TRAF6 regulates proliferation, apoptosis, and invasion of osteosarcoma cell

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.

TRAF6 regulates autophagy and apoptosis of melanoma cells through c-Jun/ATG16L2 signaling pathway

Autophagy and apoptosis are essential processes that participate in cell death and maintain cellular homeostasis. Dysregulation of these biological processes results in the development of diseases, including cancers. Therefore, targeting the interaction between apoptosis and autophagy offers a potential strategy for cancer therapy. Melanoma is the most lethal skin cancer. We previously found that tumor necrosis factor receptor-associated factor 6 (TRAF6) is overexpressed in melanoma and benefits the malignant phenotype of melanoma cells. Additionally, TRAF6 promotes the activation of cancer-associated fibroblasts in melanoma. However, the role of TRAF6 in autophagy and apoptosis remains unclear. In this study, we found that knockdown of TRAF6 induced both apoptosis and autophagy in melanoma cells. Transcriptomic data and real-time PCR analysis demonstrated reduced expression of autophagy related 16 like 2 (ATG16L2) in TRAF6-deficient melanoma cells. ATG16L2 knockdown resulted in increased autophagy and apoptosis. Mechanism studies confirmed that TRAF6 regulated ATG16L2 expression through c-Jun. Importantly, targeting TRAF6 with cinchonine, a TRAF6 inhibitor, effectively suppressed the growth of melanoma cells by inducing autophagy and apoptosis through the TRAF6/c-Jun/ATG16L2 signaling pathway. These findings highlight the pivotal role of TRAF6 in regulating autophagy and apoptosis in melanoma, emphasizing its significance as a novel therapeutic target for melanoma treatment.

Asiaticoside reverses M2 phenotype macrophage polarization-evoked osteosarcoma cell malignant behaviour by TRAF6/NF-κB inhibition

CONTEXT

M2 phenotype macrophage polarization is an attractive target for therapeutic intervention. Asiaticoside (ATS) has multiple pharmacological functions.

OBJECTIVE

This study investigates the effect of ATS on M2 phenotype macrophage polarization in osteosarcoma.

MATERIALS AND METHODS

The differentiation of human THP-1 monocytes into M0 phenotype macrophages was induced by 100 nM phorbol myristate acetate for 24 h, and treated with 20 ng/mL IL-4 and 20 ng/mL IL-13 for 48 h to obtain M2 phenotype macrophages. The function of ATS on the growth and invasion was investigated by cell counting kit-8, transwell, and western blot under the co-culture of M2 phenotype macrophages and osteosarcoma cells for 24 h. The mechanism of ATS on osteosarcoma was assessed using molecular experiments.

RESULTS

ATS reduced the THP-1 cell viability with an IC₅₀ of 128.67 μM. Also, ATS repressed the M2 phenotype macrophage polarization induced by IL-4/IL-13, and the effect was most notably at a 40 μM dose. ATS (40 μM) restrained the growth and invasion of osteosarcoma cells induced by M2 phenotype macrophages. In addition, ATS reduced the tumour necrosis factor receptor-associated factor 6 (TRAF6)/NF-κB activity in osteosarcoma cells and the TRAF6 knockdown reduced the growth and invasion of osteosarcoma cells induced by M2 phenotype macrophages. TRAF6 (2 μg/mL) attenuated the inhibitory effect of ATS on the growth and invasion of osteosarcoma cells caused by M2 phenotype macrophages. In vivo studies further confirmed ATS (2.5, 5, or 10 mg/kg) repressed osteosarcoma tumour growth.

DISCUSSION AND CONCLUSIONS

ATS reversed M2 phenotype macrophage polarization-evoked osteosarcoma cell malignant behaviour by reducing TRAF6/NF-κB activity, suggesting ATS might be a promising drug for the clinical treatment of osteosarcoma.

The molecular mechanisms of vulpinic acid induced programmed cell death in melanoma

BACKGROUNDS

Malignant melanoma is an aggressive skin tumor with a rapidly increasing incidence and there is not yet a successful treatment strategy. Vulpinic acid (VA) is derived from secondary metabolites from lichen species. In the current study, we, for the first time, investigated the anti-cancer effects of VA and the underlying mechanism VA induced programmed cell death in melanoma.

METHODS

The anti-cancer effects of VA on melanoma cells were evaluated by the xCELLigence system, flow cytometry, caspase-3 activity and RT-PCR analysis.

RESULTS

Our results showed that VA had a strong anti-proliferative effect on A-375 melanoma cells without damaging human epidermal melanocyte cells. Additionally, VA promoted apoptotic cell death through G2/M arrest and the activation of both intrinsic and extrinsic apoptosis pathways according to the analysis of 88 genes associated with apoptosis by qRT-PCR.

CONCLUSIONS

Our findings suggest that VA could become an alternative topical and transdermal treatment strategy in the treatment of maligned melanoma cancer. However, further investigations are needed to assess the underlying molecular mechanism of VA mediated apoptotic cell death in the treatment of melanoma.

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.

Targeting the Ubiquitin-Proteasome System for Cancer Therapeutics by Small-Molecule Inhibitors

The ubiquitin-proteasome system (UPS) is a critical regulator of cellular protein levels and activity. It is, therefore, not surprising that its dysregulation is implicated in numerous human diseases, including many types of cancer. Moreover, since cancer cells exhibit increased rates of protein turnover, their heightened dependence on the UPS makes it an attractive target for inhibition via targeted therapeutics. Indeed, the clinical application of proteasome inhibitors in treatment of multiple myeloma has been very successful, stimulating the development of small-molecule inhibitors targeting other UPS components. On the other hand, while the discovery of potent and selective chemical compounds can be both challenging and time consuming, the area of targeted protein degradation through utilization of the UPS machinery has seen promising developments in recent years. The repertoire of proteolysis-targeting chimeras (PROTACs), which employ E3 ligases for the degradation of cancer-related proteins via the proteasome, continues to grow. In this review, we will provide a thorough overview of small-molecule UPS inhibitors and highlight advancements in the development of targeted protein degradation strategies for cancer therapeutics.

Structural feature of TRAFs, their related human diseases and therapeutic intervention

Several studies have been conducted over the years to unravel the structural information on the receptors that bind to tumor necrosis factor receptor-associated factor (TRAF) and the driving forces for the TRAF/receptor complex. In addition, studies have also been performed to highlight the influence of TRAF malfunctioning and mutations on the development of human disease. However, a holistic study that systematically summarizes the available information and the existing clinical trends towards development of the TRAF-targeting drugs has not been conducted to date. Herein, I reviewed existing research that focused on the structural information of various receptors recognized by the different members of the TRAF family. I also reviewed studies on the different human diseases that occur due to TRAF malfunctioning or mutations as well as the clinical trials undertaken to treat TRAF-associated diseases.

miR-146a-5p Plays an Oncogenic Role in NSCLC via Suppression of TRAF6

Non-small cell lung cancer (NSCLC) is the most deadly cancer in the world due to its often delayed diagnosis. Identification of biomarkers with high sensitivity, specificity, and accessibility for early detection, such as circulating microRNAs, is therefore of utmost importance. In the present study, we identified a significantly higher expression of miR-146a-5p in the serum and tissue samples of NSCLC patients than that of the healthy controls. In parallel, miR-146a-5p was also highly expressed in three human NSCLC adenocarcinoma-cell lines (A549, H1299, and H1975) compared to the human bronchial epithelium cell line (HBE). By dual-luciferase reporter assay and manipulation of the expressions of miR-146a-5p and its target gene, tumor necrosis factor receptor-associated factor 6 (TRAF6), we showed that the functional effects of miR-146a-5p on NSCLC cell survival and migration were mediated by direct binding to and suppression of TRAF6. Overexpression of TRAF6 sufficiently reversed miR-146a-5p-induced cancer cell proliferation, migration, and apoptosis resistance. Our data implied that miR-146a-5p/TRAF6/NF-κB-p65 axis could be a promising diagnostic marker and a therapeutic target for NSCLC.

By targeting TRAF6, miR-140-3p inhibits TGF-β1-induced human osteosarcoma epithelial-to-mesenchymal transition, migration, and invasion

OBJECTIVES

We evaluated the effects of miR-140-3p on EMT, cellular migration, and invasion in TGF-β1 treated human OS cells. Human fresh OS tissue and normal bone tissue specimens were gathered from 42 patients (29 male and 13 female, 11 to 24 years of age with a mean age of 17.5 ± 2.3 years) diagnosed with OS by pathology. By targeting TRAF6, miR-140-3p inhibits TGF-β1-induced human osteosarcoma epithelial-to-mesenchymal transition, migration, and invasion.

RESULTS

In this study, we found microRNA (miR)-140-3p to be down-regulated and tumor necrosis factor receptor-associated factor 6 (TRAF6) to be up-regulated in patient OS samples. Lower levels of miR-140-3p and higher levels of TRAF6 were found in the advanced Enneking stage of OS. Furthermore, both mRNA and protein levels of TRAF6 were negatively associated with miR-140-3p mRNA expression in human OS tissue. TRAF6 was verified as a direct target of miR-140-3p in TGF-β1-treated human U2OS cells. Further, a miR-140-3p mimic dramatically inhibited while a miR-140-3p inhibitor enhanced TGF-β1-induced epithelial-to-mesenchymal transition, migration, and invasion of U2OS cells. Small interfering RNA was found to silence TRAF6 and to partly reverse the effects of the miR-140-3p inhibitor on TGF-β1-treated U2OS cells in vitro.

CONCLUSION

These results demonstrate miR-140-3p to function as a tumor inhibitor of human OS cells by decreasing TRAF6 expression. miR-140-3p and TRAF6 may be valuable and novel biomarkers for diagnosis and treatment of OS.

Identification of osteosarcoma driver genes using a network method

Osteosarcoma (OS) is a severe disease that is generally caused by genetic alterations. Systematic identification of driver genes may be used to increase the understanding of the mechanisms underlying the disease. The present study identified a framework to predict driver genes, with the hypothesis that driver genes operate through a number of connected functional genes. OS-related genes were extracted from the Catalogue Of Somatic Mutations In Cancer and subsequently ranked by virtue of their effect on a set of functional genes using a network-based algorithm. This revealed the driver genes associated with dysregulated networks. In addition, compared with the Mutations For Functional Impact on Network Neighbors algorithm, the results obtained using the aforementioned network-based algorithm revealed that the proposed method is effective. Gene functional analysis demonstrated that the potential OS driver genes were involved in OS-associated pathways. Through the validation of the 15 candidate OS driver genes, the classifier constructed in the present study revealed that the identified driver genes were able to distinguish 184 cancer samples from controls. Therefore, the present study provided insights into the identification of driver genes from a vast amount of sequencing data.

Resveratrol induces depletion of TRAF6 and suppresses prostate cancer cell proliferation and migration

Although the early diagnosis of prostate cancer (PCa) enhances life expectancy with a 5-year survival rate of 100 %, metastasized-PCa is the fundamental reason for death by PCa, hence requires an advanced and target-directed treatment strategy. Metastasis is considered to be initiated with the epithelial-mesenchymal transition (EMT) event in which tumor cells change their epithelial characteristics into mesenchymal form and exacerbates the cancer progression. Herein, we investigated the effect and mechanism of resveratrol function in PCa cell proliferation and migration and reported that TNF-receptor associated factor 6 (TRAF6), an unconventional E3 ligase, is a key mediator of resveratrol function to inhibit PCa cell growth and proliferation and targeted for lysosomal degradation by resveratrol. MTT and cell counting demonstrated that resveratrol inhibited the viability and proliferation in DU145 and PC3 cells. Resveratrol (50 μM) mediated the degradation of TRAF6 which in turn facilitated repression of the NF-κB pathway. Also, wound healing and transwell migration assays and level of EMT-related proteins showed that resveratrol used TRAF6, at least in part to inhibit cell migration. Overexpression of TRAF6 augmented EMT in PCa by upregulating the expression of transcription factor SLUG. Moreover, TRAF6 overexpression was closely associated with EMT process through the NF-κB pathway. Our exploration exhibited that resveratrol may inhibit EMT through the TRAF6/NF-κB/SLUG axis. Altogether, this study represents that TRAF6 acts as an intermediary of resveratrol action to suppress PCa cell proliferation and migration, and concerns future attention to obtain as a therapeutic target for the treatment of PCa.

Modified Genomic Self-DNA Influences In Vitro Survival of HT29 Tumor Cells via TLR9- and Autophagy Signaling

In relation of immunobiology, the consequence of the crosstalk between TLR9-signaling and autophagy is poorly documented in HT29 cancer cells. To assess the TLR9-mediated biologic effects of modified self-DNA sequences on cell kinetics and autophagy response HT29 cells were incubated separately with intact genomic (g), hypermethylated (m), fragmented (f), and hypermethylated/fragmented (m/f) self-DNAs. Cell viability, apoptosis, cell proliferation, colonosphere-formation were determined. Moreover, the relation of TLR9-signaling to autophagy response was assayed by real-time RT-PCR, immunocytochemistry and transmission electron microscopy (TEM). After incubation with g-, m-, and m/f-DNAs cell viability and proliferation decreased, while apoptosis increased. F-DNA treatment resulted in an increase of cell survival. Methylation of self-DNA resulted in decrease of TLR9 expression, while it did not influence the positive effect of DNA fragmentation on MyD88 and TRAF6 overexpression, and TNFα downregulation. Fragmentation of DNA abrogated the positive effect of methylation on IRAK2, NFκB and IL-8 mRNA upregulations. In case of the autophagy genes and proteins, g- and f-DNAs caused significant upregulation of Beclin1, Atg16L1, and LC3B. According to TEM analyses, autophagy was present in each group of tumor cells, but to a varying degree. Incubation with m-DNA suppressed tumor cell survival by inducing features of apoptotic cell death, and activated mitophagy. F-DNA treatment enhanced cell survival, and activated macroautophagy and lipophagy. Colonospheres were only present after m-DNA incubation. Our data provided evidence for a close existing interplay between TLR9-signaling and the autophagy response with remarkable influences on cell survival in HT29 cells subjected to modified self-DNA treatments.

TRAF6 promotes the progression and growth of colorectal cancer through nuclear shuttle regulation NF-kB/c-jun signaling pathway

AIMS

TRAF6 is an intracellular signal adapter molecule plays a significant role in tumor development. However, the specific mechanism causes and promotes of colorectal cancer keep largely unknown. Therefore, we sought to investigate the roles and the molecular mechanisms of TRAF6 in regulation colorectal cancer.

MATERIAL AND METHODS

The immunohistochemistry analyzed the expression of TRAF6 in colorectal cancer samples and analyzed the effects of expression of TRAF6 on the prognosis in colorectal cancer. The roles of TRAF6 in regulating colorectal cancer cell proliferation, colony formation, cell migration, cell wound healing and cell invasion were evaluated in vitro. Animal studies were performed to investigate the effects of TRAF6 on tumor growth. mRNA abundance of key genes was analyzed via qPCR. Protein level of TRAF6 and NF-κB/AP-1 signaling pathways was examined by Western blot. Luciferase reporter and Immunofluorescence assays were used to identify the activities NF-κB/AP-1 signaling pathways.

KEY FINDINGS

TRAF6 high expression in colorectal cancer tissues. And colorectal cancer patients with high expression of TRAF6 had a poor survival rate. TRAF6 knockdown can inhibit proliferation, migration, and invasion of colorectal cancer cells in vitro and in vivo experiments. TRAF6 activates the TRAF6-NF-κB/AP-1 signaling pathway by entering the nucleus, causing biobehavioral changes in colorectal cancer cells.

SIGNIFICANCE

TRAF6 plays a vital role in the progression of colorectal cancer. What's more, research elucidating the biological mechanisms of TRAF6 can treated as potential therapeutic target for colorectal cancer.

TRAF6 maintains mammary stem cells and promotes pregnancy-induced mammary epithelial cell expansion

Receptor activator of nuclear factor (NF)-κB (RANK) signaling promotes pregnancy-dependent epithelial cell differentiation and expansion for mammary gland development, which requires NF-κB pathway-dependent Cyclin D1 induction and inhibitor of DNA binding 2 (Id2) pathway-dependent anti-apoptotic gene induction. However, the roles of tumor necrosis factor receptor-associated factor 6 (TRAF6) remain unclear despite its requirement in RANK signaling. Here we show that TRAF6 is crucial for both mammary stem cell maintenance and pregnancy-induced epithelial cell expansion. TRAF6 deficiency impairs phosphoinositide 3-kinase (PI3K)/AKT and canonical NF-κB pathways, whereas noncanonical NF-κB signaling remains functional. Therefore, we propose that TRAF6 promotes cell proliferation by activating PI3K/AKT signaling to induce retinoblastoma phosphorylation in concert with noncanonical NF-κB pathway-dependent Cyclin D1 induction. Furthermore, TRAF6 inhibits apoptosis by activating canonical NF-κB signaling to induce anti-apoptotic genes with the Id2 pathway. Therefore, proper orchestration of TRAF6-dependent and -independent RANK signals likely establishes mammary gland formation.

In vitro and in vivo cancer cell apoptosis triggered by competitive binding of Cinchona alkaloids to the RING domain of TRAF6

TRAF6 is highly expressed in many tumors and plays an important role in the immune system. The aim of this study is to confirm anti-tumor activities of all naturally occurring Cinchona alkaloids that have been screened using computational docking program, and to validate the accuracy and specificity of the RING domain of TRAF6 as a potential anti-tumor target, and to explore their effect on the immune system. Results reported herein would demonstrate that Cinchona alkaloids could induce apoptosis in HeLa cells, inhibit the ubiquitination and phosphorylation of both AKT and TAK1, and up-regulate the ratio of Bax/Bcl-2. In addition, these compounds could induce apoptosis in vivo, and increase the secretion of TNF-α, IFN-γ, and IgG, while not significantly impacting the ratio of CD4+T/CD8+T. These investigations suggest that the RING domain of TRAF6 could serve as a de novo biological target for therapeutic treatment in cancers.

Characterization and anti-inflammatory effects of sulfated polysaccharide from the red seaweed Gelidium pacificum Okamura

In the present study, crude polysaccharides were extracted from Gelidium pacificum Okamura, and further purified to obtain the sulfated polysaccharide with molecular weight of 28,807 Da. Its monosaccharide composition mainly consisted of xylose (7.1%), galactose (59.7%) and galacturonic acid (19.76%). And the sulfate ester content of the sulfated polysaccharide was estimated as 8.8%. Structure analysis showed that the sulfated polysaccharide comprised of 1,4-linked-α-D-Galp3S, 1,2-linked-α-D-Xylp and 1,3-linked-β-D-GalpA residues, respectively. Its anti-inflammatory effects were investigated in LPS-stimulated human monocytic (THP-1) cells. The sulfated polysaccharide at a concentration of 5 μg/mL fully protected the THP-1 cells against LPS-stimulated cytotoxicity. Furthermore, the addition of sulfated polysaccharide resulted in a significant reduction of NO production in LPS-treated cells, and this effect appeared to be dose-related. The sulfated polysaccharide (5 μg/mL) significantly suppressed the mRNA and protein expression of toll-like receptor-4 (TLR-4), myeloid differentiation factor (MyD88) and tumor necrosis factor receptor-associated factor-6 (TRAF-6) in LPS-stimulated THP-1 cells. These results showed the sulfated polysaccharide not only provided a good protection against LPS-induced cell toxicity, but also exerted an anti-inflammatory effect via the TLR4 signaling pathway.

An analysis of the expression and function of myeloid differentiation factor 88 in human osteosarcoma

The aim of the present study was to investigate the expression and function of myeloid differentiation factor 88 (MyD88) in osteosarcoma. Immunohistochemical staining was used to detect MyD88 protein in osteosarcoma tissues and matched normal bone tissues. The association between MyD88 expression and the clinical characteristics of patients with osteosarcoma was analyzed. Furthermore, survival analysis of patients with osteosarcoma was performed to study the association between MyD88 expression and patient prognosis. Finally, the effect of the MyD88 inhibitor, ST2825, on the proliferation and apoptosis of the human osteosarcoma cell line U2OS was examined. Additionally, cell proliferation, invasion and apoptosis were examined using an MTT assay, Transwell assay and Annexin V-fluorescein isothiocyanate staining kit, respectively. The expression of proteins associated with the NF-κB signaling pathway was analyzed by western blotting. The positive expression rate of MyD88 in osteosarcoma and normal bone tissues was 71.4 and 6.1%, respectively. Statistical analysis demonstrated that MyD88 was not associated with gender, age, histological type or tumor location, but that it was associated with Enneking stage and tumor metastasis (P<0.05). According to the survival analysis, patients with osteosarcoma in the high MyD88 expression group displayed a reduced overall survival rate (P<0.05). Furthermore, inhibition of MyD88 by ST2825 in U2OS cells resulted in a marked decrease in cellular proliferation and migration, and an increase in the rate of apoptosis (P<0.05). Notably, ST2825 significantly decreased cyclin D1, matrix metallopeptidase-9 and nucleus p65 expression, but increased cleaved-caspase 3 expression in ST2825-treated U2OS cells (P<0.05). The results of the present study indicated that MyD88 expression is associated with the progression of osteosarcoma and may be a potential therapeutic target for the treatment of osteosarcoma.

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.

Modulating inflammation through the negative regulation of NF-κB signaling

Immune system activation is essential to thwart the invasion of pathogens and respond appropriately to tissue damage. However, uncontrolled inflammation can result in extensive collateral damage underlying a diverse range of auto-inflammatory, hyper-inflammatory, and neoplastic diseases. The NF-κB signaling pathway lies at the heart of the immune system and functions as a master regulator of gene transcription. Thus, this signaling cascade is heavily targeted by mechanisms designed to attenuate overzealous inflammation and promote resolution. Mechanisms associated with the negative regulation of NF-κB signaling are currently under intense investigation and have yet to be fully elucidated. Here, we provide an overview of mechanisms that negatively regulate NF-κB signaling through either attenuation of signal transduction, inhibition of posttranscriptional signaling, or interference with posttranslational modifications of key pathway components. While the regulators discussed for each group are far from comprehensive, they exemplify common mechanistic approaches that inhibit this critical biochemical signaling cascade. Despite their diversity, a commonality among these regulators is their selection of specific targets at key inflection points in the pathway, such as TNF-receptor-associated factor family members or essential kinases. A better understanding of these negative regulatory mechanisms will be essential to gain greater insight related to the maintenance of immune system homeostasis and inflammation resolution. These processes are vital elements of disease pathology and have important implications for targeted therapeutic strategies.

Small interfering RNA-mediated silencing of G-protein-coupled receptor 137 inhibits growth of osteosarcoma cells

Purpose

Osteosarcoma is the most widespread primary carcinoma in bones. Osteosarcoma cells are highly metastatic and frequently develop resistance to chemotherapy making this disease harder to treat. This identifies an urgent need of novel therapeutic strategies for osteosarcoma. G-Protein-coupled receptor 137 (GPR137) is involved in several human cancers and may be a novel therapeutic target.

Methods

The expression of GPR137 was assessed in one osteoblast and three human osteosarcoma cell lines via the quantitative real-time polymerase chain reaction and western blot assays. Stable GPR137 knockdown cell lines were established using an RNA interference lentivirus system. Viability, colony formation, and flow cytometry assays were performed to measure the effects of GPR137 depletion on cell growth. The underlying molecular mechanism was determined using signaling array analysis and western blot assays.

Results

GPR137 expression was higher in the three human osteosarcoma cell lines, Saos-2, U2OS, and SW1353, than in osteoblast hFOB 1.19 cells. Lentivirus-mediated small interfering RNA targeting GPR137 successfully knocked down GPR137 mRNA and protein expression in both Saos-2 and U2OS cells. In the absence of GPR137, cell viability and colony formation ability were seriously impaired. The extent of apoptosis was also increased in both cell lines. Moreover, AMP-activated protein kinase α, proline-rich AKT substrate of 40 kDa, AKT, and extracellular signal-regulated kinase phosphorylation levels were down-regulated in GPR137 knockdown cells.

Conclusions

The results of this study highlight the crucial role of GPR137 in promoting osteosarcoma cell growth in vitro. GPR137 could serve as a potential therapeutic target against osteosarcoma.

Shear stress induces human aortic endothelial cell apoptosis via interleukin‑1 receptor‑associated kinase 2‑induced endoplasmic reticulum stress

Atherosclerosis is characterized by localized lesions distributed in the arterial tree due to the shear stress produced by blood flow. Endothelial cells are directly affected by alterations in blood flow. Dysfunction and injury to endothelial cells has been hypothesized to initiate the pathological processes of atherosclerosis. The present study aimed to investigate the mechanism of shear stress-induced endothelial cellular apoptosis. Shear stress was generated using an artificial device to mimic the impact of disturbed blood flow on cultured human aortic endothelial cells (HAECs). Cellular apoptosis was assessed using a terminal deoxynucleotidyl transferase dUTP nick end labeling assay; an ELISA assay was used to detect the produced interleukin (IL)-1β; specific small interfering (si)RNA was used to knockdown the expression of interleukin-1 receptor-associated kinase 2 (IRAK2) in HAECs and the expression levels of 78 kDa glucose-regulated protein, DNA damage-inducible transcript 3 protein (CHOP), IRAK2 and IL-1β were evaluated using western blotting. The results of the present study demonstrated that artificial shear stress induced endoplasmic reticulum (ER) stress, IL-1β production and apoptosis in HAECs in a time-dependent manner. The inhibition of ER stress, and treatment with interleukin-1 receptor antagonist protein and siRNA against IRAK2 attenuated shear stress-induced CHOP signaling-mediated cellular apoptosis. Therefore, overproduction of IL-1β exacerbated shear stress-induced ER stress-mediated apoptosis via the IRAK2/CHOP signaling pathway in endothelial cells.

A structural perspective on the interactions of TRAF6 and Basigin during the onset of melanoma: A molecular dynamics simulation study

Metastatic melanoma is the most fatal type of skin cancer. The roles of matrix metalloproteinases (MMPs) have well been established in the onset of melanoma. Basigin (BSG) belongs to the immunoglobulin superfamily and is critical for induction of extracellular MMPs during the onset of various cancers including melanoma. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an E3-ligase that interacts with BSG and mediates its membrane localization, which leads to MMP expression in melanoma cells. This makes TRAF6 a potential therapeutic target in melanoma. We here conducted protein-protein interaction studies on TRAF6 and BSG to get molecular level insights of the reactions. The structure of human BSG was constructed by protein threading. Molecular-docking method was applied to develop the TRAF6-BSG complex. The refined docked complex was further optimized by molecular dynamics simulations. Results from binding free energy, surface properties, and electrostatic interaction analysis indicate that Lys340 and Glu417 of TRAF6 play as the anchor residues in the protein interaction interface. The current study will be helpful in designing specific modulators of TRAF6 to control melanoma metastasis.

The Emerging Role of TRAF7 in Tumor Development

The seven members of the tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) family of intracellular proteins were originally discovered and characterized as signaling adaptor molecules coupled to the cytoplasmic regions of receptors of the TNF-R superfamily. Functionally, TRAFs act both as a scaffold and/or enzymatic proteins to regulate activation of mitogen-activated protein kinases (MAPKs) and transcription factors of nuclear factor-κB family (NF-κB). Given the wide variety of stimuli intracellularly conveyed by TRAF proteins, they are physiologically involved in multiple biological processes, including embryonic development, tissue homeostasis, and regulation of innate and adaptive immune responses. In the last few years, it has become increasingly evident the involvement of TRAF7, the last member of the TRAF family to be discovered, in the genesis and progression of several human cancers, placing TRAF7 in the spotlight as a novel tumor suppressor protein. In this paper, we review and discuss the literature recently produced on this subject. J. Cell. Physiol. 232: 1233-1238, 2017. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

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.

TRAF6 regulates melanoma invasion and metastasis through ubiquitination of Basigin

TRAF6 plays a crucial role in the regulation of the innate and adaptive immune responses. Although studies have shown that TRAF6 has oncogenic activity, the role of TRAF6 in melanoma is unclear. Here, we report that TRAF6 is overexpressed in primary as well as metastatic melanoma tumors and melanoma cell lines. Knockdown of TRAF6 with shRNA significantly suppressed malignant phenotypes including cell proliferation, anchorage-independent cell growth and metastasis in vitro and in vivo. Notably, we demonstrated that Basigin (BSG)/CD147, a critical molecule for cancer cell invasion and metastasis, is a novel interacting partner of TRAF6. Furthermore, depletion of TRAF6 by shRNA reduced the recruitment of BSG to the plasma membrane and K63-linked ubiquitination, in turn, which impaired BSG-dependent MMP9 induction. Taken together, our findings indicate that TRAF6 is involved in regulating melanoma invasion and metastasis, suggesting that TRAF6 may be a potential target for therapy or chemo-prevention in melanoma.

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.

Bioinformatics analysis of differentially expressed pathways related to the metastatic characteristics of osteosarcoma

In this study, gene expression data of osteosarcoma (OSA) were analyzed to identify metastasis-related biological pathways. Four gene expression data sets (GSE21257, GSE9508, GSE49003 and GSE66673) were downloaded from Gene Expression Omnibus (GEO). An analysis of differentially expressed genes (DEGs) was performed using the Significance Analysis of Microarray (SAM) method. Gene expression levels were converted into scores of pathways by the Functional Analysis of Individual Microarray Expression (FAIME) algorithm and the differentially expressed pathways (DEPs) were then disclosed by a t-test. The distinguishing and prediction ability of the DEPs for metastatic and non-metastatic OSA was further confirmed using the principal component analysis (PCA) method and 3 gene expression data sets (GSE9508, GSE49003 and GSE66673) based on the support vector machines (SVM) model. A total of 616 downregulated and 681 upregulated genes were identified in the data set, GSE21257. The DEGs could not be used to distinguish metastatic OSA from non-metastatic OSA, as shown by PCA. Thus, an analysis of DEPs was further performed, resulting in 14 DEPs, such as NRAS signaling, Toll-like receptor (TLR) signaling, matrix metalloproteinase (MMP) regulation of cytokines and tumor necrosis factor receptor-associated factor (TRAF)-mediated interferon regulatory factor 7 (IRF7) activation. Cluster analysis indicated that these pathways could be used to distinguish between metastatic OSA from non-metastatic OSA. The prediction accuracy was 91, 66.7 and 87.5% for the data sets, GSE9508, GSE49003 and GSE66673, respectively. The results of PCA further validated that the DEPs could be used to distinguish metastatic OSA from non-metastatic OSA. On the whole, several DEPs were identified in metastatic OSA compared with non-metastatic OSA. Further studies on these pathways and relevant genes may help to enhance our understanding of the molecular mechanisms underlying metastasis and may thus aid in the development of novel therapies.

siRNA-induced TRAF6 knockdown promotes the apoptosis and inhibits the invasion of human lung cancer SPC-A1 cells

Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been found to be involved in multiple cancers. However, the effect of small interfering RNA (siRNA)-induced knockdown of TRAF6 on the biological behaviors of cancer cells remains unknown. Thus, the present study aimed to investigate the effect of siRNA-induced knockdown of TRAF6 on the biological behaviors of human lung cancer SPC-A1 cells. The expression of TRAF6 was determined in human lung adenocarcinoma A549, non-small cell lung cancer H1650, human airway epithelial Calu-3 and human lung cancer SPC-A1 cell lines using quantitative RT-PCR (qRT-PCR) and western blotting at the transcriptional and translational levels. TRAF6 expression was knocked down in the SPC-A1 cells using an siRNA technique, and the effects of TRAF6 knockdown on NF-κB activity, cell proliferation, apoptosis, cell cycle, invasion and migration of the SPC-A1 cells were determined using electrophoretic mobility shift assay (EMSA), cell proliferation assay, flow cytometry, Transwell invasion assay and scratch wound assay. In addition, the protein expression of CD24, CXCR4, MMP1, MMP2, MMP9, TWIST, TIMP-2 and Slug was quantified using western blotting assay. Western blotting and qRT-PCR assays showed upregulation of TRAF6 at both the translational and transcriptional levels in the Calu-3 and SPC-A1 cells, and K63-linked ubiquitination of TRAF6 and constitutive NF-κB activation were detected in the SPC-A1 cells. Knockdown of TRAF6 inhibited the migration and invasion and promoted the apoptosis of the SPC-A1 cells, but had little effect on cell proliferation and the cell cycle. In addition, siRNA-induced TRAF6 knockdown caused a marked reduction in the protein expression of CD24 and CXCR4, but had little effect on MMP-1, MMP-2, MMP-9, Twist, TIMP-2 or Slug expression. The present study demonstrated that TRAF6 is upregulated in human lung cancer cells, and siRNA-induced TRAF6 knockdown inhibits the invasion of lung cancer cells and promotes apoptosis. It is suggested that TRAF6 may be a promising target for the therapy of lung cancer.

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.

Circulating interleukin-1β promotes endoplasmic reticulum stress-induced myocytes apoptosis in diabetic cardiomyopathy via interleukin-1 receptor-associated kinase-2

Aim

IL-1β was considered as an important inflammatory cytokine in diabetic cardiovascular complications. DCM is one of the major manifestations of diabetic cardiovascular complications whose specific mechanisms are still unclear. In this study, we investigated the role of IL-1β in myocytes apoptosis in DCM.

Methods

In the in vitro study, high- glucose medium and/or IL-1β were used to incubate the isolated primary myocytes. siRNA was used to knockdown the irak2 gene expression. Apoptosis was evaluated by Hoechst and TUNEL staining. In the in vivo study, DCM in rats was induced by STZ injection and confirmed by cardiac hemodynamic determinations. The IL-1 receptor antagonist, IL-1Ra was also used to treat DCM rats. Myocardial apoptosis was assessed by TUNEL assay. In both in vitro and in vivo studies, expression levels of GRP-78, IRAK-2 and CHOP were analyzed by Western Blotting. ELISA was employed to exam the IL-1β content in serum and cell supernatants.

Results

Myocytes were not identified as the source of IL-1β secretion under high- glucose incubation. High glucose incubation and/or IL-1β incubation elevated ER- stress mediated myocytes apoptosis which was attenuated by irak2 silencing. Dramatically increased circulating and myocardial IL-1β levels were found in DCM rats which stimulated activation of ER stress and lead to elevated myocytes apoptosis. The administration of IL-1Ra, however, attenuated IRAK2/CHOP induced apoptosis without affecting fasting blood glucose concentration.

Conclusions

Elevated circulating IL-1β contributed to promote ER stress- induced myocytes apoptosis by affecting IRAK-2/CHOP pathway in DCM.

HTLV-1 tax stabilizes MCL-1 via TRAF6-dependent K63-linked polyubiquitination to promote cell survival and transformation

The human T-cell leukemia virus type 1 (HTLV-1) Tax protein hijacks the host ubiquitin machinery to activate IκB kinases (IKKs) and NF-κB and promote cell survival; however, the key ubiquitinated factors downstream of Tax involved in cell transformation are unknown. Using mass spectrometry, we undertook an unbiased proteome-wide quantitative survey of cellular proteins modified by ubiquitin in the presence of Tax or a Tax mutant impaired in IKK activation. Tax induced the ubiquitination of 22 cellular proteins, including the anti-apoptotic BCL-2 family member MCL-1, in an IKK-dependent manner. Tax was found to promote the nondegradative lysine 63 (K63)-linked polyubiquitination of MCL-1 that was dependent on the E3 ubiquitin ligase TRAF6 and the IKK complex. Tax interacted with and activated TRAF6, and triggered its mitochondrial localization, where it conjugated four carboxyl-terminal lysine residues of MCL-1 with K63-linked polyubiquitin chains, which stabilized and protected MCL-1 from genotoxic stress-induced degradation. TRAF6 and MCL-1 played essential roles in the survival of HTLV-1 transformed cells and the immortalization of primary T cells by HTLV-1. Therefore, K63-linked polyubiquitination represents a novel regulatory mechanism controlling MCL-1 stability that has been usurped by a viral oncogene to precipitate cell survival and transformation.

HTLV-1 infection is etiologically linked to the development of the neuroinflammatory disorder HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia (ATL), an aggressive CD4+CD25+ malignancy. The HTLV-1 regulatory protein Tax constitutively activates the IκB kinases (IKKs) and NF-κB to promote cell survival, proliferation and transformation. However, the precise mechanisms by which Tax and IKK regulate cell survival are largely unknown. Here, we found that Tax interacts with and activates the host ubiquitin ligase TRAF6, and promotes a redistribution of TRAF6 to the mitochondria. TRAF6 conjugates the anti-apoptotic BCL-2 family member MCL-1 with lysine 63 (K63)-linked polyubiquitin chains that antagonize MCL-1 interaction with the 20S proteasome, thereby protecting MCL-1 from degradation elicited by chemotherapeutic drugs. TRAF6 and MCL-1 both played pivotal roles in the survival of ATL cells and the immortalization of primary T cells by HTLV-1. Overall, our study has identified a novel TRAF6/MCL-1 axis that has been subverted by the HTLV-1 Tax protein to maintain the survival of HTLV-1 infected T cells.

Knockdown of TRAF4 expression suppresses osteosarcoma cell growth in vitro and in vivo

Tumor necrosis factor (TNF) receptor-associated factor 4 (TRAF4) is an adapter molecule that is overexpressed in certain cancers. TRAF4 is overexpressed in osteosarcoma tissues and osteosarcoma cells. Using the technique of RNA interference, the expression of TRAF4 in the human osteosarcoma Saos-2 cell line was shown to be downregulated. The proliferation, cell cycle arrest and apoptosis ability of Saos‑2 cells were examined, as was tumor development in a xenograft mouse model. The results showed that the TRAF4 knockdown exerts inhibitory effects on the proliferation ability of Saos-2 cells and tumor development in a xenograft mouse model. Simultaneously, it was found that TRAF4 knockdown led to cell cycle arrest in the G1 phase and promoted Saos-2 cell apoptosis. Following TNF-α treatment, the expression of nuclear factor κB was significantly reduced in the TRAF4‑small interfering RNA group. These results indicate that TRAF4 regulated osteosarcoma cell growth in vitro and in vivo, and offers a candidate molecular target for osteosarcoma prevention and therapy.

Genome-wide association studies for growth and meat production traits in sheep

BACKGROUND

Growth and meat production traits are significant economic traits in sheep. The aim of the study is to identify candidate genes affecting growth and meat production traits at genome level with high throughput single nucleotide polymorphisms (SNP) genotyping technologies.

METHODOLOGY AND RESULTS

Using Illumina OvineSNP50 BeadChip, we performed a GWA study in 329 purebred sheep for 11 growth and meat production traits (birth weight, weaning weight, 6-month weight, eye muscle area, fat thickness, pre-weaning gain, post-weaning gain, daily weight gain, height at withers, chest girth, and shin circumference). After quality control, 319 sheep and 48,198 SNPs were analyzed by TASSEL program in a mixed linear model (MLM). 36 significant SNPs were identified for 7 traits, and 10 of them reached genome-wise significance level for post-weaning gain. Gene annotation was implemented with the latest sheep genome Ovis_aries_v3.1 (released October 2012). More than one-third SNPs (14 out of 36) were located within ovine genes, others were located close to ovine genes (878bp-398,165bp apart). The strongest new finding is 5 genes were thought to be the most crucial candidate genes associated with post-weaning gain: s58995.1 was located within the ovine genes MEF2B and RFXANK, OAR3_84073899.1, OAR3_115712045.1 and OAR9_91721507.1 were located within CAMKMT, TRHDE, and RIPK2 respectively. GRM1, POL, MBD5, UBR2, RPL7 and SMC2 were thought to be the important candidate genes affecting post-weaning gain too. Additionally, 25 genes at chromosome-wise significance level were also forecasted to be the promising genes that influencing sheep growth and meat production traits.

CONCLUSIONS

The results will contribute to the similar studies and facilitate the potential utilization of genes involved in growth and meat production traits in sheep in future.

TRAF molecules in cell signaling and in human diseases

The tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) family of intracellular proteins were originally identified as signaling adaptors that bind directly to the cytoplasmic regions of receptors of the TNF-R superfamily. The past decade has witnessed rapid expansion of receptor families identified to employ TRAFs for signaling. These include Toll-like receptors (TLRs), NOD-like receptors (NLRs), RIG-I-like receptors (RLRs), T cell receptor, IL-1 receptor family, IL-17 receptors, IFN receptors and TGFβ receptors. In addition to their role as adaptor proteins, most TRAFs also act as E3 ubiquitin ligases to activate downstream signaling events. TRAF-dependent signaling pathways typically lead to the activation of nuclear factor-κBs (NF-κBs), mitogen-activated protein kinases (MAPKs), or interferon-regulatory factors (IRFs). Compelling evidence obtained from germ-line and cell-specific TRAF-deficient mice demonstrates that each TRAF plays indispensable and non-redundant physiological roles, regulating innate and adaptive immunity, embryonic development, tissue homeostasis, stress response, and bone metabolism. Notably, mounting evidence implicates TRAFs in the pathogenesis of human diseases such as cancers and autoimmune diseases, which has sparked new appreciation and interest in TRAF research. This review presents an overview of the current knowledge of TRAFs, with an emphasis on recent findings concerning TRAF molecules in signaling and in human diseases.

TNF receptor-associated factor 6 regulates proliferation, apoptosis, and invasion of glioma cells

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.

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.