NFKBIZ regulates NFκB signaling pathway to mediate tumorigenesis and metastasis of hepatocellular carcinoma by direct interaction with TRIM16

Hepatocellular carcinoma (HCC) is a malignant tumor with high incidence and mortality rates. NFKBIZ, a member of the nuclear factor kappa B inhibitory family, is closely related to tumor progression. However, the precise role of NFKBIZ in HCC remains unclear. To explore this, we conducted a series of experiments from clinic to cells. Western blot and qPCR revealed a significant downregulation of NFKBIZ in human HCC tissues. Clinical character analysis showed that the patients with lower NFKBIZ expression had poorer prognosis and higher clinical stage. By using CCK-8, wound healing, transwell invasion and migration assay, we discovered that NFKBIZ expression was reversely associated with the proliferation, invasion, and migration ability of HCC cells in vitro. Additionally, the results obtained from xenograft assay and lung metastasis models showed that NFKBIZ overexpression inhibited the growth and metastasis of HCC cells in vivo. Western blot and immunofluorescence assay further revealed that NFKBIZ mediated HCC cell growth and migration by regulating NFκB signaling transduction. Finally, flow cytometry, protein degradation assay and Co-immunoprecipitation indicated that TRIM16 can enhance NFKBIZ ubiquitination by direct interactions at its K48 site, which may thereby alleviate HCC cell apoptosis to induce the insensitivity to sorafenib. In conclusion, our study demonstrated that NFKBIZ regulated HCC tumorigenesis and metastasis by mediating NFκB signal transduction and TRIM16/NFKBIZ/NFκB axis may be the underlying mechanism of sorafenib insensitivity in HCC.

IκBζ is a dual-use coactivator of NF-κB and POU transcription factors

OCA-B, OCA-T1, and OCA-T2 belong to a family of coactivators that bind to POU transcription factors (TFs) to regulate gene expression in immune cells. Here, we identify IκBζ (encoded by the NFKBIZ gene) as an additional coactivator of POU TFs. Although originally discovered as an inducible regulator of NF-κB, we show here that IκBζ shares a microhomology with OCA proteins and uses this segment to bind to POU TFs and octamer-motif-containing DNA. Our functional experiments suggest that IκBζ requires its interaction with POU TFs to coactivate immune-related genes. This finding is reinforced by epigenomic analysis of MYD88L265P-mutant lymphoma cells, which revealed colocalization of IκBζ with the POU TF OCT2 and NF-κB:p50 at hundreds of DNA elements harboring octamer and κB motifs. These results suggest that IκBζ is a transcriptional coactivator that can amplify and integrate the output of NF-κB and POU TFs at inducible genes in immune cells.

Toll-like receptor 9 signaling in chronic lymphocytic leukemia cell lines

Chronic lymphocytic leukemia (CLL) is a prototypic neoplasia in which malignant cells strongly depend on microenvironmental stimulations in the lymphoid tissues where they accumulate; leukemic cells are exposed to interaction with bystander and accessory cells, as well as inflammatory soluble mediators. Cell lines are frequently used to model the pathobiology of this disease; however, they do not always recapitulate leukemic cell growth and response to stimulation, and no data are available on Toll-like receptors (TLR) signaling in CLL cell lines. To address this gap, we analyzed HG3, MEC2, and PCL12 cell lines, before and after CpG stimulation, by RNA-sequencing followed by bioinformatic analyses and validation experiments. We identified NFKBIZ mRNA and the corresponding IkBz protein as robust markers of TLR9 activation in both MEC2 and PCL12, but not in HG3 cells. Next, we compared our current results with previous results obtained with primary CLL patient samples and were able to conclude that MEC2 is most similar to the patients' cells in terms of global responsiveness to TLR stimulation; in particular, MEC2 better resembles the samples of patients, as it is characterized by high expression levels of IkBz, but with a lower number of genes regulated.

miR-4734 conditionally suppresses ER stress-associated proinflammatory responses

Prolonged metabolic stress can lead to severe pathologies. In metabolically challenged primary fibroblasts, we assigned a novel role for the poorly characterized miR-4734 in restricting ATF4 and IRE1-mediated upregulation of a set of proinflammatory cytokines and endoplasmic reticulum stress-associated genes. Conversely, inhibition of this miRNA augmented the expression of those genes. Mechanistically, miR-4734 was found to restrict the expression of the transcriptional activator NF-kappa-B inhibitor zeta (NFKBIZ), which is required for optimal expression of the proinflammatory genes and whose mRNA is targeted directly by miR-4734. Concordantly, overexpression of NFKBIZ compromised the effects of miR-4734, underscoring the importance of this direct targeting. As the effects of miR-4734 were evident under stress but not under basal conditions, it may possess therapeutic utility towards alleviating stress-induced pathologies.

Emerging role of IκBζ in inflammation: Emphasis on psoriasis

Psoriasis is a chronic inflammatory disorder affecting skin and joints that results from immunological dysfunction such as enhanced IL-23 induced Th-17 differentiation. IkappaB-Zeta (IκBζ) is an atypical transcriptional factor of the IκB protein family since, contrary to the other family members, it positively regulates NF-κB pathway by being exclusively localized into the nucleus. IκBζ deficiency reduces visible manifestations of experimental psoriasis by diminishing expression of psoriasis-associated genes. It is thus tempting to consider IκBζ as a potential therapeutic target for psoriasis as well as for other IL23/IL17-mediated inflammatory diseases. In this review, we will discuss the regulation of expression of NFKBIZ and its protein IκBζ, its downstream targets, its involvement in pathogenesis of multiple disorders with emphasis on psoriasis and evidences supporting that inhibition of IκBζ may be a promising alternative to current therapeutic managements of psoriasis.

I-Kappa-B-Zeta Regulates Interleukin-17A/Tumor Necrosis Factor-Alpha Mediated Synergistic Induction of Interleukin-19 and Interleukin-20 in Humane Keratinocytes

Background

Interleukin (IL)-19 and IL-20 are important members of the IL-10 cytokine family, which are known to play a role in inflammatory processes. Both anti-IL-19 and -IL-20 targeting drugs have been suggested in the treatment of inflammatory diseases such as psoriasis and rheumatoid arthritis. Recently, we presented I-kappa-B-zeta (IκBζ) as a key player in psoriasis by identifying IκBζ as a regulator of IL-17/tumor necrosis factor (TNF)α-inducible psoriasis-associated genes and proteins. Some of these genes were synergistically regulated by IL-17/TNFα.

Objective

The purpose of this study was to explore the role of IκBζ in the regulation of IL-17A/TNFα-mediated induction of IL-19 and IL-20 expression in human keratinocytes.

Methods

In vitro experiments with cultured primary humane keratinocytes were conducted and investigated by quantitative polymerase chain reaction (qPCR), Western blotting, ELISA and EMSA. For statistics, a one- or two- way repeated-measures analysis of variance (RM ANOVA) or the Friedman test (a nonparametric equivalent to the RM ANOVA) were conducted.

Results

We demonstrated that IL-19 and IL-20 mRNA and protein expressions were synergistically induced by IL-17A and TNFα, whereas IL-17A and TNFα alone had only a minor effect on the IL-19 and IL-20 expression. Moreover, we demonstrated IκBζ to be a regulator of this synergistic induction of IL-19 and IL-20. Finally, the IL-17A/TNFα-induced synergistic induction of IL-19 and IL-20 expression was found to be mediated by a p38 MAPK-, NF-κB- and JNK1/2-dependent mechanism.

Conclusion

This study demonstrates that IκBζ plays a role in the IL-17A/TNFα-mediated synergistic induction of IL-19 and IL-20 in humane keratinocytes.

IκBζ is a key player in the antipsoriatic effects of secukinumab

BACKGROUND

IκBζ plays a key role in psoriasis by mediating IL-17A-driven effects, but the molecular mechanism by which IL-17A regulates IκBζ expression is not clarified.

OBJECTIVE

We sought to explore the molecular transformation in patients with psoriasis during anti-IL-17A (secukinumab) treatment with a focus on IκBζ.

METHODS

The study was an open-label, single-arm, single-center secukinumab treatment study that included 14 patients with plaque psoriasis. Skin biopsy specimens and blood samples were collected on days 0, 4, 14, 42, and 84 and processed for microarray gene expression analysis. Furthermore, in vitro experiments with human keratinocytes and synovial fibroblasts were conducted.

RESULTS

Secukinumab improved clinical scores and histologic psoriasis features. Moreover, secukinumab altered the skin transcriptome. The major transcriptional shift appeared between day 14 and day 42 after treatment initiation, although 80 genes were differentially expressed already at day 4. Expression of nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor (IκB) ζ (NFKBIZ, the gene encoding IκBζ) was reduced already after 4 days of treatment in the skin. NFKBIZ expression correlated to Psoriasis Area and Severity Index score, and NFKBIZ mRNA levels in the skin decreased during anti-IL-17A treatment. Moreover, specific NFKBIZ signature genes were significantly altered during anti-IL-17A treatment. Finally, we identified NF-κB activator 1 (Act1), p38 mitogen-activated protein kinase (MAPK), Jun NH2-terminal kinase (JNK), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) as key signaling pathways in NFKBIZ/IκBζ regulation.

CONCLUSION

Our results define a crucial role for IκBζ in the antipsoriatic effect of secukinumab. Because IκBζ signature genes were regulated already after 4 days of treatment, this strongly indicates that IκBζ plays a crucial role in the antipsoriatic effects mediated by anti-IL-17A treatment.

IκBζ is a key transcriptional regulator of IL-36-driven psoriasis-related gene expression in keratinocytes

Psoriasis is an autoinflammatory disease characterized by cytokine-driven keratinocyte proliferation and infiltration of immune cells. While IL-17A and TNFα are established targets in psoriasis therapy, IL-36 is emerging as an important cytokine in this disease. The mechanisms of IL-36–driven proinflammatory responses are largely unknown. Here we identified IκBζ, a transcriptional regulator of selective NF-κB target genes, as a crucial mediator of IL-36 action. In keratinocytes, IκBζ was required for the expression of several psoriasis-related cytokines and chemokines. Moreover, genetic deletion of IκBζ prevented IL-36–mediated dermatitis induction in mice. Since IκBζ is essential not only for IL-36 but also for IL-17 signaling, our results suggest that inhibition of IκBζ function could be a future strategy in psoriasis therapy.

Proinflammatory cytokine signaling in keratinocytes plays a crucial role in the pathogenesis of psoriasis, a skin disease characterized by hyperproliferation and abnormal differentiation of keratinocytes and infiltration of inflammatory cells. Although IL-17A and TNFα are effective therapeutic targets in psoriasis, IL-36 has recently emerged as a proinflammatory cytokine. However, little is known about IL-36 signaling and its downstream transcriptional responses. Here, we found that exposure of keratinocytes to IL-36 induced the expression of IκBζ, an atypical IκB member and a specific transcriptional regulator of selective NF-κB target genes. Induction of IκBζ by IL-36 was mediated by NF-κB and STAT3. In agreement, IL-36–mediated induction of IκBζ was found to be required for the expression of various psoriasis-related genes involved in inflammatory signaling, neutrophil chemotaxis, and leukocyte activation. Importantly, IκBζ-knockout mice were protected against IL-36–mediated dermatitis, accompanied by reduced proinflammatory gene expression, decreased immune cell infiltration, and a lack of keratinocyte hyperproliferation. Moreover, expression of IκBζ mRNA was highly up-regulated in biopsies of psoriasis patients where it coincided with IL36G levels. Thus our results uncover an important role for IκBζ in IL-36 signaling and validate IκBζ as an attractive target for psoriasis therapy.

House Dust Mite Allergens and the Induction of Monocyte Interleukin 1β Production That Triggers an IκBζ-Dependent Granulocyte Macrophage Colony-Stimulating Factor Release from Human Lung Epithelial Cells

Asthma is a chronic lung disease characterized by inflammation centered upon bronchial epithelium. House dust mite is one of the most common respiratory allergens that trigger exacerbations of asthma. IκBζ (gene NFKBIZ) is a recently recognized member of the NF-κB family that can be induced in mononuclear phagocytes and lung epithelial cells and has been shown to play a prominent role in epithelial cell function. We therefore analyzed the role of IκBζ in regulating lung epithelial cell cytokine responses to house dust mite mix (HDM). We found that human bronchial epithelial cells express IκBζ and release IL-6 and granulocyte macrophage colony-stimulating factor (GMCSF) when cocultured with human monocytes and HDM. This response is blocked in the presence of IL-1 receptor antagonist (IL-1Ra), indicating that it is IL-1 mediated. Neither HDM-stimulated macrophages nor dendritic cells release IL-1β and subsequently induce cytokine release from the bronchial epithelial cells. Rhodobacter sphaeroides LPS (RS-LPS), a TLR4 antagonist, blocks the ability of HDM to induce IκBζ and release GMCSF from epithelial cells cocultured with monocytes. Additionally, human bronchial epithelial cells show no induction of IκBζ or cytokine responses to direct HDM stimulation. Finally, NFKBIZ small interfering RNA-mediated knockdown in the bronchial epithelial cells suppresses the release of IL-1-induced IL-6 and GMCSF. Our findings indicate a possible role for monocyte recruitment and lung epithelial cell IκBζ in mediating asthma associated inflammation. Thus, IκBζ, IL-1Ra, and RS-LPS deserve future study as potential modulators of house dust mite-induced asthma.