TRAF6

Gene Summary

Gene:TRAF6; TNF receptor-associated factor 6, E3 ubiquitin protein ligase
Aliases: RNF85, MGC:3310
Location:11p12
Summary:The protein encoded by this gene is a member of the TNF receptor associated factor (TRAF) protein family. TRAF proteins are associated with, and mediate signal transduction from, members of the TNF receptor superfamily. This protein mediates signaling from members of the TNF receptor superfamily as well as the Toll/IL-1 family. Signals from receptors such as CD40, TNFSF11/RANCE and IL-1 have been shown to be mediated by this protein. This protein also interacts with various protein kinases including IRAK1/IRAK, SRC and PKCzeta, which provides a link between distinct signaling pathways. This protein functions as a signal transducer in the NF-kappaB pathway that activates IkappaB kinase (IKK) in response to proinflammatory cytokines. The interaction of this protein with UBE2N/UBC13, and UBE2V1/UEV1A, which are ubiquitin conjugating enzymes catalyzing the formation of polyubiquitin chains, has been found to be required for IKK activation by this protein. This protein also interacts with the transforming growth factor (TGF) beta receptor complex and is required for Smad-independent activation of the JNK and p38 kinases. This protein has an amino terminal RING domain which is followed by four zinc-finger motifs, a central coiled-coil region and a highly conserved carboxyl terminal domain, known as the TRAF-C domain. Two alternatively spliced transcript variants, encoding an identical protein, have been reported. [provided by RefSeq, Feb 2012]
Databases:OMIM, HGNC, GeneCard, Gene
Protein:TNF receptor-associated factor 6
HPRD
Source:NCBIAccessed: 27 February, 2015

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 27 February 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Cancer Gene Expression Regulation
  • Apoptosis
  • Toll-Like Receptors
  • TNF Receptor-Associated Factor 6
  • Tongue Neoplasms
  • Signal Transduction
  • Biopsy
  • Lung Cancer
  • Neoplastic Cell Transformation
  • Squamous Cell Carcinoma
  • Chromosome 11
  • Mutation
  • Cell Movement
  • Amino Acid Sequence
  • TNF Receptor-Associated Factor 2
  • siRNA
  • TOR Serine-Threonine Kinases
  • Cell Proliferation
  • MicroRNAs
  • Cell Line
  • Oligonucleotide Array Sequence Analysis
  • Immunohistochemistry
  • ras Proteins
  • Gene Expression Profiling
  • Single Nucleotide Polymorphism
  • eIF-2 Kinase
  • Neoplasm Proteins
  • Tumor Markers
  • I-kappa B Kinase
  • Interleukin-1 Receptor-Associated Kinases
  • Transfection
  • Bladder Cancer
  • Knockout Mice
  • Messenger RNA
  • RTPCR
  • Molecular Sequence Data
  • Breast Cancer
  • Protein Binding
  • Up-Regulation
  • NF-kappa B
  • Young Adult
Tag cloud generated 27 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: TRAF6 (cancer-related)

Wang Y, Sun C, Li T, et al.
Integrative approach detected association between genetic variants of microRNA binding sites of TLRs pathway genes and OSCC susceptibility in Chinese Han population.
PLoS One. 2014; 9(7):e101695 [PubMed] Free Access to Full Article Related Publications
Oral squamous cell carcinoma (OSCC) is a leading malignancy worldwide; the overall 5-year survival rate is approximately 50%. A variety of proteins in Toll-like receptors (TLRs) pathway have been related with the risk of OSCC. However, the influence of genetic variations in TLRs pathway genes on OSCC susceptibility is unclear. Previous studies mainly focused on the coding region of genes, while the UTR region remains unstudied. In the current study, a bioinformatics approach was performed to select candidate single nucleotide polymorphisms (SNPs) on microRNA binding sites of TLRs pathway genes related with OSCC. After screening 90 OSCC related TLRs pathway genes, 16 SNPs were selected for genotyping. We found that rs5030486, the polymorphisms on 3' UTR of TRAF6, was significantly associated with OSCC risk. AG genotype of TRAF6 was strongly associated with a decreased risk of OSCC (OR = 0.252; 95% CI = 0.106, 0.598; p = 0.001). In addition, AG genotype was also related with a reduced risk of OSCC progression both in univariable analysis (HR = 0.303, 95% CI = 0.092, 0.995) and multivariable analysis (HR = 0.272, 95% CI = 0.082, 0.903). Furthermore, after detecting the mRNA expression level of TRAF6 in 24 OSCC patients, we found that TRAF6 expression level was significantly different between patients carrying different genotypes at locus rs5030486 (p = 0.013), indicating that rs5030486 of TRAF6 might contribute to OSCC risk by altering TRAF6 expression level. In general, these data indicated that SNP rs5030486 could be a potential bio-marker for OSCC risk and our results might provide new insights into the association of polymorphisms within the non-coding area of genes with cancers.

Natarajan V, Komarov AP, Ippolito T, et al.
Peptides genetically selected for NF-κB activation cooperate with oncogene Ras and model carcinogenic role of inflammation.
Proc Natl Acad Sci U S A. 2014; 111(4):E474-83 [PubMed] Free Access to Full Article Related Publications
Chronic inflammation is associated with increased cancer risk. Furthermore, the transcription factor NF-κB, a central regulator of inflammatory responses, is constitutively active in most tumors. To determine whether active NF-κB inherently contributes to malignant transformation, we isolated a set of NF-κB-activating genetic elements and tested their oncogenic potential in rodent cell transformation models. Genetic elements with desired properties were isolated using biologically active selectable peptide technology, which involves functional screening of lentiviral libraries encoding 20 or 50 amino acid-long polypeptides supplemented with endoplasmic reticulum-targeting and oligomerization domains. Twelve NF-κB-activating selectable peptides (NASPs) representing specific fragments of six proteins, none of which was previously associated with NF-κB activation, were isolated from libraries of 200,000 peptides derived from 500 human extracellular proteins. Using selective knockdown of distinct components of the NF-κB pathway, we showed that the isolated NASPs act either via or upstream of TNF receptor-associated factor 6. Transduction of NASPs into mouse and rat embryo fibroblasts did not, in itself, alter their growth. However, when coexpressed with oncogenic Ras (H-Ras(V12)), NASPs allowed rodent fibroblasts to overcome H-Ras(V12)-mediated p53-dependent senescence and acquire a transformed tumorigenic phenotype. Consistent with their ability to cooperate with oncogenic Ras in cell transformation, NASP expression reduced the transactivation activity of p53. This system provides an in vitro model of NF-κB-driven carcinogenesis and suggests that the known carcinogenic effects of inflammation may be at least partially due to NF-κB-mediated abrogation of oncogene-induced senescence.

Giovannetti E, Giaccone G
CYB5A and autophagy-mediated cell death in pancreatic cancer.
Autophagy. 2014; 10(4):697-8 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
The highly invasive and chemoresistant phenotype of pancreatic cancer highlights the urgency to identify prognostic biomarkers and novel therapeutic targets. Recently, we observed a significant correlation between shorter survival and loss of the cytoband 18q22.3. Here we investigated genes encoded by this cytoband, and demonstrated the prognostic value of CYB5A in resected and metastatic patients. Furthermore, our in vitro and in vivo studies clarified CYB5A inhibitory activity of oncogenic phenotypes through autophagy induction. This raises the possibility that inhibition of CYB5A-deregulated downstream pathways, such as those involving TRAF6, may favor autophagy-mediated cancer cell death in selected subgroups of patients.

Zhan Z, Xie X, Cao H, et al.
Autophagy facilitates TLR4- and TLR3-triggered migration and invasion of lung cancer cells through the promotion of TRAF6 ubiquitination.
Autophagy. 2014; 10(2):257-68 [PubMed] Related Publications
Autophagy contributes to the pathogenesis of cancer, whereas toll-like receptors (TLRs) also play an important role in cancer development and immune escape. However, little is known about the potential interaction between TLR signaling and autophagy in cancer cells. Here we show that autophagy induced by TLR4 or TLR3 activation enhances various cytokine productions through promoting TRAF6 (TNF receptor-associated factor 6, E3 ubiquitin protein ligase) ubiquitination and thus facilitates migration and invasion of lung cancer cells. Stimulation of TLR4 and TLR3 with lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid [poly(I:C)] respectively triggered autophagy in lung cancer cells. This was mediated by the adaptor protein, toll-like receptor adaptor molecule 1 (TICAM1/TRIF), and was required for TLR4- and TLR3-induced increases in the production of IL6, CCL2/MCP-1 [chemokine (C-C motif) ligand 2], CCL20/MIP-3α [chemokine (C-C motif) ligand 20], VEGFA (vascular endothelial growth factor A), and MMP2 [matrix metallopeptidase 2 (gelatinase A, 72 kDa gelatinase, 72 kDa type IV collagenase)]. These cytokines appeared to be necessary for enhanced migration and invasion of lung cancer cells upon TLR activation. Remarkably, inhibition of autophagy by chemical or genetic approaches blocked TLR4- or TLR3-induced Lys63 (K63)-linked ubiquitination of TRAF6 that was essential for activation of MAPK and NFKB (nuclear factor of kappa light polypeptide gene enhancer in B-cells) pathways, both of which were involved in the increased production of the cytokines. Collectively, these results identify induction of autophagy by TLR4 and TLR3 as an important mechanism that drives lung cancer progression, and indicate that inhibition of autophagy may be a useful strategy in the treatment of lung cancer.

Hung PS, Liu CJ, Chou CS, et al.
miR-146a enhances the oncogenicity of oral carcinoma by concomitant targeting of the IRAK1, TRAF6 and NUMB genes.
PLoS One. 2013; 8(11):e79926 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
MicroRNAs are short non-coding RNAs that regulate gene expression and are crucial to tumorigenesis. Oral squamous cell carcinoma (OSCC) is a prevalent malignancy worldwide. Up-regulation of miR-146 has been identified in OSCC tissues. However, the roles of miR-146 in carcinogenesis are controversial as it is suppressive in many other malignancies. The present study investigated the pathogenic implications of miR-146a in oral carcinogenesis. Microdissected OSCC exhibits higher levels of miR-146a expression than matched adjacent mucosal cells. The plasma miR-146a levels of patients are significantly higher than those of control subjects; these levels decrease drastically after tumor resection. miR-146a levels in tumors and in patients' plasma can be used to classify OSCC and non-disease status (sensitivity: >0.72). Exogenous miR-146a expression is significantly increased in vitro oncogenic phenotypes as well as during xenograft tumorigenesis and OSCC metastasis. The plasma miR-146a levels of these mice parallel the xenograft tumor burdens of the mice. A miR-146a blocker abrogates the growth of xenograft tumors. miR-146a oncogenic activity is associated with down-regulation of IRAK1, TRAF6 and NUMB expression. Furthermore, miR-146a directly targets the 3'UTR of NUMB and a region within the NUMB coding sequence when suppressing NUMB expression. Exogenous NUMB expression attenuates OSCC oncogenicity. Double knockdown of IRAK1 and TRAF6, and of TRAF6 and NUMB, enhance the oncogenic phenotypes of OSCC cells. Oncogenic enhancement modulated by miR-146a expression is attenuated by exogenous IRAK1 or NUMB expression. This study shows that miR-146a expression contributes to oral carcinogenesis by targeting the IRAK1, TRAF6 and NUMB genes.

Giovannetti E, Wang Q, Avan A, et al.
Role of CYB5A in pancreatic cancer prognosis and autophagy modulation.
J Natl Cancer Inst. 2014; 106(1):djt346 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
BACKGROUND: Loss of 18q22.3 is a prognostic marker in pancreatic ductal adenocarcinoma (PDAC). This study investigated genes encoded by this cytoband.
METHODS: We studied mRNA/protein expression in radically resected (n = 130) and metastatic patients (n = 50). The role of CYB5A was tested in 11 PDAC cell lines and five primary cultures through retrovirus-mediated upregulation and small interfering RNA using wound-healing, invasion, annexin-V, electron microscopy, and autophagic assays, as well as autophagy genes and kinases arrays. CYB5A+ orthotopic models (n = 6 mice/group) were monitored by Firefly and Gaussia-luciferase bioluminescence, magnetic resonance imaging, and high-frequency ultrasound. Data were analyzed by t test, Fisher exact-test, log-rank test and Cox proportional hazards models. All statistical tests were two-sided.
RESULTS: Both resected and metastatic patients with low mRNA or protein expression of CYB5A had statistically significantly shorter survival (eg, median = 16.7 months, 95% confidence interval [CI] = 13.5 to 19.9; vs median = 24.8 months, 95% CI = 12.8 to 36.9; P = .02, two-sided log-rank test; n = 82 radically resected PDACs), and multivariable analyses confirmed prognostic relevance. Moreover, we characterized a novel function to CYB5A, autophagy induction, concomitant with reduced proliferation and migration/invasion of PDAC cells. Network analysis of proautophagic pathways suggested CYB5A interaction with TRAF6, which was confirmed by TRAF6 downregulation after CYB5A reconstitution (-69% in SU.86.86-CYB5A+; P = .005, two-sided t test). CYB5A silencing had opposite effects, restoring TRAF6 expression and wound healing. In vivo studies showed that CYB5A induced autophagy while inhibiting tumor growth/metastasis and increasing survival (median = 57 days, 95% CI = 52 to 61; vs median = 44 days, 95% CI = 21 to 57; P = .03, two-sided log-rank test).
CONCLUSIONS: These results define CYB5A as a novel prognostic factor for PDAC that exerts its tumor-suppressor function through autophagy induction and TRAF6 modulation.

Han Q, Yao F, Zhong C, Zhao H
TRAF6 promoted the metastasis of esophageal squamous cell carcinoma.
Tumour Biol. 2014; 35(1):715-21 [PubMed] Related Publications
Esophageal cancer is one of the most aggressive malignancies and has been ranked as the sixth leading cause of cancer-related death in the world. It is very urgent to find new therapeutic targets. Although tumor necrosis factor receptor-associated factor 6 (TRAF6) was initially identified as an adaptor for NF-κB signaling, recently it has been found to be involved in cancer by modulating various signaling pathways. In the previous study, we have found that TRAF6 promoted the growth of esophageal squamous cell carcinoma (ESCC) cell in vitro and in vivo. However, the effects of TRAF6 on the migration and metastasis of ESCC cells are poorly understood. Here, we found that TRAF6 promoted migration and metastasis of ESCC cells through modulating Ras signaling. Overexpression of TRAF6 promoted the migration of ESCC cells and immortalized esophageal epithelial cells, while knock down the expression of TRAF6 inhibited the migration and metastasis of ESCC cells in vitro and in vivo. Mechanically, TRAF6 binds Ras with its N-terminal and activated Ras signaling. Taken together, TRAF6 played an important role in the metastasis of ESCC and might be a promising therapeutic target.

Yao F, Han Q, Zhong C, Zhao H
TRAF6 promoted the tumorigenicity of esophageal squamous cell carcinoma.
Tumour Biol. 2013; 34(5):3201-7 [PubMed] Related Publications
Esophageal squamous cell carcinoma (ESCC) is one of the most common malignancies worldwide. It is very urgent to understand the underlying molecular mechanism and develop new therapeutic strategy. Tumor necrosis factor receptor-associated factor (TRAF6), initially identified as a regulator of NF-κB, recently has been found to be involved in cancer by modulating various signaling pathways. However, the function of TRAF6 in ESCC is poorly understood. Here, we found that the expression of TRAF6 was upregulated in ESCC cell lines and clinical samples. Moreover, over-expression of TRAF6 in ESCC cells promoted cell proliferation, while downregulation of TRAF6 impaired the tumorigenicity of ESCC cells in vitro and in vivo. Mechanistically, TRAF6 inhibited cell apoptosis by downregulation of activated caspase 3 and cleaved poly ADP ribose polymerase and upregulation of c-Jun, Bcl2, and c-Myc. Taken together, our study suggested the oncogenic role of TRAF6 in ESCC, and TRAF6 might be an important therapeutic target for ESCC.

Xu Z, Pei L, Wang L, et al.
Snail1-dependent transcriptional repression of Cezanne2 in hepatocellular carcinoma.
Oncogene. 2014; 33(22):2836-45 [PubMed] Related Publications
High malignancy and early metastasis are the hallmarks of hepatocellular carcinoma (HCC). Here, we report that Cezanne2 expression is downregulated in HCC cells and in HCC patients' tumorous tissues and that Cezanne2 is inversely associated with Snail1 expression in HCC patients' tumorous tissues. Chromatin immunoprecipitation assays and the reporter gene assay showed that Snail1 binds to the promoter of the Cezanne2 gene and mediates the direct consequence of Cezanne2 repression. Enhanced expression of Cezanne2 could suppress proliferation, migration and invasion in HCC cells. Further, Cezanne2 could regulate MMP (matrix metalloproteinase)2, MMP9 and ICAM1 (intercellular adhesion molecule) levels through modulation of the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cell) signaling cascade. Co-immunoprecipitation and in vivo deubiquitination assay indicated that Cezanne2 interacts with TNF receptor-associated factor (TRAF)6 and cleaves the polyubiquitin from TRAF6 substrates. Our data reveal that Snail1-mediated suppression of Cezanne2 may have a key role in HCC malignancy.

Dahan J, Nouët Y, Jouvion G, et al.
LIM-only protein FHL2 activates NF-κB signaling in the control of liver regeneration and hepatocarcinogenesis.
Mol Cell Biol. 2013; 33(16):3299-308 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Four-and-a-half LIM-only protein 2 (FHL2) is an important mediator in many signaling pathways. In this study, we analyzed the functions of FHL2 in nuclear factor κB (NF-κB) signaling in the liver. We show that FHL2 enhanced tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) activity in transcriptional activation of NF-κB targets by stabilizing the protein. TRAF6 is a binding partner of FHL2 and an important component of the Toll-like receptor-NF-κB pathway. Knockdown of FHL2 in 293-hTLR4/MD2-CD14 cells impaired lipopolysaccharide (LPS)-induced NF-κB activity, which regulates expression of inflammatory cytokines. Indeed, FHL2(-/-) macrophages showed significantly reduced production of TNF and interleukin 6 (IL-6) following LPS stimulation. TNF and IL-6 are the key cytokines that prime liver regeneration after hepatic injury. Following partial hepatectomy, FHL2(-/-) mice exhibited diminished induction of TNF and IL-6 and delayed hepatocyte regeneration. In the liver, NF-κB signaling orchestrates inflammatory cross talk between hepatocytes and hepatic immune cells that promote chemical hepatocarcinogenesis. We found that deficiency of FHL2 reduced susceptibility to diethylnitrosamine-induced hepatocarcinogenesis, correlating with the activator function of FHL2 in NF-κB signaling. Our findings demonstrate FHL2 as a positive regulator of NF-κB activity in liver regeneration and carcinogenesis and highlight the importance of FHL2 in both hepatocytes and hepatic immune cells.

Yingjie L, Jian T, Changhai Y, Jingbo L
Numblike regulates proliferation, apoptosis, and invasion of lung cancer cell.
Tumour Biol. 2013; 34(5):2773-80 [PubMed] Related Publications
Numblike (Numbl), a conserved homolog of Drosophila Numb, has been proved to be implicated in early development of the nervous system. A recent study also showed that Numbl played an important role in tumorigenesis and invasion by suppressing NF-κB activation. However, the biological role of Numbl remains unknown in lung cancer up to now. To address the expression of Numbl in the lung cancer cell, four lung cancer cell lines (metastatic cell lines NCI-H292, 95-D, and non-metastatic cell lines A549, HCC827) and non-cancerous human bronchial epithelial cells were used to detect the protein expression of Numbl by western blotting. The results in this study indicated that the expression of Numbl was downregulated in human lung cancer cell lines, especially in metastatic cell lines. To investigate the role of Numbl in lung cancer cell proliferation, apoptosis, and invasion, we generated human lung cancer 95-D cell lines in which Numbl was either overexpressed or depleted. Subsequently, the effects of Numbl on the cell viability, cycle, apoptosis, and invasion properties in 95-D cells were determined with MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay, flow cytometry analysis, and Transwell invasion assays. The results indicated that Numbl could decrease cell viability, suppress cell proliferation and invasion, and promote cell apoptosis. In addition, we investigated the effects of Numbl on the expression of the following proteins: TRAF6 (tumor necrosis factor receptor-associated factor 6), p-p65 (phosphor-NF-κB), cyclin D1, caspase-3, and matrix metalloproteinase 9 (MMP9). Results showed that Numbl could decrease the expression of TRAF6, p-p65, cyclin D1, and MMP9 and increase the expression of caspase-3. All these results suggested that Numbl might be involved in the inhibition of growth, proliferation, and invasion of 95-D cells, as well as the potentiation of apoptosis of 95-D cells by abrogating TRAF6-induced activation of NF-κB.

An J, Liu H, Magyar CE, et al.
Hyperactivated JNK is a therapeutic target in pVHL-deficient renal cell carcinoma.
Cancer Res. 2013; 73(4):1374-85 [PubMed] Related Publications
Clear cell renal cell carcinomas (RCC), the major histologic subtype of RCC accounting for more than 80% of cases, are typified by biallelic inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene. Although accumulation of hypoxia-inducible factor alpha (HIF-α) is the most well-studied effect of VHL inactivation, direct inhibition of HIFα or restoration of wild-type pVHL protein expression has not proved readily feasible, given the limitations associated with pharmacologic targeting of transcription factors (i.e., HIF-α) and gene replacement therapy of tumor suppressor genes (i.e., VHL). Here, we have established that phosphorylated c-Jun, a substrate of the c-Jun-NH(2)-kinase (JNK), is selectively activated in clear cell RCC patient specimens. Using multiple isogenic cell lines, we show that HIF-α-independent JNK hyperactivation is unique to the pVHL-deficient state. Importantly, pVHL-deficient RCCs are dependent upon JNK activity for in vitro and in vivo growth. A multistep signaling pathway that links pVHL loss to JNK activation involves the formation of a CARD9/BCL10/TRAF6 complex as a proximal signal to sequentially stimulate TAK1 (MAPKKK), MKK4 (MAPKK), and JNK (MAPK). JNK stimulates c-Jun phosphorylation, activation, and dimerization with c-Fos to form a transcriptionally competent AP1 complex that drives transcription of the Twist gene and induces epithelial-mesenchymal transition. Thus, JNK represents a novel molecular target that is selectively activated in and drives the growth of pVHL-deficient clear cell RCCs. These findings can serve as the preclinical foundation for directed efforts to characterize potent pharmacologic inhibitors of the JNK pathway for clinical translation.

Peng Z, Shuangzhu Y, Yongjie J, et al.
TNF receptor-associated factor 6 regulates proliferation, apoptosis, and invasion of glioma cells.
Mol Cell Biochem. 2013; 377(1-2):87-96 [PubMed] Related Publications
Tumor necrosis factor receptor-associated factor 6 (TRAF6), which plays an important role in inflammation and immune response, is an essential adaptor protein for the NF-κB (nuclear factor κB) signaling pathway. Recent studies have shown that TRAF6 played an important role in tumorigenesis and invasion by suppressing NF-κB activation. However, up to now, the biologic role of TRAF6 in glioma has still remained unknown. To address the expression of TRAF6 in glioma cells, four glioma cell lines (U251, U-87MG, LN-18, and U373) and a non-cancerous human glial cell line SVG p12 were used to explore the protein expression of TRAF6 by Western blot. Our results indicated that TRAF6 expression was upregulated in human glioma cell lines, especially in metastatic cell lines. To investigate the role of TRAF6 in cell proliferation, apoptosis, invasion, and migration of glioma, we generated human glioma U-87MG cell lines in which TRAF6 was either overexpressed or depleted. Subsequently, the effects of TRAF6 on cell viability, cell cycle distribution, apoptosis, invasion, and migration in U-87MG cells were determined with 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry analysis, transwell invasion assay, and wound-healing assay. The results showed that knockdown of TRAF6 could decrease cell viability, suppress cell proliferation, invasion and migration, and promote cell apoptosis, whereas overexpression of TRAF6 displayed the opposite effects. In addition, the effects of TRAF6 on the expression of phosphor-NF-κB (p-p65), cyclin D1, caspase 3, and MMP-9 were also probed. Knockdown of TRAF6 could lower the expression of p-p65, cyclin D1, and MMP-9, and raise the expression of caspase 3. All these results suggested that TRAF6 might be involved in the potentiation of growth, proliferation, invasion, and migration of U-87MG cell, as well as inhibition of apoptosis of U-87MG cell by abrogating activation of NF-κB.

Johns N, Stephens NA, Preston T
Muscle protein kinetics in cancer cachexia.
Curr Opin Support Palliat Care. 2012; 6(4):417-23 [PubMed] Related Publications
PURPOSE OF REVIEW: Skeletal muscle loss appears to be the most significant event in cancer cachexia and is associated with a poor outcome. The balance between mechanisms that control synthesis and degradation is fundamental when designing new therapies. This review aims to highlight the molecular mechanisms that are associated with protein kinetics.
RECENT FINDINGS: The mechanisms that promote muscle synthesis have been explored in detail recently but moreover they have been the mechanisms behind degradation. Specific advances in cellular signalling molecules related to autophagy pathways including signal transducer and activators of transcription-3, activin type-2 receptor, TRAF6, and transcriptomic research have been given special attention in this review to highlight their roles in degradation and as potential targets for therapeutics. Ways to quantify muscle loss are badly needed for outcome measures; recent research using radiolabelled amino acids has also been discussed in this review.
SUMMARY: Only by having an appreciation of the complex regulation of muscle protein synthesis and degradation, will potential new therapeutics be able to be developed. This review identifies known targets in molecular pathways of current interest, explores methods used to find novel genes which may be involved in muscle kinetics and also highlights ways in which muscle kinetics may be measured to assess the efficacy of such interventions.

Iyer A, Zurolo E, Prabowo A, et al.
MicroRNA-146a: a key regulator of astrocyte-mediated inflammatory response.
PLoS One. 2012; 7(9):e44789 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Increasing evidence supports the involvement of microRNAs (miRNA) in the regulation of inflammation in human neurological disorders. In the present study we investigated the role of miR-146a, a key regulator of the innate immune response, in the modulation of astrocyte-mediated inflammation. Using Taqman PCR and in situ hybridization, we studied the expression of miR-146a in epilepsy-associated glioneuronal lesions which are characterized by prominent activation of the innate immune response. In addition, cultured human astrocytes were used to study the regulation of miR-146a expression in response to proinflammatory cytokines. qPCR and western blot were used to evaluate the effects of overexpression or knockdown of miR-146a on IL-1β signaling. Downstream signaling in the IL-1β pathway, as well as the expression of IL-6 and COX-2 were evaluated by western blot and ELISA. Release several cytokines was evaluated using a human magnetic multiplex cytokine assay on a Luminex® 100™/200™ platform. Increased expression of miR-146a was observed in glioneuronal lesions by Taqman PCR. MiR-146a expression in human glial cell cultures was strongly induced by IL-1β and blocked by IL-1β receptor antagonist. Modulation of miR-146a expression by transfection of astrocytes with anti-miR146a or mimic, regulated the mRNA expression levels of downstream targets of miR-146a (IRAK-1, IRAK-2 and TRAF-6) and the expression of IRAK-1 protein. In addition, the expression of IL-6 and COX-2 upon IL-1β stimulation was suppressed by increased levels of miR-146a and increased by the reduction of miR-146a. Modulation of miR-146a expression affected also the release of several cytokines such as IL-6 and TNF-α. Our observations indicate that in response to inflammatory cues, miR-146a was induced as a negative-feedback regulator of the astrocyte-mediated inflammatory response. This supports an important role of miR-146a in human neurological disorders associated with chronic inflammation and suggests that this miR may represent a novel target for therapeutic strategies.

Sun YS, Ye ZY, Qian ZY, et al.
Expression of TRAF6 and ubiquitin mRNA in skeletal muscle of gastric cancer patients.
J Exp Clin Cancer Res. 2012; 31:81 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
OBJECTIVE: To investigate the prognostic significance of tumor necrosis factor receptor (TNFR),-associated factor 6 (TRAF6),-and ubiquitin in gastric cancer patients.
METHODS: Biopsies of the rectus abdominis muscle were obtained intra operatively from 102 gastric cancer patients and 29 subjects undergoing surgery for benign abdominal diseases, and muscle TRAF6 and ubiquitin mRNA expression and proteasome proteolytic activities were assessed.
RESULTS: TRAF6 was significantly upregulated in muscle of gastric cancer compared with the control muscles. TRAF6 was upregulated in 67.65% (69/102) muscle of gastric cancer. Over expression of TRAF6 in muscles of gastric cancer were associated with TNM stage, level of serum albumin and percent of weight loss. Ubiquitin was significantly upregulated in muscle of gastric cancer compared with the control muscles. Ubiquitin was upregulated in 58.82% (60/102) muscles of gastric cancer. Over expression of ubiquitin in muscles of gastric cancer were associated with TNM (Tumor-Node-Metastasis) stage and weight loss. There was significant relation between TRAF6 and ubiquitin expression.
CONCLUSIONS: We found a positive correlation between TRAF6 and ubiquitin expression, suggesting that TRAF6 may up regulates ubiquitin activity in cancer cachexia. While more investigations are required to understand its mechanisms of TRAF6 and ubiquitin in skeletal muscle. Correct the catabolic-anabolic imbalance is essential for the effective treatment of cancer cachexia.

Shkoda A, Town JA, Griese J, et al.
The germinal center kinase TNIK is required for canonical NF-κB and JNK signaling in B-cells by the EBV oncoprotein LMP1 and the CD40 receptor.
PLoS Biol. 2012; 10(8):e1001376 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
The tumor necrosis factor-receptor-associated factor 2 (TRAF2)- and Nck-interacting kinase (TNIK) is a ubiquitously expressed member of the germinal center kinase family. The TNIK functions in hematopoietic cells and the role of TNIK-TRAF interaction remain largely unknown. By functional proteomics we identified TNIK as interaction partner of the latent membrane protein 1 (LMP1) signalosome in primary human B-cells infected with the Epstein-Barr tumor virus (EBV). RNAi-mediated knockdown proved a critical role for TNIK in canonical NF-κB and c-Jun N-terminal kinase (JNK) activation by the major EBV oncoprotein LMP1 and its cellular counterpart, the B-cell co-stimulatory receptor CD40. Accordingly, TNIK is mandatory for proliferation and survival of EBV-transformed B-cells. TNIK forms an activation-induced complex with the critical signaling mediators TRAF6, TAK1/TAB2, and IKKβ, and mediates signalosome formation at LMP1. TNIK directly binds TRAF6, which bridges TNIK's interaction with the C-terminus of LMP1. Separate TNIK domains are involved in NF-κB and JNK signaling, the N-terminal TNIK kinase domain being essential for IKKβ/NF-κB and the C-terminus for JNK activation. We therefore suggest that TNIK orchestrates the bifurcation of both pathways at the level of the TRAF6-TAK1/TAB2-IKK complex. Our data establish TNIK as a novel key player in TRAF6-dependent JNK and NF-κB signaling and a transducer of activating and transforming signals in human B-cells.

Fang J, Rhyasen G, Bolanos L, et al.
Cytotoxic effects of bortezomib in myelodysplastic syndrome/acute myeloid leukemia depend on autophagy-mediated lysosomal degradation of TRAF6 and repression of PSMA1.
Blood. 2012; 120(4):858-67 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Bortezomib (Velcade) is used widely for the treatment of various human cancers; however, its mechanisms of action are not fully understood, particularly in myeloid malignancies. Bortezomib is a selective and reversible inhibitor of the proteasome. Paradoxically, we find that bortezomib induces proteasome-independent degradation of the TRAF6 protein, but not mRNA, in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) cell lines and primary cells. The reduction in TRAF6 protein coincides with bortezomib-induced autophagy, and subsequently with apoptosis in MDS/AML cells. RNAi-mediated knockdown of TRAF6 sensitized bortezomib-sensitive and -resistant cell lines, underscoring the importance of TRAF6 in bortezomib-induced cytotoxicity. Bortezomib-resistant cells expressing an shRNA targeting TRAF6 were resensitized to the cytotoxic effects of bortezomib due to down-regulation of the proteasomal subunit α-1 (PSMA1). To determine the molecular consequences of loss of TRAF6 in MDS/AML cells, in the present study, we applied gene-expression profiling and identified an apoptosis gene signature. Knockdown of TRAF6 in MDS/AML cell lines or patient samples resulted in rapid apoptosis and impaired malignant hematopoietic stem/progenitor function. In summary, we describe herein novel mechanisms by which TRAF6 is regulated through bortezomib/autophagy-mediated degradation and by which it alters MDS/AML sensitivity to bortezomib by controlling PSMA1 expression.

Matta H, Gopalakrishnan R, Graham C, et al.
Kaposi's sarcoma associated herpesvirus encoded viral FLICE inhibitory protein K13 activates NF-κB pathway independent of TRAF6, TAK1 and LUBAC.
PLoS One. 2012; 7(5):e36601 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
BACKGROUND: Kaposi's sarcoma associated herpesvirus encoded viral FLICE inhibitory protein (vFLIP) K13 activates the NF-κB pathway by binding to the NEMO/IKKγ subunit of the IκB kinase (IKK) complex. However, it has remained enigmatic how K13-NEMO interaction results in the activation of the IKK complex. Recent studies have implicated TRAF6, TAK1 and linear ubiquitin chains assembled by a linear ubiquitin chain assembly complex (LUBAC) consisting of HOIL-1, HOIP and SHARPIN in IKK activation by proinflammatory cytokines.
METHODOLOGY/PRINCIPAL FINDINGS: Here we demonstrate that K13-induced NF-κB DNA binding and transcriptional activities are not impaired in cells derived from mice with targeted disruption of TRAF6, TAK1 and HOIL-1 genes and in cells derived from mice with chronic proliferative dermatitis (cpdm), which have mutation in the Sharpin gene (Sharpin(cpdm/cpdm)). Furthermore, reconstitution of NEMO-deficient murine embryonic fibroblast cells with NEMO mutants that are incapable of binding to linear ubiquitin chains supported K13-induced NF-κB activity. K13-induced NF-κB activity was not blocked by CYLD, a deubiquitylating enzyme that can cleave linear and Lys63-linked ubiquitin chains. On the other hand, NEMO was required for interaction of K13 with IKK1/IKKα and IKK2/IKKβ, which resulted in their activation by "T Loop" phosphorylation.
CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that K13 activates the NF-κB pathway by binding to NEMO which results in the recruitment of IKK1/IKKα and IKK2/IKKβ and their subsequent activation by phosphorylation. Thus, K13 activates NF-κB via a mechanism distinct from that utilized by inflammatory cytokines. These results have important implications for the development of therapeutic agents targeting K13-induced NF-κB for the treatment of KSHV-associated malignancies.

Li Z, Xiao J, Wu X, et al.
Plumbagin inhibits breast tumor bone metastasis and osteolysis by modulating the tumor-bone microenvironment.
Curr Mol Med. 2012; 12(8):967-81 [PubMed] Related Publications
Bone metastasis is a common and serious consequence of breast cancer. Bidirectional interaction between tumor cells and the bone marrow microenvironment drives a so-called 'vicious cycle' that promotes tumor cell malignancy and stimulates osteolysis. Targeting these interactions and pathways in the tumor-bone microenvironment has been an encouraging strategy for bone metastasis therapy. In the present study, we examined the effects of plumbagin on breast cancer bone metastasis. Our data indicated that plumbagin inhibited cancer cell migration and invasion, suppressed the expression of osteoclast-activating factors, altered the cancer cell induced RANKL/OPG ratio in osteoblasts, and blocked both cancer cell- and RANKL-stimulated osteoclastogenesis. In mouse model of bone metastasis, we further demonstrated that plumbagin significantly repressed breast cancer cell metastasis and osteolysis, inhibited cancer cell induced-osteoclastogenesis and the secretion of osteoclast-activating factors in vivo. At the molecular level, we found that plumbagin abrogated RANKL-induced NF-κB and MAPK pathways by blocking RANK association with TRAF6 in osteoclastogenesis, and by inhibiting the expression of osteoclast-activating factors through the suppression of NF-κB activity in breast cancer cells. Taken together, our data demonstrate that plumbagin inhibits breast tumor bone metastasis and osteolysis by modulating the tumor-bone microenvironment and that plumbagin may serve as a novel agent in the treatment of tumor bone metastasis.

Liu H, Tamashiro S, Baritaki S, et al.
TRAF6 activation in multiple myeloma: a potential therapeutic target.
Clin Lymphoma Myeloma Leuk. 2012; 12(3):155-63 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Multiple myeloma (MM) is an incurable B-lymphocyte malignancy. New therapeutic options have become available during the past several years; however nearly all patients acquire resistance to currently available therapeutic agents. Mechanisms contributing to the pathogenesis and chemoresistance of MM include genetic abnormalities, chromosomal translocations, gene mutations, the interaction between MM cells and the bone marrow microenvironment, and defects in the apoptotic signaling pathways. Survival signaling pathways associated with the pathogenesis of MM and bone marrow stromal cells play crucial roles in promoting growth, survival, adhesion, immortalization, angiogenesis, and drug resistance. The receptor activator of nuclear factor-kappa B/receptor activator of nuclear factor-kappa B ligand/tumor necrosis factor receptor-associated factor (RANK/RANKL-TRAF6) signal pathway mediates osteolytic bone lesions through the activation of the NF-κB and Janus kinase/signal transducer and activator of transcription (JNK) pathways in osteoclast precursor cells and thus contributes to the main clinical manifestations of bone disease. TRAF6 has also been identified as a ligase for Akt ubiquitination and membrane recruitment and its phosphorylation on growth factor stimulation. The inhibition of TRAF6 by silencing RNA or by decoy peptides decreases MM tumor cell proliferation and increases apoptosis as well as bone resorption. Some proteasome inhibitors and benzoxadiazole derivatives showed inhibitory effects on the activity and function of TRAF6. Overall, we propose that TRAF6 may be considered as a potential therapeutic target for the treatment of MM.

Xiao N, Li H, Luo J, et al.
Ubiquitin-specific protease 4 (USP4) targets TRAF2 and TRAF6 for deubiquitination and inhibits TNFα-induced cancer cell migration.
Biochem J. 2012; 441(3):979-86 [PubMed] Related Publications
TRAF [TNF (tumour necrosis factor)-receptor-associated factor] 2 and 6 are essential adaptor proteins for the NF-κB (nuclear factor κB) signalling pathway, which play important roles in inflammation and immune response. Polyubiquitination of TRAF2 and TRAF6 is critical to their activities and functions in TNFα- and IL (interleukin)-1β-induced NF-κB activation. However, the regulation of TRAF2 and TRAF6 by deubiquitination remains incompletely understood. In the present study, we identified USP (ubiquitin-specific protease) 4 as a novel deubiquitinase targeting TRAF2 and TRAF6 for deubiquitination. We found that USP4 specifically interacts with TRAF2 and TRAF6, but not TRAF3. Moreover, USP4 associates with TRAF6 both in vitro and in vivo, independent of its deubiquitinase activity. The USP domain is responsible for USP4 to interact with TRAF6. Ectopic expression of USP4 inhibits the TRAF2- and TRAF6-stimulated NF-κB reporter gene and negatively regulates the TNFα-induced IκBα (inhibitor of NF-κBα) degradation and NF-κB activation. Knockdown of USP4 significantly increased TNFα-induced cytokine expression. Furthermore, we found that USP4 deubiquitinates both TRAF2 and TRAF6 in vivo and in vitro in a deubiquitinase activity-dependent manner. Importantly, the results of the present study showed that USP4 is a negative regulator of TNFα- and IL-1β-induced cancer cell migration. Taken together, the present study provides a novel insight into the regulation of the NF-κB signalling pathway and uncovers a previously unknown function of USP4 in cancer.

Santarpia M, Magri I, Sanchez-Ronco M, et al.
mRNA expression levels and genetic status of genes involved in the EGFR and NF-κB pathways in metastatic non-small-cell lung cancer patients.
J Transl Med. 2011; 9:163 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
BACKGROUND: Metastatic non-small-cell lung cancer (NSCLC) has a dismal prognosis. EGFR is overexpressed or mutated in a large proportion of cases. Downstream components of the EGFR pathway and crosstalk with the NF-κB pathway have not been examined at the clinical level. We explored the prognostic significance of the mRNA expression of nine genes in the EGFR and NF-κB pathways and of BRCA1 and RAP80 in patients in whom EGFR and K-ras gene status had previously been determined. In addition, NFKBIA and DUSP22 gene status was also determined.
METHODS: mRNA expression of the eleven genes was determined by QPCR in 60 metastatic NSCLC patients and in nine lung cancer cell lines. Exon 3 of NFKBIA and exon 6 of DUSP22 were analyzed by direct sequencing. Results were correlated with outcome to platinum-based chemotherapy in patients with wild-type EGFR and to erlotinib in those with EGFR mutations.
RESULTS: BRCA1 mRNA expression was correlated with EZH2, AEG-1, Musashi-2, CYLD and TRAF6 expression. In patients with low levels of both BRCA1 and AEG-1, PFS was 13.02 months, compared to 5.4 months in those with high levels of both genes and 7.7 months for those with other combinations (P=0.025). The multivariate analysis for PFS confirmed the prognostic role of high BRCA1/AEG-1 expression (HR, 3.1; P=0.01). Neither NFKBIA nor DUSP22 mutations were found in any of the tumour samples or cell lines.
CONCLUSIONS: The present study provides a better understanding of the behaviour of metastatic NSCLC and identifies the combination of BRCA1 and AEG-1 expression as a potential prognostic model.

Starczynowski DT, Lockwood WW, Deléhouzée S, et al.
TRAF6 is an amplified oncogene bridging the RAS and NF-κB pathways in human lung cancer.
J Clin Invest. 2011; 121(10):4095-105 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Somatic mutations and copy number alterations (as a result of deletion or amplification of large portions of a chromosome) are major drivers of human lung cancers. Detailed analysis of lung cancer-associated chromosomal amplifications could identify novel oncogenes. By performing an integrative cytogenetic and gene expression analysis of non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC) cell lines and tumors, we report here the identification of a frequently recurring amplification at chromosome 11 band p13. Within this region, only TNF receptor-associated factor 6 (TRAF6) exhibited concomitant mRNA overexpression and gene amplification in lung cancers. Inhibition of TRAF6 in human lung cancer cell lines suppressed NF-κB activation, anchorage-independent growth, and tumor formation. In these lung cancer cell lines, RAS required TRAF6 for its oncogenic capabilities. Furthermore, TRAF6 overexpression in NIH3T3 cells resulted in NF-κB activation, anchorage-independent growth, and tumor formation. Our findings show that TRAF6 is an oncogene that is important for RAS-mediated oncogenesis and provide a mechanistic explanation for the previously apparent importance of constitutive NF-κB activation in RAS-driven lung cancers.

Pryor JG, Brown-Kipphut BA, Iqbal A, Scott GA
Microarray comparative genomic hybridization detection of copy number changes in desmoplastic melanoma and malignant peripheral nerve sheath tumor.
Am J Dermatopathol. 2011; 33(8):780-5 [PubMed] Related Publications
Desmoplastic melanoma (DM) and malignant peripheral nerve sheath tumor (MPNST) can appear morphologically and immunophenotypically similar. We attempted to determine whether microarray comparative genomic hybridization could detect copy number differences between them to aid in the diagnosis. S-100 immunohistochemistry was performed on 5 cases of DM and 9 cases of MPNST using formalin-fixed paraffin-embedded specimens. Genomic DNA was extracted from microdissected cells. Whole genome amplification was performed on 5 of 5 DMs and 6 of 9 MPNST cases. A multiplex polymerase chain reaction assay was used to determine the quality of the DNA samples, which were run on the Spectral Chip 2600 bacterial artificial chromosome array platform. DM showed gains involving chromosomes 1p, 2p, 9q, 13q, 14q, and 20q and losses involving chromosomes 5p, 11p, 12q, 15q, and 18q. Several cancer-associated genes were involved, including gain of BCL2L1, ARTN, AMPK, NRAS, and CCNA1 and loss of IGF2, CDKN1C, PAX6, WT1, TRAF6, MAPK8IP1, and IMP3. MPNST had gains involving chromosomes 1p, 2q, and 19p and loss of chromosome 21q. Gains of MUM1, APC2, MAP2K2, JMJD2B, SP110, PTMA, GPI, and CDKN2D were detected. DM and MPNST have chromosomal alterations detected by array comparative genomic hybridization that might be useful in distinguishing these 2 tumors, although further studies with a larger sample size will be needed to test this.

Mu Y, Sundar R, Thakur N, et al.
TRAF6 ubiquitinates TGFβ type I receptor to promote its cleavage and nuclear translocation in cancer.
Nat Commun. 2011; 2:330 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Transforming growth factor β (TGFβ) is a pluripotent cytokine promoting epithelial cell plasticity during morphogenesis and tumour progression. TGFβ binding to type II and type I serine/threonine kinase receptors (TβRII and TβRI) causes activation of different intracellular signaling pathways. TβRI is associated with the ubiquitin ligase tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6). Here we show that TGFβ, via TRAF6, causes Lys63-linked polyubiquitination of TβRI, promoting cleavage of TβRI by TNF-alpha converting enzyme (TACE), in a PKCζ-dependent manner. The liberated intracellular domain (ICD) of TβRI associates with the transcriptional regulator p300 to activate genes involved in tumour cell invasiveness, such as Snail and MMP2. Moreover, TGFβ-induced invasion of cancer cells is TACE- and PKCζ- dependent and the TβRI ICD is localized in the nuclei of different kinds of tumour cells in tissue sections. Thus, our data reveal a specific role for TβRI in TGFβ mediated tumour invasion.

Paik JH, Jang JY, Jeon YK, et al.
MicroRNA-146a downregulates NFκB activity via targeting TRAF6 and functions as a tumor suppressor having strong prognostic implications in NK/T cell lymphoma.
Clin Cancer Res. 2011; 17(14):4761-71 [PubMed] Related Publications
PURPOSE: We investigated prognostic implications of microRNAs in extranodal NK/T cell lymphoma (NKTL).
EXPERIMENTAL DESIGN: We measured miRNA expression in NKTL tissues and cell lines, using real-time PCR, and analyzed its role in NKTL, using cell lines.
RESULTS: Multivariate analysis showed low miR-146a expression (P < 0.001; HR = 13.110), primary non-upper aerodigestive tract lesion (non-UAT; P = 0.008; HR = 5.376) and high International Prognostic Index (IPI; ≥3; P = 0.013; HR = 3.584) to be independent poor prognostic factors. miR-146a expression could subdivide UAT-NKTL into 2 prognostic groups, resulting in the following prognostic groups: (i) UAT(Low-146a), (ii) UAT(High-146a), and (iii) non-UAT. Compared with UAT(High-146a), UAT(Low-146a) showed distinctively poor prognosis (P < 0.001; HR = 15.620), similar to the non-UAT group. In vitro, miR-146a overexpression in NKTL cell lines, SNK6 and YT, inhibited nuclear factor κB (NFκB) activity, suppressed cell proliferation, induced apoptosis, and enhanced chemosensitivity. TNF receptor-associated factor 6, a target of miR-146a and a known NFκB activator, was downregulated by miR-146a in SNK6 and YT cells. Promoter methylation of miR-146a gene was observed in SNK6 and YT cells, as well as in NKTL tissues with low miR-146a expression, and miR-146a expression was induced by the conversion of methylation status with a demethylating agent in SNK6 and YT cells.
CONCLUSIONS: These results suggest that miR-146a might function as a potent tumor suppressor in NKTL and be useful for patient assessment and therapeutic targeting.

Boldin MP, Taganov KD, Rao DS, et al.
miR-146a is a significant brake on autoimmunity, myeloproliferation, and cancer in mice.
J Exp Med. 2011; 208(6):1189-201 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Excessive or inappropriate activation of the immune system can be deleterious to the organism, warranting multiple molecular mechanisms to control and properly terminate immune responses. MicroRNAs (miRNAs), ∼22-nt-long noncoding RNAs, have recently emerged as key posttranscriptional regulators, controlling diverse biological processes, including responses to non-self. In this study, we examine the biological role of miR-146a using genetically engineered mice and show that targeted deletion of this gene, whose expression is strongly up-regulated after immune cell maturation and/or activation, results in several immune defects. Collectively, our findings suggest that miR-146a plays a key role as a molecular brake on inflammation, myeloid cell proliferation, and oncogenic transformation.

Ma T, Wang N, Su Z, et al.
Characterization of apoptosis and proliferation in esophageal carcinoma EC109 cells following siRNA-induced down-regulation of TRAF6.
Mol Cell Biochem. 2011; 352(1-2):77-85 [PubMed] Related Publications
Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an activator of the NF-κB transcription factor. NF-κB is involved in a variety of inflammatory, anti-apoptotic, and gene regulatory pathways and was recently found to be over-expressed in esophageal cancer cells. Here we investigated the function of TRAF6 in the esophageal cancer cell line EC109. siRNA targeting TRAF6 was introduced into EC109 cells and TRAF6 mRNA and protein levels were subsequently examined via RT-PCR and western blotting. Rates of apoptosis and cell proliferation were also measured using flow cytometry, ethynyl deoxyuridine (EdU), and CCK-8 (Cell Counting Kit-8) assays. The real-time PCR array was applied to profile the expression of TRAF6 related genes. TRAF6-siRNA reduced TRAF6 mRNA and protein expressions. NF-κB p65 protein expression was decreased in TRAF6-targeting siRNA-transfected cells compared to cells of the negative control. TRAF6-siRNA also significantly inhibited proliferation and enhanced apoptosis of EC109 cells. These studies suggested that TRAF6 was required for NF-κB activation in EC109 cells and it may be a good molecular target for suppressing the survival and proliferation of esophageal cancer cells.

Sung B, Cho SG, Liu M, Aggarwal BB
Butein, a tetrahydroxychalcone, suppresses cancer-induced osteoclastogenesis through inhibition of receptor activator of nuclear factor-kappaB ligand signaling.
Int J Cancer. 2011; 129(9):2062-72 [PubMed] Article available free on PMC after 01/04/2015 Related Publications
Osteoclastogenesis is associated with aging and various age-related inflammatory chronic diseases, including cancer. Receptor activator of nuclear factor-kappaB (NF-κB) ligand (RANKL), a member of the tumor necrosis factor superfamily, has been implicated as a major mediator of bone resorption, suggesting that agents that can suppress RANKL signaling might inhibit osteoclastogenesis, a process closely linked to bone resorption. We therefore investigated whether butein, a tetrahydroxychalcone, could inhibit RANKL signaling and suppress osteoclastogenesis induced by RANKL or tumor cells. We found that human multiple myeloma cells (MM.1S and U266), breast tumor cells (MDA-MB-231) and prostate tumor cells (PC-3) induced differentiation of macrophages to osteoclasts, as indicated by tartrate-resistant acid phosphatase (TRAP)-positive cells, and that butein suppressed this process. The chalcone also suppressed the expression of RANKL by the tumor cells. We further found that butein suppressed RANKL-induced NF-κB activation and that this suppression correlated with the inhibition of IκBα kinase and suppression of phosphorylation and degradation of IκBα, an inhibitor of NF-κB. Finally, butein also suppressed the RANKL-induced differentiation of macrophages to osteoclasts in a dose-dependent and time-dependent manner. Collectively, our results indicate that butein suppresses the osteoclastogenesis induced by tumor cells and by RANKL, by suppression of the NF-κB activation pathway.

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