Wild-type IDH1 maintains NSCLC stemness and chemoresistance through activation of the serine biosynthetic pathway.

Tumor-initiating cells (TICs) reprogram their metabolic features to meet their bioenergetic, biosynthetic, and redox demands. Our previous study established a role for wild-type isocitrate dehydrogenase 1 (IDH1WT) as a potential diagnostic and prognostic biomarker for non-small cell lung cancer (NSCLC), but how IDH1WT modulates NSCLC progression remains elusive. Here, we report that IDH1WT activates serine biosynthesis by enhancing the expression of phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase 1 (PSAT1), the first and second enzymes of de novo serine synthetic pathway. Augmented serine synthesis leads to GSH/ROS imbalance and supports pyrimidine biosynthesis, maintaining tumor initiation capacity and enhancing gemcitabine chemoresistance. Mechanistically, we identify that IDH1WT interacts with and stabilizes PHGDH and fragile X-related protein-1 (FXR1) by impeding their association with the E3 ubiquitin ligase parkin by coimmunoprecipitation assay and proximity ligation assay. Subsequently, stabilized FXR1 supports PSAT1 mRNA stability and translation, as determined by actinomycin D chase experiment and in vitro translation assay. Disrupting IDH1WT-PHGDH and IDH1WT-FXR1 interactions synergistically reduces NSCLC stemness and sensitizes NSCLC cells to gemcitabine and serine/glycine-depleted diet therapy in lung cancer xenograft models. Collectively, our findings offer insights into the role of IDH1WT in serine metabolism, highlighting IDH1WT as a potential therapeutic target for eradicating TICs and overcoming gemcitabine chemoresistance in NSCLC.

ID1 expressing macrophages support cancer cell stemness and limit CD8+ T cell infiltration in colorectal cancer.

Elimination of cancer stem cells (CSCs) and reinvigoration of antitumor immunity remain unmet challenges for cancer therapy. Tumor-associated macrophages (TAMs) constitute the prominant population of immune cells in tumor tissues, contributing to the formation of CSC niches and a suppressive immune microenvironment. Here, we report that high expression of inhibitor of differentiation 1 (ID1) in TAMs correlates with poor outcome in patients with colorectal cancer (CRC). ID1 expressing macrophages maintain cancer stemness and impede CD8+ T cell infiltration. Mechanistically, ID1 interacts with STAT1 to induce its cytoplasmic distribution and inhibits STAT1-mediated SerpinB2 and CCL4 transcription, two secretory factors responsible for cancer stemness inhibition and CD8+ T cell recruitment. Reducing ID1 expression ameliorates CRC progression and enhances tumor sensitivity to immunotherapy and chemotherapy. Collectively, our study highlights the pivotal role of ID1 in controlling the protumor phenotype of TAMs and paves the way for therapeutic targeting of ID1 in CRC.

Mesaconine alleviates doxorubicin-triggered cardiotoxicity and heart failure by activating PINK1-dependent cardiac mitophagy.

Aberrant mitophagy has been identified as a driver for energy metabolism disorder in most cardiac pathological processes. However, finding effective targeted agents and uncovering their precise modulatory mechanisms remain unconquered. Fuzi, the lateral roots of Aconitum carmichaelii, shows unique efficacy in reviving Yang for resuscitation, which has been widely used in clinics. As a main cardiotonic component of Fuzi, mesaconine has been proven effective in various cardiomyopathy models. Here, we aimed to define a previously unrevealed cardioprotective mechanism of mesaconine-mediated restoration of obstructive mitophagy. The functional implications of mesaconine were evaluated in doxorubicin (DOX)-induced heart failure models. DOX-treated mice showed characteristic cardiac dysfunction, ectopic myocardial energy disorder, and impaired mitophagy in cardiomyocytes, which could be remarkably reversed by mesaconine. The cardioprotective effect of mesaconine was primarily attributed to its ability to promote the restoration of mitophagy in cardiomyocytes, as evidenced by elevated expression of PINK1, a key mediator of mitophagy induction. Silencing PINK1 or deactivating mitophagy could completely abolish the protective effects of mesaconine. Together, our findings suggest that the cardioprotective effects of mesaconine appear to be dependent on the activation of PINK1-induced mitophagy and that mesaconine may constitute a promising therapeutic agent for the treatment of heart failure.

TRIB3 reduces CD8+ T cell infiltration and induces immune evasion by repressing the STAT1-CXCL10 axis in colorectal cancer.

High CD8+ T cell infiltration in colorectal cancer (CRC) should suggest a favorable prognosis and a satisfactory response to immunotherapy; however, the vast majority of patients with CRC do not benefit from immunotherapy due to poor T cell infiltration. Therefore, a better understanding of the mechanisms for T cell exclusion from CRC tumors is needed. Tribbles homolog 3 (TRIB3) has been implicated as an oncoprotein, but its role in regulating antitumor immune responses has not been defined. Here, we demonstrated that TRIB3 inhibits CD8+ T cell infiltration in various CRC mouse models. We showed that TRIB3 was acetylated by acetyltransferase P300, which inhibited ubiquitination and subsequent proteasomal degradation of TRIB3. Ectopically expressed TRIB3 inhibited signal transducer and activator of transcription 1 (STAT1) activation and STAT1-mediated CXCL10 transcription by enhancing the epidermal growth factor receptor signaling pathway, causing a reduction in tumor-infiltrating T cells. Genetic ablation of Trib3 or pharmacological acceleration of TRIB3 degradation with a P300 inhibitor increased T cell recruitment and sensitized CRCs to immune checkpoint blockade therapy. These findings identified TRIB3 as a negative modulator of CD8+ T cell infiltration in CRCs, highlighting a potential therapeutic target for treating immunologically "cold" CRCs.

Crosstalk between ferroptosis and stress-Implications in cancer therapeutic responses.

Ferroptosis is a newly discovered form of cell death that is characterized by the accumulation of iron-dependent lipid peroxidation. Research on ferroptosis has seen exponential growth over the past few years. Tumor cells are strongly dependent on iron for their growth, which makes them develop mechanisms to increase iron uptake and inhibit iron output, thereby completing iron accumulation. Ferroptosis can be induced or inhibited by various stresses through multiple mechanisms, making it stands at the crossroads of stresses related cancer cell fate determination. In this review, we give a brief summary of ferroptosis hallmarks and provide a systematic analysis of the current molecular mechanisms and regulatory networks of diverse stress conditions on ferroptosis. We also discuss the relationships between ferroptosis and cancer therapy responses to further understand potential targets and therapeutic strategies for cancer treatment.

The chemokine CCL1 triggers an AMFR-SPRY1 pathway that promotes differentiation of lung fibroblasts into myofibroblasts and drives pulmonary fibrosis.

Recruitment of immune cells to the site of inflammation by the chemokine CCL1 is important in the pathology of inflammatory diseases. Here, we examined the role of CCL1 in pulmonary fibrosis (PF). Bronchoalveolar lavage fluid from PF mouse models contained high amounts of CCL1, as did lung biopsies from PF patients. Immunofluorescence analyses revealed that alveolar macrophages and CD4+ T cells were major producers of CCL1 and targeted deletion of Ccl1 in these cells blunted pathology. Deletion of the CCL1 receptor Ccr8 in fibroblasts limited migration, but not activation, in response to CCL1. Mass spectrometry analyses of CCL1 complexes identified AMFR as a CCL1 receptor, and deletion of Amfr impaired fibroblast activation. Mechanistically, CCL1 binding triggered ubiquitination of the ERK inhibitor Spry1 by AMFR, thus activating Ras-mediated profibrotic protein synthesis. Antibody blockade of CCL1 ameliorated PF pathology, supporting the therapeutic potential of targeting this pathway for treating fibroproliferative lung diseases.

Autophagic Flux Detection: Significance and Methods Involved.

Macroautophagy is an important biological process in eukaryotic cells by which longevity proteins, misfolded proteins, and damaged organelles are degraded. The autophagy process consists of three key steps: (1) the formation of autophagosomes; (2) the fusion of the autophagosomes with lysosomes; and (3) the degradation of the contents of autolysosomes. If any of the three steps is impaired, autophagy will not be able to complete its biological function. Dysfunctional or blocked autophagy is closely involved in the pathogenesis of a variety of diseases. The accurate determination of the autophagy activity in vivo and in vitro has become a challenge in the field of autophagy research. At present, the most widely used detection method to determine autophagy activity in mammalian cells is to quantify LC3B in the cells by Western blot, or to observe the formation and changes of autophagosomes and autolysosomes by immunofluorescence and electron microscopy. However, ignoring the dynamic characteristics of autophagy and only evaluating the number of autophagosomes or the presence of LC3B cannot completely reflect the activation or a blockage of the autophagy system, and objectively analyze its real role in the occurrence and development of a disease. For example, the accumulation of autophagosomes and autolysosomes can occur through an increase in substrate to be degraded after the activation of autophagy, or it may be caused by the partial obstruction or blockage of autophagy. In this chapter, new and familiar ways to detect the autophagic flux are methodically summarized to provide researchers with a multi-angled viewpoint.

Faciogenital Dysplasia 5 supports cancer stem cell traits in basal-like breast cancer by enhancing EGFR stability.

Most basal-like breast cancers (BLBCs) are triple-negative breast cancers (TNBCs), which have the worst prognosis and distant metastasis-free survival among breast cancer subtypes. Now, no targeted therapies are available for patients with BLBC due to the lack of reliable and effective molecular targets. Here, we performed the BLBC tissue microarray-based immunohistochemical analysis and showed that Faciogenital Dysplasia 5 (FGD5) abundance is associated with poor prognosis in BLBCs. FGD5 deletion decreased the proliferation, invasion, and tumorsphere formation capacity of BLBC cells. Furthermore, genetic inhibition of Fgd5 in mouse mammary epithelial cells attenuated BLBC initiation and progression by reducing the self-renewal ability of tumor-initiating cells. In addition, FGD5 abundance was positively correlated with the abundance of epidermal growth factor receptor (EGFR) in BLBCs. FGD5 ablation decreased EGFR abundance by reducing EGFR stability in TNBC cells in 2D and 3D culture conditions. Mechanistically, FGD5 binds to EGFR and interferes with basal EGFR ubiquitination and degradation induced by the E3 ligase ITCH. Impaired EGFR degradation caused BLBC cell proliferation and promoted invasive properties and self-renewal. To verify the role of the FGD5-EGFR interaction in the regulation of EGFR stability, we screened a cell-penetrating α-helical peptide PER3 binding with FGD5 to disrupt the interaction. Treatment of BLBC patient-derived xenograft-bearing mice with the peptide PER3 disrupting the FGD5-EGFR interaction either with or without chemotherapy reduced BLBC progression. Our study identified FGD5 as a positive modulator of tumor-initiating cells and suggests a potential therapeutic option for the BLBC subtype of breast cancer.

TRIB3 promotes MYC-associated lymphoma development through suppression of UBE3B-mediated MYC degradation.

The transcription factor MYC is deregulated in almost all human cancers, especially in aggressive lymphomas, through chromosomal translocation, amplification, and transcription hyperactivation. Here, we report that high expression of tribbles homologue 3 (TRIB3) positively correlates with elevated MYC expression in lymphoma specimens; TRIB3 deletion attenuates the initiation and progression of MYC-driven lymphoma by reducing MYC expression. Mechanistically, TRIB3 interacts with MYC to suppress E3 ubiquitin ligase UBE3B-mediated MYC ubiquitination and degradation, which enhances MYC transcriptional activity, causing high proliferation and self-renewal of lymphoma cells. Use of a peptide to disturb the TRIB3-MYC interaction together with doxorubicin reduces the tumor burden in MycEµ mice and patient-derived xenografts. The pathophysiological relevance of UBE3B, TRIB3 and MYC is further demonstrated in human lymphoma. Our study highlights a key mechanism for controlling MYC expression and a potential therapeutic option for treating lymphomas with high TRIB3-MYC expression.

TRIB3-EGFR interaction promotes lung cancer progression and defines a therapeutic target.

High expression or aberrant activation of epidermal growth factor receptor (EGFR) is related to tumor progression and therapy resistance across cancer types, including non-small cell lung cancer (NSCLC). EGFR tyrosine kinase inhibitors (TKIs) are first-line therapy for NSCLC. However, patients eventually deteriorate after inevitable acquisition of EGFR TKI-resistant mutations, highlighting the need for therapeutics with alternative mechanisms of action. Here, we report that the elevated tribbles pseudokinase 3 (TRIB3) is positively associated with EGFR stability and NSCLC progression. TRIB3 interacts with EGFR and recruits PKCα to induce a Thr654 phosphorylation and WWP1-induced Lys689 ubiquitination in the EGFR juxtamembrane region, which enhances EGFR recycling, stability, downstream activity, and NSCLC stemness. Disturbing the TRIB3-EGFR interaction with a stapled peptide attenuates NSCLC progression by accelerating EGFR degradation and sensitizes NSCLC cells to chemotherapeutic agents. These findings indicate that targeting EGFR degradation is a previously unappreciated therapeutic option in EGFR-related NSCLC.

Disruption of the EGFR-SQSTM1 interaction by a stapled peptide suppresses lung cancer via activating autophagy and inhibiting EGFR signaling.

Despite the success of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in the treatment of non-small cell lung cancer (NSCLC) harboring EGFR-activating mutations, intrinsic or acquired resistance remains the major obstacle to long-term disease remission. Defective autophagy has been reported as an EGFR-TKI resistance mechanism. However, how EGFR regulate autophagic flux are still not fully understood. Here we found that EGFR-stimulated phosphorylation of SQSTM1 at tyrosine 433 induces dimerization of its UBA domain, which disturbs the sequestration function of SQSTM1 and causes autophagic flux blocking. SAH-EJ2, a staple optimized EGFR-derived peptide, showed enhanced in vitro and in vivo antitumor activity against NSCLC than the prototype regardless of EGFR mutation status. Mechanistically, SAH-EJ2 disrupts the EGFR-SQSTM1 interaction and protects against EGFR-induced SQSTM1 phosphorylation, which hinders the dimerization of the SQSTM1 UBA domains and restores SQSTM1 cargo function. Moreover, SAH-EJ2 suppresses EGFR activity by blocking its dimerization and reducing its protein stability, which reciprocally activates the core autophagy machinery. Our observations reveal that disturbing the EGFR-SQSTM1 interaction by SAH-EJ2 confers a potential strategy in the treatment of NSCLC through suppressing EGFR signalling and activating autophagy simultaneously.

Disrupting the TRIB3-SQSTM1 interaction reduces liver fibrosis by restoring autophagy and suppressing exosome-mediated HSC activation.

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/TGFß1: transforming growth factor, beta 1; TLR2: toll-like receptor 2; TRIB3: tribbles pseudokinase 3.

EGFR enhances the stemness and progression of oral cancer through inhibiting autophagic degradation of SOX2.

Epidermal growth factor receptor (EGFR) is highly expressed in head and neck squamous cell carcinoma (HNSCC) and correlates with poor prognosis. EGFR has been demonstrated to be associated with cancer stem cell traits in HNSCC. However, the underlying molecular mechanism is far from elucidated. Here, SOX2, one of the most important stem cell markers, was identified as a binding partner and substrate of EGFR. EGFR signaling inhibition decreases SOX2 expression by promoting its autophagic degradation. Mechanistically, EGFR activation induces SOX2 phosphorylation at the Y277 site and reduces its ubiquitination, which inhibits its association with p62 and subsequent autophagic degradation. Gefitinib, an EGFR tyrosine kinase inhibitor, shows in vitro and in vivo protective effects against oral cancer cells that can be reversed through autophagy inhibition. Our study suggests that EGFR plays an important role in the development of cancer stem cells by stabilizing SOX2. Targeting EGFR in combination with conventional chemotherapy might be a promising strategy for the treatment of HNSCC through elimination of cancer stem cells.

TRIB3 supports breast cancer stemness by suppressing FOXO1 degradation and enhancing SOX2 transcription.

The existence of breast cancer stem cells (BCSCs) is a major reason underlying cancer metastasis and recurrence after chemotherapy and radiotherapy. Targeting BCSCs may ameliorate breast cancer relapse and therapy resistance. Here we report that expression of the pseudokinase Tribble 3 (TRIB3) positively associates with breast cancer stemness and progression. Elevated TRIB3 expression supports BCSCs by interacting with AKT to interfere with the FOXO1-AKT interaction and suppress FOXO1 phosphorylation, ubiquitination, and degradation by E3 ligases SKP2 and NEDD4L. The accumulated FOXO1 promotes transcriptional expression of SOX2, a transcriptional factor for cancer stemness, which in turn, activates FOXO1 transcription and forms a positive regulatory loop. Disturbing the TRIB3-AKT interaction suppresses BCSCs by accelerating FOXO1 degradation and reducing SOX2 expression in mouse models of breast cancer. Our study provides insights into breast cancer development and confers a potential therapeutic strategy against TRIB3-overexpressed breast cancer.

Targeting Extracellular Heat Shock Protein 70 Ameliorates Doxorubicin-Induced Heart Failure Through Resolution of Toll-Like Receptor 2-Mediated Myocardial Inflammation.

Background Heart failure (HF) is one of the most significant causes of morbidity and mortality for the cardiovascular risk population. We found previously that extracellular HSP70 (heat shock protein) is an important trigger in cardiac hypertrophy and fibrosis, which are associated with the development of heart dysfunction. However, the potential role of HSP70 in response to HF and whether it could be a target for the therapy of HF remain unknown. Methods and Results An HF mouse model was generated by a single IP injection of doxorubicin at a dose of 15 mg/kg. Ten days later, these mice were treated with an HSP70 neutralizing antibody for 5 times. We observed that doxorubicin treatment increased circulating HSP70 and expression of HSP70 in myocardium and promoted its extracellular release in the heart. Blocking extracellular HSP70 activity by its antibody significantly ameliorated doxorubicin-induced left ventricular dilation and dysfunction, which was accompanied by a significant inhibition of cardiac fibrosis. The cardioprotective effect of the anti-HSP70 antibody was largely attributed to its ability to promote the resolution of myocardial inflammation, as evidenced by its suppression of the toll-like receptor 2-associated signaling cascade and modulation of the intracellular distribution of the p50 and p65 subunits of nuclear factor-κB. Conclusions Extracellular HSP70 serves as a noninfectious inflammatory factor in the development of HF, and blocking extracellular HSP70 activity may provide potential therapeutic benefits for the treatment of HF.

Targeting Degradation of the Transcription Factor C/EBPß Reduces Lung Fibrosis by Restoring Activity of the Ubiquitin-Editing Enzyme A20 in Macrophages.

Although recent progress provides mechanistic insights into the pathogenesis of pulmonary fibrosis (PF), rare anti-PF therapeutics show definitive promise for treating this disease. Repeated lung epithelial injury results in injury-repairing response and inflammation, which drive the development of PF. Here, we report that chronic lung injury inactivated the ubiquitin-editing enzyme A20, causing progressive accumulation of the transcription factor C/EBPß in alveolar macrophages (AMs) from PF patients and mice, which upregulated a number of immunosuppressive and profibrotic factors promoting PF development. In response to chronic lung injury, elevated glycogen synthase kinase-3ß (GSK-3ß) interacted with and phosphorylated A20 to suppress C/EBPß degradation. Ectopic expression of A20 or pharmacological restoration of A20 activity by disturbing the A20-GSK-3ß interaction accelerated C/EBPß degradation and showed potent therapeutic efficacy against experimental PF. Our study indicates that a regulatory mechanism of the GSK-3ß-A20-C/EBPß axis in AMs may be a potential target for treating PF and fibroproliferative lung diseases.

TRIB3 Interacts With ß-Catenin and TCF4 to Increase Stem Cell Features of Colorectal Cancer Stem Cells and Tumorigenesis.

BACKGROUND & AIMS: Activation of Wnt signaling to ß-catenin contributes to the development of colorectal cancer (CRC). Expression of tribbles pseudo-kinase 3 (TRIB3) is increased in some colorectal tumors and associated with poor outcome. We investigated whether increased TRIB3 expression promotes stem cell features of CRC cells and tumor progression by interacting with the Wnt signaling pathway. METHODS: We performed studies with C57BL/6J-ApcMin/J mice injected with an adeno-associated virus vector that expresses a small hairpin RNA against Trib3 mRNA (ApcMin/J-Trib3KD) or a control vector (ApcMin/J-Ctrl). We created BALB/c mice that overexpress TRIB3 from an adeno-associated virus vector and mice with small hairpin RNA-mediated knockdown of ß-catenin. The mice were given azoxymethane followed by dextran sodium sulfate to induce colitis-associated cancer. Intestinal tissues were collected and analyzed by histology, gene expression profiling, immunohistochemistry, and immunofluorescence. Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5)-positive (LGR5Pos) and LGR5-negative (LGR5Neg) HCT-8 CRC cells, with or without knockdown or transgenic expression of TRIB3, were sorted and analyzed in sphere-formation assays. We derived organoids from human and mouse colorectal tumors to analyze the function of TRIB3 and test the effect of a peptide inhibitor. Wnt signaling to ß-catenin was analyzed in dual luciferase reporter, chromatin precipitation, immunofluorescence, and immunoblot assays. Proteins that interact with TRIB3 were identified by immunoprecipitation. CRC cell lines were grown in nude mice as xenograft tumors. RESULTS: At 10 weeks of age, more than half the ApcMin/J-Ctrl mice developed intestinal high-grade epithelial neoplasia, whereas ApcMin/J-Trib3KD mice had no intestinal polyps and normal histology. Colon tissues from ApcMin/J-Trib3KD mice expressed lower levels of genes regulated by ß-catenin and genes associated with cancer stem cells. Mice with overexpression of Trib3 developed more tumors after administration of azoxymethane and dextran sodium sulfate than BALB/c mice. Mice with knockdown of ß-catenin had a lower tumor burden after administration of azoxymethane and dextran sodium sulfate, regardless of Trib3 overexpression. Intestinal tissues from mice with overexpression of Trib3 and knockdown of ß-catenin did not have activation of Wnt signaling or expression of genes regulated by ß-catenin. LGR5Pos cells sorted from HCT-8 cells expressed higher levels of TRIB3 than LGR5Neg cells. CRC cells that overexpressed TRIB3 had higher levels of transcription by ß-catenin and formed larger spheroids than control CRC cells; knockdown of ß-catenin prevented the larger organoid size caused by TRIB3 overexpression. TRIB3 interacted physically with ß-catenin and transcription factor 4 (TCF4). TRIB3 overexpression increased, and TRIB3 knockdown decreased, recruitment of TCF4 and ß-catenin to the promoter region of genes regulated by Wnt. Activated ß-catenin increased expression of TRIB3, indicating a positive-feedback loop. A peptide (P2-T3A6) that bound ß-catenin disrupted its interaction with TRIB3 and TCF4. In primary CRC cells and HCT-8 cells, P2-T3A6 decreased expression of genes regulated by ß-catenin and genes associated with cancer stem cells and decreased cell viability and migration. Injection of C57BL/6J-ApcMin/J mice with P2-T3A6 decreased the number and size of tumor nodules and colon expression of genes regulated by ß-catenin. P2-T3A6 increased 5-fluorouracil-induced death of CRC cells and survival times of mice with xenograft tumors. CONCLUSION: TRIB3 interacts with ß-catenin and TCF4 in intestine cells to increase expression of genes associated with cancer stem cells. Knockdown of TRIB3 decreases colon neoplasia in mice, migration of CRC cells, and their growth as xenograft tumors in mice. Strategies to block TRIB3 activity might be developed for treatment of CRC.

Metformin suppresses melanoma progression by inhibiting KAT5-mediated SMAD3 acetylation, transcriptional activity and TRIB3 expression.

Metformin has beneficial effects of preventing and treating cancers on type 2 diabetic patients. However, the role of metformin in non-diabetic cancer patients and the precise molecular mechanisms against cancer have not yet been sufficiently elucidated. We recently reported that the pseudokinase protein TRIB3 acts as a stress sensor linking metabolic stressors to cancer promotion by inhibiting autophagy and ubiquitin-proteasomal degradation systems; genetically abrogating of TRIB3 expression reduces tumourigenesis and cancer progression. Thus, TRIB3 is a potential therapeutic target for diverse cancers. In this study, we found that metformin attenuates melanoma growth and metastasis by reducing TRIB3 expression in non-diabetic C57BL/6 mice and diabetic KK-Ay mice; overexpression of TRIB3 protects metformin from the activation of autophagic flux, the clearance of accumulated tumour-promoting factors and the attenuation of tumour progression. We further elucidated that TRIB3 acts as an adaptor to recruit lysine acetyltransferase 5 (KAT5) to SMAD3 and induce a phosphorylation-dependent K333 acetylation of SMAD3, which sustains transcriptional activity of SMAD3 and subsequently enhances TRIB3 transcription. Metformin suppresses SMAD3 phosphorylation and decreases the KAT5/SMAD3 interaction, to attenuate the KAT5-mediated K333 acetylation of SMAD3, reduce the SMAD3 transcriptional activity and subsequent TRIB3 expression, thereby antagonizes melanoma progression. Together, our study not only defines a molecular mechanism by which metformin protects against melanoma progression by disturbing the KAT5/TRIB3/SMAD3 positive feedback loop in diabetes and non-diabetes mice, but also suggests a candidate diverse utility of metformin in tumour prevention and therapy because of suppressing stress protein TRIB3 expression.