Role Of RelB Research Articles

The Alternative RelB NF-kB Subunit Exerts a Critical Survival Function upon Metabolic Stress in Diffuse Large B-Cell Lymphoma-Derived Cells.

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma in adults and reveals distinct genetic and metabolic signatures. NF-κB transcription factor family is involved in diverse biological processes enabling tumor development and resistance to anticancer-therapy through activation of its two main pathways, the canonical and the alternative NF-κB pathways, the main actor of the latter being the RelB NF-kB subunit. RelB DNA binding activity is frequently activated in DLBCL patients and cell lines. RelB activation defines a new DLBCL subgroup with dismal outcome upon immunochemotherapy, and RelB confers DLBCL cell resistance to DNA damage. However, whether RelB can impact on DLBCL cell metabolism and survival upon metabolic stress is unknown. Here, we reveal that RelB controls DLBCL oxidative energetic metabolism. Accordingly, RelB inhibition reduce DLBCL mitochondrial ATP production, and sensitizes DLBCL cells to apoptosis induced by Metformin and L-asparaginase (®Kidrolase), two FDA approved antimetabolic drugs targeting mitochondrial metabolism. RelB also confers DLBCL cell resistance to glutamine deprivation, an essential amino acid that feeds the TCA cycle. Taken together, our findings uncover a new role for RelB in the regulation of DLBCL cell metabolism and DLBCL cell survival upon metabolic stress.

A T cell-intrinsic function for NF-\u03baB RelB in experimental autoimmune encephalomyelitis

NF-kappaB (NF-κB) is a family of transcription factors with pleiotropic functions in immune responses. The alternative NF-κB pathway that leads to the activation of RelB and NF-κB2, was previously associated with the activation and function of T cells, though the exact contribution of these NF-κB subunits remains unclear. Here, using mice carrying conditional ablation of RelB in T cells, we evaluated its role in the development of conventional CD4+ T (Tconv) cells and their function in autoimmune diseases. RelB was largely dispensable for Tconv cell homeostasis, activation and proliferation, and for their polarization toward different flavors of Thelper cells in vitro. Moreover, ablation of RelB had no impact on the capacity of Tconv cells to induce autoimmune colitis. Conversely, clinical severity of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS) was significantly reduced in mice with RelB-deficient T cells. This was associated with impaired expression of granulocyte–macrophage colony-stimulating factor (GM-CSF) specifically in the central nervous system. Our data reveal a discrete role for RelB in the pathogenic function of Tconv cells during EAE, and highlight this transcription factor as a putative therapeutic target in MS.

RelB regulates the homeostatic proliferation but not the function of Tregs

BackgroundRelB, a member of the NF-κB family, plays a critical role in the development of T cells. However, the role of RelB in Foxp3+ regulatory T cells (Tregs) remains controversial.ResultsUsing a bone marrow chimeric mouse model, we demonstrated that the expansion of Foxp3+ Tregs in vivo could be mediated by extrinsic mechanisms. RelB plays an important role in inhibiting the homeostatic proliferation of Tregs, but not their survival. Even with the heightened expansion, RelB−/− Treg cells displayed normal suppressive function in vitro. Among the expanded populations of Treg cells, most were nTreg cells; however, the population of iTregs did not increase. Mechanistically, RelB seems to regulate Treg proliferation independently of the signal transducer and activator of transcription 5 (STAT5) pathway.ConclusionsThese data suggest that RelB regulates Treg proliferation independently of the STAT5 pathway, but does not alter the function of Tregs. Further studies are warranted to uncover such mechanisms.

RelB silencing to reverse tamoxifen resistance by regulating GPx4 and ferroptosis in breast cancer.

e12513 Background: Tamoxifen(Tam), as an essential therapeutic treatment of estrogen receptor(ER)-positive breast cancer(BCa), has been available for the past three decades. However, the induction of Tam resistance during therapy has indicated a significant challenge with regards to this agent. Tam could increase oxidative stress and induce cell death by regulating reactive oxygen species(ROS). Ferroptosis, a cell death process driven by the accumulation of iron-dependent lipid peroxides, has been induced by inactivation/depletion of glutathione peroxidases(GPxs). Our previous studies found that the expression level of RelB gene, a member of NF-κB family, is negatively correlated with ER targeted by Tam in BCa. Methods: The RelB level of BCa tumor tissues and the corresponding cell lines were examined by immunoblotting and western blot. The effects of Tam on cell viability were determined using colony survival and MTT assay. The ROS and oxygen consumption rates(OCR) were measured using specific ROS detection probes and a Seahorse XF96 Analyzer, respectively. The lipid peroxidation level of cells was analyzed by immunofluorescence assay. The morphological changes of mitochondria were observed by transmission electron microscope. RelB binding to the NF-κB intronic enhancer region of the human GPx4 gene was determined using a ChIP assay. Accordingly, the effect of RelB on BCa Tam resistance was further validated using BCa mice xenograft models. Results: RelB was uniquely expressed at the high level in Tam resistance BCa tissues and cell lines. Down-regulation of RelB based on a CRISPR/Cas9 system remarkably sensitized resistance BCa cells to Tam. Treatment with SN52, a RelB inhibitor, illuminated the role of RelB in Tam-treated BCa cells. The high level of ROS and declination of mitochondrial respiration which induced by Tam were inhibited in resistance cells. Tam enhanced lipid peroxidation with concomitant non-apoptotic cell death, which are negatively regulated by GPx4 activity. In addition to GPx4 knockdown, deferoxamine was able to rescue Tam-induced cell death in BCa cells, verifying that Tam induces cell death partially through ferroptosis. Importantly, RelB upregulates GPx4 expression through binding to an NF-κB enhancer element located at the 5’-flanking region. Consistently, in vivo functional validation confirmed that RelB inhibition not only impairs tumor growth, but also inhibits Tam resistance in nude mice. Conclusions: RelB could inhibit ferroptosis which induced by hydroxyl radicals accumulation through upregulating GPx4 in BCa.

RelB suppresses type I Interferon signaling in dendritic cells

Type I Interferon (IFN) signaling plays a critical role in dendritic cell (DC) development and functions. Inhibition of hyper type I IFN signaling promotes cDC2 subtype development. Relb is essential to development of cDC2 subtype and here we analyzed its effect on type I IFN signaling in DCs. We show that Relb suppresses the homeostatic type I IFN signaling in cDC2 cultures. TLR stimulation of FL-DCs led to RelB induction coinciding with fall in IFN signatures; conforming with the observation Relb expression reduced TLR stimulated IFN induction along with decrease in ISGs. Towards understanding mechanism, we show that effects of RelB are mediated by increased levels of IκBα. We demonstrate that RelB dampened antiviral responses by lowering ISG levels and the defect in cDC2 development in RelB null mice can be rescued in Ifnar1−/− background. Overall, we propose a novel role of RelB as a negative regulator of the type I IFN signaling pathway; fine tuning development of cDC2 subtype.

RelB regulates basal and proinflammatory induction of conjunctival CCL2

ABSTRACT Purpose: This study investigated the involvement of NF-kB in regulating postoperative conjunctival inflammation. Methods: Experimental surgery was performed as described for the mouse model of conjunctival scarring. Expression of NF-κB in postoperative conjunctival tissues or conjunctival fibroblasts were assessed by real-time PCR, immunoblotting and immunofluorescence analyses. Downregulation of RelB was achieved using small interfering RNA. Cellular cytokine secretion was determined using multiplex cytokine assay. Results: RelB was the most highly induced member of the NF-kB family on day 2 post-surgery. Elevated RelB may be found associated with vimentin-positive cells and fibroblasts in vivo and in vitro. In conjunctival fibroblasts, RelB may be induced by TNF-α but not TGF-β2 while its silencing caused selective induction of CCL2 secretion by both basal and TNF-α-stimulated fibroblasts. Conclusions: High RelB induction in the inflammatory phase and the selective modulation of CCL2 suggest a specific anti-inflammatory role for RelB in the postoperative conjunctiva.

Abstract P3-09-03: RelB facilitates cell migration and invasion in breast cancer via MMP1 upregulation

Abstract Background: RelB is a subunit of the nuclear factor-κB (NF-κB) signaling famliy and appears aberrant expression in breast cancer. The aim of the present study was to further investigate the role of RelB in breast cancer and whether RelB might be a therapeutic target. Methods: 120 cases of breast cancer patients were collected from the Jiangsu Province Hospital during 2015-2017. Immunohistochemistry (IHC) was performed to detect RelB expression in breast cancer tissues and para-cancer tissues. The relationship between RelB expression and clinical pathologic parameters were investigated. Detection the expression of RelB in 4 kinds of human breast cancer cell lines (MCF-7, T47D, MDA-MB-231, BT-549) by Western blot and RT-qPCR.Knockout of RelB in TNBC cell lines (BT-549 and MDA-MB-231) was using the CRISPR/Cas9 genome editing system. CCK-8 and flow cytometry were performed to observe the proliferation, cycle and apoptosis of MDA-MB-231 and BT-549 after knockout of RelB. Transwell and wound healing experiments were performed to observe cell invasion and migration ability. RT-PCR and Western blotting were performed to detect the expression of mRNA and protein of EMT marker and MMP1 respectively. The luciferase reporter gene was performed to detect whether RelB binding with MMP1 promoter region. In vivo efficacy was tested using the xenograft model and lung metastasis model. Results: RelB was highly expressed in triple-negative breast cancer (TNBC) tissues compared with that in adjacent tissues. RelB levels were remarkably associated with the pTNM stage (p=0.01981) and ER expression (p=0.4689). RelB expressions in TNBC cell lines were higher than that of hormone receptor positive MCF-7 cells. In vitro studies showed that RelB deletion promoted apoptosis and suppressed breast cancer cell survival, migration and invasion by decreasing snail, vimentin and MMP1. RelB deletion inhibited cell cycle progression and G1/S transition by upregulating p21 and p27 expression. In vivo studies showed that 231-RelB-KO cells completely impaired tumor formation in xenograft models and lung metastasis model in nude mice. Conclusion: RelB is aberrant constitutive expressed in clinical specimens and cell lines of breast cancer, especially in TNBC. RelB regulates malignant phenotypes of breast cancer, including cell survival, migration and invasion, as well as apoptosis and the cell cycle. Moreover, RelB can induce MMP1, which facilitates the invasion of tumor. Collectively, our findings highlight that RelB might serve as a therapeutic target for triple negative breast cancer. Citation Format: Wang M, Tang J. RelB facilitates cell migration and invasion in breast cancer via MMP1 upregulation [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-09-03.

Correction: S100A9+ MDSC and TAM-mediated EGFR-TKI resistance in lung adenocarcinoma: the role of RELB.

[This corrects the article DOI: 10.18632/oncotarget.24146.].

Induction of CD4(+) Regulatory and Polarized Effector/helper T Cells by Dendritic Cells.

Dendritic cells (DCs) are considered to play major roles during the induction of T cell immune responses as well as the maintenance of T cell tolerance. Naive CD4+ T cells have been shown to respond with high plasticity to signals inducing their polarization into effector/helper or regulatory T cells. Data obtained from in vitro generated bone-marrow (BM)-derived DCs as well as genetic mouse models revealed an important but not exclusive role of DCs in shaping CD4+ T cell responses. Besides the specialization of some conventional DC subsets for the induction of polarized immunity, also the maturation stage, activation of specialized transcription factors and the cytokine production of DCs have major impact on CD4+ T cells. Since in vitro generated BM-DCs show a high diversity to shape CD4+ T cells and their high similarity to monocyte-derived DCs in vivo, this review reports data mainly on BM-DCs in this process and only touches the roles of transcription factors or of DC subsets, which have been discussed elsewhere. Here, recent findings on 1) the conversion of naive into anergic and further into Foxp3− regulatory T cells (Treg) by immature DCs, 2) the role of RelB in steady state migratory DCs (ssmDCs) for conversion of naive T cells into Foxp3+ Treg, 3) the DC maturation signature for polarized Th2 cell induction and 4) the DC source of IL-12 for Th1 induction are discussed.

Abstract 2515: Inverse relationship between PSA and IL-8 in prostate cancer: An insight into the mechanisms of NF-κB-mediated radioresistance

Abstract Nuclear factor κB (NF-κB), an inflammatory responsive transcription factor, is involved in tumorigenesis and resistance of cancer cells to therapy-induced cytotoxicity. Our previous studies demonstrated that activation of RelB-mediated NF-κB alternative pathway contributes to tumorigenicity of prostate cancer, decreased the circulating levels of prostate specific antigen (PSA), and enhanced the level of interleukin-8 (IL-8). The present study extends to directly test the role of RelB on radioresistance of prostate cancer in vivo, investigate the relationship between IL8 and PSA expression, and determine their role in the response of prostate cancer to radiation. We found that expression of RelB in prostate cancer cells with a low basal level of RelB (LNCaP) reduced their radiosensitivity and suppression of RelB in prostate cancer cells with a high basal level of RelB (PC3) enhanced their radiosensitivity in vitro and in xenograft tumors. The RelB-mediated inverse relationship between PSA and IL-8 expression was verified through direct modulation of RelB levels by transfection of RelB cDNA and RNAi in multiple prostate cancer cell lines. Interestingly, when the cellular levels of PSA and IL-8 were manipulated, by treating cultural cells with pure compounds or genetic manipulations, we found that up-regulation of IL-8 with concurrent down-regulation of PSA reduced radiosensitivity of prostate cancer cells. In contrast, up-regulation of PSA with concurrence down-regulation of IL-8 resulted in an increase in radiosensitivity. Together, the results reveal a previously unrecognized role of IL-8 on PSA expression, identify an inverse relationship between PSA and IL-8 as an indicator of radiosensitivity and implicate inhibition of the NF-κB alterative pathway as a promising approach for prostate cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2515. doi:10.1158/1538-7445.AM2011-2515

Stabilization of RelB Requires Multidomain Interactions with p100/p52

The NF-kappaB family member RelB has many properties not shared by other family members such as restricted subunit association and lack of regulation by the classical IkappaB proteins. We show that the protein level of RelB is significantly reduced in the absence of p100 and reduced even more when both p100 and p105 are absent. RelB stabilizes itself by directly interacting with p100, p105, and their processed products. However, RelB forms complexes with its partners using different interaction modes. Although the C-terminal ankyrin repeat domain of p105 is not involved in the RelB-p105 complex formation, all domains and flexible regions of each protein are engaged in the RelB-p100 complex. In several respects the RelB-p52 and RelB-p100 complexes are unique in the NF-kappaB family. The N-terminal domain of p100/p52 interacts with RelB but not RelA. The transcriptional activation domain of RelB, but not RelA, directly interacts with the processing region of p100. These unique protein-protein contacts explain why RelB prefers p52 as its dimeric partner for transcriptional activity and is retained in the cytoplasm as an inhibited complex by p100. This association-mediated stabilization of RelB implies a possible role for RelB in the processing of p100 into p52.

Hematopoiesis of immature myeloid dendritic cells in stroma-dependent spleen long-term cultures occurs independently of NF- kB/RelB function

The nuclear factor-kappaB (NF-KB)/RelB transcription factor plays an essential role in development of some dendritic cell (DC) subsets in mice. In this laboratory, immature myeloid DC are produced in vitro in a stroma-dependent murine spleen long-term culture (LTC) system. In LTC, DC differentiate from hematopoietic progenitors maintained within the stromal cell matrix. Expression and function of RelB in development of LTC-DC has been investigated, with a view to assessing the relationship between DC produced in this system and other known subsets of DC. RelB expression by LTC-DC was confirmed by detection of protein by Western blotting, RNA by reverse transcription polymerase chain reaction, and nuclear protein with DNA-binding function in electrophoretic mobility shift assays. The role of RelB in cell development was assessed by addition of antisense RelB oligonucleotides into LTC and colony assays established above STX3 stromal cells. RelB(-/-) mice were also examined for ability to produce LTC, and for presence of DC progenitors in spleen and bone marrow that can generate DC when overlaid on STX3 in cocultures. Functional RelB was detected in both LTC-DC and in STX3 stromal cells. A critical role for RelB in DC differentiation from spleen progenitors was confirmed, because antisense RelB oligonucleotides specifically and completely inhibited production of large differentiated myeloid DC in LTC. Further investigation using RelB(-/-) mice revealed that RelB expression by stromal cells rather than hematopoietic cells was required for production of LTC-DC. This was evidenced by a combination of factors, including 1) inability to generate productive LTC from RelB(-/-) mice; 2) presence of DC precursors in RelB(-/-) bone marrow and spleen, which could produce DC in stromal cocultures; and 3) increased myeloid precursor frequency among RelB(-/-) spleen cells over RelB(+/+) control cell populations. Specific development of fully differentiated, but immature myeloid CD11c(+)CD11b(+)MHC-CII(-)CD8alpha(-)CD40(-) DC in spleen LTC is dependent on expression of activated NF-kappaB/Rel-B. However, this appears to relate to stromal cell function rather than to the function of hematopoietic cells. Altogether these data confirm the importance of splenic stromal cells in myelopoiesis leading to development of immature DC as produced in LTC.