Inducible tumor necrosis factor (TNF) receptor-associated factor-1 expression couples the canonical to the non-canonical NF-κB pathway in TNF stimulation

Fueling CARs: metabolic strategies to enhance CAR T-cell therapy

CAR T cells are widely applied for relapsed hematological cancer patients. With six approved cell therapies, for Multiple Myeloma and other B-cell malignancies, new insights emerge. Profound evidence shows that patients who fail CAR T-cell therapy have, aside from antigen escape, a more glycolytic and weakened metabolism in their CAR T cells, accompanied by a short lifespan. Recent advances show that CAR T cells can be metabolically engineered towards oxidative phosphorylation, which increases their longevity via epigenetic and phenotypical changes. In this review we elucidate various strategies to rewire their metabolism, including the design of the CAR construct, co-stimulus choice, genetic modifications of metabolic genes, and pharmacological interventions. We discuss their potential to enhance CAR T-cell functioning and persistence through memory imprinting, thereby improving outcomes. Furthermore, we link the pharmacological treatments with their anti-cancer properties in hematological malignancies to ultimately suggest novel combination strategies.

Hexavalent chromium exposure activates the non-canonical nuclear factor kappa B pathway to promote immune checkpoint protein programmed death-ligand 1 expression and lung carcinogenesis

Lung cancer is the leading cause of cancer-related death worldwide; however, the mechanism of lung carcinogenesis has not been clearly defined. Chronic exposure to hexavalent chromium [Cr(VI)], a common environmental and occupational pollutant, causes lung cancer, representing an important lung cancer etiology factor. The mechanism of how chronic Cr(VI) exposure causes lung cancer remains largely unknown. By using cell culture and mouse models and bioinformatics analyses of human lung cancer gene expression profiles, this study investigated the mechanism of Cr(VI)-induced lung carcinogenesis. A new mouse model of Cr(VI)-induced lung carcinogenesis was developed as evidenced by the findings showing that a 16-week Cr(VI) exposure (CaCrO4, 100 μg per mouse once per week) via oropharyngeal aspiration induced lung adenocarcinomas in male and female A/J mice, whereas none of the sham-exposed control mice had lung tumors. Mechanistic studies revealed that chronic Cr(VI) exposure activated the non-canonical NFκB pathway through the long non-coding RNA (lncRNA) ABHD11-AS1/deubiquitinase USP15-mediated tumor necrosis factor receptor-associated factor 3 (TRAF3) down-regulation. The non-canonical NFκB pathway activation increased the interleukin 6 (IL-6)/Janus kinase (Jak)/signal transducer and activator of transcription 3 (Stat3) signaling. The activation of the IL-6/Jak signaling axis by Cr(VI) exposure not only promoted inflammation but also stabilized the immune checkpoint molecule programmed death-ligand 1 (PD-L1) protein in the lungs, reducing T lymphocyte infiltration to the lungs. Given the well-recognized critical role of PD-L1 in inhibiting anti-tumor immunity, these findings suggested that the lncRNA ABHD11-AS1-mediated non-canonical NFκB pathway activation and PD-L1 up-regulation may play important roles in Cr(VI)-induced lung carcinogenesis.

Mathematical models disentangle the role of IL-10 feedbacks in human monocytes upon proinflammatory activation

Inflammation is one of the vital mechanisms through which the immune system responds to harmful stimuli. During inflammation, proinflammatory and anti-inflammatory cytokines interplay to orchestrate fine-tuned and dynamic immune responses. The cytokine interplay governs switches in the inflammatory response and dictates the propagation and development of the inflammatory response. Molecular pathways underlying the interplay are complex, and time-resolved monitoring of mediators and cytokines is necessary as a basis to study them in detail. Our understanding can be advanced by mathematical models that enable to analyze the system of interactions and their dynamical interplay in detail. We, therefore, used a mathematical modeling approach to study the interplay between prominent proinflammatory and anti-inflammatory cytokines with a focus on tumor necrosis factor and interleukin 10 (IL-10) in lipopolysaccharide-primed primary human monocytes. Relevant time-resolved data were generated by experimentally adding or blocking IL-10 at different time points. The model was successfully trained and could predict independent validation data and was further used to perform simulations to disentangle the role of IL-10 feedbacks during an acute inflammatory event. We used the insight to obtain a reduced predictive model including only the necessary IL-10-mediated feedbacks. Finally, the validated reduced model was used to predict early IL-10-tumor necrosis factor switches in the inflammatory response. Overall, we gained detailed insights into fine-tuning of inflammatory responses in human monocytes and present a model for further use in studying the complex and dynamic process of cytokine-regulated acute inflammation.

Transcriptional induction of NF-κB-inducing kinase by E2F4/5 facilitates collective invasion of GBM cells

The prognosis of high-grade gliomas, such as glioblastoma multiforme (GBM), is extremely poor due to the highly invasive nature of these aggressive cancers. Previous work has demonstrated that TNF-weak like factor (TWEAK) induction of the noncanonical NF-κB pathway promotes the invasiveness of GBM cells in an NF-κB-inducing kinase (NIK)-dependent manner. While NIK activity is predominantly regulated at the posttranslational level, we show here that NIK (MAP3K14) is upregulated at the transcriptional level in invading cell populations, with the highest NIK expression observed in the most invasive cells. GBM cells with high induction of NIK gene expression demonstrate characteristics of collective invasion, facilitating invasion of neighboring cells. Furthermore, we demonstrate that the E2F transcription factors E2F4 and E2F5 directly regulate NIK transcription and are required to promote GBM cell invasion in response to TWEAK. Overall, our findings demonstrate that transcriptional induction of NIK facilitates collective cell migration and invasion, thereby promoting GBM pathogenesis.

Transcriptional Induction of NF-kB-Inducing Kinase by E2F4/5 Facilitates Collective Invasion of Glioma Cells

The prognosis of high-grade gliomas, such as glioblastoma multiforme (GBM), is extremely poor due to the highly invasive nature of these aggressive cancers. Previous work has demonstrated that TNF-weak like factor (TWEAK) induction of the noncanonical NF-κB pathway increases the invasiveness of glioma cells in an NF-κB-inducing kinase (NIK)-dependent manner. While NIK activity is predominantly regulated at the posttranslational level, we show here that NIK ( MAP3K14 ) is upregulated at the transcriptional level in invading cell populations, with the highest expression observed in the most invasive cells. Glioma cells with high induction of NIK gene expression demonstrate characteristics of collective invasion, facilitating invasion of neighboring cells. Furthermore, we demonstrate that the E2F transcription factors E2F4 and E2F5 directly regulate NIK transcription and are required to promote glioma cell invasion in response to TWEAK. Overall, our findings demonstrate that transcriptional induction of NIK facilitates collective cell migration and invasion, thereby promoting glioma pathogenesis.

CD40/TRAF1 decreases synovial cell apoptosis in patients with rheumatoid arthritis through JNK/NF-κB pathway

INTRODUCTION

A genome-wide association analysis revealed a rheumatoid arthritis (RA)-risk-associated genetic locus on chromosome 9, which contained the tumor necrosis factor receptor-associated factor 1 (TRAF1). However, the detail mechanism by TRAF1 signaled to fibroblast-like synoviocytes (FLSs) apoptosis remains to be fully understood.

MATERIALS AND METHODS

Synovial tissue of 10 RA patients and osteoarthritis patients were obtained during joint replacement surgery. We investigated TRAF1 level and FLSs apoptosis percentage in vivo and elucidated the mechanism involved in the regulation of apoptotic process in vitro.

RESULTS

We proved the significant increase of TRAF1 level in FLSs of RA patients and demonstrated that TRAF1 level correlated positively with DAS28 score and negatively with FLSs apoptosis. Treatment with siTRAF1 was able to decrease MMPs levels and the phosphorylated forms of JNK/NF-κB in vitro. Moreover, JNK inhibitor could attenuate expression of MMPs and increase percentage of apoptosis in RA-FLSs, while siTRAF1 could not promote apoptosis when RA-FLSs were pretreated with JNK activator.

CONCLUSIONS

High levels of TRAF1 in RA synovium play an important role in the synovial hyperplasia of RA by suppressing apoptosis through activating JNK/NF-kB-dependent signaling pathways in response to the engagement of CD40.

The canonical and non-canonical NF-κB pathways and their crosstalk: A comparative study based on Petri nets

NF-κB is a protein complex that occurs in almost all animal cell types. It regulates the cellular immune responses to stimuli in the nucleus. Dysregulation of NF-κB can cause severe diseases like chronic inflammation, autoimmune diseases or cancer. We modeled the two major pathways leading from the external cellular stimulation of the CD40 receptor to the nuclear translocation of NF-κB dimers, the canonical and non-canonical pathway. Based on literature data, we developed two Petri net models describing these pathways. In a third Petri net, we combined the two models, introducing crosstalk specific in CD40L-stimulated B cells. In terms of structural properties, we checked the Petri nets for their consistency and correctness. To explore differences and similarities, we compared structural properties and the simulation behavior of the models. The non-canonical NF-κB pathway exhibited a more diverse regulation than the canonical pathway. Applying in silico knockout analyses, we were able to quantify the relevance of individual biochemical processes. We predicted interrelationships, e.g., between the synthesis of the protein NF-κB-inducing kinase and the processing of the precursor protein p100. The activation of the transcription factors, p50-RelA and p52-RelB, was affected by most of the knockouts. The results of the in silico knockout were in accordance with experimental studies. The Petri net models provide a basis for further analyses and could be extended to include gene expression, additional pathways, molecular processes, and kinetic data.

Inhibitory feedback control of NF-κB signalling in health and disease

Cells must adapt to changes in their environment to maintain cell, tissue and organismal integrity in the face of mechanical, chemical or microbiological stress. Nuclear factor-κB (NF-κB) is one of the most important transcription factors that controls inducible gene expression as cells attempt to restore homeostasis. It plays critical roles in the immune system, from acute inflammation to the development of secondary lymphoid organs, and also has roles in cell survival, proliferation and differentiation. Given its role in such critical processes, NF-κB signalling must be subject to strict spatiotemporal control to ensure measured and context-specific cellular responses. Indeed, deregulation of NF-κB signalling can result in debilitating and even lethal inflammation and also underpins some forms of cancer. In this review, we describe the homeostatic feedback mechanisms that limit and ‘re-set’ inducible activation of NF-κB. We first describe the key components of the signalling pathways leading to activation of NF-κB, including the prominent role of protein phosphorylation and protein ubiquitylation, before briefly introducing the key features of feedback control mechanisms. We then describe the array of negative feedback loops targeting different components of the NF-κB signalling cascade including controls at the receptor level, post-receptor signalosome complexes, direct regulation of the critical ‘inhibitor of κB kinases’ (IKKs) and inhibitory feedforward regulation of NF-κB-dependent transcriptional responses. We also review post-transcriptional feedback controls affecting RNA stability and translation. Finally, we describe the deregulation of these feedback controls in human disease and consider how feedback may be a challenge to the efficacy of inhibitors.

Mathematical modeling of canonical and non-canonical NF-κB pathways in TNF stimulation

BACKGROUND AND OBJECTIVE

NF-κB can be activated by the canonical and non-canonical pathways. These two pathways interplay via the TRAF1|NIK complex after stimulation by TNF. However existing mathematical models of two pathways are inadequate. In this context, an improved mathematical model is constructed to simulate these two pathways and their coupling stimulated by TNF.

METHODS

A schematic description of two NF-κB pathways and their relation after TNF stimulation is constructed at first. Then twenty-eight ordinary differential equations are utilized to build the mathematical model. Model equations are solved via the ordinary differential equation solver (ode23).

RESULTS

The proposed model firstly reconstructs the changes in concentrations of NF-κB pathway related biochemical factors with time, and further investigates the underlying mechanism of interaction between two pathways through the TRAF1|NIK complex after stimulation.

CONCLUSIONS

The model is validated through good agreement between simulation results and published experimental observations. This study helps to well understand the canonical and non-canonical pathways and their interaction. It also provides a potential tool to investigate how the dysregulated pathways act in pathological conditions.

A20 Promotes Ripoptosome Formation and TNF-Induced Apoptosis via cIAPs Regulation and NIK Stabilization in Keratinocytes

The ubiquitin-editing protein A20 (TNFAIP3) is a known key player in the regulation of immune responses in many organs. Genome-wide associated studies (GWASs) have linked A20 with a number of inflammatory and autoimmune disorders, including psoriasis. Here, we identified a previously unrecognized role of A20 as a pro-apoptotic factor in TNF-induced cell death in keratinocytes. This function of A20 is mediated via the NF-κB-dependent alteration of cIAP1/2 expression. The changes in cIAP1/2 protein levels promote NIK stabilization and subsequent activation of noncanonical NF-κB signaling. Upregulation of TRAF1 expression triggered by the noncanonical NF-κB signaling further enhances the NIK stabilization in an autocrine manner. Finally, stabilized NIK promotes the formation of the ripoptosome and the execution of cell death. Thus, our data demonstrate that A20 controls the execution of TNF-induced cell death on multiple levels in keratinocytes. This signaling mechanism might have important implications for the development of new therapeutic strategies for the treatment of A20-associated skin diseases.

Proteomics study of the antifibrotic effects of α-mangostin in a rat model of renal fibrosis

Background

Renal fibrosis is a consequence of a “faulty” wound-healing mechanism that results in the accumulation of extracellular matrix, which could lead to the impairment of renal functions. α-Mangostin (AM) may prevent the formation of liver fibrosis, but there has yet to be a conclusive investigation of its effect on renal fibrosis.

Objectives

To investigate the renoprotective effect of AM against thioacetamide (TAA)-induced renal fibrosis in rats at the morphological and proteomic levels.

Methods

We divided 18 male Wistar rats into 3 groups: a control group, a TAA-treated group, and a TAA + AM group. The various agents used to treat the rats were administered intraperitoneally over 8 weeks. Subsequently, the morphology of renal tissue was analyzed by histology using Sirius Red staining and the relative amount of stained collagen fibers quantified using ImageJ analysis. One-dimensional gel liquid chromatography with tandem mass spectrometry (GeLC-MS/MS) was used to track levels of protein expression. Proteomic bioinformatics tools including STITCH were used to correlate the levels of markers known to be involved in fibrosis with Sirius Red-stained collagen scoring.

Results

Histology revealed that AM could reduce the relative amount of collagen fibers significantly compared with the TAA group. Proteomic analysis revealed the levels of 4 proteins were modulated by AM, namely CASP8 and FADD-like apoptosis regulator (Cflar), Ragulator complex protein LAMTOR3 (Lamtor3), mitogen-activated protein kinase kinase kinase 14 (Map3k14), and C-Jun-amino-terminal kinase-interacting protein 3 (Mapk8ip3).

Conclusion

AM can attenuate renal fibrosis by the suppression of pathways involving Cflar, Lamtor3, Map3k14, and Mapk8ip3.

Increased expression of CD40/TRAF1 and activation of nuclear factor-κκB-dependent proinflammatory gene expression in collagen-induced arthritis

OBJECTIVE

Genetic studies have implicated both CD40 and tumour necrosis factor receptor-associated factor-1 (TRAF1) with rheumatoid arthritis (RA). CD40 signalling is known to be associated with TRAF1 expression, directly or indirectly; however, the detailed mechanisms of these interactions are not clear in RA, and in particular in fibroblast-like synoviocytes. This study aims to investigate this pathway and the role of nuclear factor-κB (NF-κB) in a mouse model of RA.

METHOD

We utilized the collagen-induced arthritis (CIA) model in DBA/1 mice. CD40, TRAF1, and NF-κB p65 were quantitated by enzyme-linked immunosorbent assay and immunohistochemistry in serum and tissue, respectively. Real-time polymerase chain reaction was applied to measure NF-κB-related gene expression, including cytokines [tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6)] and adhesion molecules [intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1)].

RESULTS

The severity of arthritis by clinical and histological assessments peaked on day 35 and decreased thereafter. Serum levels of CD40, TRAF1, and NF-κB p65 paralleled this time-course. The tissue expression of the CD40, TRAF1, total NF-κB p65, and phospho-NF-κB p65 proteins, as well as NF-κB-related gene expression, including cytokines (TNFα, IL-6) and adhesion molecules (ICAM-1, VCAM-1), were markedly upregulated within 25-50 days after CIA.

CONCLUSION

Our data identify a cellular/molecular mechanism of the CD40/TRAF1 signalling pathway involved in CIA: increased expression of CD40 and its adaptor TRAF1 proteins and activation of the NF-κB-dependent proinflammatory pathway. These correlations implicate possible mechanistic pathways in this model that may also operate in human RA and thus provide rationales for new therapeutic modalities.

Cardiolipotoxicity, Inflammation, and Arrhythmias: Role for Interleukin-6 Molecular Mechanisms

Fatty acid infiltration of the myocardium, acquired in metabolic disorders (obesity, type-2 diabetes, insulin resistance, and hyperglycemia) is critically associated with the development of lipotoxic cardiomyopathy. According to a recent Presidential Advisory from the American Heart Association published in 2017, the current average dietary intake of saturated free-fatty acid (SFFA) in the US is 11–12%, which is significantly above the recommended <10%. Increased levels of circulating SFFAs (or lipotoxicity) may represent an unappreciated link that underlies increased vulnerability to cardiac dysfunction. Thus, an important objective is to identify novel targets that will inform pharmacological and genetic interventions for cardiomyopathies acquired through excessive consumption of diets rich in SFFAs. However, the molecular mechanisms involved are poorly understood. The increasing epidemic of metabolic disorders strongly implies an undeniable and critical need to further investigate SFFA mechanisms. A rapidly emerging and promising target for modulation by lipotoxicity is cytokine secretion and activation of pro-inflammatory signaling pathways. This objective can be advanced through fundamental mechanisms of cardiac electrical remodeling. In this review, we discuss cardiac ion channel modulation by SFFAs. We further highlight the contribution of downstream signaling pathways involving toll-like receptors and pathological increases in pro-inflammatory cytokines. Our expectation is that if we understand pathological remodeling of major cardiac ion channels from a perspective of lipotoxicity and inflammation, we may be able to develop safer and more effective therapies that will be beneficial to patients.

TRAF1 Signaling in Human Health and Disease

Tumor necrosis factor receptor (TNFR) associated factor 1 (TRAF1) is a signaling adaptor first identified as part of the TNFR2 signaling complex. TRAF1 plays a key role in pro-survival signaling downstream of TNFR superfamily members such as TNFR2, LMP1, 4-1BB, and CD40. Recent studies have uncovered another role for TRAF1, independent of its role in TNFR superfamily signaling, in negatively regulating Toll-like receptor and Nod-like receptor signaling, through sequestering the linear ubiquitin assembly complex, LUBAC. TRAF1 has diverse roles in human disease. TRAF1 is overexpressed in many B cell related cancers and single nucleotide polymorphisms (SNPs) in TRAF1 have been linked to non-Hodgkin's lymphoma. Genome wide association studies have identified an association between SNPs in the 5' untranslated region of the TRAF1 gene with increased incidence and severity of rheumatoid arthritis and other rheumatic diseases. The loss of TRAF1 from chronically stimulated CD8 T cells results in desensitization of the 4-1BB signaling pathway, thereby contributing to T cell exhaustion during chronic infection. These apparently opposing roles of TRAF1 as both a positive and negative regulator of immune signaling have led to some confusion in the literature. Here we review the role of TRAF1 as a positive and negative regulator in different signaling pathways. Then we discuss the role of TRAF1 in human disease, attempting to reconcile seemingly contradictory roles based on current knowledge of TRAF1 signaling and biology. We also discuss avenues for future research to further clarify the impact of TRAF1 in human disease.

CD137 (4-1BB) Signalosome: Complexity Is a Matter of TRAFs

CD137 (4-1BB, Tnsfr9) is a member of the TNF-receptor (TNFR) superfamily without known intrinsic enzymatic activity in its cytoplasmic domain. Hence, akin to other members of the TNFR family, it relies on the TNFR-Associated-Factor (TRAF) family of adaptor proteins to build the CD137 signalosome for transducing signals into the cell. Thus, upon CD137 activation by binding of CD137L trimers or by crosslinking with agonist monoclonal antibodies, TRAF1, TRAF2, and TRAF3 are readily recruited to the cytoplasmic domain of CD137, likely as homo- and/or heterotrimers with different configurations, initiating the construction of the CD137 signalosome. The formation of TRAF2-RING dimers between TRAF2 molecules from contiguous trimers would help to establish a multimeric structure of TRAF-trimers that is probably essential for CD137 signaling. In addition, available studies have identified a large number of proteins that are recruited to CD137:TRAF complexes including ubiquitin ligases and proteases, kinases, and modulatory proteins. Working in a coordinated fashion, these CD137-signalosomes will ultimately promote CD137-mediated T cell proliferation and survival and will endow T cells with stronger effector functions. Current evidence allows to envision the molecular events that might take place in the early stages of CD137-signalosome formation, underscoring the key roles of TRAFs and of K63 and K48-ubiquitination of target proteins in the signaling process. Understanding the composition and fine regulation of CD137-signalosomes assembly and disassembly will be key to improve the therapeutic activities of chimeric antigen receptors (CARs) encompassing the CD137 cytoplasmic domain and a new generation of CD137 agonists for the treatment of cancer.

Tumor Necrosis Factor Receptor-Associated Factor Regulation of Nuclear Factor κB and Mitogen-Activated Protein Kinase Pathways

Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) are a family of structurally related proteins that transduces signals from members of TNFR superfamily and various other immune receptors. Major downstream signaling events mediated by the TRAF molecules include activation of the transcription factor nuclear factor κB (NF-κB) and the mitogen-activated protein kinases (MAPKs). In addition, some TRAF family members, particularly TRAF2 and TRAF3, serve as negative regulators of specific signaling pathways, such as the noncanonical NF-κB and proinflammatory toll-like receptor pathways. Thus, TRAFs possess important and complex signaling functions in the immune system and play an important role in regulating immune and inflammatory responses. This review will focus on the role of TRAF proteins in the regulation of NF-κB and MAPK signaling pathways.

Temperature regulates NF-κB dynamics and function through timing of A20 transcription

NF-κB signaling plays a pivotal role in control of the inflammatory response. We investigated how the dynamics and function of NF-κB were affected by temperature within the mammalian physiological range (34 °C to 40 °C). An increase in temperature led to an increase in NF-κB nuclear/cytoplasmic oscillation frequency following Tumor Necrosis Factor alpha (TNFα) stimulation. Mathematical modeling suggested that this temperature sensitivity might be due to an A20-dependent mechanism, and A20 silencing removed the sensitivity to increased temperature. The timing of the early response of a key set of NF-κB target genes showed strong temperature dependence. The cytokine-induced expression of many (but not all) later genes was insensitive to temperature change (suggesting that they might be functionally temperature-compensated). Moreover, a set of temperature- and TNFα-regulated genes were implicated in NF-κB cross-talk with key cell-fate-controlling pathways. In conclusion, NF-κB dynamics and target gene expression are modulated by temperature and can accurately transmit multidimensional information to control inflammation.

MicroRNA-1180 is associated with growth and apoptosis in prostate cancer via TNF receptor associated factor 1 expression regulation and nuclear factor-κB signaling pathway activation

In the present study, the aim was to investigate the role of microRNA-1180 (miR-1180) in the growth and apoptosis of prostate cancer, as well as to identify its direct targets. Initially, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed to examine the expression of miR-1180 in the prostate cancer tissues and adjacent normal prostate tissues of 30 patients, as well as in DU145 and RWPE-1 cells. Next, DU145 cells were transfected with miR-1180 mimics, and the expression levels of associated proteins were determined by western blot assay. In addition, the role of miR-1180 in the proliferation, apoptosis, invasion and migration of DU145 cells was investigated by MTT, flow cytometry, cell invasion and wound healing assays, respectively. A dual-luciferase reporter assay was also performed to examine whether TNF receptor associated factor 1 (TRAF1) and B-cell lymphoma-2-associated athanogene 2 (BAG2) are direct targets of miR-1180. It was observed that miR-1180 expression was significantly decreased in the prostate cancer tissues compared with the normal prostate tissues, and was also inhibited in DU145 cells compared with RWPE-1 cells. Furthermore, transient overexpression of miR-1180 inhibited the proliferation, migration and invasion, and promoted the apoptosis of DU145 cells, as well as alleviated expression of associated proteins. The dual-luciferase reporter assay confirmed that TRAF1 and BAG2 are direct targets of miR-1180. These results suggested that miR-1180 contributed to prostate cancer by targeting TRAF1/BAG2 and by nuclear factor-κB signaling pathway activation.

TRAF molecules in inflammation and inflammatory diseases

Purpose of Review

This review presents an overview of the current knowledge of TRAF molecules in inflammation with an emphasis on available human evidence and direct in vivo evidence of mouse models that demonstrate the contribution of TRAF molecules in the pathogenesis of inflammatory diseases.

Recent Findings

The tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) family of cytoplasmic proteins was initially identified as signaling adaptors that bind directly to the intracellular domains of receptors of the TNF-R superfamily. It is now appreciated that TRAF molecules are widely employed in signaling by a variety of adaptive and innate immune receptors as well as cytokine receptors. TRAF-dependent signaling pathways typically lead to the activation of nuclear factor-κBs (NF-κBs), mitogen-activated protein kinases (MAPKs), or interferon-regulatory factors (IRFs). Most of these signaling pathways have been linked to inflammation, and therefore TRAF molecules were expected to regulate inflammation and inflammatory responses since their discovery in 1990s. However, direct in vivo evidence of TRAFs in inflammation and especially in inflammatory diseases had been lacking for many years, partly due to the difficulty imposed by early lethality of TRAF2^-/-, TRAF3^-/-, and TRAF6^-/- mice. With the creation of conditional knockout and lineage-specific transgenic mice of different TRAF molecules, our understanding about TRAFs in inflammation and inflammatory responses has rapidly advanced during the past decade.

Summary

Increasing evidence indicates that TRAF molecules are versatile and indispensable regulators of inflammation and inflammatory responses and that aberrant expression or function of TRAFs contributes to the pathogenesis of inflammatory diseases.

A TNF-p100 pathway subverts noncanonical NF-κB signaling in inflamed secondary lymphoid organs

Lymphotoxin-beta receptor (LTβR) present on stromal cells engages the noncanonical NF-κB pathway to mediate RelB-dependent expressions of homeostatic chemokines, which direct steady-state ingress of naïve lymphocytes to secondary lymphoid organs (SLOs). In this pathway, NIK promotes partial proteolysis of p100 into p52 that induces nuclear translocation of the RelB NF-κB heterodimers. Microbial infections often deplete homeostatic chemokines; it is thought that infection-inflicted destruction of stromal cells results in the downregulation of these chemokines. Whether inflammation per se also regulates these processes remains unclear. We show that TNF accumulated upon non-infectious immunization of mice similarly downregulates the expressions of these chemokines and consequently diminishes the ingress of naïve lymphocytes in inflamed SLOs. Mechanistically, TNF inactivated NIK in LTβR-stimulated cells and induced the synthesis of Nfkb2 mRNA encoding p100; these together potently accumulated unprocessed p100, which attenuated the RelB activity as inhibitory IκBδ. Finally, a lack of p100 alleviated these TNF-mediated inhibitions in inflamed SLOs of immunized Nfkb2-/- mice. In sum, we reveal that an inhibitory TNF-p100 pathway modulates the adaptive compartment during immune responses.

CD40L and TNF both activate the classical NF-κB pathway, which is not required for the CD40L induced alternative pathway in endothelial cells

CD40L and TNF signal through engagement of their respective receptors, which are both members of the TNF receptor family. They use partially common signaling molecules leading, among others, to activation of the NF-κB pathway. However, whereas TNF activates the classical, CD40L has been reported to activate the alternative NF-κB pathway, leading to the anticipation that differences in the pattern of inflammatory gene expression would occur. Here, we have compared the gene expression repertoire of CD40L (CD154) and TNF stimulated HUVEC and report that unexpectedly, apart from a stronger response to TNF, no major qualitative differences could be observed. This applies for the period of up to 6 h, a time where the alternative pathway has already been activated. Analysis of the early events after receptor engagement revealed that both TNF and CD40L activate the classical NF-κB pathway, and confirm activation of the alternative by the latter. Furthermore, using genetic and pharmacological inhibition of the classical pathway we show that activation of the alternative occurs independently of the former. This reveals novel insights into NF-κB signaling by CD40L and TNF in endothelial cells.

CagA promotes proliferation and inhibits apoptosis of GES-1 cells by upregulating TRAF1/4-1BB

Cytotoxin-associated gene A (CagA) is one of the most important virulence factors of Helicobacter pylori, and serves a role in H. pylori‑mediated tumorigenesis in gastric cancer. However, the underlying molecular mechanism remains to be elucidated. The present study aimed to investigate the effects of CagA on the proliferation and apoptosis of GES‑1 cells, and the underlying mechanism. A CagA eukaryotic expression plasmid was constructed and transfected into GES‑1 cells. The mRNA and protein levels of CagA, tumor necrosis factor receptor‑associated factor 1 (TRAF1) and tumor necrosis factor receptor superfamily member 9 (4‑1BB) were determined using the reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. Western blot and ELISA analysis was used to detect the release of interleukin (IL)‑8. An MTT assay and flow cytometric analysis was used to assess cell viability and apoptosis, respectively. Ectopic expression of CagA markedly increased TRAF1 and 4‑1BB mRNA and protein levels in GES‑1 cells. CagA increased the expression and release of IL‑8 in GES‑1 cells. The expression of CagA significantly promoted the proliferation (P<0.05) and inhibited the apoptosis (P<0.05) of GES‑1 cells. In conclusion, CagA upregulated TRAF1/4‑1BB, thereby promoting the proliferation and inhibiting the apoptosis of GES-1 cells.

Increased serum levels of tumor necrosis factor receptor-associated factor 1 (TRAF1) correlate with disease activity and autoantibodies in rheumatoid arthritis

BACKGROUND

In 2007 a genome wide association analyses revealed an additional risk-associated genetic region in rheumatoid arthritis (RA), the tumor necrosis factor receptor-associated factor 1-complement 5 (TRAF1-C5) containing locus on chromosome 9, comprehensive evaluation of the TRAF1 in RA patients remains necessary.

METHODS

Serum was obtained from 79 RA patients and from 38 healthy individuals. Concentrations of TRAF1 were measured by enzyme-linked immune sorbent assay (ELISA).

RESULTS

We found that the serum concentration of TRAF1 in RA patients was 35.9±51.2pg/ml, the serum concentration of TRAF1 in healthy controls was 12.5±8.6pg/ml. The difference between these 2 groups was significant (p=0.003). Patients with high disease activity had significantly higher TRAF1 concentration in comparison to patients with low and moderate disease activity (p<0.05). We also found that the numerical DAS28 had a significant positive correlation with TRAF1 concentration (r=0.419, p<0.001). We found that serum GPI and RF concentrations showed a significant positive correlation with TRAF1 concentrations respectively (r=0.767, p<0.001; r=0.365, p=0.001), while CCP concentration showed no significant correlation.

CONCLUSIONS

TRAF1 plays a crucial role in the pathogenesis of autoantibodies and may serve as a serologic inflammatory marker of disease activity in RA patients.

In vivo selection for spine-derived highly metastatic lung cancer cells is associated with increased migration, inflammation and decreased adhesion

We developed a murine spine metastasis model by screening five metastatic non-small cell lung cancer cell lines (PC-9, A549, NCI-H1299, NCI-H460, H2030). A549 cells displayed the highest tendency towards spine metastases. After three rounds of selection in vivo, we isolated a clone named A549L6, which induced spine metastasis in 80% of injected mice. The parameters of the A549L6 cell spinal metastatic mouse models were consistent with clinical spine metastasis features. All the spinal metastatic mice developed symptoms of nerve compression after 40 days. A549L6 cells had increased migration, invasiveness and decreased adhesion compared to the original A549L0 cells. In contrast, there was no significant differences in cell proliferation, apoptosis and sensitivity to chemotherapeutic agents such as cisplatin. Comparative transcriptomic analysis and Real-time PCR analysis showed that expression of signaling molecules regulating several tumor properties including migration (MYL9), metastasis (CEACAM6, VEGFC, CX3CL1, CST1, CCL5, S100A9, IGF1, NOTCH3), adhesion (FN1, CEACAM1) and inflammation (TRAF2, NFκB2 and RelB) were altered in A549L6 cells. We suggest that migration, adhesion and inflammation related genes contribute to spine metastatic capacity.

Deciphering CD137 (4-1BB) signaling in T-cell costimulation for translation into successful cancer immunotherapy

CD137 (4-1BB, TNF-receptor superfamily 9) is a surface glycoprotein of the TNFR family which can be induced on a variety of leukocyte subsets. On T and NK cells, CD137 is expressed following activation and, if ligated by its natural ligand (CD137L), conveys polyubiquitination-mediated signals via TNF receptor associated factor 2 that inhibit apoptosis, while enhancing proliferation and effector functions. CD137 thus behaves as a bona fide inducible costimulatory molecule. These functional properties of CD137 can be exploited in cancer immunotherapy by systemic administration of agonist monoclonal antibodies, which increase anticancer CTLs and enhance NK-cell-mediated antibody-dependent cell-mediated cytotoxicity. Reportedly, anti-CD137 mAb and adoptive T-cell therapy strongly synergize, since (i) CD137 expression can be used to select the T cells endowed with the best activities against the tumor, (ii) costimulation of the lymphocyte cultures to be used in adoptive T-cell therapy can be done with CD137 agonist antibodies or CD137L, and (iii) synergistic effects upon coadministration of T cells and antibodies are readily observed in mouse models. Furthermore, the signaling cytoplasmic tail of CD137 is a key component of anti-CD19 chimeric antigen receptors that are used to redirect T cells against leukemia and lymphoma in the clinic. Ongoing phase II clinical trials with agonist antibodies and the presence of CD137 sequence in these successful chimeric antigen receptors highlight the importance of CD137 in oncoimmunology.

S-adenosylhomocysteine induces inflammation through NFkB: A possible role for EZH2 in endothelial cell activation

S-adenosylhomocysteine (SAH) can induce endothelial dysfunction and activation, contributing to atherogenesis; however, its role in the activation of the inflammatory mediator NFkB has not been explored. Our aim was to determine the role of NFkB in SAH-induced activation of endothelial cells. Furthermore, we examined whether SAH, as a potent inhibitor of S-adenosylmethionine-dependent methyltransferases, suppresses the function of EZH2 methyltransferase to contribute to SAH-induced endothelial cell activation. We found that excess SAH increases the expression of adhesion molecules and cytokines in human coronary artery endothelial cells. Importantly, this up-regulation was suppressed in cells expressing a dominant negative form of the NFkB inhibitor, IkB. Moreover, SAH accumulation triggers the activation of both the canonical and non-canonical NFkB pathways, decreases EZH2, and reduces histone 3 lysine 27 trimethylation. EZH2 knockdown recapitulated the effects of excess SAH on endothelial activation, i.e., it induced NFkB activation and the subsequent up-regulation of adhesion molecules and cytokines. Our findings suggest that suppression of the epigenetic regulator EZH2 by excess SAH may contribute to NFkB activation and the consequent vascular inflammatory response. These studies unveil new targets of SAH regulation, demonstrating that EZH2 suppression and NFkB activation mediated by SAH accumulation may contribute to its adverse effects in the vasculature.

TNF induced inhibition of Cirbp expression depends on RelB NF-κB signalling pathway

The circadian clock is required for the rhythmic expression of a plethora of genes that orchestrate metabolism, sleep-wake behaviour and the immune response to pathogens. The cold-inducible RNA binding protein (CIRBP) is required for high amplitude expression of clock genes. Moreover, CIRBP protects the expression of clock genes from the inhibitory effects of tumour necrosis factor (TNF). However, since TNF represses Cirbp expression, the protective effect of CIRBP is lost. Here, we show that the TNF effect on Cirbp requires the non-canonical NF-κB signalling pathway. While a knock down of RelA does not alter the effects of TNF on Cirbp, a knock down of RelB represses this effect. In addition, the data indicate that p50 and p52 are required in the TNF induced inhibition of Cirbp. These results show that Cirbp expression in TNF treated cells is regulated via the non-canonical NF-κB pathway.

TRAF1 knockdown alleviates palmitate-induced insulin resistance in HepG2 cells through NF-κB pathway

High-fat diet (HFD) and inflammation are key contributors to insulin resistance (IR) and Type 2 diabetes mellitus (T2DM). With HFD, plasma free fatty acids (FFAs) can activate the nuclear factor-κB (NF-κB) in target tissues, then initiate negative crosstalk between FFAs and insulin signaling. However, the molecular link between IR and inflammation remains to be identified. We here reported that tumor necrosis factor receptor-associated factor 1 (TRAF1), an adapter in signal transduction, was involved in the onset of IR in hepatocytes. TRAF1 was significantly up-regulated in insulin-resistant liver tissues and palmitate (PA)-treated HepG2 cells. In addition, we showed that depletion of TRAF1 led to inhibition of the activity of NF-κB. Given the fact that the activation of NF-κB played a facilitating role in IR, the phosphorylation of Akt and GSK3β was also analyzed. We found that depletion of TRAF1 markedly reversed PA-induced attenuation of the phosphorylation of Akt and GSK3β in the cells. The accumulation of lipid droplets in hepatocyte and expression of two key gluconeogenic enzymes, PEPCK and G6Pase, were also determined and found to display a similar tendency with the phosphorylation of Akt and GSK3β. Glucose uptake assay indicated that knocking down TRAF1 blocked the effect of PA on the suppression of glucose uptake. These data implicated that TRAF1 knockdown might alleviate PA-induced IR in HepG2 cells through NF-κB pathway.

Neil2-null Mice Accumulate Oxidized DNA Bases in the Transcriptionally Active Sequences of the Genome and Are Susceptible to Innate Inflammation

Why mammalian cells possess multiple DNA glycosylases (DGs) with overlapping substrate ranges for repairing oxidatively damaged bases via the base excision repair (BER) pathway is a long-standing question. To determine the biological role of these DGs, null animal models have been generated. Here, we report the generation and characterization of mice lacking Neil2 (Nei-like 2). As in mice deficient in each of the other four oxidized base-specific DGs (OGG1, NTH1, NEIL1, and NEIL3), Neil2-null mice show no overt phenotype. However, middle-aged to old Neil2-null mice show the accumulation of oxidative genomic damage, mostly in the transcribed regions. Immuno-pulldown analysis from wild-type (WT) mouse tissue showed the association of NEIL2 with RNA polymerase II, along with Cockayne syndrome group B protein, TFIIH, and other BER proteins. Chromatin immunoprecipitation analysis from mouse tissue showed co-occupancy of NEIL2 and RNA polymerase II only on the transcribed genes, consistent with our earlier in vitro findings on NEIL2's role in transcription-coupled BER. This study provides the first in vivo evidence of genomic region-specific repair in mammals. Furthermore, telomere loss and genomic instability were observed at a higher frequency in embryonic fibroblasts from Neil2-null mice than from the WT. Moreover, Neil2-null mice are much more responsive to inflammatory agents than WT mice. Taken together, our results underscore the importance of NEIL2 in protecting mammals from the development of various pathologies that are linked to genomic instability and/or inflammation. NEIL2 is thus likely to play an important role in long term genomic maintenance, particularly in long-lived mammals such as humans.

Analysis of the TGFβ-induced program in primary airway epithelial cells shows essential role of NF-κB/RelA signaling network in type II epithelial mesenchymal transition

Background

The airway epithelial cell plays a central role in coordinating the pulmonary response to injury and inflammation. Here, transforming growth factor-β (TGFβ) activates gene expression programs to induce stem cell-like properties, inhibit expression of differentiated epithelial adhesion proteins and express mesenchymal contractile proteins. This process is known as epithelial mesenchymal transition (EMT); although much is known about the role of EMT in cellular metastasis in an oncogene-transformed cell, less is known about Type II EMT, that occurring in normal epithelial cells. In this study, we applied next generation sequencing (RNA-Seq) in primary human airway epithelial cells to understand the gene program controlling Type II EMT and how cytokine-induced inflammation modifies it.

Results

Generalized linear modeling was performed on a two-factor RNA-Seq experiment of 6 treatments of telomerase immortalized human small airway epithelial cells (3 replicates). Using a stringent cut-off, we identified 3,478 differentially expressed genes (DEGs) in response to EMT. Unbiased transcription factor enrichment analysis identified three clusters of EMT regulators, one including SMADs/TP63 and another NF-κB/RelA. Surprisingly, we also observed 527 of the EMT DEGs were also regulated by the TNF-NF-κB/RelA pathway. This Type II EMT program was compared to Type III EMT in TGFβ stimulated A549 alveolar lung cancer cells, revealing significant functional differences. Moreover, we observe that Type II EMT modifies the outcome of the TNF program, reducing IFN signaling and enhancing integrin signaling. We confirmed experimentally that TGFβ-induced the NF-κB/RelA pathway by observing a 2-fold change in NF-κB/RelA nuclear translocation. A small molecule IKK inhibitor blocked TGFβ-induced core transcription factor (SNAIL1, ZEB1 and Twist1) and mesenchymal gene (FN1 and VIM) expression.

Conclusions

These data indicate that NF-κB/RelA controls a SMAD-independent gene network whose regulation is required for initiation of Type II EMT. Type II EMT dramatically affects the induction and kinetics of TNF-dependent gene networks.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1707-x) contains supplementary material, which is available to authorized users.

ATM regulates NF-κB-dependent immediate-early genes via RelA Ser 276 phosphorylation coupled to CDK9 promoter recruitment

Ataxia-telangiectasia mutated (ATM), a member of the phosphatidylinositol 3 kinase-like kinase family, is a master regulator of the double strand DNA break-repair pathway after genotoxic stress. Here, we found ATM serves as an essential regulator of TNF-induced NF-kB pathway. We observed that TNF exposure of cells rapidly induced DNA double strand breaks and activates ATM. TNF-induced ROS promote nuclear IKKγ association with ubiquitin and its complex formation with ATM for nuclear export. Activated cytoplasmic ATM is involved in the selective recruitment of the E3-ubiquitin ligase β-TrCP to phospho-IκBα proteosomal degradation. Importantly, ATM binds and activates the catalytic subunit of protein kinase A (PKAc), ribosmal S6 kinase that controls RelA Ser 276 phosphorylation. In ATM knockdown cells, TNF-induced RelA Ser 276 phosphorylation is significantly decreased. We further observed decreased binding and recruitment of the transcriptional elongation complex containing cyclin dependent kinase-9 (CDK9; a kinase necessary for triggering transcriptional elongation) to promoters of NF-κB-dependent immediate-early cytokine genes, in ATM knockdown cells. We conclude that ATM is a nuclear damage-response signal modulator of TNF-induced NF-κB activation that plays a key scaffolding role in IκBα degradation and RelA Ser 276 phosphorylation. Our study provides a mechanistic explanation of decreased innate immune response associated with A-T mutation.

Proteomic analysis of A2780/S ovarian cancer cell response to the cytotoxic organogold(III) compound Aubipy(c)

Aubipyc is an organogold(III) compound endowed with encouraging anti-proliferative properties in vitro that is being evaluated pre-clinically as a prospective anticancer agent. A classical proteomic approach is exploited here to elucidate the mechanisms of its biological actions in A2780 human ovarian cancer cells. Based on 2-D gel electrophoresis separation and subsequent mass spectrometry identification, a considerable number of differentially expressed proteins were highlighted in A2780 cancer cells treated with Aubipyc. Bioinformatic analysis of the groups of up-regulated and down-regulated proteins pointed out that Aubipyc primarily perturbs mitochondrial processes and the glycolytic pathway. Notably, some major alterations in the glycolytic pathway were validated through Western blot and metabolic investigations.

BIOLOGICAL SIGNIFICANCE

This is the first proteomic analysis regarding Aubipyc cytotoxicity in A2780/S ovarian cancer cell line. Aubipyc is a promising gold(III) compound which manifests an appreciable cytotoxicity toward the cell line A2780, being able to overcome resistance to platinum. The proteomic study revealed for Aubipyc different cellular alterations with respect to cisplatin as well as to other gold compound such as auranofin. Remarkably, the bioinformatic analysis of proteomic data pointed out that Aubipyc treatment affected, directly or indirectly, several glycolytic enzymes. These data suggest a new mechanism of action for this gold drug and might have an impact on the use of gold-based drug in cancer treatment.

Cisplatin-induced epigenetic activation of miR-34a sensitizes bladder cancer cells to chemotherapy

BACKGROUND

Accumulating evidence suggests a tumor suppressive role for miR-34a in human carcinogenesis. However, its precise biological role remains largely elusive. This study aimed to reveal the association of the miR-34a expression and its modulation of sensitivity to cisplatin in muscle-invasive bladder cancer (MIBC).

METHODS

miR-34a expression in MIBC cell lines and patient tissues was investigated using qPCR. The methylation analysis of miR-34a promoter region was performed by MassARRAY. Synthetic short single or double stranded RNA oligonucleotides and lentiviral vector were used to regulate miR-34a expression in MIBC cells to investigate its function in vitro and in vivo.

RESULTS

miR-34a expression was frequently decreased in MIBC tissues and cell lines through promoter hypermethylation while it was epigenetically increased in MIBC cells following cisplatin treatment. Increased miR-34a expression significantly sensitized MIBC cells to cisplatin and inhibited the tumorigenicity and proliferation of cancer cells in vitro and in vivo. Furthermore, we identified CD44 as being targeted by miR-34a in MIBC cells following cisplatin treatment, and increased CD44 expression could efficiently reverse the effect of miR-34a on MIBC cell proliferation, colongenic potential and chemosensitivity.

CONCLUSIONS

Cisplatin-based chemotherapy induced demethylation of miR-34a promoter and increased miR-34a expression, which in turn sensitized MIBC cells to cisplatin and decreased the tumorigenicity and proliferation of cancer cells that by reducing the production of CD44.

Non-Canonical NF-κB Signaling Initiated by BAFF Influences B Cell Biology at Multiple Junctures

It has been more than a decade since it was recognized that the nuclear factor of kappa light polypeptide gene enhancer in B cells (NF-κB) transcription factor family was activated by two distinct pathways: the canonical pathway involving NF-κB1 and the non-canonical pathway involving NF-κB2. During this time a great deal of evidence has been amassed on the ligands and receptors that activate these pathways, the cytoplasmic adapter molecules involved in transducing the signals from receptors to nucleus, and the resulting physiological outcomes within body tissues. In contrast to NF-κB1 signaling, which can be activated by a wide variety of receptors, the NF-κB2 pathway is typically only activated by a subset of receptor and ligand pairs belonging to the tumor necrosis factor (TNF) family. Amongst these is B cell activating factor of the TNF family (BAFF) and its receptor BAFFR. Whilst BAFF is produced by many cell types throughout the body, BAFFR expression appears to be restricted to the hematopoietic lineage and B cells in particular. For this reason, the main physiological outcomes of BAFF mediated NF-κB2 activation are confined to B cells. Indeed BAFF mediated NF-κB2 signaling contributes to peripheral B cell survival and maturation as well as playing a role in antibody responses and long term maintenance plasma cells. Thus the importance BAFF and NF-κB2 permeates the entire B cell lifespan and impacts on this important component of the immune system in a variety of ways.

Systems approaches to modeling chronic mucosal inflammation

The respiratory mucosa is a major coordinator of the inflammatory response in chronic airway diseases, including asthma and chronic obstructive pulmonary disease (COPD). Signals produced by the chronic inflammatory process induce epithelial mesenchymal transition (EMT) that dramatically alters the epithelial cell phenotype. The effects of EMT on epigenetic reprogramming and the activation of transcriptional networks are known, its effects on the innate inflammatory response are underexplored. We used a multiplex gene expression profiling platform to investigate the perturbations of the innate pathways induced by TGF β in a primary airway epithelial cell model of EMT. EMT had dramatic effects on the induction of the innate pathway and the coupling interval of the canonical and noncanonical NF- κ B pathways. Simulation experiments demonstrate that rapid, coordinated cap-independent translation of TRAF-1 and NF- κ B2 is required to reduce the noncanonical pathway coupling interval. Experiments using amantadine confirmed the prediction that TRAF-1 and NF- κ B2/p100 production is mediated by an IRES-dependent mechanism. These data indicate that the epigenetic changes produced by EMT induce dynamic state changes of the innate signaling pathway. Further applications of systems approaches will provide understanding of this complex phenotype through deterministic modeling and multidimensional (genomic and proteomic) profiling.

NF-κB and Rheumatoid Arthritis: Will Understanding Genetic Risk Lead to a Therapeutic Reward?

NF-κB has long been known to play an important role in autoimmune diseases such as rheumatoid arthritis (RA). Indeed, as our understanding of how NF-κB is utilized has increased, we have been hard put to find a process not associated with this transcription factor family in some way. However, new data originating, in part, from genome-wide association studies have demonstrated that very specific alterations in components of the NF-κB pathway are sufficient to confer increased risk of developing disease. Here we review the data which have identified specific components of the NF-κB pathway, and consider what is known of their mechanisms of action and how these mechanisms might play into the disease process. In addition, the use of genetic information to predict RA is considered.