Divergent gene regulation and growth effects by NF-kappa B in epithelial and mesenchymal cells of human skin

Functional polymorphism in NFKB1 promoter is related to the risks of oral squamous cell carcinoma occurring on older male areca (betel) chewers

Areca (betel)-chewing is tightly associated with the high prevalence of oral squamous cell carcinoma (OSCC) in Asians. NFKB1 encodes a 105kDa protein that can be processed to produce p50 subunit of nuclear factor-kappaB protein complex. A insertion (ins)/deletion (del) polymorphism (-94ins/delATTG) in NFKB1 promoter, which may drive the ins allele two-fold increase in NFKB1 transcription relative to del allele, was recently found. This study identified that the odds ratio in OSCC carrying ins allelotype were 1.78 relative to controls (56.7 vs 41.8%) in subjects more than 50 years old. L allelotype of Heme oxygenase-1 (HO-1), accounting for a long (GT)(n) repeat in HO-1 promoter, is associated with the risks of areca-related OSCC. Subjects carried both NFKB1 ins and HO-1 L allelotypes had significant risks for various subsets of OSCC. OSCC with lymph node metastasis or advanced stage had significantly higher frequency of NFKB1 ins and HO-1 L allelotypes. This study suggested that the functional NFKB1promoter polymorphism could be valuable for assessment of cancer risk.

Targeted deletion of the integrin beta4 signaling domain suppresses laminin-5-dependent nuclear entry of mitogen-activated protein kinases and NF-kappaB, causing defects in epidermal growth and migration

The alpha6beta4 integrin-a laminin-5 receptor-mediates assembly of hemidesmosomes and recruitment of Shc and phosphoinositide 3-kinase through the unique cytoplasmic extension of beta4. Mice carrying a targeted deletion of the signaling domain of beta4 develop normally and do not display signs of skin fragility. The epidermis of these mice contains well-structured hemidesmosomes and adheres stably to the basement membrane. However, it is hypoplastic due to reduced proliferation of basal keratinocytes and undergoes wound repair at a reduced rate. Keratinocytes from beta4 mutant mice undergo extensive spreading but fail to proliferate and migrate in response to epidermal growth factor (EGF) on laminin-5. EGF causes significant phosphorylation of extracellular signal-regulated kinase (ERK) and Jun N-terminal protein kinase (JNK) and phosphorylation and degradation of IkappaB in beta4 mutant cells adhering to laminin-5. Unexpectedly, however, ERK, JNK, and NF-kappaB remain in the cytoplasm in beta4 mutant cells on laminin-5, whereas they enter effectively into the nucleus in the same cells on fibronectin or in wild-type cells on both matrix proteins. Inhibitor studies indicate that alpha6beta4 promotes keratinocyte proliferation and migration through its effect on NF-kappaB and P-JNK. These findings provide evidence that beta4 signaling promotes epidermal growth and wound healing through a previously unrecognized effect on nuclear translocation of NF-kappaB and mitogen-activated protein kinases.

NF-kB in development and progression of human cancer

The nuclear factor kB (NF-kB) comprises a family of transcription factors involved in the regulation of a wide variety of biological responses. NF-kB plays a well-known function in the regulation of immune responses and inflammation, but growing evidences support a major role in oncogenesis. NF-kB regulates the expression of genes involved in many processes that play a key role in the development and progression of cancer such as proliferation, migration and apoptosis. Aberrant or constitutive NF-kB activation has been detected in many human malignancies. In recent years, numerous studies have focused on elucidating the functional consequences of NF-kB activation as well as its signaling mechanisms. NF-kB has turned out to be an interesting therapeutic target for treatment of cancer.

Notch signaling in the integrated control of keratinocyte growth/differentiation and tumor suppression

Oncogenesis is closely linked to abnormalities in cell differentiation. Notch signaling provides an important form of intercellular communication involved in cell fate determination, stem cell potential and differentiation. Here we review the role of this pathway in the integrated growth/differentiation control of the keratinocyte cell type, and the maintenance of normal skin homeostasis. In parallel with the pro-differentiation function of Notch1 in keratinocytes, we discuss recent evidence pointing to a tumor suppressor function of this gene in both mouse skin and human cervical carcinogenesis. The possibility that Notch signaling elicits signals with a duality of growth positive and negative function will be discussed.

CDK4 regulation by TNFR1 and JNK is required for NF-kappaB-mediated epidermal growth control

Nuclear factor kappaB (NF-kappaB) mediates homeostatic growth inhibition in the epidermis, and a loss of NF-kappaB function promotes proliferation and oncogenesis. To identify mechanisms responsible for these effects, we impaired NF-kappaB action in the epidermis by three different genetic approaches, including conditional NF-kappaB blockade. In each case, epidermal hyperplasia was accompanied by an increase in both protein levels and tissue distribution of the G1 cell cycle kinase, CDK4. CDK4 up-regulation required intact TNFR1 and c-Jun NH2-terminal kinase (JNK) function. Cdk4 gene deletion concomitant with conditional NF-kappaB blockade demonstrated that CDK4 is required for growth deregulation. Therefore, epidermal homeostasis depends on antagonist regulation of CDK4 expression by NF-kappaB and TNFR1/JNK.

Nuclear factor-kappaB: its role in health and disease

Nuclear factor-kappaB (NF-kappaB) is a major transcription factor that plays an essential role in several aspects of human health including the development of innate and adaptive immunity. The dysregulation of NF-kappaB is associated with many disease states such as AIDS, atherosclerosis, asthma, arthritis, cancer, diabetes, inflammatory bowel disease, muscular dystrophy, stroke, and viral infections. Recent evidence also suggests that the dysfunction of NF-kappaB is a major mediator of some human genetic disorders. Appropriate regulation and control of NF-kappaB activity, which can be achieved by gene modification or pharmacological strategies, would provide a potential approach for the management of NF-kappaB related human diseases. This review summarizes the current knowledge of the physiological and pathophysiological functions of NF-kappaB and its possible role as a target of therapeutic intervention

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.

NF-kappaB RelA opposes epidermal proliferation driven by TNFR1 and JNK

NF-kappaB inhibition promotes epidermal tumorigenesis; however, whether this reflects an underlying role in homeostasis or a special case confined to neoplasia is unknown. Embryonic lethality of mice lacking NF-kappaB RelA has hindered efforts to address this. We therefore generated developmentally mature RelA(-/-) skin. RelA(-/-) epidermis displays hyperplasia without abnormal differentiation, inflammation, or apoptosis. Hyperproliferation is TNFR1-dependent because Tnfr1 deletion normalized cell division. TNFR1-dependent JNK activation occurred in RelA(-/-) epidermis, and JNK inhibition abolished hyperproliferation due to RelA deficiency. Thus, RelA antagonizes TNFR1-JNK proliferative signals in epidermis and plays a nonredundant role in restraining epidermal growth.

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

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

Identification of Naf1/ABIN-1 among TNF-alpha-induced expressed genes in human synoviocytes using oligonucleotide microarrays

The cytokine tumor necrosis factor alpha (TNF-alpha) is a critical effector of the pathogenesis of rheumatoid arthritis (RA). We used oligonucleotide microarray (OM) analysis to assess TNF-alpha-modulated gene expression in cultured primary human synoviocytes in vitro. Genes identified include cytokines and inflammatory mediators, extracellular matrix and adhesion molecules, cell cycle and proliferation related proteins, transcription related proteins, and apoptotic mediators. OM identified 1185 differentially expressed genes in TNF-alpha-treated synoviocytes. The regulation of Nef-associated factor-1 (Naf1), an A20-binding, nuclear factor kappa B (NFkappaB) inhibitory protein was probed further given its putative role as an endogenous brake for the expression of some TNF-alpha-driven genes. Naf1 mRNA levels were higher in synovial biopsies from patients with active RA and seronegative arthropathy than in those from patients with osteoarthritis. These findings underscore the value of transcriptome analysis in cytokine-activated synoviocyte cultures in vitro as a means of identifying disease-associated genes in human arthritis, and implicate Naf1 as a potential modulator of TNF-alpha bioactivity in RA.

Microarray analysis of the involution switch

Mammary epithelial cells (MEC) undergo a series of developmental decisions during a pregnancy cycle. The switches from proliferation to differentiation to secretion and then to cell death are precisely controlled. In order to identify critical changes associated with the transition from a secretory phenotype during lactation to dedifferentiation and cell death, we have undertaken a microarray analysis of mouse mammary gland development. We have focused on the involution switch and on the transcription profiles of genes that are targets of transcription factors known to influence involution and apoptosis. Our results show that both Stat3 and NF-kB target genes are induced by the involution switch while Stat5 target genes are distinct from Stat3 induced genes. Furthermore, a substantial number of genes that were specifically upregulated at the start of involution are regulators of inflammation and the acute phase response. These results provide a novel insight into the involution process and demonstrate the value of microarray analysis in defining molecular events associated with critical developmental transitions in mammary gland.