TRAF6 activation in multiple myeloma: a potential therapeutic target

The New Roles of traf6 Gene Involved in the Development of Zebrafish Liver and Gonads

Traf6, an adaptor protein, exhibits non-conventional E3 ubiquitin ligase activity and was well studied as an important factor in immune systems and cancerogenesis. In mice, the traf6-null caused a perinatal death, so that the underlying pathophysiology of traf6-defeciency is still largely unclear in animals. Here, in the present study, a traf6 knockout zebrafish line (traf6-/-) was generated and could survive until adulthood, providing a unique opportunity to demonstrate the functions of traf6 gene in animals' organogenesis beyond the mouse model. The body of traf6-/- fish was found to be significantly shorter than that of the wildtype (WT). Likewise, a comparative transcriptome analysis showed that 866 transcripts were significantly altered in the traf6-/- liver, mainly involved in the immune system, metabolic pathways, and progesterone-mediated oocyte maturation. Especially, the mRNA expression of the pancreas duodenum homeobox protein 1 (pdx1), glucose-6-phosphatase (g6pcb), and the vitellogenesis genes (vtgs) were significantly decreased in the traf6-/- liver. Subsequently, the glucose was found to be accumulated in the traf6-/- liver tissues, and the meiotic germ cell was barely detected in traf6-/- testis or ovary. The findings of this study firstly implied the pivotal functions of traf6 gene in the liver and gonads' development in fish species.

Tumor Necrosis Factor Receptor-Associated Factor 6 and Human Cancer: A Systematic Review of Mechanistic Insights, Functional Roles, and Therapeutic Potential

Cancer imposes a substantial burden and its incidence is persistently increasing in recent years. Cancer treatment has been difficult due to its inherently complex nature. The tumor microenvironment (TME) includes a complex interplay of cellular and noncellular constituents surrounding neoplastic cells, intricately contributing to the tumor initiation and progression. This critical aspect of tumors involves a complex interplay among cancer, stromal, and inflammatory cells, forming an inflammatory TME that promotes tumorigenesis across all stages. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is implicated in modulating various critical processes linked to tumor pathogenesis, including but not limited to the regulation of tumor cell proliferation, invasion, migration, and survival. Furthermore, TRAF6 prominently contributes to various immune and inflammatory pathways. The TRAF6-mediated activation of nuclear factor (NF)-κB in immune cells governs the production of proinflammatory cytokines. These cytokines sustain inflammation and stimulate tumor growth by activating NF-κB in tumor cells. In this review, we discuss various types of tumors, including gastrointestinal cancers, urogenital cancers, breast cancer, lung cancer, head and neck squamous cell carcinoma, uterine fibroids, and glioma. Employing a rigorous and systematic approach, we comprehensively evaluate the functional repertoire and potential roles of TRAF6 in various cancer types, thus highlighting TRAF6 as a compelling and emerging therapeutic target worthy of further investigation and development.

Inhibition of TRAF6 improves hyperlipidemic acute pancreatitis by alleviating pyroptosis in vitro and in vivo rat models

OBJECTIVE

Hypertriglyceridemia (HTG) is one of the common causes of acute pancreatitis (AP). Hyperlipidemic acute pancreatitis (HTG-AP) is associated with higher mortality owing to its tendency for greater severity and rapid progression. The purpose of this study was to explore the mechanism of involvement of tumor necrosis factor receptor-related factor 6 (TRAF6) in pyroptosis during HTG-AP.

METHODS

The HTG environment was simulated with palmitic acid treatment in vitro and a high-fat diet in vivo. Cerulein was used to establish the HTG-AP model, followed by genetic and pharmacological inhibition of TRAF6. Pyroptosis activation, inflammatory reaction, and the interaction between TRAF6 and pyroptosis in HTG-AP were assessed.

RESULTS

HTG was found to aggravate the development of pancreatitis, accompanied by increased pyroptosis and enhanced inflammatory response in HTG-AP models. Mechanistically, TRAF6 downregulation decreased the activation of pyroptosis in cerulein-induced HTG-AP.

CONCLUSION

Collectively, inhibition of TRAF6 improved HTG-AP and the associated inflammation by alleviating pyroptosis.

The roles of bone remodeling in normal hematopoiesis and age-related hematological malignancies

Prior research establishing that bone interacts in coordination with the bone marrow microenvironment (BMME) to regulate hematopoietic homeostasis was largely based on analyses of individual bone-associated cell populations. Recent advances in intravital imaging has suggested that the expansion of hematopoietic stem cells (HSCs) and acute myeloid leukemia cells is restricted to bone marrow microdomains during a distinct stage of bone remodeling. These findings indicate that dynamic bone remodeling likely imposes additional heterogeneity within the BMME to yield differential clonal responses. A holistic understanding of the role of bone remodeling in regulating the stem cell niche and how these interactions are altered in age-related hematological malignancies will be critical to the development of novel interventions. To advance this understanding, herein, we provide a synopsis of the cellular and molecular constituents that participate in bone turnover and their known connections to the hematopoietic compartment. Specifically, we elaborate on the coupling between bone remodeling and the BMME in homeostasis and age-related hematological malignancies and after treatment with bone-targeting approaches. We then discuss unresolved questions and ambiguities that remain in the field.

Novel Biomarkers for Diagnosis and Monitoring of Immune Thrombocytopenia

Lower-than-normal platelet counts are a hallmark of the acquired autoimmune illness known as immune thrombocytopenia, which can affect both adults and children. Immune thrombocytopenia patients' care has evolved significantly in recent years, but the disease's diagnosis has not, and it is still only clinically achievable with the elimination of other causes of thrombocytopenia. The lack of a valid biomarker or gold-standard diagnostic test, despite ongoing efforts to find one, adds to the high rate of disease misdiagnosis. However, in recent years, several studies have helped to elucidate a number of features of the disease's etiology, highlighting how the platelet loss is not only caused by an increase in peripheral platelet destruction but also involves a number of humoral and cellular immune system effectors. This made it possible to identify the role of immune-activating substances such cytokines and chemokines, complement, non-coding genetic material, the microbiome, and gene mutations. Furthermore, platelet and megakaryocyte immaturity indices have been emphasized as new disease markers, and prognostic signs and responses to particular types of therapy have been suggested. Our review's goal was to compile information from the literature on novel immune thrombocytopenia biomarkers, markers that will help us improve the management of these patients.

m6A-dependent upregulation of TRAF6 by METTL3 is associated with metastatic osteosarcoma

•

METTL3 is highly expressed in osteosarcoma.

•

METTL3 downregulation inhibits metastases of osteosarcoma cells.

•

m6A regulates osteosarcoma cell activity.

•

METTL3 modifies TRAF6 activity via m6A.

•

TRAF6 inhibits the repressive effects of sh-METTL3 on osteosarcoma metastases.

Objectives

RNA N6-methyladenosine (m6A) is associated with tumorigenesis. The importance of methyltransferase-like 3 (METTL3) has been reported in cancer progression and metastasis. However, its role and molecular mechanism in osteosarcoma (OS), the most common primary bone tumor, is poorly studied. In this study, we aimed to investigate the functional role and underlying mechanism of METTL3 in the metastasis of OS.

Methods

The expression differences of METTL3 between metastatic and non-metastatic OS tissues and patients with different Enneking stages were detected using RT-qPCR. METTL3 was artificially downregulated in the cells, followed by wound healing assay, Matrigel assay, immunofluorescence, in vivo tumorigenic assay, HE staining, and western blot. Transcriptome sequencing and m6A-seq was conducted to identify the downstream genes of METTL3, and RIP and dual-luciferase assays were performed for validation. The expression of TRAF6 in OS tissues was detected using RT-qPCR. Finally, the rescue experiments were conducted.

Results

METTL3 was overexpressed in metastatic OS tissues, and downregulation of METTL3 decreased cell migration, invasion, epithelial-mesenchymal transition, and tumorigenic and metastatic activities. The m6A site was highly enriched in cells poorly expressing METTL3, and the m6A peak was mainly enriched in the exon region. METTL3 was positively correlated with TRAF6 in metastatic OS, and depletion of METTL3 resulted in the loss of TRAF6 expression in OS cells. Upregulation of TRAF6 contributed to metastases in vitro and in vivo.

Conclusion

METTL3 is highly expressed in OS and enhances TRAF6 expression through m6A modification, thereby promoting the metastases of OS cells.

Benzoyl‑xanthone derivative induces apoptosis in MCF‑7 cells by binding TRAF6

TNF receptor-associated factor 6 (TRAF6) has been reported to be associated with the development of cancer. Nevertheless, the exact role of TRAF6 in cancer remains unclear. The purpose of the present study was to explore the mechanism of 2-benzoyl-3-hydroxy-4-methyl-9H-xanthen-9-one leading to the inhibition of the activation of AKT and TGF-β-activated kinase 1 (TAK1), and to the apoptosis of MCF-7 cells. Using a computational docking program and examination of AKT and TAK1 level changes, a new small molecule was identified, 2-benzoyl-3-hydroxy-4-methyl-9H-xanthen-9-one, which competitively bound to TRAF6. Next, the effect of this new compound on MCF-7 cells' biological behavior was studied in vitro. MTT assays were used to investigate cell viability; flow cytometry and invasion assays were performed to detect early apoptosis and invasion in MCF-7 cells, respectively. Immunoprecipitation, western blotting and caspase-3/9 activity assays were carried out to explore changes in protein expression. Briefly, the present data indicated that 2-benzoyl-3-hydroxy-4-methyl-9H-xanthen-9-one could suppress proliferation, induce early apoptosis and inhibit invasion in MCF-7 cells by suppressing the expression of Bcl-2 and promoting the expression of Bax, caspase-9, and caspase-3. These findings indicated that 2-benzoyl-3-hydroxy-4-methyl-9H-xanthen-9-one could induce apoptosis by inhibiting the activation of AKT and TAK1, and affecting the Bcl-2/Bax-caspase-9-caspase-3 pathway by competitively binding with TRAF6.

Protocatechualdehyde Inhibits the Osteoclast Differentiation of RAW264.7 and BMM Cells by Regulating NF-κB and MAPK Activity

Protocatechualdehyde (PCA), an important component of Salvia miltiorrhiza, has many activities, such as anti-inflammatory and antisepsis activities. However, the role of PCA in osteoclasts is not clear. We used RAW264.7 cells (a mouse leukemic monocyte/macrophage cell line) and bone marrow macrophages (BMMs) to probe the role of PCA in osteoclasts and the underlying mechanism. The effects of PCA on cell activity were evaluated with CCK-8 assays. TRAP staining detected mature osteoclasts. Corning Osteo Assay Surface plates were used to examine absorption. The levels of RNA and protein were analyzed, respectively, using RT-PCR and Western blotting. PCA (5 μg/ml) was not toxic to the two cell types but reduced the formation of osteoclasts and bone absorption. Furthermore, PCA restrained the expression of mRNAs encoding proteins associated with osteoclasts and reduced the phosphorylation of proteins in important signaling pathways. The results indicate that PCA inhibits osteoclast differentiation by suppressing NF-κB and MAPK activity.

Mechanism by which TRAF6 Participates in the Immune Regulation of Autoimmune Diseases and Cancer

Tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), an E3 ubiquitin ligase, is a signal transduction molecule shared by the interleukin-1 receptor (IL-1R)/Toll-like receptor (TLR) family and the TNFR superfamily. TRAF6 has a unique TRAF domain and RING finger domain that mediate intracellular signaling events. In the immune system, TRAF6-mediated signaling has been shown to be critical for the development, homeostasis, and activation of a variety of immune cells, including B cells, T cells, dendritic cells, and macrophages. Although the pathogenesis and etiology of autoimmune diseases and cancer are not fully understood, it is worth noting that existing studies have shown that TRAF6 is involved in the pathogenesis and development of a variety of these diseases. Herein, we reviewed the role of TRAF6 in certain immune cells, as well as the function and potential effect of TRAF6 in autoimmune diseases and cancer. Our review indicates that TRAF6 may be a novel target for autoimmune diseases and cancer.

The NEDD4-1 E3 ubiquitin ligase: A potential molecular target for bortezomib sensitivity in multiple myeloma

E3 ubiquitin ligases primarily determine the substrate specificity of the ubiquitin-proteasome system and play an essential role in the resistance to bortezomib in multiple myeloma (MM). Neural precursor cell-expressed developmentally downregulated gene 4-1 (NEDD4-1, also known as NEDD4) is a founding member of the NEDD4 family of E3 ligases and is involved in the proliferation, migration, invasion and drug sensitivity of cancer cells. In the present study, we investigated the role of NEDD4-1 in MM cells and explored its underlying mechanism. Clinically, low NEDD4-1 expression has been linked to poor prognosis in patients with MM. Functionally, NEDD4-1 knockdown (KD) resulted in bortezomib resistance in MM cells in vitro and in vivo. The overexpression (OE) of NEDD4-1, but not an enzyme-dead NEDD4-1-C867S mutant, had the opposite effect. Furthermore, the overexpression of NEDD4-1 in NEDD4-1 KD cells resensitized the cells to bortezomib in an add-back rescue experiment. Mechanistically, pAkt-Ser473 levels and Akt signaling were elevated and decreased by NEDD4-1 KD and OE, respectively. NEDD4-1 ubiquitinated Akt and targeted pAkt-Ser473 for proteasomal degradation. More importantly, the NEDD4-1 KD-induced upregulation of Akt expression sensitized MM cells to growth inhibition after treatment with an Akt inhibitor. Collectively, our results suggest that high NEDD4-1 levels may be a potential new therapeutic target in MM.

miR-545 promoted enterovirus 71 replication via directly targeting phosphatase and tensin homolog and tumor necrosis factor receptor-associated factor 6

Enterovirus 71 (EV71) is a small, nonenveloped icosahedral RNA virus and is the predominant causative pathogen of hand-foot-and-mouth disease. Recently, microRNAs (miRNAs) are reported to play important roles in the pathogenesis of EV71 replication. This study investigated the role of miR-545 in the EV71 replication and explored the underlying molecular mechanisms. We showed that miR-545 was upregulated in the EV71-infected human embryonic kidney (HEK) 293 cells and rhabdomyosarcoma (RD) cells. Overexpression of miR-545 promoted the viral replication of EV71 and attenuated the inhibitory effects of EV71 on cell viability in HEK293 and RD cells; while knockdown of miR-545 significantly suppressed the EV71 replication in these two cell lines. Bioinformatics analysis and luciferase reporter assay showed that miR-545 directly targeted the 3'untranslated region of phosphatase and tensin homolog (PTEN) and tumor necrosis factor receptor-associated factor 6 (TRAF6) in HEK293 cells. Furthermore, miR-545 negatively regulated the messenger RNA (mRNA) and protein expression of PTEN and TRAF6. The mRNA and protein expression of PTEN and TRAF6 was also suppressed by EV71 infection, which was attenuated by miR-545 knockdown in HEK293 cells. Overexpression of PTEN and TRAF6 both suppressed the EV71 replication in HKE293 cells, and also attenuated the enhanced effects of miR-545 overexpression on the EV71 replication in HEK293 cells. Collectively, our study for the first time showed that miR-545 had an enhanced effect on the EV71 replication in HEK293 and RD cells. Further mechanistic results indicated that miR-545 promoted EV71 replication at least partly via targeting PTEN and TRAF6.

IL-17A Increases Multiple Myeloma Cell Viability by Positively Regulating Syk Expression

PURPOSE: Elevated IL-17 produced by T_h17 cells was reported to promote myeloma cell growth and inhibit immune function in multiple myeloma (MM). IL-17A was also reported to promote MM growth through IL-17 receptors and enhance adhesion to bone marrow stromal cells (BMSCs). Spleen tyrosine kinase (Syk) influences MM cell survival and migration. Herein we aimed to investigate whether Syk was involved in the regulative role of IL-17A in the viability of MM cells. METHODS: Cell viability was determined using CCK8 assay. The production of cytokine including IL-17A was evaluated with ELISA. Western blotting assay was used to determine protein expression levels of Syk and nuclear factor κB (NF-κB) related molecules. mRNA expression level of RORγt was detected with reverse transcription quantitative polymerase chain reaction. RESULTS: IL-17Awas highly expressed in MM patients and was able to induce MM cell viability. Following analysis indicated that the effects of IL-17A were mediated by Syk/ nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. Immunoprecipitation also indicated that Syk is involved in IL-17A–induced Act1-TRAF6 complex formation and TRAF6 polyubiquitination in MM cells. CONCLUSIONS: Taken together, our study indicated that IL-17A increases MM cell viability through activating NF-κB signal pathway via positively regulating Syk expression. Syk also participates in the formation of IL-17R-proximal signaling complex (IL-17R-Act1-TRAF6), which is essential for IL-17A–mediated NF-kB activation. These investigations highlight that inhibition of Syk may be a potential therapeutic option for neoplastic diseases such as MM.

Targeting the cross-talk between the hedgehog and NF-κB signaling pathways in multiple myeloma

Multiple myeloma (MM) is an incurable plasma cell malignancy. Aberrant activation of the Hedgehog (Hh) and NF-κB signaling pathways is observed in MM and plays a pivotal role in the development of MM by promoting myeloma cell growth, survival, and drug resistance. In this study, we found that the Sonic Hh (SHh) ligand in the bone marrow microenvironment is responsible for the enhancement of NF-κB activity in MM cell lines NCI-H929 and U266. Notably, we discovered that Hh signaling regulates NF-κB through its classical pathway (SHh/PTCH1/SMO/GLI1) in MM cells. Meanwhile, non-classical pathway by SMO recruitment of TRAF6 to ubiquitination is also involved in it. Moreover, the SMO inhibitor cyclopamine enhances the cytotoxic effects of bortezomib in MM cell lines. Our study reveals the cross-talk between Hh members and the NF-κB pathway in the myeloma cells and provides a theoretical basis for combined utilization of Hh members and proteasome inhibition in MM.

A biomarker and therapeutical target in immune thrombocytopenia: TNF receptor-associated factor 6

Background: Immune thrombocytopenia (ITP) is an acquired disease characterized by various pathogenetic mechanisms. We aimed to evaluate the value of TRAF6 as a biomarker of pathogenesis in ITP. Methods: 85 newly diagnosed ITP patients and 85 controls were included. Results: In the patient group, mean TRAF6 level was 2348 pg/ml and in the control group, TRAF6 level was 25.57 pg/ml. In corticosteroid-responding patients, TRAF6 levels were lower than nonresponding patients. Discussion: TRAF6 levels were observed to be higher than healthy controls, which suggest a solid relation with ITP pathogenesis. The observation that in patients who present with high TRAF6 levels, there was a significant corticosteroid refractoriness and responsiveness.

Binding and Enhanced Binding between Key Immunity Proteins TRAF6 and TIFA

Human tumor necrosis factor receptor associated factor (TRAF)-interacting protein, with a forkhead-associated domain (TIFA), is a key regulator of NF-κB activation. It also plays a key role in the activation of innate immunity in response to bacterial infection, through heptose 1,7-bisphosphate (HBP); a metabolite of lipopolysaccharide (LPS). However, the mechanism of TIFA function is largely unexplored, except for the suggestion of interaction with TRAF6. Herein, we provide evidence for direct binding, albeit weak, between TIFA and the TRAF domain of TRAF6, and it is shown that the binding is enhanced for a rationally designed double mutant, TIFA S174Q/M179D. Enhanced binding was also demonstrated for endogenous full-length TRAF6. Furthermore, the structures of the TRAF domain complexes with the consensus TRAF-binding peptides from the C terminus of wild-type and S174Q/M179D mutant TIFA, showing salt-bridge formation between residues 177-181 of TIFA and the binding pocket residues of the TRAF domain, were solved. Taken together, the results provide direct evidence and a structural basis for the TIFA-TRAF6 interaction, and show how this important biological function can be modulated.

Cross Talk Networks of Mammalian Target of Rapamycin Signaling With the Ubiquitin Proteasome System and Their Clinical Implications in Multiple Myeloma

Multiple myeloma (MM) is the second most common hematological malignancy and results from the clonal amplification of plasma cells. Despite recent advances in treatment, MM remains incurable with a median survival time of only 5-6years, thus necessitating further insights into MM biology and exploitation of novel therapeutic approaches. Both the ubiquitin proteasome system (UPS) and the PI3K/Akt/mTOR signaling pathways have been implicated in the pathogenesis, and treatment of MM and different lines of evidence suggest a close cross talk between these central cell-regulatory signaling networks. In this review, we outline the interplay between the UPS and mTOR pathways and discuss their implications for the pathophysiology and therapy of MM.

Calycosin inhibits nasopharyngeal carcinoma cells by influencing EWSAT1 expression to regulate the TRAF6-related pathways

The incidence of nasopharyngeal carcinoma (NPC) in China is relatively higher than that throughout the rest of the world, and NPC is geographically distributed. Long non-coding RNA (lncRNA) plays a key role in the development of tumors. Recent studies have found that the lncRNA Ewing sarcoma-associated transcript 1 (EWSAT1) is highly expressed in various tumors and also in NPCs. The isoflavone calycosin, which is a typical Chinese herbal medicine, can inhibit the growth of breast cancer, colorectal cancer, osteosarcoma and other cancers. The aim of our study was to select NPCs that were sensitive to calycosin and whether calycosin had an effect on NPC cells. If it does, are the effects related to a high expression of EWSAT1? We also verified that EWSAT1 was highly expressed in NPC cells. At the same time, we found that calycosin inhibited the growth of NPC cell lines. To further determine whether the effect of calycosin on NPC cells was related to EWSAT1, we used NPC cells with different concentrations of calycosin and found that the expression of EWSAT1 decreased significantly with increasing concentrations of calycosin and that the expression of downstream factors and pathways were also affected. It was demonstrated that calycosin affected NPC cell growth by regulating EWSAT1 and its downstream pathway. In addition, we overexpressed EWSAT1 and found that the increased expression of EWSAT1 weakened the growth inhibitory effect of calycosin on NPC cells.

STX2 promotes colorectal cancer metastasis through a positive feedback loop that activates the NF-κB pathway

Metastatic progression is the main contributor to the poor prognosis of colorectal cancer (CRC). Thus, identifying the determinants of CRC metastasis will be of great significance. Based on our previous bioinformatics analysis, Syntaxin2 (STX2) may be upregulated and correlated with the poor prognosis of CRC patients. In this study, we found that STX2 expression was associated with CRC invasion and metastasis and poor patient survival. Gain- and loss-of-function analyses demonstrated that STX2 functioned as a key oncogene by promoting CRC invasion and metastasis. Mechanistically, STX2 selectively interacted with tumor necrosis factor receptor-associated factor 6 (TRAF6) and activated the nuclear transcription factor-κB (NF-κB) signaling pathway. Furthermore, chromatin immunoprecipitation (ChIP) analysis revealed that NF-κB directly bound to the STX2 promoter and drove STX2 transcription. Therefore, STX2 activated the NF-κB pathway, and in turn, NF-κB increased STX2 expression, forming a positive signaling loop that eventually promoted CRC metastasis. Collectively, our results reveal STX2 as a crucial modulator of the aggressive CRC phenotype and highlight STX2 as a potential prognostic biomarker and therapeutic target for combating CRC metastasis.

Hepatic leukocyte immunoglobulin-like receptor B4 (LILRB4) attenuates nonalcoholic fatty liver disease via SHP1-TRAF6 pathway

Nonalcoholic fatty liver disease (NAFLD) is an increasingly prevalent liver pathology characterized by hepatic steatosis and commonly accompanied by systematic inflammation and metabolic disorder. Despite an accumulating number of studies, no pharmacological strategy is available to treat this condition in the clinic. In this study, we applied extensive gain- and loss-of-function approaches to identify the key immune factor leukocyte immunoglobulin-like receptor B4 (LILRB4) as a negative regulator of NAFLD. The hepatocyte-specific knockout of LILRB4 (LILRB4-HKO) exacerbated high-fat diet-induced insulin resistance, glucose metabolic imbalance, hepatic lipid accumulation, and systematic inflammation in mice, whereas LILRB4 overexpression in hepatocytes showed a completely opposite phenotype relative to that of LILRB4-HKO mice when compared with their corresponding controls. Further investigations of molecular mechanisms demonstrated that LILRB4 recruits SHP1 to inhibit TRAF6 ubiquitination and subsequent inactivation of nuclear factor kappa B and mitogen-activated protein kinase cascades. From a therapeutic perspective, the overexpression of LILRB4 in a genetic model of NAFLD, ob/ob mice, largely reversed the inherent hepatic steatosis, inflammation, and metabolic disorder.

CONCLUSION

Targeting hepatic LILRB4 to improve its expression or activation represents a promising strategy for the treatment of NAFLD as well as related liver and metabolic diseases. (Hepatology 2018;67:1303-1319).

Regulation of platelet activation and thrombus formation by reactive oxygen species

Reactive oxygen species (ROS) are generated within activated platelets and play an important role in regulating platelet responses to collagen and collagen-mediated thrombus formation. As a major collagen receptor, platelet-specific glycoprotein (GP)VI is a member of the immunoglobulin (Ig) superfamily, with two extracellular Ig domains, a mucin domain, a transmembrane domain and a cytoplasmic tail. GPVI forms a functional complex with the Fc receptor γ-chain (FcRγ) that, following receptor dimerization, signals via an intracellular immunoreceptor tyrosine-based activation motif (ITAM), leading to rapid activation of Src family kinase signaling pathways. Our previous studies demonstrated that an unpaired thiol in the cytoplasmic tail of GPVI undergoes rapid oxidation to form GPVI homodimers in response to ligand binding, indicating an oxidative submembranous environment in platelets after GPVI stimulation. Using a redox-sensitive fluorescent dye (H2DCF-DA) in a flow cytometric assay to measure changes in intracellular ROS, we showed generation of ROS downstream of GPVI consists of two distinct phases: an initial Syk-independent burst followed by additional Syk-dependent generation. In this review, we will discuss recent findings on the regulation of platelet function by ROS, focusing on GPVI-dependent platelet activation and thrombus formation.

Autoregulation of RANK ligand in oral squamous cell carcinoma tumor cells

Oral squamous cell carcinoma (OSCC) is the most common malignancy among oral cancers and shows potent activity for local bone invasion. Receptor activator of nuclear factor κB (RANK) ligand (RANKL) is critical for bone-resorbing osteoclast formation. We previously demonstrated that OSCC tumor cells express high levels of RANKL. In this study, confocal microscopy demonstrated RANKL specific receptor, RANK expression in OSCC tumor cell lines (SCC1, SCC12, and SCC14a). We also confirmed the expression of RANK and RANKL in primary human OSCC tumor specimens. However, regulatory mechanisms of RANKL expression and a functional role in OSCC tumor progression are unclear. Interestingly, we identified that RANKL expression is autoregulated in OSCC tumor cells. The RANKL specific inhibitor osteoprotegerin (OPG) treatment to OSCC cells inhibits autoregulation of RANKL expression. Further, we showed conditioned media from RANKL CRISPR-Cas9 knockout OSCC cells significantly decreased osteoclast formation and bone resorption activity. In addition, RANKL increases OSCC tumor cell proliferation. RANKL treatment to OSCC cells demonstrated a dose-dependent increase in RANK intracellular adaptor protein, TRAF6 expression, and activation of IKK and IκB signaling molecules. We further identified that transcription factor NFATc2 mediates autoregulation of RANKL expression in OSCC cells. Thus, our results implicate RANKL autoregulation as a novel mechanism that facilitates OSCC tumor cell growth and osteoclast differentiation/bone destruction.

The effects of TRAF6 on proliferation, apoptosis and invasion in osteosarcoma are regulated by miR-124

The present study aimed to verify tumor necrosis factor receptor‑associated factor 6 (TRAF6) as the target gene of microRNA-124 (miR-124). In addition, the expression of miR‑124 was investigated in osteosarcoma tissues and cells, and its effects on the biological characteristics of osteosarcoma cells were determined, in order to provide an experimental and theoretical basis for the application of TRAF6 in the treatment of osteosarcoma. A fluorescence reporter enzyme system was used to verify TRAF6 as a target gene of miR‑124, and western blotting was used to detect the effects of miR‑124 on the protein expression levels of TRAF6 in cells. The expression levels of miR‑124 were detected in osteosarcoma tissues and an osteosarcoma cell line (MG‑63) by quantitative polymerase chain reaction (qPCR). In addition, a total of 48 h post‑transfection of MG‑63 cells with a miR‑124 mimic, qPCR was used to detect the expression levels of miR‑124, and the effects of miR‑124 on the viability of MG‑63 human osteosarcoma cells was determined using the MTT method. The effects of miR‑124 on the cell cycle progression and apoptosis of MG‑63 cells were analyzed by flow cytometry, whereas the effects of miR‑124 on the migration of MG‑63 cells was detected using the Transwell invasion chamber analysis method. A TRAF6 recombinant expression plasmid (pcDNA3.1‑TRAF6) was also constructed, and MG‑63 cells were transfected with the recombinant plasmid and a miR‑124 mimic, in order to further validate the biological role of miR‑124 via the regulation of TRAF6. The results of the present study indicated that, compared with in the normal control group, the expression levels of miR‑124 were significantly increased in MG‑63 cells transfected with a miR‑124 mimic (P<0.01). In addition, the luciferase reporter gene system demonstrated that, compared with in the control group, relative luciferase activity was significantly reduced in the miR‑124 mimic group (P<0.01). The results of MTT analysis indicated that cell viability was also significantly reduced in response to the overexpression of miR‑124 in MG‑63 cells (P<0.01). Flow cytometric analysis demonstrated that the proportion of cells in S phase and G2/M phase was significantly decreased (P<0.01) in cells overexpressing miR‑124, and the number of apoptotic cells was significantly increased (P<0.01). Furthermore, the results of the Transwell invasion assay suggested that the number of invasive cells was significantly decreased following enhanced expression of miR‑124 (P<0.01). In MG‑63 cells overexpressing miR‑124 and TRAF6, the results of MTT, flow cytometric and Transwell assay analyses demonstrated that the overexpression of TRAF6 had the opposite biological effects compared to miR‑124 overexpression. In conclusion, the present study indicated that the expression levels of miR‑124 were downregulated in human osteosarcoma tissues and cells, and that miR‑124 is associated with negative regulation of TRAF6 expression; therefore, the role of TRAF6 in primary osteosarcoma may be regulated by miR‑124. Therapeutic strategies that enhance miR‑124 expression or inhibit TRAF6 expression may be beneficial for the treatment of patients with osteosarcoma.

Mechanisms of Resistance in Multiple Myeloma

Multiple myeloma (MM) is an incurable hematopoietic cancer that is characterized by malignant plasma cell infiltration of the bone marrow and/or extramedullary sites. Multi-modality approaches including "novel agents," traditional chemotherapy, and/or stem cell transplantation are used in MM therapy. Drug resistance, however, ultimately develops and the disease remains incurable for the vast majority of patients. In this chapter, we review both tumor cell-autonomous and non-autonomous (microenvironment-dependent) mechanisms of drug resistance. MM provides an attractive paradigm highlighting a number of current concepts and challenges in oncology. Firstly, identification of MM cancer stem cells and their unique drug resistance attributes may provide rational avenues towards MM eradication and cure. Secondly, the oligoclonal evolution of MM and alternation of "clonal tides" upon therapy challenge our current understanding of treatment responses. Thirdly, the success of MM "novel agents" provides exemplary evidence for the impact of therapies that target the immune and non-immune microenvironment. Fourthly, the rapid pace of drug approvals for MM creates an impetus for development of precision medicine strategies and biomarkers that promote efficacy and mitigate toxicity and cost. While routine cure of the disease remains the ultimate and yet unattainable prize, MM advances in the last 10-15 years have provided an astounding paradigm for the treatment of blood cancers in the modern era and have radically transformed patient outcomes.

Hepatoprotective effect of quercetin via TRAF6/JNK pathway in acute hepatitis

Quercetin, as a member of the flavonoids family, has many beneficial properties. The aim of our study was to evaluate the protective effect of quercetin in ConA-induced hepatitis in mice, and to clarify its mechanism of action. Hepatitis was induced by using ConA (25 mg/kg), and quercetin was administered intragastrically at the dose of 100 mg/kg or 200 mg/kg for 5 days before ConA injection. The serum levels of liver enzymes, inflammatory cytokines and other marker proteins were determined at 2 h, 8 h and 24 h after ConA injection. Following ConA injection, serum levels of liver enzymes and inflammatory cytokines were significantly increased. Quercetin ameliorated liver damage and histopathological changes, and suppressed the release of inflammatory cytokines. The expression of Bax, Bcl-2, Beclin-1, LC3, P62 and caspase 9 were markedly affected by quercetin pretreatment. The expression of TRAF6 and p-JNK were decreased in the quercetin groups. Quercetin attenuated apoptosis and autophagy in ConA-induced autoimmune hepatitis by inhibiting TRAF6/JNK pathway.

I‑BET151 inhibits osteoclastogenesis via the RANKL signaling pathway in RAW264.7 macrophages

Excessive bone resorption mediated by osteoclasts may lead to the risk of various lytic bone diseases. In the present study, the effects of I‑BET151, a bromodomain and extra terminal domain protein inhibitor, on osteoclastogenesis in RAW264.7 cells and the underlying mechanism of this process was investigated. Cells were divided into 6 groups, including the control group, receptor activator of nuclear factor‑κB ligand (RANKL) group and 4 other groups containing RANKL and I‑BET151 at different concentrations. Tartrate‑resistant acid phosphatase (TRACP) staining was used to observe the effect of I‑BET151 on osteoclastogenesis and the number of TRACP positive multinucleated cells was calculated. Western blotting was used to evaluate the expression of tumor necrosis factor receptor associated factor (TRAF6), nuclear factor of activated T‑cells cytoplasmic 1 (NFATcl), transcription factor p65 (p65), nuclear factor of κ light polypeptide gene enhancer in B‑cells inhibitor‑α (IκB‑α), extracellular signal‑regulated kinase, Jun N‑terminal kinase (JNK) and p38. mRNA expression levels of osteoclast specific genes TRACP, matrix metalloproteinase‑9 (MMP9), cathepsin K (CtsK) and proto‑oncogene tyrosine‑protein kinase Src (c‑Src) were measured using the reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). TRACP staining results demonstrated that I‑BET151 inhibited osteoclastogenesis induced by RANKL and the inhibition was dose dependent. TRACP multinucleated positive cells were significantly decreased when treated with I‑BET151 compared with the RANKL group. The inhibitory effect on TRAF6 was significant when concentrations of 100 and 200 nM I‑BET151 were used, and NFATcl was significantly inhibited when a concentration of 200 nM was used compared with the RANKL group, in a dose-dependent manner. Nuclear translocation of p65 was significantly inhibited by I‑BET151 at all concentrations. The degradation of IκB‑α, and phosphorylation of JNK and p38 were also significantly inhibited by I‑BET151, with the exception of the expression of IκB‑α following treatment with 50 nM I‑BET151. The RT‑qPCR results revealed that osteoclast‑specific genes TRACP, MMP9, CtsK and c‑Src were all dose‑dependently inhibited by I‑BET151, except for CtsK. In conclusion, I‑BET151 may significantly suppress the osteoclastogenesis of RAW264.7 cells via the RANKL signaling pathway.

The effect of marrow stromal cells on TRAF6 expression levels in myeloma cells

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an important E3 ubiquitin ligase, which is key to immunity. TRAF6 has been implicated in the invasive growth and metastasis of various types of cancer, including squamous cell carcinoma, gastric cancer, myelodysplastic syndromes and acute myeloid leukemia. In the present study, associations between multiple myeloma (MM) and TRAF6, its downstream component nuclear factor-κB (NF-κB) and bone marrow stromal cells (MSC) were investigated. The TRAF6 protein expression levels of 18 patients were positively correlated with the protein levels of β-2 microglobulin (r²=0.3472; P=0.01) and negatively correlated with albumin protein levels (r²=0.5494; P=0.0004). In vitro expression of the TRAF6 protein, phosphorylated transcription factor p65 and phosphorylated p100 in myeloma cell lines was induced by MSCs from patients with MM. In addition, the in vitro expression of TRAF6 was associated with an enhanced proliferation rate of myeloma cells, which was blocked by silencing TRAF6 using small interfering RNA. Due to the association between the TRAF6-NF-κB signaling pathway in myeloma cells and MSCs, this signaling pathway may be a useful prognostic and therapeutic target in myeloma.

N6-Isopentenyladenosine promoted HeLa cell apoptosis through inhibitions of AKT and transforming growth factor β-activated kinase 1 activation

N6-Isopentenyladenosine, a member of the family of plant hormones, possesses anti-cancer activities on a number of cancer cell lines. However, its mode of action in cervical cancer cell remains poorly understood. Our computational docking studies showed that N6-Isopentenyladenosine could bind with the really interesting new gene domain of tumor necrosis factor receptor-associated factor 6, which is an ubiquitination E3 ligase. Tumor necrosis factor receptor-associated factor 6-mediated ubiquitination is known to activate both protein kinase B (also known as AKT) and transforming growth factor β-activated kinase 1, and the really interesting new gene domain comprises the core of the ubiquitin ligase catalytic domain. First, we evaluated the effects of iPA on cervical cancer cell line HeLa using MTT and flow cytometry. Second, we examined the effects of iPA on activation of tumor necrosis factor receptor-associated factor 6-mediated downstream targets using western blot or immunoprecipitation. iPA could reduce HeLa cell proliferation through apoptosis, and such anti-cancer activity is associated with inhibitions of both AKT and transforming growth factor β-activated kinase 1 signaling pathways. In addition, suppression of the anti-apoptotic protein Bcl-2 and elevation of the pro-apoptotic protein Bax were also observed. Anti-proliferation properties of iPA are likely due to its binding at the really interesting new gene domain of tumor necrosis factor receptor-associated factor 6 and loss of AKT and transforming growth factor β-activated kinase 1 activities as a result of functional modulations of tumor necrosis factor receptor-associated factor 6. These results support the emerging notion that tumor necrosis factor receptor-associated factor 6 could serve as a viable target for developing new cancer therapeutics.

Cinchonine induces apoptosis of HeLa and A549 cells through targeting TRAF6

BACKGROUND

Cancer cells are known to over-express TRAF6 that is critical for both AKT and TAK1 activations. The Really Interesting New Gene (RING) domain of TRAF6 is believed to be responsible for the E3 ligase activity, ZINC fingers of TRAF6 provide critical support for the activity of the RING domain which is critical for both AKT and TAK1 activations.

METHODS

We employed computational docking program to identify small molecules that could effectively and competitively bind with the RING domain of TRAF6, which is believed to be responsible for its E3 ligase activity. MTT assay and flow cytometry were employed to analyze apoptosis of cancer cells. Signaling pathways were detected using immunoprecipitation and western blotting, and immunofluorescence was pursued to assess the nature of binding of cinchonine to TRAF6. We also performed animal experiments to test effect of cinchonine in vivo.

RESULTS

Cinchonine, a naturally occurring Cinchona alkaloid identified from the docking study, could bind to TRAF6 in HeLa and A549 cells and induce apoptosis of these cancer cells. We found that AKT ubiquitination and phosphorylation as well as phosphorylation of TAK1 were decreased. These activities would lead to subsequent suppression anti-apoptotic protein Bcl-2, while elevating pro-apoptotic protein Bax. Immunofluorescence staining unambiguously demonstrated the binding of cinchonine specifically at the RING domain of TRAF6 in cells, thereby validating the computational modeling. Animal experiments showed that cinchonine could suppress tumor growth in mice without showing significant acute toxicity.

CONCLUSION

These investigations suggest that through competitive binding with the RING domain of TRAF6, cinchonine could induce apoptosis via inhibiting AKT and TAK1 signaling pathways.

Cell Adhesion Molecule CD166 Drives Malignant Progression and Osteolytic Disease in Multiple Myeloma

Multiple myeloma is incurable once osteolytic lesions have seeded at skeletal sites, but factors mediating this deadly pathogenic advance remain poorly understood. Here, we report evidence of a major role for the cell adhesion molecule CD166, which we discovered to be highly expressed in multiple myeloma cell lines and primary bone marrow cells from patients. CD166⁺ multiple myeloma cells homed more efficiently than CD166^- cells to the bone marrow of engrafted immunodeficient NSG mice. CD166 silencing in multiple myeloma cells enabled longer survival, a smaller tumor burden, and less osteolytic lesions, as compared with mice bearing control cells. CD166 deficiency in multiple myeloma cell lines or CD138⁺ bone marrow cells from multiple myeloma patients compromised their ability to induce bone resorption in an ex vivo organ culture system. Furthermore, CD166 deficiency in multiple myeloma cells also reduced the formation of osteolytic disease in vivo after intratibial engraftment. Mechanistic investigation revealed that CD166 expression in multiple myeloma cells inhibited osteoblastogenesis of bone marrow-derived osteoblast progenitors by suppressing Runx2 gene expression. Conversely, CD166 expression in multiple myeloma cells promoted osteoclastogenesis by activating TRAF6-dependent signaling pathways in osteoclast progenitors. Overall, our results define CD166 as a pivotal director in multiple myeloma cell homing to the bone marrow and multiple myeloma progression, rationalizing its further study as a candidate therapeutic target for multiple myeloma treatment. Cancer Res; 76(23); 6901-10. ©2016 AACR.

ON 01910.Na inhibits growth of diffuse large B-cell lymphoma by cytoplasmic sequestration of sumoylated C-MYB/TRAF6 complex

Diffuse large B-cell lymphoma (DLBCL), the most common lymphoma, shows either no response or development of resistance to further treatment in 30% of the patients that warrants the development of novel drugs. We have reported that ON 01910.Na (rigosertib), a multikinase inhibitor, is selectively cytotoxic for DLBCL and induces more hyperphosphorylation and sumoylation of Ran GTPase-activating protein 1 (RanGAP1) in DLBCL cells than in non-neoplastic lymphoblastoid cell line. However, the exact mechanism of rigosertib-induced cell death in DLBCL remains to be clarified. Here, we analyzed the efficacy of rigosertib against DLBCL cells in vitro and in vivo and its molecular effects on tumor biology. We found for the first time that rigosertib attenuated expression of unmodified and sumoylated tumor necrosis factor receptor-associated factor 6 (TRAF6) and c-Myb and inhibited nuclear entry of sumoylated RanGAP1, TRAF6, and c-Myb that was confirmed by immunofluorescence. Moreover, co-immunoprecipitation showed that rigosertib induced sequestration of c-Myb and TRAF6 in the cytoplasm by stimulating their sumoylation through the RanGAP1*SUMO1/Ubc9 pathway. Specific knockdown of c-Myb and TRAF6 induced tumor cell apoptosis and cell cycle arrest at G1 phase. Xenograft mice bearing lymphoma cells also exhibited effective tumor regression on rigosertib treatment along with cytoplasmic expression of c-Myb and TRAF6. Nuclear expression of c-Myb in clinical cases of DLBCL correlated with a poor prognosis. Thus, suppression of c-Myb and TRAF6 activity may have therapeutic implication in DLBCL. These data support the clinical development of rigosertib in DLBCL.

Pancreatic Acinar Cells Employ miRNAs as Mediators of Intercellular Communication to Participate in the Regulation of Pancreatitis-Associated Macrophage Activation

Macrophage activation plays an important role in the inflammatory response in acute pancreatitis. In the present study, the activation of AR42J pancreatic acinar cells was induced by taurolithocholate treatment. The results showed that the culture medium from the activated AR42J cells significantly enhanced NFκB activation in the macrophages compared to that without taurolithocholate treatment. Additionally, the precipitates obtained from ultracentrifugation of the culture media that were rich in exosomes were markedly more potent in activating macrophages compared with the supernatant fraction lacking exosomes. The results indicated that the mediators carried by the exosomes played important roles in macrophage activation. Exosomal miRNAs were extracted and examined using microarrays. A total of 115 differentially expressed miRNAs were identified, and 30 showed upregulated expression, while 85 displayed downregulated expression. Target genes of the differentially expressed miRNAs were predicted using TargetScan, MiRanda, and PicTar software programs. The putative target genes were subjected to KEGG functional analysis. The functions of the target genes were primarily enriched in MAPK pathways. Specifically, the target genes regulated macrophage activation through the TRAF6-TAB2-TAK1-NIK/IKK-NFκB pathway. As the mediators of signal transduction, miRNAs and their predicted target mRNAs regulate every step in the MAPK pathway.

Tumor necrosis factor receptor- associated factor 6 (TRAF6) regulation of development, function, and homeostasis of the immune system

Tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) is an adapter protein that mediates a wide array of protein-protein interactions via its TRAF domain and a RING finger domain that possesses non-conventional E3 ubiquitin ligase activity. First identified nearly two decades ago as a mediator of interleukin-1 receptor (IL-1R)-mediated activation of NFκB, TRAF6 has since been identified as an actor downstream of multiple receptor families with immunoregulatory functions, including members of the TNFR superfamily, the Toll-like receptor (TLR) family, tumor growth factor-β receptors (TGFβR), and T-cell receptor (TCR). In addition to NFκB, TRAF6 may also direct activation of mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K), and interferon regulatory factor pathways. In the context of the immune system, TRAF6-mediated signals have proven critical for the development, homeostasis, and/or activation of B cells, T cells, and myeloid cells, including macrophages, dendritic cells, and osteoclasts, as well as for organogenesis of thymic and secondary lymphoid tissues. In multiple cellular contexts, TRAF6 function is essential not only for proper activation of the immune system but also for maintaining immune tolerance, and more recent work has begun to identify mechanisms of contextual specificity for TRAF6, involving both regulatory protein interactions, and messenger RNA regulation by microRNAs.

Expression and Clinical Significance of Tumor Necrosis Factor Receptor-Associated Factor 6 in Patients With Colon Cancer

BACKGROUND

Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been reported to be highly expressed in many tumor tissues, but it is still of value to detect its expression in patients with colon cancer and to clarify its clinical significance.

OBJECTIVES

To study the expression and clinical significance of TRAF6 in patients with colon cancer.

PATIENTS AND METHODS

A total of 135 patients with colon cancer who underwent surgery at our hospital from February 2008 to March 2013 were selected. The expression levels of TRAF6 protein in tumor and paracancerous tissues were detected with the immunohistochemical method to evaluate their clinical significance.

RESULTS

The positive expression rate of TRAF6 in tumor tissues was 66.7%, which was significantly higher than in normal paracancerous tissues (18.5%). The positive expression rate of TRAF6 was significantly correlated with Dukes' staging, degree of differentiation, and lymphatic metastasis (P < 0.05), but not gender or age (P > 0.05). The expression level of TRAF6 was negatively correlated with the 5-year survival rate; patients with high TRAF6 expression levels had significantly decreased survival compared to those with low levels (P < 0.05).

CONCLUSIONS

TRAF6 plays an important role in the onset of colon cancer; therefore, drugs targeting it may have great clinical significance in the treatment of this disease.

TRAF6 promotes the invasion and metastasis and predicts a poor prognosis in gastric cancer

PURPOSE

This study investigated the relationships of TRAF6 expression with clinical pathologic parameters and the prognosis of patients with gastric cancer. This study also explored the roles of TRAF6 in cell apoptosis and invasiveness, as well as underlying molecular mechanism of gastric cancer cell line in vitro.

METHODS

A total of 90 cases of tissue microarrays were immunohistochemically analyzed for TRAF6 expression. Cell proliferation was measured by MTT assay. Flow cytometry was used for analyzing cell apoptosis and cell invasion ability was detected by a Transwell invasion assay. Protein expression was assessed by Western blotting.

RESULTS

TRAF6 was expressed in 53 of 90 (58.9%) cases of gastric cancer. TRAF6 expression was significantly positively correlated with advanced N stage, pathological stage and a poor prognosis, but not an independent predictor of a poor prognosis in gastric cancer (p=0.083). The knockdown of TRAF6 increased cell apoptosis and reduced invasive ability of BGC-823 cell. Moreover, TRAF6 down-regulation decreased protein levels of phosphor-Akt, Bcl-2 and MMP9 and up-regulation of Bax in BGC-823 cell. Inversely, overexpression of TRAF6 in SGC-7901 cells increased protein levels of phosphor-Akt, Bcl-2 and MMP9 and down-regulation of Bax.

CONCLUSIONS

The expression of TRAF6 was positively correlated with an advanced N stage and acted as a predictor of a poor prognosis in patients with gastric cancer. Moreover, TRAF6 regulating cell apoptosis and invasive ability of gastric cancer cells might be associated with Akt activation and alterations of protein expression of Bcl2, Bax and MMP9.

A functional polymorphism in the pre‑miR‑146a gene influences the prognosis of glioblastoma multiforme by interfering with the balance between Notch1 and Notch2

The aim of the present study was to evaluate the association between a polymorphism (rs2910164) in the microRNA (miR)‑146a precursor and the prognosis of glioblastoma multiforme (GBM), as well as to examine the possible underlying mechanism in a Chinese population. A total of 380 patients with histologically confirmed GBM were recruited between 2008 and 2012, and were genotyped for the rs2910164 polymorphism using Sanger sequencing. The Kaplan‑Meier method was used to estimate overall survival (OS), and univariate and multivariate Cox proportional hazard regression analyses were used to evaluate the effect of miR‑146a polymorphisms on OS. It was identified that the rs2910164 CC genotype was significantly associated with a decreased OS among the patients with GBM (P=0.002). It was confirmed that Notch1 and Notch2 were targets of miR‑146a and it was demonstrated that the introduction of miR‑146a mimic suppressed the levels of Notch1 and Notch2 to different extents, resulting in a reduced Notch1/Notch2 ratio with an increase in miR‑146a mimic concentration in U251 cells. Additionally, resected tumor specimens were collected from 138 GBM patients and the expression levels of miR‑146a, Notch1 and Notch2 were examined using reverse transcription‑quantitative polymerase chain reaction and western blot analysis. Consistent with the in vitro study, lower levels of miR‑146a, higher levels of Notch1 and Notch2, and a higher Notch1/Notch2 ratio were identified in the CC genotype group compared with those of the GG/GC group. In the present study, the rs2910164 C allele was found to be associated with a reduced survival rate in patients with GBM, and the observed association between the CC genotype and poorer prognosis of GBM was at least partially mediated by the decreased expression of miR‑146a, which interfered with the balance of Notch1 and Notch2.

Increased serum tumor necrosis factor receptor-associated factor-6 expression in patients with non-metastatic triple-negative breast cancer

Obesity appears to be associated with an increased risk of breast cancer (BC) and an inferior oncological outcome at the time of diagnosis, with poor outcomes most prominent in cases of triple-negative BC (TNBC). The present study analyzed serum tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and TNF receptor associated factor-6 (TRAF) protein expression levels in 48 patients with non-metastatic BC and 26 obese control patients (without BC). The mean age of the cohort was 52.5 years (range, 35-78 years) and the patients had a median body mass index of 33.5 kg/m² (range, 30-47 kg/m²). In the study population, 27.1% of BC patients were triple negative and 70.8% were hormone receptor (HR)-positive. Median serum TRAF6 expression was 0.90 ng/ml (range, 0.55-1.53 ng/ml) in the 13 TNBC patients and 0.63 ng/ml (range, 0.49-1.22 ng/ml) in the 35 HR-positive BC patients; thus, TRAF6 expression was significantly higher in the TNBC patients compared with the obese control group (0.90 vs. 0.73 ng/ml; P=0.033). Furthermore, median serum TRAF6 expression levels were significantly higher in HR-negative patients compared with HR-positive patients (0.83 vs. 0.62 ng/ml; P=0.002). The present study demonstrated that serum TRAF6 expression levels were increased in TNBC and HR-negative patients with non-metastatic BC compared with HR- and human epidermal growth factor receptor 2-positive cases or the obese healthy control group. Therefore, elevated TRAF6 expression may be a poor prognostic factor in non-metastatic BC. In addition, we propose that progesterone (PR) negativity may be a more useful poor prognosis factor than estrogen receptor (ER) negativity, as TRAF6 expression levels were higher in the PR-negative patients compared with the ER-negative patients.

Inhibition of IRAK1/4 sensitizes T cell acute lymphoblastic leukemia to chemotherapies

Signaling via the MyD88/IRAK pathway in T cells is indispensable for cell survival; however, it is not known whether this pathway functions in the progression of T acute lymphoblastic leukemia (T-ALL). Here, we determined that compared with thymic and peripheral T cells, T-ALL cells from patients have elevated levels of IRAK1 and IRAK4 mRNA as well as increased total and phosphorylated protein. Targeted inhibition of IRAK1 and IRAK4, either with shRNA or with a pharmacological IRAK1/4 inhibitor, dramatically impeded proliferation of T-ALL cells isolated from patients and T-ALL cells in a murine leukemia model; however, IRAK1/4 inhibition had little effect on cell death. We screened several hundred FDA-approved compounds and identified a set of drugs that had enhanced cytotoxic activity when combined with IRAK inhibition. Administration of an IRAK1/4 inhibitor or IRAK knockdown in combination with either ABT-737 or vincristine markedly reduced leukemia burden in mice and prolonged survival. IRAK1/4 signaling activated the E3 ubiquitin ligase TRAF6, increasing K63-linked ubiquitination and enhancing stability of the antiapoptotic protein MCL1; therefore, IRAK inhibition reduced MCL1 stability and sensitized T-ALL to combination therapy. These studies demonstrate that IRAK1/4 signaling promotes T-ALL progression through stabilization of MCL1 and suggest that impeding this pathway has potential as a therapeutic strategy to enhance chemotherapeutic efficacy.

Ablation of Akt2 protects against lipopolysaccharide-induced cardiac dysfunction: role of Akt ubiquitination E3 ligase TRAF6

Lipopolysaccharide (LPS), an essential component of the outer membrane of Gram-negative bacteria, plays a pivotal role in myocardial anomalies in sepsis. Recent evidence has depicted a role of Akt in LPS-induced cardiac sequelae although little information is available with regard to the contribution of Akt isoforms in the endotoxin-induced cardiac dysfunction. This study examined the effect of Akt2 knockout on LPS-induced myocardial contractile dysfunction and the underlying mechanism(s) with a focus on TNF receptor-associated factor 6 (TRAF6). Echocardiographic properties and cardiomyocyte contractile function [peak shortening (PS), maximal velocity of shortening/relengthening, time-to-PS, time-to-90% relengthening] were examined in wild-type and Akt2 knockout mice following LPS challenge (4mg/kg, 4h). LPS challenge enlarged LV end systolic diameter, reduced fractional shortening and cardiomyocyte contractile capacity, prolonged TR90, promoted apoptosis, upregulated caspase-3/-12, ubiquitin, and the ubiquitination E3 ligase TRAF6 as well as decreased mitochondrial membrane potential without affecting the levels of TNF-α, toll-like receptor 4 and the mitochondrial protein ALDH2. Although Akt2 knockout failed to affect myocardial function, apoptosis, and ubiquitination, it significantly attenuated or mitigated LPS-induced changes in cardiac contractile and mitochondrial function, apoptosis and ubiquitination but not TRAF6. LPS facilitated ubiquitination, phosphorylation of Akt, GSK3β and p38, the effect of which with the exception of p38 was ablated by Akt2 knockout. TRAF6 inhibitory peptide or RNA silencing significantly attenuated LPS-induced Akt2 ubiquitination, cardiac contractile anomalies and apoptosis. These data collectively suggested that TRAF6 may play a pivotal role in mediating LPS-induced cardiac injury via Akt2 ubiquitination.

The genetic architecture of multiple myeloma

Multiple myeloma is a malignant proliferation of monoclonal plasma cells leading to clinical features that include hypercalcaemia, renal dysfunction, anaemia, and bone disease (frequently referred to by the acronym CRAB) which represent evidence of end organ failure. Recent evidence has revealed myeloma to be a highly heterogeneous disease composed of multiple molecularly-defined subtypes each with varying clinicopathological features and disease outcomes. The major division within myeloma is between hyperdiploid and nonhyperdiploid subtypes. In this division, hyperdiploid myeloma is characterised by trisomies of certain odd numbered chromosomes, namely, 3, 5, 7, 9, 11, 15, 19, and 21 whereas nonhyperdiploid myeloma is characterised by translocations of the immunoglobulin heavy chain alleles at chromosome 14q32 with various partner chromosomes, the most important of which being 4, 6, 11, 16, and 20. Hyperdiploid and nonhyperdiploid changes appear to represent early or even initiating mutagenic events that are subsequently followed by secondary aberrations including copy number abnormalities, additional translocations, mutations, and epigenetic modifications which lead to plasma cell immortalisation and disease progression. The following review provides a comprehensive coverage of the genetic and epigenetic events contributing to the initiation and progression of multiple myeloma and where possible these abnormalities have been linked to disease prognosis.

Peptides genetically selected for NF-κB activation cooperate with oncogene Ras and model carcinogenic role of inflammation

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.

Role of CYB5A in pancreatic cancer prognosis and autophagy modulation

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.

Effect of TRAF6 on the biological behavior of human lung adenocarcinoma cell

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a unique adaptor protein of the tumor necrosis factor receptor-associated factor family that mediates both tumor necrosis factor receptor and interleukin-1 receptor/Toll-like receptor signaling. A recent study showed that TRAF6 played an important role in tumorigenesis and invasion through activation of nuclear factor kappa B (NF-κB). However, the biological role of TRAF6 remains unknown in lung cancer up to now. To address the expression of TRAF6 in lung cancer cells, four lung cancer cell lines (A549, HCC827, NCI-H292, and 95-D) and human bronchial epithelial cells were used to detect the expression of TRAF6 protein by western blotting. Results indicated that TRAF6 displayed an upregulation in human lung cancer cell lines. To investigate the effects of TRAF6 on the biological behavior of human lung adenocarcinoma cell, we generated human lung adenocarcinoma A549 cell line in which TRAF6 was depleted. The results showed that downregulation of TRAF6 could decrease cell viability, suppress cell proliferation and invasion, and promote cell apoptosis. At the same time, we explored the effects of TRAF6 on the expression of the following proteins: phosphor-NF-κB (p-p65), cyclin D1, caspase-3, and matrix metalloproteinase 9 (MMP9). Downregulation of TRAF6 could decrease the expression of p-p65, cyclin D1, and MMP9 and increase the expression of caspase-3. All these results suggested that TRAF6 might be involved in the potentiation of growth, proliferation, and invasion of A549 cell line, as well as the inhibition of A549 cell apoptosis by the activation of NF-κB. To make a long story short, the overexpression of TRAF6 might be related to the tumorigenesis and invasion of lung cancer.

TRAF6 regulates proliferation, apoptosis, and invasion of osteosarcoma cell

TRAF6, a unique tumor necrosis factor receptor-associated factor (TRAF) family member, possesses a unique receptor-binding specificity that results in its crucial role as the signaling mediator for TNF receptor superfamily and interleukin-1 receptor/Toll-like receptor superfamily. TRAF6 plays an important role in tumorigenesis, invasion and metastasis. This study aimed to explore the expression of TRAF6 in osteosarcoma tissues and its correlation to the clinical pathology of osteosarcoma and to discuss the relationship between TRAF6 expression and osteosarcoma invasion. These data will provide the experimental base for the biological treatment of osteosarcoma in the future. Using RT-PCR and Western blot, the results showed that the expression rate of TRAF6 mRNA in osteosarcoma tissues was significantly higher than that in normal bone tissue (p < 0.05), that the expression rate of TRAF6 mRNA in the carcinoma tissues from patients with lung metastasis was significantly higher than that from patients without lung metastasis (p < 0.05), and that the expression rate of TRAF6 mRNA also increased with increasing Enneking stage (p < 0.05). However, the mRNA expression of TRAF6 in osteosarcoma was independent of the patient's gender, age, and tumor size (p > 0.05). The TRAF6 protein displayed an up-regulation in osteosarcoma tissues compared to normal bone tissue (p < 0.05), displayed an up-regulation in osteosarcoma tissues from patients with lung metastasis compared to from patients without lung metastasis (p < 0.05), and displayed a gradual increase with increasing Enneking stage (p < 0.05). By the technique of RNA interference, the expression of TRAF6 in the human osteosarcoma MG-63 cell line was down-regulated, and the invasive ability of MG-63 cells was examined. The results showed that TRAF6 protein expression was significantly decreased in the MG-63 cells from TRAF6 siRNA-transfected group (p < 0.05), and the proliferation ability of MG-63 cells and the number of MG-63 cells that passed through the Transwell chamber were significantly lower than that in the non-transfected control group as well as the transfected control group (p < 0.05). In addition, the percentage of MG-63 cells undergoing apoptosis was significantly higher in the TRAF6 siRNA-transfected group compared with the non-transfected control group as well as the transfected control group (p < 0.05). The expression of p-p65, cyclin D1, MMP-9 was down-regulated in the MG-63 cells from TRAF6 siRNA-transfected group. The expression of caspase 3 was up-regulated in the MG-63 cells from TRAF6 siRNA-transfected group compared to the non-transfected control group as well as the transfected control group (p < 0.05). To make a long story short, the overexpression of TRAF6 in osteosarcoma might be related to the tumorigenesis, invasion of osteosarcoma.