Showing papers by "Michael Karin published in 2009"

Regulation and Function of NF-κB Transcription Factors in the Immune System

Abstract: The mammalian Rel/NF-κB family of transcription factors, including RelA, c-Rel, RelB, NF-κB1 (p50 and its precursor p105), and NF-κB2 (p52 and its precursor p100), plays a central role in the immune system by regulating several processes ranging from the development and survival of lymphocytes and lymphoid organs to the control of immune responses and malignant transformation. The five members of the NF-κB family are normally kept inactive in the cytoplasm by interaction with inhibitors called IκBs or the unprocessed forms of NF-κB1 and NF-κB2. A wide variety of signals emanating from antigen receptors, pattern-recognition receptors, receptors for the members of TNF and IL-1 cytokine families, and others induce differential activation of NF-κB heterodimers. Although work over the past two decades has shed significant light on the regulation of NF-κB transcription factors and their functions, much progress has been made in the past two years revealing new insights into the regulation and functions of NF-κB...

Carcinoma-produced Factors Activate Myeloid Cells Through TLR2 to Stimulate Metastasis

Abstract: Metastatic progression depends on genetic alterations intrinsic to cancer cells as well as the inflammatory microenvironment of advanced tumours. To understand how cancer cells affect the inflammatory microenvironment, we conducted a biochemical screen for macrophage-activating factors secreted by metastatic carcinomas. Here we show that, among the cell lines screened, Lewis lung carcinoma (LLC) were the most potent macrophage activators leading to production of interleukin-6 (IL-6) and tumour-necrosis factor-alpha (TNF-alpha) through activation of the Toll-like receptor (TLR) family members TLR2 and TLR6. Both TNF-alpha and TLR2 were found to be required for LLC metastasis. Biochemical purification of LLC-conditioned medium (LCM) led to identification of the extracellular matrix proteoglycan versican, which is upregulated in many human tumours including lung cancer, as a macrophage activator that acts through TLR2 and its co-receptors TLR6 and CD14. By activating TLR2:TLR6 complexes and inducing TNF-alpha secretion by myeloid cells, versican strongly enhances LLC metastatic growth. These results explain how advanced cancer cells usurp components of the host innate immune system, including bone-marrow-derived myeloid progenitors, to generate an inflammatory microenvironment hospitable for metastatic growth.

Is NF-κB a good target for cancer therapy? Hopes and pitfalls

Abstract: The nuclear factor κB (NF-κB) signalling pathway has been implicated in cancer development and progression, as well as in resistance to chemotherapy and radiation therapy. In this Perspective, Baud and Karin explore the therapeutic potential of targeting NF-κB in cancer, and discuss the challenges posed by this approach. Nuclear factor κB (NF-κB) transcription factors have a key role in many physiological processes such as innate and adaptive immune responses, cell proliferation, cell death, and inflammation. It has become clear that aberrant regulation of NF-κB and the signalling pathways that control its activity are involved in cancer development and progression, as well as in resistance to chemotherapy and radiotherapy. This article discusses recent evidence from cancer genetics and cancer genome studies that support the involvement of NF-κB in human cancer, particularly in multiple myeloma. The therapeutic potential and benefit of targeting NF-κB in cancer, and the possible complications and pitfalls of such an approach, are explored.

NF-kappaB as a critical link between inflammation and cancer.

Abstract: NF-kappaB transcription factors have been suspected to be involved in cancer development since their discovery because of their kinship with the v-Rel oncogene product. Subsequent work led to identification of oncogenic mutations that result in NF-kappaB activation in lymphoid malignancies, but most of these mutations affect upstream components of NF-kappaB signaling pathways, rather than NF-kappaB family members themselves. NF-kappaB activation has also been observed in many solid tumors, but so far no oncogenic mutations responsible for NF-kappaB activation in carcinomas have been identified. In such cancers, NF-kappaB activation is a result of underlying inflammation or the consequence of formation of an inflammatory microenvironment during malignant progression. Most importantly, through its ability to up-regulate the expression of tumor promoting cytokines, such as IL-6 or TNF-alpha, and survival genes, such as Bcl-X(L), NF-kappaB provides a critical link between inflammation and cancer.

Caspase 1–independent activation of interleukin-1β in neutrophil-predominant inflammation

Abstract: Objective Interleukin-1β (IL-1β) is a key cytokine linked to the pathogenesis of acute arthritis. Caspase 1, neutrophil elastase, and chymase all process proIL-1β to its biologically active form. This study was undertaken to examine the potential contributions of each of these proteases in experimental models of inflammatory arthritis. Methods Caspase 1–deficient (Casp1−/−) and wild-type (WT) mice were tested for their response to arthritogenic K/BxN serum transfer for induction of arthritis or injection of monosodium urate monohydrate (MSU) crystals for induction of peritonitis. All mice were prophylactically treated with inhibitors of neutrophil elastase or chymase. Arthritic paws were tested for the presence of IL-1β protein by enzyme-linked immunosorbent assay and Western blotting. Neutrophils and mast cells from WT and mutant mice were tested for their ability to secrete IL-1β after in vitro stimulation, in the presence of protease inhibitors. Results Casp1−/− and WT mice developed paw swelling to the same extent in the K/BxN serum transfer–induced arthritis model. MSU crystal injection into Casp1−/− mice also resulted in neutrophil influx and production of measurable peritoneal IL-1β protein. Both of these responses were attenuated with neutrophil elastase inhibitors. K/BxN serum transfer–induced arthritis was also reduced by treatment with a chymase inhibitor. Casp1−/− neutrophils and mast cells, when exposed to MSU crystals, secreted similar amounts of IL-1β protein upon in vitro stimulation with lipopolysaccharide, albeit at lower levels than that secreted by WT cells. Elastase and chymase inhibitors reduced the amount of IL-1β released by these cells. Conclusion The production of IL-1β by neutrophils and mast cells is not exclusively dependent on caspase 1, and other proteases can compensate for the loss of caspase 1 in vivo. These pathways might therefore compromise the caspase 1–targeted therapies in neutrophil-predominant arthritis.

Nuclear cytokine-activated IKKα controls prostate cancer metastasis by repressing Maspin (Nature (2007) 446, (690-694))

Abstract: This corrects the article DOI: 10.1038/nature05656

NOD2 contributes to cutaneous defense against Staphylococcus aureus through α-toxin-dependent innate immune activation

Abstract: Staphylococcus aureus is a major cause of community-acquired and nosocomial infections including the life-threatening conditions endocarditis, necrotizing pneumonia, necrotizing fasciitis, and septicemia. Toll-like receptor (TLR)-2, a membrane-bound microbial sensor, detects staphylococcal components, but macrophages lacking TLR2 or both TLR2 and TLR4 remain S. aureus responsive, suggesting that an alternative microbial recognition receptor might be involved. The cytoplasmic sensor nucleotide-binding oligomerization domain containing (NOD) 2/caspase recruitment domain (CARD) 15 detects muramyl dipeptide from bacterial peptidoglycans and mediates cytokine responses to S. aureus in vitro, but the physiological significance of these observations is not well defined. Here we show that NOD2-deficient mice exhibit a delayed but ultimately exacerbated ulcerative response and impaired bacterial clearance after s.c. infection with S. aureus. NOD2-dependent recognition of S. aureus and muramyl dipeptide is facilitated by α-toxin (α-hemolysin), a pore-forming toxin and virulence factor of the pathogen. The action of NOD2 is dependent on IL-1β-amplified production of IL-6, which promotes rapid bacterial killing by neutrophils. These results significantly broaden the physiological importance of NOD2 in innate immunity from the recognition of bacteria that primarily enter the cytoplasm to the detection of bacteria that typically reside extracellularly and demonstrate that this microbial sensor contributes to the discrimination between commensal bacteria and bacterial pathogens that elaborate pore-forming toxins.

TNFR signaling: ubiquitin‐conjugated TRAFfic signals control stop‐and‐go for MAPK signaling complexes

Abstract: Nearly two decades after the initial cloning and identification of the founding father of the tumor necrosis factor receptor (TNFR) family, much has been learned about the mechanisms by which these receptors signal to critical transcription factors and other targets that regulate gene expression and cellular physiology. Mitogen-activated protein kinases (MAPKs) and inhibitor of nuclear factor (NF)-kappaB (I kappaB) kinases (IKKs) were identified early on as the upstream kinases responsible for activation of activator-protein 1 (AP-1) and NF-kappaB, respectively, and later on for their ability to control life-or-death decisions in TNF-stimulated cells. Both of these critical pathways are regulated at the level of MAPK kinase kinases (MAP3Ks), after which point they diverge. Recent work, however, illustrates that protein ubiquitination cascades play a critical initiating role in TNFR signaling and account for spatial and temporal separation of IKK and MAPK signaling cascades and thereby determine biological specificity and outcome. Cellular inhibitors of apoptosis (cIAPs) 1 and 2 are ubiquitin (Ub) ligases (E3s) that mediate canonical Lys48-linked ubiquitination of TNFR-associated factor 3 (TRAF3), marking it for subsequent degradation by the proteasome. TRAF3 degradation releases the brake on TRAF2/6:MAP3K signaling complexes responsible for MAPK activation, leading to their translocation from the cytoplasmic segment of the receptor to the cytosol where they initiate MAPK phosphorylation and activation. By contrast, IKK activation proceeds considerably faster than MAPK activation, takes place at the receptor, and is independent of cIAP1/2 activity and TRAF3 degradation. This arrangement may be important for ensuring the proper delivery of NF-kappaB-dependent survival signals and conversion of JNK-promoted death signals to proliferative ones.

The chemokine CXCL16 and its receptor, CXCR6, as markers and promoters of inflammation-associated cancers.

Abstract: Clinical observations and mouse models have suggested that inflammation can be pro-tumorigenic. Since chemokines are critical in leukocyte trafficking, we hypothesized that chemokines play essential roles in inflammation-associated cancers. Screening for 37 chemokines in prostate cancer cell lines and xenografts revealed CXCL16, the ligand for the receptor CXCR6, as the most consistently expressed chemokine. Immunohistochemistry and/or immunofluorescence and confocal imaging of 121 human prostate specimens showed that CXCL16 and CXCR6 were co-expressed, both on prostate cancer cells and adjacent T cells. Expression levels of CXCL16 and CXCR6 on cancer cells correlated with poor prognostic features including high-stage and high-grade, and expression also correlated with post-inflammatory changes in the cancer stroma as revealed by loss of alpha-smooth muscle actin. Moreover, CXCL16 enhanced the growth of CXCR6-expressing cancer and primary CD4 T cells. We studied expression of CXCL16 in an additional 461 specimens covering 12 tumor types, and found that CXCL16 was expressed in multiple human cancers associated with inflammation. Our study is the first to describe the expression of CXCL16/CXCR6 on both cancer cells and adjacent T cells in humans, and to demonstrate correlations between CXCL16 and CXCR6 vs. poor both prognostic features and reactive changes in cancer stoma. Taken together, our data suggest that CXCL16 and CXCR6 may mark cancers arising in an inflammatory milieu and mediate pro-tumorigenic effects of inflammation through direct effects on cancer cell growth and by inducing the migration and proliferation of tumor-associated leukocytes.

Genetic and pharmacological inhibition of JNK ameliorates hypoxia-induced retinopathy through interference with VEGF expression

Abstract: Many ocular pathologies, including retinopathy of prematurity (ROP), diabetic retinopathy, and age-related macular degeneration, result in vision loss because of aberrant neoangiogenesis. A common feature of these conditions is the presence of hypoxic areas and overexpression of the proangiogenic vascular endothelial growth factor (VEGF). The prevailing current treatment, laser ablation of the retina, is destructive and only partially effective. Preventive and less destructive therapies are much more desirable. Here, we show that mice lacking c-Jun N-terminal kinase 1 (JNK1) exhibit reduced pathological angiogenesis and lower levels of retinal VEGF production in a murine model of ROP. We found that hypoxia induces JNK activation and regulates VEGF expression by enhancing the binding of phospho-c-Jun to the VEGF promoter. Intravitreal injection of a specific JNK inhibitor decreases retinal VEGF expression and reduces pathological retinal neovascularization without obvious side effects. These results strongly suggest that JNK1 plays a key role in retinal neoangiogenesis and that it represents a new pharmacological target for treatment of diseases where excessive neoangiogenesis is the underlying pathology.

NF-kB as a Critical Link Between Inflammation and Cancer

Abstract: NF-kB transcription factors have been suspected to be involved in cancer development since their discovery because of their kinship with the v-Rel oncogene product. Subsequent work led to identification of oncogenic mutations that result in NF-kB activation in lymphoid malignancies, but most of these mutations affect upstream components of NF-kB signaling pathways, rather than NF-kB family members themselves. NF-kB activation has also been observed in many solid tumors, but so far no oncogenic mutations responsible for NF-kB activation in carcinomas have been identified. In such cancers, NF-kB activation is a result of underlying inflammation or the consequence of formation of an inflammatory microenvironment during malignant progression. Most importantly, through its ability to up-regulate the expression of tumor promoting cytokines, such as IL-6 or TNF-a, and survival genes, such as Bcl-XL, NF-kB provides a critical link between inflammation and cancer.

Conditional Deletion of IkappaB-Kinase-beta Accelerates Helicobacter-Dependent Gastric Apoptosis, Proliferation, and Preneoplasia

Abstract: BACKGROUND & AIMS The nuclear factor kappaB (NF-kappaB)/IkappaB-kinase-beta (IKKbeta) pathway has been shown to represent a key link between inflammation and cancer, inducing pro-inflammatory cytokines in myeloid cells and anti-apoptotic pathways in epithelial cells. However, the role of NF-kappaB pathway in gastric carcinogenesis and injury has not been well-defined. We derived mice with a conditional knockout of IKKbeta in gastric epithelial cells (GECs) and myeloid cells, and examined responses to ionizing radiation (IR) and Helicobacter felis infection. METHODS Ikkbeta(Deltastom) mice were generated by crossing Foxa3-Cre mice to Ikkbeta(F/F) mice. Cellular stress was induced with IR and H felis in Ikkbeta(Deltastom), Ikkbeta(F/F), and cis-NF-kappaB-enhanced green fluorescent protein (GFP) reporter mice. Gastric histopathology, apoptosis, proliferation, necrosis, reactive oxygen species, and expression of cytokines, chemokines, and anti-apoptotic genes were assessed. The role of myeloid IKKbeta in these models was studied by crosses with LysM-Cre mice. RESULTS NF-kappaB activity was upregulated in myeloid cells with acute H felis infection, but in GECs by IR or long-term H felis infection during progression to dysplasia. Deletion of IKKbeta in GECs led to increased apoptosis, reactive oxygen species, and cellular necrosis, and resulted in up-regulation of interleukin-1alpha and down-regulation of anti-apoptotic genes. Loss of IKKbeta in GECs resulted in worse inflammation and more rapid progression to gastric preneoplasia, while loss of IKKbeta in myeloid cells inhibited development of gastric atrophy. CONCLUSIONS The loss of IKKbeta/NF-kappaB signaling in GECs results in increased apoptosis and necrosis in response to cellular stress, and accelerated development of dysplasia by Helicobacter infection.

Neuronal IκB Kinase β Protects Mice from Autoimmune Encephalomyelitis by Mediating Neuroprotective and Immunosuppressive Effects in the Central Nervous System

Abstract: Some aspects of CNS-directed autoimmunity in multiple sclerosis are modeled in mice by immunization with myelin Ags where tissue damage is driven by myelin-reactive Th1 and Th17 effector lymphocytes. Whether the CNS plays an active role in controlling such autoimmune diseases is unknown. We used mice in which IkappaB kinase beta was deleted from Ca(2+)/calmodulin-dependent kinase IIalpha-expressing neurons (nIKKbetaKO) to investigate the contribution of neuronal NF-kappaB to the development of myelin oligodendrocyte glycoprotein 35-55-induced experimental autoimmune encephalomyelitis. We show that nIKKbetaKO mice developed a severe, nonresolving disease with increased axon loss compared with controls and this was associated with significantly reduced CNS production of neuroprotective factors (vascular endothelial growth factor, CSF1-R, and FLIP) and increased production of proinflammatory cytokines (IL-6, TNF, IL-12, IL-17, and CD30L) and chemokines. The isolation of CNS-infiltrating monocytes revealed greater numbers of CD4(+) T cells, reduced numbers of NK1.1(+) cells, and a selective accumulation of Th1 cells in nIKKbetaKO CNS from early in the disease. Our results show that neurons play an important role in determining the quality and outcome of CNS immune responses, specifically that neuronal IkappaB kinase beta is required for neuroprotection, suppression of inflammation, limitation of Th1 lymphocyte accumulation, and enhancement of NK cell recruitment in experimental autoimmune encephalomyelitis-affected CNS and stress the importance of neuroprotective strategies for the treatment of multiple sclerosis.

MEKK1 binds HECT E3 ligase itch by its amino-terminal RING motif to regulate Th2 cytokine gene expression

Abstract: MEKK1-dependent signaling regulates HECT E3 ligase Itch, resulting in elevated catalytic activity. After TCR costimulation, MEKK1 predominantly induces JNK1 activation, whereas the related kinase MEKK2 regulates ERK5 activation. MEKK1 becomes phosphorylated on multiple sites and polyubiquitinated following TCR costimulation. E3 ligase Itch is recruited to activated MEKK1, but not MEKK2, and this novel scaffolding interaction is dependent on MEKK1 Thr1381 phosphorylation within the kinase domain and an intact MEKK1 RING finger motif. MEKK1 phosphorylation on Thr1381 is observed during Th2 differentiation, but not under Th1 differentiation. Both Itch and the MEKK1 kinase domain are important for Il4 and Il6 cytokine gene expression under Th2 conditions.