Showing papers by "Michael Karin published in 2007"

A cytokine-mediated link between innate immunity, inflammation, and cancer

Abstract: It has been established that cancer can be promoted and/or exacerbated by inflammation and infections. Indeed, chronic inflammation orchestrates a tumor-supporting microenvironment that is an indispensable participant in the neoplastic process. The mechanisms that link infection, innate immunity, inflammation, and cancer are being unraveled at a fast pace. Important components in this linkage are the cytokines produced by activated innate immune cells that stimulate tumor growth and progression. In addition, soluble mediators produced by cancer cells recruit and activate inflammatory cells, which further stimulate tumor progression. However, inflammatory cells also produce cytokines that can limit tumor growth. Here we provide an overview of the current understanding of the role of inflammation-induced cytokines in tumor initiation, promotion, and progression.

Gender Disparity in Liver Cancer Due to Sex Differences in MyD88-Dependent IL-6 Production

Abstract: Hepatocellular carcinoma (HCC), the most common liver cancer, occurs mainly in men. Similar gender disparity is seen in mice given a chemical carcinogen, diethylnitrosamine (DEN). DEN administration caused greater increases in serum interleukin-6 (IL-6) concentration in males than it did in females. Furthermore, ablation of IL-6 abolished the gender differences in hepatocarcinogenesis in mice. DEN exposure promoted production of IL-6 in Kupffer cells (KCs) in a manner dependent on the Toll-like receptor adaptor protein MyD88, ablation of which also protected male mice from DEN-induced hepatocarcinogenesis. Estrogen inhibited secretion of IL-6 from KCs exposed to necrotic hepatocytes and reduced circulating concentrations of IL-6 in DEN-treated male mice. We propose that estrogen-mediated inhibition of IL-6 production by KCs reduces liver cancer risk in females, and these findings may be used to prevent HCC in males.

A large noncoding RNA is a marker for murine hepatocellular carcinomas and a spectrum of human carcinomas.

Abstract: A large noncoding RNA is a marker for murine hepatocellular carcinomas and a spectrum of human carcinomas

Epithelial-cell-intrinsic IKK-β expression regulates intestinal immune homeostasis

Abstract: Intestinal epithelial cells (IECs) provide a primary physical barrier against commensal and pathogenic microorganisms in the gastrointestinal (GI) tract, but the influence of IECs on the development and regulation of immunity to infection is unknown1. Here we show that IEC-intrinsic IκB kinase (IKK)-β-dependent gene expression is a critical regulator of responses of dendritic cells and CD4+ T cells in the GI tract. Mice with an IEC-specific deletion of IKK-β show a reduced expression of the epithelial-cell-restricted cytokine thymic stromal lymphopoietin in the intestine and, after infection with the gut-dwelling parasite Trichuris, fail to develop a pathogen-specific CD4+ T helper type 2 (TH2) response and are unable to eradicate infection. Further, these animals show exacerbated production of dendritic-cell-derived interleukin-12/23p40 and tumour necrosis factor-α, increased levels of CD4+ T-cell-derived interferon-γ and interleukin-17, and develop severe intestinal inflammation. Blockade of proinflammatory cytokines during Trichuris infection ablates the requirement for IKK-β in IECs to promote CD4+ TH2 cell-dependent immunity, identifying an essential function for IECs in tissue-specific conditioning of dendritic cells and limiting type 1 cytokine production in the GI tract. These results indicate that the balance of IKK-β-dependent gene expression in the intestinal epithelium is crucial in intestinal immune homeostasis by promoting mucosal immunity and limiting chronic inflammation.

Interplay of IKK/NF-κB signaling in macrophages and myofibers promotes muscle degeneration in Duchenne muscular dystrophy

Abstract: Duchenne muscular dystrophy (DMD) is a lethal X-linked disorder associated with dystrophin deficiency that results in chronic inflammation and severe skeletal muscle degeneration. In DMD mouse models and patients, we find that IkappaB kinase/NF-kappaB (IKK/NF-kappaB) signaling is persistently elevated in immune cells and regenerative muscle fibers. Ablation of 1 allele of the p65 subunit of NF-kappaB was sufficient to improve pathology in mdx mice, a model of DMD. In addition, conditional deletion of IKKbeta in mdx mice elucidated that NF-kappaB functions in activated macrophages to promote inflammation and muscle necrosis and in skeletal muscle fibers to limit regeneration through the inhibition of muscle progenitor cells. Furthermore, specific pharmacological inhibition of IKK resulted in improved pathology and muscle function in mdx mice. Collectively, these results underscore the critical role of NF-kappaB in the progression of muscular dystrophy and suggest the IKK/NF-kappaB signaling pathway as a potential therapeutic target for DMD.

Nuclear cytokine-activated IKKα controls prostate cancer metastasis by repressing Maspin

Abstract: Experiments in a mouse prostate cancer model have identified a signalling pathway that stimulates the formation of metastases. The pathway is initiated when a protein ligand occupies a receptor known as RANK (receptor activator of nuclear factor κB), and is dependent on the activation and nuclear translocation of IKKα (IκB kinase α). Once in the nucleus, activated IKKα represses maspin gene transcription, whose product is well established as an inhibitor of cell migration and invasion in prostate and breast cancer. RANK may therefore be a general promoter of metastatic behaviour in prostate or mammary carcinoma cells. A previously unknown signalling pathway is shown to enhance the formation of metastases in a mouse model of prostate cancer. This pathway can be activated by RANK ligand that is expressed by inflammatory cells in the tumour and triggers activation of IKKα in the nucleus, where it directly represses the transcription of maspin, a known metastases suppressor. Inflammation enhances tumour promotion through NF-κB-dependent mechanisms1. NF-κB was also proposed to promote metastatogenesis through epithelial–mesenchymal transition2. Yet a mechanistic link between inflammation and metastasis is missing. We identified a role for IκB kinase α (IKKα), activated by receptor activator of NF-κB (RANK/TNFRSF11A), in mammary epithelial proliferation during pregnancy3. Owing to similarities between mammary and prostate epithelia, we examined IKKα involvement in prostate cancer and its progression. Here we show that a mutation that prevents IKKα activation slows down CaP growth and inhibits metastatogenesis in TRAMP mice, which express SV40 T antigen in the prostate epithelium4. Decreased metastasis correlated with elevated expression of the metastasis suppressor Maspin5, the ablation of which restored metastatic activity. IKKα activation by RANK ligand (RANKL/TNFSF11) inhibits Maspin expression in prostate epithelial cells, whereas repression of Maspin transcription requires nuclear translocation of active IKKα. The amount of active nuclear IKKα in mouse and human prostate cancer correlates with metastatic progression, reduced Maspin expression and infiltration of prostate tumours with RANKL-expressing inflammatory cells. We propose that tumour-infiltrating RANKL-expressing cells lead to nuclear IKKα activation and inhibition of Maspin transcription, thereby promoting the metastatic phenotype.

p63 induces key target genes required for epidermal morphogenesis

Abstract: Mice lacking p63, a single gene that encodes a group of transcription factors that either contain (TA) or lack (ΔN) a transactivation domain, fail to develop stratified epithelia as well as epithelial appendages and limbs. ΔNp63 isoforms are predominantly expressed during late embryonic and postnatal epidermal development, however, the function of these proteins remains elusive. Using an epidermal-specific inducible knockdown mouse model, we demonstrate that ΔNp63 proteins are essential for maintaining basement membrane integrity and terminal differentiation of keratinocytes. Furthermore, we have identified two ΔNp63α target genes that mediate these processes. We propose that ΔNp63α initially induces expression of the extracellular matrix component Fras1, which is required for maintaining the integrity of the epidermal–dermal interface at the basement membrane. Subsequently, induction of IκB kinase-α by ΔNp63α initiates epidermal terminal differentiation resulting in the formation of the spinous layer. Our data provide insights into the role of ΔNp63α in epidermal morphogenesis and homeostasis, and may contribute to our understanding of the pathogenic mechanisms underlying disorders caused by p63 mutations.

IκB kinase α kinase activity is required for self-renewal of ErbB2/Her2-transformed mammary tumor-initiating cells

Abstract: NF-κB is constitutively active in many solid tumors, including breast cancer. However, the role of NF-κB in breast carcinogenesis is unknown. IkkαAA/AA “knockin” mice in which activation of IκB kinase α (IKKα) is prevented by replacement of activation loop serines with alanines exhibit delayed mammary gland growth during pregnancy, because IKKα activity is required for cyclin D1 induction and proliferation of lobuloalveolar epithelial cells. Given the role of cyclin D1 in breast and mammary cancer, we examined involvement of IKKα in mammary carcinogenesis induced by oncogenes or a chemical carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA). The IkkαAA mutation retarded tumor development in response to either 7,12-dimethylbenzaanthracene or the MMTV-c-neu (ErbB2/Her2) transgene but had no effect on MMTV-v-Ha-ras-induced cancer, although both oncogenes rely on cyclin D1. Strikingly, primary IkkαAA/AA/MMTV-c-neu carcinoma cells exhibited diminished self-renewal capacity, resulting in the inability to establish secondary tumors. IkkαAA/AA/MMTV-c-neu carcinoma cells underwent premature senescence when cultured under conditions used for propagation of mammary gland stem cells. Thus, IKKα is not only a regulator of mammary epithelial proliferation, but is also an important contributor to ErbB2-induced oncogenesis, providing signals that maintain mammary tumor-initiating cells. IKKα may represent a novel and specific target for treatment of ErbB2-positive breast cancer.

NF-κB prevents β cell death and autoimmune diabetes in NOD mice

Abstract: Whereas NF-κB has potent antiapoptotic function in most cell types, it was reported that in pancreatic β cells it serves a proapoptotic function and may contribute to the pathogenesis of autoimmune type 1 diabetes. To investigate the role of β cell NF-κB in autoimmune diabetes, we produced transgenic mice expressing a nondegradable form of IκBα in pancreatic β cells (RIP-mIκBα mice). β cells of these mice were more susceptible to killing by TNF-α plus IFN-γ but more resistant to IL-1β plus IFN-γ than normal β cells. Similar results were obtained with β cells lacking IκB kinase β, a protein kinase required for NF-κB activation. Inhibition of β cell NF-κB accelerated the development of autoimmune diabetes in nonobese diabetic mice but had no effect on glucose tolerance or serum insulin in C57BL/6 mice, precluding a nonphysiological effect of transgene expression. Development of diabetes after transfer of diabetogenic CD4+ T cells was accelerated in RIP-mIκBα/nonobese diabetic mice and was abrogated by anti-TNF therapy. These results suggest that under conditions that resemble autoimmune type 1 diabetes, the dominant effect of NF-κB is prevention of TNF-induced apoptosis. This differs from the proapoptotic function of NF-κB in IL-1β-stimulated β cells.

From death receptor to reactive oxygen species and c‐Jun N‐terminal protein kinase: the receptor‐interacting protein 1 odyssey

Abstract: Death receptors (DRs) are more than simple killers: they control cell growth, proliferation, and survival, thereby playing a pivotal role in immune and inflammatory responses. Some of these phenomena might be explained by aberrant reactive oxygen species (ROS) production and metabolism, which can lead to oxidative stress. A key signaling molecule of DR-initiated intracellular pathways, receptor-interacting protein 1 (RIP1), orchestrates a complex control of multiple responses and may link DR-associated signaling complexes to ROS production by mitochondria. Yet, RIP1 is also an important regulator of endogenous anti-oxidants and ROS scavenging enzymes, because it is required for nuclear factor kappaB activation that results in expression of anti-apoptotic and anti-oxidant proteins. Alteration of RIP1 function may result in ROS accumulation and abnormal c-Jun N-terminal protein kinase activation, affecting inflammatory responses, innate immunity, stress responses, and cell survival. These molecular mechanisms may be involved in neoplastic, autoimmune, neurodegenerative, inflammatory, and metabolic diseases.

Kinase MEKK1 is required for CD40-dependent activation of the kinases Jnk and p38, germinal center formation, B cell proliferation and antibody production

Abstract: Mice lacking activity of the kinase MEKK1 ('Map3k1(deltaKD)' mice) have defective activation of the kinase Jnk and increased production of T helper type 2 cytokines after T cell receptor ligation. Here we show that Map3k1(deltaKD) mice had defective germinal center formation and diminished production of antibodies recognizing thymus-dependent antigens. Those defects were B cell intrinsic, as MEKK1 was necessary for CD40-mediated activation of the kinases Jnk and p38 and transcription factor c-Jun, as well as for expression of cyclin D2 and activation-induced deaminase. MEKK1 was recruited to CD40 and adaptor molecule TRAF2 after CD40 ligation, and Map3k1(deltaKD) B cells were hypoproliferative after CD40 stimulation. Our data emphasize that MEKK1 is an essential component of signaling cascades needed for thymus-dependent antigen-induced B cell proliferation and antibody production.

Regulation of late B cell differentiation by intrinsic IKKα-dependent signals

Abstract: NF-κB-inducing kinase (NIK)-mediated IKKα phosphorylation activates the alternative NF-κB pathway, which is characterized by nuclear translocation of p52:RelB heterodimers. This alternative pathway is initiated by a select few receptors, including LT-βR, BAFF-R, and CD40. Although NIK, IKKα, and p52 are all critical regulators of LT-βR signaling in stromal cells during humoral immune responses, lymphocytes require NIK, but not p52, for optimal Ig production. This disparity suggests that NIK possesses critical cell-type-specific functions that do not depend on NF-κB. Here we use mice bearing targeted mutations of the IKKα activation loop Ser176/180 (IKKαAA) to address the B cell-intrinsic functions of NIK–IKKα signaling in vivo. We find that IKKαAA B cells mount normal primary antibody responses but do not enter germinal centers. This defect likely derives from ineffective early T–B cell collaboration and leads to impaired generation of humoral memory and relatively short-lived, low-affinity antibody production. Our findings contrast with those obtained by using p52−/− B cells, which mount normal Ig responses, and alymphoplasia (NIK mutant) B cells, which produce very little primary Ig. Thus, the NIK–IKKα–p52 axis is not as linear and exclusive as previous studies suggest, and IKKα possesses critical NF-κB-independent functions in B cells.

Differential Regulation of Hepatic Transporters in the Absence of Tumor Necrosis Factor-α, Interleukin-1β, Interleukin-6, and Nuclear Factor-κB in Two Models of Cholestasis

Abstract: Hepatic transporters are responsible for uptake and efflux of bile acids and xenobiotics as an essential aspect of liver function. When normal vectorial transport of bile acids by the apical uptake and canalicular excretion transporters is disrupted, cholestasis ensues, leading to accumulation of toxic bile constituents and considerable hepatocellular damage. The purpose of this study was to assess the role of cytokines and nuclear factor-kappaB (NF-kappaB) in the transcriptional regulation of transporters in two models of cholestasis, lipopolysaccharide (LPS) administration and bile duct ligation (BDL). In wild-type (WT) and knockout mouse strains lacking tumor necrosis factor (TNF) receptor-1, interleukin (IL)-1 receptor I, IL-6, or inhibitor of kappaB(IkappaB) kinase beta, transporter mRNA levels in liver were determined using branched DNA signal amplification 16 h after LPS administration or 3 days after BDL. In WT mice, LPS administration tended to decrease mRNA levels of organic anion-transporting polypeptide (Oatp) 2, Na(+)-taurocholate cotransporting polypeptide (Ntcp), Oatp1, Oatp4, bile salt excretory protein (Bsep), multidrug resistance-associated protein (Mrp) 2, and Mrp6 compared with saline treatment, whereas it increased Mrp1, 3, and 5 levels. Similar changes were observed in each knockout strain after LPS administration. Conversely, BDL decreased only Oatp1 expression in WT mice, meanwhile increasing expression of Mrp1, 3, and 5 and Oatp2 expression in both WT and knockout strains. Because the transcriptional effects of BDL- and LPS-induced cholestasis reflect dissimilarity in hepatic transporter regulation, we conclude that these disparities are not due to the individual activity of TNF-alpha, IL-1, IL-6, or NF-kappaB but to the differences in the mechanism of cholestasis.

Inhibitor κB Kinase β Binding by Inhibitor κB Kinase γ

Abstract: Activation of a large multisubunit protein kinase, called the inhibitor κB kinase (IKK) complex, is central to the induction of the family of transcription factors nuclear factor κB. IKK is comprised of two catalytic subunits, IKKα and IKKβ, and a regulatory IKKγ subunit. It is known that the catalytic IKKβ and regulatory IKKγ subunits associate through interactions mediated by the N-terminal region of IKKγ and an 11-mer peptide located near the C-terminus of IKKβ. In this study, we have defined the minimal IKKγ segment that binds IKKβ and determined the binding affinity of the IKKβ/IKKγ complex. We identified that the N-terminal segment spanning residues 40−130 of IKKγ binds the IKKβ C-terminal domain (residues 665−756) with Kd ≈ 25 nM. Several smaller N-terminal IKKγ deletion mutants within the N-terminal 130 residues, although in some cases retained IKKβ binding activity, showed a tendency to aggregate and formed covalently linked complexes. However, expansion of the C-terminus of these fragments to re...

Iκb-kinase/nuclear factor-κb signaling prevents thermal injury–induced gut damage by inhibiting c-jun Nh2-terminal kinase activation*

Abstract: Objective The molecular mechanism of major burn-induced gut damage is not clear. This study is to determine whether IkappaB-kinase (IKK)/nuclear factor-kappaB signaling in intestinal mucosa maintains gut function through the regulation of the c-Jun NH2-terminal kinase (JNK) and p38 phosphorylation. Design Prospective, experimental study. Setting Research laboratory at a university hospital. Subjects Thermal injury models in mice. Interventions Conditional intestinal epithelial cell IKKbeta knockout (Vil-Cre/Ikkbeta(F/Delta) mice and control (Ikkbeta(F/Delta) mice were subjected to 30% total body surface area third-degree burn. JNK inhibitor (SP600125) or p38 inhibitor (SB203580) was given to mice immediately after burn injury. Measurements and main results Thermal injury induced a significant increase of intestinal permeability, nuclear factor-kappaB DNA-binding activity, phosphorylated JNK, phosphorylated p38, and caspase 3 expression of intestinal mucosa in Vil-Cre/Ikkbeta(F/Delta) mice compared with those of Ikkbeta(F/Delta) mice. BCL-xL and cellular FLICE inhibitory protein, but not GADD45beta (growth arrest and DNA damage-inducing protein beta), cellular inhibitor of apoptosis 1, Bfl-1, or TRAIL, messenger RNA expression was significantly decreased in Vil-Cre/Ikkbeta(F/Delta) mice compared with that of Ikkbeta(F/Delta) mice. SP600125 decreased intestinal permeability and increased phosphorylated p38 and tumor necrosis factor receptor-associated factor 2 expression of intestinal mucosa in Vil-Cre/Ikkbeta(F/Delta) mice. SB203580 treatment enhanced thermal injury-induced gut damage in Vil-Cre/Ikkbeta(F/Delta) mice. Conclusions Thermal injury induces nuclear factor-kappaB activation of intestinal mucosa and IKK protects intestinal mucosa from thermal injury-induced gut damage. IKK blocks caspase 3 expression by up-regulating BCL-xL and cellular FLICE inhibitory protein expression. IKK inhibits JNK and p38 but not p44/42 phosphorylation of intestinal mucosa. JNK inhibition increases p38 and tumor necrosis factor receptor-associated factor 2 expression and decreases thermal injury-induced gut damage. Taken together with the enhanced thermal injury-induced gut damage by p38 inhibition, we conclude that IKK maintains gut function by inhibiting JNK phosphorylation, which suppresses p38 phosphorylation and induces gut damage.

Control of Osteoclast Activity and Bone Loss by IKK Subunits: New Targets for Therapy

Abstract: Transcription factor NF-kappaB has been well recognized as a pivotal player in osteclastogenesis and inflammation-induced bone loss. Here, we discuss our recent results obtained using a genetic approach in mice that indicate the importance of IKKbeta, and not IKKalpha, as a transducer of signals from receptor activator of NF-kappaB (RANK) to NF-kappaB. Ablation of IKKbeta results in lack of osteoclastogenesis and unresponsiveness of IKKbeta-deficient mice to inflammation-induced bone loss. In the need of a more effective therapy for the treatment of inflammatory diseases causing bone resorption, specific inhibition of IKKbeta represents a logical alternative strategy to the current therapies.

Rsk Tolls the bell for endocytosis in DCs.

Abstract: The mitogen-activated protein kinases Erk and p38 transduce Toll-like receptor signals that lead to antigen capture by dendritic cells. New work identifies 'downstream' effector kinases essential for these responses and traces a pathway of mitogen-activated protein kinase signaling apparently unique to dendritic cells.

Compositions and Methods for Activating Toll-like Receptor 4

Abstract: Methods for activating Toll-like receptor 4 via cholesterol-dependent cytolysins isolated from a Gram-positive bacteria are provided. In addition compositions containing an isolated cholesterol-dependent cytolysin or a fragment thereof or a mimetic of the cytolysin or fragment thereof and methods for use of such composition in inhibiting binding and/or interaction of Toll-like receptor 4 with endotoxin are provided. Methods for identifying modulators of Toll-like receptor 4 activation by a cholesterol-dependent cytolysin and use of such modulators in treatment of septicemia and/or septic shock are also provided.

Gamma subunit of cytokine responsive lkB-alpha kinase complex

Abstract: The present invention provides a novel essential regulatory subunit of the IκB kinase (IKK) complex, IKK-γ. The isolated IKK-γ subunit of the invention has substantially the same amino acid sequence as SEQ ID NO: 2 shown in FIG. 2.

Method for detecting the presence of prostate cancer

Abstract: The present invention relates to compositions and methods for cancer diagnosis, treatment and drug screening. In particular, the present invention provides compositions and methods for targeting the nuclear translocation of IkB kinase-α (IKKα) and the IKKα-mediated suppression of Maspin expression observed in metastatic prostate cancer cells.