The Rel/NF-kappaB signal transduction pathway: introduction

A novel mechanism for pergolide-induced neuroprotection: inhibition of NF-κB nuclear translocation

We previously demonstrated that the dopaminergic agonist pergolide, independently from its DA agonist activity, can exert neuroprotective effects against cell death induced in SH-SY5Y neural cells by H(2)O(2) treatment. Since oxidative stress in SH-SY5Y neural cells is known to activate the NF-kappaB pathway we tested the hypothesis that pergolide may interfere with NF-kappaB activity. Based on Western blot analysis and immunocytochemistry, pergolide was found to prevent H(2)O(2)-induced apoptosis by inhibiting NF-kappaB nuclear translocation and activation of p53 signalling pathway. Similarly, the cell-permeable SN50 peptide, which is known to block NF-kappaB nuclear translocation, prevented both H(2)O(2)-induced p53 expression and apoptosis. The mechanism of action of pergolide responsible for neuroprotection differed from that of antioxidants. In fact, Vitamin E, contrary to pergolide and SN50, rescued neuronal cells from H(2)O(2)-induced apoptosis acting upstream NF-kappaB activation, as demonstrated by the prevention of H(2)O(2)-induced IkappaB degradation. These data suggest a novel site of action of pergolide that may account for additional pharmacological properties of this drug.

NF-kappaB in pancreatic cancer

Although the genetic profile of pancreatic cancer is emerging as a result of much research, the role of specific genetic alterations that initiate tumorigenesis and produce its cardinal clinical features of locally aggressive growth, metastasis, and chemotherapy resistance remains unresolved. Recently, a number of studies have shown that the inhibition of constitutive NF-kappaB activation, one of the frequent molecular alterations in pancreatic cancer, inhibits tumorigenesis and metastasis. It also sensitizes pancreatic cancer cell lines to anticancer agent-induced apoptosis. Therefore because of the crucial role of NF-kappaB in pancreatic cancer, it is a potential target for developing novel therapeutic strategies for the disease. In vivo and in vitro models that mimic the tumorigenic phenotypes in the appropriate histological and molecular concert would be very useful for confirming the suspected role of the pancreatic cancer signature genetic lesions and better understanding the molecular basis of this disease.

Inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced tumor promotion markers in CD-1 mouse skin by oleandrin

Oleandrin, derived from the leaves of Nerium oleander, has been shown to possess anti-inflammatory and tumor cell growth-inhibitory effects. Here, we provide evidence that oleandrin could possess anti-tumor promoting effects. We determined the effect of topical application of oleandrin to CD-1 mice against l2-O-tetradecanoylphorbol-13-acetate (TPA), a widely studied skin tumor promoter, -induced conventional and novel markers of skin tumor promotion. Topical application of oleandrin (2 mg per mouse) 30 min before TPA (3.2 nmol per mouse) application onto the skin afforded significant inhibition, in a time-dependent manner, against TPA-mediated increase in cutaneous edema and hyperplasia, epidermal ornithine decarboxylase (ODC) activity and ODC and cyclooxgenase-2 (COX-2) protein expression. In search for novel markers of skin tumor promotion, we found that TPA application to mouse skin resulted, as an early event, in an increased expression of phosphatidyinositol 3-kinase (PI3K), phosphorylation of Akt at threonine308 and activation of nuclear factor kappa B (NF-kappaB). Topical application of oleandrin before TPA application to mouse skin resulted in significant reduction in TPA-induced expression of PI3K and phosphorylation of Akt, and inhibition of NF-kappaB activation. NF-kappaB is a eukaryotic transcription factor that is critically involved in regulating the expression of specific genes that participate in inflammation, apoptosis and cell proliferation. Employing Western blot analysis, we found that oleandrin application to mouse skin resulted in inhibition of TPA-induced activation of NF-kappaB, IKKalpha and phosphorylation and degradation of IkappaBalpha. Our data suggest that oleandrin could be a useful anti-tumor promoting agent because it inhibits several biomarkers of TPA-induced tumor promotion in an in vivo animal model. One might envision the use of chemopreventive agents such as oleandrin in an emollient or patch for chemoprevention or treatment of skin cancer.

Expression of NF-kappaB in prostate cancer lymph node metastases

INTRODUCTION

Nuclear factor-kappaB (NF-kappaB) is a transcription factor that transactivates genes involved in the regulation of cell growth, apoptosis, angiogenesis, and metastasis. Our aim was to assess NF-kappaB expression in lymph node (LN) metastases of prostate cancer.

METHODS

Immunohistochemical staining was performed using the p65 anti-NF-kappaB antibody. Seventy-seven paraffin-embedded LN specimens obtained from 54 prostate cancer patients were analyzed. Of the 54 patients, 32 had positive LN metastases, while 22 showed no evidence of metastasis and were considered as controls. The overall percentage of NF-kappaB-nuclear localization was assessed, as well as the intensity of staining.

RESULTS

Nuclear localization of NF-kappaB was significantly greater in the metastatic LN group compared to controls. In patients with positive-LN metastases, 84.4% showed >10% nuclear staining in tumor cells. Moreover, 64.4% of the malignant LN specimens had >10% nuclear staining in lymphocytes compared to 0% in controls. Intensity of cytoplasmic and nuclear staining was higher in the metastatic LN group than in controls (P < 0.01).

CONCLUSIONS

Nuclear localization/activation of NF-kappaB is up-regulated in prostate cancer LN metastasis. Such up-regulation of NF-kappaB activity is observed in the tumor cells as well as in the surrounding lymphocytes.

Upregulation of heme oxygenase-1 and p21 confers resistance to apoptosis in human gastric cancer cells

Both heme oxygenase-1 (HO-1) and p21(WAF1/Cip1) (p21) are involved in the pathogenesis of human cancer and their functions are closely associated with apoptosis. However, how these two molecules regulate apoptosis in human gastric cancer is unknown. In this study, we studied how HO-1 and p21 were regulated in two gastric cancer cell lines, MKN-45 with wild p53 and MKN-28 with mutant p53. The cells were treated with hemin and cadmium to induce HO-1. The result showed that HO-1 protein was significantly induced by hemin and cadmium in both cells tested. Following the HO-1 expression, p21 level was also markedly induced. The cells with increased HO-1 and p21 showed obviously resistantance to apoptotic stimuli. The levels of HO-1 and p21 induced were significantly inhibited by p38 mitogen-activated protein kinase (p38 MAPK) inhibitor (SB203580) and extracellular-regulated kinase (ERK) inhibitor (PD098059). Parallel to decreased HO-1 and p21 expression, the kinase inhibitors also significantly attenuated the resistance of the cells to apoptosis. The elevated HO-1 and p21 was further found to be associated with increase activity of the nuclear NF-kappaB and the inhibition of NF-kappaB led to the block of their induction. The elevated HO-1 and p21 were also demonstrated to be related to increased cellular inhibitor of caspase inbitory protein-2 (c-IAP2) and decreased caspapse-3 activity. It was noted that the above changes observed were not different between MKN-45 and MKN-28 cells, suggesting the functions of HO-1 and p21 were irrespective of the status of p53. In conclusion, we demonstrate that the resistance to apoptosis in gastric cancer cells with elevated HO-1 and p21 is independent of p53 status in a p38 MAPK- and ERK-mediated pathway with elevated c-IAP2 and decreased caspase-3 activity and that this pathway is sensitive to the inhibition of NF-kappaB.

A nonradioactive method for detecting DNA-binding activity of nuclear transcription factors

To determine the feasibility of a nonradioactive electrophoresis mobility shift assay for detecting nuclear transcription factor, double-stranded oligonucleotides encoding the consensus target sequence of NF-kappa B were labelled with DIG by terminal transferase. After nuclear protein stimulated with phorbol 12-myristate 13-acetate (PMA) or PMA and pyrrolidine dithiocarbamate (PDTC) electrophoresed on 8% nondenaturing poliacrylamide gel together with oligeonucleotide probe, they were electro-blotted nylon membrane positively charged. Anti-DIG-AP antibody catalyzed chemiluminescent substrate CSPD to image on X-film. The results showed that nuclear proteins binded specifically to the NF-kappa B consensus sequence in the EMSA by chemiluminescent technique method and the activity of NF-kappa B in PMA group was more than that in PMA + PDTC group. It is suggested that detection of NF-kappa B by EMSA with chemiluminescent technique is feasible and simple, which can be performed in ordinary laboratories.

Murine pancreatic tumor cell line TD2 bears the characteristic pattern of genetic changes with two independently amplified gene loci

TGFalpha/p53(+/-) transgenic mice represent a genetically engineered mouse model for pancreatic adenocarcinoma. The tumors develop a characteristic pattern of secondary genetic changes. From one of these tumors, the permanent cell line TD2 was established. Here, we describe in detail the genetic changes by molecular-cytogenetic techniques. The original tumor-specific CGH profile has been retained unchanged. The most characteristic aberration pattern bears chromosome 11. Egfr, localized on proximal chromosome 11, is amplified two to three times and leads to an easily identifiable, stable marker chromosome with a large amplification unit, which is present in each metaphase. The wild-type p53 gene on distal chromosome 11 is lost. The p16Ink4a locus on chromosome 4 is hypermethylated. For c-Myc a 15-fold amplification, present in a 1.65 Mb amplification unit, is detected on chromosome 15. Transition between presence in the form of several double minutes, DMs, or a single homogeneously staining region, HSR, was observed for c-Myc. Molecular-cytogenetic analysis of both amplification units show that Egfr amplification and c-Myc amplification represent two alternative modes by which genes get amplified in tumor cells. The expression level of the respective genes was proven by Northern blot analysis. The cell line TD2 represents a valuable in vitro model for pancreatic adenocarcinoma.

Stable expression of the avian retroviral oncoprotein v-Rel in avian, mouse, and dog cell lines

Overexpression of the retroviral oncoprotein v-Rel can rapidly transform and immortalize a variety of avian cells in culture. However, mammalian models for v-Rel-mediated oncogenesis have been compromised by the fact that high-level expression of v-Rel has been reported to be toxic in many mammalian cell types, including mouse 3T3 cells, Rat-1 cells, and mouse bone marrow cells. In this article, we demonstrate that 3T3 cells can support expression of v-Rel for at least 24 days when infected with a mouse stem cell virus (MSCV) retroviral vector containing v-rel. In retrovirus-infected 3T3 cells, v-Rel is located in the nucleus and can bind to DNA, but does not transform the cells. On the other hand, 3T3 and Rat-2 cells do not express v-Rel after stable transfection with a pcDNA-based v-Rel expression vector. We also show that infection of the IL3-dependent mouse B cell line BaF3 with the MSCV-v-rel vector results in expression of v-Rel, but does not convert these cells to growth factor independence. In contrast to 3T3 cells, the dog osteosarcoma D17 cell line can support a high level of v-Rel expression, after either transfection or infection with a retroviral vector. That is, v-Rel can be stably expressed as a nuclear, DNA-binding protein in D17 cells to approximately the same level as in chicken embryo fibroblasts. These results suggest that the restriction to v-Rel expression in rodent fibroblasts is generally absent in D17 cells and that the type of v-rel expression vector determines whether 3T3 cells can support stable expression of v-Rel. The findings reported here are an essential first step in the development of mammalian systems to study Rel-mediated oncogenesis.

NF-kappaB/Rel transcriptional pathway: implications in pancreatic cancer

Despite considerable efforts in understanding the cellular mechanisms contributing to pancreatic cancer, the prognosis of this malignant disease is still extremely poor. Although pancreatic cancer is the fifth common cause of cancer death in Western countries, current options in treatment enable a 5-yr survival rate for all stages of less than 5%. In the face fo the fatal outcome, new approaches to the therapy have been established. Based on its role in malignant transformation, apoptosis, and cell proliferation, the transcription factor NF-kappaB/Rel has gained the attention of many laboratories. This review provides basic information for the understanding of the biology of NF-kappaB and aims at presenting experimental data illustrating the involvement of NF-kappaB/Rel in pancreatic cancer.

The role of Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 regulator of transcription activation (RTA) in control of gene expression

The mechanisms that control the replication state, latency versus lytic, of human herpesviruses have been under intense investigations. Here we summarize some of the recent findings that help define such mechanisms for Kaposi's sarcoma-associated herpesvirus/human herpesvirus type 8 (KSHV/HHV-8). For HHV-8, the viral regulator of transcription activation (RTA) is a key mediator of the switch from latency to lytic gene expression in infected cells. RTA is necessary and sufficient to drive HHV-8 lytic replication and the production of viral progeny. The RTA is an immediate-early gene product, it is the initial activator of expression of a multitude of viral and cellular genes that have been implicated in the replication of HHV-8 and pathogenesis of KS. Interactions of RTA with a number of viral promoters, and with a number of transcription factors or transcriptional co-activators are highlighted. Modulation of transactivation, through alternate RTA-protein, or RTA-promoter interactions, is hypothesized to participate in the selective tissue tropism and differential pathogenesis observed in KS.

Mutations within a conserved protein kinase A recognition sequence confer temperature-sensitive and partially defective activities onto mouse c-Rel

We have created two mutants of mouse transcription factor c-Rel (c-G29E and c-R266H) that are analogous to mutants previously shown to have temperature-sensitive (ts) functions for the homologous Drosophila protein Dorsal and the retroviral oncoprotein v-Rel. In vitro, c-R266H shows both a ts and a concentration-dependent ability to bind DNA, suggesting that the lesion affects the ability of c-Rel to form homodimers. In contrast, the ability of mouse c-G29E to bind DNA in vitro is not ts. c-Rel mutant c-R266H also shows a ts ability to activate transcription from a kappaB-site reporter plasmid, whereas c-G29E activates transcription well above control levels at both 33 and 39 degrees C. Insertion of two amino acids (Pro-Trp) between amino acids 266 and 267 in mouse c-Rel (mutant c-SPW) also creates a c-Rel protein with distinct properties: mutant c-SPW is partially defective in that it cannot form DNA-binding homodimers but can form DNA-binding heterodimers with p50. Interestingly, the mutations in c-Rel that affect homodimer formation (c-R266H and c-SPW) fall within a consensus protein kinase A recognition sequence but are not predicted to lie in the dimer interface. Conditional and partially defective mutants such as those described herein may be useful for identifying physiological responses and genes regulated by specific Rel/NF-kappaB family members.

NF-kappaB is required for apoptosis prevention during herpes simplex virus type 1 infection

Wild-type herpes simplex virus type 1 (HSV-1) infection triggers apoptosis in human cells. The subsequent synthesis of infected cell proteins between 3 and 6 h postinfection (hpi) acts to block this process from killing the cells. The factors produced during this window also prevent cell death induced by environmental staurosporine or sorbitol (M. Aubert, J. O'Toole, and J. A. Blaho, J. Virol. 73:10359-10370, 1999). We now report that (i) during the prevention window, HSV-1(F) also inhibited apoptosis induced by tumor necrosis factor alpha (TNF-alpha) plus cycloheximide (CHX) treatment. While deciphering the mechanism of this inhibition, we observed that (ii) the transcription factor NF-kappaB translocated from the cytoplasm into the nuclei of infected cells, and (iii) this migration initiated at 3 hpi. (iv) The complete inhibition of protein synthesis at 3 hpi by the addition of CHX precluded NF-kappaB translocation, while CHX additions at 6 hpi or later did not elicit this effect. This result confirms that infected cell protein synthesis is required for the nuclear import of NF-kappaB. (v) The detection of NF-kappaB in nuclei correlated with the ability of HSV-1(F), HSV-1(KOS1.1), or HSV-1(R7032), a replication-competent recombinant virus containing a deletion in the gene encoding the gE glycoprotein, to prevent apoptosis. (vi) NF-kappaB did not bind its kappaB DNA recognition site and remained cytoplasmic in cells actively undergoing apoptosis following infection with HSV-1(vBSdelta27), a virus with the key regulatory protein ICP27 deleted. (vii) Prestimulation of NF-kappaB by the addition of a phorbol ester prevented HSV-1(vBSdelta27)-induced apoptosis. (viii) Retention of NF-kappaB in the cytoplasm by the addition of a pharmacological antagonist of its release from IkappaBalpha led to an increase in death factor processing during HSV-1(F) infection. (ix) A novel HEp-2 clonal cell line, termed IkappaBalphaDN, was generated which expresses a dominant-negative form of IkappaBalpha. Treatment of IkappaBalphaDN cells with TNF-alpha in the absence of CHX resulted in apoptotic death due to the inability of NF-kappaB to become activated in these cells. Finally, (x) infection of IkappaBalphaDN cells with HSV-1(F) or HSV-1(KOS1.1) resulted in apoptosis, demonstrating that (xi) the nuclear translocation of NF-kappaB between 3 and 6 hpi (the prevention window) is necessary to prevent apoptosis in wild-type HSV-1-infected human HEp-2 cells.

X-ray crystal structure of an IkappaBbeta x NF-kappaB p65 homodimer complex

We report the crystal structure of a murine IkappaBbeta x NF-kappaB p65 homodimer complex. Crystallographic models were determined for two triclinic crystalline systems and refined against data at 2.5 and 2.1 A. The overall complex structure is similar to that of the IkappaBalpha.NF-kappaB p50/p65 heterodimer complex. One NF-kappaB p65 subunit nuclear localization signal clearly contacts IkappaBbeta, whereas a homologous segment from the second subunit of the homodimer is mostly solvent-exposed. The unique 47-amino acid insertion between ankyrin repeats three and four of IkappaBbeta is mostly disordered in the structure. Primary sequence analysis and differences in the mode of binding at the IkappaBbeta sixth ankyrin repeat and NF-kappaB p65 homodimer suggest a model for nuclear IkappaBbeta.NF-kappaB.DNA ternary complex formation. These unique structural features of IkappaBbeta may contribute to its ability to mediate persistent NF-kappaB activation.

KappaB-Ras binds to the unique insert within the ankyrin repeat domain of IkappaBbeta and regulates cytoplasmic retention of IkappaBbeta x NF-kappaB complexes

The IkappaBalpha and IkappaBbeta proteins inhibit the transcriptional potential of active NF-kappaB dimers through stable complex formation. It has been shown that inactive IkappaBalpha x NF-kappaB complexes shuttle in and out of the nucleus, whereas IkappaBbeta x NF-kappaB complexes are retained exclusively in the cytoplasm of resting cells. The biochemical mechanism underlying this functional difference and its consequences are unknown. Although the two IkappaB proteins are significantly homologous, IkappaBbeta contains a unique 47-amino acid insertion of unknown function within its ankyrin repeat domain. In this study, we assess the role of the IkappaBbeta insert in regulating cytoplasmic retention of IkappaBbeta.NF-kappaB complexes. Deletion of the IkappaBbeta insert renders IkappaBbeta x NF-kappaB complexes capable of shuttling between the nucleus and cytoplasm, similar to IkappaBalpha x NF-kappaB complexes. A small Ras-like G-protein, kappaB-Ras, participates with the IkappaBbeta insert to effectively mask the NF-kappaB nuclear localization potential. Similarly, a complex between NF-kappaB and a mutant IkappaBbeta protein containing four serine to alanine mutations within its C-terminal proline, glutamic acid, serine, and threonine-rich sequence exhibits nucleocytoplasmic shuttling. This suggests a phosphorylation state-dependent role for the C-terminal proline, glutamic acid, serine, and threonine-rich sequence of IkappaBbeta in proper localization of IkappaBbeta x NF-kappaB complexes. These results are consistent with structural studies, which predicted that binary IkappaBbeta x NF-kappaB complexes should be capable of nuclear translocation, and with previous observations that hypophosphorylated IkappaBbeta.NF-kappaB complexes can reside in the nucleus.

Solution study of the NF-kappaB p50-DNA complex by UV laser protein-DNA cross-linking

In this study, we describe a new approach for studying protein-DNA interactions in solution. The approach is based on mapping the UV laser-induced protein-DNA cross-links between the amino acids of the protein and the DNA bases that are in direct contact. The approach was applied for studying the solution structure of the human necrosis factor (NF)-kappaB p50 homodimer bound to a 37 base pair DNA. Several points of contact identical to those observed in the NF-kappaB-DNA crystal structure were found between the two biomolecules. Evidence is provided for the occurrence of two new contact points, one for each DNA strand. These new points of contact are located symmetrically a base apart from the extremity of the binding sequence.

Identification of Ets-1 as an important transcriptional activator of CTP:phosphocholine cytidylyltransferase alpha in COS-7 cells and co-activation with transcriptional enhancer factor-4

Phosphatidylcholine biosynthesis via the CDP-choline pathway is primarily regulated by CTP:phosphocholine cytidylyltransferase (CT). Transcriptional enhancer factor-4 (TEF-4) enhances the transcription of CTalpha in COS-7 cells by interactions with the basal transcription machinery (Sugimoto, H., Bakovic, M., Yamashita, S., and Vance, D.E. (2001) J. Biol. Chem. 276,12338-12344). To identify the most important transcription factor involved in basal CTalpha transcription, we made CTalpha promoter-deletion and -mutated constructs linked to a luciferase reporter and transfected them into COS-7 cells. The results indicate that an important site regulating basal CTalpha transcription is -53/-47 (GACTTCC), which is a putative consensus-binding site of Ets transcription factors (GGAA) in the opposite orientation. Gel shift analyses indicated the existence of a binding protein for -53/-47 (GACTTCC) in nuclear extracts of COS-7 cells. When anti-Ets-1 antibody was incubated with the probe in gel shift analyses, the intensity of the binding protein was decreased. The binding of endogenous Ets-1 to the promoter probe was increased when TEF-4 was expressed; however, the amount of Ets-1 detected by immunoblotting was unchanged. When cells were transfected with Ets-1 cDNA, the luciferase activity of CTalpha promoter constructs was greatly enhanced. Co-transfection experiments with Ets-1 and TEF-4 showed enhanced expression of reporter constructs as well as CTalpha mRNA. These results suggest that Ets-1 is an important transcriptional activator of the CTalpha gene and that Ets-1 activity is enhanced by TEF-4.

Induction of heme oxygenase-1 expression in murine macrophages is essential for the anti-inflammatory effect of low dose 15-deoxy-Delta 12,14-prostaglandin J2

15-Deoxy-Delta 12,14-prostaglandin J2 (15d-PGJ2), a cyclopentenone prostaglandin, displays a potent anti-inflammatory effect at micromolar concentrations (>2 microM) through direct inhibition of nuclear factor (NF)-kappa B activation. Here we show that at submicromolar concentrations (0.1-0.5 microM) 15d-PGJ2 retains the ability to suppress the production of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) in lipopolysaccharide (LPS)-activated murine J774 macrophages under the conditions of a prolonged incubation (>12 h). Western blot analysis revealed that the expression of the cytoprotective enzyme, heme oxygenase-1 (HO-1), was induced and coincident with the anti-inflammatory action of 15d-PGJ2. Inhibition of HO-1 activity or scavenging carbon monoxide (CO), a byproduct derived from heme degradation, significantly attenuated the suppressive activity of 15d-PGJ2. Furthermore, LPS-induced NF-kappa B activation assessed by the inhibitory protein of NF-kappa B(I kappa B) degradation and p50 nuclear translocation was diminished in cells subjected to prolonged treatment with the low concentration of 15d-PGJ2. Treatment of cells with the protein synthesis inhibitor, cycloheximide, or the specific p38 MAP kinase inhibitor, SB203580, blocked the induction of HO-1 and suppression of LPS-induced I kappa B degradation mediated by 15d-PGJ2. Likewise, HO inhibitor and CO scavenger were effective in abolishing the inhibitory effects of 15d-PGJ2 on NF-kappa B activation induced by LPS. The functional role of CO was further demonstrated by the use of a CO releasing molecule, tricarbonyldichlororuthenium(II) dimer, which significantly suppressed LPS-induced nuclear translocation of p50 as assessed by confocal immunofluorescence. Collectively, these data suggest that even at submicromolar concentrations 15d-PGJ2 can exert an anti-inflammatory effect in macrophages through a mechanism that involves the action of HO/CO.

Gains of 2p involving the REL locus correlate with nuclear c-Rel protein accumulation in neoplastic cells of classical Hodgkin lymphoma

Structural aberrations of the short arm of chromosome 2, mostly resulting in gains of 2p13 approximately 16, have recently been described as being highly recurrent in Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL). As these gains consistently lead to increased copy numbers of the REL oncogene locus, we investigated the expression of the c-Rel protein in a series of 30 cHL cases with known genomic REL status as determined by comparative genomic hybridization and interphase cytogenetics. Expression of the c-Rel protein was investigated in 26 biopsies by immunohistochemistry. Distinct patterns were observed in HRS cells with no staining, cytoplasmic, and/or nuclear staining for c-Rel. All 13 samples with additional copies of the REL locus displayed nuclear staining for c-Rel, while 13 cHL samples lacking chromosome 2 (2p) gains displayed a significantly lower proportion or complete absence of HRS cells with nuclear c-Rel expression. Detailed analysis using combined immunophenotyping and interphase cytogenetics of individual HRS cells demonstrated that REL gains correlated with the presence of nuclear c-Rel staining. Additionally, in 2 cHL samples with translocation breakpoints in 2p13 approximately 16, nuclear staining of c-Rel was observed; in one of them the staining pattern was indicative of a truncated c-Rel protein. The correlation between structural aberrations involving the REL locus and nuclear c-Rel accumulation in HRS cells qualifies REL as a target gene of the frequent gains in 2p in cHL. The data suggest that REL aberrations are a genetic mechanism contributing to constitutive nuclear factor (NF)-kappa B/Rel activation in cHL.

NF-kappa B nuclear localization and its prognostic significance in prostate cancer

OBJECTIVE

To detect the subcellular localization of NF-kappa B (p65) in human prostate cancer tissues of different histological grades, and to test whether NF-kappa B localization alone, or combined with the histological grade, can be used to predict patient outcome.

PATIENTS AND METHODS

Prostate cancer tissues were obtained from radical prostatectomy specimens; the histological grade was determined using the Gleason grading system. Clinical outcomes were defined as good (5-year disease-free survival with undetectable levels of prostate specific antigen) or poor (progression to bone metastases). The subcellular localization of NF-kappa B was visualized by immunohistochemistry using an anti-p65 antibody.

RESULTS

The NF-kappa B subcellular localization was initially assessed in 45 specimens; in these samples a nuclear localization of NF-kappa B was specific to cancer tissues, but did not correlate with the Gleason score (P = 0.089). NF-kappa B was then assessed as a prognostic marker to complement Gleason score in predicting cancer progression. Tumour tissues from 30 men with a known clinical outcome were included; 10 of 17 patients who had a poor outcome were positive for NF-kappa B nuclear staining, whereas only two of 13 with a good outcome were positive (P = 0.026). When NF-kappa B subcellular localization and Gleason score were combined, two risk categories of progression were defined. Eleven of 13 specimens from those with a good outcome were in the low-risk category (Gleason 2-4 or Gleason 5-7 with negative nuclear NF-kappa B) and 12 of 17 in the poor outcome group were in the high-risk category (Gleason 8-10 or Gleason 5-7 with positive nuclear NF-kappa B; P = 0.004).

CONCLUSION

NF-kappa B is detectable in the nucleus in prostate cancer tissues and positivity can be used to help predict patient outcome. Multivariate analyses using other clinical and molecular variables are underway, and will validate the usefulness of NF-kappa B as a prognostic factor.

Dexamethasone prevents interleukin-1beta-induced nuclear factor-kappaB activation by upregulating IkappaB-alpha synthesis, in lymphoblastic cells

AIMS

Glucocorticoids (GCs) exert some of their anti-inflammatory actions by preventing the activation of the transcription factor nuclear factor (NF)-kappaB. The GC-dependent inhibition of NF-kappaB may occur at different levels, but the mechanisms involved are still incompletely understood. In this work, we investigated whether the synthetic GC, dexamethasone (Dex), modulates the activity of NF-kappaB in the lymphoblastic CCRF-CEM cell line. We also evaluated the ability of Dex to prevent the activation of NF-kappaB in response to the potent proinflammatory cytokine, interleukin (IL)-1beta.

RESULTS

Exposure of the cells to Dex (1 microM) induced the rapid degradation of IkappaB-alpha, leading to the transient translocation of the NF-kappaB family members p65 and p50 from the cytoplasm to the nucleus, as evaluated by western blot. Electrophoretic mobility shift assays revealed that, in the nucleus, these NF-kappaB proteins formed protein-DNA complexes, indicating a transient activation of NF-kappaB. Additionally, Dex also induced de novo synthesis of IkappaB-alpha, following its degradation. Finally, when the cells were exposed to Dex (1 microM) prior to stimulation with IL-1beta (20 ng/ml), Dex was efficient in preventing IL-1beta-induced NF-kappaB activation. The GC antagonist, RU 486 (10 microM), did not prevent any of the effects of Dex reported here.

CONCLUSION

Our results indicate that, in CCRF-CEM cells, Dex prevents NF-kappaB activation, induced by IL-1beta, by a mechanism that involves the upregulation of IkappaB-alpha synthesis, and that depends on the early and transient activation of NF-kappaB.

Novel agents for the prevention of breast cancer: targeting transcription factors and signal transduction pathways

Transformation of breast cells occurs through loss or mutation of tumor suppressor genes, or activation or amplification of oncogenes, leading to deregulation of signal transduction pathways, abnormal amplification of growth signals, and aberrant expression of genes that ultimately transform the cells into invasive cancer. The goal of cancer preventive therapy, or "chemoprevention," is to eliminate premalignant cells or to block the progression of normal cells into cancer. Multiple alterations in signal pathways and transcription factors are observed in mammary gland tumorigenesis. In particular, estrogen receptor (ER) deregulation plays a critical role in breast cancer development and progress, and targeting ER with selective ER modulators (SERMs) has achieved significant reduction of breast cancer incidence in women at high risk for breast cancer. However, not all breast cancer is prevented by SERMs, because 30-40% of the tumors are ER-negative. Other receptors for retinoids, vitamin D analogs and peroxisome proliferator-activiator, along with transcription factors such as AP-1, NF-kappaB, and STATs (signal transducers and activators of transcription) affect breast tumorigenesis. This is also true for the signal transduction pathways, for example cyclooxygenase 2 (Cox-2), HER2/neu, mitogen-activated protein kinase (MAPK), and PI3K/Akt. Therefore, proteins in pathways that are altered during the process of mammary tumorigenesis may be promising targets of future chemopreventive drugs. Many newly-developed synthetic or natural compounds/agents are now under testing in preclinical studies and clinical trials. Receptor selective retinoids, receptor tyrosine kinase inhibitors (TKIs), SERMs, Cox-2 inhibitors, and others are some of the promising novel agents for the prevention of breast cancer. The chemopreventive activity of these agents and other novel signal transduction inhibitors are discussed in this chapter.

A Paradigm for Gene Regulation: Inflammation, NF-κB and PPAR

The onset of inflammatory gene expression is driven by the transcription factor NF-kappaB, whose transcriptional activity is regulated at multiple levels. First, NF-kappaB activity is regulated by cytoplasmic degradation of the IkappaB inhibitor and nuclear translocation. Second, the nuclear p65 transactivation potential can be further influenced by posttranslational modifications, such as phosphorylation and/or acetylation. The p65 phosphorylation is a process highly regulated by both cell- and stimulus-dependent activating kinases. Ser276 phosphorylation seems to be highly important considering its crucial role in the interaction with and the engagement of the cofactor CBP/p300. We have identified MSK1 as an acting kinase in the TNF-signalling pathway, where it is responsible for p65 phosphorylation at Ser276, as well as for H3 phosphorylation of Ser10 in IL-6 promoter-associated chromatin (Fig. 1) (Saccani et al., 2002; Vermeulen et al., 2002, 2003). To our knowledge, this was the first report that identifies one particular kinase involved in transcription factor phosphorylation and histone modification at the level of a single promoter in order to establish gene activation. The question of which element takes the initial step to recruit and to assemble the activated transcription complex still remains unanswered (Vanden Berghe et al., 2002). PPAR alpha negatively interferes with inflammatory gene expression by up-regulation of the cytoplasmic inhibitor molecule IkappaB alpha, thus establishing an autoregulatory loop (Fig. 1). This induction takes place in the absence of a PPRE, but requires the presence of NF-kappaB and Sp1 elements in the IkappaB alpha promoter sequence as well as DRIP250 cofactors. The detailed mechanism how PPAR can activate genes in a non-DNA-binding way needs further investigation; moreover, it is at present not clear whether this upregulation, unlike the inhibitory effect of glucocorticoids, is a cell type- or a PPAR-specific phenomenon.

The human B-cell lymphoma cell line RC-K8 has multiple genetic alterations that dysregulate the Rel/NF-kappaB signal transduction pathway

The human large B-cell lymphoma cell line RC-K8 has a rearranged REL locus that directs the production of a chimeric protein, termed REL-NRG (Non-Rel Gene). In this study, we show that RC-K8 cells have constitutively nuclear heterodimeric and homodimeric DNA-binding complexes that consist of p50, REL, and REL-NRG. In vitro, IkappaBalpha can block the DNA-binding activity of wild-type REL homodimers but not REL-NRG homodimers. In vivo, REL-NRG cannot activate transcription of a kappaB site reporter plasmid, suggesting that it is a transcription repressing or blocking REL protein. By Western blotting, no IkappaBalpha protein can be detected in extracts of RC-K8 cells. The absence of IkappaBalpha protein in RC-K8 cells appears to be due to mutations that cause premature termination of translation in three of the four copies of the IKBA gene in RC-K8 cells. Re-expression of wild-type IkappaBalpha or a super-repressor form of IkappaBalpha in RC-K8 cells is cytotoxic; in contrast, expression of a dominant-negative form of IkappaB kinase does not affect the growth of RC-K8 cells. By cDNA microarray analysis, a number of previously identified Rel/NF-kappaB target genes are overexpressed in RC-K8 cells, consistent with there being transcriptionally active REL complexes. Taken together, our results suggest that the growth of RC-K8 cells is dependent on the activity of nuclear wild-type REL dimers, while the contribution of REL-NRG to the transformed state of RC-K8 cells is less clear. Nevertheless, the RC-K8 cell line is the first tumor cell line identified with mutations in genes encoding multiple proteins in the Rel/NF-kappaB signal transduction pathway.

Solvent exposed non-contacting amino acids play a critical role in NF-kappaB/IkappaBalpha complex formation

IkappaBalpha inhibits transcription factor NF-kappaB activity by specific binding to NF-kappaB heterodimers composed of p65 and p50 subunits. It binds with slightly lower affinity to p65 homodimers and with significantly lower affinity to homodimers of p50. We have employed a structure-based mutagenesis approach coupled with protein-protein interaction assays to determine the source of this dimer selectivity exhibited by IkappaBalpha. Mutation of amino acid residues in IkappaBalpha that contact NF-kappaB only marginally affects complex binding affinity, indicating a lack of hot spots in NF-kappaB/IkappaBalpha complex formation. Conversion of the weak binding NF-kappaB p50 homodimer into a high affinity binding partner of IkappaBalpha requires transfer of both the NLS polypeptide and amino acid residues Asn202 and Ser203 from the NF-kappaB p65 subunit. Involvement of Asn202 and Ser203 in complex formation is surprising as these amino acid residues occupy solvent exposed positions at a distance of 20A from IkappaBalpha in the crystal structures. However, the same amino acid residue positions have been genetically isolated as determinants of binding specificity in a homologous system in Drosophila. X-ray crystallographic and solvent accessibility experiments suggest that these solvent-exposed amino acid residues contribute to NF-kappaB/IkappaBalpha complex formation by modulating the NF-kappaB p65 subunit NLS polypeptide.

A short domain within Bcl-3 is responsible for its lymphocyte survival activity

The NFkappaB factor Bcl-3 influences the survival of T cells when they are activated to take part in immune responses. Because treatment of mice with adjuvant results in the increased expression of Bcl-3 in T cells, where it has survival-promoting effects, Bcl-3 may be an important, limiting factor that is supplied to T cells only when they are contributing to an appropriate immune response to infection, and not when spuriously activated by self-antigens. Although Bcl-3 is a member of the NFkappaB/Rel/IkappaB family of transcription factors, the means by which it promotes T cell survival is not obvious because Bcl-3 is unique in having an ankyrin repeat domain, like inhibitory IkappaB proteins, while also possessing domains capable of transcriptional activation, like Rel proteins. In order to understand the basis for the survival activity of Bcl-3, deletion mutants were engineered and tested in a retroviral gene transfer sytem. We report that most of Bcl-3 can be deleted without diminishing its ability to prolong the survival of activated T and B cells, and find that its lymphocyte survival domain maps to the vicinity of its first and second ankryin repeats. This information sets the stage for experiments in which a focused search can be made for mediators of Bcl-3 survival effects.

Differential regulation of the inhibitor of apoptosis ch-IAP1 by v-rel and the proto-oncogene c-rel

The v-rel oncogene encoded by reticuloendotheliosis virus is the acutely transforming member of the Rel/NF-kappaB family of transcription factors. v-Rel is a truncated and mutated form of c-Rel and transforms cells by inducing the aberrant expression of genes regulated by Rel/NF-kappaB proteins. The expression of ch-IAP1, a member of the inhibitor-of-apoptosis family, is highly elevated in cells expressing v-Rel and contributes to the immortalization of cells transformed by this oncoprotein. In this study we demonstrate that the elevated expression of ch-IAP1 in v-Rel-expressing cells is due to an increased rate of transcription. The ch-IAP1 promoter was isolated, and four Rel/NF-kappaB binding sites were identified upstream of the transcription start site. Two kappaB sites proximal to the transcription start site were required for v-Rel to activate the ch-IAP1 promoter. While c-Rel also utilized these sites, a third more-distal kappaB site was required for its full activation of the ch-IAP1 promoter. Differences in the transactivation domains of v-Rel and c-Rel are responsible for their different abilities to utilize these sites and account for their differential activation of the ch-IAP1 promoter. Although c-Rel was a more potent activator of the ch-IAP1 promoter than v-Rel in transient reporter assays, cells stably overexpressing c-Rel failed to maintain high levels of ch-IAP1 expression. The reduction of ch-IAP1 expression in these cells correlated with the efficient regulation of c-Rel by IkappaBalpha. The ability of v-Rel to escape IkappaBalpha regulation allows for the gradual and sustained elevation of ch-IAP1 expression directly contributing to the transforming properties of v-Rel.

Stronger correlation of bcl-3 than bcl-2, bcl-xL, costimulation, or antioxidants with adjuvant-induced T cell survival

A set of signals separate from those needed for T cell activation and clonal expansion acts to sustain a T cell response once it has begun. Immunologic adjuvants can initiate these signals in a process we designate adjuvant-induced survival (AIS). Here, the natural adjuvant LPS was used in a super-antigen model of AIS to understand which factors are needed to sustain T cell survival after activation. Flow cytometric stains for antiapoptotic Bcl-2 and Bcl-xL showed that neither factor was well correlated with AIS, although both were increased transiently upon T cell activation. T cells protected via AIS showed no increased ability to resist death caused by reactive oxygen species, and cellular division was not accelerated as might be expected if AIS were to operate through co-stimulatory pathways. Finally, microarray analyses were performed that showed increased expression of Bcl-3, an NFkappaB/IkappaB factor, was correlated with AIS. It is proposed that T cell survival during productive immune responses occurs by successive activities of Bcl-2, Bcl-xL and Bcl-3, with Bcl-3 requiring innate immune responses to adjuvants for its expression.

NFkappaB and caspase-3 activity in apoptotic hepatocytes of galactosamine-sensitized mice treated with TNFalpha

Tumor necrosis factor-alpha (TNFalpha) induces apoptosis in hepatocytes only under transcriptional arrest induced by galactosamine (GalN). In this study we demonstrated the shuttle of the transcription factor NFkappaB (nuclear factor-kappa B) in the liver tissue of mice within 30 min-4.5 hr hours after GalN/TNFalpha treatment. NFkappaB translocation from cytoplasm to the nucleus is initiated by its separation from the inhibitory IkappaB proteins which include IkappaBalpha, IkappaBbeta, and IkappaB. Thirty minutes after GalN/TNFalpha administration, NFkappaBp65 in hepatocellular nuclei becomes increasingly detectable and reaches its highest level after 2.5 hr. Then export back into cytoplasm begins but, surprisingly, approximately 30% of NFkappaB remains in the nuclear fraction and appears as an immunoprecipitate in the nuclei of apoptotic hepatocytes. Non-apoptotic hepatocytes do not show any reaction product in the nuclei 4.5 hr after treatment. Correspondingly, the amount of dissociated IkappaBbeta decreases in the cytoplasm up to 2.5 hr and increases again afterwards, although it does not reach the level of the control samples. No evidence of IkappaBbeta in the nuclei was found either immunocytochemically or biochemically. Caspase-3 activity, which is responsible for apoptosis, increases significantly after 3.5 hr. At that time, apoptotic hepatocytes can occasionally be observed and, 4.5 hr after GalN/TNFalpha treatment, constitute approximately 30% of the hepatocytes.

A small molecule inhibitor of redox-regulated NF-kappa B and activator protein-1 transcription blocks allergic airway inflammation in a mouse asthma model

An oxidant/antioxidant imbalance is seen in the lungs of patients with asthma. This oxidative stress in asthmatic airways may lead to activation of redox-sensitive transcription factors, NF-kappaB and AP-1. We examined the effect of the small molecule inhibitor of redox-regulated NF-kappaB and AP-1 transcription, MOL 294 on airway inflammation and airway hyperreactivity (AHR) in a mouse model of asthma. MOL 294 is a potent nonpeptide inhibitor of NF-kappaB and AP-1 based upon a beta-strand template that binds to and inhibits the cellular redox protein thioredoxin. BALB/c mice after i.p. OVA sensitization (day 0) were challenged with intranasal OVA on days 14, 25, 26, and 27. MOL 294, administered intranasal on days 25-27, blocked the airway inflammatory response to OVA assessed 24 h after the last OVA challenge on day 28. MOL 294 reduced eosinophil, IL-13, and eotaxin levels in bronchoalveolar lavage fluid and airway tissue eosinophilia and mucus hypersecretion. MOL 294 also decreased AHR in vivo to methacholine. These results support redox-regulated transcription as a therapeutic target in asthma and demonstrate that selective inhibitors can reduce allergic airway inflammation and AHR.

Constitutive nuclear factor-kappa B activity is required for central neuron survival

The function of nuclear factor (NF)-kappaB within the developing and mature CNS is controversial. We have generated transgenic mice to reveal NF-kappaB transcriptional activity in vivo. As expected, constitutive NF-kappaB activity was observed within immune organs, and tumor necrosis factor-inducible NF-kappaB activity was present in mesenchymal cells. Intriguingly, NF-kappaB activity was also prominent in the CNS throughout development, especially within neocortex, olfactory bulbs, amygdala, and hippocampus. NF-kappaB in the CNS was restricted to neurons and blocked by overexpression of dominant-negative NF-kappaB-inducible kinase or the IkappaBalphaM super repressor. Blocking endogenous neuronal NF-kappaB activity in cortical neurons using recombinant adenovirus induced neuronal death, whereas induction of NF-kappaB activity increased levels of anti-apoptotic proteins and was strongly neuroprotective. Together, these data demonstrate a physiological role for NF-kappaB in maintaining survival of central neurons.

Thalidomide in the management of multiple myeloma

The discovery that multiple myeloma is associated with new vessel formation and is correlated with survival and proliferation led initially to the use of thalidomide for patients with relapsed or refractory disease. The outcome with conventional chemotherapy in this setting has historically been very poor. New insights into the biology of the disease suggests that thalidomide may work via a number of other mechanisms and the advent of the thalidomide analogues with their differential effects on survival and proliferation pathways has opened up a new era in the understanding and treatment of the disease. The encouraging results from phase I/II trials of these agents has meant that for the first time in 50 years there is the opportunity to improve outcome. Further work is in progress to define how best to use these drugs and their role in treatment at different stages of the disease.

Complement factor B gene regulation: synergistic effects of TNF-alpha and IFN-gamma in macrophages

Complement factor B (Bf) plays an important role in activating the alternative complement pathway. The inflammatory cytokines, in particular TNF-alpha and IFN-gamma, are critical in the regulation of Bf gene expression in macrophages. In this study, we investigated the mechanisms of Bf gene regulation by TNF-alpha and IFN-gamma in murine macrophages. Northern analysis revealed that Bf mRNA expression was synergistically up-regulated by TNF-alpha and IFN-gamma in MH-S cells. Truncations of the 5' Bf promoter identified a region between -556 and -282 bp that mediated TNF-alpha responsiveness as well as the synergistic effect of TNF-alpha and IFN-gamma on Bf expression. Site-directed mutagenesis of a NF-kappaB-binding element in this region (-433 to -423 bp) abrogated TNF-alpha responsiveness and decreased the synergistic effect of TNF-alpha and IFN-gamma on Bf expression. EMSAs revealed nuclear protein binding to this NF-kappaB cis-binding element on TNF-alpha stimulation. Supershift analysis revealed that both p50 and p65 proteins contribute to induction of Bf by TNF-alpha. An I-kappaB dominant negative mutant blocked Bf induction by TNF-alpha and reduced the synergistic induction by TNF-alpha and IFN-gamma. In addition, the proteasome inhibitor MG132, which blocks NF-kappaB induction, blocked TNF-alpha-induced Bf promoter activity and the synergistic induction of Bf promoter activity by TNF-alpha and IFN-gamma. LPS was found to induce Bf promoter activity through the same NF-kappaB cis-binding site. These findings suggest that a NF-kappaB cis-binding site between -433 and -423 bp is required for TNF-alpha responsiveness and for TNF-alpha- and IFN-gamma-stimulated synergistic responsiveness of the Bf gene.

Regulation of the transcriptional activity of the nuclear factor-kappaB p65 subunit

Nuclear factor-kappaB (NF-kappaB) is well known for its role in inflammation, immune response, control of cell division and apoptosis. The function of NF-kappaB is primarily regulated by IkappaB family members, which ensure cytoplasmic localisation of the transcription factor in the resting state. Upon stimulus-induced IkappaB degradation, the NF-kappaB complexes move to the nucleus and activate NF-kappaB-dependent transcription. Over the years, a second regulatory mechanism, independent of IkappaB, has become generally accepted. Changes in NF-kappaB transcriptional activity have been assigned to phosphorylation of the p65 subunit by a large variety of kinases in response to different stimuli. Here, we give an overview of the kinases and signalling pathways mediating this process and comment on the players involved in tumour necrosis factor-induced regulation of NF-kappaB transcriptional activity. Additionally, we describe how other posttranslational modifications, such as acetylation and methylation of transcription factors or of the chromatin environment, may also affect NF-kappaB transcriptional activity.

Participation of the calcium/calmodulin-dependent kinases in hydrogen peroxide-induced Ikappa B phosphorylation in human T lymphocytes

NF-kappaB is an important transcription factor that has a role in a variety of responses such as inflammation, oncogenesis, apoptosis, and viral replication. Oxidative stress is well known to induce the activation of NF-kappaB. Cells can be exposed to either endogenously produced oxidants or oxidants produced by surrounding cells. In addition, ischemia reperfusion and certain cancer therapies such as chemotherapy and photodynamic therapy are thought to result in oxygen radical production. Because of the important role that NF-kappaB has in multiple responses, it is critical to determine the mechanisms by which oxidative stress induces NF-kappaB activity. We report that the calmodulin antagonist W-7 and the calcium/calmodulin-dependent (CaM) kinase inhibitors KN-93 and K252a, can block oxidative stress-induced IkappaB phosphorylation in Jurkat T lymphocytes. Furthermore, KN-93 but not KN-92 can block hydrogen peroxide-induced Akt and IKK phosphorylation. In addition, we found that expression of a kinase-dead CaM-KIV construct in two cell lines inhibits IkappaB phosphorylation or degradation and that expression of CaM-KIV augments hydrogen peroxide-induced IkappaB phosphorylation and degradation. Although the CaM kinases appear to be required for this response, increases in intracellular calcium do not appear to be required. These results identify the CaM kinases as potential targets that can be used to minimize NF-kappaB activation in response to oxidative stress.

Mechanisms of constitutive NF-kappaB activation in human prostate cancer cells

BACKGROUND

Activation of the NF-kappaB transcription factor has been previously demonstrated in two androgen receptor negative prostate cancer cell lines. We wished to extend this work to additional prostate cancer cells and to characterize the mechanisms responsible for constitutive NF-kappaB activation.

METHODS

Electrophoretic mobility shift assays were performed to measure NF-kappaB DNA-binding activity in prostate cancer cell lines, and immunohistochemistry was performed to detect nuclear localization of NF-kappaB in prostate cancer tissues. Western blot analysis was used to study the status of IkappaBalpha. Transient transfection assays were employed to characterize the contributions of IkappaB kinase (IKK), MAPK kinase kinases (MAPKKKs), androgen receptor (AR), and tyrosine phosphorylation to the constitutive activation of NF-kappaB in the prostate cancer cell lines.

RESULTS

Constitutive NF-kappaB activity was observed in AR-negative cell lines as well as in the prostate cancer patient samples, but was not present in AR positive cells. A "super-repressor" IkappaBalpha, as well as dominant negative forms of IKKbeta and NF-kappaB-inducing kinase (NIK), and tyrosine kinase inhibition were able to suppress NF-kappaB activity in the cells with constitutive activation.

CONCLUSIONS

The constitutive activation of NF-kappaB observed in prostate cancer cells is likely due to a signal transduction pathway involving tyrosine kinases, NIK, and IKK activation.

Rel/NF-kappa B/I kappa B signal transduction in the generation and treatment of human cancer

The Rel/NF-kappa B family is a group of structurally-related, tightly-regulated transcription factors that control the expression of a multitude of genes involved in key cellular and organismal processes. The Rel/NF-kappa B signal transduction pathway is misregulated in a variety of human cancers, especially ones of lymphoid cell origin, due either to genetic changes (such as chromosomal rearrangements, amplifications, and mutations) or to chronic activation of the pathway by epigenetic mechanisms. Constitutive activation of the Rel/NF-kappa B pathway can contribute to the oncogenic state in several ways, for example, by driving proliferation, by enhancing cell survival, or by promoting angiogenesis or metastasis. In many cases, inhibition of Rel/NF-kappa B activity reverses all or part of the malignant state. Thus, the Rel/NF-kappa B pathway has received much attention as a focal point for clinical intervention.

Estrogen receptor alpha inhibits IL-1beta induction of gene expression in the mouse liver

Estrogens have been suggested to modulate several inflammatory processes. Here, we show that IL-1beta treatment induced the expression of approximately 75 genes in the liver of ovariectomized mice. 17alpha-Ethinyl estradiol (EE) pretreatment reduced the IL-1beta induction of approximately one third of these genes. Estrogen receptor alpha (ERalpha) was required for this inhibitory activity, because EE inhibition of IL-1beta-stimulated gene expression occurred in ERbeta knockout mice, but not in ERalpha knockout mice. EE treatment induced expression of 40 genes, including the transcriptional repressor short heterodimer partner and prostaglandin D synthase, known modulators of nuclear factor-kappaB signaling. However, the ER agonists genistein and raloxifene both inhibited IL-1beta gene induction without stimulating the expression of prostaglandin D synthase, short heterodimer partner, or other ER-inducible genes, indicating that induction of gene expression was not required for ER inhibition of IL-1beta signaling. Finally, the ability of EE to repress IL-1beta gene induction varied among tissues. For example, EE inhibited IL-1beta induction of lipopolysaccharide-induced c-x-c chemokine (LIX) in the liver, but not in the spleen or lung. The degree of EE repression did not correlate with ER expression. cAMP response element binding protein-binding protein (CBP)/p300 levels also varied between tissues. Together, these results are consistent with a model of in vivo ER interference with IL-1beta signaling through a coactivator-based mechanism.

Characterization of the nuclear import and export functions of Ikappa B(epsilon)

Control over the nuclear localization of nuclear factor kappaB/Rel proteins is accomplished in large part through association with members of the inhibitor of kappaB (IkappaB) protein family. For example, the well studied IkappaBalpha protein actively shuttles between the nucleus and the cytoplasm and both inhibits nuclear import and mediates nuclear export of NF-kappaB/Rel proteins. In contrast, the IkappaBbeta protein can inhibit nuclear import of NF-kappaB/Rel proteins but does not remove NF-kappaB/Rel proteins from the nucleus. To further understand how the IkappaB proteins control the nuclear-cytoplasmic distribution of NF-kappaB/Rel proteins, we have characterized the nuclear import and nuclear export functions of IkappaBepsilon. Our results indicate that the IkappaBepsilon protein, like the IkappaBalpha protein, actively shuttles between the nucleus and the cytoplasm. Similar to IkappaBalpha, nuclear import of IkappaBepsilon is mediated by its ankyrin repeat domain and is not blocked by the dominant-negative RanQ69L protein. However, the nuclear import function of the IkappaBepsilon ankyrin repeat domain is markedly less efficient than that of IkappaBalpha, with the result that nuclear shuttling of IkappaBepsilon between the nucleus and the cytoplasm is significantly slower than IkappaBalpha. Nuclear export of IkappaBepsilon is mediated by a short leucine-rich nuclear export sequence (NES)-like sequence ((343)VLLPFDDLKI(352)), located between amino acids 343 and 352. This NES-like sequence is required for RanGTP-dependent binding of IkappaBepsilon to CRM1. Nuclear accumulation of IkappaB(epsilon) is increased by either leptomycin B treatment or alanine substitutions within the IkappaBepsilon-derived NES. A functional NES is required for both efficient cytoplasmic retention and post-induction control of c-Rel by IkappaBepsilon, consistent with the notion that IkappaBepsilon-mediated nuclear export contributes to control over the nucleocytoplasmic distribution of NF-kappaB/Rel proteins.

Biologic sequelae of nuclear factor-kappaB blockade in multiple myeloma: therapeutic applications

The transcription factor nuclear factor-kappaB (NF-kappaB) confers significant survival potential in a variety of tumors. Several established or novel anti-multiple myeloma (anti-MM) agents, such as dexamethasone, thalidomide, and proteasome inhibitors (PS-341), inhibit NF-kappaB activity as part of their diverse actions. However, studies to date have not delineated the effects of specific inhibition of NF-kappaB activity in MM. We therefore investigated the effect of SN50, a cell-permeable specific inhibitor of NF-kappaB nuclear translocation and activity, on MM cells. SN50 induced apoptosis in MM cell lines and patient cells; down-regulated expression of Bcl-2, A1, X-chromosome-linked inhibitor-of-apoptosis protein (XIAP), cellular inhibitor-of-apoptosis protein 1 (cIAP-1), cIAP-2, and survivin; up-regulated Bax; increased mitochondrial cytochrome c release into the cytoplasm; and activated caspase-9 and caspase-3, but not caspase-8. We have previously demonstrated that tumor necrosis factor-alpha (TNF-alpha) is present locally in the bone marrow microenvironment and induces NF-kappaB-dependent up-regulation of adhesion molecules on both MM cells and bone marrow stromal cells, with resultant increased adhesion. In this study, TNF-alpha alone induced NF-kappaB nuclear translocation, cIAP-1 and cIAP-2 up-regulation, and MM cell proliferation; in contrast, SN50 pretreatment sensitized MM cells to TNF-alpha-induced apoptosis and cleavage of caspase-8 and caspase-3, similar to our previous finding of SN50-induced sensitization to apoptosis induced by the TNF-alpha family member TNF-related apoptosis-inducing ligand (TRAIL)/Apo2L. Moreover, SN50 inhibited TNF-alpha-induced expression of another NF-kappaB target gene, intercellular adhesion molecule-1. Although the p38 inhibitor PD169316 did not directly kill MM cells, it potentiated the apoptotic effect of SN50, suggesting an interaction between the p38 and NF-kappaB pathways. Our results therefore demonstrate that NF-kappaB activity in MM cells promotes tumor-cell survival and protects against apoptotic stimuli. These studies provide the framework for targeting NF-kappaB activity in novel biologically based therapies for MM.

Tamoxifen enhancement of TNF-alpha induced MnSOD expression: modulation of NF-kappaB dimerization

Manganese superoxide dismutase (MnSOD) has been shown to suppress the development of cancer. Tamoxifen (TAM), a nonsteroidal anti-estrogen that is widely used in chemotherapy, is known to be a modulator of antioxidant status. However, the mechanism by which TAM mediates antioxidant enzyme induction remains unclear. In this study we investigated TAM enhancement of MnSOD induction by TNF-alpha. The results show that co-treatment with TAM and TNF-alpha increases the MnSOD promoter/enhancer driven luciferase activity, MnSOD mRNA and protein levels. Interestingly, co-treatment with TAM and TNF-alpha drastically decreases the binding activity of the p50/p50 homodimer and increases that of the p50/p65 heterodimer compared to TNF-alpha alone. This change in DNA binding could not be attributed to a decrease in the level of p50, its precursor, p105, or its inhibitors. Furthermore, TAM did not enhance degradation of IkappaB-alpha. These results suggest that p50/p50 homodimer may act as an inhibitory complex of MnSOD expression. Modulation of the DNA binding activity in favor of the p50/p65 complex may enhance NF-kappaB mediated induction of MnSOD by TAM. These findings reveal a potential novel mechanism for the induction of the human MnSOD gene.

SHIP negatively regulates IgE + antigen-induced IL-6 production in mast cells by inhibiting NF-kappa B activity

We demonstrate in this study that IgE + Ag-induced proinflammatory cytokine production is substantially higher in Src homology-2-containing inositol 5'-phosphatase (SHIP)(-/-) than in SHIP(+/+) bone marrow-derived mast cells (BMMCs). Focusing on IL-6, we found that the repression of IL-6 mRNA and protein production in SHIP(+/+) BMMCs requires the enzymatic activity of SHIP, because SHIP(-/-) BMMCs expressing wild-type, but not phosphatase-deficient (D675G), SHIP revert the IgE + Ag-induced increase in IL-6 mRNA and protein down to levels seen in SHIP(+/+) BMMCs. Comparing the activation of various signaling pathways to determine which ones might be responsible for the elevated IL-6 production in SHIP(-/-) BMMCs, we found the phosphatidylinositol 3-kinase/protein kinase B (PKB), extracellular signal-related kinase (Erk), p38, c-Jun N-terminal kinase, and protein kinase C (PKC) pathways are all elevated in IgE + Ag-induced SHIP(-/-) cells. Moreover, inhibitor studies suggested that all these pathways play an essential role in IL-6 production. Looking downstream, we found that IgE + Ag-induced IL-6 production is dependent on the activity of NF-kappa B and that I kappa B phosphorylation/degradation and NF-kappa B translocation, DNA binding and transactivation are much higher in SHIP(-/-) BMMCs. Interestingly, using various pathway inhibitors, it appears that the phosphatidylinositol 3-kinase/PKB and PKC pathways elevate IL-6 mRNA synthesis, at least in part, by enhancing the phosphorylation of I kappa B and NF-kappa B DNA binding while the Erk and p38 pathways enhance IL-6 mRNA synthesis by increasing the transactivation potential of NF-kappa B. Taken together, our data are consistent with a model in which SHIP negatively regulates NF-kappa B activity and IL-6 synthesis by reducing IgE + Ag-induced phosphatidylinositol-3,4,5-trisphosphate levels and thus PKB, PKC, Erk, and p38 activation.

Intracellular signal transduction in eosinophils and its clinical significance

The incidence and prevalence of allergic diseases such as asthma and allergic rhinitis have recently been increasing worldwide. Eosinophils are the principal effector cells for the pathogenesis of allergic inflammation via the secretion of highly cytotoxic granular proteins including eosinophil cationic protein, major basic protein and eosinophil protein X. Blood and tissue eosinophilia is a common manifestation of late-phase allergic inflammation causing tissue damage. The development of eosinophilia correlates with the production of haematopoietic cytokines including interleukin (IL)-3. IL-5 and granulocyte macrophage colony stimulating factor (GM-CSF), and eosinophil-specific chemoattractant, eotaxin, from T-lymphocytes and the epithelium respectively. Elucidation of intracellular mechanisms that control the activation, apoptosis and recruitment of eosinophils to tissues is therefore fundamental in understanding these disease processes and provides targets for novel drug therapy. Over the past decade, there has been intensive investigation for the intracellular signal transduction regulating various biological functions of eosinophils and their roles in the pathogenesis of eosinophil-related diseases. This review will emphasize on the cytokine and chemokine-mediated signal transductions including the RAS-RAF-mitogen-activated protein kinases (MAPK), Janus kinases (JAK)-signal transducers and activators of transcription (STAT), phosphatidylinositol 3-kinase (PI3K) and nuclear factor-kappa B (NF-kappaB), and various antagonists of receptors and inhibitors of intracellular signaling molecules as potential therapeutic agents of allergic diseases.

Genomic organization and expression of the rearranged REL proto-oncogene in the human B-cell lymphoma cell line RC-K8

The human large B-cell lymphoma cell line RC-K8 has a rearranged REL locus that is transcribed into a chimeric mRNA, termed REL-NRG (Non-Rel Gene). By analyzing the recently completed human genome sequence, we have found that the normal REL and NRG loci are separated by approximately 28 megabase pairs on chromosome 2, suggesting that a deletion created the REL-NRG locus in RC-K8 cells. Using computer-based and molecular approaches, we have determined the structure of the altered REL locus in RC-K8 cells. The REL-NRG transcript is encoded by 7 REL exons and 6 NRG-derived exons. Direct DNA sequencing has identified the site of the REL-NRG fusion in RC-K8 cells. We also show that both wild-type c-Rel and c-Rel-Nrg proteins are expressed and in a complex in RC-K8 cells. Furthermore, like c-Rel, c-Rel-Nrg is a cytoplasmic protein when overexpressed in fibroblasts in culture and can bind to a kappaB DNA site in vitro.

Immortalized embryonic mouse fibroblasts lacking the RelA subunit of transcription factor NF-kappaB have a malignantly transformed phenotype

The RelA transcription factor is part of dimeric complexes, most commonly either p50-RelA (NF-kappaB) heterodimers or RelA homodimers, that control a variety of cellular processes. Immortalized embryonic fibroblasts established from rela knockout mice have previously been shown to be more sensitive to apoptosis induced by tumor necrosis factor (TNF) than are control fibroblasts. In this report, we show that one line of rela-/- fibroblasts has additional phenotypes that distinguish them from control mouse fibroblasts. As compared to normal 3T3 cells, RelA-deficient fibroblasts have a spindled morphology, are less adherent to culture dishes, grow to a higher saturation density, and can form colonies in soft agar. These properties are consistent with a weakly transformed phenotype for rela-/- cells. Furthermore, RelA-deficient fibroblasts can form tumors in immunodeficient mice, but these tumors regress, probably because of the sensitivity of these cells to TNF. The ability of rela-/- fibroblasts to form colonies in soft agar can be reverted by re-expression of wild-type mouse RelA, but not by expression of RelA mutants that cannot form homodimers. There is no clear correlation between the absence of RelA and the levels of expression of other Rel/NF-kappaB family members or adhesion proteins (ICAM-1 and VCAM-1) whose genes have upstream kappaB sites. Taken together, these results suggest that RelA has tumor suppressing activity under some circumstances and that RelA complexes are involved in the control of a variety of cellular properties associated with oncogenesis.

In adenovirus type 12 tumorigenic cells, major histocompatibility complex class I transcription shutoff is overcome by induction of NF-kappaB and relief of COUP-TFII repression

The surface levels of major histocompatibility complex class I antigens are diminished on tumorigenic adenovirus type 12 (Ad12)-transformed cells, enabling them to escape from immunosurveillant cytotoxic T lymphocytes (CTLs). This is due to the down-regulation of the class I transcriptional enhancer, in which there is strong binding of the repressor COUP-TFII and lack of binding of the activator NF-kappaB. Even though NF-kappaB (p65/p50) translocates to the nuclei of Ad12-transformed cells, it fails to bind to DNA efficiently due to the hypophosphorylation of the p50 subunit. In this study, tumor necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) were shown to promote degradation of the NF-kappaB cytoplasmic inhibitor IkappaBalpha and permit the nuclear translocation of a phosphorylated form of NF-kappaB that is capable of binding DNA. Interestingly, when Ad12-transformed cells were treated with TNF-alpha or IL-1beta, class I gene transcription substantially increased when transcriptional repression by COUP-TFII was blocked. This indicates that in cytokine-treated Ad12-transformed cells, COUP-TFII is able to repress activation of class I transcription by newly nucleus-localized NF-kappaB. Our results suggest that Ad12 likely employs a "fail-safe" mechanism to ensure that the transcription of class I genes remains tightly repressed under various physiological conditions, thus providing tumorigenic Ad12-transformed cells with a means of escaping CTL recognition and lysis.

Enhancement of nuclear factor-kappa B acetylation by coactivator p300 and HIV-1 Tat proteins

Nuclear factor (NF)-kappaB transcription factors are involved in the control of a large number of normal cellular and organismal processes, such as immune and inflammatory responses, developmental processes, cellular growth, and apoptosis. Transcription of the human immunodeficiency virus type 1 (HIV-1) genome depends on the intracellular environment where the integrate viral DNA is regulated by a complex interplay among viral regulatory proteins, such as Tat, and host cellular transcription factors, such as NF-kappaB, interacting with the viral long terminal repeat region. CBP (CREB-binding protein) and p300, containing an intrinsic histone acetyltransferase (HAT) activity, have emerged as coactivators for various DNA-binding transcription factors. Here, we show that the p50 subunit as well as the p50/p65 of NF-kappaB, and not other factors such as SP1, TFIIB, polymerase II, TFIIA, or p65, can be acetylated by CBP/p300 HAT domain. Acetylation of p50 was completely dependent on the presence of both HAT domain and Tat proteins, implying that Tat influences the transcription machinery by aiding CBP/p300 to acquire new partners and increase its functional repertoire. Three lysines, Lys-431, Lys-440, and Lys-441 in p50 were all acetylated in vitro, and a sequence similarity among p50, p53, Tat, and activin receptor type I on these particular lysines was observed. All proteins have been shown to be acetylated by the CBP/p300 HAT domain. Acetylated p50 increases its DNA binding properties, as evident by streptavidin/biotin pull-down assays when using labeled NF-kappaB oligonucleotides. Increased DNA binding on HIV-1 long terminal repeat coincided with increases in the rate of transcription. Therefore, we propose that acetylation of the DNA binding domain of NF-kappaB aids in nuclear translocation and enhanced transcription and also suggest that the substrate specificity of CBP/p300 can be altered by small peptide molecules, such as HIV-encoded Tat.

Inhibitor of apoptosis protein from Orgyia pseudotsugata nuclear polyhedrosis virus provides a costimulatory signal required for optimal proliferation of developing thymocytes

The inhibitors of apoptosis proteins (IAPs) constitute a family of endogenous inhibitors that control apoptosis in the cell by inhibiting caspase processing and activity. IAPs are also implicated in cell division, cell cycle regulation, and cancer. To address the role of IAPs in thymus development and homeostasis, we generated transgenic mice expressing IAP generated from the baculovirus Orgyia pseudotsugata nuclear polyhedrosis virus (OpIAP). Developing thymocytes expressing OpIAP show increased nuclear levels of NF-kappaB and reduced cytoplasmic levels of its inhibitor, IkappaBalpha. In mature thymocytes, OpIAP induces optimal activation and proliferation after TCR triggering in the absence of a costimulatory signal. OpIAP expression in immature thymocytes blocks TCR-induced apoptosis. Taken together, our data illustrate the pleiotropism of OpIAP in vivo.