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PubMed1999

Constitutive activation of transcription factors NF-(kappa)B, AP-1, and NF-IL6 in human head and neck squamous cell carcinoma cell lines that express pro-inflammatory and pro-angiogenic cytokines.

We previously reported that human head and neck squamous cell carcinomas (HNSCCs) express the pro-inflammatory and pro-angiogenic cytokines interleukin (IL)-1alpha, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor in vitro and in vivo. The promoter region of the genes encoding these cytokines include binding sites for the transcription factors nuclear factor (NF) kappaB/Rel A, activator protein-1 (AP-1), and CCAAT enhancer-binding protein beta (C/EBPbeta, or NF-IL6), which have been reported to contribute to activation of these cytokine genes. In the study presented here, we examined the activation, composition, and function of these transcription factors in HNSCC cell lines that express pro-inflammatory cytokines, by using electrophoretic mobility shift and reporter-gene assays. Constitutive activation of NF-kappaB, AP-1, and NF-IL6 DNA-binding proteins was detected. Supershift analysis with antibodies specific for NF-kappaB, AP-1, and NF-IL6 binding proteins showed that the NF-kappaB-binding protein included p65/Rel A and p50; AP-1 activity included c-jun, junB, junD, and Fra-1; and NF-IL6 included C/EBPbeta. Mutational analysis of the NF-kappaB, AP-1, and NF-IL6 sites in the IL-8 promoter region showed that NF-kappaB and AP-1 sites contributed to constitutive IL-8 reporter activity in HNSCC. HNSCC lines that exhibited increased IL-8 secretion relative to simian virus 40-immortalized and primary keratinocyte cell lines also demonstrated a concordant increase in NF-kappaB reporter activity relative to nonmalignant keratinocytes. We concluded that the early transcription factors NF-kappaB, AP-1, and NF-IL6 are constitutively activated in human HNSCC cell lines and that NF-kappaB and AP-1 promote expression of the pro-inflammatory and pro-angiogenic cytokine IL-8 in HNSCC. The demonstration of the activation of these transcription factors will be helpful in defining the identity and role of these and other early gene products that contribute to pathogenesis of the malignant phenotype in HNSCC and in defining potential targets for pharmacologic and molecular therapy of HNSCC. Mol. Carcinog. 26:119-129, 1999. Published 1999 Wiley-Liss, Inc.

CCAAT-Enhancer-Binding Proteins↗

PubMed2002

Modulation of lipopolysaccharide-induced NF-IL6 activation by protein kinase C-alpha in a mouse macrophage cell line.

We have previously shown that overexpression of a dominant-negative (DN) mutant of protein kinase C-alpha (PKC-alpha) in RAW 264.7 macrophages inhibited lipopolysaccharide (LPS)-induced IL-1alpha, inducible nitric oxide synthase and cyclooxygenase-2 expression. This inhibition was not related to defective NF-kappaB nuclear translocation, suggesting that PKC-alpha might be involved in the modulation of other LPS-inducible transcription factors. In the present study, we have investigated the impact of PKC-alpha on the activation of AP-1 and NF-IL6 in LPS-treated RAW 264.7 macrophages. Electrophoretic mobility shift assays and luciferase reporter constructs revealed that LPS-induced AP-1 transcriptional activity was normal in DN PKC-alpha-overexpressing RAW 264.7 cells. In contrast, LPS-induced DNA-binding and transcriptional activities of NF-IL6 were inhibited in DN PKC-alpha-overexpressing RAW 264.7 cells and correlated with an impairment of NF-IL6 nuclear translocation. Conversely, overexpression of either wild-type PKC-alpha or a constitutively active PKC-alpha mutant significantly enhanced LPS-stimulated NF-IL6-dependent promoter activity. Finally, LPS-induced expression of two genes regulated by NF-IL6, namely IL-1beta and granulocyte colony-stimulating factor, was impaired in DN PKC-alpha-overexpressing RAW 264.7 cells. Taken together, these results suggest that regulation of NF-IL6 activity constitutes one of the mechanisms by which PKC-alpha modulates LPS-induced gene expression in the mouse macrophage cell line RAW 264.7.

Active Transport, Cell Nucleus↗

PubMed1993

Normal breast epithelial cells produce interleukins 6 and 8 together with tumor-necrosis factor: defective IL6 expression in mammary carcinoma.

Virtually pure primary cultures of normal mammary epithelial cells (MEC) obtained from healthy women were shown to release interleukin 6 and 8 (IL6, IL8) and to produce a nonsecreted form of tumor-necrosis factor (TNF). No interferon (IFN), whether alpha, beta, or gamma, or IL1-alpha or -beta could be detected. Analysis of cellular RNA confirmed these findings and showed that MEC also express IL6 receptor and TNF-alpha-related mRNAs. Epithelial cells were selectively stained by antibodies to IL6, IL8 and TNF-alpha both in primary cultures and in the normal mammary gland. Samples of human milk contained sizable amounts of IL6, IL8 and IFN-gamma; yet the liquid phase was consistently negative for other cytokines (i.e., TNF-alpha, IFN-alpha/-beta, IL1-alpha/-beta). Expression of IL6 (but not of IL8 and TNF-alpha) was abolished in ductal infiltrating carcinomas and greatly reduced in cultures of oncogene-transfected mammary cells, suggesting that alterations of IL6 expression are associated with pathogenesis in breast cancer.

Adolescent↗

PubMed1991

Time course of IL1 and IL6 synthesis and release in human bronchial epithelial cell cultures exposed to toluene diisocyanate.

We have previously demonstrated that human bronchial epithelial cells release appreciable amounts of interleukin 1 (IL1) and interleukin 6 (IL6) when exposed to toluene diisocyanate (TDI) in vitro. TDI is an inflammatory and asthmogenic stimulus presumed to act at least in part through immunological mechanisms. The epithelial cell-derived IL1 and IL6 can promote T cell activation and proliferation in culture, and if this also happens in vivo they may contribute to the persistence of the inflammatory response of the bronchial mucosa observed in TDI-sensitive asthmatics. In this study, we confirmed the release of biologically active IL1 beta and IL6-like substances from bronchial epithelial cells exposed to isocyanates in vitro, and related the rate and the magnitude of the cytokine secretion with the pattern of IL1 beta and IL6 gene expression and the extent of epithelial cell injury. In the epithelial cell cultures exposed to TDI, there was a parallel, progressive increase in the expression of IL6 mRNA and in the secretion of IL6 protein between 48 hours and 6 days after exposure. By contrast, although increasing amounts of biologically active IL1 beta were detected in the supernatants of TDI-exposed epithelial cells throughout the 6-day period following exposure, augmented levels of IL1 beta mRNA were only evident 6 days after exposure, suggesting that TDI exposure might have initially affected the enzymatic cleavage of the intracellular IL1 beta precursor and the mechanisms which regulate the secretion of mature IL1 beta.

Blotting, Northern↗

PubMed2001

Cyclic AMP- and IL6-signaling cross talk: comodulation of proliferation and apoptosis in the 7TD1 B cell hybridoma.

Proliferation of the 7TD1 B cell hybridoma is dependent on the survival factor interleukin-6 (IL6). IL6 inhibits physiological cell death and allows expansion of populations of serum-stimulated cells. In this report, we demonstrate that cyclic AMP (cAMP)- and IL6-dependent signaling pathways can interact, controlling proliferation of 7TD1 cells through modulation of apoptosis. Cyclic AMP analogues inhibited proliferation, as well as other treatments that increased intracellular cAMP. The cAMP-induced inhibition could be reversed after 24 h by the removal of dibutyryl-cAMP from the culture medium and readdition of IL6. In the absence of IL6, cAMP induced a slow loss of viable cells. This decrease in viable cells in the presence of cAMP was accompanied by a marked increase in apoptosis. The increase in apoptotic cells after 48 h was preceded at 24 h by a parallel increase in DEVD-caspase activity after treatment with cell-permeable cAMP analogues. Increased DEVD-caspase activity and subsequent apoptosis could both be blocked by the addition of IL6. These coregulating actions may represent a cross-talk signaling mechanism modulating cytokine activation of cellular proliferation and survival.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2005

HLXB9 activates IL6 in Hodgkin lymphoma cell lines and is regulated by PI3K signalling involving E2F3.

Multiple cytokines are secreted by Hodgkin lymphoma (HL) cells, notably interleukin-6 (IL6), which is believed to play a significant pathobiological role in this and certain other tumors. Previous work on prostate carcinoma cells has shown that IL6 expression is activated therein by the homeodomain protein GBX2, which we found to be absent in HL cells. Instead, we observed expression of a closely related gene, HLXB9, albeit restricted to HL cells coexpressing IL6. Treatment of HL cell lines with antisense-oligonucleotides directed against HLXB9, forced expression of recombinant HLXB9, and analysis of reporter gene constructs containing IL6 promoter sequences all confirmed the potential of HLXB9 to drive expression of IL6. Chromosomal rearrangements of the HLXB9 locus at 7q36 were not detected in HL cells unlike AML subsets expressing HLXB9. However, inhibition of certain signal transduction pathways revealed that the phosphatidylinositol 3 kinase (PI3K) pathway contributes to HLXB9 expression. AKT/phospho-AKT analysis revealed constitutively active PI3K signalling in HL cell lines. Downstream analysis of PI3K revealed that E2F3 may mediate activation of HLXB9. Taken together, our data show that the PI3K signalling pathway in HL cells is constitutively activated and promotes HLXB9 expression, probably via E2F3, thereby enhancing malignant expression of IL6.

Cell Line, Tumor↗

PubMed2004

Synergism of cytoplasmic kinases in IL6-induced ligand-independent activation of androgen receptor in prostate cancer cells.

IL6 is a pleiotropic cytokine which has been implicated in ligand-independent activation of androgen receptor in prostate cancer cells. Here, we present the evidence that two cytoplasmic kinases Pim1 and Etk are involved in this process. We showed that Pim1 is expressed in all prostate cancer cell lines examined. Both the expression level and the kinase activity of Pim1 are regulated by IL6 in these cells. Furthermore, we showed that IL6 downstream tyrosine kinase Etk can induce tyrosine phosphorylation of Pim1 which is correlated with its kinase activity. Mutation of the conserved Tyrosine 218 in the activation loop results in reduced kinase activity of Pim1. Interestingly, Etk can also be activated by Pim1 when they are coexpressed in prostate cancer cells, suggesting a possible positive feedback loop between Etk and Pim1. It appears that both Pim1 and Etk are required for IL6-induced activation of androgen receptor-mediated transcription in prostate cancer cells because overexpression of the kinase-deficient form of either Pim1 or Etk dramatically blocks the IL6 effect. Coexpression of the two kinases together but neither one alone is sufficient to activate ARE-containing promoter. Taken together, our data suggest a synergism of Ser/Thr kinase Pim1 and tyrosine kinase Etk in IL6 signaling and provide new insights into ligand-independent activation of androgen receptor in prostate cancer cells.

Cell Division↗

PubMed1993

Phosphorylation at threonine-235 by a ras-dependent mitogen-activated protein kinase cascade is essential for transcription factor NF-IL6.

NF-IL6, a member of the basic leucine zipper (bZIP) family transcription factors, is involved in expression of inducible genes involved in immune and inflammatory responses. We observed that coexpression of oncogenic p21ras stimulated the transactivating activity of NF-IL6 and induced phosphorylation of Thr-235 located just N-terminal to the DNA binding domain of NF-IL6. Recently, mitogen-activated protein (MAP) kinases have been shown to be implicated in the cellular response to activated ras. Purified MAP kinases specifically phosphorylated Thr-235 of NF-IL6 in vitro. Mutation of Thr-235 abolished the ras-dependent activation of NF-IL6. From these results, we conclude that NF-IL6 is regulated through phosphorylation by MAP kinases in response to activated ras.

3T3 Cells↗

PubMed2002

Transcription factor NF-IL6 (C/EBPbeta) activates the expression of the mouse MHC class I H2-Kb gene in response to TNF-alpha via the intragenic downstream regulatory element.

The 5'-enhancer-deleted genomic construct of the H2-K(b) gene, stably integrated into the genome of L(tk-) fibroblasts, retains full competence to be induced by tumor necrosis factor-alpha (TNF-alpha) treatment. The only defined regulatory region in this construct is the intragenic downstream regulatory element (H2DRE). Computational inspection uncovered two potential NF-IL6 (C/EBPbeta) binding motifs within the H2DRE. Chloramphenicol acetyltransferase (CAT) reporter gene assay revealed that NF-IL6 is able to elevate transcription from H2DRE. Moreover, transient transfection of an NF-IL6 expression vector increased both constitutive and TNF-alpha-induced mRNA levels of endogenous H2 class I genes, and transfection of an NF-IL6 dominant negative construct decreased the expression of endogenous H2 class I genes in a dose-dependent manner. Using the electrophoretic mobility shift assay (EMSA) and antibody supershift assay, we were able to qualify the two computationally identified NF-IL6 binding motifs as one high-affinity and one low-affinity binding site. We conclude that the H2-K(b) gene belongs to target genes of the NF-IL6 (C/EBPbeta) in the course of the cellular response to TNF-alpha, and we discuss some consequences of this conclusion in a general framework of inducible expression of the H2-K(b) gene.

3T3 Cells↗

PubMed2006

Genetic variation in IL6 gene and type 2 diabetes: tagging-SNP haplotype analysis in large-scale case-control study and meta-analysis.

Interleukin-6 (IL-6, gene symbol IL6) is a proinflammatory cytokine. High circulating IL-6 levels have been associated with insulin resistance and greater risk of type 2 diabetes. Using a linkage disequilibrium (LD)-based approach, we sought to investigate the associations of the common polymorphisms comprehensively defining the genetic variability at the IL6 locus with diabetes risk. We conducted a case-control study of 2691 cases of type 2 diabetes (1692 women and 999 men) and 3237 control subjects (2238 women and 999 men) from the Nurses' Health Study and the Health Professional Follow-up Study. Pairwise LD analysis indicated that all the IL6 polymorphisms (rs2069827, rs1800797, rs1800795, rs1554606, rs2069849, rs2069861 and rs1818879) were in strong LD. We did not find significant associations between IL6 polymorphisms and the risk of type 2 diabetes in women or men, individually or in haplotypes. In addition, none of the IL6 polymorphisms was significantly associated with the plasma levels of IL-6 in the control subjects. Our meta-analysis of 5383 diabetes case and 12 069 controls indicated a null association between the best-studied 5' promoter polymorphism--174G>C (rs1800795)--and diabetes risk. Diversity in adiposity, age and sex could not account for the heterogeneity across different studies. In summary, the data in this study do not support substantial associations between the common polymorphisms in IL6 gene and circulating IL-6 levels and the risk of type 2 diabetes.

Adult↗

PubMed2000

NF-IL6 and CRE elements principally account for both basal and interleukin-1 beta-induced transcriptional activity of the proximal 528bp of the PGHS-2 promoter in amnion-derived AV3 cells: evidence for involvement of C/EBP beta.

Prostaglandin H synthase (PGHS)-2 promoter fragments (-528 to +9 bp and 5' unidirectional deletions thereof) were cloned upstream of the chloramphenicol acetyl-transferase (CAT) reporter gene. These were transfected into amnion-derived AV3 cells. The region, -528 to -203, which includes NF-kappa B sites, had little influence on CAT expression. The region, -203 and -52, however, was responsible for most of the basal promoter activity and also conferred responsiveness to interleukin (IL)-1 beta (>3-times basal). Point mutations of NF-IL6 and cAMP response element (CRE) in this region reduced both basal and IL-1 beta-stimulated production of CAT; dual mutation eliminated IL-1 beta responsiveness. Factors in nuclear extracts from control or IL-1 beta-stimulated AV3 cells specifically complexed the NF-IL6 and CRE sequences. However, the NF-IL6 and CRE oligonucleotides cross-competed, suggesting a common factor. C/EBP beta was identified by supershift assay as interacting with both sequences. To a lesser extent C/EBP alpha and delta also interacted with the NF-IL6 site. However, CRE binding protein (CREB), was absent from the complex with the CRE. In conclusion, NF-IL6 and CRE elements principally account in AV3 amnion cells for basal and IL-1 beta-inducible transcriptional activity of the proximal 528 bp of the PGHS-2 promoter, while NF-kappa B elements play no substantial role. C/EBPs, particularly C/EBPbeta, are implicated in control of PGHS-2 transcription through the NF-IL6 and CRE sites.

Amnion↗

PubMed2001

Elevated interleukin-6 plasma levels are regulated by the promoter region polymorphism of the IL6 gene in primary Sjögren's syndrome and correlate with the clinical manifestations of the disease.

OBJECTIVES: To determine whether plasma interleukin-6 (IL-6) and G/C base exchange polymorphism at position -174 of the IL6 gene have an effect on the clinical manifestations of primary Sjögren's syndrome (pSS). METHODS: Levels of circulating IL-6 protein and polymorphism of the IL6 gene were analysed in 66 patients with pSS and in 400 healthy subjects. These data were studied in relation to clinical data on the pSS patients. RESULTS: Plasma IL-6 was elevated in pSS patients compared with healthy controls. pSS patients with coeliac disease, pulmonary fibrosis or alveolitis or peripheral nervous system symptoms had significantly higher IL-6 levels than patients without these manifestations. IL-6 levels increased in parallel with the histological grade of minor salivary gland biopsy and the number of pSS criteria fulfilled. IL6 allele frequencies were similar in patients and normal subjects. Plasma IL-6 levels were regulated by the IL6 genotype in pSS patients. CONCLUSIONS: The G/C polymorphism of the IL6 gene does not predispose patients to pSS, but the circulating IL-6 concentration is related to specific manifestations of the disease and the levels of IL-6 are regulated by the IL6 promoter polymorphism in pSS.

Adolescent↗

PubMed1993

NF-IL6 represses early gene expression of human papillomavirus type 16 through binding to the noncoding region.

The expression of human papillomavirus type 16 (HPV16) early genes, including E6 and E7 transforming genes, is regulated by several cellular factors binding to the noncoding region (NCR), such as the glucocorticoid receptor, NF-I, and AP1, all of which are positive regulators. We demonstrated that the nuclear factor for interleukin 6 expression (NF-IL6) specifically binds to the HPV16 NCR ranging from nucleotides 7007 to 7766 and represses the early gene expression of HPV16. The responsive element in HPV16 NCR was determined within the region ranging from nucleotides 7454 to 7766. In this region, many binding sites for other cellular transactivators, such as NF-I and AP1, have been detected. Interestingly, three of seven binding sites for NF-I and two of two binding sites for AP1 in this region overlap with the putative NF-IL6 binding sites identified by computer analysis. Competition experiments with the oligonucleotides containing such NF-I or AP1 sites indicated that NF-IL6 certainly binds to them. Furthermore, in a chloramphenicol acetyltransferase assay using mutant NF-IL6 expression vectors, the DNA binding domain of NF-IL6 was shown to be necessary for repression, whereas the functional domain was not. These findings indicate that repression may be caused by competition with other transcriptional activators, such as NF-I and AP1. Thus, NF-IL6 may play a significant role in the regulation of viral transcription as a part of the host's resistance to viral infection.

Acute-Phase Reaction↗

PubMed1994

Transcription factors NF-IL6 and CREB recognize a common essential site in the human prointerleukin 1 beta gene.

A site located between -2782 and -2729 of the human prointerleukin-1 beta (IL1B) gene functions as a strong lipopolysaccharide (LPS)-responsive enhancer independent of the previously identified enhancer located between -2896 and -2846 (F. Shirakawa, K. Saito, C.A. Bonagura, D.L. Galson, M. J. Fenton, A. C. Webb, and P. E. Auron, Mol. Cell. Biol. 13:1332-1344, 1993). Although these two enhancers appear to function cooperatively in the native sequence context, they function independently as LPS-responsive elements upon removal of an interposed silencer sequence. The new enhancer is not induced by dibutyryl cyclic AMP (dbcAMP) alone but is superinduced by costimulation with LPS-dbcAMP. This pattern of induction depends upon the nature of the sequence, a composite NF-IL6-cAMP response element (CRE) binding site. This pseudosymmetrical sequence is shown to contrast with a classical symmetric CRE which responds to dbcAMP but not LPS. DNA binding studies using in vivo nuclear extract, recombinant proteins, and specific antibodies show that LPS induces the formation of two different complexes at the enhancer: (i) an NF-IL6-CREB heterodimer and (ii) a heterodimer consisting of NF-IL6 and a non-CREB, CRE-binding protein. Cotransfection studies using NF-IL6 and CREB expression vectors show that NF-IL6 transactivates the enhancer in the presence of LPS, whereas CREB acts either positively or negatively, depending upon its cAMP-regulated phosphorylation state. Our data demonstrate that the newly identified enhancer is a specialized LPS-responsive sequence which can be modulated by cAMP as a result of the involvement of NF-IL6-CRE-binding protein heterodimers.

Base Sequence↗

PubMed1997

Retinoid antagonism of NF-IL6: insight into the mechanism of antiproliferative effects of retinoids in Kaposi's sarcoma.

All-trans-retinoic acid (RA) is active in the treatment of Kaposi's sarcoma (KS), and retinoids inhibit KS cell growth in vitro. To understand the mechanism of retinoid action in KS, we studied the expression of autocrine growth factors of KS cells after RA treatment. We demonstrate that RA and its synthetic analogs inhibit the proliferation of KS cells by inhibiting the mRNA and protein levels of interleukin-6 (IL-6), an autocrine growth factor for KS cells. We further demonstrate that nuclear retinoid receptors (RA receptors [RARs] and retinoid X receptors [RXRs]) inhibit IL-6 promoter action by antagonizing the enhancer action of NF-IL6, a basic domain leucine zipper transcription factor belonging to the family of CAAT enhancer binding proteins. Furthermore, RARs and RXRs do not bind in vitro to an NF-IL6 binding site. However, the secondary folded structure of the DNA binding domain of RAR and RXR is obligatory for inhibiting NF-IL6 activity. Thus, NF-IL6 is a potential therapeutic target for the treatment of KS. Finally, using receptor-selective synthetic retinoids, we demonstrate that NF-IL6 antagonism and transactivation are separable functions of RAR alpha, thus indicating that synthetic retinoids with properties of NF-IL6 antagonism but lacking transactivation capabilities can be synthesized. Such retinoids might increase therapeutic potential in KS.

CCAAT-Enhancer-Binding Proteins↗

PubMed2005

Correlation of VEGF production with IL1 alpha and IL6 secretion by human pituitary adenoma cells.

OBJECTIVES: Vascular endothelial growth factor (VEGF) is considered to be the most important angiogenic factor involved in the neovascularisation of solid tumours. Regulatory molecules include cytokines and growth factors. Interleukin (IL)1 and IL6 have both been shown to regulate VEGF levels in a variety of tissues. The role of cytokines in the pathogenesis of pituitary tumours remains unclear. We have examined the expression of VEGF and its relationships with IL1 and IL6 in the human pituitary tumour cell line HP75 and a series of human pituitary tumours. We have also looked at the relationship of tumour volume and invasive status to VEGF secretion. METHODS: Surgically resected tumours were routinely cultured in single-cell suspension at 200 K/well (standard unit for culture of dispersed primary pituitary adenoma cells). We measured VEGF, IL1 alpha and IL6 levels by ELISA. Tumour volume and invasion grade were assessed by preoperative magnetic resonance imaging. RESULTS: VEGF was detected in conditioned medium of HP75 cells (900+/-52 pg/ml) and in 82% of tumours tested (range 26-16 464 pg/ml). Tumour volume and secretion of VEGF were significantly associated with levels of IL6 (volume, P = 0.056; VEGF, P < 0.001 (P values based on Spearman's test)) and IL1 alpha produced (volume, P < 0.005; VEGF, P < 0.001). Invasive tumours showed a higher basal secretion of VEGF that that of the non-invasive type; however, this difference was not significant. Addition of exogenous IL1 alpha, but not IL6, significantly increased VEGF production. CONCLUSIONS: The significant associations between VEGF and the levels of IL6 and IL1 alpha suggest an important role for these cytokines in the development of these tumours.

Adenoma↗

PubMed2005

Inhibition of NF-IL6 activity by manassantin B, a dilignan isolated from Saururus chinensis, in phorbol myristate acetate-stimulated U937 promonocytic cells.

Mannasantin B, a dilignan structurally related to manssantin A, is an inhibitor of NF-kappaB transactivation. In the present study, we found that it inhibited PMA-induced expression of IL-1beta, IL-1beta mRNA, and IL-1beta promoter activity in U937 cells with IC50 values of about 50 nM. It also inhibited NF-IL6- and NF-kappaB-induced activation of IL-1beta, with IC50 values of 78 nM and 1.6 microM, respectively, revealing a potent inhibitory effect on NF-IL6. Electrophoretic mobility shift assays showed that manassantin B had an inhibitory effect on DNA binding by NF-IL6, but not by NF-kappaB. Further analysis revealed that transactivation by NF-IL6 was also inhibited. Our results indicate that manassantin B suppresses expression of IL-1beta in promonocytic cells by inhibiting not only NF-kappaB but also NF-IL6 activity. Furthermore, our observations suggest that manassantin B may be clinically useful as a potent inhibitor of NF-IL6 activity.

CCAAT-Enhancer-Binding Protein-beta↗

PubMed1994

NF-IL6, a member of the C/EBP family of transcription factors, binds and trans-activates the human MDR1 gene promoter.

Revealing the regulatory mechanisms involved in P-glycoprotein expression is important to our understanding of multidrug resistance (MDR) in tumor cells. The MDR1 gene encoding P-glycoprotein contained a promoter sequence (-157 to -125) that was found to be homologous with other mdr gene promoters and that specifically interacted with a nuclear protein. The nuclear protein was identified, using a HeLa lambda gt11 cDNA expression library, to be the transcriptional regulator nuclear factor for interleukin-6 (NF-IL6), a member of the C/EBP family of transcription factors that bound an NF-IL-6-like consensus element 5'-TTTCGCAGT-3'. Furthermore, a glutathione S-transferase fusion protein (10.1-glutathione S-transferase) containing the partial NF-IL6 cDNA was also found to specifically interact with the MDR1 promoter sequence. Co-transfection of an NF-IL6 expression vector with a chloramphenicol acetyltransferase reporter gene driven by 1018 base pairs of MDR1 5'-flanking sequences demonstrated that NF-IL6 trans-activated the MDR1 promoter. This trans-activation was significantly reduced when the NF-IL6 element in the reporter gene construct was deleted or mutated. Identification of NF-IL6 as an important transcriptional regulator and the implications of its potential role in MDR1 gene induction in response to a variety of stimuli are discussed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗