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Epilepsy refers to a group of neurological disorders of varying etiologies characterized by recurrent seizures, resulting in brain dysfunction. Endoplasmic reticulum (ER) stress is highly activated in the process of epilepsy-related brain injury. However, the mechanisms by which ER stress triggers neuronal apoptosis remain to be fully elucidated. Tribbles pseudokinase 3 (TRIB3) is a pseudokinase that affects a number of cellular functions, and its expression is increased during ER stress. Here, we sought to clarify the role of TRIB3 in neuronal apoptosis mediated by ER stress. In the kainic acid (KA) (10 mg/kg)-induced rat seizure model, we characterized neuronal injury and apoptosis after KA injection. KA induced an ER stress response, as indicated by elevated expression of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). TRIB3 protein was upregulated concomitantly with the downregulation of phosphorylated-protein kinase B (p-AKT) in rats following KA administration. In rat cortical neurons treated with KA, TRIB3 knockdown by siRNA reduced the number of dying neurons, decreased the induction of GRP78 and CHOP and the activation of caspase-3, and blocked the dephosphorylation of AKT after KA treatment. Our findings indicate that TRIB3 is involved in neuronal apoptosis occurring after KA-induced seizure. The knockdown of TRIB3 effectively protects against neuronal apoptosis in vitro, suggesting that TRIB3 may be a potential therapeutic target for the treatment of epilepsy.

The Tribbles (TRIB) family of pseudokinase proteins has been shown to play key roles in cell cycle, metabolic diseases, chronic inflammatory disease, and cancer development. A better understanding of the mechanisms of TRIB pseudokinases could provide new insights for disease development and help promote TRIB proteins as novel therapeutic targets for drug discovery. At the 2nd International Symposium on Tribbles and Diseases held on May 7-9, 2018 in Beijing, China, a group of leading Tribbles scientists reported their findings and ongoing studies about the effects of the different TRIB proteins in the areas of immunity, metabolism, fundamental cell biology and cancer. Here, we summarize important and insightful overviews from 4 keynote lectures, 13 plenary lectures and 8 short talks that took place during this meeting. These findings may offer new insights for the understanding of the roles of TRIB pseudokinases in the development of various diseases. (C) 2019 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V. Dr. Zhuowei Hu' s work was supported by National Key R&D Program of China (Grant No. 2017YFA0205400, China), the National Natural Science Foundation of China (Grant Nos. 81530093 and 81773781, China), Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Sciences (Grant No. 2016-12M-1-007, China) and CAMS Central Public-interest Scientific Institution Basic Research Fund (Grant No. 2017PT3104, China); Dr. Bing Cui' s work was supported by grants of the National Natural Science Foundation of China (Grant No. 81874316, China), the CAMS Innovation Fund for Medical Sciences (Grant No. 2016-I2M-3-008, China); Dr. Patrick A. Eyers' s work was supported by grants of from the BBSRC and NWCR (Grant Nos. 1088 and 1097, UK); Dr. Leonard L. Dobens' s work was supported by grants of NSF (Grant No. IOS-1456023, USA), NIH (Grant No. NIH R21 CA197317, USA); Dr. Nguan Soon Tan' s work was supported by grants of Ministry of Education, Singapore (Grant Nos. MOE2014-T2-1-012 and 2012-T1-001-036, Singapore); Dr. Peter D. Mace' s work was supported by grants from the Health Research Council of New Zealand, and additionally supported by a Rutherford Discovery Fellowship from the New Zealand government administered by the Royal Society of New Zealand; Dr. Wolfgang Link' s work was supported by Fundacao para a Ciencia e a Tecnologia (FCT) Research Center Grant UID/KM/04773/2013 Centre for Biomedical Research 1334, by a research grant from Liga Portuguesa Contra o Cancro NUcleo Regional do Sul (LPCC/NRS, Portugal), Terry Fox, by a FCT 2014 research grant SFRH/BPD/100434/2014 and a ProRegem grant PD/BD/114258/2016 (Portugal); Dr. Endre Kiss-Toth' s work was supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU)and Innovation Network and the British Heart Foundation (PG/16/44/32146, UK); Dr. Karen Keeshan' s work was supported by grants from The Howat Foundation Ltd. (UK), Children with Cancer UK, Bloodwise and the Friends of Paul O' Gorman (UK); Dr. Takuro Nakamura' s work was supported by grants of P-CREATE from Japan Agency for Medical Research and Development; Dr. Warren S. Pear' s work was supported by grants from the NIH (NIAID, USA), Alex' s Lemonade Stand Foundation (USA) and the Samuel Waxman Cancer Research Foundation (USA); Yodit Feseha is supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU). Yodit Feseha' s work is conducted in the context of the "Fondation Centaure" (RTRS), which supports a French transplantation research network, the 1HU-Cesti project, the DHU Oncogreffe and the LabEX IGO thanks to French government financial support managed by the National Research Agency via the "Investment into the Future" program (Grant Nos. ANR-10-IBHU-005 and ANR-11-LABX-0016-01, France). The IHU-Cesti project is also supported by Nantes Metropole and Region Pays de la Loire (France); Dr. Jessica Johnston's work was supported by grants of the British Heart Foundation (PG/16/44/32146, UK); Dr. Arkatiz Carracedo' s work was supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU); Dr. Marcel Scheideler' s work was supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU); Dr. Zabran llyas' s work was supported by a joint Ph.D studentship beween the A* Star Institute and the University of Sheffield (UK); Dr. Robert C. Bauer s work was supported by funding from the National Institutes of Health National Heart, Lung, and Blood Institute (R01HL141745, USA); Dominika Grzesik' s work was supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU); Juan Salamanca-Viloria's work was supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU); Dr. Xiaoxi Lv' s work was supported by the National Natural Science Foundation of China (Grant No. 81503128, China) and CAMS Innovation Fund for Medical Sciences (Grant No. 201642M-1-008, China); Dr. Yishi Jin' s work was supported by National Institute of Health (NS R01-035546, USA); Dr. Ke Li' s work was supported by the National Natural Science Foundation of China (Grant No. 81400140, China), and CAMS Innovation Fund for Medical Sciences (Grant No. 201642M-1-011, China); Dr. Guillermo Velasco' s work was supported by European Marie Sklodowska Curie ITN Project TRAIN-TRIBBLES Research and Innovation Network (Grant No. 721532, EU); Dr. Jose M. Lizcano's work was supported by Spanish Ministry of Economy and Competitiveness (MINECO) and Fondo Europeo de desarrollo Regional (FEDER) (Grant No. INNPACTO/IPT-2012-0614-010000, Spain); Dr. Xiaowei Zhang' s work was supported by the National Natural Science Foundation of China (Grant Nos. 81400286 and 81530093, China), and the CAMS Innovation Fund for Medical Sciences (Grant No. 201642M-1-010, China); Dr. Fang Hua' s work was supported by the National Natural Science Foundation of China (Grant Nos. 81472717 and 81673474, China), Beijing Natural Science Foundation (Grant No. 7162133, China), and the CAMS Innovation Fund for Medical Sciences (Grant No. 201642M-1-007, China); Dr. Jiaojiao Yu' s work was supported by the National Natural Science Foundation of China (Grant No. 81703564, China); Dr. Jinmei Yu' s work was supported by the National Natural Science Foundation of China (Grant No. 81603129, China). In addition, the Meeting Organizing Committee was greatly thankful to PerkinElmer and Innovent Biologics for their generous financial supports, as well as Dr. Zhuowei Hu' s laboratory members for their assistance in preparing and organizing the conference.

Background Tribble pseudokinase 3 (TRIB3) plays a key role in regulating the malignancy of many tumors. This study examined its function in cancer cells and explored the potential mechanisms of action. Methods The expression of TRIB3 was examined in hepatocellular carcinomas (HCCs) using The Cancer Genome Atlas (TCGA) database. A TRIB3 lentivirus with a flag label was constructed and transfected into Huh7 and Hep3B human hepatoma cell lines to generate cells that stably overexpress TRIB3. A small interfering RNA (siRNA) was designed to knockdown TRIB3 mRNA in HepG2 and Huh7. Cell viability and cell colony formation assays were conducted. Flow cytometry was performed to assess the cell cycle in cells overexpressing TRIB3. Western blotting were performed to examine the expression of (Mitogen-activated protein kinase, MAPKK) (MEK), phosphorylated-MEK (p-MEK), extracellular signal-regulated kinase (ERK), and p-MEK in cells with TRIB3 knockdown. The correlation between TRIB3 and SMARCD3 was assessed using co-immunoprecipitation assays and immunofluorescence. Results TRIB3 was significantly overexpressed in advanced grade HCC tissues and was closely correlated with poor prognosis. TRIB3 overexpression promoted the cell growth and cell cycle but had little effect on migration capabilities in Huh7 and Hep3B cells. Conversely, knockdown of TRIB3 had slow down the cell growth in Huh7 and HepG2 cells detected by CCK8 and colony formation assay. The expression of MEK and ERK at both the protein and mRNA levels were downregulated when TRIB3 was knocked down. The protein expression of p-ERK and p-MEK were also downregulated upon TRIB3 silencing. SMARCD3 is a transcript factor that is belongs to the SWI/SNF complex and has been shown to regulate many genes. Indeed, co-immunoprecipitation assays demonstrated that TRIB3 interacts with SMARCD3 in the nucleus, suggesting that it may regulate TRIB3 in HCCs. Conclusions This study demonstrated that TRIB3 promotes the malignancy of HCC cells and its expression may be a potential diagnostic biomarker for HCC progression.

Methamphetamine (Meth) is a neuro-stimulator substrate which might lead to neural cell death and the activation of several interconnected cellular pathways as well. However, the precise molecular mechanisms underlying Meth-induced neural cell death remained unclear yet. The current study aimed to assess the specific relationship between long-term Meth exposure and several endoplasmic reticulum stress, autophagy, and apoptosis associated markers including C/EBP homologous protein (CHOP), Tribbles homolog 3(Trib3), Nuclear protein 1(NUPR1), and Beclin-1 expression in postmortem human striatum. Therefore, the effects of long-term Meth exposure on autophagy and apoptosis in the striatum of postmortem users were evaluated and molecular, immunehistochemical, and histological examinations were performed on 10 control and 10 Meth-addicted brains. The level of CHOP, Trib3, NUPR1, and Beclin-1, Microtubule-associated proteins 1A/1B light chain 3B(LC3), Caspase 3, and Autophagy protein 5 (ATG5) were measured by using qPCR and immunohistochemistry. Stereological neural cell counting, Hematoxylin and Eosin, Nissl and Tunel staining were also performed. Based on our findings, the expression level of CHOP, Trib3, NUPR1, and Beclin-1 in the striatum of Meth group were significantly higher than the control group. Besides, the neuronal cell death was substantially increased in the striatum based on data obtained from the Tunel assay and the stereological analysis. Long-term presence of Meth in the brain can induce ER stress and overexpression of NUPR1 which is associated with the upregulation of CHOP, a pro-apoptotic transcription factor. Moreover, an increase in Trib3 expression is implicated in CHOP-dependent autophagic cell death during Meth-induced ER stress accompanied by an increase in neuronal cell death in the striatum of the postmortem human brains. Beclin 1 expression was also upregulated which may due to the activation of autophagic mechanisms upon prolonged Meth exposure.

Simple Summary Accumulating evidence supports a key function for Tribbles proteins in oncogenesis, both in leukemia and solid tumors. However, the exact role of these proteins is hard to define since in a context-dependent manner they can function as both oncogenes and tumor suppressors. Their complex role arises from the capacity to interact with a wide range of target molecules thereby acting as molecular scaffolds and signaling regulators of multiple pathways. This review focuses on one particular Tribbles family member, namely, TRIB3, addressing its gene and protein expression, as well as its role in cancer development and progression. Abstract The first Tribbles protein was identified as critical for the coordination of morphogenesis in Drosophila melanogaster. Three mammalian homologs were subsequently identified, with a structure similar to classic serine/threonine kinases, but lacking crucial amino acids for the catalytic activity. Thereby, the very weak ATP affinity classifies TRIB proteins as pseudokinases. In this review, we provide an overview of the regulation of TRIB3 gene expression at both transcriptional and post-translational levels. Despite the absence of kinase activity, TRIB3 interferes with a broad range of cellular processes through protein–protein interactions. In fact, TRIB3 acts as an adaptor/scaffold protein for many other proteins such as kinase-dependent proteins, transcription factors, ubiquitin ligases, or even components of the spliceosome machinery. We then state the contribution of TRIB3 to cancer development, progression, and metastasis. TRIB3 dysregulation can be associated with good or bad prognosis. Indeed, as TRIB3 interacts with and regulates the activity of many key signaling components, it can act as a tumor-suppressor or oncogene in a context-dependent manner.

Amyloid-β (Aβ)-induced neuron death is considered central to the pathogenesis of Alzheimer's disease (AD). Among several death modalities, autophagy and apoptosis play important roles in Aβ-induced neuron death suggesting that there may be regulatory mechanisms that initiate both cell death pathways. However, molecules that govern both pathways have not been identified. Here, we report that, upon Aβ treatment, tribbles pseudokinase 3 (Trib3, an ortholog of Drosophila Tribbles) is up-regulated in neurons both in vivo and in vitro. Increased Trib3 levels inhibited the activity of the kinase Akt by interacting with it. As a result, forkhead box O1 (FoxO1), a transcription factor that is negatively regulated by Akt, was activated, translocated to the nucleus, and induced the pro-apoptotic gene BCL2-like 11 (Bim). Conversely, FoxO1 responded to Aβ insult by binding to the Trib3 gene promoter, enhancing its expression. Our investigations further revealed that Trib3 also induces autophagy. We found that Trib3 indirectly activates unc-51-like autophagy-activating kinase1 (Ulk1) by impeding phosphorylation of, and thus inactivating, a negative regulator of Ulk1, mechanistic target of rapamycin. Ulk1 activation augmented autophagosome formation and reduced autophagy flux. Thus, Trib3 was required for formation of autophagosomes, which accumulated in neurons as autophagic flux was thwarted. Most importantly, silencing endogenous Trib3 strongly protected neurons from Aβ insult. Our results suggest that a self-amplifying feed-forward loop among Trib3, Akt, and FoxO1 in Aβ-treated neurons induces both apoptosis and autophagy, culminating in neuron death. Thus, Trib3 may serve as a potential therapeutic target for AD.

Arsenic, a metalloid with cytotoxic and carcinogenic effects related to the disruption of glutathione homeostasis, induces the expression of ATF4, a central transcription factor in the cellular stress response. However, the interplay between factors downstream of ATF4 is incompletely understood. In this article, we investigate the role of Tribbles homolog 3 (TRIB3), a regulatory member of the ATF4 pathway, in determining cell sensitivity to arsenite. Our results show that arsenite potently upregulates Trib3 mRNA and protein in an ATF4-dependent manner in mouse embryonic fibroblasts. Trib3-deficient cells display increased susceptibility to arsenite-induced cell death, which is rescued by re-expressing TRIB3. In cells lacking TRIB3, arsenite stress leads to markedly elevated mRNA and protein levels of Chac1, a gene that encodes a glutathione-degrading enzyme and is not previously known to be repressed by TRIB3. Analysis of the Chac1 promoter identified two regulatory elements that additively mediate the induction of Chac1 by arsenite and ATF4, as well as the robust suppression of Chac1 by TRIB3. Crucially, Chac1 silencing enhances glutathione levels and eliminates the increased susceptibility of Trib3-deficient cells to arsenite stress. Moreover, Trib3-deficient cells demonstrate an increased rate of glutathione consumption, which is abolished by Chac1 knockdown. Taken together, these data indicate that excessive Chac1 expression is detrimental to arsenite-treated cell survival and that TRIB3 is critical for restraining the pro-death potential of Chac1 during arsenite stress, representing a novel mechanism of cell viability regulation that occurs within the ATF4 pathway.

Mice expressing connexin50D47A (Cx50D47A) exhibit nuclear cataracts and impaired differentiation. Cx50D47A does not traffic properly, and homozygous mutant lenses show increased levels of the stress-responsive αB-crystallins. Therefore, we assessed whether expression of Cx50D47A led to endoplasmic reticulum (ER) stress in the lens in vivo. Although pharmacologic induction of ER stress can be transduced by three different pathways, we found no evidence for activation of the IRE1α or ATF6 pathways in Cx50D47A-expressing lenses. In contrast, heterozygous and homozygous Cx50D47A lenses showed an increase in phosphorylated PERK immunoreactivity and in the ratio of phosphorylated to total EIF2α (2.4- and 3.3-fold, respectively) compared with wild type. Levels of ATF4 were similar in wild type and heterozygous lenses but elevated in homozygotes (391%). In both heterozygotes and homozygotes, levels of calreticulin protein were increased (184 and 262%, respectively), as was Chop mRNA (1.9- and 12.4-fold, respectively). CHOP protein was increased in homozygotes (384%). TUNEL staining was increased in Cx50D47A lenses, especially in homozygous mice. Levels of two factors that may be pro-survival, Irs2 and Trib3, were greatly increased in homozygous lenses. These results suggest that expression of Cx50D47A induces ER stress, triggering activation of the PERK-ATF4 pathway, which potentially contributes to the lens pathology and leads to increased expression of anti-apoptotic factors, allowing cell survival.

Aims/hypothesis Hypoxia may contribute to beta cell failure in type 2 diabetes and islet transplantation. The adaptive unfolded protein response (UPR) is required for endoplasmic reticulum (ER) homeostasis. Here we investigated whether or not hypoxia regulates the UPR in beta cells and the role the adaptive UPR plays during hypoxic stress. Methods Mouse islets and MIN6 cells were exposed to various oxygen (O2) tensions. DNA-damage inducible transcript 3 (DDIT3), hypoxia-inducible transcription factor (HIF)1α and HSPA5 were knocked down using small interfering (si)RNA; Hspa5 was also overexpressed. db/db mice were used. Results Hypoxia-response genes were upregulated in vivo in the islets of diabetic, but not prediabetic, db/db mice. In isolated mouse islets and MIN6 cells, O2 deprivation (1–5% vs 20%; 4–24 h) markedly reduced the expression of adaptive UPR genes, including Hspa5, Hsp90b1, Fkbp11 and spliced Xbp1. Coatomer protein complex genes (Copa, Cope, Copg [also known as Copg1], Copz1 and Copz2) and ER-to-Golgi protein trafficking were also reduced, whereas apoptotic genes (Ddit3, Atf3 and Trb3 [also known as Trib3]), c-Jun N-terminal kinase (JNK) phosphorylation and cell death were increased. Inhibition of JNK, but not HIF1α, restored adaptive UPR gene expression and ER-to-Golgi protein trafficking while protecting against apoptotic genes and cell death following hypoxia. DDIT3 knockdown delayed the loss of the adaptive UPR and partially protected against hypoxia-induced cell death. The latter response was prevented by HSPA5 knockdown. Finally, Hspa5 overexpression significantly protected against hypoxia-induced cell death. Conclusions/interpretation Hypoxia inhibits the adaptive UPR in beta cells via JNK and DDIT3 activation, but independently of HIF1α. Downregulation of the adaptive UPR contributes to reduced ER-to-Golgi protein trafficking and increased beta cell death during hypoxic stress.

This research was conducted in order to determine the effects of omega-3 on oocyte in vitro maturation and the level of expression of tribbles (TRIB1, TRIB2 and TRIB3 genes) in cumulus cells. Eight-ten weeks old NMRI mice were super-ovulated using 7.5 IU pregnant mare’s serum gonadotropin (PMSG, Intraperitoneal) and they were killed after 44 hours and their ovaries were removed. The oocytes were used for in vitro maturation and the cumulus-oocyte complexes (COCs) were released. Cumulus cells and oocytes were assigned into control, ethanol-treated and groups exposed to 10 and 100 μg/ml of omega-3. The cells were prepared to assess the maturation stage in order to evaluate the gene expression level. The data were statistically analyzed. Exposing oocytes to low dose (10 μg/ml) and high dose (100 μg/ml) of omega-3 resulted in a reduced rate of GV-stage oocytes, decreased MI-oocytes and increased MII-oocytes. The enhanced maturity of COCs was also detected in response to a high dose of omega-3 (100 μg/ml). Exposure of cumulus cells to omega-3 (10 and 100 μg/ml) induced TRIB2 and inhibited TRIB3 gene expression level; however, TRIB1 gene expression level increased and decreased in response to low (10 μg/ml) and high (100 μg/ml) concentrations of omega-3, respectively. The addition of omega-3 to the environment of oocytes or cumulus cells affected the maturation of oocytes and cumulus cells, which was followed by the differential expression of TRIB genes, suggesting that there was a role of fatty acid metabolism in the differentiation and maturation of cumulus cells.

Obesity patients are more susceptible to develop COVID-19 severe outcome due to the role of angiotensin-converting enzyme 2 (ACE2) in the viral infection. ACE2 is regulated in the human cells by different genes associated with increased (TLR3, HAT1, HDAC2, KDM5B, SIRT1, RAB1A, FURIN and ADAM10) or decreased (TRIB3) virus replication. RNA-seq data revealed 14857 genes expressed in human subcutaneous adipocytes, including genes mentioned above. Irisin treatment increased by 3-fold the levels of TRIB3 transcript and decreased the levels of other genes. The decrease in FURIN and ADAM10 expression enriched diverse biological processes, including extracellular structure organization. Our results indicate a positive effect of irisin on the expression of multiple genes related to viral infection in the adipose tissue; furthermore, translatable for other tissues and organs targeted by the novel coronavirus and present, thus, promising approaches for the treatment of COVID-19 infection as therapeutic strategy to decrease ACE2 regulatory genes., Highlights • Genes associated with increased virus, SARS-CoV-2, replication are diminished, whereas, the gene that decreases virus replication is elevated by irisin in human subcutaneous adipocytes. • TRIB3 is increased by irisin. • Irisin diminished FURIN and ADAM10 in human subcutaneous adipocytes.

Aims Tribbles homolog 3 (TRIB3) is emerging as a multifunctional oncoprotein associated with various cellular events in different tumors. However, the regulatory mechanism of TRIB3 in acute myeloid leukemia (AML) remains unknown. This study aims to investigate the molecular mechanisms and uncover the functions of TRIB3 in AML. Methods Western blotting and quantitative real-time PCR were used to analyze the expression levels of TRIB3, peroxisome proliferator-activated receptor α (PPARα), apoptosis markers and autophagy markers in AML cells. Flow cytometry was used to assess cell apoptosis. The interaction of TRIB3 and PPARα was evaluated by immunofluorescence, coimmunoprecipitation, and in vivo ubiquitination assays. Key findings We demonstrated that downregulating TRIB3 in leukemic cells effectively induced apoptosis and autophagy by regulating the degradation of PPARα. Mechanistically, TRIB3 interacted with PPARα and contributed to its destabilization by promoting its ubiquitination. When PPARα was activated by its specific agonist clofibrate, the apoptosis and autophagy of AML cells were significantly enhanced. These results were confirmed by rescue experiments. Blocking PPARα expression using the PPARα inhibitor GW6471 reversed the functional influence of TRIB3 on AML cells. Significance The aim of this study is to provide evidence of the degradation of PPARα by TRIB3 via ubiquitin-dependent proteasomal degradation. This process meditates the progression of AML and prolongs the survival of leukemic cells. As a result, these data indicate that TRIB3 is a novel and promising therapeutic target for AML treatment.

Purpose: The resistance to differentiation therapy and early death caused by fatal bleeding endangers the health of a significant proportion of patients with acute promyelocytic leukemia (APL). This study aims to investigate the molecular mechanisms of all-trans retinoic acid (ATRA) resistance and uncover new potential therapeutic strategies to block the rapid progression of early death. Experimental Design: The important role of TWIST1 in APL leukemogenesis was first determined by gain- and loss-of-function assays. We then performed in vivo and in vitro experiments to explore the interaction of TWIST1 and TRIB3 and develop a potential peptide-initiated therapeutic opportunity to protect against early death and induction therapy resistance in patients with APL. Results: We found that the epithelial–mesenchymal transition (EMT)-inducing transcription factor TWIST1 is highly expressed in APL cells and is critical for leukemic cell survival. TWIST1 and TRIB3 were highly coexpressed in APL cells compared with other subtypes of acute myeloid leukemia cells. We subsequently demonstrated that TRIB3 could bind to the WR domain of TWIST1 and contribute to its stabilization by inhibiting its ubiquitination. TRIB3 depletion promoting TWIST1 degradation reverses resistance to induction therapy and improves sensitivity to ATRA. On the basis of a detailed functional screen of synthetic peptides, we discovered a peptide analogous to the TWIST1 WR domain that specifically represses APL cell survival by disrupting the TRIB3/TWIST1 interaction. Conclusions: Our data not only define the essential role of TWIST1 as an EMT-TF in patients with APL but also suggest that disrupting the TRIB3/TWIST1 interaction reverses induction therapy resistance and blocks rapid progression of APL early death. See related commentary by Peeke and Gritsman, p. 6018

Post-translational modifications directly control protein activity and, thus, they represent an important means to regulate the responses of cells to different stimuli. Protein SUMOylation has recently been recognised as one such modification, and it has been associated with various diseases, including different types of cancer. However, the precise way that changes in SUMOylation influence the tumorigenic properties of cells remains to be fully clarified. Here, we show that blocking the SUMO pathway by depleting SUMO1 and UBC9, or by exposure to ginkgolic acid C15:1 or 2-D08 (two different SUMOylation inhibitors), induces cell death, also inhibiting the invasiveness of tumour cells. Indeed, diminishing the formation of SUMO1 complexes induces autophagy-mediated cancer cell death through increasing the expression of Tribbles pseudokinase 3 (TRIB3). Moreover, we found that blocking the SUMO pathway inhibits tumour cell invasion by decreasing RAC1 SUMOylation. These findings shed new light on the mechanisms by which SUMO1 modifications regulate the survival, and the migratory and invasive capacity of tumour cells, potentially establishing the bases to develop novel anti-cancer treatments based on the inhibition of SUMOylation., Summary: Blockade of the SUMO pathway inhibits tumorigenesis through two different mechanisms: (i) stimulation of autophagy-mediated cancer cell death via TRIB3 upregulation; and (ii) inhibition of invasiveness via abrogation of RAC1 SUMOylation.

Impaired macroautophagy/autophagy is involved in the pathogenesis of hepatic fibrosis. However, how aberrant autophagy promotes fibrosis is far from understood. Here, we aimed to define a previously unrevealed pro-fibrotic mechanism for the stress protein TRIB3 (tribbles pseudokinase 3)-mediated autophagy dysfunction. Human fibrotic liver tissues were obtained from patients with cirrhosis who underwent an open surgical repair process. The functional implications of TRIB3 were evaluated in mouse models of hepatic fibrosis induced by bile duct ligation (BDL) or thioacetamide (TAA) injection. Human fibrotic liver tissues expressed higher levels of TRIB3 and selective autophagic receptor SQSTM1/p62 (sequestosome 1) than nonfibrotic tissues and the elevated expression of TRIB3 and SQSTM1 was positively correlated in the fibrotic tissues. Silencing Trib3 protected against experimentally induced hepatic fibrosis, accompanied by restored autophagy activity in fibrotic liver tissues. Furthermore, TRIB3 interacted with SQSTM1 and hindered its binding to MAP1LC3/LC3, which caused the accumulation of SQSTM1 aggregates and obstructed autophagic flux. The TRIB3-mediated autophagy impairment not only suppressed autophagic degradation of late endosomes but also promoted hepatocellular secretion of INHBA/Activin A-enriched exosomes which caused migration, proliferation and activation of hepatic stellate cells (HSCs), the effector cells of liver fibrosis. Disrupting the TRIB3-SQSTM1 interaction with a specific helical peptide exerted potent protective effects against hepatic fibrosis by restoring autophagic flux in hepatocytes and HSCs. Together, stress-elevated TRIB3 expression promotes hepatic fibrosis by interacting with SQSTM1 and interfering with its functions in liver-parenchymal cells and activating HSCs. Targeting this interaction is a promising strategy for treating fibroproliferative liver diseases. Abbreviations: 3-MA: 3-methyladenine; AAV: adeno-associated virus; ACTA2/α-SMA: actin, alpha 2, smooth muscle, aorta; BDL: bile duct ligation; BECN1/Beclin 1: beclin 1, autophagy related; CHX: cycloheximide; CQ: chloroquine; Edu: 5-ethynyl-2-deoxyuridine; ESCRT: endosomal sorting complexes required for transport; HSC: hepatic stellate cell; ILV: intralumenal vesicle; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MVB: multivesicular body; PIK3C3: phosphatidylinositol 3-kinase, catalytic subunit type 3; PPI: protein-protein interaction; SQSTM1/p62: sequestosome 1; TAA: thioacetamide; TEM: transmission electron microscopy; TGFB1/TGFβ1: transforming growth factor, beta 1; TLR2: toll-like receptor 2; TRIB3: tribbles pseudokinase 3

Type 2 diabetes mellitus is a complex disease. Our previous study revealed that TRIB3 genetic variations were strongly associated with diabetic vascular complications, although TRIB3 regulation pathways remain poorly understood. We used two extreme treatment groups from a 2 × 2 factorial randomized controlled trial to identify a positive association, which was further validated in patients receiving cross treatment to test the effect of genetic polymorphisms among the different treatment groups. A gene-centric score (GS)-weighted model including the three associated genetic variations TRIB3 rs2295490, ATF6 rs12086247, and SMARCD3 rs58125572 was used. The results of the GS model indicated a 46% reduction in the risk of primary vascular complications in patients bearing more than two risk alleles [hazard ratio (HR) 0.54, 95% confidence interval (CI) 0.38–0.76, p < 0.001], following intensive glucose control treatment when compared with patients who received standard glucose control treatment. Furthermore, these patients benefited from active blood pressure-lowering treatment (HR 0.39, 95% CI 0.24–0.64, p < 0.001). However, no significant difference was observed between the two interventions in patients with fewer than two risk alleles (HR 1.09, 95% CI 0.86–1.39, p = 0.47). These results indicate that genetic variants in these three genes may be useful biomarkers for individualized drug therapy in diabetic patients.

The joint modeling of brain imaging information and genetic data is a promising research avenue to highlight the functional role of genes in determining the pathophysiological mechanisms of Alzheimer's disease (AD). However, since genome-wide association (GWA) studies are essentially limited to the exploration of statistical correlations between genetic variants and phenotype, the validation and interpretation of the findings are usually nontrivial and prone to false positives. To address this issue, in this work, we investigate the functional genetic mechanisms underlying brain atrophy in AD by studying the involvement of candidate variants in known genetic regulatory functions. This approach, here termed functional prioritization, aims at testing the sets of gene variants identified by high-dimensional multivariate statistical modeling with respect to known biological processes to introduce a biology-driven validation scheme. When applied to the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort, the functional prioritization allowed for identifying a link between tribbles pseudokinase 3 (

Rong-Jaan Lin,1,2 I-Jung Wu,1,2 Jo-Yu Hong,3 Bang-Hung Liu,4 Ruei-Yue Liang,4 Tein-Ming Yuan,5 Show-Mei Chuang4,6,7 1College of Life Sciences, National Chung Hsing University, 2Taichung Hospital, Ministry of Health and Welfare, 3Bachelor Program of Biotechnology, College of Agriculture and Natural Resources, 4Institute of Biomedical Sciences, College of Life Sciences, National Chung Hsing University, 5Surgery Department, Feng-Yuan Hospital, Ministry of Health and Welfare, 6Department of Nursing, Asia University, 7Department of Medical Research, China Medical University Hospital, Taichung, Taiwan Background: Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is one of the main pungent components of chili peppers and has been shown to exert various effects on numerous physiological processes. Recent studies have focused on the chemopreventive effects of capsaicin, which can combat growth in various human cancer cell systems. The tribbles-related protein 3 (TRIB3) is evolutionarily conserved from Drosophila to humans. In the latter, TRIB3 is a key determinant in numerous cellular processes, including apoptosis. Purpose: The aim of this study was to examine the importance of TRIB3 in the antitumor efficacy of capsaicin in human cancer cells, and further assess potential mechanism(s) underlying the capsaicin-induced upregulation of TRIB3.Methods: Human cancer cell lines were treated with capsaicin, then evaluated for levels of TRIB3 and molecules related to apoptosis or signaling pathways. The impact of TRIB3 on capsaicin-induced apoptosis was investigated using si-RNA or overexpression of TRIB3. Results: It is the first time to show that TRIB3 is targeted by capsaicin to promote apoptosis. Capsaicin promotes apoptotic cell death by upregulating TRIB3 expression in cancer cells. Overexpression of TRIB3 enhances capsaicin-induced apoptosis, and TRIB3 knockdown experiments demonstrate that the effect of capsaicin in apoptotic cell death is correlated with the induction of TRIB3 in cancer cells. Finally, enhancements in gene expression and protein stability are involved in the capsaicin-induced upregulation of TRIB3. Conclusion: Our results show that the capsaicin-induced upregulation of TRIB3 triggers apoptosis and thereby contributes to the suppression of cell growth in cancer cell lines. Keywords: capsaicin, TRIB3, apoptosis, cancer, Protein stability

Background: Glucose-induced insulin resistance is mediated by induction of the pseudokinase TRIB3, which requires glucose metabolism via the hexosamine biosynthetic pathway (HBP). We have also shown that the SP1 binding site in the TRIB3 promoter region is essential for glucose’s ability to induce TRIB3 in skeletal muscle. However, the mechanism by which glucose regulates TRIB3 gene expression remains unknown. Hypothesis: Since the HBP provides the substrate for O-GlcNAcylation, we hypothesize that glucose results in O-GlcNAcylation of SP1 and this modulates induction of TRIB3 causing insulin resistance. Results: When treated with 5mM or 25mM glucose, the induction of TRIB3 gene expression (P Conclusion: (1) Increased TRIB3 mRNA expression parallels with upregulated SP1 expression; (2) Glucose induction of TRIB3 mRNA and protein is eliminated when HBP flux and O-GlcNAcylation is disrupted by the inhibition of OGT; (3) SP1 sites are critical in the regulatory action of glucose on the TRIB3 promoter and can be modulated by SP1 O-GlcNAcylation. While further studies are underway, these data provide new insights regarding mechanisms causing glucose-induced insulin resistance, and TRIB3 and TRIB3 promoter regulation are attractive targets for prevention of glucose toxicity in diabetes. Disclosure X. Liu: None. M. Kang: None. W. Garvey: Advisory Panel; Self; Novo Nordisk Inc., Merck & Co., Inc.. Research Support; Self; Sanofi, Pfizer Inc., Novo Nordisk Inc., AstraZeneca, Merck & Co., Inc., Elcelyx Therapeutics, Inc., Lexicon Pharmaceuticals, Inc., Eisai Inc..

Endoplasmic reticulum (ER) homeostasis is crucial for proper β-cell function as evidenced by rare monogenic diabetic disorders, such as Wolfram syndrome, arising from genetic defects in key ER molecules. Wolfram syndrome stems from mutation of the ER transmembrane protein, Wolfram Syndrome 1 (WFS1), resulting in a recessive, progressive neurodegenerative disorder that first manifests as juvenile-onset diabetes mellitus (DM). While many WFS1 variants are associated with DM, the role of WFS1 in β-cell viability and function remains unclear. Our central hypothesis is that WFS1 regulates β-cell viability through downregulation of ER stress-responsive pro-apoptotic factors and β-cell function through modulation of key ER Ca2+ transporters. To test this hypothesis, we generated inducible β-cell models of WFS1 knockdown and overexpression using rat insulinoma cell lines to monitor β-cell function and β-cell death. We employed chemical and physiologic stimuli to model ER stress and monitored its downstream effects by real-time PCR, immunoblot and intracellular calcium mobilization. Our data indicate that β-cells depleted of WFS1 exhibit impaired insulin secretion and reduced insulin content. Additionally, knockdown of WFS1 is associated with decreased ER Ca2+, increased cytosolic Ca2+ and increased β-cell death. Conversely, increasing WFS1 expression in vitro increases insulin production and confers protection against ER stress-mediated β-cell death. Our data suggest that WFS1 may preserve β-cell viability by reducing the expression of pro-apoptotic factors CHOP and TRIB3. Future studies seek to clarify the mechanisms by which WFS1 protects β-cells against metabolic stressors and promotes insulin production. These studies will expand our understanding of the broader mechanisms by which ER dysfunction triggers β-cell pathology in more common forms of diabetes, and provide potential novel targets for intervention that center on preserving ER homeostasis. Disclosure D. Abreu: None. Z. Lavagnino: None. C.M. Brown: None. D.W. Piston: None. F. Urano: Research Support; Self; Eli Lilly and Company. Stock/Shareholder; Self; CytRx.

Methamphetamine (Meth) is a widely abused psychoactive drug that primarily damages the nervous system, notably causing dopaminergic neuronal apoptosis. CCAAT-enhancer binding protein (C/EBPβ) is a transcription factor and an important regulator of cell apoptosis and autophagy. Insulin-like growth factor binding protein (IGFBP5) is a proapoptotic factor that mediates Meth-induced neuronal apoptosis, and Trib3 (tribbles pseudokinase 3) is an endoplasmic reticulum (ER) stress-inducible gene involved in autophagic cell death through the mammalian target of rapamycin (mTOR) signaling pathway. To test the hypothesis that C/EBPβ is involved in Meth-induced IGFBP5-mediated neuronal apoptosis and Trib3-mediated neuronal autophagy, we measured the protein expression of C/EBPβ after Meth exposure and evaluated the effects of silencing C/EBPβ, IGFBP5, or Trib3 on Meth-induced apoptosis and autophagy in neuronal cells and in the rat striatum after intrastriatal Meth injection. We found that, at relatively high doses, Meth exposure increased C/EBPβ protein expression, which was accompanied by increased neuronal apoptosis and autophagy; triggered the IGFBP5-mediated, p53-up-regulated modulator of apoptosis (PUMA)-related mitochondrial apoptotic signaling pathway; and stimulated the Trib3-mediated ER stress signaling pathway through the Akt-mTOR signaling axis. We also found that autophagy is an early response to Meth-induced stress upstream of apoptosis and plays a detrimental role in Meth-induced neuronal cell death. These results suggest that Meth exposure induces C/EBPβ expression, which plays an essential role in the neuronal apoptosis and autophagy induced by relatively high doses of Meth; however, relatively low concentrations of Meth did not change the expression of C/EBPβ in vitro. Further studies are needed to elucidate the role of C/EBPβ in low-dose Meth-induced neurotoxicity.-Xu, X., Huang, E., Luo, B., Cai, D., Zhao, X., Luo, Q., Jin, Y., Chen, L., Wang, Q., Liu, C., Lin, Z., Xie, W.-B., Wang, H. Methamphetamine exposure triggers apoptosis and autophagy in neuronal cells by activating the C/EBPβ-related signaling pathway.

Background Chronic inflammation is one of the key processes in the development of metabolic dysfunction under obesity which represents a major risk for cardiovascular disease. The metabolic and immune responses to obesity affect many organs and particularly the adipose tissue where macrophages are key effector cells modulating inflammation through the signals received from adipocytes. The Tribbles (Trib) family of proteins has been described as major regulators of inflammation and energy metabolism. Specifically, Trib3 participates in a wide range of inflammatory and metabolic signalling pathways. We propose that Trib3 may modulate macrophage polarisation and therefore modulate the immune response to promote obesity. Methodology Trib3 full body knock out (Trib3KO) mice were used to study morphological changes in the adipose tissue. To investigate whether Trib3 regulates the polarisation state of macrophages, bone marrow derived macrophages (BMDMs) were isolated and polarised in vitro to further characterise their pro- or anti- inflammatory properties. Adipose tissue macrophages (CD11b+ATMs) were isolated from adipose tissue using magnetics beads and the expression of polarisation markers was evaluated by qPCR. Results Trib3 deficiency increased subcutaneous adipose tissue mass. Cell content showed that adipocytes were the same size compared to wild-type. However, adipocyte and macrophage numbers were increased in the Trib3KO mice. No significant differences in gene expression of classical polarisation markers were found in ATMs, however differential gene expression of proteins involved in macrophage function and phenotype was found in Trib3KO BMDMs compared to wild type results among the different polarisation states. Conclusion The results obtained in this pilot study suggest a role for Trib3 in macrophages due to expression differences measured in Trib3 deficient BMDMs, linked to a pro-inflammatory macrophage phenotype.

Background The development of potent non-toxic chemotherapeutic drugs against castration resistant prostate cancer (CRPC) remains a major challenge. Corosolic acid (CA), a natural triterpenoid, has anti-cancer activity with limited side effects. However, CA anti-prostate cancer activities and mechanisms, particularly in CRPC, are not clearly understood. In this study, we investigated CA anti-tumor ability against human CRPC and its mechanism of action. Methods The cell apoptosis and proliferation effects were evaluated via MTT detection, colony formation assay and flow cytometry. Western blot, gene transfection and immunofluorescence assay were applied to investigate related protein expression of Endoplasmic reticulum stress. A xenograft tumor model was established to investigate the inhibitory effect of CA on castration resistant prostate cancer in vivo. Results The results showed that CA inhibited cell growth and induced apoptosis in human prostate cancer cell (PCa) line PC-3 and DU145, as well as retarded tumor growth in a xenograft model, exerting a limited toxicity to normal cells and tissues. Importantly, CA activated endoplasmic reticulum (ER) stress-associated two pro-apoptotic signaling pathways, as evidenced by increased protein levels of typical ER stress markers including IRE-1/ASK1/JNK and PERK/eIF2α/ATF4/CHOP. IRE-1, PERK or CHOP knockdown partially attenuated CA cytotoxicity against PCa cells. Meanwhile, CHOP induced expression increased Tribbles 3 (TRIB3) level, which lead to AKT inactivation and PCa cell death. CHOP silencing resulted in PCa cells sensitive to CA-induced apoptosis. Conclusion Our data demonstrated, for the first time, that CA might represent a novel drug candidate for the development of an anti-CRPC therapy. Electronic supplementary material The online version of this article (10.1186/s13046-018-0889-x) contains supplementary material, which is available to authorized users.

TRIBBLES pseudokinases (TRIB1, TRIB2 and TRIB3) are important regulators of normal and malignant haemopoiesis. The relative abundance of each TRIBBLES family member may be important for distinct oncogenic or tumour suppressor functions. We map the expression profiles of TRIB1, TRIB2 and TRIB3 in human and murine haemopoietic stem, progenitor and mature cells and in human leukaemia datasets. Our data show that TRIB1-TRIB2 have an inverse expression relationship in normal haemopoiesis whereas TRIB1-TRIB3 have a positive correlation. We reveal that TRIB3 expression is high in the dormant haemopoietic stem cell (HSC) population, implicating a novel role for TRIB3 in stem cell quiescence. These analyses support a non-redundant role for each TRIBBLES member during normal haemopoietic differentiation. We show that TRIB1-TRIB2 display a significant negative correlation in myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML) subtypes, but not in acute lymphoid leukaemia (ALL). This inverse relationship is specific to certain subtypes of AML. A positive correlation exists in different leukaemia subtypes between TRIB1-TRIB3. The TRIB1-TRIB2 and TRIB1-TRIB3 correlations are consistent with a correlative relationship with C/EBP transcription factor family members. Our results have implications for the development of strategies to therapeutically target these genes in different types of leukaemia.

Tribbles pseudokinase 3 (TRIB3) belongs to the tribbles family of pseudokinases. In this article, we summarize several observation obtained by our laboratories supporting that TRIB3 plays a crucial role in the anti-cancer activity of cannabinoids (a novel family of potential anti-cancer agents derived from marijuana) and that TRIB3 genetic inactivation enhances cancer generation and progression.

The tribbles protein family, an evolutionarily conserved group of pseudokinases, have been shown to regulate multiple cellular events including those involved in normal and malignant haematopoiesis. The three mammalian Tribbles homologues, Trib1, Trib2 and Trib3 are characterized by conserved motifs, including a pseudokinase domain and a C-terminal E3 ligase-binding domain. In this review, we focus on the role of Trib (mammalian Tribbles homologues) proteins in mammalian haematopoiesis and leukaemia. The Trib proteins show divergent expression in haematopoietic cells, probably indicating cell-specific functions. The roles of the Trib proteins in oncogenesis are also varied and appear to be tissue-specific. Finally, we discuss the potential mechanisms by which the Trib proteins preferentially regulate these processes in multiple cell types.

Parkinson9s disease (PD) is characterized by the progressive loss of select neuronal populations, but the prodeath genes mediating the neurodegenerative processes remain to be fully elucidated. Trib3 (tribbles pseudokinase 3) is a stress-induced gene with proapoptotic activity that was previously described as highly activated at the transcriptional level in a 6-hydroxydopamine (6-OHDA) cellular model of PD. Here, we report that Trib3 immunostaining is elevated in dopaminergic neurons of the substantia nigra pars compacta (SNpc) of human PD patients. Trib3 protein is also upregulated in cellular models of PD, including neuronal PC12 cells and rat dopaminergic ventral midbrain neurons treated with 6-OHDA, 1-methyl-4-phenylpyridinium (MPP + ), or α-synuclein fibrils (αSYN). In the toxin models, Trib3 induction is substantially mediated by the transcription factors CHOP and ATF4. Trib3 overexpression is sufficient to promote neuronal death; conversely, Trib3 knockdown protects neuronal PC12 cells as well as ventral midbrain dopaminergic neurons from 6-OHDA, MPP + , or αSYN. Mechanism studies revealed that Trib3 physically interacts with Parkin, a prosurvival protein whose loss of function is associated with PD. Elevated Trib3 reduces Parkin expression in cultured cells; and in the SNpc of PD patients, Parkin levels are reduced in a subset of dopaminergic neurons expressing high levels of Trib3. Loss of Parkin at least partially mediates the prodeath actions of Trib3 in that Parkin knockdown in cellular PD models abolishes the protective effect of Trib3 downregulation. Together, these findings identify Trib3 and its regulatory pathways as potential targets to suppress the progression of neuron death and degeneration in PD. SIGNIFICANCE STATEMENT Parkinson9s disease (PD) is the most common neurodegenerative movement disorder. Current treatments ameliorate symptoms, but not the underlying neuronal death. Understanding the core neurodegenerative processes in PD is a prerequisite for identifying new therapeutic targets and, ultimately, curing this disease. Here, we describe a novel pathway involving the proapoptotic protein Trib3 in neuronal death associated with PD. These findings are supported by data from multiple cellular models of PD and by immunostaining of postmortem PD brains. Upstream, Trib3 is induced by the transcription factors ATF4 and CHOP; and downstream, Trib3 interferes with the PD-associated prosurvival protein Parkin to mediate death. These findings establish this new pathway as a potential and promising therapeutic target for treatment of PD.

Tribbles homolog 3 (TRIB3) is an intracellular kinase-like molecule that modifies cellular survival and metabolism. The present study aimed to investigate the function of TRIB3 regulation in the process of high glucose-induced apoptosis in endothelial cells, with the aim of identifying a novel intervention target for the prevention and treatment of diabetes mellitus. Human umbilical vein endothelial cells (HUVECs) grown in medium with various concentrations of glucose (5.5, 10, 20, 30 and 40 mmol/l) were assessed for mRNA expression of TRIB1, TRIB2 and TRIB3 using reverse transcription quantitative polymerase chain reaction. In addition, protein expression of TRIB3 was examined using western blot analysis. Immunofluorescence staining was performed in order to determine the distribution and localization of TRIB3 in HUVECs. Furthermore, cells grown in normal (5.5 mmol/l) or high glucose (HG; 30 mmol/l) medium were subjected to TRIB3 inhibition through small interfering (si)RNA knockdown. These cells were then examined in order to determine whether TRIB3 upregulation was associated with endothelial cell apoptosis. HUVECs treated with 30 and 40 mmol/l glucose for 48 h and 72 h showed significantly lower survival rates compared with those treated with normal glucose levels. In addition, slight but not significant increases in TRIB1 and TRIB2 mRNA expression were observed in HUVECs incubated with various concentrations of glucose for different durations. By contrast, TRIB3 mRNA expression was increased 7.2-fold following incubation with HG. Western blot analysis revealed a 5.44-fold increase in TRIB3 protein levels in cells grown in HG medium for 24 h compared with those grown in normal medium. Immunostaining assays revealed a markedly higher and well-defined nucleolar fluorescence intensity for TRIB3 expression at 24 h in HG medium compared with that of the control group. Furthermore, the apoptotic rate of HG-treated TRIB3 siRNA-transfected HUVECs was significantly increased compared with that of those transfected with control siRNA In conclusion, the results of the present study suggested that TRIB3 was associated with high glucose-induced HUVECs apoptosis, which was attenuated following transfection with TRIB3 siRNA.

High insulin/IGF is a biologic link between diabetes and cancers, but the underlying molecular mechanism remains unclear. Here we report a previously unrecognized tumour-promoting mechanism for stress protein TRB3, which mediates a reciprocal antagonism between autophagic and proteasomal degradation systems and connects insulin/IGF to malignant promotion. We find that several human cancers express higher TRB3 and phosphorylated insulin receptor substrate 1, which correlates negatively with patient's prognosis. TRB3 depletion protects against tumour-promoting actions of insulin/IGF and attenuates tumour initiation, growth and metastasis in mice. TRB3 interacts with autophagic receptor p62 and hinders p62 binding to LC3 and ubiquitinated substrates, which causes p62 deposition and suppresses autophagic/proteasomal degradation. Several tumour-promoting factors accumulate in cancer cells to support tumour metabolism, proliferation, invasion and metastasis. Interrupting TRB3/p62 interaction produces potent antitumour efficacies against tumour growth and metastasis. Our study opens possibility of targeting this interaction as a potential novel strategy against cancers with diabetes.

International audience; The joint modeling of brain imaging information and genetic data is a promising research avenue to highlight the functional role of genes in determining the pathophysiological mechanisms of Alzheimer’s disease (AD). However, since genome-wide association (GWA) studies are essentially limited to the exploration of statistical correlations between genetic variants and phenotype, the validation and interpretation of the findings are usually nontrivial and prone to false positives. To address this issue, in this work, we investigate the functional genetic mechanisms underlying brain atrophy in AD by studying the involvement of candidate variants in known genetic regulatory functions. This approach, here termed functional prioritization, aims at testing the sets of gene variants identified by high-dimensional multivariate statistical modeling with respect to known biological processes to introduce a biology-driven validation scheme. When applied to the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort, the functional prioritization allowed for identifying a link between tribbles pseudokinase 3 (TRIB3) and the stereotypical pattern of gray matter loss in AD, which was confirmed in an independent validation sample, and that provides evidence about the relation between this gene and known mechanisms of neurodegeneration.

L’ABTL0812 és un derivat lipídic amb activitat antitumoral llicenciat per la companyia biofarmacèutica Ability Pharmaceuticals. En estudis preliminars es va observar que l’ABTL0812 indueix citotoxicitat en un ampli espectre de cèl·lules tumorals humanes i una inhibició del creixement de tumors xenografts derivats de cèl·lules tumorals humanes, propietats que han motivat el seu desenvolupament pre-clínic. A l’actualitat, l’ABTL0812 es troba en Fase Clínica 2 en pacients amb càncer de pulmó escamós i d’endometri avançat (identificador ClinicalTrials.gov: NCT03366480). El nostre laboratori està implicat en caracteritzar el seu mecanisme d’acció antitumoral, utilitzant com a model les cèl·lules MiaPaca2 (adenocarcinoma pancreàtic) i A549 (adenocarcinoma de pulmó). Estudis previs realitzats al laboratori mostren que l’ABTL0812 activa els receptors PPAR i PPAR, que medien en la inducció de mort dependent d’autofàgia sense induir l’aparició de trets típicament apoptòtics. En aquesta Tesi Doctoral, mitjançant assajos de gen reporter luciferasa, quantificació de mRNA per RT-qPCR i assaig d’immunoblot, demostrem que l’activació dels receptors PPAR/ indueix l’activació transcripcional de la pseudoquinasa TRIB3. Una vegada sobre-expressada, TRIB3 uneix Akt i impedeix la seva activació per les quinases activadores PDK1 i mTORC2. Com a conseqüència d’això, s’inhibeix el complex mTORC1. Tanmateix, s’ha constatat que la inhibició del complex mTORC1 a les cèl·lules tumorals humanes MiaPaca2 i A549 no és suficient per induir una autofàgia robusta anàloga a l’observada per l’ABTL0812. Aquest fet va motivar l’estudi sobre si l’estrès reticular podia estar relacionat amb la sobre-expressió de TRIB3 i la mort cel·lular mediada per autofàgia induïdes per l’ABTL0812, tal com s’ha proposat per altres composts anti-tumorals com el tetrahidrocannabinol. En aquest treball hem observat que l’ABTL0812 indueix dilatació del reticle endoplasmàtic i la sobre-expressió dels marcadors d’estrès reticular BiP, ATF4 i CHOP. En conjunt, aquests resultats demostren la inducció d’estrès reticular per part de l’ABTL0812. El bloqueig farmacològic de l’estrès reticular mostra preliminarment que l’estrès reticular media en la citotoxicitat induïda per l’ABTL0812. D‘interès, s’ha posat a punt la quantificació dels nivells de mRNA plasmàtics dels marcador d’estrès reticular CHOP i TRIB3, tant en mostres de sang total com a PBMCs purificades, i s’ha constatat que augmenten en els pacients humans en resposta al tractament amb ABTL0812. En l’actualitat, aquests biomarcadors farmacodinàmics s’estan utilitzant a la Fase Clínica 2. L’anàlisi per espectrometria de masses de l’esfingolipidoma de cèl·lules tumorals ha permès observar que l’ABTL0812 indueix l’acumulació de dihidroceramides de cadena llarga, sense alterar els nivells de ceramides. Aquest esdeveniment s’explica pel fet que la incubació amb ABTL0812 resulta en la inhibició de l’enzim desaturasa-1 (Des-1) a la cèl·lula tumoral. Des-1 és l’últim enzim de la via de síntesi de novo de ceramides (catalitza el pas de dihidroceramides a ceramides) i la seva inhibició resulta en l’acumulació de dihidroceramides de cadena llarga, de manera anàloga a la mostrada per l’inhibidor específic de Des-1 GT11. D’interès, el tractament de les cèl·lules tumorals amb la dihidroceramida de cadena curta dideuterada d2c8DhCer (que provoca un augment dels nivells cel·lulars de dihidroceramides) resulta en la inducció d’estrès reticular, autofàgia i citotoxicitat a les cèl·lules tumorals MiaPaca2 i A549, tal com fa l’ABTL0812. L’estudi preliminar dels processos executors de la mort cel·lular induïda per l’ABTL0812 mostra que aquest compost altera la funció mitocondrial (depleció dràstica d’ATP cel·lular) i activa la via canònica de mitofàgia PINK1/parkina/ubiquitina. A més a més, l’ABTL0812 promou l’alliberació citosòlica de catepsines lisosomals, suggerint la inducció de permeabilització de membrana lisosomal (LMP) que explicaria la mort per necrosi observada a les cèl·lules tumorals. Finalment, aquesta Tesi proposa que l’ABTL0812 actuaria de forma paral·lela a través de dos eixos. Per un costat, activaria els receptors PPAR/, que indueixen la sobre-expressió de TRIB3 i la subseqüent inhibició d’Akt i del complex mTORC1. Per l’altre costat, l’ABTL0812 inhibiria l’enzim Des-1, provocant una acumulació de dihidroceramides de cadena llarga i l’activació d’estrès reticular. Ambdós eixos del mecanisme sinergitzen en l’activació d’autofàgia robusta i mort cel·lular, com demostra el tractament combinat amb l’inhibidor específic de mTORC1 Everolimus i l’inhibidor específic de Des-1 GT11. ABTL0812 is a polyunsaturated fatty acid derivative with antitumoral activity licensed by the biopharmaceutical company Ability Pharmaceuticals. ABTL0812 shows cytotoxicity in a wide panel of human tumor cell lines and induces tumor growth inhibition in human tumor cell-derived xenografts. This have encouraged its pre-clinical and clinical development. ABTL0812 recently started Phase 2 Clinical trials in patients with advanced endometrial cancer and squamous NSCLC, as a first line of treatment in combination with paclitaxel and carboplatin (ClinicalTrials.gov: NCT03366480). Our laboratory is involved in the characterization of ABTL0812’s antitumoral mechanism of action, using MiPaca2 (pancreatic adenocarcinoma) and A549 (lung adenocarcinoma) cell lines as models. Previous studies carried out in our laboratory uncovered that in cells ABTL0812 activates peroxisome proliferator-activated receptors PPAR/ receptors, inducing autophagy-mediated cancer cell death without activating apoptosis. Here, by using gene reporter luciferase assay, qRT-PCR mRNA quantification and immunoblot analysis, we show that ABTL0812 activates PPAR-mediated transcription of Tribbles 3 (TRIB3) pseudokinase. Over-expressed TRIB3 then binds and inhibits Akt, preventing its activation by PDK1 and mTORC2 upstream kinases, resulting in inhibition of the oncogenic Akt/mTORC1 axis. However, we found that mTORC1 inhibition is not enough to induce robust autophagy in MiaPaca2 and A549 cell lines, as it does ABTL0812. Thus, we investigated whether endoplasmic reticulum (ER) stress could also account for ABTL0812-induced TRIB3 overexpression, as it has been proposed for other antitumoral drugs such as tetrahydrocannabinol. We found ABTL0812 induces endoplasmic reticulum dilatation and over-expression of the endoplasmic reticulum stress markers BiP, ATF4 and CHOP (both mRNA and protein levels), indicating that ABTL0812 induces ER stress in these tumor cells. We also show preliminary pharmacological data suggesting that ER stress has a role in mediating ABTL0812-induced cytotoxicity. Remarkably, we have optimized a protocol for the quantification of TRIB3 and CHOP mRNAs (qRT-PCR) in blood and purified PBMCs from patients enrolled in Clinical Phase 2. We describe increased levels of CHOP and TRIB3 mRNAs in response to ABTL0812 treatment. Furthermore, we have proposed and optimized RT quantification of the ER stress genes TRIB3 and CHOP as reliable pharmacodynamic biomarkers for the ongoing Phase 2 Clinical trials. Given the role of sphingolipids in initiating the ER stress, we undertook a comprehensive mass-spec analysis of cellular sphingolipids to show that ABTL0812 induces long-chain dihydroceramides accumulation without affecting ceramide levels. In cells, dihydroceramides are converted into ceramides by the desaturase-1 (Des-1) enzyme. Enzymatic analysis demonstrated that ABTL0812 treatment results in inhibition of Des-1 activity in vitro and in cellular assays, provoking an accumulation of long-chain dihydroceramides, analogously to that induced by Des-1 specific inhibitor GT11. Interestingly, we show that treatment with the dideuterated short-chain dihydroceramide d2c8DhCer (which induces an increase of cellular dihydroceramides) results in endoplasmic reticulum stress, autophagy and cytotoxicity in MiaPaca2 and A549 cell lines. Preliminary characterization of ABTL0812-induced cell death shows that this compound alters mitochondrial function (induces a drastic depletion of cellular ATP) and it activates the canonic mitophagy pathway PINK1/parkin/ubiquitin. Furthermore, ABTL0812 induces cytosolic release lysosomal cathepsin B, suggesting a lysosomal membrane permeabilization (LMP) that would explain the necrotic cell death observed in tumor cells. Finally, this work proposes that ABTL0812 exerts its antitumoral activity acting simultaneously on two axes. On one hand, ABTL0812 activates PPAR/ receptors, which induce TRIB3 over-expression and the subsequent Akt and mTORC1 inhibition. On the other hand, ABTL0812 inhibits Des-1 enzyme, resulting in accumulation of long-chain dihydroceramides and the subsequent activation of ER stress. Both axes synergize to activate a robust autophagy which ultimately leads to lysosomal membrane permeabilization and necrosis. In agreement with this, we show that the inhibition of mTORC1 (Everolimus) synergizes with Des-1 inhibition (GT11) to promote autophagy and cytotoxicity.

Vildagliptin promotes beta cell survival by inhibiting cell apoptosis. It has been suggested that chronic ER (endoplasmic reticulum) stress triggers beta cell apoptosis. The objective of the study is to explore whether the pro-survival effect of vildagliptin is associated with attenuation of endoplasmic reticulum stress in islets of db/db mice.Vildagliptin was orally administered to db/db mice for 6 weeks, followed by evaluation of beta cell apoptosis by caspase3 activity and TUNEL staining method. Endoplasmic reticulum stress markers were determined with quantitative RT-PCR, immunohistochemistry and immunoblot analysis.After 6 weeks of treatment, vildagliptin treatment increased plasma active GLP-1 levels (22.63±1.19 vs. 11.69±0.44, P0.001), inhibited beta cell apoptosis as demonstrated by lower amounts of TUNEL staining nuclei (0.37±0.03 vs. 0.55±0.03, P0.01) as well as decreased caspase3 activity (1.48±0.11 vs. 2.67±0.13, P0.01) in islets of diabetic mice compared with untreated diabetic group. Further, vildagliptin treatment down-regulated several genes related to endoplasmic reticulum stress including TRIB3 (tribbles homolog 3) (15.9±0.4 vs. 33.3±1.7, ×10⁻³, P0.001), ATF-4(activating transcription factor 4) (0.83±0.06 vs. 1.42±0.02, P0.001) and CHOP(C/EBP homologous protein) (0.07±0.01 vs. 0.16±0.01, P0.001).Vildagliptin promoted beta cell survival in db/db mice in association with down-regulating markers of endoplasmic reticulum stress including TRIB3, ATF-4 as well as CHOP.

Abstract The Helicobacter pylori vacuolating cytotoxin (VacA) can promote progressive vacuolation and gastric injury and may be associated with human gastric cancer. Increasing evidence indicates that autophagy is involved in the cell death induced by VacA, but the specific mechanisms need to be further elucidated. We show here that VacA could induce autophagy and increase cell death in human gastric cancer cell lines. Further investigations revealed that inhibition of autophagy could decrease the VacA-induced cell death in AGS cells. Furthermore, numerous dilated endoplasmic reticula (ER) were observed, and the phosphorylation of a subunit of eukaryotic translation initiation factor 2 subunit 1 also increased in the VacA-treated AGS cells, while repression of ER stress could reduce autophagy and cell death through knockdown of activating transcription factor 4 and DNA-damage-inducible transcript 3. In addition, the expression of pseudokinase tribbles homolog 3 (TRIB3) upon ER stress was triggered by VacA, and knockdown of TRIB3 could also decrease VacA-induced cell death. Finally, inhibition of autophagy could decrease VacA s1m1 -induced cell death and apoptosis, and apoptosis inhibitor Z-VAD had no significant effect on autophagy induced by VacA s1m1 . Thus, these results suggested that VacA causes autophagic cell death via ER stress in gastric epithelial cells.

Mammals must be able to endure periods of limited food availability, and the liver plays a central role in the adaptation to nutritional stresses. TRIB3 (Tribbles homolog 3) is a cellular stress-inducible gene with a liver-centric expression pattern and it has been implicated in stress response regulation and metabolic control . In the current article, we study the involvement of TRIB3 in responses to nutrient deficiencies, including fasting for up to 48 h in mice. We show that hepatic expression of Trib3 is increased after 48 h of fasting and mice with a targeted deletion of the Trib3 gene present elevated hepatic triglyceride content and liver weight at 48 h, along with an upregulation of lipid utilization genes in the liver. Further, hepatic and serum levels of the metabolic stress hormone FGF21 are considerably increased in 48-h-fasted Trib3 knockout mice compared to wild type. Trib3 deficiency also leads to elevated FGF21 levels in the mouse liver during essential amino acid deficiency and in cultured mouse embryonic fibroblasts during glucose starvation. Reporter assays reveal that TRIB3 regulates FGF21 by inhibiting ATF4-mediated, C/EBP–ATF site-dependent activation of Fgf21 transcription. Based on chromatin immunoprecipitation from mouse liver, the binding of TRIB3 and ATF4 , a transcription factor known to physically interact with TRIB3, is significantly increased at the Fgf21 promoter following 48 h of fasting. Thus, under nutrient-limiting conditions that stimulate ATF4 activity, TRIB3 is implicated in the regulation of metabolic adaptation by restraining the transcription of Fgf21.

Background/aim Triple-negative breast cancer (TNBC) is characterized by the absence of hormone receptors (estrogen, progesterone and human epidermal growth factor receptor-2) and a relatively poor prognosis due to inefficacy of hormone receptor-based chemotherapies. It is imperative that we continue to explore natural products with potential to impede growth and metastasis of TNBC. In this study, we screened over 1,000 natural products for capacity to induce cell death in TNBC (MDA-MB -231) cells. Materials and methods Frankincense (Boswellia serrata extract (BSE)) and 3-O-Acetyl-β-boswellic acid (3-OAβBA) were relatively potent, findings that corroborate the body of existing literature. The effects of BSE and 3-OAβBA on genetic parameters in MDA-MB-231 cells were evaluated by examining whole-transcriptomic influence on mRNAs, long intergenic non-coding RNA transcripts (lincRNA) and non-coding miRNAs. Results Bio-statistical analysis demarcates the primary effect of both BSE/3-OAβBA on the up-regulation of PERK (protein kinase RNA-like endoplasmic reticulum kinase)- endoplasmic reticulum (ER)/unfolded protein response (UPR) pathways that are closely tied to activated programmed cell death (APCD). Global profiling confirms concomitant effects of BSE/3-OAβBA on upwardly expressed ER/URP APCD key components PERK (EIF2AK3), XBP1, C/EBP homologous protein transcription factor (CHOP), ATF3 and DDIT3,4/DNA-damage-inducible transcript 3,4 (GADD34). Further, BSE and/or 3-OAβBA significantly down-regulated oncogenes (OG) which, heretofore, lack functional pathway mapping, but are capable of driving epithelial-mesenchymal transition (EMT), cell survival, proliferation, metastasis and drug resistance. Among these are cell migration-inducing protein hyaluronan binding (CEMIP) [-7.22]; transglutaminase 2 [-4.96], SRY box 9 (SOX9) [-4.09], inhibitor of DNA binding 1, dominant negative helix-loop-helix protein (ID1) [-6.56]; and endothelin 1 (EDN1, [-5.06]). Likewise, in the opposite manner, BSE and/or 3-OAβBA induced the robust overexpression of tumor suppressor genes (TSGs), including: glutathione-depleting ChaC glutathione-specific gamma-glutamylcyclotransferase 1 (CHAC1) [+21.67]; the mTOR inhibitors - sestrin 2 (SESN2) [+16.4] Tribbles homolog 3 (TRIB3) [+6.2], homocysteine-inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1 (HERPUD1) [+12.01]; and cystathionine gamma-lyase (CTH) [+11.12]. Conclusion The anti-cancer effects of the historically used frankincense sap (BSE) appear to involve major impact on the ER/UPR response, concomitant to effecting multiple targets counter to the growth, proliferation and metastasis of TNBC cancer cells. The microarray data are available at Expression Omnibus GEO Series accession number GSE102891.

Osteogenic differentiation in human bone marrow-derived mesenchymal stem cells (hBMSCs) is regulated by various factors, including bone morphogenetic proteins (BMPs), Notch, growth hormones and mitogen-activated protein kinases (MAPKs). Tribbles homolog 3 (TRIB3), a pseudokinase, plays an important role in cancer cells and adipocytes. However, TRIB3 function in osteogenic differentiation is unknown, although it is involved in regulating signaling pathways associated with osteogenic differentiation. Here, we found that TRIB3 was highly expressed during osteogenic differentiation in hBMSCs. Inhibition of focal adhesion kinase (FAK) or phosphatidylinositol 3-kinase (PI3K) resulted in a significant decrease in TRIB3 expression, and expression of TRIB3 was restored by increasing insulin-like growth factor-1 (IGF-1) via activating phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling. TRIB3 knock-down enhanced proliferation and decreased osteogenic differentiation at the middle stage of differentiation, and these effects were reversed by inhibiting the activation of extracellular signal-regulated kinase (ERK)-1/2. In conclusion, TRIB3 plays an important role in proliferation and osteogenic differentiation by regulating ERK1/2 activity at the middle stage of differentiation, and expression of TRIB3 is regulated by FAK in a PI3K/AKT-dependent manner.

Methamphetamine (METH) is an illegal and widely abused psychoactive stimulant. METH exposure causes detrimental effects on multiple organ systems, primarily the nervous system, especially dopaminergic pathways, in both laboratory animals and humans. In this study, we hypothesized that Nuclear protein 1 (Nupr1/com1/p8) is involved in METH-induced neuronal apoptosis and autophagy through endoplasmic reticulum (ER) stress signaling pathway. To test this hypothesis, we measured the expression levels of Nupr1, ER stress protein markers CHOP and Trib3, apoptosis-related protein markers cleaved-caspase3 and PARP, as well as autophagy-related protein markers LC3 and Beclin-1 in brain tissues of adult male Sprague-Dawley (SD) rats, rat primary cultured neurons and the rat adrenal pheochromocytoma cells (PC12 cells) after METH exposure. We also determined the effects of METH exposure on the expression of these proteins after silencing Nupr1, CHOP, or Trib3 expression with synthetic small hairpin RNA (shRNA) or siRNA in vitro, and after silencing Nupr1 in the striatum of rats by injecting lentivirus containing shRNA sequence targeting Nupr1 gene to rat striatum. The results showed that METH exposure increased Nupr1 expression that was accompanied with increased expression of ER stress protein markers CHOP and Trib3, and also led to apoptosis and autophagy in rat primary neurons and in PC12 cells after 24 h exposure (3.0 mM), and in the prefrontal cortex and striatum of rats after repeated intraperitoneal injections (15 mg/kg × 8 injections at 12 h intervals). Silencing of Nupr1 expression partly reduced METH-induced apoptosis and autophagy in vitro and in vivo. These results suggest that Nupr1 plays an essential role in METH-caused neuronal apoptosis and autophagy at relatively higher doses and may be a potential therapeutic target in high-dose METH-induced neurotoxicity.

Tribbles homolog 3 (TRIB3) is a mammalian gene that is upregulated in response to several types of cell death-inducing cellular stress. The TRIB3 protein is a pseudokinase, a protein kinase-like scaffold with impaired catalytic activity. However, research has revealed it to be prolific at forming protein- protein interactions. By binding to and regulating the activity of several key proteins, including the protein kinase Akt and transcription factors ATF4, CHOP and NF-κB, TRIB3 is at a junction of several signaling pathways. This review begins by providing insights into the characteristic protein structure and gene expression regulation mechanisms of TRIB3. Further, the diverse reported molecular roles of TRIB3 as a regulator of cell death, stress responses, inflammation, cell differentiation, protein degradation and other processes are discussed. Special attention is devoted to the involvement of TRIB3 in the pathogenesis of cancer and type 2 diabetes, two fields where TRIB3 has generated particular interest, as well as considerable debate, from a biomedical standpoint. Throughout, emphasis is placed on results obtained from animal models with altered TRIB3 expression (Trib3 knockout or overexpression mice), in order to provide insight into the contributions of TRIB3 to physiology and disease at the organism level.

Pseudokinase tribbles (Trib) family, Trib1 and Trib2, but not Trib3, act as oncogene to drive acute leukemia by destabilizing the myeloid transcription factor CCAAT/enhancer-binding protein α (C/EBPα) and inhibiting myeloid differentiation. A recent study identifies pseudokinase TRIB3 as an important factor in acute promyelocytic leukemia (APL) progression and therapy resistance. Targeting TRIB3 may provide a novel therapeutic approach for APL.

The t(15;17) translocation generates a PML-RARα fusion protein causative for acute promyelocytic leukemia (APL). Li et al. now identify the pseudokinase stress protein TRIB3 as an important factor in APL disease progression and therapy resistance. Targeting the interaction of TRIB3 and PML-RARα using peptide technology provides a novel therapeutic approach.

Synchrotron microbeam radiation therapy (MRT) relies on the spatial fractionation of a synchrotron beam into parallel micron-wide beams allowing deposition of hectogray doses. MRT controls the intracranial tumor growth in rodent models while sparing normal brain tissues. Our aim was to identify the early biological processes underlying the differential effect of MRT on tumor and normal brain tissues. The expression of 28,000 transcripts was tested by microarray 6 hr after unidirectional MRT (400 Gy, 50 µm-wide microbeams, 200 µm spacing). The specific response of tumor tissues to MRT consisted in the significant transcriptomic modulation of 431 probesets (316 genes). Among them, 30 were not detected in normal brain tissues, neither before nor after MRT. Areg, Trib3 and Nppb were down-regulated, whereas all others were up-regulated. Twenty-two had similar expression profiles during the 2 weeks observed after MRT, including Ccnb1, Cdc20, Pttg1 and Plk1 related to the mitotic role of the Polo-like kinase (Plk) pathway. The up-regulation of Areg expression may indicate the emergence of survival processes in tumor cells triggered by the irradiation; while the modulation of the "mitotic role of Plk1" pathway, which relates to cytokinetic features of the tumor observed histologically after MRT, may partially explain the control of tumor growth by MRT. The identification of these tumor-specific responses permit to consider new strategies that might potentiate the antitumoral effect of MRT.

In our previous in vitro study of the toxicity on silver nanoparticles (AgNPs), we observed a dramatically higher sensitivity of Jurkat T cells to AgNPs than to Ag ions, and DNA damage and apoptosis were found to be involved in that toxicity. In this study, to understand underlying mechanism of different sensitivity of Jurket T cells to AgNPs and Ag ions, mRNA microarray and micro RNA microarray were concomitantly conducted on AgNPs and Ag ions exposed Jurkat T cells. Surprisingly only a small number of genes were differentially expressed by exposure to each of the silver (15 altered mRNA by AgNPs exposure, whereas 4 altered mRNA by Ag ions exposure, as determined 1.5-fold change as the cut-off value). miRNA microarray revealed that the expression of 63 miRNAs was altered by AgNPs exposure, whereas that of 32 miRNAs was altered by Ag ions exposure. An integrated analysis of mRNA and miRNA expression revealed that the expression of hsa-miR-219-5p, was negatively correlated with the expression of metallothionein 1F (MT1F) and tribbles homolog 3 (TRIB3), in cells exposed to AgNPs; whereas, the expression of hsa-miR-654-3p was negatively correlated with the expression of mRNA, endonuclease G-like 1 (EDGL1) in cells exposed to Ag ions. Network analysis were further conducted on mRNA-miRNA pairs, which revealed that miR-219-5p-MT1F and -TRIB3 pairs by AgNPs are being involved in various cellular processes, such as, oxidative stress, cell cycle and apoptosis, whereas, miR-654-3p and ENDOGL1 pair by Ag ions generated a much simpler network. The putative target genes of AgNPs-induced miR-504, miR-33 and miR-302 identified by Tarbase 6.0 are also found to be involved in DNA damage and apoptosis. These results collectively suggest that distinct epigenetic regulation may be an underlying mechanism of different sensitivity of Jurkat T cells to AgNPs and Ag ion. Further identification of putative target genes of DE miRNA by AgNPs and Ag ions may provide additional clues for the mechanism of differential toxicity. Overall results suggest that epigenetic mechanism is involved in toxicity of AgNPs and Ag ions in Jurkat T cells.