Overexpression Of JunB Research Articles

MEK inhibition prevents CAR-T cell exhaustion and differentiation via downregulation of c-Fos and JunB

Clinical evidence supports the notion that T cell exhaustion and terminal differentiation pose challenges to the persistence and effectiveness of chimeric antigen receptor-T (CAR-T) cells. MEK1/2 inhibitors (MEKIs), widely used in cancer treatment due to their ability to inhibit aberrant MAPK signaling, have shown potential synergistic effects when combined with immunotherapy. However, the impact and mechanisms of MEKIs on CAR-T cells remain uncertain and controversial. To address this, we conducted a comprehensive investigation to determine whether MEKIs enhance or impair the efficacy of CAR-T cells. Our findings revealed that MEKIs attenuated CAR-T cell exhaustion and terminal differentiation induced by tonic signaling and antigen stimulation, thereby improving CAR-T cell efficacy against hematological and solid tumors. Remarkably, these effects were independent of the specific scFvs and costimulatory domains utilized in CARs. Mechanistically, analysis of bulk and single-cell transcriptional profiles demonstrates that the effect of MEK inhibition was related to diminish anabolic metabolism and downregulation of c-Fos and JunB. Additionally, the overexpression of c-Fos or JunB in CAR-T cells counteracted the effects of MEK inhibition. Furthermore, our Cut-and-Tag assay revealed that MEK inhibition downregulated the JunB-driven gene profiles associated with exhaustion, differentiation, anergy, glycolysis, and apoptosis. In summary, our research unveil the critical role of the MAPK-c-Fos-JunB axis in driving CAR-T cell exhaustion and terminal differentiation. These mechanistic insights significantly broaden the potential application of MEKIs to enhance the effectiveness of CAR-T therapy.

Abstract We139: 3D Chromatin Architectures and Transcription Regulation in Diabetic Endothelial Dysfunction

Cardiovascular disease is the major cause of mortality in people with type 2 diabetes, primarily due to endothelial dysfunction. Recent studies have suggested that transcriptional reprogramming plays a central role in endothelial dysfunction, but its regulation in the context of diabetes remains poorly understood. In this study, we utilized 3D chromatin mapping analysis (H3K27ac HiChIP) to investigate the transcriptional regulation in aortic endothelial cells (db/db mice) and HUVEC cells treated with high glucose (HUVEC high-glu ). We found that these cells were characterized by a massive loss of enhancer-promoter loops, which was associated with transcriptional downregulation. Through transcription factor motif scan, ChIP-seq and ATAC-seq analysis, we uncovered that the lost loop anchors are demarcated by reduced JUNB (transcription factor) binding while their chromatin accessibility remains unchanged. Moreover, we demonstrated that overexpression of JUNB significantly restored enhancer-promoter loops lost in HUVEC high-glu and ameliorated endothelial dysfunctions both in vitro (cell scratch, Transwell), ex vivo (aorta relaxation/contraction) and in vivo (hindlimb ischemia) assays. We further showed that JUNB protein (but not RNA) expression is reduced in aortic endothelial cells (db/db), HUVEC high-glu and primary endothelial cells from diabetic patients. Through RIME (Rapid immunoprecipitation mass spectrometry of endogenous protein) assay, we identified that RBBP6 (RB Binding Protein 6, Ubiquitin Ligase) is a JUNB interacting protein in HUVEC high-glu . We further showed that overexpression of RBBP6 downregulated JUNB expression while proteasome inhibitor MG132 treatment largely abolished the inhibitory effect of RBBP6 on JUNB protein levels in normal HUVEC cells, suggesting that RPPB6 promoted JUNB degradation through ubiquitination. Notably, knockdown of RBBP6 in HUVEC high-glu significantly upregulated JUNB expression, enhancer-promoter loopings and improved endothelial dysfunction. Overall, our findings provide novel 3D chromatin insights into diabetic endothelial dysfunction and illustrate a model whereby RBBP6-mediated JUNB degradation leads to global loss of enhancer-promoter looping and transcriptional inhibition in diabetic endothelial dysfunction.

Epigallocatechin-3-gallate inhibits osteogenic differentiation of vascular smooth muscle cells through the transcription factor JunB.

Medial arterial calcification (MAC) accompanying chronic kidney disease (CKD) leads to increased vessel wall stiffness, myocardial ischemia, heart failure, and increased cardiovascular morbidity and mortality. Unfortunately, there are currently no drugs available to treat MAC. The natural polyphenol epigallocatechin-3-gallate (EGCG) has been demonstrated to protect against cardiovascular disease; however, whether EGCG supplementation inhibits MAC in CKD remains unclear. In this study, we utilize a CKD-associated MAC model to investigate the effects of EGCG on vascular calcification and elucidate the underlying mechanisms involved. Our findings demonstrate that EGCG treatment significantly reduces calcium phosphate deposition and osteogenic differentiation of VSMCs in vivo and in vitro in a dose-dependent manner. In addition, through RNA sequencing (RNA-seq) analysis, we show a significant activation of the transcription factor JunB both in CKD mouse arteries and in osteoblast-like VSMCs. Notably, EGCG effectively suppresses CKD-associated MAC by inhibiting the activity of JunB. In addition, overexpression of JunB can abolish while knockdown of JunB can enhance the inhibitory effect of EGCG on the osteogenic differentiation of VSMCs. Furthermore, EGCG supplementation inhibits MAC in CKD via modulation of the JunB-dependent Ras/Raf/MEK/ERK signaling pathway. In conclusion, our study highlights the potential therapeutic value of EGCG for managing CKD-associated MAC, as it mitigates this pathological process through targeted inactivation of JunB.

Integrated analysis reveals Atf3 promotes neuropathic pain via orchestrating JunB mediated release of inflammatory cytokines in DRG macrophage

The dorsal root ganglion (DRG) is actively involved in the development of neuropathic pain (NP), serving as an intermediate station for pain signals from the peripheral nervous system to the central nervous system. The mechanism by which DRG is involved in NP regulation is not fully understood. The immune system plays a pivotal role in the physiological and pathological states of the human body. In recent years, the immune system has been thought to play an increasingly important role in the pathogenesis of NP. The immune system plays a key role in pain through specific immune cells and their immune-related genes (IRGs). However, the mechanism by which IRGs of DRG regulate NP action has not been fully elucidated.Here, we performed Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of IRGs in DRG bulk-RNA sequencing data from spared nerve injury (SNI) model mice and found that their IRGs were enriched in many pathways, especially in the immune response pathway. Subsequently, we analyzed single-cell RNA sequencing (scRNA-seq) data from DRGs extracted from the SNI model and identified eight cell populations. Among them, the highest IRG activity was presented in macrophages. Next, we analyzed the scRNA and bulk-sequencing data and deduced five common transcription factors (TFs) from differentially expressed genes (DEGs). The protein-protein interaction (PPI) network suggested that Atf3 and JunB are closely related. In vitro experiments, we verified that the protein and mRNA expressions of Atf3 and JunB were up-regulated in macrophages after lipopolysaccharide (LPS) stimulation. Moreover, the down-regulation of Atf3 reduced the release of inflammatory cytokines and decreased the protein and mRNA expression levels of JunB. The down-regulation of JunB also reduced the release of inflammatory cytokines. Furthermore, overexpression of JunB attenuated the effect of Atf3 down-regulation in reducing the release of inflammatory cytokines. Therefore, we speculated that Atf3 might promote NP through JunB-mediated release of inflammatory factors in DRG macrophages.

MEK Inhibition in CAR-T Cells Prevents Exhaustion and Terminal Differentiation Via Downregulating C-Fos and JunB

Introduction: The effects of MEK inhibitors (MEKIs) in CAR-T cells are poorly understood and remain controversial. Some groups showed that MEKIs could impair CAR-T cells' function in vitro. However, another group reported that MEKIs could combine with GD2 CAR-T cells to provide additional efficacy. Yet, the mechanism for this combined effect is unclear. Considering that the CAR signaling pathway is similar to TCR, both involve the activation of MAPK signaling. We hypothesized that MEKIs might mitigate CAR-T cells' exhaustion and terminal differentiation by lessening redundant CAR signaling. The study aims to systematically evaluate the role and mechanism of MEK inhibitors on CAR-T cells. Methods and Results: To explore whether MEKIs could mitigate the unbeneficial impact of antigen-independent CAR tonic signaling, we added 3 FDA-approved MEKIs: trametinib, cobimetinib, and binimetinib, respectively, to the culture medium of CD19.28z CAR-T cells for 9 days at the concentration approaching their clinically tolerable peak blood concentration. We found that all the 3 MEKIs could reduce CAR-T cells' terminal differentiation and restrain the expression of exhaustion and activation markers. Among them, trametinib was the most potent because it could achieve the comparable effect of cobimetinib and binimetinib at the lowest concentration. Thus, we chose trametinib for further research. We confirmed that compared to concentrations of 7.5nM and 30nM, 15nM was the optimal concentration of trametinib with mild inhibition on the proliferation of CAR-T cells and a potent effect on CAR-T cells' phenotype. Pre-treatment with trametinib didn't affect the in-vitro cytotoxicity of CD19.28z CAR-T cells. The above effects of trametinib were more significant as treatment time and the dose increased. Similar results could be obtained in analogous experiments with CD19.4-1BBz and GD2.28z CAR-T cells. Intriguingly, GD2.28z CAR-T cells cultured with trametinib had better proliferation and killing capacity because they were more exhausted than CD19.28z CAR-T cells. Using the Nalm-6-bearing leukemia xenograft model, we found that compared to DMSO pre-treated CD19.28z CAR-T cells, trametinib pre-treated CD19.28z CAR-T cells exerted more potent anti-leukemia activity, showed a less exhausted and differentiated state, proliferated better, and further extended mice survival (Fig.1). Similar results could be obtained in analogous in-vivo experiments with CD19.4-1BBz CAR-T cells. To evaluate whether trametinib could protect CAR-T cells from the exhaustion and terminal differentiation triggered by antigen stimulation, we cocultured CD19.28z CAR-T cells with Nalm-6 cells in a medium with or without trametinib. We demonstrated under antigen stimulation, trametinib could effectively inhibit CAR-T cells' activation, exhaustion, apoptosis, terminal differentiation, and phosphorylation of ERK and consequently promote the proliferation of total and CD8 CAR-T cells. In addition, after repetitive antigen stimulation, trametinib could rescue CAR-T cells' functional exhaustion and improve CAR-T cells' in-vitro cytotoxicity. Mechanistically, Single-cell and bulk RNA-Seq revealed that the effect of MEK inhibition was associated with the downregulation of AP-1 and exhaustion-associated transcription factors (TFs) and the upregulation of memory-associated TFs (Fig.2). GSEA revealed the upregulation of naive/memory-associated genes and downregulation of genes involved in T cell activation/effector/exhaustion, AP-1 pathway and apoptosis in the trametinib-treated group. Additionally, single-cell transcriptional profiling demonstrated enrichment of memory and Ki67+cycling CAR-T clusters in the trametinib-treated group. Among the AP-1 TFs downregulated by trametinib, c-Fos and JunB are the direct downstream targets of the canonical MAPK signaling pathway, and both of them were reported to implicate T cell exhaustion. Thus we speculated both downregulation of c-Fos and JunB may contribute to the role of MEKIs. Consistent with our hypothesis, overexpression of c-Fos or JunB in CAR-T cells could partially, if not all, abrogated the effects of MEK inhibition. Significance: Our research provides a strategy to optimize CAR-T antitumor efficacy by MEK inhibition and shed light on the role of c-Fos and JunB in driving CAR-T cell exhaustion and terminal differentiation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The m6A methyltransferase METTL3 contributes to Transforming Growth Factor-beta-induced epithelial-mesenchymal transition of lung cancer cells through the regulation of JUNB

N6-Methyladenosine (m6A) is the most common internal chemical modification of mRNAs involved in many pathological processes including various cancers. In this study, we investigated the role of m6A methyltransferase METTL3 in TGF-β-induced epithelial-mesenchymal transition (EMT) of lung cancer cell lines. The expression of METTL3 and m6A RNA modification were increased during TGF-β-induced EMT of A549 and LC2/ad lung cancer cells. Knockdown of METTL3 inhibited TGF-β-induced morphological conversion of the cells, enhanced cell migration potential and the expression changes of EMT-related marker genes such as CDH1/E-cadherin, FN1/Fibronectin and VIM/Vimentin. Mechanistic investigations revealed that METTL3 knockdown decreased the m6A modification, total mRNA level and mRNA stability of JUNB, one of the important transcriptional regulators of EMT. Over-expression of JUNB partially rescued the inhibitory effects of METTL3 knockdown in the EMT phenotypes. This study demonstrates that m6A methyltransferase METTL3 is indispensable for TGF-β-induced EMT of lung cancer cells through the regulation of JUNB.

Abnormally expressed JunB transactivated by IL-6/STAT3 signaling promotes uveal melanoma aggressiveness via epithelial-mesenchymal transition.

Uveal melanoma (UM) is the most common primary intraocular tumor in adults, and it carries a high risk of metastasis and mortality. Various proinflammatory cytokines have been found to be significantly increased in the aqueous humor or vitreous fluid of UM patients; however, the role of these cytokines in UM metastasis remains elusive. In the present study, we found that long-term interleukin (IL)-6 exposure promoted the migration and invasion of UM cells, diminished cell–cell adhesion, and enhanced focal adhesion. Moreover, IL-6 treatment decreased the membranous epithelial marker TJP1 and increased the cytoplasmic mesenchymal marker Vimentin. Further investigation demonstrated that JunB played a critical role in IL-6-induced UM epithelial–mesenchymal transition (EMT). In UM cells, the expression of JunB was significantly up-regulated during the IL-6-driven EMT process. Additionally, JunB induction occurred at the transcriptional level in a manner dependent on phosphorylated STAT3, during which activated STAT3 directly bound to the JunB promoter. Importantly, the knockdown of STAT3 prevented the IL-6-induced EMT phenotype as well as cell migration and invasion, whereas JunB overexpression recovered the attenuated aggressiveness of UM cells. Similarly, with IL-6 stimulation, the stable overexpression of JunB strengthened the migratory and invasive capabilities of UM cells and induced the EMT-promoting factors (Snail, Twist1, matrix metalloproteinase (MMP)-2, MMP-14, and MMP-19). Analysis of The Cancer Genome Atlas (TCGA) database indicated that JunB was positively correlated with IL-6 and STAT3 in UM tissues. The present study proposes an IL-6/STAT3/JunB axis leading to UM aggressiveness by EMT, which illustrates the negative side of inflammatory response in UM metastasis.

Abstract 5186: Overexpression of CXCR4 and JUNB in disseminated tumor cells (DTCs) isolated from breast cancer patients before neoadjuvant treatment

Abstract Introduction: The presence of Disseminated (DTCs) and Circulating Tumor Cells (CTCs) in the bone marrow (BM) and the blood of breast cancer (BC) patients are poor prognostic factors. We have recently shown that CTCs derived from metastatic BC patients, overexpressed CXCR4 and JUNB and this expression was related to clinical outcome. In this study we applied the same methodology to BM of non-metastatic BC patients at primary diagnosis, before the onset of therapy. Methods: Bilateral BM (10 ml) aspirations were assessed for the detection of DTCs by a Ficoll density gradient centrifugation and subsequent centrifugation of the BM cells onto glass slides [1x106 mononuclear cells (MNCs) per slide]. Triple staining experiments with panytokeratin/CXCR4/JUNB antibodies were performed. An expression pattern of the examined proteins was created, using three different BC cell lines (SKBR3, MDA-MB231, and MCF7). Consequently, 10 BM aspirations from BC patients were analyzed. Mean intensity for each examined molecule was calculated automatically with the ARIOL system. Results: Quantification of CXCR4 among BC cell lines revealed that CXCR4 expression followed the subsequent hierarchy SKBR3>MCF7>MDA-MB231 with higher expression in SKBR3 and lower in MDA-MB 231 cells, respectively. Accordingly, the expression pattern of JUNB in cell lines was SKBR3>MCF7>MDA-MB231. Consequently, we analyzed 10 BM samples from primary BC patients. The (CXCR4+JUNB+CK+) phenotype was observed in 90% (9/10) of the samples. In addition, the (CXCR4-JUNB+CK+) phenotype was detected in 20% (2/10) of the patients. Interestingly, the (CXCR4+JUNB-CK+) phenotype was not observed in any of the patient's samples. Quantification of CXCR4 expression revealed that the mean intensity in DTCs (19.1±2) was statistically higher than in MCF7 (13±0.51; p=0.006) and MDA-MB231 (10.22±0.7; p= 0.0002) cell lines. It was also higher compared to normal donors' PBMCs (10.6±1.01; p=0.0004). In addition, the mean intensity of JUNB was statistically increased in DTCs (17.1±1.66) compared to MCF7 (8.9±0.56; p=0.00001) and MDA-MB231 (6.6±0.15; p= 0.00001) cells, respectively. Furthermore, it was increased compared to normal donors' PBMCs (5.2±0.15; p=0.0002). In two patients, we had available samples after treatment. In one patient, DTCs were eliminated after neoadjuvant therapy, for the other patient, DTCs were reduced from 10 to two DTCs. However, these cells were double positive for CXCR4 and JUNB. Conclusion: CXCR4 and JUNB were overexpressed in DTCs derived from primary BC patients, in agreement to previous findings in CTCs, implying an upregulation of the CXCR4 pathway in these cells. Quantification of this expression potentially defines a subgroup of patients with high expression of CXCR4 and JUNB that could benefit from targeted therapies. Citation Format: Galatea Kallergi, Oliver Hoffmann, Nefeli Zacharopoulou, Christos Stournaras, Vassilis Georgoulias, Sabine Kasmir-Bauer. Overexpression of CXCR4 and JUNB in disseminated tumor cells (DTCs) isolated from breast cancer patients before neoadjuvant treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5186.

MicroRNA 199a-5p induces apoptosis by targeting JunB

MicroRNAs participate in a variety of physiological and pathophysiological processes in various organs including the heart. Our previous work revealed that the level of miR-199a-5p was significantly higher in failing hearts than in control hearts. However, whether it is associated with the progression of heart failure (HF) and mediates cardiomyocyte apoptosis remained unclear. In the present study, we used various biochemical and molecular biological approaches to investigate the changes in miR-199a-5p levels in failing hearts in a rat model induced by acute myocardial infarction. We found that miR-199a-5p levels in the heart increased with the progression of HF, and overexpression of miR-199a-5p significantly increased apoptosis in untreated H9C2 cells and potentiated angiotensin II-induced apoptosis. Thus, our results indicate that miR-199a-5p is involved in the progression of HF and mediates cardiomyocyte apoptosis. We also confirmed that JunB, a member of the activator protein-1 transcription factor family, is one of direct targets of miR-199a-5p via a dual-luciferase reporter assay and mutagenesis on the 3′ untranslated region of the JunB gene. Consistent with the above findings, overexpression of JunB in H9c2 cells suppressed cell apoptosis. Based on our findings, miR-199a-5p induces apoptosis by targeting JunB.

The Fos-Related Antigen 1-JUNB/Activator Protein 1 Transcription Complex, a Downstream Target of Signal Transducer and Activator of Transcription 3, Induces T Helper 17 Differentiation and Promotes Experimental Autoimmune Arthritis.

Dysfunction of T helper 17 (Th17) cells leads to chronic inflammatory disorders. Signal transducer and activator of transcription 3 (STAT3) orchestrates the expression of proinflammatory cytokines and pathogenic cell differentiation from interleukin (IL)-17-producing Th17 cells. However, the pathways mediated by STAT3 signaling are not fully understood. Here, we observed that Fos-related antigen 1 (FRA1) and JUNB are directly involved in STAT3 binding to sites in the promoters of Fosl1 and Junb. Promoter binding increased expression of IL-17 and the development of Th17 cells. Overexpression of Fra1 and Junb in mice resulted in susceptibility to collagen-induced arthritis and an increase in Th17 cell numbers and inflammatory cytokine production. In patients with rheumatoid arthritis, FRA1 and JUNB were colocalized with STAT3 in the inflamed synovium. These observations suggest that FRA1 and JUNB are associated closely with STAT3 activation, and that this activation leads to Th17 cell differentiation in autoimmune diseases and inflammation.

Abstract 4521: Long term hypoxia induces stable overexpression of JUNB and the TGFβ pathway in colon cancer

Abstract Introduction: Metastasis is responsible for over 90% of cancer related mortality, however mutations unique to the metastatic phenotype have yet to be identified. This raises the possibility that the metastatic phenotype is the result of a transcriptional profile adopted by cells of the primary tumor enabling them to spread to distal regions of the body. The tumor microenvironment (TME) is capable of influencing gene expression and cellular behavior. Hypoxia, low oxygen tension, is a component of the TME that arises due to improper tissue architecture and correlates with poor survival outcome. Stabilization of the transcription factor HIF-1α during hypoxia induces the expression of genes involved in metastasis through direct activation and through the alteration of the epigenome. However, upon re-oxygenation HIF-1α is degraded and can no longer induce expression of hypoxic responsive genes. During the metastatic process, cells that have adopted hypoxia induced metastatic behavior such as increased motility and invasiveness must transit through regions of normoxia on their way to metastatic colonization. Hypothesis: As hypoxic cell migrate away from regions of low oxygen towards oxygen rich environments, such venous blood, genes induced by hypoxia would be expected to return to basal levels of expression. Those genes whose expression does not return to levels associated with normoxia, but instead remain elevated following re-oxygenation, may be crucial for maintaining the hypoxia induced metastatic phenotype. Experimental Design: To study the stability of hypoxia induced gene expression alterations following re-oxygenation, colon cancer cell lines were grown under hypoxic conditions (1% O2) for up to 3 weeks and then transitioned to normoxic conditions (21% O2). RNA sequencing was used to assess changes in gene expression during hypoxia adaptation and for 3 more weeks following re-oxygenation. Results: While the majority of genes whose expression was induced by hypoxia returned to basal levels following re-oxygenation, a subset of genes clustered in the TGF-β pathway remained at elevated levels. In particular the expression of JunB, a component of the AP-1 transcription factor, was induced by hypoxia and continued to remain overexpressed after return to normoxic growth conditions. Conclusion: Long term culturing of colon cancer cells in hypoxic conditions induces changes in gene expression that remain stable following return to normoxic growth conditions. We hypothesis that genes whose expression follows this pattern may be involved in the hypoxia induced metastatic phenotype. RNA-seq profiling of cells grown in hypoxic conditions for three weeks and then returned to normoxic growth conditions for an additional three weeks identified genes involved in the TGF-β pathway and in particular JunB that were induced by hypoxia and remained stable following return to normoxia. Citation Format: Colin Flinders, Norah Alwash, Shannon Mumenthaler. Long term hypoxia induces stable overexpression of JUNB and the TGFβ pathway in colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4521. doi:10.1158/1538-7445.AM2017-4521

JunD Is Required for Proliferation of Prostate Cancer Cells and Plays a Role in Transforming Growth Factor-β (TGF-β)-induced Inhibition of Cell Proliferation

TGF-β inhibits proliferation of prostate epithelial cells. However, prostate cancer cells in advanced stages become resistant to inhibitory effects of TGF-β. The intracellular signaling mechanisms involved in differential effects of TGF-β during different stages are largely unknown. Using cell line models, we have shown that TGF-β inhibits proliferation in normal (RWPE-1) and prostate cancer (DU145) cells but does not have any effect on proliferation of prostate cancer (PC3) cells. We have investigated the role of Jun family proteins (c-Jun, JunB, and JunD) in TGF-β effects on cell proliferation. Jun family members were expressed at different levels and responded differentially to TGF-β treatment. TGF-β effects on JunD protein levels, but not mRNA levels, correlated with its effects on cell proliferation. TGF-β induced significant reduction in JunD protein in RWPE-1 and DU145 cells but not in PC3 cells. Selective knockdown of JunD expression using siRNA in DU145 and PC3 cells resulted in significant reduction in cell proliferation, and forced overexpression of JunD increased the proliferation rate. On the other hand, knockdown of c-Jun or JunB had little, if any, effect on cell proliferation; overexpression of c-Jun and JunB decreased the proliferation rate in DU145 cells. Further studies showed that down-regulation of JunD in response to TGF-β treatment is mediated via the proteasomal degradation pathway. In conclusion, we show that specific Jun family members exert differential effects on proliferation in prostate cancer cells in response to TGF-β, and inhibition of cell proliferation by TGF-β requires degradation of JunD protein.

Involvement of JunB Proto-Oncogene in Tail Formation During Early Xenopus Embryogenesis.

Integration of signaling pathways is important for the establishment of the body plan during embryogenesis. However, little is known about how the multiple signals interact to regulate morphogenesis. Here, we show that junb is expressed in the posterior neural plate and the caudal fin during Xenopus embryogenesis and that overexpression of wild-type JunB induces small head phenotypes and ectopic tail-like structures. A mutant form of JunB that lacked GSK3 and MAPK phosphorylation sites showed stronger tail-like structure-inducing activity than wild-type JunB. Moreover, the mutant JunB induced expression of tailbud and neural marker genes, but not somite and chordoneural hinge (CNH) marker genes in ectopic tail-like structures. In ectodermal explants of Xenopus embryos, overexpression of JunB increased the expression of tailbud and posterior marker genes including fgf3, xbra (t) and wnt8. These results indicate that JunB is capable of inducing the ectopic formation of tissues similar to the tailbud, and that the tailbud-inducing activity of JunB is likely to be regulated by FGF and Wnt pathways. Overall, our results suggest that JunB is a regulator of tail organization possibly through integration of several morphogen signaling pathways.

Abstract 4073: Proteasomal degradation of JunD is required for TGF-β induced inhibition of proliferation in prostate cancer cells.

Abstract Transforming growth factor-β (TGF-β) inhibits proliferation of prostate epithelial cells. However, prostate cancer cells in advanced stages become resistant to TGF-β effects on proliferation. In this study, we have investigated the role of AP-1 family of transcription factors, specifically the Jun family members (c-Jun, JunB and JunD) in TGF-β1 effects on prostate cancer cell proliferation. Basal expression of individual Jun family members was determined by RT-PCR and Western blot analysis in four prostate cell lines: RWPE1, LNCaP, DU145 and PC3 cells. Jun levels were also examined in response to TGF-β1. c-Jun was expressed in all cell lines and its expression was up-regulated by TGF-β1. Levels of JunB were higher in normal cells compared to those in cancer cells and TGF-β1caused an increase in JunB levels. JunD levels were higher in all cell lines; TGF-β1 had differential effects on JunD protein levels. While it caused a significant decrease in JunD levels in RWPE-1 and DU145 cells, it did not affect JunD levels in PC3 cells. These differential effects on JunD levels correlated with differential effects of TGF-β on cell proliferation. Individual Jun family members were overexpressed in DU145 cells and effects on cell proliferation were determined. Over-expression of c-Jun and JunB decreased proliferation rate in DU145 cells; however, overexpression of JunD increased proliferation in these cells. Interestingly, cells over-expressing JunD still succumb to inhibitory effect of TGF-β1 after six to eight days of incubation. Furthermore, silencing JunD by siRNA decreased proliferation in both DU145 and PC3 cells. To determine the molecular mechanism of TGF-β-induced down-regulation of JunD, we pretreated cells over-expressing JunD with a proteosomal inhibitor, MG132. Pretreatment of MG132 blocked the degradation of JunD in in DU145 cells over-expressing JunD. In conclusion, our studies show that specific Jun family exerts differential effects on proliferation in prostate cancer cells in response to TGF-β1. While c-Jun and Jun B mediate the inhibitory effects of TGF-β1 on proliferation, JunD counteracts these effects. TGF-β1 causes inhibition in proliferation by degrading JunD via proteasomal degradation. Acknowledgements: These studies were supported by the NIH/NIMHD/RCMI grant #G12MD007590, NIH/NIMHD #5P20MD002285, and DOD grant # W8I-08-1-0077. Citation Format: Ana C. Millena, BaoHan T. Vo, Nicole Strong, Lindsey Walker, Yang Cao, Natalya Klueva, Curt Pfarr, Shafiq Khan. Proteasomal degradation of JunD is required for TGF-β induced inhibition of proliferation in prostate cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4073. doi:10.1158/1538-7445.AM2013-4073

Abstract 4206: Identification of transcriptional regulatory motifs that control gene expression in premenopausal women with previous history of breast cancer

Abstract Background: Age is an important risk factor for Breast Cancer. Older women have a 50 times greater risk for breast cancer as compared to younger women (under the age of 30 years). Aging is associated with activation of specific transcription factor networks. We hypothesized that premature activation of these programs may predispose to cancer. The aims of this study were 1) to identify active transcription factor networks controlling the expression of specific cancer-related genes in the normal breast and 2) to analyze whether premature activation of this network is associated with neoplastic transformation. Methods: Fresh frozen normal breast tissue of women, under the age of 50 years, with and without history of breast cancer was obtained (ncancer=8, nnon cancer=4). Total RNA was extracted, cDNA annealed and Whole-genome DASL assay (Illumina Corp) was conducted to identify genes that correlated with cancer outcome in premenopausal women. Differential expression analysis was performed using Partek® software program to identify the up or down regulated genes in women with cancer compared to those without. Transcription factors affecting the regulation of genes in patients with cancer were predicted using MotifModeler program (Liu et al). The resulting data was confirmed using qPCR analysis. Results: Whole genome DASL analysis showed differential expression of 34 genes (p-value <0.01). MotifModeler analysis predicted 18 transcription factors as major regulators of gene expression in premenopausal women with previous history of breast cancer. JUNB and FOS were the most significantly altered in this comparison. qPCR pre-validated the over expression of JUNB and FOS in association with cancer development. Further validation studies in an independent cohort are ongoing using Formalin-fixed Paraffin-embedded (FFPE) samples. Conclusion: Gene expression analysis identified transcriptional features of cancer outcome. Differential expression of the JUNB and FOS family of proteins, which are part of AP-1 transcription factor complex, may be correlated with neoplastic transformation in premenopausal women. Breast Cancer Program of the IU Simon Cancer Center funded this project. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4206. doi:1538-7445.AM2012-4206

Regulation of HGF-mediated cell proliferation and invasion through NF-κB, JunB, and MMP-9 cascades in stomach cancer cells

Blocking of activator protein-1 activity leads to suppression of growth factor-induced transformation. However, the role of individual components of the Jun family in this process is unclear. Over-expression of JunB has been reported to be associated with neoplastic transformation and regulation of Matrix metalloproteinase-9 (MMP-9) expression. Using cDNA microarray, we found that JunB might be one of target genes up-regulated by hepatocyte growth factor (HGF). Therefore, we tried to investigate the role of JunB in HGF-medicated cell proliferation and cell invasion in human gastric cancer cells, NUGC3 and MKN28. We verified that HGF increased JunB in time and dose-dependent manners. The JunB levels were decreased by the treatment with an NF-κB inhibitor, pyrrolidine dithiocarbamate. Down-regulation of JunB by transfecting cells with JunB-short hairpin RNAs (shRNA) inhibited MMP-9 up-regulation induced by HGF. Furthermore, transfection with JunB-shRNA repressed HGF-mediated increases in cell proliferation and cell invasion. These data suggest that JunB might be regulated through an NF-κB pathway and up-regulation of JunB induced by HGF might play an important role in the regulation of cell proliferation and cell invasion through MMP-9 expression. In conclusion, these results may contribute to the JunB-associated malignant phenotype of gastric cancers by regulating MMP-9, and serve as a novel therapeutic target for stomach cancer therapy in the future.

Ets-1 Activates Overexpression of JunB and CD30 in Hodgkin's Lymphoma and Anaplastic Large-Cell Lymphoma

Overexpression of CD30 and JunB is a hallmark of tumor cells in Hodgkin's lymphoma (HL) and anaplastic large-cell lymphoma (ALCL). We reported that CD30-extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) signaling induces JunB, which maintains constitutive activation of the CD30 promoter. Herein, we localize a cis-acting enhancer in the JunB promoter that is regulated by Ets-1. We show that E26 transformation-specific-1 (Ets-1) (-146 to -137) enhances JunB promoter activation in a manner that is dependent on CD30 or the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK)-ERK1/2 MAPK pathway. Ets-1 knockdown reduces the expression of both JunB and CD30, and CD30 knockdown significantly reduces JunB expression in HL and ALCL cell lines. NPM-ALK knockdown also reduces JunB expression in ALCL cell lines expressing NPM-ALK. Collectively, these results indicate that CD30 and NPM-ALK cooperate to activate the ERK1/2 MAPK-Ets-1 pathway. Ets-1, constitutively activated by ERK1/2-MAPK, plays a central role in the overexpression of JunB and CD30, which are both involved in the pathogenesis of HL and ALCL.

Enhanced Chromatin Accessibility and Recruitment of JUNB Mediate the Sustained IL-4 Expression in NFAT1 Deficient T Helper 2 Cells

Nuclear factor of activated T cells (NFAT) is a family of transcription factors composed of five proteins. Among them, NFAT1 is a predominant NFAT protein in CD4+ T cells. NFAT1 positively regulates transcription of a large number of inducible cytokine genes including IL-2, IL-4, IL-5 and other cytokines. However, disruption of NFAT1 results in an unexpected increase of IL-4. In this study, we have investigated the role of NFAT1 in regulation of IL-4 gene expression in T helper 2 cells (Th2) from an epigenetic viewpoint. NFAT1 deficient Th2 cells showed a sustained IL-4 expression while wild type (WT) cells reduced its expression. We tested whether epigenetic maintenance and changes in the chromatin architecture of IL-4 promoter locus play a role in differential IL-4 transcription between in WT and NFAT1 deficient Th2 cells. Compared with WT, NFAT1 deficient CD4+ Th2 cells exhibited enhanced chromatin accessibility with permissive histone modification and DNA demethylation in the IL-4 promoter region. Transcription factors bound to IL-4 promoter region in the absence of NFAT1 were identified by Micro-LC/LC-MS/MS analysis. Among the candidates, preferential recruitment of JUNB to the IL-4 promoter was confirmed by chromatin immunoprecipitation analysis. Overexpression of JUNB together with SATB1 synergistically upregulated IL-4 promoter activity, while knockdown JUNB significantly reduced IL-4 expression. Our results suggest that the prolonged IL-4 expression in NFAT1 deficient Th2 cells is mediated by preferential binding of JUNB/SATB1 to the IL-4 promoter with permissive chromatin architecture.

Opposite Regulation of the Human Apolipoprotein M Gene by Hepatocyte Nuclear Factor 1 and Jun Transcription Factors

HDL is a negative risk factor for atherosclerosis because of its multiple atheroprotective functions. Inflammation converts HDL particles from anti-atherogenic to pro-atherogenic, and this transformation is associated with changes in HDL structure and composition. Apolipoprotein M (apoM) has been recently shown to play a role in the maturation of HDL in plasma and to protect from atherosclerosis. ApoM gene is expressed primarily in the liver and kidney and is down-regulated by pro-inflammatory signals. We now show that the human apoM promoter harbors a dual specificity regulatory element in the proximal region that binds hepatocyte nuclear factor 1 (HNF-1) and members of the AP-1 family of pro-inflammatory transcription factors (c-Jun and JunB). Overexpression of c-Jun or JunB repressed both the basal and the HNF-1-mediated transactivation of the human apoM promoter. Treatment of HepG2 cells with potent inflammation-inducing phorbol esters or overexpression of PKCα was associated with a marked inhibition of apoM gene expression in a c-Jun/JunB-dependent manner. We provide evidence for a novel mechanism of inflammation-induced transcriptional repression that is based on the competition between HNF-1 and Jun proteins for binding to the same regulatory region. A similar mechanism accounts for the down-regulation of the liver-specific apolipoprotein A-II gene by Jun factors. Our studies provide novel insights on the mechanisms that control the expression of liver-specific apolipoprotein genes during inflammation and could affect the maturation and the functionality of HDL particles.

AP-1 Regulates Cyclin D1 and c-MYC Transcription in an AKT-Dependent Manner in Response to mTOR Inhibition: Role of AIP4/Itch-Mediated JUNB Degradation

One mechanism by which AKT kinase-dependent hypersensitivity to mammalian target of rapamycin (mTOR) inhibitors is controlled is by the differential expression of cyclin D1 and c-MYC. Regulation of posttranscriptional processes has been demonstrated to be crucial in governing expression of these determinants in response to rapamycin. Our previous data suggested that cyclin D1 and c-MYC expression might additionally be coordinately regulated in an AKT-dependent manner at the level of transcription. Under conditions of relatively quiescent AKT activity, treatment of cells with rapamycin resulted in upregulation of cyclin D1 and c-MYC nascent transcription, whereas in cells containing active AKT, exposure repressed transcription. Promoter analysis identified AKT-dependent rapamycin responsive elements containing AP-1 transactivation sites. Phosphorylated c-JUN binding to these promoters correlated with activation of transcription whereas JUNB occupancy was associated with promoter repression. Forced overexpression of JunB or a conditionally active JunB-ER allele repressed cyclin D1 and c-MYC promoter activity in quiescent AKT-containing cells following rapamycin exposure. AIP4/Itch-dependent JUNB protein degradation was found to be markedly reduced in active AKT-containing cells compared with cells harboring quiescent AKT. Moreover, silencing AIP4/Itch expression or inhibiting JNK mediated AIP4 activity abrogated the rapamycin-induced effects on cyclin D1 and c-MYC promoter activities. Our findings support a role for the AKT-dependent regulation of AIP4/Itch activity in mediating the differential cyclin D1 and c-MYC transcriptional responses to rapamycin.