NF-κB inducing kinase: a key regulator in the immune system and in cancer

A molting-inhibiting hormone-like protein from Pacific white shrimp Litopenaeus vannamei is involved in immune responses

The molting-inhibiting hormones (MIHs) from the crustacean hyperglycemic hormone (CHH) family are a group of neuropeptides that are implicated in regulation of molting and reproduction in crustaceans. In this study, a novel protein containing a typical crustacean neuropeptide domain was identified from Litopenaeus vannamei. The protein showed high homology with other shrimp MIHs and was then designated as a MIH-like protein (MIHL). Among the detected tissues, the heart expressed the highest level of MIHL. The expression of MIHL could be significantly up-regulated after infection with white spot syndrome virus (WSSV), gram-negative bacterium Vibro parahaemolyticus and gram-positive bacterium Staphylococcus aureus, indicating that MIHL could be involved in immune responses. The promoter of MIHL was predicted to contain two NF-κB binding sites and could be regulated by the NF-κB family protein Relish but not Dorsal, suggesting that MIHL could be an effector gene of the IMD/Relish pathway. Silencing of MIHL in vivo by RNAi strategy significantly down-regulated the expression of many immune effector genes and increased the mortalities of shrimp infected by V. parahaemolyticus and WSSV and their copy numbers in tissues. These confirmed that MIHL could play a role in antiviral and antibacterial immune responses in shrimp.

Zinc finger protein 91 (ZFP91) activates HIF-1α via NF-κB/p65 to promote proliferation and tumorigenesis of colon cancer

Zinc finger protein 91 (ZFP91) has been reported to be involved in various biological processes. However, the clinical significance and biological role of ZFP91 in colon cancer remains unknown. Here, we show that ZFP91 expression is upregulated in patients with colon cancer. We found that ZFP91 upregulated HIF-1α at the levels of promoter and protein in colon cancer cells. Using chromatin immunoprecipitation, electrophoretic mobility shift assay and luciferase reporter gene assay, we found that NF-κB/p65 is required for the binding of ZFP91 to the HIF-1α promoter at -197/-188 base pairs and for the transcriptional activation of HIF-1α gene mediated by ZFP91. Flow cytometry, 5-ethynyl-2'-deoxyuridine (EdU) incorporation and tumor xenograft assay demonstrated that ZFP91 enhanced cell proliferation of colon cancer through upregulating HIF-1α in vitro and in vivo. Furthermore, ZFP91 is positively associated with HIF-1α in human colon cancer. Thus, we concluded that ZFP91 activates transcriptional coregulatory protein HIF-1α through transcription factor NF-κB/p65 in the promotion of proliferation and tumorigenesis in colon cancer cell. ZFP91 may serve as a driver gene to activate HIF-1α transcription in the development of cancer.

Pharmacological Potential and Synthetic Approaches of Imidazo[4,5-b]pyridine and Imidazo[4,5-c]pyridine Derivatives

The structural resemblance between the fused imidazopyridine heterocyclic ring system and purines has prompted biological investigations to assess their potential therapeutic significance. They are known to play a crucial role in numerous disease conditions. The discovery of their first bioactivity as GABA_A receptor positive allosteric modulators divulged their medicinal potential. Proton pump inhibitors, aromatase inhibitors, and NSAIDs were also found in this chemical group. Imidazopyridines have the ability to influence many cellular pathways necessary for the proper functioning of cancerous cells, pathogens, components of the immune system, enzymes involved in carbohydrate metabolism, etc. The collective results of biochemical and biophysical properties foregrounded their medicinal significance in central nervous system, digestive system, cancer, inflammation, etc. In recent years, new preparative methods for the synthesis of imidazopyridines using various catalysts have been described. The present manuscript to the best of our knowledge is the complete compilation on the synthesis and medicinal aspects of imidazo[4,5-b]pyridines and imidazo[4,5-c]pyridines reported from the year 2000 to date, including structure–activity relationships.

NIK/MAP3K14 Regulates Mitochondrial Dynamics and Trafficking to Promote Cell Invasion

Although the role of NF-κB-inducing kinase (NIK) in immunity is well established, its relevance in cancer is just emerging. Here we describe novel functions for NIK in regulating mitochondrial dynamics and motility to promote cell invasion. We show that NIK is localized to mitochondria in cancer cell lines, ex vivo tumor tissue, and mouse embryonic fibroblasts (MEFs). NIK promotes mitochondrial fission, velocity, and directional migration, resulting in subcellular distribution of mitochondria to the periphery of migrating cells. Moreover, NIK is required for recruitment of Drp1 to mitochondria, forms a complex with Drp1, and regulates Drp1 phosphorylation at Ser-616 and dephosphorylation at Ser-637. Consistent with a role for NIK in regulating mitochondrial dynamics, we demonstrate that Drp1 is required for NIK-dependent, cytokine-induced invasion. Importantly, using MEFs, we demonstrate that the established downstream mediators of NIK signaling, IκB kinase α/β (IKKα/β) and NF-κB, are not required for NIK to regulate cell invasion, Drp1 mitochondrial localization, or mitochondrial fission. Our results establish a new paradigm for IKK-independent NIK signaling and significantly expand the current dogma that NIK is predominantly cytosolic and exclusively regulates NF-κB activity. Overall, these findings highlight the importance of NIK in tumor pathogenesis and invite new therapeutic strategies that attenuate mitochondrial dysfunction through inhibition of NIK and Drp1.

NF-kappaΒ-inducing kinase regulates stem cell phenotype in breast cancer

Breast cancer stem cells (BCSCs) overexpress components of the Nuclear factor-kappa B (NF-κB) signaling cascade and consequently display high NF-κB activity levels. Breast cancer cell lines with high proportion of CSCs exhibit high NF-κB-inducing kinase (NIK) expression. The role of NIK in the phenotype of cancer stem cell regulation is poorly understood. Expression of NIK was analyzed by quantitative RT-PCR in BCSCs. NIK levels were manipulated through transfection of specific shRNAs or an expression vector. The effect of NIK in the cancer stem cell properties was assessed by mammosphere formation, mice xenografts and stem markers expression. BCSCs expressed higher levels of NIK and its inhibition through small hairpin (shRNA), reduced the expression of CSC markers and impaired clonogenicity and tumorigenesis. Genome-wide expression analyses suggested that NIK acts on ERK1/2 pathway to exert its activity. In addition, forced expression of NIK increased the BCSC population and enhanced breast cancer cell tumorigenicity. The in vivo relevance of these results is further supported by a tissue microarray of breast cancer samples in which we observed correlated expression of Aldehyde dehydrogenase (ALDH) and NIK protein. Our results support the essential involvement of NIK in BCSC phenotypic regulation via ERK1/2 and NF-κB.

Bovine lactoferrin free of lipopolysaccharide can induce a proinflammatory response of macrophages

Background

Lactoferrin (LF) is an 80 kDa glycoprotein which is known for its effects against bacteria, viruses and other pathogens. It also has a high potential in nutrition therapy and welfare of people and a variety of animals, including piglets. The ability to bind lipopolysaccharide (LPS) is one of the described anti-inflammatory mechanisms of LF. Previous studies suggested that cells can be stimulated even by LPS-free LF. Therefore, the aim of our study was to bring additional information about this possibility. Porcine monocyte derived macrophages (MDMF) and human embryonic kidney (HEK) cells were stimulated with unpurified LF in complex with LPS and with purified LF without bound LPS.

Results

Both cell types were stimulated with unpurified as well as purified LF. On the other hand, neither HEK0 cells not expressing any TLR nor HEK4a cells transfected with TLR4 produced any pro-inflammatory cytokine transcripts after stimulation with purified LF. This suggests that purified LF without LPS stimulates cells via another receptor than TLR4. An alternative, TLR4-independent, pathway was further confirmed by analyses of the NF-kappa-B-inducing kinase (NIK) activation. Western blot analyses showed NIK which activates different NFκB subunits compared to LF-LPS signaling via TLR4. Though, this confirmed an alternative pathway which is used by the purified LF free of LPS. This stimulation of MDMF led to low, but significant amounts of pro-inflammatory cytokines, which can be considered as a positive stimulation of the immune system.

Conclusion

Our results suggest that LF’s ability is not only to bind LPS, but LF itself may be a stimulant of pro-inflammatory pathways.

OTUD7B and NIK expression in non-small cell lung cancer: Association with clinicopathological features and prognostic implications

PURPOSE

To investigate the correlation among OTUD7B and NIK expression and the clinicopathological characteristics in NSCLC patients.

METHODS

One hundred and twenty patients were involved in this study. We detected OTUD7B and NIK expression by immunohistochemistry and analyzed their correlation with clinicopathological data.

RESULTS

The expression of OTUD7B and NIK were negatively correlated in NSCLC tumor samples (rs=-0.421, P<0.001). The higher expression of OTUD7B was associated with smaller tumor size(P=0.018), less lymph node metastasis (P=0.012) and earlier TNM stage(P=0.039), while the higher expression of NIK was only related to more lymph node metastasis(P=0.031) and later TNM stage(P=0.011). MMP-9 was negatively correlated with OTUD7B and positively correlated with NIK. In addition, the high expression of OTUD7B was associated with good prognosis of NSCLC patients (log-rank=6.714, P=0.0096), and a high OTUD7B/low NIK index can predict an even better prognosis (log-rank=11.794, P=0.0006). Moreover, the multivariate Cox regression analysis showed that OTUD7B rather than NIK is an independent marker of overall survival in NSCLC patients(HR=1.602, 95% CI 1.009-2.544, P=0.046).

CONCLUSIONS

OTUD7B and NIK may play important roles in the development of lung cancer. The combination of OTUD7B and NIK expression may be a good index for predicting the prognosis of NSCLC.

Non-canonical NFκB mutations reinforce pro-survival TNF response in multiple myeloma through an autoregulatory RelB:p50 NFκB pathway

Environmental drug resistance constitutes a serious impediment for therapeutic intervention in multiple myeloma. Tumor-promoting cytokines, such as tumor necrosis factor (TNF), induce nuclear factor-κB (NFκB)- driven expression of pro-survival factors, which confer resistance in myeloma cells to apoptotic insults from TNF-related apoptosis-inducing ligand (TRAIL) and other chemotherapeutic drugs. It is thought that RelA:p50 dimer, activated from IκBα-inhibited complex in response to TNF-induced canonical NFκB signal, mediates the pro-survival NFκB function in cancerous cells. Myeloma cells additionally acquire gain-of-function mutations in the non-canonical NFκB module, which induces partial proteolysis of p100 into p52 to promote RelB:p52/NFκB activation from p100-inhibited complex during immune cell differentiation. However, role of non-canonical NFκB signaling in the drug resistance in multiple myeloma remains unclear. Here we report that myeloma-associated non-canonical aberrations reinforce pro-survival TNF signaling in producing a protracted TRAIL-refractory state. These mutations did not act through a typical p52 NFκB complex, but completely degraded p100 to reposition RelB under IκBα control, whose degradation during TNF signaling induced an early RelB:p50 containing NFκB activity. More so, autoregulatory RelB synthesis prolonged this TNF-induced RelB:p50 activity in myeloma cells harboring non-canonical mutations. Intriguingly, TNF-activated RelB:p50 dimer was both necessary and sufficient, and RelA was not required, for NFκB-dependent pro-survival gene expressions and suppression of apoptosis. Indeed, high RelB mRNA expressions in myeloma patients correlated with the augmented level of pro-survival factors and resistance to therapeutic intervention. In sum, we provide evidence that cancer-associated mutations perpetuate TNF-induced pro-survival NFκB activity through autoregulatory RelB control and thereby exacerbate environmental drug resistance in multiple myeloma.

Mitogen-Activated Protein Kinase 14 Promotes AKI

An improved understanding of pathogenic pathways in AKI may identify novel therapeutic approaches. Previously, we conducted unbiased liquid chromatography-tandem mass spectrometry-based protein expression profiling of the renal proteome in mice with acute folate nephropathy. Here, analysis of the dataset identified enrichment of pathways involving NFκB in the kidney cortex, and a targeted data mining approach identified components of the noncanonical NFκB pathway, including the upstream kinase mitogen-activated protein kinase kinase kinase 14 (MAP3K14), the NFκB DNA binding heterodimer RelB/NFκB2, and proteins involved in NFκB2 p100 ubiquitination and proteasomal processing to p52, as upregulated. Immunohistochemistry localized MAP3K14 expression to tubular cells in acute folate nephropathy and human AKI. In vivo, kidney expression levels of NFκB2 p100 and p52 increased rapidly after folic acid injection, as did DNA binding of RelB and NFκB2, detected in nuclei isolated from the kidneys. Compared with wild-type mice, MAP3K14 activity-deficient aly/aly (MAP3K14^aly/aly) mice had less kidney dysfunction, inflammation, and apoptosis in acute folate nephropathy and less kidney dysfunction and a lower mortality rate in cisplatin-induced AKI. The exchange of bone marrow between wild-type and MAP3K14^aly/aly mice did not affect the survival rate of either group after folic acid injection. In cultured tubular cells, MAP3K14 small interfering RNA targeting decreased inflammation and cell death. Additionally, cell culture and in vivo studies identified the chemokines MCP-1, RANTES, and CXCL10 as MAP3K14 targets in tubular cells. In conclusion, MAP3K14 promotes kidney injury through promotion of inflammation and cell death and is a promising novel therapeutic target.

NIK regulates MT1-MMP activity and promotes glioma cell invasion independently of the canonical NF-κB pathway

A growing body of evidence implicates the noncanonical NF-κB pathway as a key driver of glioma invasiveness and a major factor underlying poor patient prognoses. Here, we show that NF-κB-inducing kinase (NIK/MAP3K14), a critical upstream regulator of the noncanonical NF-κB pathway, is both necessary and sufficient for cell-intrinsic invasion, as well as invasion induced by the cytokine TWEAK, which is strongly associated with tumor pathogenicity. NIK promotes dramatic alterations in glioma cell morphology that are characterized by extensive membrane branching and elongated pseudopodial protrusions. Correspondingly, NIK increases the phosphorylation, enzymatic activity and pseudopodial localization of membrane type-1 matrix metalloproteinase (MT1-MMP/MMP14), which is associated with enhanced tumor cell invasion of three-dimensional collagen matrices. Moreover, NIK regulates MT1-MMP activity in cells lacking the canonical NF-κB p65 and cRel proteins. Finally, increased expression of NIK is associated with elevated MT1-MMP phosphorylation in orthotopic xenografts and co-expression of NIK and MT1-MMP in human tumors is associated with poor glioma patient survival. These data reveal a novel role of NIK to enhance pseudopodia formation, MT1-MMP enzymatic activity and tumor cell invasion independently of p65. Collectively, our findings underscore the therapeutic potential of approaches targeting NIK in highly invasive tumors.

A roadmap of constitutive NF-κB activity in Hodgkin lymphoma: Dominant roles of p50 and p52 revealed by genome-wide analyses

Background

NF-κB is widely involved in lymphoid malignancies; however, the functional roles and specific transcriptomes of NF-κB dimers with distinct subunit compositions have been unclear.

Methods

Using combined ChIP-sequencing and microarray analyses, we determined the cistromes and target gene signatures of canonical and non-canonical NF-κB species in Hodgkin lymphoma (HL) cells.

Results

We found that the various NF-κB subunits are recruited to regions with redundant κB motifs in a large number of genes. Yet canonical and non-canonical NF-κB dimers up- and downregulate gene sets that are both distinct and overlapping, and are associated with diverse biological functions. p50 and p52 are formed through NIK-dependent p105 and p100 precursor processing in HL cells and are the predominant DNA binding subunits. Logistic regression analyses of combinations of the p50, p52, RelA, and RelB subunits in binding regions that have been assigned to genes they regulate reveal a cross-contribution of p52 and p50 to canonical and non-canonical transcriptomes. These analyses also indicate that the subunit occupancy pattern of NF-κB binding regions and their distance from the genes they regulate are determinants of gene activation versus repression. The pathway-specific signatures of activated and repressed genes distinguish HL from other NF-κB-associated lymphoid malignancies and inversely correlate with gene expression patterns in normal germinal center B cells, which are presumed to be the precursors of HL cells.

Conclusions

We provide insights that are relevant for lymphomas with constitutive NF-κB activation and generally for the decoding of the mechanisms of differential gene regulation through canonical and non-canonical NF-κB signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0280-5) contains supplementary material, which is available to authorized users.

Mir-302c mediates influenza A virus-induced IFNβ expression by targeting NF-κB inducing kinase

Little is known about the role of microRNA during influenza A virus (IAV) infection. We observed that NIK 3'UTR luciferase activity was elevated during IAV infection. Further studies demonstrated that miR-302c reduced NIK expression, resulting in the reduction of IFNβ mRNA expression. We found that miR-302c prevented the translocation of NF-κB from the cytosol to the nucleus. Furthermore, IAV infection downregulated miR-302c expression, leading to the activation of IFNβ expression and the inhibition of viral replication. Compared to miR-302c, miR-520e cannot promote viral replication and production, although the two microRNAs target the same site of the NIK 3'UTR. Collectively, our work defines a novel signaling pathway implicated in the control of IFNβ mRNA expression during IAV infection.

The Emerging Role of miRNAs in HTLV-1 Infection and ATLL Pathogenesis

Human T-cell leukemia virus (HTLV)-1 is a human retrovirus and the etiological agent of adult T-cell leukemia/lymphoma (ATLL), a fatal malignancy of CD4/CD25+ T lymphocytes. In recent years, cellular as well as virus-encoded microRNA (miRNA) have been shown to deregulate signaling pathways to favor virus life cycle. HTLV-1 does not encode miRNA, but several studies have demonstrated that cellular miRNA expression is affected in infected cells. Distinct mechanisms such as transcriptional, epigenetic or interference with miRNA processing machinery have been involved. This article reviews the current knowledge of the role of cellular microRNAs in virus infection, replication, immune escape and pathogenesis of HTLV-1.

Catalytic subunits of the phosphatase calcineurin interact with NF-κB-inducing kinase (NIK) and attenuate NIK-dependent gene expression

Nuclear factor (NF)-κB-inducing kinase (NIK) is a serine/threonine kinase that activates NF-κB pathways, thereby regulating a wide variety of immune systems. Aberrant NIK activation causes tumor malignancy, suggesting a requirement for precise regulation of NIK activity. To explore novel interacting proteins of NIK, we performed in vitro virus screening and identified the catalytic subunit Aα isoform of serine/threonine phosphatase calcineurin (CnAα) as a novel NIK-interacting protein. The interaction of NIK with CnAα in living cells was confirmed by co-immunoprecipitation. Calcineurin catalytic subunit Aβ isoform (CnAβ) also bound to NIK. Experiments using domain deletion mutants suggested that CnAα and CnAβ interact with both the kinase domain and C-terminal region of NIK. Moreover, the phosphatase domain of CnAα is responsible for the interaction with NIK. Intriguingly, we found that TRAF3, a critical regulator of NIK activity, also binds to CnAα and CnAβ. Depletion of CnAα and CnAβ significantly enhanced lymphotoxin-β receptor (LtβR)-mediated expression of the NIK-dependent gene Spi-B and activation of RelA and RelB, suggesting that CnAα and CnAβ attenuate NF-κB activation mediated by LtβR-NIK signaling. Overall, these findings suggest a possible role of CnAα and CnAβ in modifying NIK functions.

Conditioning solid tumor microenvironment through inflammatory chemokines and S100 family proteins

Recently, there has been growing attention to the role of the tumor microenvironment (TME) in cancer growth, metastasis and emergence of chemotherapy resistance. Stromal and tumor cells make up the TME and interact with each other through a complex cross-talk manner. This interaction is facilitated by a variety of growth factors, cytokines, chemokines and S100 proteins. In this review, we focus on chemokines and their cognate receptors in regulating the tumorigenic process. Chemokines are cytokines that have chemotactic potential. Chemokine receptors are expressed on tumor cells and stromal cells. Chemokines and their cognate receptors modulate tumor growth and metastasis in a paracrine and autocrine manner. They play a major role in the modulation of stromal cell recruitment, angiogenic potential, cancer cell proliferation, survival, adhesion, invasion and metastasis to distant sites. In addition, a new class of calcium binding family S100 proteins has been getting attention as they play significant roles in tumor progression and metastasis by modulating TME. Here, we highlight recent developments regarding the inflammatory chemokine/S100 protein systems in the TME. We also focus on how chemokines/S100 proteins, through their role in the TME, modulate cancer cell ability to grow, proliferate, invade and metastasize to different organs. This review highlights the possibility of using the chemokine/chemokine receptor axis as a promising strategy in cancer therapy, the current difficulties in achieving this goal, and how it could be overcome for successful future therapeutic intervention.

Downregulation of miR-518a-3p activates the NIK-dependent NF-κB pathway in colorectal cancer

The aim of the present study was to investigate the biological role and underlying mechanisms of action of miR-518a-3p in the progression and invasion of colorectal cancer (CRC). Reverse transcription-quantitative PCR (RT-qPCR) was used to examine the mRNA expression levels of miR-518a-3p in 5 CRC cell lines (SW480, SW620, HCT116, HT29 and LoVo) in a normal colonic cell line, NCM460, as well as in tumor tissues with or without metastases. The biological effects of miR-518a-3p were assessed in the CRC cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometric analysis, and RT‑qPCR and western blot analyses were employed to evaluate the expression of miR-518a-3p targets. The regulation of NF-κB-inducing kinase (NIK) by miR-518a-3p was confirmed using luciferase activity assays. Our results revealed that miR-518a-3p was significantly downregulated in the CRC cell lines compared with the normal colonic cell line (P<0.05), as well as in the CRC tissues with distant metastases compared with the tissues without metastases. The downregulation of miR-518a-3p was associated with tumor size, distant metastasis and TNM stage in the patients with CRC. Moreover, the ectopic expression of miR-518a-3p and the inhibition of NIK by RNA interference markedly reduced cell proliferation and enhanced the apoptosis of CRC cells. Further experiments revealed that NIK, a regulator of NF-κB, was a downstream target of miR-518a-3p. The presents findings indicate that miR-518a-3p plays an important role in the progression of CRC by targeting NIK.

Nuclear Factor-κB Activation as a Pathological Mechanism of Lipid Metabolism and Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall with lipid-laden lesions, involving a complex interaction between multiple different cell types and cytokine networks. Inflammatory responses mark all stages of atherogenesis: from lipid accumulation in the intima to plaque formation and eventual rupture. One of the most important regulators of inflammation is the transcription factor nuclear factor-κB (NF-κB), which is activated through the canonical and noncanonical pathways in response to various stimuli. NF-κB has long been regarded as a proatherogenic factor, because it is implicated in multiple pathological processes during atherogenesis, including foam cell formation, vascular inflammation, proliferation of vascular smooth muscle cells, arterial calcification, and plaque progression. In contrast, inhibition of NF-κB signaling has been shown to protect against atherosclerosis. This chapter aims to discuss recent progress on the roles of NF-κB in lipid metabolism and atherosclerosis and also to highlight its potential therapeutic benefits.

Relationship between expression of NIBP and noncanonical NF-κB signaling: Clinical significance in colon carcinoma

AIM: To investigate the expression of NIK, IKKβ binding protein (NIBP), phosphorylated p100 (p-p100), p52, CD44, Vimentin and E-cadherin in colon carcinoma and to explore their clinical significance.

METHODS: Immunohistochemistry was used to detect the expression of NIBP, p-p100, p52, CD44, E-cadherin and Vimentin in 114 paraffin-embedded colon carcinoma tissues, 20 colon adenoma tissues and 50 normal colon mucosa tissues.

RESULTS: The positive expression of NIBP, p-p100, p52, CD44 and Vimentin in colon cancer tissues with metastasis was much higher than that in colon cancer tissues without metastasis, colon adenoma tissues and normal colon mucosa tissues, while the expression of E-cadherin showed a reverse trend (P < 0.05). The expression of NIBP, p-p100, p52, CD44, Vimentin and E-cadherin in colon cancer tissues was related with depth of invasion, TNM stage, lymph node metastasis and distant metastasis (P < 0.05). There were significant correlations between the expression of p-p100 and p52 or NIBP, and between the expression of CD44 and p52, E-cadherin, or Vimentin.

CONCLUSION: NIBP may regulate the epithelial-mesenchymal transition process by activating the noncanonical nuclear factor-κB (NF-κB) signal pathway and thus play an important role in the development, invasion and metastasis of colon cancer.

NIK is required for NF-κB-mediated induction of BAG3 upon inhibition of constitutive protein degradation pathways

Recently, we reported that induction of the co-chaperone Bcl-2-associated athanogene 3 (BAG3) is critical for recovery of rhabdomyosarcoma (RMS) cells after proteotoxic stress upon inhibition of the two constitutive protein degradation pathways, that is, the ubiquitin-proteasome system by Bortezomib and the aggresome-autophagy system by histone deacetylase 6 (HDAC6) inhibitor ST80. In the present study, we investigated the molecular mechanisms mediating BAG3 induction under these conditions. Here, we identify nuclear factor-kappa B (NF-κB)-inducing kinase (NIK) as a key mediator of ST80/Bortezomib-stimulated NF-κB activation and transcriptional upregulation of BAG3. ST80/Bortezomib cotreatment upregulates mRNA and protein expression of NIK, which is accompanied by an initial increase in histone H3 acetylation. Importantly, NIK silencing by siRNA abolishes NF-κB activation and BAG3 induction by ST80/Bortezomib. Furthermore, ST80/Bortezomib cotreatment stimulates NF-κB transcriptional activity and upregulates NF-κB target genes. Genetic inhibition of NF-κB by overexpression of dominant-negative IκBα superrepressor (IκBα-SR) or by knockdown of p65 blocks the ST80/Bortezomib-stimulated upregulation of BAG3 mRNA and protein expression. Interestingly, inhibition of lysosomal activity by Bafilomycin A1 inhibits ST80/Bortezomib-stimulated IκBα degradation, NF-κB activation and BAG3 upregulation, indicating that IκBα is degraded via the lysosome in the presence of Bortezomib. Thus, by demonstrating a critical role of NIK in mediating NF-κB activation and BAG3 induction upon ST80/Bortezomib cotreatment, our study provides novel insights into mechanisms of resistance to proteotoxic stress in RMS.

Mouse hepatocyte overexpression of NF-κB-inducing kinase (NIK) triggers fatal macrophage-dependent liver injury and fibrosis

Damaged, necrotic, or apoptotic hepatocytes release damage-associated molecular patterns that initiate sterile inflammation, and liver inflammation drives liver injury and fibrosis. Here we identified hepatic nuclear factor kappa B (NF-κB)-inducing kinase (NIK), a Ser/Thr kinase, as a novel trigger of fatal liver inflammation. NIK is activated by a broad spectrum of stimuli. It was up-regulated in injured livers in both mice and humans. In primary mouse hepatocytes, NIK overexpression stimulated, independently of cell injury and death, release of numerous chemokines and cytokines that activated bone marrow-derived macrophages (BMDMs). BMDMs in turn secreted proapoptotic molecules that stimulated hepatocyte apoptosis. Hepatocyte-specific expression of the NIK transgene triggered massive liver inflammation, oxidative stress, hepatocyte apoptosis, and liver fibrosis, leading to weight loss, hypoglycemia, and death. Depletion of Kupffer cells/macrophages reversed NIK-induced liver destruction and death.

CONCLUSION

the hepatocyte NIK-liver immune cell axis promotes liver inflammation, injury, and fibrosis, thus driving liver disease progression.

Limitation of immune tolerance-inducing thymic epithelial cell development by Spi-B-mediated negative feedback regulation

Medullary thymic epithelial cells (mTECs) expressing the autoimmune regulator AIRE and various tissue-specific antigens (TSAs) are critical for preventing the onset of autoimmunity and may attenuate tumor immunity. However, molecular mechanisms controlling mTEC development remain elusive. Here, we describe the roles of the transcription factor Spi-B in mTEC development. Spi-B is rapidly up-regulated by receptor activator of NF-κB ligand (RANKL) cytokine signaling, which triggers mTEC differentiation, and in turn up-regulates CD80, CD86, some TSAs, and the natural inhibitor of RANKL signaling, osteoprotegerin (OPG). Spi-B-mediated OPG expression limits mTEC development in neonates but not in embryos, suggesting developmental stage-specific negative feedback regulation. OPG-mediated negative regulation attenuates cellularity of thymic regulatory T cells and tumor development in vivo. Hence, these data suggest that this negative RANKL-Spi-B-OPG feedback mechanism finely tunes mTEC development and function and may optimize the trade-off between prevention of autoimmunity and induction of antitumor immunity.

Negative regulation of RelA phosphorylation: emerging players and their roles in cancer

NF-κB signaling contributes to human disease processes, notably inflammatory diseases and cancer. Many advances have been made in understanding mechanisms responsible for abnormal NF-κB activation with RelA post-translational modification, particularly phosphorylation, proven to be critical for RelA function. While the majority of studies have focused on identifying kinases responsible for NF-κB phosphorylation and pathway activation, recently progress has also been made in understanding the negative regulators important for restraining RelA activity. Here we summarize negative regulators of RelA phosphorylation, their targeting sites in RelA and biological functions through negative regulation of RelA activation. Finally, we emphasize the tumor suppressor-like roles that these negative regulators can assume in human cancers.

The effect of 17-methoxyl-7-hydroxy-benzene-furanchalcone on NF-κB and the inflammatory response during myocardial ischemia reperfusion injury in rats

The aim of this study was to investigate the effect of 17-methoxyl-7-hydroxy-benzene-furanchalcone (MHBFC) on nuclear factor-kappa-binding (NF-κB) and the inflammatory response in rats with myocardial ischemia reperfusion injury (MI/RI). Sprague-Dawley rats were randomly divided into 7 groups, and the rat MI/RI model was established by the ligation of the left anterior descending for 30 minutes followed by ligation release for 1 hour. Areas of myocardial infarction were measured using Evans blue-2,3,5-Triphenyltetrazolium chloride (TTC) staining. Levels of malondialdehyde, glutathione peroxidase, and total superoxide dismutase were assessed. Release of interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-10 (IL-10) was measured by means of an enzyme-linked immunosorbent assay. NF-κBp65 and intercellular adhesion molecule-1 protein expression and caspase-3 and adenine nucleotide translocator-1 messenger RNA expression were evaluated by immunohistochemistry and reverse transcription polymerase chain reaction, respectively. Pretreatment with MHBFC decreased the infarction areas, the malondialdehyde, IL-1β and IL-6 levels, the expression of caspase-3, NF-κBp65, and intercellular adhesion molecule-1. Further, MHBFC increased total superoxide dismutase and glutathione peroxidase activities, the release of IL-10, and the expression of adenine nucleotide translocator-1 messenger RNA compared with the results of the model group. The experiment showed that MHBFC protected the heart against MI/RI possibly by reducing lipid peroxidation damage while inhibiting the activity of NF-κBp65 and the inflammatory response.

Negative feedback regulation of NF-κB-inducing kinase is proteasome-dependent but does not require cellular inhibitors of apoptosis

Non-canonical NF-κB signaling is controlled by the precise regulation of NF-κB inducing kinase (NIK) stability. NIK is constitutively ubiquitylated by cellular inhibitor of apoptosis (cIAP) proteins 1 and 2, leading to its complete proteasomal degradation in resting cells. Following stimulation, cIAP-mediated ubiquitylation of NIK ceases and NIK is stabilized, allowing for inhibitor of κB kinase (IKK)α activation and non-canonical NF-κB signaling. Non-canonical NF-κB signaling is terminated by feedback phosphorylation of NIK by IKKα that promotes NIK degradation; however, the mechanism of active NIK protein turnover remains unknown. To address this question, we established a strategy to precisely distinguish between basal degradation of newly synthesized endogenous NIK and induced active NIK in stimulated cells. Using this approach, we found that IKKα-mediated degradation of signal-induced activated NIK occurs through the proteasome. To determine whether cIAP1 or cIAP2 play a role in active NIK turnover, we utilized a Smac mimetic (GT13072), which promotes degradation of these E3 ubiquitin ligases. As expected, GT13072 stabilized NIK in resting cells. However, loss of the cIAPs did not inhibit proteasome-dependent turnover of signal-induced NIK showing that unlike the basal regulatory mechanism, active NIK turnover is independent of cIAP1 and cIAP2. Our results therefore establish that the negative feedback control of IKKα-mediated NIK turnover occurs via a novel proteasome-dependent and cIAP-independent mechanism.

Significant involvement of nuclear factor-κB-inducing kinase in proper differentiation of αβ and γδ T cells

Nuclear factor-κB-inducing kinase (NIK) is known to play a critical role in maintaining proper immune function. This is exemplified in the spontaneous mutant mouse lacking functional NIK, alymphoplasia (aly), which is simultaneously immune-compromised and autoimmune-prone. To investigate the role of NIK in αβ T-cell repertoire formation, we analysed T-cell development in aly/aly mice bearing a transgenic T-cell receptor (TCR). Although there were no apparent abnormalities in the mature αβ T cells of non-transgenic aly/aly mice, the maturation efficiency of idiotype(high+) T cells in the TCR-transgenic mice was lower in aly/aly mice compared with those found in aly/+ mice, suggesting that the mature αβ T-cell repertoire could be altered by the absence of functional NIK. In one strain of TCR-transgenic aly/aly mice with a negatively selecting H-2 background, the proportion of CD8(low+) idiotype(high+) cells, which are thought to potentially represent the γδ lineage of T cells, was markedly decreased. When the γδ T cells in non-transgenic aly/aly mice were investigated, the proportion of γδ T cells in the peripheral organs of aly/aly mice was found to be one-half to one-fifth of those in aly/+ mice. Analyses of bone marrow chimera mice indicated that NIK in host cells, rather than in donor cells was important for generating a normal number of peripheral γδ T cells. Collectively, these results suggest that NIK could be involved in thymic positive selection of some αβ T cells and that NIK in non-haematopoietic cells is important for the optimal development and/or maintenance of γδ T cells.

A cell-intrinsic requirement for NF-κB-inducing kinase in CD4 and CD8 T cell memory

NF-κB-inducing kinase [(NIK), MAP3K14] is an essential kinase linking a subset of TNFR family members to the noncanonical NF-κB pathway. To assess the cell-intrinsic role of NIK in murine T cell function, we generated mixed bone marrow chimeras using bone marrow from NIK knockout (KO) and wild-type (WT) donor mice and infected the chimeras with lymphocytic choriomeningitis virus (LCMV). The chimeras possess an apparently normal immune system, including a mixture of NIK KO and WT T cells, and the virus was cleared normally. Comparison of the NIK KO and WT CD4 and CD8 T cell responses at 8 d post infection revealed modest but significant differences in the acute response. In both CD4 and CD8 compartments, relatively fewer activated (CD44(hi)) NIK KO T cells were present, but within the CD44(hi) population, a comparable percentage of the activated cells produced IFN-γ in response to ex vivo stimulation with antigenic LCMV peptides, although IL-7R expression was reduced in the NIK KO CD8 T cells. Assessment of the LCMV-specific memory at 65 d post infection revealed many more LCMV-specific WT memory T cells than NIK KO memory T cells in both the CD4 and the CD8 compartments, although the small number of surviving NIK KO memory T cells responded to secondary challenge with virus. These results demonstrate a cell-intrinsic requirement for NIK in the generation and/or maintenance of memory T cells in response to acute viral infection.

NIK controls classical and alternative NF-κB activation and is necessary for the survival of human T-cell lymphoma cells

PURPOSE

Peripheral T-cell lymphomas (PTCL) are a heterogeneous entity of neoplasms with poor prognosis, a lack of effective therapies, and a largely unknown molecular pathology. Deregulated NF-κB activity has been associated with several lymphoproliferative diseases, but its importance in T-cell lymphomagenesis is poorly understood. We investigated the function of the NF-κB-inducing kinase (NIK), in this pathway and its role as a potential molecular target in T-cell lymphomas.

EXPERIMENTAL DESIGN

We used immunohistochemistry to analyze the expression of different NF-κB members in primary human PTCL samples and to study its clinical impact. With the aim of inhibiting the pathway, we used genetic silencing of NIK in several T-cell lymphoma cell lines and observed its effect on downstream targets and cell viability.

RESULTS

We showed that the NF-κB pathway was activated in a subset of PTCLs associated with poor overall survival. NIK was overexpressed in a number of PTCL cell lines and primary samples, and a pivotal role for NIK in the survival of these tumor cells was unveiled. NIK depletion led to a dramatic induction of apoptosis in NIK-overexpressing cell lines and also showed a more pronounced effect on cell survival than inhibitor of kappa B kinase (IKK) knockdown. NIK silencing induced a blockage of both classical and alternative NF-κB activation and reduced expression of several prosurvival and antiapoptotic factors.

CONCLUSIONS

The results of the present study indicate that NIK could be a promising therapeutic target in these aggressive malignancies.

Noncanonical NF-κB activation by the oncoprotein Tio occurs through a nonconserved TRAF3-binding motif

Members of the nuclear factor κB (NF-κB) family of transcription factors regulate many cellular functions. Activation of NF-κB signaling is commonly classified as occurring through canonical or noncanonical pathways. Most NF-κB-inducing stimuli, including the viral oncoprotein Tio, lead to a concerted activation of both NF-κB pathways; however, extensive crosstalk at multiple levels between these signaling cascades restricts the ability to discriminate between the canonical and the noncanonical effects. We showed that noncanonical NF-κB activation by Tio depends on a distinct sequence motif that directly recruits tumor necrosis factor receptor-associated factor 3 (TRAF3). Through its TRAF3-binding motif, Tio triggered a ubiquitin-independent depletion of TRAF3 from the cytosol, which prevented TRAF3 from inhibiting signaling through the noncanonical NF-κB cascade. Furthermore, the Tio-TRAF3 interaction did not affect components of the canonical NF-κB signaling pathway or the expression of target genes; thus, Tio induced noncanonical NF-κB independently of crosstalk with the canonical pathway. Together, these data identify a distinct molecular mechanism of noncanonical NF-κB activation that should enable studies into the particular functions of this pathway.

Microfluidics assisted synthesis and bioevaluation of sinomenine derivatives as antiinflammatory agents

Sinomenine (1) is currently used for the treatment of rheumatoid arthritis (RA) in China and there is still room for the improvement of its efficacy. In present study, capillary based microfluidic system was effectively applied for the syntheses of two novel series of sinomenine derivatives. The Heck reactions in microreactor gave much higher conversions compared to the batch ones. The two-step synthesis of the isoxazoline in microreactor greatly shortened the reaction time without any isolation of intermediates. The inhibitory activity of synthesized compounds on the TNF-α-induced nuclear factor kappa B (NF-κB) activation was evaluated in vitro. Among the compounds, 3c and 3g showed the potent inhibitory activity. Furthermore, 3g exhibited the antiinflammatory effect in vivo.

Downregulation of TRAF2 mediates NIK-induced pancreatic cancer cell proliferation and tumorigenicity

BACKGROUND

Increased levels of NF-κB are hallmarks of pancreatic ductal adenocarcinoma (PDAC) and both classical and alternative NF-κB activation pathways have been implicated.

METHODOLOGY/PRINCIPAL FINDINGS

Here we show that activation of the alternative pathway is a source for the high basal NF-κB activity in PDAC cell lines. Increased activity of the p52/RelB NF-κB complex is mediated through stabilization and activation of NF-κB-inducing kinase (NIK). We identify proteasomal downregulation of TNF receptor-associated factor 2 (TRAF2) as a mechanism by which levels of active NIK are increased in PDAC cell lines. Such upregulation of NIK expression and activity levels relays to increased proliferation and anchorage-independent growth, but not migration or survival of PDAC cells.

CONCLUSIONS/SIGNIFICANCE

Rapid growth is one characteristic of pancreatic cancer. Our data indicates that the TRAF2/NIK/NF-κB2 pathway regulates PDAC cell tumorigenicity and could be a valuable target for therapy of this cancer.

A randomized, placebo-controlled, preoperative trial of allopurinol in subjects with colorectal adenoma

Inflammation and oxidative stress play a crucial role in the development of colorectal cancer (CRC) and interference with these mechanisms represents a strategy in CRC chemoprevention. Allopurinol, a safe molecular scavenger largely used as antigout agent, has been shown to increase survival of patients with advanced CRC and to reduce CRC incidence in long-term gout users in epidemiologic studies. We conducted a randomized, double-blind, placebo-controlled preoperative trial in subjects with colorectal adenomatous polyps to assess the activity of allopurinol on biomarkers of colorectal carcinogenesis. After complete colonoscopy and biopsy of the index polyp, 73 subjects with colorectal adenomas were assigned to either placebo or one of two doses of allopurinol (100 mg or 300 mg) and treated for four weeks before polyp removal. Change of Ki-67 labeling index in adenomatous tissue was the primary endpoint. Secondary endpoints were the immunohistochemical (IHC) expression of NF-κB, β-catenin, topoisomerase-II-α, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) in adenomatous polyps and normal adjacent colonic tissue. Compared with placebo, Ki-67 levels were not significantly modulated by allopurinol, whereas β-catenin and NF-κB expression levels decreased significantly in adenomatous tissue, with a mean change from baseline of -10.6%, 95% confidence interval (CI), -20.5 to -0.7, and -8.1%, 95% CI, -22.7 to 6.5, respectively. NF-κB also decreased significantly in normal adjacent tissue (-16.4%; 95% CI, -29.0 to -3.8). No dose-response relationship was noted, except for NF-κB expression in normal tissue. Allopurinol can inhibit biomarkers of oxidative activation in colon adenomatous polyps and normal adjacent tissue. Further studies should define its potential chemopreventive activity.

The crystal structure of the catalytic domain of the NF-κB inducing kinase reveals a narrow but flexible active site

The NF-κB inducing kinase (NIK) regulates the non-canonical NF-κB pathway downstream of important clinical targets including BAFF, RANKL, and LTβ. Despite numerous genetic studies associating dysregulation of this pathway with autoimmune diseases and hematological cancers, detailed molecular characterization of this central signaling node has been lacking. We undertook a systematic cloning and expression effort to generate soluble, well-behaved proteins encompassing the kinase domains of human and murine NIK. Structures of the apo NIK kinase domain from both species reveal an active-like conformation in the absence of phosphorylation. ATP consumption and peptide phosphorylation assays confirm that phosphorylation of NIK does not increase enzymatic activity. Structures of murine NIK bound to inhibitors possessing two different chemotypes reveal conformational flexibility in the gatekeeper residue controlling access to a hydrophobic pocket. Finally, a single amino acid difference affects the ability of some inhibitors to bind murine and human NIK with the same affinity.

Molecular hallmarks of adult T cell leukemia

The molecular hallmarks of adult T cell leukemia (ATL) comprise outstanding deregulations of signaling pathways that control the cell cycle, resistance to apoptosis, and proliferation of leukemic cells, all of which have been identified by early excellent studies. Nevertheless, we are now confronted the therapeutic difficulties of ATL that is a most aggressive T cell leukemia/lymphoma. Using next-generation strategies, emerging molecular characteristics such as specific surface markers and an additional catalog of signals affecting the fate of leukemic cells have been added to the molecular hallmarks that constitute an organizing principle for rationalizing the complexities of ATL. Although human T cell leukemia virus type 1 is undoubtedly involved in ATL leukemogenesis, most leukemic cells do not express the viral protein Tax. Instead, cellular gene expression changes dominate homeostasis disorders of infected cells and characteristics of ATL. In this review, we summarize the state of the art of ATL molecular pathology, which supports the biological properties of leukemic cells. In addition, we discuss the recent discovery of two molecular hallmarks of potential generality; an abnormal microRNA pattern and epigenetic reprogramming, which strongly involve the imbalance of the molecular network of lymphocytes. Global analyses of ATL have revealed the functional impact of crosstalk between multifunctional pathways. Clinical and biological studies on signaling inhibitory agents have also revealed novel oncogenic drivers that can be targeted in future. ATL cells, by deregulation of such pathways and their interconnections, may become masters of their own destinies. Recognizing and understanding of the widespread molecular applicability of these concepts will increasingly affect the development of novel strategies for treating ATL.

APPL1 regulates basal NF-κB activity by stabilizing NIK

APPL1 is a multifunctional adaptor protein that binds membrane receptors, signaling proteins and nuclear factors, thereby acting in endosomal trafficking and in different signaling pathways. Here, we uncover a novel role of APPL1 as a positive regulator of transcriptional activity of NF-κB under basal but not TNFα-stimulated conditions. APPL1 was found to directly interact with TRAF2, an adaptor protein known to activate canonical NF-κB signaling. APPL1 synergized with TRAF2 to induce NF-κB activation, and both proteins were necessary for this process and function upstream of the IKK complex. Although TRAF2 was not detectable on APPL endosomes, endosomal recruitment of APPL1 was required for its function in the NF-κB pathway. Importantly, in the canonical pathway, APPL1 appeared to regulate the proper spatial distribution of the p65 subunit of NF-κB in the absence of cytokine stimulation, since its overexpression enhanced and its depletion reduced the nuclear accumulation of p65. By analyzing the patterns of gene transcription upon APPL1 overproduction or depletion we found altered expression of NF-κB target genes that encode cytokines. At the molecular level, overexpressed APPL1 markedly increased the level of NIK, the key component of the noncanonical NF-κB pathway, by reducing its association with the degradative complex containing TRAF2, TRAF3 and cIAP1. In turn, high levels of NIK triggered nuclear translocation of p65. Collectively, we propose that APPL1 regulates basal NF-κB activity by modulating the stability of NIK, which affects the activation of p65. This places APPL1 as a novel link between the canonical and noncanonical machineries of NF-κB activation.

Structure of the nuclear factor κB-inducing kinase (NIK) kinase domain reveals a constitutively active conformation

NF-κB-inducing kinase (NIK) is a central component in the non-canonical NF-κB signaling pathway. Excessive NIK activity is implicated in various disorders, such as autoimmune conditions and cancers. Here, we report the first crystal structure of truncated human NIK in complex with adenosine 5'-O-(thiotriphosphate) at a resolution of 2.5 Å. This truncated protein is a catalytically active construct, including an N-terminal extension of 60 residues prior to the kinase domain, the kinase domain, and 20 residues afterward. The structure reveals that the NIK kinase domain assumes an active conformation in the absence of any phosphorylation. Analysis of the structure uncovers a unique role for the N-terminal extension sequence, which stabilizes helix αC in the active orientation and keeps the kinase domain in the catalytically competent conformation. Our findings shed light on the long-standing debate over whether NIK is a constitutively active kinase. They also provide a molecular basis for the recent observation of gain-of-function activity for an N-terminal deletion mutant (ΔN324) of NIK, leading to constitutive non-canonical NF-κB signaling with enhanced B-cell adhesion and apoptosis resistance.

NF-κB–inducing kinase (NIK) promotes hyperglycemia and glucose intolerance in obesity by augmenting glucagon action

The canonical inhibitor of nuclear factor κB kinase subunit β (IKK-β)–nuclear factor of κ light polypeptide gene enhancer in B cells 1 (NF-κB1) pathway has been well documented to promote insulin resistance; however, the noncanonical NF-κB–inducing kinase (NIK)–NF-κB2 pathway is not well understood in obesity. Additionally, the contribution of counter-regulatory hormones, particularly glucagon, to hyperglycemia in obesity is unclear. Here we show that NIK promotes glucagon responses in obesity. Hepatic NIK was abnormally activated in mice with dietary or genetic obesity. Systemic deletion of Map3k14, encoding NIK, resulted in reduced glucagon responses and hepatic glucose production (HGP). Obesity is associated with high glucagon responses, and liver-specific inhibition of NIK led to lower glucagon responses and HGP and protected against hyperglycemia and glucose intolerance in obese mice. Conversely, hepatocyte-specific overexpression of NIK resulted in higher glucagon responses and HGP. In isolated mouse livers and primary hepatocytes, NIK also promoted glucagon action and glucose production, at least in part by increasing cAMP response element-binding (CREB) stability. Therefore, overactivation of liver NIK in obesity promotes hyperglycemia and glucose intolerance by increasing the hyperglycemic response to glucagon and other factors that activate CREB.

NLRP12 suppresses colon inflammation and tumorigenesis through the negative regulation of noncanonical NF-κB signaling

In vitro data suggest that a subgroup of NLR proteins, including NLRP12, inhibits the transcription factor NF-κB, although physiologic and disease-relevant evidence is largely missing. Dysregulated NF-κB activity is associated with colonic inflammation and cancer, and we found Nlrp12(-/-) mice were highly susceptible to colitis and colitis-associated colon cancer. Polyps isolated from Nlrp12(-/-) mice showed elevated noncanonical NF-κB activation and increased expression of target genes that were associated with cancer, including Cxcl13 and Cxcl12. NLRP12 negatively regulated ERK and AKT signaling pathways in affected tumor tissues. Both hematopoietic- and nonhematopoietic-derived NLRP12 contributed to inflammation, but the latter dominantly contributed to tumorigenesis. The noncanonical NF-κB pathway was regulated upon degradation of TRAF3 and activation of NIK. NLRP12 interacted with both NIK and TRAF3, and Nlrp12(-/-) cells have constitutively elevated NIK, p100 processing to p52 and reduced TRAF3. Thus, NLRP12 is a checkpoint of noncanonical NF-κB, inflammation, and tumorigenesis.

Arsenic trioxide exerts antimyeloma effects by inhibiting activity in the cytoplasmic substrates of histone deacetylase 6

Arsenic trioxide (As(2)O(3)) has shown remarkable efficacy for the treatment of multiple myeloma (MM). Histone deacetylases (HDAC) play an important role in the control of gene expression, and their dysregulation has been linked to myeloma. Especially, HDAC6, a unique cytoplasmic member of class II, which mainly functions as α-tubulin deacetylase and Hsp90 deacetylase, has become a target for drug development to treat cancer due to its major contribution in oncogenic cell transformation. However, the mechanisms of action for As(2)O(3) have not yet been defined. In this study, we investigated the effect of As(2)O(3) on proliferation and apoptosis in human myeloma cell line and primary myeloma cells, and then we studied that As(2)O(3) exerts antimyeloma effects by inhibiting activity in the α-tubulin and Hsp90 through western blot analysis and immunoprecipitation. We found that As(2)O(3) acts directly on MM cells at relatively low concentrations of 0.5~2.5 µM, which effects survival and apoptosis of MM cells. However, As(2)O(3) inhibited HDAC activity at the relatively high concentration and dose-dependent manner (great than 4 µM). Subsequently, we found that As(2)O(3) treatment in a dose- and time-dependent fashion markedly increased the level of acetylated α-tubulin and acetylated Hsp90, and inhibited the chaperone association with IKKα activities and increased degradation of IKKα. Importantly, the loss of IKKα-associated Hsp90 occurred prior to any detectable loss in the levels of IKKα, indicating a novel pathway by which As(2)O(3) down-regulates HDAC6 to destabilize IKKα protein via Hsp90 chaperone function. Furthermore, we observed the effect of As(2)O(3) on TNF-α-induced NF-κB signaling pathway was to significantly reduced phosphorylation of Ser-536 on NF-κB p65. Therefore, our studies provide an important insight into the molecular mechanism of anti-myeloma activity of As(2)O(3) in HDAC6-Hsp90-IKKα-NFκB signaling axis and the rationale for As(2)O(3) can be extended readily using all the HDAC associated diseases.

Gene-gene interaction of BLK, TNFSF4, TRAF1, TNFAIP3, and REL in systemic lupus erythematosus

OBJECTIVE

Although the number of convincingly established genetic associations with systemic lupus erythematosus (SLE) has increased sharply over the last few years, refinement of these associations is required, and their potential roles in gene-gene interactions need to be further investigated. Recent genome-wide association studies (GWAS) in SLE have produced renewed interest in B cell/T cell responses and the NF-κB signaling pathway. The aim of this study was to search for possible gene-gene interactions based on identified single-nucleotide polymorphisms (SNPs), in using an approach based on the role of signaling pathways.

METHODS

The SNPs in BLK, TNFSF4, TRAF1, TNFAIP3, and REL were replicated in order to evaluate genetic associations with SLE. TaqMan genotyping was conducted in 804 Chinese patients with SLE and 722 matched control subjects. A multiple logistic regression model was used to estimate the multiplicative interaction effect of the SNPs, and additive interactions were analyzed by 2×2 factorial designs. Data from a previously published GWAS conducted by the International Consortium on the Genetics of Systemic Lupus Erythematosus were derived for comparison and validation.

RESULTS

Single-marker analysis validated the association of BLK rs2736340 (P=4.25×10(-6)) as well as TNFSF4 rs2205960 (P=2.82×10(-5)) and TNFAIP3 rs5029939 (P=1.92×10(-3)) with SLE susceptibility in Chinese. Multiplicative interaction analysis indicated that BLK had an interactive effect with TNFSF4 in Chinese patients with SLE (P=6.57×10(-4)). Additive interaction analysis revealed interactions between TRAF1 and TNFAIP3 in both Chinese (P=2.18×10(-3)) and Caucasians (P=2.86×10(-4)). In addition, multiple tendencies toward interactions were observed, and an additive effect was observed as the number of risk genotypes increased.

CONCLUSION

The results of this study provide evidence of the possible gene-gene interactions of BLK, TNFSF4, TRAF1, TNFAIP3, and REL in SLE, which may represent a synergic effect of T cells and B cells through the NF-κB pathway in determining immunologic aberration.

Polycomb-mediated loss of miR-31 activates NIK-dependent NF-κB pathway in adult T cell leukemia and other cancers

Constitutive NF-κB activation has causative roles in adult T cell leukemia (ATL) caused by HTLV-1 and other cancers. Here, we report a pathway involving Polycomb-mediated miRNA silencing and NF-κB activation. We determine the miRNA signatures and reveal miR-31 loss in primary ATL cells. MiR-31 negatively regulates the noncanonical NF-κB pathway by targeting NF-κB inducing kinase (NIK). Loss of miR-31 therefore triggers oncogenic signaling. In ATL cells, miR-31 level is epigenetically regulated, and aberrant upregulation of Polycomb proteins contribute to miR-31 downregulation in an epigenetic fashion, leading to activation of NF-κB and apoptosis resistance. Furthermore, this emerging circuit operates in other cancers and receptor-initiated NF-κB cascade. Our findings provide a perspective involving the epigenetic program, inflammatory responses, and oncogenic signaling.

Induction of the alternative NF-κB pathway by lymphotoxin αβ (LTαβ) relies on internalization of LTβ receptor

Several tumor necrosis factor receptor (TNFR) family members activate both the classical and the alternative NF-κB pathways. However, how a single receptor engages these two distinct pathways is still poorly understood. Using lymphotoxin β receptor (LTβR) as a prototype, we showed that activation of the alternative, but not the classical, NF-κB pathway relied on internalization of the receptor. Further molecular analyses revealed a specific cytosolic region of LTβR essential for its internalization, TRAF3 recruitment, and p100 processing. Interestingly, we found that dynamin-dependent, but clathrin-independent, internalization of LTβR appeared to be required for the activation of the alternative, but not the classical, NF-κB pathway. In vivo, ligand-induced internalization of LTβR in mesenteric lymph node stromal cells correlated with induction of alternative NF-κB target genes. Thus, our data shed light on LTβR cellular trafficking as a process required for specific biological functions of NF-κB.

NF-κB inducing kinase, NIK mediates cigarette smoke/TNFα-induced histone acetylation and inflammation through differential activation of IKKs

BACKGROUND

Nuclear factor (NF)-κB inducing kinase (NIK) is a central player in the non-canonical NF κB pathway, which phosphorylates IκB kinase α (IKKα) resulting in enhancement of target gene expression. We have recently shown that IKKα responds to a variety of stimuli including oxidants and cigarette smoke (CS) regulating the histone modification in addition to its role in NF-κB activation. However, the primary signaling mechanism linking CS-mediated oxidative stress and TNFα with histone acetylation and pro-inflammatory gene transcription is not well understood. We hypothesized that CS and TNFα increase NIK levels causing phosphorylation of IKKα, which leads to histone acetylation.

METHODOLOGY

To test this hypothesis, we investigated whether NIK mediates effects of CS and TNFα on histone acetylation in human lung epithelial cells in vitro and in lungs of mouse exposed to CS in vivo. CS increased the phosphorylation levels of IKKα/NIK in lung epithelial cells and mouse lungs. NIK is accumulated in the nuclear compartment, and is recruited to the promoters of pro-inflammatory genes, to induce posttranslational acetylation of histones in response to CS and TNFα. Cells in which NIK is knocked down using siRNA showed partial attenuation of CSE- and TNFα-induced acetylation of histone H3 on pro-inflammatory gene promoters. Additional study to determine the role of IKKβ/NF-κB pathway in CS-induced histone acetylation suggests that the canonical pathway does not play a role in histone acetylation particularly in response to CS in mouse lungs.

CONCLUSIONS

Overall, our findings provide a novel role for NIK in CS- and TNFα-induced histone acetylation, especially on histone H3K9.

FKBP51 and the NF-κB regulatory pathway in cancer

Constitutive activation of NF-κB occurs in a significant percentage of human cancers. Genetic abnormalities of tumors often enhance normal NF-κB signaling. Chronic inflammation is also associated with constitutive NF-κB activation and increases the risk of cancer. Aberrant NF-κB activation favors cellular transformation, sustains cancer survival, and contributes to tumor invasion. Strategies to inhibit NF-κB represent a promising therapeutic option against cancer. In the last decade, several studies point to the large immunophilin FKBP51 as an important element for the control of NF-κB activation in human neoplasia. This article is an overview of the causes of aberrant NF-κB regulation in cancer and highlights recent papers that implicate FKBP51 in such deregulation.

Immune-enhancing effect of Danggwibohyeoltang, an extract from Astragali Radix and Angelicae gigantis Radix, in vitro and in vivo

Danggwibohyeoltang (DGBHT) is an oriental herbal prescription consisting of two herbs: Astragali Radix and Angelicae gigantis Radix. We examined the immune-enhancing effect of DGBHT in mice using the forced swimming test (FST) and in vitro tests in peritoneal macrophages. After daily oral administration of DGBHT, blood biochemical parameters related to fatigue were measured after the FST. The immobility time in the FST was significantly decreased in the DGBHT-treated group (200 mg/kg) on the 10th and 14th days. DGBHT (100~~200 mg/kg) treatment significantly increased glucose levels, acting as an energy source. Lactic dehydrogenase levels, which are accurate indicators of muscle damage, tended to decline after DGBHT administration (100~200 mg/kg). When DGBHT (200 mg/kg) was orally administered to mice, creatine kinase levels tended to decrease; however, this decrease was not significant. DGBHT did not have any effects on the variation of total protein and blood urea nitrogen levels. Further, we examined how DGBHT regulates cytokine production, nitric oxide (NO) production, and nuclear factor-kappa B (NF-κB) activation in mouse peritoneal macrophages. When DGBHT was used in combination with recombinant interferon-gamma (rIFN-γ), there was a noticeable cooperative induction of NO production and NF-κB activation. Moreover, rIFN-γ plus DGBHT treatment of peritoneal macrophages significantly increased the production of tumor necrosis factor-alpha (TNF-α) and interleukin-12 (IL-12). These results suggest that DGBHT improves immune function through the changes in indicators related to fatigue and the regulatory effects on immunological parameters, such as TNF-α, IL-12, NO production, and NF-κB activation.

The complex interplay between autophagy and NF-κB signaling pathways in cancer cells

Tight regulation of both the NF-κB pathway and the autophagy process is necessary for maintenance of cellular homeostasis. Deregulation of both pathways is frequently observed in cancer cells and is associated with tumorigenesis and tumor cell resistance to cancer therapies. Autophagy is involved in several cellular functions regulated by NF-κB including cell survival, differentiation, senescence, inflammation, and immunity. On a molecular level, autophagy and NF-κB share common upstream signals and regulators and can control each other through positive or negative feedback loops, thus ensuring homeostatic responses. Here, we summarize and discuss the most recent discoveries that shed new light on the complex interplay between autophagy and NF-κB signaling pathways; this certainly has functional relevance in tumorigenesis and tumor responses to therapy.