κB-DNA binding activity was determined by electrophoretic mobility shift assay (EMSA). Levels of inhibitory B (IB-) and P-gp were measured by cellular-ELISA. And immunocytochemistry was used to detect the translocation of P65.

RESULTS: IN comparison with the parent SGC7901 cells, the basal and vincristine-induced NF-κB-DNA binding activity at various concentrations were all higher in the SGC7901/VCR cells. Concurrent with the NF-κB activation, vincristine-induced IB- degradation and P-gp upregulation were also found to be highly enhanced in the SGC7901/VCR cells than that in the sensitive SGC7901 cells. In the SGC7901/VCR cells, the activation of NF-κB induced by vincristine showed a positive relation with the level of P-gp expression (r = 0.977, P < 0.01). And nuclear translocation of P65 occurred concomitantly with NF-κB activation. Furthermore, the inhibition of NF-κB by MG-132, a proteasome inhibitor, could reduce NF-κB activation, IB- degradation and P-gp upregulation.

CONCLUSION: The enhancement of NF-κB activation correlates with vincristine resistance and NF-κB may play an important role in the regulation of the P-gp expression.

Expression of nuclear factor-kappa B and target genes in gastric precancerous lesions and adenocarcinoma: Association with Helicobactor pylori cagA (+) infection

AIM: To examine the expression of nuclear factor kappaB (NF-κB) and its target genes in intestinal metaplasia (IM), dysplasia (DYS) and gastric carcinoma (GC) infected with Helicobacter pylori (H pylori) and to investigate the mechanism underlying H pylori cytotoxin associated gene A (cag A) infection leading to gastric adenocarcinoma.

METHODS: Expressions of NF-κB/p65 and its target genes: c-myc, cyclinD1 and bcl-xl were immunohistochemically examined in 289 cases of gastric biopsy and resection specimens from patients with IM, DYS and GC infected with H pylori. H pylori in the above mentioned tissues was detected by Warthin-Starry stain and rapid urease tests. IgG antibody to cagA in sera of the patients was measured by ELISA.

RESULTS: The positive rates of NF-κB/p65 were significantly higher in groups with cagA of IMI-II(28/33), IM III(48/52), DYSI(27/31), DYS II-III(28/32), GC(35/40) than in groups without cagA of IMI-II(4/17), IMIII(3/20), DYSI(3/20), DYSII-III(6/21), GC(10/23). The expressions of c-myc, cyclinD1, and bcl-xl were significantly higher in groups with cagA of IM III(47/52, 49/52, 46/52), DYSII-III(29/32, 26/32, 25/32) than in groups without cagA of IM III(8/20, 7/20, 5/20), DYSII-III(10/21, 8/21, 3/21), which were in conformity with the expression of NF-κB in IM III, and DYSII-III. A significantly higher expression level of NF-κB/p65, c-myc, cyclinD1 and bcl-xl was detected in intestinal type GC(27/28, 18/28, 22/28, 24/28) than in diffuse type GC(8/12, 3/12, 3/12, 6/12), respectively.

CONCLUSION: There may be two different molecular mechanisms in the occurrence of intestinal and diffuse type gastric carcinomas. Intestinal type gastric carcinoma is strongly associated with high expression of c-myc, cyclinD1 and bcl-xl through NF-κB/p65 activated by H pylori cagA. Inhibiting the activity of NF-κB is an effective and promising way to prevent intestinal type gastric carcinoma.

Molecular mimicry of the NF-κB DNA target site by a selected RNA aptamer

During the past two decades, structural and biophysical studies of DNA-protein and RNA-protein complexes have enhanced our understanding of the physico-chemical basis of nucleic acid recognition by proteins. However, it remains unclear what protein surface features are most important for nucleic acid binding and whether the same protein surface could bind specifically to both DNA and RNA. The recently described X-ray crystal structure of the transcription factor NF-kappaB p50 homodimer bound to a high-affinity RNA aptamer allows the direct comparison of NF-kappaB-RNA and NF-kappaB-DNA binding modes. The RNA aptamer, which bears no sequence homology to natural NF-kappaB DNA targets, adopts a structure with similar physico-chemical properties to kappaB DNA and contacts a common nucleic-acid-binding 'consensus surface' on the p50 homodimer.

To be, or not to be: NF-kappaB is the answer--role of Rel/NF-kappaB in the regulation of apoptosis

During their lifetime, cells encounter many life or death situations that challenge their very own existence. Their survival depends on the interplay within a complex yet precisely orchestrated network of proteins. The Rel/NF-kappaB signaling pathway and the transcription factors that it activates have emerged as critical regulators of the apoptotic response. These proteins are best known for the key roles that they play in normal immune and inflammatory responses, but they are also implicated in the control of cell proliferation, differentiation, apoptosis and oncogenesis. In recent years, there has been remarkable progress in understanding the pathways that activate the Rel/NF-kappaB factors and their role in the cell's decision to either fight or surrender to apoptotic challenge. Whereas NF-kappaB is most commonly involved in suppressing apoptosis by transactivating the expression of antiapoptotic genes, it can promote programmed cell death in response to certain death-inducing signals and in certain cell types. This review surveys our current understanding of the role of NF-kappaB in the apoptotic response and focuses on many developments since this topic was last reviewed in Oncogene 4 years ago. These recent findings shed new light on the activity of NF-kappaB as a critical regulator of apoptosis in the immune, hepatic, epidermal and nervous systems, on the mechanisms through which it operates and on its role in tissue development, homoeostasis and cancer.

Production of an Antiproliferative Furanoheliangolide by Lychnophora ericoides Cell Culture

This work reports for the first time the production a furanoheliangolide (goyazensolide) by plant cell culture. Monitoring of the goyazensolide metabolism revealed that the maximum production occurred during the lag phase of the Lychnophora ericoides callus culture. The antiproliferative activity of obtained goyazensolide was evaluated against seven cancer cell lines using MTT assay. The results revealed a potent cytotoxic activity for the furaheliangolide with IC50 values in the range of 0.06 microg/ml for CEM leukemia cells to 0.75 microg/ml for B16 melanome cells.

Effect of NF-κB, survivin, Bcl-2 and Caspase3 on apoptosis of gastric cancer cells induced by tumor necrosis factor related apoptosis inducing ligand

AIM: To study the effect of NF-κB, survivin, Bcl-2 and Caspase3 on tumor necrosis factors related apoptosis inducing ligand (TRAIL) induced apoptosis of gastric cancer cells.

METHODS: Gastric cancer cells of SGC-7901, MKN28, MKN45 and AGS lines were cultured in PRMI-1640 medium and the apoptosis rates of the cells of 4 lines were observed after treatment of tumor necrosis factors related apoptosis inducing ligand (TRAIL) with a flow cytometer. The expression of NF-κB, survivin, Bcl-2 and Caspase3 in gastric cancer cells of 4 lines was analyzed with Western blot.

RESULTS: After the gastric cancer cells were exposed to TRAIL 300 ng/mL for 24 hours, the apoptosis rate was 36.05%, 20.27%, 16.50% and 11.80% in MKN28, MKN45, AGS and SGC-7901cells respectively. Western blot revealed that the expressions of NF-κB and survivin were lower in MKN28 cells than in MKN45, AGS and SGC-7901 cells. In contrast, the expression of Caspase3 was higher in MKN28 cells than in MKN45, AGS and SGC-7901 cells.

CONCLUSION: There is a selectivity of TRAIL potency to induce apoptosis in gastric cancer cells of different cell lines. The anticancer potency of TRAIL is associated with the decreased expression of NF-κB and survivin and increased expression of Caspase3 of gastric cancer cells.

A p105-based inhibitor broadly represses NF-kappa B activities

An IkappaBalpha-based NF-kappaB super repressor (sr) has been used widely for studying genes regulated by NF-kappaB transcription factors. Repression of NF-kappaB by IkappaBalpha(sr) also facilitates tumor necrosis factor alpha-induced apoptosis in the cell. However, IkappaBalpha primarily targets RelA and c-Rel-containing complexes, leaving other NF-kappaB/Rel protein complexes, such as p50 and p52 homodimers, and RelB heterodimers uninhibited. Because these atypical NF-kappaB complexes also contribute to gene regulation and are activated in pathological conditions, broad inhibition of all NF-kappaB species is of significant pharmacological and clinical interests. We have designed, generated, and tested a p105-based NF-kappaB super repressor. We showed that p105(sr), which no longer generates p50 and undergoes signal-induced degradation, effectively inhibits all NF-kappaB activities. In addition, we also demonstrated that p105(sr) significantly enhances tumor necrosis factor alpha-mediated killing of MT1/2 skin papilloma cells where p50 homodimer activity is elevated. Our results suggest that p105(sr) is a broader range and effective NF-kappaB super repressor and can potentially be used in cells where a noncanonical NF-kappaB activity is dominant or multiple NF-kappaB activities are activated.

Overexpression of MEKK3 confers resistance to apoptosis through activation of NFkappaB

Many cancers have constitutively activated NFkappaB, the elevation of which contributes to cancer cell resistance to chemotherapeutic agent-induced apoptosis. Although mitogen-activated protein kinase/extracellular-regulated kinase kinase kinase-3 (MEKK3) has been shown to participate in the activation of NFkappaB, its relations to apoptosis and cancer are unclear. In this study, we established cell model systems to examine whether stable expression of MEKK3 could lead to increased NFkappaB activity and confer resistance to apoptosis. In addition, we investigated in breast and ovarian cancers whether MEKK3 expression may be altered and correlated with aberrant NFkappaB activity. We show that stable cell lines overexpressing MEKK3 not only had elevated levels of NFkappaB binding activity but also were more responsive to cytokine stimulation. These stable cells showed 2-4-fold higher basal expression of Bcl-2 and xIAP than the parental cells. Consistent with this increased expression of cell survival genes, MEKK3 stable cells showed reduced activation of caspases 3 and 8 and poly(ADP-ribose) polymerase cleavage and dramatically increased resistance to apoptosis induced by tumor necrosis factor-related apoptosis-inducing ligand, doxorubicin, daunorubicin, camptothecin, and paclitaxel. Intriguingly, analysis of human breast and ovarian cancers showed that a significant fraction of these samples have elevated MEKK3 protein levels with corresponding increases in NFkappaB binding activities. Thus, our results established that elevated expression of MEKK3 appears to be a frequent occurrence in breast and ovarian cancers and that overexpression of MEKK3 in cells leads to increased NFkappaB activity and increased expression of cell survival factors and ultimately contributes to their resistance to apoptosis. As such, MEKK3 may serve as a therapeutic target to control cancer cell resistance to cytokine- or drug-induced apoptosis.

The role of Notch in tumorigenesis: oncogene or tumour suppressor?

Notch signalling participates in the development of multicellular organisms by maintaining the self-renewal potential of some tissues and inducing the differentiation of others. Involvement of Notch in cancer was first highlighted in human T-cell leukaemia, fuelling the notion that aberrant Notch signalling promotes tumorigenesis. However, there is mounting evidence that Notch signalling is not exclusively oncogenic. It can instead function as a tumour suppressor.