RAG2-/-, I kappa B-alpha-/- chimeras display a psoriasiform skin disease

NF-κB gene signature predicts prostate cancer progression

In many patients with prostate cancer, the cancer will be recurrent and eventually progress to lethal metastatic disease after primary treatment, such as surgery or radiation therapy. Therefore, it would be beneficial to better predict which patients with early-stage prostate cancer would progress or recur after primary definitive treatment. In addition, many studies indicate that activation of NF-κB signaling correlates with prostate cancer progression; however, the precise underlying mechanism is not fully understood. Our studies show that activation of NF-κB signaling via deletion of one allele of its inhibitor, IκBα, did not induce prostatic tumorigenesis in our mouse model. However, activation of NF-κB signaling did increase the rate of tumor progression in the Hi-Myc mouse prostate cancer model when compared with Hi-Myc alone. Using the nonmalignant NF-κB-activated androgen-depleted mouse prostate, a NF-κB-activated recurrence predictor 21 (NARP21) gene signature was generated. The NARP21 signature successfully predicted disease-specific survival and distant metastases-free survival in patients with prostate cancer. This transgenic mouse model-derived gene signature provides a useful and unique molecular profile for human prostate cancer prognosis, which could be used on a prostatic biopsy to predict indolent versus aggressive behavior of the cancer after surgery.

Activation of NF-kappa B signaling promotes growth of prostate cancer cells in bone

Patients with advanced prostate cancer almost invariably develop osseous metastasis. Although many studies indicate that the activation of NF-κB signaling appears to be correlated with advanced cancer and promotes tumor metastasis by influencing tumor cell migration and angiogenesis, the influence of altered NF-κB signaling in prostate cancer cells within boney metastatic lesions is not clearly understood. While C4-2B and PC3 prostate cancer cells grow well in the bone, LNCaP cells are difficult to grow in murine bone following intraskeletal injection. Our studies show that when compared to LNCaP, NF-κB activity is significantly higher in C4-2B and PC3, and that the activation of NF-κB signaling in prostate cancer cells resulted in the increased expression of the osteoclast inducing genes PTHrP and RANKL. Further, conditioned medium derived from NF-κB activated LNCaP cells induce osteoclast differentiation. In addition, inactivation of NF-κB signaling in prostate cancer cells inhibited tumor formation in the bone, both in the osteolytic PC3 and osteoblastic/osteoclastic mixed C4-2B cells; while the activation of NF-κB signaling in LNCaP cells promoted tumor establishment and proliferation in the bone. The activation of NF-κB in LNCaP cells resulted in the formation of an osteoblastic/osteoclastic mixed tumor with increased osteoclasts surrounding the new formed bone, similar to metastases commonly seen in patients with prostate cancer. These results indicate that osteoclastic reaction is required even in the osteoblastic cancer cells and the activation of NF-κB signaling in prostate cancer cells increases osteoclastogenesis by up-regulating osteoclastogenic genes, thereby contributing to bone metastatic formation.

Myeloid cells control termination of lung inflammation through the NF-kappaB pathway

Although acute lung inflammation in response to local or systemic infection involves myeloid and nonmyeloid cells, the interplay between different cell types remains poorly defined. Since NF-kappaB is a key transcription factor for innate immunity, we investigated whether dysregulated NF-kappaB activation in myeloid cells impacts inflammatory signaling in nonmyeloid cells and generation of neutrophilic lung inflammation in response to systemic endotoxemia. We generated bone marrow chimeras by fetal liver transplantation of cells deficient in IkappaBalpha or p50 into lethally irradiated NF-kappaB reporter transgenic mice. No differences were apparent between bone marrow chimeras in the absence of an inflammatory stimulus; however, following intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS), IkappaBalpha- or p50-deficient bone marrow chimeras showed increased NF-kappaB activation in nonhematopoietic cells, exaggerated neutrophilic inflammation, and higher mortality compared with untransplanted reporter mice and wild-type bone marrow chimeras. Primary bone marrow-derived macrophages (BMDM) from IkappaBalpha(-/-) or p50(-/-) exhibited increased NF-kappaB activation and macrophage inflammatory protein-2 production after LPS treatment compared with wild-type cells, and coculture of BMDM with lung epithelial (A549) cells resulted in increased NF-kappaB activation in A549 cells and excess IL-8 production by these epithelial cells. These studies indicate an important role for inhibitory members of the NF-kappaB family acting specifically within myeloid cells to limit inflammatory responses in the lungs.

Epstein–Barr virus-encoded LMP1 induces a hyperproliferative and inflammatory gene expression programme in cultured keratinocytes

SCC12F cells are a line of keratinocytes that retain the capacity for terminal differentiation in vitro. We showed previously that the Epstein–Barr virus (EBV)-encoded oncogene latent membrane protein 1 (LMP1) altered SCC12F morphology in vitro, downregulated cell–cell-adhesion molecule expression and promoted cell motility. In organotypic raft culture, LMP1-expressing cells failed to stratify and formed poorly organized structures which displayed impaired terminal differentiation. To understand better the mechanism(s) by which LMP1 induces these effects, we generated SCC12F cells in which LMP1 expression is inducible. Following induction, these cells exhibited phenotypic changes similar to those observed previously and allowed us to investigate the effects of LMP1 expression on cellular pathways associated with growth, differentiation and morphology. Using microarrays and a number of confirmatory techniques, we identified sets of differentially expressed genes that are characteristically expressed in inflammatory and hyperproliferative epidermis, including chemokines, cytokines and their receptors, growth factors involved in promoting epithelial cell motility and proliferation and signalling molecules that regulate actin filament reorganization and cell movement. Among the genes whose expression was differentially induced significantly by LMP1, the induction of IL-1β and IL-1α was of particular interest, as many of the LMP1-regulated genes identified are established targets of these cytokines. Our findings suggest that alterations in the IL-1 signalling network may be responsible for many of the changes in host-cell gene expression induced in response to LMP1. Identification of these LMP1-regulated genes helps to define the mechanism(s) by which this oncoprotein influences cellular pathways that regulate terminal differentiation, cell motility and inflammation.

The nuclear factor-kappaB pathway controls the progression of prostate cancer to androgen-independent growth

Typically, the initial response of a prostate cancer patient to androgen ablation therapy is regression of the disease. However, the tumor will progress to an "androgen-independent" stage that results in renewed growth and spread of the cancer. Both nuclear factor-kappaB (NF-kappaB) expression and neuroendocrine differentiation predict poor prognosis, but their precise contribution to prostate cancer progression is unknown. This report shows that secretory proteins from neuroendocrine cells will activate the NF-kappaB pathway in LNCaP cells, resulting in increased levels of active androgen receptor (AR). By blocking NF-kappaB signaling in vitro, AR activation is inhibited. In addition, the continuous activation of NF-kappaB signaling in vivo by the absence of the IkappaBalpha inhibitor prevents regression of the prostate after castration by sustaining high levels of nuclear AR and maintaining differentiated function and continued proliferation of the epithelium. Furthermore, the NF-kappaB pathway was activated in the ARR(2)PB-myc-PAI (Hi-myc) mouse prostate by cross-breeding into a IkappaBalpha(+/-) haploid insufficient line. After castration, the mouse prostate cancer continued to proliferate. These results indicate that activation of NF-kappaB is sufficient to maintain androgen-independent growth of prostate and prostate cancer by regulating AR action. Thus, the NF-kappaB pathway may be a potential target for therapy against androgen-independent prostate cancer.

Anti-inflammatory functions of glucocorticoid-induced genes

There is a broad consensus that glucocorticoids (GCs) exert anti-inflammatory effects largely by inhibiting the function of nuclear factor kappaB (NFkappaB) and consequently the transcription of pro-inflammatory genes. In contrast, side effects are thought to be largely dependent on GC-induced gene expression. Biochemical and genetic evidence suggests that the positive and negative effects of GCs on transcription can be uncoupled from one another. Hence, novel GC-related drugs that mediate inhibition of NFkappaB but do not activate gene expression are predicted to retain therapeutic effects but cause fewer or less severe side effects. Here, we critically re-examine the evidence in favor of the consensus, binary model of GC action and discuss conflicting evidence, which suggests that anti-inflammatory actions of GCs depend on the induction of anti-inflammatory mediators. We propose an alternative model, in which GCs exert anti-inflammatory effects at both transcriptional and post-transcriptional levels, both by activating and inhibiting expression of target genes. The implications of such a model in the search for safer anti-inflammatory drugs are discussed.

Regulation of IgE homeostasis, and the identification of potential targets for therapeutic intervention

Atopic allergies have increased during the past 20-30 years in frequency quite dramatically and in many countries have reached almost epidemic proportions. Allergies have thereby become one of the major medical issues of the western world. Immunoglobulin E (IgE) is here a central player. IgE is the Ig class that is present in the lowest concentration in human plasma. IgG is, for example, 10 000 to 1 million times more abundant than IgE. However, despite of its low plasma levels IgE is a very important inducer of inflammation, due to its interaction with high-affinity receptors on mast cell and basophils. IgE has been conserved as a single active gene in all placental mammals studied, and the expression of this gene is under a very stringent control, most likely due to its very potent inflammatory characteristics. IgE expression is being regulated at many levels: by cytokines, switch region length, positive and negatively acting transcription factors and suppressors of cytokine signaling (SOCS). In addition, the plasma half-life differs markedly for IgG and IgE, with 21 and 2.5 days, respectively. This review summarizes the rapid progress in our understanding of the complex network of regulatory mechanisms acting on IgE and also how this new information may help us in our efforts to control IgE-mediated inflammatory conditions.

Inhibition of the nuclear factor-kappaB signaling pathway by leflunomide or triptolide also inhibits the anthralin-induced inflammatory response but does not affect keratinocyte growth inhibition

We performed this study to determine the relationship between activation of nuclear factor (NF)-kappaB and inhibition of keratinocyte growth by anthralin, which not only might be useful for a better understanding of the role of NF-kappaB in the pathogenesis of psoriasis, but also indicate whether the inflammatory reaction induced by anthralin is inseparable from its antipsoriatic activity. The involvement of NF-kappaB was assessed using the antipsoriatic drugs leflunomide and triptolide (T0) as effectors, since they can inhibit NF-kappaB activation induced by anthralin. The results showed that the inhibition of keratinocyte growth by anthralin was not related to the activation of NF-kappaB. Using sodium salicylate, a known NF-kappaB inhibitor, further confirmed this conclusion. Thus it might be possible to inhibit the inflammatory response induced by anthralin via repression of NF-kappaB activation. We found that leflunomide or T0 could significantly inhibit the mRNA overexpression of interleukin-8 and intercellular adhesion molecule-1 in keratinocytes induced by anthralin. Taken together, our data indicate that the growth inhibition of anthralin is related to the NF-kappaB-independent signaling pathway, and that leflunomide or T0 could control proinflammatory cytokine expression induced by anthralin via inhibiting the activation of NF-kappaB.

Differential expression of phosphorylated NF-kappaB/RelA in normal and psoriatic epidermis and downregulation of NF-kappaB in response to treatment with etanercept

Etanercept, a recombinant human tumor necrosis factor (TNF) receptor fusion protein, is FDA approved for psoriasis and psoriatic arthritis. TNFalpha increases the synthesis of proinflammatory cytokines and leads to the activation of multiple signaling pathways, including nuclear factor kappa B (NF-kappaB). The Rel/NF-kappaB transcription factors play a central role in numerous cellular processes, including the stress response and keratinocyte proliferation and differentiation. Utilizing a phosphorylation-specific antibody, we examined the expression of active nuclear NF-kappaB/RelA via immunohistochemistry in normal skin, non-lesional psoriatic skin, lesional psoriatic skin, and lesional skin from patients treated with etanercept. There was no expression of active nuclear NF-kappaB in the normal epidermis, whereas a basal level of constitutive active phosphorylated NF-kappaB/RelA was present in uninvolved epidermis from psoriasis patients. There was also significant upregulation of active phosphorylated NF-kappaB/RelA in the epidermis from psoriatic plaques. Serial biopsies from psoriasis patients treated with etanercept at 1, 3, and 6 mo demonstrated a significant downregulation of phosphorylated NF-kappaB/RelA, which correlated with decreases in epidermal thickness, restoration of normal markers of keratinocyte differentiation, and clinical outcomes. These data suggest that activation of NF-kappaB plays a significant role in the pathogenesis of psoriasis and that a potential mechanism of action for TNF-targeting agents is downregulation of NF-kappaB transcriptional activity.

Upregulation of 8-lipoxygenase in the dermatitis of IkappaB-alpha-deficient mice

Neonatal mice deficient in IkappaB-alpha, an inhibitor of the ubiquitous transcription factor NF-kappaB, develop severe and widespread dermatitis shortly after birth. In humans, inflammatory skin disorders such as psoriasis are associated with accumulation in the skin of the unusual arachidonic acid metabolite 12R-hydroxyeicosatetraenoic acid (12R-HETE), a product of the enzyme 12R-lipoxygenase. To examine the etiology of the murine IkappaB-alpha-deficient skin phenotype, we investigated the expression of lipoxygenases and the metabolism of exogenous arachidonic acid in the skin. In the IkappaB-alpha-deficient animals, the major lipoxygenase metabolite was 8S-HETE, formed together with a minor amount of 12S-HETE; 12R-HETE synthesis was undetectable. Skin from the wild-type littermates formed 12S-HETE as the almost exclusive lipoxygenase metabolite. Upregulation of 8S-lipoxygenase (8-LOX) in IkappaB-alpha-deficient mice was confirmed at the transcriptional and translational level using ribonuclease protection assay and western analysis. In immunohistochemical studies, increased expression of 8-LOX was detected in the stratum granulosum of the epidermis. In the stratum granulosum, 8-LOX may be involved in the terminal differentiation of keratinocytes. Although mouse 8S-lipoxygenase and human 12R-lipoxygenase are not ortholog genes, we speculate that in mouse and humans the two different enzymes may fulfill equivalent functions in the progression of inflammatory dermatoses.

The regulation of immunoglobulin E class-switch recombination

Immunoglobulin E (IgE) isotype antibodies are associated with atopic disease, namely allergic rhinitis, asthma and atopic dermatitis, but are also involved in host immune defence mechanisms against parasitic infection. The commitment of a B cell to isotype class switch to an IgE-producing cell is a tightly regulated process, and our understanding of the regulation of IgE-antibody production is central to the prevention and treatment of atopic disease. Both those that are presently in use and potential future therapies to prevent IgE-mediated disease take advantage of our existing knowledge of the specific mechanisms that are required for IgE class switching.

Nuclear factor-kappaB (NF-kappaB) regulates proliferation and branching in mouse mammary epithelium

The nuclear factor-kappaB (NF-kappaB) family of transcription factors has been shown to regulate proliferation in several cell types. Although recent studies have demonstrated aberrant expression or activity of NF-kappaB in human breast cancer cell lines and tumors, little is known regarding the precise role of NF-kappaB in normal proliferation and development of the mammary epithelium. We investigated the function of NF-kappaB during murine early postnatal mammary gland development by observing the consequences of increased NF-kappaB activity in mouse mammary epithelium lacking the gene encoding IkappaBalpha, a major inhibitor of NF-kappaB. Mammary tissue containing epithelium from inhibitor kappaBalpha (IkappaBalpha)-deficient female donors was transplanted into the gland-free mammary stroma of wild-type mice, resulting in an increase in lateral ductal branching and pervasive intraductal hyperplasia. A two- to threefold increase in epithelial cell number was observed in IkappaBalpha-deficient epithelium compared with controls. Epithelial cell proliferation was strikingly increased in IkappaBalpha-deficient epithelium, and no alteration in apoptosis was detected. The extracellular matrix adjacent to IkappaBalpha-deficient epithelium was reduced. Consistent with in vivo data, a fourfold increase in epithelial branching was also observed in purified IkappaBalpha-deficient primary epithelial cells in three-dimensional culture. These data demonstrate that NF-kappaB positively regulates mammary epithelial proliferation, branching, and functions in maintenance of normal epithelial architecture during early postnatal development.