Bcl3 Phosphorylation by Akt, Erk2, and IKK Is Required for Its Transcriptional Activity

IL-10 dependent adaptation allows macrophages to adjust inflammatory responses to TLR4 stimulation history

During an infection, innate immune cells must adjust nature and strength of their responses to changing pathogen abundances. To determine how stimulation of the pathogen sensing TLR4 shapes subsequent macrophage responses, we systematically varied priming and restimulation concentrations of its ligand KLA. We find that different priming strengths have very distinct effects at multiple stages of the signaling response, including receptor internalization, MAPK activation, cytokine and chemokine production, and nuclear translocation and chromatin association of NFκB and IκB members. In particular, restimulation-induced TNF-α production required KLA doses equal to or greater than those used for prior exposure, indicating that macrophages can detect and adaptively respond to changing TLR4 stimuli. Interestingly, while such adaptation was dependent on the anti-inflammatory cytokine IL-10, exogenous concentrations of IL-10 corresponding to those secreted after strong priming did not exert suppressive effects on TNF-α without such prior priming, confirming the critical role of TLR4 stimulation history.

MEK-mediated CHPF2 phosphorylation promotes colorectal cancer cell proliferation and metastasis by activating NF-κB signaling

The cytokine tumor necrosis factor (TNF) plays a crucial role in the proliferation and metastasis of colorectal cancer (CRC) cells, but the underlying mechanisms remain poorly understood. Here, we report that chondroitin polymerizing factor 2 (CHPF2) promotes CRC cell proliferation and metastasis mediated by TNF, independently of its enzymatic activity. CHPF2 is highly expressed in CRC, and its elevated expression is associated with poor prognosis of CRC patients. Mechanistically, upon TNF stimulation, CHPF2 is phosphorylated at the T588 residue by MEK, enabling CHPF2 to interact with both TAK1 and IKKα. This interaction enhances the binding of TAK1 and IKKα, leading to increased phosphorylation of the IKK complex and activation of NF-κB signaling. As a result, the expression of early growth factors (EGR1) is upregulated to promote CRC cell proliferation and metastasis. In contrast, introduction of a phospho-deficient T588A mutation in CHPF2 weakened the interaction between CHPF2 and TAK1, thus impairing NF-κB signaling. CHPF2 T588A mutation reduced the ability of CHPF2 to promote the proliferation and metastasis of CRC in vitro and in vivo. Furthermore, the NF-κB RELA subunit promotes CHPF2 expression, further amplifying TNF-induced NF-κB signaling activation. These findings identify a moonlighting function of CHPF2 in promoting tumor cell proliferation and metastasis and provide insights into the mechanism by which CHPF2 amplifies TNF-mediated NF-κB signaling activation. Our study provides a molecular basic for the development of therapeutic strategies for CRC treatment.

Multifaceted roles for BCL3 in cancer: a proto-oncogene comes of age

In the early 1990's a group of unrelated genes were identified from the sites of recurring translocations in B-cell lymphomas. Despite sharing the nomenclature 'Bcl', and an association with blood-borne cancer, these genes have unrelated functions. Of these genes, BCL2 is best known as a key cancer target involved in the regulation of caspases and other cell viability mechanisms. BCL3 on the other hand was originally identified as a non-canonical regulator of NF-kB transcription factor pathways - a signaling mechanism associated with important cell outcomes including many of the hallmarks of cancer. Most of the early investigations into BCL3 function have since focused on its role in NF-kB mediated cell proliferation, inflammation/immunity and cancer. However, recent evidence is coming to light that this protein directly interacts with and modulates a number of other signaling pathways including DNA damage repair, WNT/β-catenin, AKT, TGFβ/SMAD3 and STAT3 - all of which have key roles in cancer development, metastatic progression and treatment of solid tumours. Here we review the direct evidence demonstrating BCL3's central role in a transcriptional network of signaling pathways that modulate cancer biology and treatment response in a range of solid tumour types and propose common mechanisms of action of BCL3 which may be exploited in the future to target its oncogenic effects for patient benefit.

Role of the redox state of the Pirin-bound cofactor on interaction with the master regulators of inflammation and other pathways

Persistent cellular stress induced perpetuation and uncontrolled amplification of inflammatory response results in a shift from tissue repair toward collateral damage, significant alterations of tissue functions, and derangements of homeostasis which in turn can lead to a large number of acute and chronic pathological conditions, such as chronic heart failure, atherosclerosis, myocardial infarction, neurodegenerative diseases, diabetes, rheumatoid arthritis, and cancer. Keeping the vital role of balanced inflammation in maintaining tissue integrity in mind, the way to combating inflammatory diseases may be through identification and characterization of mediators of inflammation that can be targeted without hampering normal body function. Pirin (PIR) is a non-heme iron containing protein having two different conformations depending on the oxidation state of the iron. Through exploration of the Pirin interactome and using molecular docking approaches, we identified that the Fe2+-bound Pirin directly interacts with BCL3, NFKBIA, NFIX and SMAD9 with more resemblance to the native binding pose and higher affinity than the Fe3+-bound form. In addition, Pirin appears to have a function in the regulation of inflammation, the transition between the canonical and non-canonical NF-κB pathways, and the remodeling of the actin cytoskeleton. Moreover, Pirin signaling appears to have a critical role in tumor invasion and metastasis, as well as metabolic and neuro-pathological complications. There are regulatory variants in PIR that can influence expression of not only PIR but also other genes, including VEGFD and ACE2. Disparity exists between South Asian and European populations in the frequencies of variant alleles at some of these regulatory loci that may lead to differential occurrence of Pirin-mediated pathogenic conditions.

The potential mechanism of Choulingdan mixture in improving acute lung injury based on HPLC-Q-TOF-MS, network pharmacology and in vivo experiments

Choulingdan mixture (CLDM) is an empirical clinical prescription for the adjuvant treatment of acute lung injury (ALI). CLDM has been used for almost 30 years in the clinic. However, its mechanism for improving ALI still needs to be investigated. In this study, high-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (HPLC-Q-TOF-MS/MS) was applied to characterize the overall chemical composition of CLDM. A total of 93 ingredients were characterized, including 25 flavonoids, 20 organic acids, 11 saponins, nine terpenoids, seven tannins and 21 other compounds. Then network pharmacology was applied to predict the potential bioactive components, target genes and signaling pathways of CLDM in improving ALI. Additionally, molecular docking was performed to demonstrate the interaction between the active ingredients and the disease targets. Finally, animal experiments further confirmed that CLDM significantly inhibits pulmonary inflammation, pulmonary edema and oxidative stress in lipopolysaccharide-induced ALI mice by inhibiting the PI3K-AKT signaling pathway. This study enhanced the amount and accuracy of compounds of CLDM and provided new insights into CLDM preventing and treating ALI.

NF-κB in monocytes and macrophages - an inflammatory master regulator in multitalented immune cells

Nuclear factor κB (NF-κB) is a dimeric transcription factor constituted by two of five protein family members. It plays an essential role in inflammation and immunity by regulating the expression of numerous chemokines, cytokines, transcription factors, and regulatory proteins. Since NF-κB is expressed in almost all human cells, it is important to understand its cell type-, tissue-, and stimulus-specific roles as well as its temporal dynamics and disease-specific context. Although NF-κB was discovered more than 35 years ago, many questions are still unanswered, and with the availability of novel technologies such as single-cell sequencing and cell fate-mapping, new fascinating questions arose. In this review, we will summarize current findings on the role of NF-κB in monocytes and macrophages. These innate immune cells show high plasticity and dynamically adjust their effector functions against invading pathogens and environmental cues. Their versatile functions can range from antimicrobial defense and antitumor immune responses to foam cell formation and wound healing. NF-κB is crucial for their activation and balances their phenotypes by finely coordinating transcriptional and epigenomic programs. Thereby, NF-κB is critically involved in inflammasome activation, cytokine release, and cell survival. Macrophage-specific NF-κB activation has far-reaching implications in the development and progression of numerous inflammatory diseases. Moreover, recent findings highlighted the temporal dynamics of myeloid NF-κB activation and underlined the complexity of this inflammatory master regulator. This review will provide an overview of the complex roles of NF-κB in macrophage signal transduction, polarization, inflammasome activation, and cell survival.

Structures of NF-κB p52 homodimer-DNA complexes rationalize binding mechanisms and transcription activation

The mammalian NF-κB p52:p52 homodimer together with its cofactor Bcl3 activates transcription of κB sites with a central G/C base pair (bp), while it is inactive toward κB sites with a central A/T bp. To understand the molecular basis for this unique property of p52, we have determined the crystal structures of recombinant human p52 protein in complex with a P-selectin(PSel)-κB DNA (5'-GGGGTGACCCC-3') (central bp is underlined) and variants changing the central bp to A/T or swapping the flanking bp. The structures reveal a nearly two-fold widened minor groove in the central region of the DNA as compared to all other currently available NF-κB-DNA complex structures, which have a central A/T bp. Microsecond molecular dynamics (MD) simulations of free DNAs and p52 bound complexes reveal that free DNAs exhibit distinct preferred conformations, and p52:p52 homodimer induces the least amount of DNA conformational changes when bound to the more transcriptionally active natural G/C-centric PSel-κB, but adopts closed conformation when bound to the mutant A/T and swap DNAs due to their narrowed minor grooves. Our binding assays further demonstrate that the fast kinetics favored by entropy is correlated with higher transcriptional activity. Overall, our studies have revealed a novel conformation for κB DNA in complex with NF-κB and pinpoint the importance of binding kinetics, dictated by DNA conformational and dynamic states, in controlling transcriptional activation for NF-κB.

Vitamin D3 reverses the transcriptional profile of offspring CD4+ T lymphocytes exposed to intrauterine inflammation

Chorioamnionitis profoundly influences multiple fetal organs as well as the immune system. Maternal vitamin D (VitD) supplementation may modulate the immune function of offspring. Here, we sought to uncover the immunomodulatory potential of intrauterine inflammation and VitD in offspring CD4⁺ T cells. Pregnant C57BL/6 mice were treated with intrauterine lipopolysaccharide (LPS) injections, with or without VitD. Splenic CD4⁺ T cells were negatively selected using anti-biotin microbeads at 28 days after birth. Differentially expressed genes (DEGs) in the offspring CD4⁺ T cells were identified via RNA sequencing. In total, 181 DEGs induced by LPS exposure were identified in offspring CD4⁺ T cells. Furthermore, 2461 DEGs were detected after VitD supplementation in addition to LPS exposure. VitD supplementation showed an unexpected ability to counteract the LPS-induced transcriptional responses. VitD supplementation downregulated lymphocyte differentiation (GO: 0030098) and lymphocyte activation (GO: 0046649), and upregulated the responses to viruses (GO: 0009615) and bacteria (GO:0009617) in offspring CD4⁺ T cells with intrauterine LPS exposure. In addition, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that several pathways, including the T cell receptor signaling pathway, the mitogen-activated protein kinase (MAPK) signaling pathway, Th17 cell differentiation, and autophagy, were downregulated by intrauterine VitD intervention following LPS exposure. Subsequently, we confirmed the counteracting effect of VitD against LPS on the expression of several genes (Insr, Foxo1, and Peli1) using qRT-PCR and western blot analyses. We also demonstrated that intrauterine VitD supplementation interferes with offspring Th17 cell differentiation induced by intrauterine LPS exposure. Our study revealed that VitD reverses the transcriptional and Th17 differential profiles of offspring CD4⁺ T lymphocytes induced by intrauterine LPS, and indicated the contribution of maternal VitD supplementation to immune protection in offspring affected by intrauterine inflammation.

Noncanonical NF-κB factor p100/p52 regulates homologous recombination and modulates sensitivity to DNA-damaging therapy

Homologous recombination (HR) serves multiple roles in DNA repair that are essential for maintaining genomic stability, including double-strand DNA break (DSB) repair. The central HR protein, RAD51, is frequently overexpressed in human malignancies, thereby elevating HR proficiency and promoting resistance to DNA-damaging therapies. Here, we find that the non-canonical NF-κB factors p100/52, but not RelB, control the expression of RAD51 in various human cancer subtypes. While p100/p52 depletion inhibits HR function in human tumor cells, it does not significantly influence the proficiency of non-homologous end joining, the other key mechanism of DSB repair. Clonogenic survival assays were performed using a pair DLD-1 cell lines that differ only in their expression of the key HR protein BRCA2. Targeted silencing of p100/p52 sensitizes the HR-competent cells to camptothecin, while sensitization is absent in HR-deficient control cells. These results suggest that p100/p52-dependent signaling specifically controls HR activity in cancer cells. Since non-canonical NF-κB signaling is known to be activated after various forms of genomic crisis, compensatory HR upregulation may represent a natural consequence of DNA damage. We propose that p100/p52-dependent signaling represents a promising oncologic target in combination with DNA-damaging treatments.

Molecular Signature of Neuroinflammation Induced in Cytokine-Stimulated Human Cortical Spheroids

Crucial in the pathogenesis of neurodegenerative diseases is the process of neuroinflammation that is often linked to the pro-inflammatory cytokines Tumor necrosis factor alpha (TNFα) and Interleukin-1beta (IL-1β). Human cortical spheroids (hCSs) constitute a valuable tool to study the molecular mechanisms underlying neurological diseases in a complex three-dimensional context. We recently designed a protocol to generate hCSs comprising all major brain cell types. Here we stimulate these hCSs for three time periods with TNFα and with IL-1β. Transcriptomic analysis reveals that the main process induced in the TNFα- as well as in the IL-1β-stimulated hCSs is neuroinflammation. Central in the neuroinflammatory response are endothelial cells, microglia and astrocytes, and dysregulated genes encoding cytokines, chemokines and their receptors, and downstream NFκB- and STAT-pathway components. Furthermore, we observe sets of neuroinflammation-related genes that are specifically modulated in the TNFα-stimulated and in the IL-1β-stimulated hCSs. Together, our results help to molecularly understand human neuroinflammation and thus a key mechanism of neurodegeneration.

Bcl-3: A Double-Edged Sword in Immune Cells and Inflammation

The NF-κB transcription factor family controls the transcription of many genes and regulates a number of pivotal biological processes. Its activity is regulated by the IκB family of proteins. Bcl-3 is an atypical member of the IκB protein family that regulates the activity of nuclear factor NF-κB. It can promote or inhibit the expression of NF-κB target genes according to the received cell type and stimulation, impacting various cell functions, such as proliferation and differentiation, induction of apoptosis and immune response. Bcl-3 is also regarded as an environment-dependent cell response regulator that has dual roles in the development of B cells and the differentiation, survival and proliferation of Th cells. Moreover, it also showed a contradictory role in inflammation. At present, in addition to the work aimed at studying the molecular mechanism of Bcl-3, an increasing number of studies have focused on the effects of Bcl-3 on inflammation, immunity and malignant tumors in vivo. In this review, we focus on the latest progress of Bcl-3 in the regulation of the NF-κB pathway and its extensive physiological role in inflammation and immune cells, which may help to provide new ideas and targets for the early diagnosis or targeted treatment of various inflammatory diseases, immunodeficiency diseases and malignant tumors.

BCL3 expression is strongly associated with the occurrence of breast cancer relapse under tamoxifen treatment in a retrospective cohort study

Patients with estrogen receptor positive breast cancer are usually receiving an anti-estrogen therapy by either aromatase inhibitors or selective estrogen receptor mediators such as tamoxifen. Nevertheless, acquired resistance to tamoxifen under treatment frequently hampers therapy. One proposed explanation for this phenomenon is the interaction of the tumor cells with cells of the tumor microenvironment via the Insulin-like growth factor RNA binding protein 5/B-cell lymphoma 3 (IGFBP5/BCL3) axis. Here we investigated whether a high expression of BCL3 either cytoplasmic or nuclear is associated with the occurrence of a relapse under anti-estrogen therapy in patients. Formaldehyde-fixed, paraffin-embedded samples of 180 breast cancer patients were analyzed for BCL3 expression by immunohistochemistry. An immunoreactive score (IRS) was calculated from staining intensity in cytoplasm and nucleus as well as the percentage of positive tumor cells. These scores were correlated with clinico-pathological parameters using cross-tabulation analysis and patients’ relapse free and overall survival by Kaplan–Meier analysis and Cox regression. A tamoxifen-adapted MCF-7 derived cell line was investigated for BCL3 localization by immunofluorescence. The cytosolic BCL3-IRS significantly correlated with the proliferation marker Ki-67, and with the occurrence of a relapse under tamoxifen treatment. Nuclear score correlated only with tamoxifen-relapse. In survival analysis, both scores were highly significant prognostic factors for relapse free, but not for overall survival. This was especially obvious for estrogen receptor positive and HER2/NEU negative cases as well as lobular breast cancer. Tamoxifen-treated, but not aromatase-treated patients had a poor survival when BCL3 scores were high. A tamoxifen adapted cell line exhibited a reduced expression and mainly nuclear localization of BCL3, compared to the parental estrogen receptor positive cell-line MCF-7. Altogether, these data strongly support a function of BCL3 in tamoxifen resistance and its potential use as a predictive biomarker for tamoxifen resistance.

Biological effects and regulation of IGFBP5 in breast cancer

The insulin-like growth factor receptor (IGF1R) pathway plays an important role in cancer progression. In breast cancer, the IGF1R pathway is linked to estrogen-dependent signaling. Regulation of IGF1R activity is complex and involves the actions of its ligands IGF1 and IGF2 and those of IGF-binding proteins (IGFBPs). Six IGFBPs are known that share the ability to form complexes with the IGFs, by which they control the bioavailability of these ligands. Besides, each of the IGFBPs have specific features. In this review, the focus lies on the biological effects and regulation of IGFBP5 in breast cancer. In breast cancer, estrogen is a critical regulator of IGFBP5 transcription. It exerts its effect through an intergenic enhancer loop that is part of the chromosomal breast cancer susceptibility region 2q35. The biological effects of IGFBP5 depend upon the cellular context. By inhibiting or promoting IGF1R signaling, IGFBP5 can either act as a tumor suppressor or promoter. Additionally, IGFBP5 possesses IGF-independent activities, which contribute to the complexity by which IGFBP5 interferes with cancer cell behavior.

Origin of the Functional Distinctiveness of NF-κB/p52

The transcription regulators of the NF-κB family have emerged as a critical factor affecting the function of various adult tissues. The NF-κB family transcription factors are homo- and heterodimers made up of five monomers (p50, p52, RelA, cRel and RelB). The family is distinguished by sequence homology in their DNA binding and dimerization domains, which enables them to bind similar DNA response elements and participate in similar biological programs through transcriptional activation and repression of hundreds of genes. Even though the family members are closely related in terms of sequence and function, they all display distinct activities. In this review, we discuss the sequence characteristics, protein and DNA interactions, and pathogenic involvement of one member of family, NF-κB/p52, relative to that of other members. We pinpoint the small sequence variations within the conserved region that are mostly responsible for its distinct functional properties.

Bcl-3 promotes TNF-induced hepatocyte apoptosis by regulating the deubiquitination of RIP1

Tumor necrosis factor-α (TNF) is described as a main regulator of cell survival and apoptosis in multiple types of cells, including hepatocytes. Dysregulation in TNF-induced apoptosis is associated with many autoimmune diseases and various liver diseases. Here, we demonstrated a crucial role of Bcl-3, an IκB family member, in regulating TNF-induced hepatic cell death. Specifically, we found that the presence of Bcl-3 promoted TNF-induced cell death in the liver, while Bcl-3 deficiency protected mice against TNF/D-GalN induced hepatoxicity and lethality. Consistently, Bcl-3-depleted hepatic cells exhibited decreased sensitivity to TNF-induced apoptosis when stimulated with TNF/CHX. Mechanistically, the in vitro results showed that Bcl-3 interacted with the deubiquitinase CYLD to synergistically switch the ubiquitination status of RIP1 and facilitate the formation of death-inducing Complex II. This complex further resulted in activation of the caspase cascade to induce apoptosis. By revealing this novel role of Bcl-3 in regulating TNF-induced hepatic cell death, this study provides a potential therapeutic target for liver diseases caused by TNF-related apoptosis.

Transcription Coactivator BCL3 Acts as a Potential Regulator of Lipid Metabolism Through the Effects on Inflammation

Background and Purpose

Transcriptional coactivator B-cell lymphoma-3 (BCL3) is a member of the IκB family of NF-κB inhibitors and regulates the activity of the NF-κB pathway. However, the relationship between BCL3 and lipid metabolism remains unclear. The present study investigates the effects of BCL3 in immune and metabolism in obese mice.

Animals and Methods

Construct Bcl3-KO mice through CRISPR/Cas9 technology. Obesity model was induced in Bcl3-KO mice by feeding a high-fat diet for 16 weeks, and some metabolic-related indicators were analysed.

Results

The results showed that the KO mice gained significantly less body weight on a high fat diet without a change in food intake. There was significant improvement in hepatic steatosis and adipose tissue hypertrophy in KO mice. The expression of SREBP1 and its downstream fatty acid synthetase FAS and ACC were down-regulated in KO mice, and the inflammation in adipose tissue and liver was further reduced.

Conclusion

These results suggest that BCL3 may be a novel factor in regulating lipid metabolism in the development of obesity.

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.

SUMO conjugation susceptibility of Akt/protein kinase B affects the expression of the pluripotency transcription factor Nanog in embryonic stem cells

Akt/PKB is a kinase involved in the regulation of a wide variety of cell processes. Its activity is modulated by diverse post-translational modifications (PTMs). Particularly, conjugation of the small ubiquitin-related modifier (SUMO) to this kinase impacts on multiple cellular functions, such as proliferation and splicing. In embryonic stem (ES) cells, this kinase is key for pluripotency maintenance. Among other functions, Akt is known to promote the expression of Nanog, a central pluripotency transcription factor (TF). However, the relevance of this specific PTM of Akt has not been previously analyzed in this context. In this work, we study the effect of Akt1 variants with differential SUMOylation susceptibility on the expression of Nanog. Our results demonstrate that both, the Akt1 capability of being modified by SUMO conjugation and a functional SUMO conjugase activity are required to induce Nanog gene expression. Likewise, we found that the common oncogenic E17K Akt1 mutant affected Nanog expression in ES cells also in a SUMOylatability dependent manner. Interestingly, this outcome takes places in ES cells but not in a non-pluripotent heterologous system, suggesting the presence of a crucial factor for this induction in ES cells. Remarkably, the two major candidate factors to mediate this induction, GSK3-β and Tbx3, are non-essential players of this effect, suggesting a complex mechanism probably involving non-canonical pathways. Furthermore, we found that Akt1 subcellular distribution does not depend on its SUMOylatability, indicating that Akt localization has no influence on the effect on Nanog, and that besides the membrane localization of E17K Akt mutant, SUMOylation is also required for its hyperactivity. Our results highlight the impact of SUMO conjugation in the function of a kinase relevant for a plethora of cellular processes, including the control of a key pluripotency TF.

Bcl3 Couples Cancer Stem Cell Enrichment With Pancreatic Cancer Molecular Subtypes

BACKGROUND & AIMS

The existence of different subtypes of pancreatic ductal adenocarcinoma (PDAC) and their correlation with patient outcome have shifted the emphasis on patient classification for better decision-making algorithms and personalized therapy. The contribution of mechanisms regulating the cancer stem cell (CSC) population in different subtypes remains unknown.

METHODS

Using RNA-seq, we identified B-cell CLL/lymphoma 3 (BCL3), an atypical nf-κb signaling member, as differing in pancreatic CSCs. To determine the biological consequences of BCL3 silencing in vivo and in vitro, we generated bcl3-deficient preclinical mouse models as well as murine cell lines and correlated our findings with human cell lines, PDX models, and 2 independent patient cohorts. We assessed the correlation of bcl3 expression pattern with clinical parameters and subtypes.

RESULTS

Bcl3 was significantly down-regulated in human CSCs. Recapitulating this phenotype in preclinical mouse models of PDAC via BCL3 genetic knockout enhanced tumor burden, metastasis, epithelial to mesenchymal transition, and reduced overall survival. Fluorescence-activated cell sorting analyses, together with oxygen consumption, sphere formation, and tumorigenicity assays, all indicated that BCL3 loss resulted in CSC compartment expansion promoting cellular dedifferentiation. Overexpression of BCL3 in human PDXs diminished tumor growth by significantly reducing the CSC population and promoting differentiation. Human PDACs with low BCL3 expression correlated with increased metastasis, and BCL3-negative tumors correlated with lower survival and nonclassical subtypes.

CONCLUSIONS

We demonstrate that bcl3 impacts pancreatic carcinogenesis by restraining CSC expansion and by curtailing an aggressive and metastatic tumor burden in PDAC across species. Levels of BCL3 expression are a useful stratification marker for predicting subtype characterization in PDAC, thereby allowing for personalized therapeutic approaches.

System-wide identification and prioritization of enzyme substrates by thermal analysis

Despite the immense importance of enzyme-substrate reactions, there is a lack of general and unbiased tools for identifying and prioritizing substrate proteins that are modified by the enzyme on the structural level. Here we describe a high-throughput unbiased proteomics method called System-wide Identification and prioritization of Enzyme Substrates by Thermal Analysis (SIESTA). The approach assumes that the enzymatic post-translational modification of substrate proteins is likely to change their thermal stability. In our proof-of-concept studies, SIESTA successfully identifies several known and novel substrate candidates for selenoprotein thioredoxin reductase 1, protein kinase B (AKT1) and poly-(ADP-ribose) polymerase-10 systems. Wider application of SIESTA can enhance our understanding of the role of enzymes in homeostasis and disease, opening opportunities to investigate the effect of post-translational modifications on signal transduction and facilitate drug discovery.

ADAP Y571 Phosphorylation Is Required to Prime STAT3 for Activation in TLR4-Stimulated Macrophages

Adhesion and degranulation-promoting adapter protein (ADAP), originally identified as an essential adaptor molecule in TCR signaling and T cell adhesion, has emerged as a critical regulator in innate immune cells such as macrophages; however, its role in macrophage polarization and inflammatory responses remains unknown. In this study, we show that ADAP plays an essential role in TLR4-mediated mouse macrophage polarization via modulation of STAT3 activity. Macrophages from ADAP-deficient mice exhibit enhanced M1 polarization, expression of proinflammatory cytokines and capacity in inducing Th1 responses, but decreased levels of anti-inflammatory cytokines in response to TLR4 activation by LPS. Furthermore, overexpression of ADAP enhances, whereas loss of ADAP reduces, the LPS-mediated phosphorylation and activity of STAT3, suggesting ADAP acts as a coactivator of STAT3 activity and function. Furthermore, the coactivator function of ADAP mostly depends on the tyrosine phosphorylation at Y571 in the motif YDSL induced by LPS. Mutation of Y571 to F severely impairs the stimulating effect of ADAP on STAT3 activity and the ability of ADAP to inhibit M1-like polarization in TLR4-activated mouse macrophages. Moreover, ADAP interacts with STAT3, and loss of ADAP renders mouse macrophages less sensitive to IL-6 stimulation for STAT3 phosphorylation. Collectively, our findings revealed an additional layer of regulation of TLR4-mediated mouse macrophage plasticity whereby ADAP phosphorylation on Y571 is required to prime STAT3 for activation in TLR4-stimulated mouse macrophages.

Carcinoma-Associated Fibroblasts Promote Growth of Sox2-Expressing Breast Cancer Cells

Simple Summary

The tumor microenvironment has a strong impact on the behavior of tumor cells. One major cell type residing in the tumor microenvironment is the carcinoma-associated fibroblast (CAF). We were interested in the effect of CAFs on Sox2 (sex determining region Y (SRY)-box 2), which not only is an essential embryonal stem cell transcription factor, but also plays a role in cancer stem cell activity. We found that long-term exposure of ERα-positive breast cancer cells to the cocktail of CAF-secreted factors strongly increased Sox2 expression involving tumor-related proteins and signaling pathways. However, Sox2 was not only present in those tumor cells that express stem cell markers, but was equally abundant in other tumor cells. By being widely expressed, Sox2 may have functions in non-stem cells. In fact, Sox2 was found to regulate ERα expression, to act anti-apoptotically, to promote cellular growth and to protect cells against the anti-estrogen fulvestrant.

Abstract

CAFs (Carcinoma-associated fibroblasts) play an important role in cancer progression. For instance, they promote resistance to anti-estrogens, such as fulvestrant. Here, we show that, in ERα-positive breast cancer cell lines, the cocktail of factors secreted by CAFs (CAF-CM) induce the expression of the embryonal stem cell transcription factor Sox2 (sex determining region Y (SRY)-box 2). Long-term exposure to CAF-CM was able to give rise to very high Sox2 levels both in the absence and presence of fulvestrant. IL-6 (interleukin-6), a major component of CAF-CM, failed to raise Sox2 expression. In MCF-7 sublines established in the presence of CAF-CM, almost all cells showed Sox2 expression, whereas long-term treatment of T47D cells with CAF-CM resulted in a ~60-fold increase in the proportions of two distinct populations of Sox2 high and low expresser cells. Exposure of BT474 cells to CAF-CM raised the fraction of Sox2 high expresser cells by ~3-fold. Cell sorting based on CD44 and CD24 expression or ALDH (aldehyde dehydrogenase) activity revealed that most Sox2 high expresser cells were not CD44^hi/CD24^lo- or ALDH-positive cells suggesting that they were not CSCs (cancer stem cells), though CD44 played a role in Sox2 expression. Functionally, Sox2 was found to protect CAF-CM-treated cells against apoptosis and to allow higher growth activity in the presence of fulvestrant. Mechanistically, the key drivers of Sox2 expression was found to be STAT3 (Signal transducer and activator of transcription 3), Bcl-3 (B-cell lymphoma 3) and the PI3K (Phosphoinositide 3-kinase)/AKT pathway, whose activities/expression can all be upregulated by CAF-CM. These data suggest that CAF-CM induces Sox2 expression in non-CSCs by activating proteins involved in growth control and drug resistance, leading to higher protection against apoptosis.

Akt+ IKKα/β+ Rab5+ Signalosome Mediate the Endosomal Recruitment of Sec61 and Contribute to Cross-Presentation in Bone Marrow Precursor Cells

Cross-presentation in dendritic cells (DC) requires the endosomal relocations of internalized antigens and the endoplasmic reticulum protein Sec61. Despite the fact that endotoxin-containing pathogen and endotoxin-free antigen have different effects on protein kinase B (Akt) and I-kappa B Kinase α/β (IKKα/β) activation, the exact roles of Akt phosphorylation, IKKα or IKKβ activation in endotoxin-containing pathogen-derived cross-presentation are poorly understood. In this study, endotoxin-free ovalbumin supplemented with endotoxin was used as a model pathogen. We investigated the effects of endotoxin-containing pathogen and endotoxin-free antigen on Akt phosphorylation, IKKα/β activation, and explored the mechanisms that the endotoxin-containing pathogen orchestrating the endosomal recruitment of Sec61 of the cross-presentation in bone marrow precursor cells (BMPC). We demonstrated that endotoxin-containing pathogen and endotoxin-free antigen efficiently induced the phosphorylation of Akt-IKKα/β and Akt-IKKα, respectively. Endotoxin-containing pathogen derived Akt+ IKKα/β+ Rab5+ signalosome, together with augmented the recruitment of Sec61 toward endosome, lead to the increased cross-presentation in BMPC. Importantly, the endosomal recruitment of Sec61 was partly mediated by the formation of Akt+ IKKα/β+ signalosome. Thus, these data suggest that Akt+ IKKα/β+ Rab5+ signalosome contribute to endotoxin-containing pathogen-induced the endosomal recruitment of Sec61 and the superior efficacy of cross-presentation in BMPC.

Role of the NF-κB system in context-specific tuning of the inflammatory gene response

The canonical NF-κB pathway instructs the expression of inflammatory genes by the RelA:p50 transcription factor in response to diverse cell-activating stimuli. However, this mainstay RelA:p50 transcriptional output must also be curated so as to provide for stimulus-type-specific and cell-type-specific inflammatory responses adapted to the local tissue-microenvironment. Here, we summarize the fundamental mechanisms regulating RelA:p50-mediated gene expressions and discuss how the NF-κB system imparts specificity in the inflammatory gene program. We put forward a conceptual framework where the dynamical attributes and the composition of the nuclear NF-κB complexes cumulatively instruct context-specific inflammatory gene patterns. We propose that integrating mechanistic knowledge and systems-level analyses may offer further insights on NF-κB-mediated inflammatory gene control in the future.

The role of B-Cell Lymphoma-3 (BCL-3) in enabling the hallmarks of cancer: implications for the treatment of colorectal carcinogenesis

With its identification as a proto-oncogene in chronic lymphocytic leukaemia and central role in regulating NF-κB signalling, it is perhaps not surprising that there have been an increasing number of studies in recent years investigating the role of BCL-3 (B-Cell Chronic Lymphocytic Leukaemia/Lymphoma-3) in a wide range of human cancers. Importantly, this work has begun to shed light on our mechanistic understanding of the function of BCL-3 in tumour promotion and progression. Here, we summarize the current understanding of BCL-3 function in relation to the characteristics or traits associated with tumourigenesis, termed ‘Hallmarks of Cancer’. With the focus on colorectal cancer, a major cause of cancer related mortality in the UK, we describe the evidence that potentially explains why increased BCL-3 expression is associated with poor prognosis in colorectal cancer. As well as promoting tumour cell proliferation, survival, invasion and metastasis, a key emerging function of this proto-oncogene is the regulation of the tumour response to inflammation. We suggest that BCL-3 represents an exciting new route for targeting the Hallmarks of Cancer; in particular by limiting the impact of the enabling hallmarks of tumour promoting inflammation and cell plasticity. As BCL-3 has been reported to promote the stem-like potential of cancer cells, we suggest that targeting BCL-3 could increase the tumour response to conventional treatment, reduce the chance of relapse and hence improve the prognosis for cancer patients.

Bcl-3 inhibits lupus-like phenotypes in BL6/lpr mice

Bcl-3 is an atypical member of the IκB family that modulates NF-κB activity in nuclei. lpr mice carry the lpr mutation in Fas, resulting in functional loss of this death receptor; they serve as models for lupus erythematosus and autoimmune lymphoproliferation syndrome (ALPS). To explore the biologic roles of Bcl-3 in this disease model, we generated BL6/lpr mice lacking Bcl-3. Unlike lpr mice on an MRL background, BL6/lpr mice present with very mild lupus- or ALPS-like phenotypes. Bcl-3 KO BL6/lpr mice, however, developed severe splenomegaly, dramatically increased numbers of double negative T cells - a hallmark of human lupus, ALPS, and MRL/lpr mice - and exhibited inflammation in multiple organs, despite low levels of autoantibodies, similar to those in BL6/lpr mice. Loss of Bcl-3 specifically in T cells exacerbated select lupus-like phenotypes, specifically organ infiltration. Mechanistically, elevated levels of Tnfα in Bcl-3 KO BL6/lpr mice may promote lupus-like phenotypes, since loss of Tnfα in these mice reversed the pathology due to loss of Bcl-3. Contrary to the inhibitory functions of Bcl-3 revealed here, this regulator has also been shown to promote inflammation in different settings. Our findings highlight the profound, yet highly context-dependent roles of Bcl-3 in the development of inflammation-associated pathology.

Bcl-3 promotes Wnt signaling by maintaining the acetylation of β-catenin at lysine 49 in colorectal cancer

Wnt/β-catenin signaling plays a critical role in colorectal cancer (CRC) tumorigenesis and the homeostasis of colorectal cancer stem cells (CSCs), but its molecular mechanism remains unclear. B-cell lymphoma 3 (Bcl-3), a member of the IκB family, is overexpressed in CRC and promotes tumorigenicity. Here, we report a novel function of Bcl-3 in maintaining colorectal CSC homeostasis by activating Wnt/β-catenin signaling. Silencing Bcl-3 suppresses the self-renewal capacity of colorectal CSCs and sensitizes CRC cells to chemotherapeutic drugs through a decrease in Wnt/β-catenin signaling. Moreover, our data show that Bcl-3 is a crucial component of Wnt/β-catenin signaling and is essential for β-catenin transcriptional activity in CRC cells. Interestingly, Wnt3a increases the level and nuclear translocation of Bcl-3, which binds directly to β-catenin and enhances the acetylation of β-catenin at lysine 49 (Ac-K49-β-catenin) and transcriptional activity. Bcl-3 depletion decreases the Ac-K49-β-catenin level by increasing the level of histone deacetylase 1 to remove acetyl groups from β-catenin, thus interrupting Wnt/β-catenin activity. In CRC clinical specimens, Bcl-3 expression negatively correlates with the overall survival of CRC patients. A significantly positive correlation was found between the expression of Bcl-3 and Ac-K49-β-catenin. Collectively, our data reveal that Bcl-3 plays a crucial role in CRC chemoresistance and colorectal CSC maintenance via its modulation of the Ac-K49-β-catenin, which serves as a promising therapeutic target for CRC.

Threonine Phosphorylation of IκBζ Mediates Inhibition of Selective Proinflammatory Target Genes

Transcription factors of the NF-κB family play a crucial role for immune responses by activating the expression of chemokines, cytokines, and antimicrobial peptides involved in pathogen clearance. IκBζ, an atypical nuclear IκB protein and selective coactivator of particular NF-κB target genes, has recently been identified as an essential regulator for skin immunity. This study discovered that IκBζ is strongly induced in keratinocytes that sense the fungal glucan zymosan A. Additionally, IκBζ is essential for the optimal expression of proinflammatory genes, such as IL6, CXCL5, IL1B, or S100A9. Moreover, this study found that IκBζ was not solely regulated on the transcriptional level but also by phosphorylation events. This study identified several IκBζ phosphorylation sites, including a conserved cluster of threonine residues located in the N-terminus of the protein, which can be phosphorylated by MAPKs. Surprisingly, IκBζ phosphorylation at this threonine cluster promoted the recruitment of histone deacetylase 1 to specific target gene promoters and, thus, negatively controlled transcription. Taken together, this study proposes a model of how an antifungal response translates to the expression of proinflammatory cytokines and highlights an additional layer of complexity in the regulation of the NF-κB responses in keratinocytes.

Protein Kinase D3 promotes the cell proliferation by activating the ERK1/c-MYC axis in breast cancer

Breast cancer is the second leading death cause of cancer death for all women. Previous study suggested that Protein Kinase D3 (PRKD3) was involved in breast cancer progression. In addition, the protein level of PRKD3 in triple‐negative breast adenocarcinoma was higher than that in normal breast tissue. However, the oncogenic mechanisms of PRKD3 in breast cancer is not fully investigated. Multi‐omic data showed that ERK1/c‐MYC axis was identified as a major pivot in PRKD3‐mediated downstream pathways. Our study provided the evidence to support that the PRKD3/ERK1/c‐MYC pathway play an important role in breast cancer progression. We found that knocking out PRKD3 by performing CRISPR/Cas9 genome engineering technology suppressed phosphorylation of both ERK1 and c‐MYC but did not down‐regulate ERK1/2 expression or phosphorylation of ERK2. The inhibition of ERK1 and c‐MYC phosphorylation further led to the lower protein level of c‐MYC and then reduced the expression of the c‐MYC target genes in breast cancer cells. We also found that loss of PRKD3 reduced the rate of the cell proliferation in vitro and tumour growth in vivo, whereas ectopic (over)expression of PRKD3, ERK1 or c‐MYC in the PRKD3‐knockout breast cells reverse the suppression of the cell proliferation and tumour growth. Collectively, our data strongly suggested that PRKD3 likely promote the cell proliferation in the breast cancer cells by activating ERK1‐c‐MYC axis.

A pipeline to create predictive functional networks: application to the tumor progression of hepatocellular carcinoma

Background

Integrating genome-wide gene expression patient profiles with regulatory knowledge is a challenging task because of the inherent heterogeneity, noise and incompleteness of biological data. From the computational side, several solvers for logic programs are able to perform extremely well in decision problems for combinatorial search domains. The challenge then is how to process the biological knowledge in order to feed these solvers to gain insights in a biological study. It requires formalizing the biological knowledge to give a precise interpretation of this information; currently, very few pathway databases offer this possibility.

Results

The presented work proposes an automatic pipeline to extract automatically regulatory knowledge from pathway databases and generate novel computational predictions related to the state of expression or activity of biological molecules. We applied it in the context of hepatocellular carcinoma (HCC) progression, and evaluate the precision and the stability of these computational predictions. Our working base is a graph of 3383 nodes and 13,771 edges extracted from the KEGG database, in which we integrate 209 differentially expressed genes between low and high aggressive HCC across 294 patients. Our computational model predicts the shifts of expression of 146 initially non-observed biological components. Our predictions were validated at 88% using a larger experimental dataset and cross-validation techniques. In particular, we focus on the protein complexes predictions and show for the first time that NFKB1/BCL-3 complexes are activated in aggressive HCC. In spite of the large dimension of the reconstructed models, our analyses over the computational predictions discover a well constrained region where KEGG regulatory knowledge constrains gene expression of several biomolecules. These regions can offer interesting windows to perturb experimentally such complex systems.

Conclusion

This new pipeline allows biologists to develop their own predictive models based on a list of genes. It facilitates the identification of new regulatory biomolecules using knowledge graphs and predictive computational methods. Our workflow is implemented in an automatic python pipeline which is publicly available at https://github.com/LokmaneChebouba/key-pipeand contains as testing data all the data used in this paper.

Activator Protein-1 Transcriptional Activity Drives Soluble Micrograft-Mediated Cell Migration and Promotes the Matrix Remodeling Machinery

Impaired wound healing and tissue regeneration have severe consequences on the patient's quality of life. Micrograft therapies are emerging as promising and affordable alternatives to improve skin regeneration by enhancing the endogenous wound repair processes. However, the molecular mechanisms underpinning the beneficial effects of the micrograft treatments remain largely unknown. In this study, we identified the active protein-1 (AP-1) member Fos-related antigen-1 (Fra-1) to play a central role in the extracellular signal-regulated kinase- (ERK-) mediated enhanced cell migratory capacity of soluble micrograft-treated mouse adult fibroblasts and in the human keratinocyte cell model. Accordingly, we show that increased micrograft-dependent in vitro cell migration and matrix metalloprotease activity is abolished upon inhibition of AP-1. Furthermore, soluble micrograft treatment leads to increased expression and posttranslational phosphorylation of Fra-1 and c-Jun, resulting in the upregulation of wound healing-associated genes mainly involved in the regulation of cell migration. Collectively, our work provides insights into the molecular mechanisms behind the cell-free micrograft treatment, which might contribute to future advances in wound repair therapies.

Genome reading by the NF-κB transcription factors

The NF-κB family of dimeric transcription factors regulates transcription by selectively binding to DNA response elements present within promoters or enhancers of target genes. The DNA response elements, collectively known as κB sites or κB DNA, share the consensus 5'-GGGRNNNYCC-3' (where R, Y and N are purine, pyrimidine and any nucleotide base, respectively). In addition, several DNA sequences that deviate significantly from the consensus have been shown to accommodate binding by NF-κB dimers. X-ray crystal structures of NF-κB in complex with diverse κB DNA have helped elucidate the chemical principles that underlie target selection in vitro. However, NF-κB dimers encounter additional impediments to selective DNA binding in vivo. Work carried out during the past decades has identified some of the barriers to sequence selective DNA target binding within the context of chromatin and suggests possible mechanisms by which NF-κB might overcome these obstacles. In this review, we first highlight structural features of NF-κB:DNA complexes and how distinctive features of NF-κB proteins and DNA sequences contribute to specific complex formation. We then discuss how native NF-κB dimers identify DNA binding targets in the nucleus with support from additional factors and how post-translational modifications enable NF-κB to selectively bind κB sites in vivo.

Protein‑ and growth‑modulatory effects of carcinoma‑associated fibroblasts on breast cancer cells: Role of interleukin‑6

Carcinoma-associated fibroblasts (CAFs) secrete factors that increase the expression and/or activities of proteins in breast cancer cells and induce resistance to anti-estrogens, such as fulvestrant. A major factor is interleukin-6 (IL-6). This study demonstrated that, across estrogen receptor (ER) α-positive and -negative cell lines, recombinant human IL-6 (rhIL-6) mimicked most of the CAF-conditioned medium (CM)-induced changes in protein expression patterns; however, in most cases, it failed to recapitulate CAF-CM-triggered alterations in ERK1/2 and AKT activities. The ability of rhIL-6 to induce fulvestrant resistance was dependent upon the culture conditions. In 3D, but not in 2D cultures, rhIL-6 increased the survival of fulvestrant-treated cells, although not to the same extent as observed with CAF-CM. In 2D cultures, rhIL-6 acted in a pro-apoptotic manner and decreased the expression of ATP-binding cassette transporter G2 (ABCG2). The inhibition of the PI3K/AKT pathway had similar effects on apoptosis and ABCG2 expression, linking the failure of rhIL-6 to induce fulvestrant resistance to its inability to activate the PI3K/AKT pathway. In 3D cultures, both CAF-CM and rhIL-6 acted in an anti-apoptotic manner. These activities are likely independent on the PI3K/AKT pathway and ABCG2. Experiments on ERα-negative breast cancer cells revealed a growth-inhibitory effects of both CAF-CM and rhIL-6, which coincided with a reduction in the c-Myc level. These data suggest that IL-6 plays a role in several effects of CAF-CM, including alterations in protein expression patterns, fulvestrant resistance in 3D cultures and growth inhibition. By contrast, IL-6 is unlikely to be responsible for the CAF-CM-induced activation of the PI3K/AKT pathway and fulvestrant resistance in 2D cultures.

The DOT1L inhibitor Pinometostat decreases the host-response against infections: Considerations about its use in human therapy

Patients with acute myeloid leukemia frequently present translocations of MLL gene. Rearrangements of MLL protein (MLL-r) in complexes that contain the histone methyltransferase DOT1L are common, which elicit abnormal methylation of lysine 79 of histone H3 at MLL target genes. Phase 1 clinical studies with pinometostat (EPZ-5676), an inhibitor of DOT1L activity, demonstrated the therapeutic potential for targeting DOT1L in MLL-r leukemia patients. We previously reported that down-regulation of DOT1L increases influenza and vesicular stomatitis virus replication and decreases the antiviral response. Here we show that DOT1L inhibition also reduces Sendai virus-induced innate response and its overexpression decreases influenza virus multiplication, reinforcing the notion of DOT1L controlling viral replication. Accordingly, genes involved in the host innate response against pathogens (RUBICON, TRIM25, BCL3) are deregulated in human lung epithelial cells treated with pinometostat. Concomitantly, deregulation of some of these genes together with that of the MicroRNA let-7B, may account for the beneficial effects of pinometostat treatment in patients with MLL-r involving DOT1L. These results support a possible increased vulnerability to infection in MLL-r leukemia patients undergoing pinometostat treatment. Close follow up of infection should be considered in pinometostat therapy to reduce some severe side effects during the treatment.

BCL3 expression promotes resistance to alkylating chemotherapy in gliomas

The response of patients with gliomas to alkylating chemotherapy is heterogeneous. However, there are currently no universally accepted predictors of patient response to these agents. We identify the nuclear factor κB (NF-κB) co-regulator B cell CLL/lymphoma 3 (BCL-3) as an independent predictor of response to temozolomide (TMZ) treatment. In glioma patients with tumors that have a methylated O⁶-methylguanine DNA methyltransferase (MGMT) promoter, high BCL-3 expression was associated with a poor response to TMZ. Mechanistically, BCL-3 promoted a more malignant phenotype by inducing an epithelial-to-mesenchymal transition in glioblastomas through promoter-specific NF-κB dimer exchange. Carbonic anhydrase II (CAII) was identified as a downstream factor promoting BCL-3-mediated resistance to chemotherapy. Experiments in glioma xenograft mouse models demonstrated that the CAII inhibitor acetazolamide enhanced survival of TMZ-treated animals. Our data suggest that BCL-3 might be a useful indicator of glioma response to alkylating chemotherapy and that acetazolamide might be repurposed as a chemosensitizer for treating TMZ-resistant gliomas.

[Nucleus translocation of membrane/cytoplasm proteins in tumor cells]

Proteins are the physical basis of life and perform all kinds of life activities. Proteins have different orientations and function in different tissues. The same protein, located in different subcellular regions, can perform different and even opposite functions. Both functional and structural proteins are capable of undergoing re-localization which can directly or indirectly participate in signal transduction. Due to abnormal transduction of signals during carcinogenesis, the proteins originally expressed in the cytoplasm are translocated into the nucleus and lead to functional changes in the tumor tissue. The changes of protein localization are affected by many factors, including the interaction between proteins, expression level of proteins and the cleaved intracellular domain of transmembrane protein.

S-Like-Phase Cyclin-Dependent Kinases Stabilize the Epstein-Barr Virus BDLF4 Protein To Temporally Control Late Gene Transcription

Temporally controlled gene expression is necessary for the propagation of herpesviruses. To achieve this, herpesviruses encode several transcriptional regulators. In Epstein-Barr virus, BcRF1 associates with five viral proteins (BDLF4, BGLF3, BFRF2, BVLF1, and BDLF3.5) to form the viral late (L) gene regulatory complex, which is called the viral preinitiation complex (vPIC), on TATT-containing promoters. However, regulation of the vPIC has been largely unexplored. In this study, we performed two screens using a kinase inhibitor library and identified a series of cyclin-dependent kinase (CDK) inhibitors that downregulated the expression of L genes without any impact on viral DNA replication through destabilization of the BDLF4 protein. Knockdown of CDK2 by short hairpin RNA (shRNA) and proteasome inhibitor treatment showed that phosphorylation of the BDLF4 protein prevented ubiquitin-mediated degradation. Moreover, we demonstrated that cyclin A- and E-associated CDK2 complexes phosphorylated BDLF4 in vitro, and we identified several serine/threonine phosphorylation sites in BDLF4. Phosphoinactive and phosphomimic mutants revealed that phosphorylation at threonine 91 plays a role in stabilizing BDLF4. Therefore, our findings indicate that S-like-phase CDKs mediate the regulation of L gene expression through stabilization of the BDLF4 protein, which makes the temporal L gene expression system more robust.IMPORTANCE Late (L) genes represent more than one-third of the herpesvirus genome, suggesting that many of these genes are indispensable for the life cycle of the virus. With the exception of BCRF1, BDLF2, and BDLF3, Epstein-Barr virus L genes are transcribed by viral regulators, which are known as the viral preinitiation complex (vPIC) and the host RNA polymerase II complex. Because the vPIC is conserved in beta- and gammaherpesviruses, studying the control of viral L gene expression by the vPIC contributes to the development of drugs that specifically inhibit these processes in beta- and gammaherpesvirus infections/diseases. In this study, we demonstrated that CDK inhibitors induced destabilization of the vPIC component BDLF4, leading to a reduction in L gene expression and subsequent progeny production. Our findings suggest that CDK inhibitors may be a therapeutic option against beta- and gammaherpesviruses in combination with existing inhibitors of herpesvirus lytic replication, such as ganciclovir.

The proto-oncogene Bcl3 induces immune checkpoint PD-L1 expression, mediating proliferation of ovarian cancer cells

The proto-oncogene Bcl3 induces survival and proliferation in cancer cells; however, its function and regulation in ovarian cancer (OC) remain unknown. Here, we show that Bcl3 expression is increased in human OC tissues. Surprisingly, however, we found that in addition to promoting survival, proliferation, and migration of OC cells, Bcl3 promotes both constitutive and interferon-γ (IFN)-induced expression of the immune checkpoint molecule PD-L1. The Bcl3 expression in OC cells is further increased by IFN, resulting in increased PD-L1 transcription. The mechanism consists of an IFN-induced, Bcl3- and p300-dependent PD-L1 promoter occupancy by Lys-314/315 acetylated p65 NF-κB. Blocking PD-L1 by neutralizing antibody reduces proliferation of OC cells overexpressing Bcl3, suggesting that the pro-proliferative effect of Bcl3 in OC cells is partly mediated by PD-L1. Together, this work identifies PD-L1 as a novel target of Bcl3, and links Bcl3 to IFNγ signaling and PD-L1-mediated immune escape.

Noncanonical NF-κB in Cancer

The NF-κB pathway is a critical regulator of immune responses and is often dysregulated in cancer. Two NF-κB pathways have been described to mediate these responses, the canonical and the noncanonical. While understudied compared to the canonical NF-κB pathway, noncanonical NF-κB and its components have been shown to have effects, usually protumorigenic, in many different cancer types. Here, we review noncanonical NF-κB pathways and discuss its important roles in promoting cancer. We also discuss alternative NF-κB-independent functions of some the components of noncanonical NF-κB signaling. Finally, we discuss important crosstalk between canonical and noncanonical signaling, which blurs the two pathways, indicating that understanding the full picture of NF-κB regulation is critical to deciphering how this broad pathway promotes oncogenesis.