The oncoprotein Bcl-3 directly transactivates through kappa B motifs via association with DNA-binding p50B homodimers

Nuclear Factor-kappaB in Autoimmunity: Man and Mouse

NF-κB (nuclear factor-kappa B) is a transcription complex crucial for host defense mediated by innate and adaptive immunity, where canonical NF-κB signaling, mediated by nuclear translocation of RelA, c-Rel, and p50, is important for immune cell activation, differentiation, and survival. Non-canonical signaling mediated by nuclear translocation of p52 and RelB contributes to lymphocyte maturation and survival and is also crucial for lymphoid organogenesis. We outline NF-κB signaling and regulation, then summarize important molecular contributions of NF-κB to mechanisms of self-tolerance. We relate these mechanisms to autoimmune phenotypes described in what is now a substantial catalog of immune defects conferred by mutations in NF-κB pathways in mouse models. Finally, we describe Mendelian autoimmune syndromes arising from human NF-κB mutations, and speculate on implications for understanding sporadic autoimmune disease.

Bcl-3 is a novel biomarker of renal fibrosis in chronic kidney disease

Progressive renal fibrosis in chronic kidney disease (CKD) greatly contributes to end-stage renal failure and is associated with high mortality. The identification of renal fibrosis biomarkers for the diagnosis and the monitoring of disease progression in CKD is urgently needed. Whole-transcriptomic analysis of renal tissues in a unilateral ureteral obstruction (UUO) mouse model revealed that the mRNA level of Bcl-3, an atypical member of the IκB family, was induced 6.3-fold 2 days after UUO. Compared with renal tissues in sham-operated mice, increases in Bcl-3 mRNA and protein in the renal tissues in the UUO model were accompanied with increases in other markers of renal fibrosis, including human epididymis protein 4 (HE4), a recently identified biomarker of renal fibrosis. Immunohistochemical analysis revealed that both Bcl-3 and HE4 were located in the plasma of renal tubule cells. Serum protein levels of Bcl-3 and HE4 rose with the development of renal fibrosis in UUO mouse model. We found that the serum protein levels of both HE4 and Bcl-3 were elevated in CKD patients compared with healthy controls. Moreover, a significant positive correlation between Bcl-3 and HE4 (r = 0.939, p < 0.0001) was observed in CKD patients. These data suggest that Bcl-3 can serve as a novel valuable biomarker of renal fibrosis in CKD.

Toll-Like Receptor Signaling and Its Inducible Proteins

Studies that bridge innate immunity and various diseases are making rapid advances. Macrophages and dendritic cells play a leading role in innate immunity, using pattern recognition receptors (PRRs) to sense both pathogen invasion and danger signals. Among these PRRs, the Toll-like receptors (TLRs) play a central role in the immune response by recognizing not only pathogen-associated molecular patterns from bacteria and viruses but also damage-associated molecular patterns from dying or injured cells. These TLR family molecules facilitate not only the elimination of pathogens but also the development of various disorders, including arteriosclerosis, cancer, and metabolic syndrome. TLRs activate signaling pathways that result in the production of cytokines, chemokines, and various inducible molecules associated with the immune response. Although most components of the innate immune signaling pathways, such as the TLR family and its downstream signaling, have been identified, the physiological roles of many TLR signal-inducible proteins remain unclear. Recent studies have shown that some TLR-inducible proteins are critical in the immune response and the development of various disorders. In this review, we focus on the TLR signaling pathways and the roles of some TLR-inducible proteins.

Bcl3: a regulator of NF-κB inducible by TWEAK in acute kidney injury with anti-inflammatory and antiapoptotic properties in tubular cells

Acute kidney injury (AKI) is characterized by tubular cell death and interstitial inflammation. TWEAK promotes experimental kidney injury and activates the transcription factor NF-κB, a key regulator of genes involved in cell survival and inflammatory response. In search of potential therapeutic targets for AKI, we compared a transcriptomics database of NF-κB-related genes from murine AKI-kidneys with a transcriptomics database of TWEAK-stimulated cultured tubular cells. Four out of twenty-four (17%) genes were significantly upregulated (false discovery rate, FDR<0.05), while nine out of twenty-four (37%) genes were significantly upregulated at FDR <0.1 in both databases. Bcl3 was the top upregulated NF-κB-related gene in experimental AKI and one of the most upregulated genes in TWEAK-stimulated tubular cells. Quantitative reverse transcription PCR (qRT-PCR), western blot and immunohistochemistry confirmed Bcl3 upregulation in both experimental conditions and localized increased Bcl3 expression to tubular cells in AKI. Transcriptomics database analysis revealed increased Bcl3 expression in numerous experimental and human kidney conditions. Furthermore, systemic TWEAK administration increased kidney Bcl3 expression. In cultured tubular cells, targeting Bcl3 by siRNA resulted in the magnification of TWEAK-induced NF-κB transcriptional activity, chemokine upregulation and Klotho downregulation, and in the sensitization to cell death induced by TWEAK/TNFα/interferon-γ. In contrast, Bcl3 overexpression decreased NF-κB transcriptional activity, inflammatory response and cell death while dampening the decrease in Klotho expression. In conclusion, Bcl3 expressed in response to TWEAK stimulation decreases TWEAK-induced inflammatory and lethal responses. Therefore, therapeutic upregulation of Bcl3 activity should be explored in kidney disease because it has advantages over chemical inhibitors of NF-κB that are known to prevent inflammatory responses but can also sensitize the cells to apoptosis.

Balanced Bcl-3 expression in murine CD4+ T cells is required for generation of encephalitogenic Th17 cells

The function of NF-κB family members is controlled by multiple mechanisms including the transcriptional regulator Bcl-3, an atypical member of the IκB family. By using a murine model of conditional Bcl-3 overexpression specifically in T cells, we observed impairment in the development of Th2, Th1, and Th17 cells. High expression of Bcl-3 promoted CD4⁺ T-cell survival, but at the same time suppressed proliferation in response to TCR stimulation, resulting in reduced CD4⁺ T-cell expansion. As a consequence, T-cell-specific overexpression of Bcl-3 led to reduced inflammation in the small intestine of mice applied with anti-CD3 in a model of gut inflammation. Moreover, impaired Th17-cell development resulted in the resistance of Bcl-3 overexpressing mice to EAE, a mouse model of multiple sclerosis. Thus, we concluded that fine-tuning expression of Bcl-3 is needed for proper CD4⁺ T-cell development and is required to sustain Th17-cell mediated pathology.

The NF-κB1 is a key regulator of acute but not chronic renal injury

The NF-κB family of transcription factors is important for many cellular functions, in particular initiation and propagation of inflammatory and immune responses. However, recent data has suggested that different subunits of the NF-κB family can suppress the inflammatory response. NF-κB1, from the locus nfκb1, can inhibit transcription, acting as a brake to the recognised pro-inflammatory activity of other NF-κB subunits. We tested the function of NF-κB1 in an acute (nephrotoxic serum (NTS) nephritis) and a chronic (unilateral ureteric obstruction (UUO)) model of renal injury using NF-κB1 (nfκb1^−/−) knockout mice. Deficiency in NF-κB1 increased the severity of glomerular injury in NTS-induced nephritis and was associated with greater proteinuria and persistent pro-inflammatory gene expression. Induction of disease in bone marrow chimeric mice demonstrated that the absence of NF-κB1 in either bone marrow or glomerular cells increased the severity of injury. Early after UUO (day 3) there was more severe histological injury in the nfκb1^−/− mice but by day 10, disease severity was equivalent in wild type and nfκb1^−/− mice. In conclusion, NF-κB1 modifies acute inflammatory renal injury but does not influence chronic fibrotic injury.

Elevated levels of Bcl-3 inhibits Treg development and function resulting in spontaneous colitis

Bcl-3 is an atypical NF-κB family member that regulates NF-κB-dependent gene expression in effector T cells, but a cell-intrinsic function in regulatory T (Treg) cells and colitis is not clear. Here we show that Bcl-3 expression levels in colonic T cells correlate with disease manifestation in patients with inflammatory bowel disease. Mice with T-cell-specific overexpression of Bcl-3 develop severe colitis that can be attributed to defective Treg cell development and function, leading to the infiltration of immune cells such as pro-inflammatory γδT cells, but not αβ T cells. In Treg cells, Bcl-3 associates directly with NF-κB p50 to inhibit DNA binding of p50/p50 and p50/p65 NF-κB dimers, thereby regulating NF-κB-mediated gene expression. This study thus reveals intrinsic functions of Bcl-3 in Treg cells, identifies Bcl-3 as a potential prognostic marker for colitis and illustrates the mechanism by which Bcl-3 regulates NF-κB activity in Tregs to prevent colitis.

Bcl-3 modulates effector T cell responses, but the importance of Bcl-3 in T regulatory cells and autoimmunity is not clear. Here the authors show that Bcl-3 impedes NF-κB DNA binding to alter T regulatory cell development and function, causing spontaneous colitis in mice.

Bcl-3 regulates TGFβ signaling by stabilizing Smad3 during breast cancer pulmonary metastasis

Transforming growth factor beta (TGFβ) signaling in breast cancer is selectively associated with pulmonary metastasis. However, the underlying mechanisms remain unclear. Here we show that Bcl-3, a member of the IκB family, serves as a critical regulator in TGFβ signaling to modulate breast cancer pulmonary metastasis. Bcl-3 expression was significantly associated with metastasis-free survival in breast cancer patients. Bcl-3 deletion inhibited the migration and invasion of breast cancer cells in vitro, as well as breast cancer lung metastasis in vivo. Bcl-3 was required for the expression of downstream TGFβ signaling genes that are involved in breast cancer lung metastasis. Bcl-3 knockdown enhanced the degradation of Smad3 but not Smad2 following TGFβ treatment. Bcl-3 could bind to Smad3 and prevent the ubiquitination and degradation of Smad3 protein. These results indicate that Bcl-3 serves as a promising target to prevent breast tumor lung metastasis.

Effect of curcumin and paclitaxel on breast carcinogenesis

Global cancer burden increased to 14.1 million new cases in 2012; and breast cancer is the most common cancer in women worldwide, with nearly 1.7 million new cases diagnosed in 2012. Curcumin is the major bioactive ingredient extracted from the rhizome of the plant Curcuma longa (turmeric). Paclitaxel is a microtubule-stabilizing agent originally isolated from the bark of Taxus brevifolia. Curcumin and paclitaxel were evaluated with two human breast cancer cell lines as the luminal MCF-7 and the basal-like MDA-MB-231 that are either positive or negative for hormonal receptors estrogen receptor, progesterone receptor and HER2, respectively. Results indicated that curcumin combined with paclitaxel decreased c-Ha-Ras, Rho-A, p53 and Bcl-xL gene expression in comparison to control and substances alone in MCF-7 cell line. These two substances alone and combined decreased gene expression of Bcl-2 and NF-κB. However, CCND1 increased when both substances were combined in MCF-7 cells. Such substances decreased Bcl-2 and increased Bax protein expression. However, curcumin alone decreased IκBα and Stat-3 gene expression. Paclitaxel alone and combined increased IκBα and Stat-3. Curcumin alone and combined with paclitaxel increased p53, Bid, caspase-3, caspase-8 and Bax gene expression in MDA-MB-231, whereas Bcl-xL decreased such expression in MDA-MB-231 cells. When paclitaxel and curcumin were combined the expression of Bcl-2 protein was decreased. However, either substance alone and combined increased Bax protein expression corroborating the apoptotic effect of these substances. It can be concluded that curcumin may be of considerable value in synergistic therapy of breast cancer reducing the associated toxicity with use of drugs.

Hepatic B cell leukemia-3 promotes hepatic steatosis and inflammation through insulin-sensitive metabolic transcription factors

BACKGROUND & AIMS

The pathomechanisms underlying non-alcoholic fatty liver disease (NAFLD) and the involved molecular regulators are incompletely explored. The nuclear factor-kappa B (NF-κB)-cofactor gene B cell leukemia-3 (Bcl-3) plays a critical role in altering the transcriptional capacity of NF-κB - a key inducer of inflammation - but also of genes involved in cellular energy metabolism.

METHODS

To define the role of Bcl-3 in non-alcoholic steatohepatitis (NASH), we developed a novel transgenic mouse model with hepatocyte-specific overexpression of Bcl-3 (Bcl-3^Hep) and employed a high-fat, high-carbohydrate dietary feeding model. To characterize the transgenic model, deep RNA sequencing was performed. The relevance of the findings was confirmed in human liver samples.

RESULTS

Hepatocyte-specific overexpression of Bcl-3 led to pronounced metabolic derangement, characterized by enhanced hepatic steatosis from increased de novo lipogenesis and uptake, as well as decreased hydrolysis and export of fatty acids. Steatosis in Bcl-3^Hep mice was accompanied by an augmented inflammatory milieu and liver cell injury. Moreover, Bcl-3 expression decreased insulin sensitivity and resulted in compensatory regulation of insulin-signaling pathways. Based on in vivo and in vitro studies we identified the transcription factors PPARα, PPARγ and PGC-1α as critical regulators of hepatic metabolism and inflammation downstream of Bcl-3. Metformin treatment improved the metabolic and inflammatory phenotype in Bcl-3^Hep mice through modulation of PPARα and PGC-1α. Remarkably, these findings were recapitulated in human NASH, which exhibited increased expression and nuclear localization of Bcl-3.

CONCLUSIONS

In summary, Bcl-3 emerges as a novel regulator of hepatic steatosis, insulin sensitivity and inflammation in NASH.

LAY SUMMARY

Non-alcoholic fatty liver disease (NAFLD) is considered the most prevalent liver disease worldwide. Patients can develop end-stage liver disease resulting in liver cirrhosis or hepatocellular carcinoma, but also develop complications unrelated to liver disease, e.g., cardiovascular disease. Still there is no full understanding of the mechanisms that cause NAFLD. In this study, genetically engineered mice were employed to examine the role of a specific protein in the liver that is involved in inflammation and the metabolism, namely Bcl-3. By this approach, a better understanding of the mechanisms contributing to disease progression was established. This can help to develop novel therapeutic and diagnostic options for patients with NAFLD.

Capture Hi-C identifies a novel causal gene, IL20RA, in the pan-autoimmune genetic susceptibility region 6q23

BACKGROUND

The identification of causal genes from genome-wide association studies (GWAS) is the next important step for the translation of genetic findings into biologically meaningful mechanisms of disease and potential therapeutic targets. Using novel chromatin interaction detection techniques and allele specific assays in T and B cell lines, we provide compelling evidence that redefines causal genes at the 6q23 locus, one of the most important loci that confers autoimmunity risk.

RESULTS

Although the function of disease-associated non-coding single nucleotide polymorphisms (SNPs) at 6q23 is unknown, the association is generally assigned to TNFAIP3, the closest gene. However, the DNA fragment containing the associated SNPs interacts through chromatin looping not only with TNFAIP3, but also with IL20RA, located 680 kb upstream. The risk allele of the most likely causal SNP, rs6927172, is correlated with both a higher frequency of interactions and increased expression of IL20RA, along with a stronger binding of both the NFκB transcription factor and chromatin marks characteristic of active enhancers in T-cells.

CONCLUSIONS

Our results highlight the importance of gene assignment for translating GWAS findings into biologically meaningful mechanisms of disease and potential therapeutic targets; indeed, monoclonal antibody therapy targeting IL-20 is effective in the treatment of rheumatoid arthritis and psoriasis, both with strong GWAS associations to this region.

BCL3 exerts an oncogenic function by regulating STAT3 in human cervical cancer

Aberrant expression of oncogenes and/or tumor suppressors play a fundamental effect on the pathogenesis and tumorigenicity of cervical cancer (CC). B-cell CLL/lymphoma 3 (BCL3) was previously found to be a putative proto-oncogene in human cancers and regulated signal transducer and activator of transcription 3 (STAT3), a critical oncogene, in CC cell line. However, its expression status, clinical significance and biological functions in CC remain largely unclear. The expressions of BCL3 and STAT3 in CC specimens were determined by immunohistochemistry. MTT, colony formation assays and flow cytometry analysis were carried out to test proliferation and cell cycle of CC cells. Here, the levels of BCL3 were overexpressed in CC compared to adjacent cervical tissues. Furthermore, high levels of BCL3 protein were confirmed by immunoblotting in CC cells as compared with normal cervical epithelial cells. The positive expression of BCL3 was correlated with adverse prognostic features and reduced survival rate. In addition, BCL3 regulated STAT3 abundance in CC cells. STAT3 was found to be upregulated and positively correlated with BCL3 expression in CC specimens. BCL3 overexpression resulted in prominent increased proliferation and cell cycle progression in Hela cells. By contrast, inhibition of BCL3 in CaSki cells remarkably suppressed proliferative ability and cell cycle progression. In vivo studies showed that knockdown of BCL3 inhibited tumor growth of CC in mice xenograft model. Notably, we confirmed that STAT3 mediated the oncogenic roles of BCL3 in CC. In conclusion, we suggest that BCL3 serves as an oncogene in CC by modulating proliferation and cell cycle progression, and its oncogenic effect is mediated by its downstream target gene, STAT3.

B-cell CLL/lymphoma 3 promotes glioma cell proliferation and inhibits apoptosis through the oncogenic STAT3 pathway

Aberrant expression of oncogenes and/or tumor suppressors play fundamental roles in the pathogenesis of glioma. B-cell CLL/lymphoma 3 (BCL3) was previously found to be a putative proto-oncogene in human cancers and the decoy receptor DcR1 is induced in a p50/Bcl3-dependent manner and attenuates the efficacy of temozolomide in glioblastoma cells. However, its expression status, clinical significance and biological functions in glioma remain largely unknown. In the present study, the levels of BCL3 were overexpressed in glioma compared to normal brain tissues. Furthermore, high expression of BCL3 protein was confirmed by immunoblotting in glioma cells as compared with normal human astrocyte cell line. The positive expression of BCL3 was correlated with adverse prognostic features and reduced overall survival rate of glioma patients. BCL3 silencing resulted in prominent decreased proliferation, cell cycle arrest in G1 phase and increased apoptosis in U251 cells. In contrast, BCL3 overexpression in U87 cells remarkably facilitated proliferative ability and cell cycle progression and induced apoptosis. In vivo studies showed that BCL3 knockdown inhibited the tumor growth of U251 cells in a mouse xenograft model. Mechanistically, BCL3 positively regulated the abundance of STAT3, p-STAT3 and the downstream targets of STAT3 pathway including BCL2, MCL-1 and cyclin D1 in glioma cells. Furthermore, a positive correlation between BCL3 and STAT3 expression was observed in glioma specimens. Notably, we confirmed that STAT3 knockdown abolished the oncogenic roles of BCL3 in glioma. In conclusion, we suggest that BCL3 serves as an oncogene in glioma by modulating proliferation, cell cycle progression and apoptosis, and its oncogenic effects are mediated by the STAT3 signaling pathway.

IκB-ζ, a new anti-inflammatory nuclear protein induced by lipopolysaccharide, is a negative regulator for nuclear factor-κB

Activation of nuclear factor-κ B (NF-κ B), a prominent cellular response to bacterial endotoxin or other microbial products, must be strictly regulated because excessive activation leads to overproduction of cytotoxic cytokines that culminates in septic shock. During screening for genes up-regulated upon inflammation, we identified a new member of the IκB family proteins with the ankyrin-repeats. This protein, designated Iκ B-ζ , is hardly detectable in resting cells, but is strongly induced upon stimulation by lipopolysaccharide, which stimulates cells through the Toll-like receptor 4. Interleukin-1β stimulation also results in the strong induction of IκB-ζ, but tumor necrosis factor-α does not. In contrast to IκB-α or Iκ B-β , IκB-ζ localizes in the nucleus, where it inhibits NF-κB activity. NF-κ B activity is essential for the induction of IκB-ζ, but is not sufficient. Thus, this protein is a new anti-inflammatory protein, which is specifically induced upon inflammation to regulate NF-κB activity.

MicroRNA-19b inhibits proliferation of gastric cancer cells by targeting B-cell CLL/lymphoma 3

Previous studies reported that the aberrant expression of miR-19b in gastric cancer tissues and circulating miR-19b is a potential biomarker to indicate progression of gastric cancer. However, the prognostic significance of miR-19b, and its role and underlying mechanisms in gastric cancer remain poorly investigated. In the present study, we demonstrated that the expression of miR-19b was aberrantly downregulated in both gastric cancer tissues and cell lines. Clinical association analyses disclosed that the reduced expression of miR-19b was significantly associated with adverse clinicopathological characteristics including poor differentiation, large tumor size and advanced tumor-node-metastasis (TNM) stage. Gastric cancer patients with low expression of miR-19b had prominent shorter overall survival and disease-free survival. Gain-of-function studies indicated that miR-19b overexpression inhibited cell proliferation and cell cycle progression in MGC-803 cells. While miR-19b silencing promoted cell proliferation and cell cycle progression in SGC-7901 cells. Furthermore, in vivo experiments showed that miR-19b overexpression suppressed the tumor growth of MGC-803 cells. Notably, miR-19b inversely regulated B-cell CLL/lymphoma 3 (BCL3) abundance in gastric cancer cells. BCL3 was identified as a direct target of miR-19b using luciferase reporter assays. Moreover, BCL3 knockdown abolished the effects of miR-19b knockdown on gastric cancer cells. In conclusion, our data suggest that miR-19b may potentially serve as a novel prognostic biomarker and therapeutic target for gastric cancer.

The Nuclear Protein IκBζ Forms a Transcriptionally Active Complex with Nuclear Factor-κB (NF-κB) p50 and the Lcn2 Promoter via the N- and C-terminal Ankyrin Repeat Motifs

The nuclear protein IκBζ, comprising the N-terminal trans-activation domain and the C-terminal ankyrin repeat (ANK) domain composed of seven ANK motifs, activates transcription of a subset of nuclear factor-κB (NF-κB)-dependent innate immune genes such as Lcn2 encoding the antibacterial protein lipocalin-2. Lcn2 activation requires formation of a complex containing IκBζ and NF-κB p50, a transcription factor that harbors the DNA-binding Rel homology region but lacks a trans-activation domain, on the promoter with the canonical NF-κB-binding site (κB site) and its downstream cytosine-rich element. Here we show that IκBζ productively interacts with p50 via Asp-451 in the N terminus of ANK1, a residue that is evolutionarily conserved among IκBζ and the related nuclear IκB proteins Bcl-3 and IκBNS Threonine substitution for Asp-451 abrogates direct association with the κB-site-binding protein p50, complex formation with the Lcn2 promoter DNA, and activation of Lcn2 transcription. The basic residues Lys-717 and Lys-719 in the C-terminal region of ANK7 contribute to IκBζ binding to the Lcn2 promoter, probably via interaction with the cytosine-rich element required for Lcn2 activation; glutamate substitution for both lysines results in a loss of transcriptionally active complex formation without affecting direct contact of IκBζ with p50. Both termini of the ANK domain in Bcl-3 and IκBNS function in a manner similar to that of IκBζ to interact with promoter DNA, indicating a common mechanism in which the nuclear IκBs form a regulatory complex with NF-κB and promoter DNA via the invariant aspartate in ANK1 and the conserved basic residues in ANK7.

Hepatic B cell leukemia-3 suppresses chemically-induced hepatocarcinogenesis in mice through altered MAPK and NF-κB activation

The transcriptional nuclear factor kappa B (NF-κB)-coactivator B cell leukemia-3 (Bcl-3) is a molecular regulator of cell death and proliferation. Bcl-3 has been shown to be widely expressed in different cancer types including hepatocellular carcinoma (HCC). Its influence on hepatocarcinogenesis is still undetermined. To examine the role of Bcl-3 in hepatocarcinogenesis mice with hepatocyte-specific overexpression of Bcl-3 (Bcl-3^Hep) were exposed to diethylnitrosamine (DEN) and phenobarbital (PB). Hepatic Bcl-3 overexpression attenuated DEN/PB-induced hepatocarcinogenesis. Bcl-3^Hep mice exhibited a lower number and smaller tumor nodules in response to DEN/PB at 40 weeks of age. Reduced HCC formation was accompanied by a lower rate of cell proliferation and a distinct expression pattern of growth and differentiation-related genes. Activation of c-Jun N-terminal kinase (JNK) and especially extracellular-signal regulated kinase (ERK) was reduced in tumor and tumor-surrounding liver tissue of Bcl-3^Hep mice, while p38 and NF-κB p65 were phosphorylated to a higher extent compared to the wild type. In parallel, the absolute number of intrahepatic macrophages, CD8⁺ T cells and activated B cells was reduced in DEN/PB-treated Bcl-3^Hep mice mirroring a reduction of tumor-associated inflammation. Interestingly, at the early time point of 7 weeks following tumor initiation, a higher rate of apoptotic cell death was observed in Bcl-3^Hep mice. In summary, hepatocyte-restricted Bcl-3 overexpression reduced hepatocarcinogenesis related to prolonged liver injury early after tumor initiation likely due to decreased survival of DEN/PB-damaged, premalignant cells. Therefore, Bcl-3 could become a novel player in the development of therapeutic and diagnostic tools for HCC.

BCL-3 expression promotes colorectal tumorigenesis through activation of AKT signalling

OBJECTIVE

Colorectal cancer remains the fourth most common cause of cancer-related mortality worldwide. Here we investigate the role of nuclear factor-κB (NF-κB) co-factor B-cell CLL/lymphoma 3 (BCL-3) in promoting colorectal tumour cell survival.

DESIGN

Immunohistochemistry was carried out on 47 tumour samples and normal tissue from resection margins. The role of BCL-3/NF-κB complexes on cell growth was studied in vivo and in vitro using an siRNA approach and exogenous BCL-3 expression in colorectal adenoma and carcinoma cells. The question whether BCL-3 activated the AKT/protein kinase B (PKB) pathway in colorectal tumour cells was addressed by western blotting and confocal microscopy, and the ability of 5-aminosalicylic acid (5-ASA) to suppress BCL-3 expression was also investigated.

RESULTS

We report increased BCL-3 expression in human colorectal cancers and demonstrate that BCL-3 expression promotes tumour cell survival in vitro and tumour growth in mouse xenografts in vivo, dependent on interaction with NF-κB p50 or p52 homodimers. We show that BCL-3 promotes cell survival under conditions relevant to the tumour microenvironment, protecting both colorectal adenoma and carcinoma cells from apoptosis via activation of the AKT survival pathway: AKT activation is mediated via both PI3K and mammalian target of rapamycin (mTOR) pathways, leading to phosphorylation of downstream targets GSK-3β and FoxO1/3a. Treatment with 5-ASA suppressed BCL-3 expression in colorectal cancer cells.

CONCLUSIONS

Our study helps to unravel the mechanism by which BCL-3 is linked to poor prognosis in colorectal cancer; we suggest that targeting BCL-3 activity represents an exciting therapeutic opportunity potentially increasing the sensitivity of tumour cells to conventional therapy.

Immunoglobulin gene translocations in chronic lymphocytic leukemia: A report of 35 patients and review of the literature

Chronic lymphocytic leukemia (CLL) represents the most common hematological malignancy in Western countries, with a highly heterogeneous clinical course and prognosis. Translocations involving the immunoglobulin (IG) genes are regularly identified. From 2000 to 2014, we identified an IG gene translocation in 18 of the 396 patients investigated at diagnosis (4.6%) and in 17 of the 275 analyzed during follow-up (6.2%). A total of 4 patients in whom the IG translocation was identified at follow-up did not carry the translocation at diagnosis. The IG heavy locus (IGH) was involved in 27 translocations (77.1%), the IG κ locus (IGK) in 1 (2.9%) and the IG λ locus (IGL) in 7 (20.0%). The chromosome band partners of the IG translocations were 18q21 in 16 cases (45.7%), 11q13 and 19q13 in 4 cases each (11.4% each), 8q24 in 3 cases (8.6%), 7q21 in 2 cases (5.7%), whereas 6 other bands were involved once (2.9% each). At present, 35 partner chromosomal bands have been described, but the partner gene has solely been identified in 10 translocations. CLL associated with IG gene translocations is characterized by atypical cell morphology, including plasmacytoid characteristics, and the propensity of being enriched in prolymphocytes. The IG heavy chain variable region (IGHV) mutational status varies between translocations, those with unmutated IGHV presumably involving cells at an earlier stage of B-cell lineage. All the partner genes thus far identified are involved in the control of cell proliferation and/or apoptosis. The translocated partner gene becomes transcriptionally deregulated as a consequence of its transposition into the IG locus. With the exception of t(14;18)(q32;q21) and its variants, prognosis appears to be poor for the other translocations. Therefore, searching for translocations involving not only IGH, but also IGL and IGK, by banding and molecular cytogenetics is required. Furthermore, it is important to identify the partner gene to ensure the patients receive the optimal treatment.

Functional activity of the porcine Gnrhr2 gene promoter in testis-derived cells is partially conferred by nuclear factor-κB, specificity protein 1 and 3 (SP1/3) and overlapping early growth response 1/SP1/3 binding sites

Unlike the classical gonadotropin-releasing hormone (GnRH1), the second mammalian isoform (GnRH2) is ubiquitously expressed, suggesting a divergent function. Indeed, we demonstrated that GnRH2 governs LH-independent testosterone secretion in porcine testes via interaction with its receptor (GnRHR2) on Leydig cells. Transient transfections with luciferase reporter vectors containing 3009bp of 5' flanking sequence for the porcine Gnrhr2 gene (-3009pGL3) revealed promoter activity in all 15 cell lines examined, including swine testis-derived (ST) cells. Therefore, ST cells were utilized to explore the molecular mechanisms underlying transcriptional regulation of the porcine Gnrhr2 gene in the testis. Reporter plasmids containing progressive 5' deletions of the Gnrhr2 promoter indicated that the -708/-490 region contained elements critical to promoter activity. Electrophoretic mobility shift assays (EMSAs) with radiolabeled oligonucleotides spanning the -708/-490bp region and ST nuclear extracts, identified specific binding complexes for the -513/-490, -591/-571 and -606/-581bp segments of promoter. Antibody addition to EMSAs indicated that the p65 and p52 subunits of nuclear factor-κB (NF-κB) comprised the specific complex bound to the oligonucleotide probe for the -513/-490bp promoter region, specificity protein (SP) 1 and 3 bound the -591/-571bp probe and early growth response 1 (EGR1), SP1 and SP3 bound the -606/-581 radiolabeled oligonucleotide. Transient transfections with vectors containing mutations of the NF-κB (-499/-493), SP1/3 (-582/-575) or overlapping EGR1/SP1/3 (-597/-587) binding sites reduced luciferase activity by 26%, 61% and 56%, respectively (P<0.05). Thus, NF-κB, SP1/3 and overlapping EGR1/SP1/3 binding sites are critical to expression of the porcine Gnrhr2 gene in ST cells.

Regulation of the Adaptive Immune Response by the IκB Family Protein Bcl-3

Bcl-3 is a member of the IκB family of proteins and an important regulator of Nuclear Factor (NF)-κB activity. The ability of Bcl-3 to bind and regulate specific NF-κB dimers has been studied in great depth, but its physiological roles in vivo are still not fully understood. It is, however, becoming clear that Bcl-3 is essential for the proper development, survival and activity of adaptive immune cells. Bcl-3 dysregulation can be observed in a number of autoimmune pathologies, and Bcl3-deficient animals are more susceptible to bacterial and parasitic infection. This review will describe our current understanding of the roles played by Bcl-3 in the development and regulation of the adaptive immune response, including lymphoid organogenesis, immune tolerance, lymphocyte function and dendritic cell biology.

BCL-3 promotes the tumor growth of hepatocellular carcinoma by regulating cell proliferation and the cell cycle through cyclin D1

Previous studies have demonstrated the aberrant expression and oncogenic role of B-cell CLL/lymphoma-3 (BCL-3) in human malignancies. However, the clinical significance of BCL-3 and its biological function in human hepatocellular carcinoma (HCC) remain unknown. In the present study, the expression levels of BCL-3 protein and mRNA in 90 pairs of HCC and matched non-tumor tissues were analyzed using immunohistochemistry and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). We found that the expression levels of BCL-3 protein and mRNA in HCC tissues were significantly higher than those in the matched tumor-adjacent tissues. In addition, positive expression of BCL-3 was associated with adverse clinicopathological characteristics of the HCC patients including hepatitis B virus (HBV) infection, tumor size, cirrhosis and advanced tumor-node-metastasis (TNM) stage. Moreover, HCC patients with positive expression of BCL-3 had significantly decreased 5-year overall survival and recurrence-free survival. Importantly, BCL-3 expression was an independent prognostic factor for indicating the survival of the HCC patients. Functionally, BCL-3 knockdown markedly inhibited cell viability, proliferation and cell cycle progression in HepG2 cells, while BCL-3 overexpression promoted these cellular processes in Huh7 cells. Accordingly, in vivo experiments indicated that BCL-3 knockdown prominently suppressed the tumor growth of HepG2 cells in nude mice. Mechanistically, we revealed that the expression of cyclin D1 was decreased after BCL-3 knockdown in the HepG2 cells and was increased after BCL-3 overexpression in the Huh7 cells. Cyclin D1 silencing was found to abrogate the functional effects of BCL-3 on cellular processes in Huh7 cells. Taken together, our data suggest that BCL-3 may serve as a promising biomarker and an effective therapeutic target of HCC.

BCL3 Reduces the Sterile Inflammatory Response in Pancreatic and Biliary Tissues

BACKGROUND & AIMS

Under conditions of inflammation in the absence of micro-organisms (sterile inflammation), necrotic cells release damage-associated molecular patterns that bind to Toll-like receptors on immune cells to activate a signaling pathway that involves activation of IκB kinase and nuclear factor κB (NF-κB). Little is known about the mechanisms that control NF-κB activity during sterile inflammation. We analyzed the contribution of B-cell CLL/lymphoma 3 (BCL3), a transcription factor that associates with NF-κB, in control of sterile inflammation in the pancreas and biliary system of mice.

METHODS

Acute pancreatitis (AP) was induced in C57BL/6 (control) and Bcl3(-/-) mice by intraperitoneal injection of cerulein or pancreatic infusion of sodium taurocholate. We also studied Mdr2(-/-) mice, which develop spontaneous biliary inflammation, as well as Bcl3(-/-)Mdr2(-/-) mice. We performed immunohistochemical analyses of inflamed and noninflamed regions of pancreatic tissue from patients with AP or primary sclerosing cholangitis (PSC), as well as from mice. Immune cells were characterized by fluorescence-activated cell sorting analysis. Control or Bcl3(-/-) mice were irradiated, injected with bone marrow from Bcl3(-/-) or control mice, and AP was induced.

RESULTS

Pancreatic or biliary tissues from patients with AP or PSC had higher levels of BCL3 and phosphorylated RelA and IκBα in inflamed vs noninflamed regions. Levels of BCL3 were higher in pancreata from control mice given cerulein than from mice without AP, and were higher in biliary tissues from Mdr2(-/-) mice than from control mice. Bcl3(-/-) mice developed more severe AP after administration of cerulein or sodium taurocholate than control mice; pancreata from the Bcl3(-/-) mice with AP had greater numbers of macrophages, myeloid-derived suppressor cells, dendritic cells, and granulocytes than control mice with AP. Activation of NF-κB was significantly prolonged in Bcl3(-/-) mice with AP, compared with control mice with AP. Bcl3(-/-)Mdr2(-/-) mice developed more severe cholestasis and had increased markers of liver injury and increased proliferation of biliary epithelial cells and hepatocytes than Mdr2(-/-) mice. In experiments with bone marrow chimeras, expression of BCL3 by acinar cells, but not myeloid cells, was required for reduction of inflammation during development of AP. BCL3 inhibited ubiquitination and proteasome-mediated degradation of p50 homodimers, which prolonged binding of NF-κB heterodimers to DNA.

CONCLUSIONS

BCL3 is up-regulated in inflamed pancreatic or biliary tissues from mice and patients with AP or cholangitis. Its production appears to reduce the inflammatory response in these tissues via blocking ubiquitination and proteasome-mediated degradation of p50 homodimers.

Natural Agents Used in Chemoprevention of Aerodigestive and GI Cancers

Aerodigestive cancers are on an increasing level in both occurrence and mortality. A major cause in many of these cancers is disruption of the inflammatory pathway, leading to increased cell proliferation, and epigenetic silencing of normal regulatory genes. Here we review the research on several natural products: silibinin, silymarin, quercetin, neem & nimbolide, gingerol, epigallatecatechin-3- gallate, curcumin, genistein and resveratrol conducted on aerodigestive cancers. These types of cancers are primarily those from oral cavity, esophagus/windpipe, stomach, small and large intestine, colon/rectum and bile/pancreas tissues. We report on the utilization in vivo and in vitro systems to research these dose effects on the inflammatory and epigenetic pathway components within the aerodigestive cancer. To follow up on the basic research we will discuss remaining research questions and future directions involving these natural products as putative stand alone or in combination with clinical agents.

NF-κB in inflammation and renal diseases

Nuclear factor κB (NF-κB) is a family of inducible transcription factors that plays a vital role in different aspects of immune responses. NF-κB is normally sequestered in the cytoplasm as inactive complexes via physical association with inhibitory proteins termed IκBs. In response to immune and stress stimuli, NF-κB members become activated via two major signaling pathways, the canonical and noncanonical pathways, and move to the nucleus to exert transcriptional functions. NF-κB is vital for normal immune responses against infections, but deregulated NF-κB activation is a major cause of inflammatory diseases. Accumulated studies suggest the involvement of NF-κB in the pathogenesis of renal inflammation caused by infection, injury, or autoimmune factors. In this review, we discuss the current understanding regarding the activation and function of NF-κB in different types of kidney diseases.

Variant of BCL3 gene is strongly associated with five-year survival of non-small-cell lung cancer patients

OBJECTIVES

BCL3, a known atypical IκB family member, has been documented to be upregulated in hematological malignancies and in some solid tumors, functioning as a crucial player in tumor development. Recently, rs8100239, a tag-Single Nucleotide Polymorphism (SNP) in BCL3 (T>A) has been identified, but there are no data regarding its involvement in non-small-cell lung cancer (NSCLC) initiation and progression.

MATERIALS AND METHODS

To study the possible association of BCL3 with NSCLC, 268 patients and 279 healthy controls were genotyped for rs8100239. Moreover, BCL3 protein expression was also investigated in 112 NSCLC cases through an immunohistochemical analysis.

RESULTS

NSCLC patients with AA genotype displayed significantly worse prognosis compared to T allele carriers (P<0.001), who had less frequent intermediate nuclear BCL3 expression (P=0.042). In addition, overexpression of BCL3 was detected in tumor specimens, compared to normal tissue (P<0.001). Furthermore, BCL3 protein levels were associated with five-year survival (P=0.039), maximum diameter of lesion (P=0.012), grade (P=0.002) and relapse frequency (P=0.041).

CONCLUSIONS

The present study is the first to show a relationship between the genetic variation rs8100239 of BCL3 and cancer patients' survival. It also represents the first quantitative evaluation of BCL3 expression in NSCLC. Our findings indicate that rs8100239 may be considered as a novel prognostic indicator, demonstrating also the overexpression of BCL3 protein in NSCLC and implicating this pivotal molecule in the pathogenesis of NSCLC.

Early diagnostic value of Bcl-3 localization in colorectal cancer

Background

B-cell leukemia 3 (Bcl-3) is a member of the inhibitor of κB family, which regulates a wide range of biological processes by functioning as a transcriptional activator or as a repressor of target genes. Elevated expression, sustained nuclear accumulation, and uncontrolled activation of Bcl-3 causes increased cellular proliferation or survival, dependent on the tissue and type of stimuli.

Methods

We retrospectively reviewed patients who were diagnosed with colorectal cancer at Skåne University Hospital in Malmö between 1st of January 1990 and 31st of December 1991. Bcl-3 localization in colorectal cancer was assessed by immunohistochemistry on tissue microarray and freshly isolated colon from patients. Correlation between Bcl-3 localization and clinicopathological parameters of the cohort were evaluated using the Spearman rank-order correlation coefficient. In addition, Bcl-3 expression and localization in colon adenocarcinoma cells were analysed by western blot, immunohistochemistry and subcellular fractionation separately.

Results

We found that Bcl-3 was mainly localized in the cytoplasm in the tumour tissue isolated from colon cancer patients. Normal colon samples from the same patients showed Bcl-3 localization in the nucleus. In three out of six colon cancer cell lines, we detected elevated levels of Bcl-3. In these cell lines Bcl-3 was accumulated in the cytosol. We confirmed these findings by analysing Bcl-3 localization in a colon tissue micro array consisting of 270 cases. In these samples Bcl-3 localization correlated with the proliferation marker Ki-67, but not with the apoptotic marker Caspase 3.

Conclusion

These findings indicate that analysis of the subcellular localization of Bcl-3 could be a potential-early diagnostic marker in colon cancer.

The transcriptional PPARβ/δ network in human macrophages defines a unique agonist-induced activation state

Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) is a lipid ligand-inducible transcription factor with established metabolic functions, whereas its anti-inflammatory function is poorly understood. To address this issue, we determined the global PPARβ/δ-regulated signaling network in human monocyte-derived macrophages. Besides cell type-independent, canonical target genes with metabolic and immune regulatory functions we identified a large number of inflammation-associated NFκB and STAT1 target genes that are repressed by agonists. Accordingly, PPARβ/δ agonists inhibited the expression of multiple pro-inflammatory mediators and induced an anti-inflammatory, IL-4-like morphological phenotype. Surprisingly, bioinformatic analyses also identified immune stimulatory effects. Consistent with this prediction, PPARβ/δ agonists enhanced macrophage survival under hypoxic stress and stimulated CD8⁺ T cell activation, concomitantly with the repression of immune suppressive target genes and their encoded products CD274 (PD-1 ligand), CD32B (inhibitory Fcγ receptor IIB) and indoleamine 2,3-dioxygenase 1 (IDO-1), as well as a diminished release of the immune suppressive IDO-1 metabolite kynurenine. Comparison with published data revealed a significant overlap of the PPARβ/δ transcriptome with coexpression modules characteristic of both anti-inflammatory and pro-inflammatory cytokines. Our findings indicate that PPARβ/δ agonists induce a unique macrophage activation state with strong anti-inflammatory but also specific immune stimulatory components, pointing to a context-dependent function of PPARβ/δ in immune regulation.

Gene expression network analysis reveals new transcriptional regulators as novel factors in human ischemic cardiomyopathy

BACKGROUND

Ischemic cardiomyopathy (ICM) is characterized by transcriptomic changes that alter cellular processes leading to decreased cardiac output. Because the molecular network of ICM is largely unknown, the aim of this study was to characterize the role of new transcriptional regulators in the molecular mechanisms underlying the responses to ischemia.

METHODS

Myocardial tissue explants from ICM patients and control (CNT) subjects were analyzed by RNA-Sequencing (RNA-Seq) and quantitative Real-Time PCR.

RESULTS

Enrichment analysis of the ICM transcriptomic profile allowed the characterization of novel master regulators. We found that the expression of the transcriptional regulators SP100 (-1.5-fold, p < 0.05), CITED2 (-3.8-fold, p < 0.05), CEBPD (-4.9-fold, p < 0.05) and BCL3 (-3.3-fold, p < 0.05) were lower in ICM than in CNT. To gain insights into the molecular network defined by the transcription factors, we identified CEBPD, BCL3, and HIF1A target genes in the RNA-Seq datasets. We further characterized the biological processes of the target genes by gene ontology annotation. Our results suggest that CEBPD-inducible genes with roles in the inhibition of apoptosis are downregulated and that BCL3-repressible genes are involved in the regulation of cellular metabolism in ICM. Moreover, our results suggest that CITED2 downregulation causes increased expression of HIF1A target genes. Functional analysis of HIF1A target genes revealed that hypoxic and stress response genes are activated in ICM. Finally, we found a significant correlation between the mRNA levels of BCL3 and the mRNA levels of both CEBPD (r = 0.73, p < 0.001) and CITED2 (r = 0.56, p < 0.05). Interestingly, CITED2 mRNA levels are directly related to ejection fraction (EF) (r = 0.54, p < 0.05).

CONCLUSIONS

Our data indicate that changes in the expression of SP100, CITED2, CEBPD, and BCL3 affect their transcription regulatory networks, which subsequently alter a number of biological processes in ICM patients. The relationship between CITED2 mRNA levels and EF emphasizes the importance of this transcription factor in ICM. Moreover, our findings identify new mechanisms used to interpret gene expression changes in ICM and provide valuable resources for further investigation of the molecular basis of human cardiac ischemic response.

Bcl-3 puts the brakes on contact hypersensitivity

B-cell lymphoma (Bcl)-3 is a nonclassical member of the IκB protein family known to interact with transcriptionally inactive NF-κB1 and NF-κB2 homodimers to modulate gene expression. Besides its action as an oncoprotein, Bcl-3 has been shown to have both proinflammatory and anti-inflammatory functions depending on the cell-type affected. In this issue of the European Journal of Immunology, Tassi et al. [Eur. J. Immunol. 2015. 45: 1059-1068] report that Bcl-3 inhibits the production of the proinflammatory chemokines CXCL9 and CXCL10 in keratinocytes, thereby restricting the influx of CD8(+) effector T cells in a mouse model of allergic contact dermatitis. In addition, mice with a global deficiency of Bcl-3 show enhanced ear swelling responses in the late phase of contact hypersensitivity responses. Besides keratinocytes, other radioresistant cell types appear to also utilize Bcl-3 to dampen the inflammatory response. This Commentary will discuss the evidence supporting Bcl-3 as a critical player in limiting inflammation during the later stages of contact hypersensitivity.

The oncoprotein and transcriptional regulator Bcl-3 governs plasticity and pathogenicity of autoimmune T cells

Bcl-3 is an atypical member of the IκB family that modulates transcription in the nucleus via association with p50 (NF-κB1) or p52 (NF-κB2) homodimers. Despite evidence attesting to the overall physiologic importance of Bcl-3, little is known about its cell-specific functions or mechanisms. Here we demonstrate a T-cell-intrinsic function of Bcl-3 in autoimmunity. Bcl-3-deficient T cells failed to induce disease in T cell transfer-induced colitis and experimental autoimmune encephalomyelitis. The protection against disease correlated with a decrease in Th1 cells that produced the cytokines IFN-γ and GM-CSF and an increase in Th17 cells. Although differentiation into Th1 cells was not impaired in the absence of Bcl-3, differentiated Th1 cells converted to less-pathogenic Th17-like cells, in part via mechanisms involving expression of the RORγt transcription factor. Thus, Bcl-3 constrained Th1 cell plasticity and promoted pathogenicity by blocking conversion to Th17-like cells, revealing a unique type of regulation that shapes adaptive immunity.

Eight SNVs in NF-κB pathway genes and their different performances between subclinical mastitis and mixed Chinese Holstein cows

The nuclear factor-kappa B (NF-κB) pathway proteins are key players in controlling both innate and adaptive immunity. However, the information on NF-κB pathway genes is very limited in mastitis resistance and milk production of Chinese Holstein cows. In this study, we examine the association of the NF-κB pathway gene variants with milk quality traits and somatic cell score (SCS) in Chinese Holstein cows. Eight single nucleotide variants (SNVs) were identified within the bovine NF-κB pathway genes, using DNA pooled sequencing, PCR-RFLP, and forced PCR-RFLP methods. These SNVs include SNV1: g. 536 C>T (exon 10 of Rel), SNV2: g. 94 G>A (exon 20 of p100), SNV3: g. 43 T>C (intron 6 of p105), SNV4: g. 2397 T>G (intron 9 of p105), SNV5: g. 382 G>C (intron 1 of IκBδ), SNV6: g. 21 C>T (exon 5 of IκBζ), SNV7: g. 272 G>A (intron 6 of IκBζ), and SNV8: g. 18 C>T (intron 10 of IκBζ). The association analysis in mixed Chinese Holstein population showed that SNV1 was significantly or highly significantly associated (P<0.01 and P<0.05) with fat rate, protein rate and SCS. Furthermore, the SNV1-CC (wild genotype) determined serine showed the significantly lower SCS and higher milk production traits compared to TT and TC. SNV2 was significantly associated (P<0.05) with SCS; SNV3 was significantly associated (P<0.05) with fat rate; and SNV4 was significantly associated (P<0.05) with fat rate and SCS. In 199 subclinical mastitis Chinese Holstein cows, the statistical results absolutely differed from the mixed Chinese Holstein individuals. Splice-site prediction by SplicePort showed that single nucleotide difference at eight SNVs results in the acceptor score and donor score changing obviously that may lead to alternative splicing. In brief, SNV1, SNV2, SNV3 and SNV4 could be useful genetic markers for mastitis resistance selection and breeding in Chinese Holstein cows. Furthermore, whether these SNVs lead to alternative splicing need further research.

Bcl3 regulates pro-survival and pro-inflammatory gene expression in cutaneous T-cell lymphoma

The advanced stages of cutaneous T cell lymphoma (CTCL) are characterized not only by decreased levels of pro-inflammatory cytokines, resulting in high susceptibility to infections, but also by high constitutive activity of NFκB, which promotes cell survival and resistance to apoptosis. The increased expression of the proto-oncogene Bcl3 belonging to IκB family is associated with the pathogenesis of the different types of human cancer, yet, the function and regulation of Bcl3 in CTCL have not been studied. Here, we show that Bcl3 is highly expressed in CTCL Hut-78 and HH cells. The suppression of Bcl3 levels decreases the expression of the pro-survival genes cIAP1 and cIAP2, reduces cell viability, and increases CTCL apoptosis. Interestingly, Bcl3 suppression concomitantly increases expression and the release of the pro-inflammatory cytokines IL-8 and IL-17 in CTCL cells. Chromatin immunoprecipitation studies show that Bcl3 regulates cIAP1, cIAP2, IL-8 and IL-17 gene expression through direct binding to their promoters. Bcl3 expression is regulated by bortezomib (BZ)-mediated proteasome inhibition, and BZ inhibits Bcl3 recruitment to its target promoters, resulting in decreased expression of cIAP1 and cIAP2, but increased expression of IL-8 and IL-17. The Bcl3 expression is regulated through NFκB subunit exchange on Bcl3 promoter. In untreated cells, the Bcl3 promoter is occupied predominantly by p65/p50 heterodimers, inducing Bcl3 expression; however, in BZ-treated cells, the p65/50 heterodimers are replaced by p52 subunits, resulting in Bcl3 transcriptional repression. These data provide the first insights into the function and regulation of Bcl3 in CTCL, and indicate that Bcl3 has an important pro-survival and immunosuppressive role in these cells.

Expression differences of miRNAs and genes on NF-κB pathway between the healthy and the mastitis Chinese Holstein cows

In order to discover the variation of microRNAs and genes associated with NF-κB signaling pathway between the healthy and the mastitis Chinese Holstein cows, Illumina Deep Sequencing and qRT-PCR are applied to detect 25 kinds of miRNAs (miR-16, miR-125b, miR-15, miR-29a, miR-23b, miR-146, miR-301a, miR-181b, let-7, miR-30b, miR-21, miR-223, miR-27b, miR-10a, miR-143, etc.) expression levels in blood samples and 14 genes (RelA, RelB, Rel, p105, p100, IκBα, IκBβ, IκBδ, IκBε, IκBζ, Bcl-3, IKKα, IKKβ, IKKγ/NEMO) relative expression levels in nine tissues. The total number of miRNAs is declining, and RelA, Rel, p105, p100, IκBα, IκBβ, IκBδ, IκBζ, Bcl-3, and IKKα expressions are rising in mastitis individuals. So, we suppose that NF-κB pathway is active in mastitis individuals as a result of the decrease inhibition of miRNAs. While in healthy ones, the NF-κB pathway is inactive, because of the miRNAs enhanced inhibition action. However, the specific regulatory mechanism of miRNAs on NF-κB pathway in mastitis Holstein cows needs further investigation. Moreover, due to obvious expression differences, some miRNAs, especially miR-16 and miR-223, may be used as new markers for the dairy mastitis prognosing.

Ankrd2 is a modulator of NF-κB-mediated inflammatory responses during muscle differentiation

Adaptive responses of skeletal muscle regulate the nuclear shuttling of the sarcomeric protein Ankrd2 that can transduce different stimuli into specific adaptations by interacting with both structural and regulatory proteins. In a genome-wide expression study on Ankrd2-knockout or -overexpressing primary proliferating or differentiating myoblasts, we found an inverse correlation between Ankrd2 levels and the expression of proinflammatory genes and identified Ankrd2 as a potent repressor of inflammatory responses through direct interaction with the NF-κB repressor subunit p50. In particular, we identified Gsk3β as a novel direct target of the p50/Ankrd2 repressosome dimer and found that the recruitment of p50 by Ankrd2 is dependent on Akt2-mediated phosphorylation of Ankrd2 upon oxidative stress during myogenic differentiation. Surprisingly, the absence of Ankrd2 in slow muscle negatively affected the expression of cytokines and key calcineurin-dependent genes associated with the slow-twitch muscle program. Thus, our findings support a model in which alterations in Ankrd2 protein and phosphorylation levels modulate the balance between physiological and pathological inflammatory responses in muscle.

BCL-3 attenuation of TNFA expression involves an incoherent feed-forward loop regulated by chromatin structure

Induction of genes is rarely an isolated event; more typically occurring as part of a web of parallel interactions, or motifs, which act to refine and control gene expression. Here, we define an Incoherent Feed-forward Loop motif in which TNFα-induced NF-κB signalling activates expression of the TNFA gene itself and also controls synthesis of the negative regulator BCL-3. While sharing a common inductive signal, the two genes have distinct temporal expression profiles. Notably, while the TNFA gene promoter is primed to respond immediately to activated NF-κB in the nucleus, induction of BCL3 expression only occurs after a time delay of about 1h. We show that this time delay is defined by remodelling of the BCL3 gene promoter, which is required to activate gene expression, and characterise the chromatin delayed induction of BCL3 expression using mathematical models. The models show how a delay in inhibitor production effectively uncouples the rate of response to inflammatory cues from the final magnitude of inhibition. Hence, within this regulatory motif, a delayed (incoherent) feed-forward loop together with differential rates of TNFA (fast) and BCL3 (slow) mRNA turnover provide robust, pulsatile expression of TNFα . We propose that the structure of the BCL-3-dependent regulatory motif has a beneficial role in modulating expression dynamics and the inflammatory response while minimising the risk of pathological hyper-inflammation.

The complexity of NF-κB signaling in inflammation and cancer

The NF-κB family of transcription factors has an essential role in inflammation and innate immunity. Furthermore, NF-κB is increasingly recognized as a crucial player in many steps of cancer initiation and progression. During these latter processes NF-κB cooperates with multiple other signaling molecules and pathways. Prominent nodes of crosstalk are mediated by other transcription factors such as STAT3 and p53 or the ETS related gene ERG. These transcription factors either directly interact with NF-κB subunits or affect NF-κB target genes. Crosstalk can also occur through different kinases, such as GSK3-β, p38, or PI3K, which modulate NF-κB transcriptional activity or affect upstream signaling pathways. Other classes of molecules that act as nodes of crosstalk are reactive oxygen species and miRNAs. In this review, we provide an overview of the most relevant modes of crosstalk and cooperativity between NF-κB and other signaling molecules during inflammation and cancer.

Atypical IκB proteins - nuclear modulators of NF-κB signaling

Nuclear factor κB (NF-κB) controls a multitude of physiological processes such as cell differentiation, cytokine expression, survival and proliferation. Since NF-κB governs embryogenesis, tissue homeostasis and the functions of innate and adaptive immune cells it represents one of the most important and versatile signaling networks known. Its activity is regulated via the inhibitors of NF-κB signaling, the IκB proteins. Classical IκBs, like the prototypical protein IκBα, sequester NF-κB transcription factors in the cytoplasm by masking of their nuclear localization signals (NLS). Thus, binding of NF-κB to the DNA is inhibited. The accessibility of the NLS is controlled via the degradation of IκBα. Phosphorylation of the conserved serine residues 32 and 36 leads to polyubiquitination and subsequent proteasomal degradation. This process marks the central event of canonical NF-κB activation. Once their NLS is accessible, NF-κB transcription factors translocate into the nucleus, bind to the DNA and regulate the transcription of their respective target genes. Several studies described a distinct group of atypical IκB proteins, referred to as the BCL-3 subfamily. Those atypical IκBs show entirely different sub-cellular localizations, activation kinetics and an unexpected functional diversity. First of all, their interaction with NF-κB transcription factors takes place in the nucleus in contrast to classical IκBs, whose binding to NF-κB predominantly occurs in the cytoplasm. Secondly, atypical IκBs are strongly induced after NF-κB activation, for example by LPS and IL-1β stimulation or triggering of B cell and T cell antigen receptors, but are not degraded in the first place like their conventional relatives. Finally, the interaction of atypical IκBs with DNA-associated NF-κB transcription factors can further enhance or diminish their transcriptional activity. Thus, they do not exclusively act as inhibitors of NF-κB activity. The capacity to modulate NF-κB transcription either positively or negatively, represents their most important and unique mechanistic difference to classical IκBs. Several reports revealed the importance of atypical IκB proteins for immune homeostasis and the severe consequences following their loss of function. This review summarizes insights into the physiological processes regulated by this protein class and the relevance of atypical IκB functioning.

Evolutionary, structural and functional interplay of the IκB family members

A primary level of control for nuclear factor kappa B (NF-κB) is effected through its interactions with the inhibitor protein, inhibitor of kappa B (IκB). Several lines of evidence confirm the existence of multiple forms of IκB that appear to regulate NF-κB by distinct mechanisms. Therefore, we performed a comprehensive bioinformatics analysis to understand the evolutionary history and intrinsic functional diversity of IκB family members. Phylogenetic relationships were constructed to trace the evolution of the IκB family genes. Our phylogenetic analysis revealed 10 IκB subfamily members that clustered into 5 major clades. Since the ankyrin (ANK) domain appears to be more ancient than the Rel homology domain (RHD), our phylogenetic analysis suggests that some undefined ancestral set of ANK repeats acquired an RHD before any duplication and was later duplicated and then diverged into the different IκB subfamilies. Functional analysis identified several functionally divergent sites in the ANK repeat domains (ARDs) and revealed that this region has undergone strong purifying selection, suggesting its functional importance in IκB genes. Structural analysis showed that the major variations in the number of ANK repeats and high conformational changes in the finger loop ARD region contribute to the differing binding partner specificities, thereby leading to distinct IκB functions. In summary, our study has provided useful information about the phylogeny and structural and functional divergence of the IκB family. Additionally, we identified a number of amino acid sites that contribute to the predicted functional divergence of these proteins.

The ChIP-seq-defined networks of Bcl-3 gene binding support its required role in skeletal muscle atrophy

NF-kappaB transcriptional activation is required for skeletal muscle disuse atrophy. We are continuing to study how the activation of NF-kB regulates the genes that encode the protein products that cause atrophy. Using ChIP-sequencing we found that Bcl-3, an NF-kB transcriptional activator required for atrophy, binds to the promoters of a number of genes whose collective function describes two major aspects of muscle wasting. By means of bioinformatics analysis of ChIP-sequencing data we found Bcl-3 to be directing transcription networks of proteolysis and energy metabolism. The proteolytic arm of the Bcl-3 networks includes many E3 ligases associated with proteasomal protein degradation, including that of the N-end rule pathway. The metabolic arm appears to be involved in organizing the change from oxidative phosphorylation to glycolysis in atrophying muscle. For one gene, MuRF1, ChIP-sequencing data identified the location of Bcl-3 and p50 binding in the promoter region which directed the creation of deletant and base-substitution mutations of MuRF1 promoter constructs to determine the effect on gene transcription. The results provide the first direct confirmation that the NF-kB binding site is involved in the muscle unloading regulation of MuRF1. Finally, we have combined the ChIP-sequencing results with gene expression microarray data from unloaded muscle to map several direct targets of Bcl-3 that are transcription factors whose own targets describe a set of indirect targets for NF-kB in atrophy. ChIP-sequencing provides the first molecular explanation for the finding that Bcl3 knockout mice are resistant to disuse muscle atrophy. Mapping the transcriptional regulation of muscle atrophy requires an unbiased analysis of the whole genome, which we show is now possible with ChIP-sequencing.

Bcl3 selectively promotes metastasis of ERBB2-driven mammary tumors

Bcl3 is a putative proto-oncogene deregulated in hematopoietic and solid tumors. Studies in cell lines suggest that its oncogenic effects are mediated through the induction of proliferation and inhibition of cell death, yet its role in endogenous solid tumors has not been established. Here, we address the oncogenic effect of Bcl3 in vivo and describe how this Stat3-responsive oncogene promotes metastasis of ErbB2-positive mammary tumors without affecting primary tumor growth or normal mammary function. Deletion of the Bcl3 gene in ErbB2-positive (MMTV-Neu) mice resulted in a 75% reduction in metastatic tumor burden in the lungs with a 3.6-fold decrease in cell turnover index in these secondary lesions with no significant effect on primary mammary tumor growth, cyclin D1 levels, or caspase-3 activity. Direct inhibition of Bcl3 by siRNA in a transplantation model of an Erbb2-positive mammary tumor cell line confirmed the effect of Bcl3 in malignancy, suggesting that the effect of Bcl3 was intrinsic to the tumor cells. Bcl3 knockdown resulted in a 61% decrease in tumor cell motility and a concomitant increase in the cell migration inhibitors Nme1, Nme2, and Nme3, the GDP dissociation inhibitor Arhgdib, and the metalloprotease inhibitors Timp1 and Timp2. Independent knockdown of Nme1, Nme2, and Arhgdib partially rescued the Bcl3 motility phenotype. These results indicate for the first time a cell-autonomous disease-modifying role for Bcl3 in vivo, affecting metastatic disease progression rather than primary tumor growth.

Bcl-3 suppresses Tax-induced NF-κB activation through p65 nuclear translocation blockage in HTLV-1-infected cells

Human T cell leukemia virus type 1 (HTLV-1) Tax-induced persistent activation of the NF-κB pathway is perceived as the primary cause of adult T cell leukemia (ATL), an aggressive leukemia caused by HTLV-1. Although elevated oncoprotein Bcl-3 levels are found in many HTLV-1-infected T cell lines and ATL cells, the role of Bcl-3 in the malignant progression caused by HTLV-1 retrovirus remains poorly understood. We confirmed, in the present study, that the Tax-induced NF-κB activation involves the regulation of Bcl-3. Both knockdown and overexpression of Bcl-3 inhibit the Tax-induced NF-κB activation. Similarly, excessive Bcl-3 inhibits the NF-κB/DNA binding activity and significantly decreases Tax-induced p65 nuclear translocation. The present results demonstrate the pleiotropic roles of Bcl-3 in Tax-induced NF-κB activation and indicate that a balance in the aberrant Bcl-3 expression may be established to play an important role in the maintenance of proliferation and inhibition of apoptosis in HTLV-1-infected and ATL cells.

The transcriptional specificity of NF-κB dimers is coded within the κB DNA response elements

Nuclear factor κB (NF-κB) regulates gene expression by binding to specific DNA elements, known collectively as κB sites, that are contained within the promoters/enhancers of target genes. We found that the identity of the central base pair (bp) of κB sites profoundly affects the transcriptional activity of NF-κB dimers. RelA dimers prefer an A/T bp at this position for optimal transcriptional activation (A/T-centric) and discriminate against G/C-centric κB sites. The p52 homodimer, in contrast, activates transcription from G/C-centric κB sites in complex with Bcl3 but represses transcription from the A/T-centric sites. The p52:Bcl3 complex binds to these two classes of κB sites in distinct modes, permitting the recruitment of coactivator, corepressor, or both coactivator and corepressor complexes in promoters that contain G/C-, A/T-, or both G/C- and A/T-centric sites. Therefore, through sensing of bp differences within κB sites, NF-κB dimers modulate biological programs by activating, repressing, and altering the expression of effector genes.

p100 Deficiency is insufficient for full activation of the alternative NF-κB pathway: TNF cooperates with p52-RelB in target gene transcription

Background

Constitutive activation of the alternative NF-κB pathway leads to marginal zone B cell expansion and disorganized spleen microarchitecture. Furthermore, uncontrolled alternative NF-κB signaling may result in the development and progression of cancer. Here, we focused on the question how does the constitutive alternative NF-κB signaling exert its effects in these malignant processes.

Methodology/Principal Findings

To explore the consequences of unrestricted alternative NF-κB activation on genome-wide transcription, we compared gene expression profiles of wild-type and NF-κB2/p100-deficient (p100^−/−) primary mouse embryonic fibroblasts (MEFs) and spleens. Microarray experiments revealed only 73 differentially regulated genes in p100^−/− vs. wild-type MEFs. Chromatin immunoprecipitation (ChIP) assays showed in p100^−/− MEFs direct binding of p52 and RelB to the promoter of the Enpp2 gene encoding ENPP2/Autotaxin, a protein with an important role in lymphocyte homing and cell migration. Gene ontology analysis revealed upregulation of genes with anti-apoptotic/proliferative activity (Enpp2/Atx, Serpina3g, Traf1, Rrad), chemotactic/locomotory activity (Enpp2/Atx, Ccl8), and lymphocyte homing activity (Enpp2/Atx, Cd34). Most importantly, biochemical and gene expression analyses of MEFs and spleen, respectively, indicated a marked crosstalk between classical and alternative NF-κB pathways.

Conclusions/Significance

Our results show that p100 deficiency alone was insufficient for full induction of genes regulated by the alternative NF-κB pathway. Moreover, alternative NF-κB signaling strongly synergized both in vitro and in vivo with classical NF-κB activation, thereby extending the number of genes under the control of the p100 inhibitor of the alternative NF-κB signaling pathway.

Nuclear factor-κB signalling and transcriptional regulation in skeletal muscle atrophy

The nuclear factor-κB (NF-κB) signalling pathway is a necessary component of adult skeletal muscle atrophy resulting from systemic illnesses or disuse. Studies showing a role for the NF-κB pathway in muscle disuse include unloading, denervation and immobilization, and studies showing a role for NF-κB in systemic illnesses include cancer, chronic heart failure and acute septic lung injury. Muscle atrophy due to most of these triggers is associated with activation of NF-κB transcriptional activity. With the exception of muscle unloading, however, there is a paucity of data on the NF-κB transcription factors that regulate muscle atrophy, and little is known about which genes are targeted by NF-κB transcription factors during atrophy. Interestingly, in some cases it appears that the amelioration of muscle atrophy by genetic inhibition of NF-κB signalling proteins is due to effects that are independent of the downstream NF-κB transcription factors. These questions are prime areas for investigation if we are to understand a key component of muscle wasting in adult skeletal muscle.