ATF4 promotes lung cancer cell proliferation and invasion partially through regulating Wnt/β-catenin signaling

Signal Transducer and Activator of Transcription 4-Induced Up-Regulated LINC01278 Enhances Proliferation and Invasion of Non-Small Cell Lung Cancer Cells via the MicroRNA-877-5p/Activating Transcription Factor 4 Axis

BACKGROUND

The purpose of this study was to investigate the specific effects of signal transducer and activator of transcription 4 (STAT4)-induced long intergenic nonprotein coding RNA 1278 (LINC01278) on the growth of non-small cell lung cancer (NSCLC) cells involved in the microRNA (miR)-877-5p/activated transcription factor 4 (ATF4) axis.

METHODS

NSCLC tumor tissue and adjacent normal tissue were collected. Human normal lung epithelial cell BEAS-2B and human NSCLC cell lines (H1299, H1975, A549, H2228) were collected. The expression levels of STAT4, LINC01278, miR-877-5p, and ATF4 were detected. A549 cells were screened for subsequent experiments. The proliferation ability of cells was detected by colony formation experiment. Cell apoptosis was tested by flow cytometry. Scratch test and transwell assay were used to detect the migration and invasion ability of cells. Biological function of LINC01278 in NSCLC was confirmed by xenograft experiments.

RESULTS

Low expression miR-877-5p and high expression of STAT4, LINC01278 and ATF4 were detected in NSCLC. Silenced LINC01278 in A549 cell depressed cell proliferation, migration and invasion, but facilitated cell apoptosis. LINC01278 was positively correlated with STAT4 and could directly bind to miR-877-5p. Upregulating miR-877-5p suppressed NSCLC cell progression, while downregulating miR-877-5p had the opposite effect. Upregulating miR-877-5p abrogated the effects of silenced LINC01278 on NSCLC cell progression. MiR-877-5p targeted ATF4. ATF4 upregulation could partly restore the carcinogenic effect of LINC01278 in vitro and in vivo.

CONCLUSION

Our data supports that STAT4-induced upregulation of LINC01278 promotes NSCLC progression by modulating the miR-877-5p/ATF4 axis, suggesting a novel direction for NSCLC treatment.

NCI 159456 PERK Inhibitor as a Targeted Therapy for Lung Cancer: An In Vitro Study

Non-small cell lung cancer (NSCLC) represents the most common histological type of lung cancer, characterized by a five-year survival rate of 15% and poor prognosis. Accumulating evidence indicates a prominent role of endoplasmic reticulum (ER) stress and the protein kinase RNA-like ER kinase (PERK)-dependent pathway of the unfolded protein response (UPR) in the pathogenesis of NSCLC. Increased expression of downstream targets of PERK was observed in various subtypes of NSCLC, and it was associated with a more aggressive phenotype, high risk of recurrence, and poor prognosis. Therefore, the present study aimed to investigate the biological effect of the selective PERK inhibitor NCI 159456 on A549 NSCLC cells and Human Pulmonary Fibroblasts (HPF) in vitro. Treatment of both normal and ER-stressed A549 cells with NCI 159456 resulted in a significant increase in the mRNA expression level of pro-apoptotic genes like activating transcription factor 4 (ATF4), DNA damage inducible transcript 3 (DDIT3), and BCL2 Associated X, Apoptosis Regulator (BAX) as well as a decreased level of the anti-apoptotic gene B-cell lymphoma 2 (Bcl-2). Cytotoxicity and genotoxicity analyses revealed that NCI 159456 significantly decreased viability and increased DNA damage in A549 cells under normal and ER stress conditions. Caspase-3 and reactive oxygen species (ROS) detection assays demonstrated that NCI 159456 significantly induced apoptosis and increased the ROS level in normal and ER-stressed A549 cells. Importantly, treatment with the inhibitor did not affect substantially normal HPF cells at any used concentration. The results indicate that PERK inhibitors could potentially be applied as a targeted therapy for NSCLC.

Anticancer activities of natural abietic acid

Cancer is the main cause of death in the world. There are several therapies that are in practice for cancer cure including radiotherapy, chemotherapy, and surgery. Among the chemotherapies, natural products are considered comparable safe, easily available and cost effective. Approximately 60% of cancer approved FDA drugs are natural products including vinblastine, doxorubicin, and paclitaxel. These natural products have complex structures due to which they work against cancer through different molecular pathways, STAT3, NF-kB, PI3K/AKT/mTOR, cell cycle arrest, mitochondrial dependent pathway, extrinsic apoptosis pathway, autophagy, mitophagy and ferroptosis. AA is a natural abietane diterpenoid compound from Pinus palustris and Pimenta racemose var. grissea with different pharmacological activities including anti-inflammatory, anti-convulsant, anti-obesity and anti-allergic. Recently it has been reported with its anticancer activities through different molecular mechanisms including NF-kB, PI3K/AKT, call cycle arrest at G0/G1 phase, mitochondrial dependent pathway, extrinsic apoptosis pathway, AMPK pathway and ferroptosis pathways. The literature survey reveals that there is no review on AA anticancer molecular mechanisms, therefore in current review, we summarize the anticancer molecular mechanisms of AA.

Activating transcription factor 4: a regulator of stress response in human cancers

Activating transcription factor 4 (ATF4) is an adaptive response regulator of metabolic and oxidative homeostasis. In response to cellular stress, ATF4 is activated and functions as a regulator to promote cell adaptation for survival. As a transcriptional regulator, ATF4 also widely participates in the regulation of amino acid metabolism, autophagy, redox homeostasis and endoplasmic reticulum stress. Moreover, ATF4 is associated with the initiation and progression of glioblastoma, hepatocellular carcinoma, colorectal cancer, gastric cancer, breast cancer, prostate cancer and lung cancer. This review primarily aims to elucidate the functions of ATF4 and its role in multiple cancer contexts. This review proposes potential therapeutic targets for clinical intervention.

An innovative nanoformulation utilizing tumor microenvironment-responsive PEG-polyglutamic coating and dynamic charge adjustment for specific targeting of ER stress inducer, microRNA, and immunoadjuvant in pancreatic cancer: In vitro investigations

Pancreatic ductal adenocarcinoma (PDAC) is a significant obstacle to lowering global cancer deaths. CB-5083, a novel valosin-containing protein (VCP)/p97 inhibitor that disrupts proteasomal degradation and induces endoplasmic reticulum stress (ERS) accumulation, was evaluated as an inducer of immunogenic cell death (ICD) in PDAC treatment. Furthermore, miR-142 enhances checkpoint blockade and promotes M1 repolarization, while Toll-like receptor 7/8 agonist resiquimod (R) acts as an immunoadjuvant to amplify the immune response to miR-142. This research signifies the first integration of CB, miR-142, and R in solid lipid nanoparticles (SLNs) modified with peptides targeting PD-L1, EGFR, and ER, which were shelled by the PEG-polyglutamic (PGA) coating that detaches in response to the acidic pH values in the tumor microenvironment (TME). The modified SLNs exhibited pH-sensitive cytotoxicity against Panc-02 cells, preserving normal cells and preventing hemolysis. The innovative approach simultaneously modulated pathways, including VCP/Bip/K48-Ub/ATF6, IRE1α/XBPs/LC3II, PD-L1/TGF-β/IL-10/CD206/MSR1/Arg1, and TNF-α/IFN-γ/IL-6/iNOS/COX-2. Combined treatment blocked VCP, arrested the cell cycle, inhibited EMT, triggered ERS-mediated autophagy/apoptosis, and stimulated robust ICD via the release of damage-associated molecular patterns. This adaptable nanoformulation, displaying pH-sensitive PEG-PGA de-coating and precisely targeting EGFR, PD-L1, and ER, serves to hinder EMT and immune evasion, subsequently amplifying ICD in PDAC cells and the TME.

Advances in the roles of ATF4 in osteoporosis

Osteoporosis (OP) is characterized by reduced bone mass, decreased strength, and enhanced bone fragility fracture risk. Activating transcription factor 4 (ATF4) plays a role in cell differentiation, proliferation, apoptosis, redox balance, amino acid uptake, and glycolipid metabolism. ATF4 induces the differentiation of bone marrow mesenchymal stem cells (BM-MSCs) into osteoblasts, increases osteoblast activity, and inhibits osteoclast formation, promoting bone formation and remodeling. In addition, ATF4 mediates the energy metabolism in osteoblasts and promotes angiogenesis. ATF4 is also involved in the mediation of adipogenesis. ATF4 can selectively accumulate in osteoblasts. ATF4 can directly interact with RUNT-related transcription factor 2 (RUNX2) and up-regulate the expression of osteocalcin (OCN) and osterix (Osx). Several upstream factors, such as Wnt/β-catenin and BMP2/Smad signaling pathways, have been involved in ATF4-mediated osteoblast differentiation. ATF4 promotes osteoclastogenesis by mediating the receptor activator of nuclear factor κ-B (NF-κB) ligand (RANKL) signaling. Several agents, such as parathyroid (PTH), melatonin, and natural compounds, have been reported to regulate ATF4 expression and mediate bone metabolism. In this review, we comprehensively discuss the biological activities of ATF4 in maintaining bone homeostasis and inhibiting OP development. ATF4 has become a therapeutic target for OP treatment.

Transducin Beta-Like 2 is a Potential Driver Gene that Adapts to Endoplasmic Reticulum Stress to Promote Tumor Growth of Lung Adenocarcinoma

BACKGROUND

Endoplasmic reticulum (ER) stress has a close relation with cancer progression. Blocking the adaptive pathway of ER stress could be an anticancer strategy. Here, we identified an ER stress-related gene, Transducin beta-like 2 (TBL2), an ER-localized type I transmembrane protein, on increased chromosome 7q as a candidate driver gene of lung adenocarcinoma (LUAD).

METHODS

The association between TBL2 mRNA expression and prognostic outcomes and clinicopathological factors was analyzed using The Cancer Genome Atlas (TCGA) datasets of LUAD and lung squamous cell carcinoma (LUSC). Localization of TBL2 in tumor tissues was observed by immunohistochemical staining. Gene set enrichment analysis (GSEA) was conducted using TCGA dataset. In vitro cell proliferation assays were performed using TBL2 knockdown LUAD cells, LUSC cells, and LUAD cells overexpressing TBL2. Apoptosis and ATF4 expression (ER stress marker) were evaluated by western blotting.

RESULTS

TBL2 was overexpressed in LUAD and LUSC cells. Multivariate analysis indicated high TBL2 mRNA expression was an independent poor prognostic factor of LUAD. GSEA revealed high TBL2 expression was positively correlated to the ER stress response in LUAD. TBL2 knockdown attenuated LUAD cell proliferation under ER stress. TBL2 inhibited apoptosis in LUAD cells under ER stress. TBL2 knockdown reduced ATF4 expression under ER stress.

CONCLUSIONS

TBL2 may be a novel driver gene that facilitates cell proliferation, possibly by upregulating ATF4 expression followed by adaptation to ER stress, and it is a poor prognostic biomarker of LUAD.

Single-cell RNA sequencing reveals enhanced antitumor immunity after combined application of PD-1 inhibitor and Shenmai injection in non-small cell lung cancer

BACKGROUND

Immune checkpoint inhibitors (ICIs) have altered the clinical management of non-small cell lung cancer (NSCLC). However, the low response rate, severe immune-related adverse events (irAEs), and hyperprogressive disease following ICIs monotherapy require attention. Combination therapy may overcome these limitations and traditional Chinese medicine with immunomodulatory effects provides a promising approach. Shenmai injection (SMI) is a clinically effective adjuvant treatment for cancer with chemotherapy and radiotherapy. Therefore, the combined effects and mechanisms of SMI and programmed death-1 (PD-1) inhibitor against NSCLC was focused on this study.

METHODS

A Lewis lung carcinoma mouse model and a lung squamous cell carcinoma humanized mouse model were used to investigate the combined efficacy and safety of SMI and PD-1 inhibitor. The synergistic mechanisms of the combination therapy against NSCLC were explored using single-cell RNA sequencing. Validation experiments were performed using immunofluorescence analysis, in vitro experiment, and bulk transcriptomic datasets.

RESULTS

In both models, combination therapy alleviated tumor growth and prolonged survival without increasing irAEs. The GZMA^high and XCL1^high natural killer (NK) cell subclusters with cytotoxic and chemokine signatures increased in the combination therapy, while malignant cells from combination therapy were mainly in the apoptotic state, suggesting that mediating tumor cell apoptosis through NK cells is the main synergistic mechanisms of combination therapy. In vitro experiment confirmed that combination therapy increased secretion of Granzyme A by NK cells. Moreover, we discovered that PD-1 inhibitor and SMI combination blocked inhibitory receptors on NK and T cells and restores their antitumoral activity in NSCLC better than PD-1 inhibitor monotherapy, and immune and stromal cells exhibited a decrease of angiogenic features and attenuated cancer metabolism reprogramming in microenvironment of combination therapy.

CONCLUSIONS

This study demonstrated that SMI reprograms tumor immune microenvironment mainly by inducing NK cells infiltration and synergizes with PD-1 inhibitor against NSCLC, suggested that targeting NK cells may be an important strategy for combining with ICIs. Video Abstract.

ATF4 Transcriptionally Activates SHH to Promote Proliferation, Invasion, and Migration of Gastric Cancer Cells

Activating transcription factor 4 (ATF4) is a DNA-binding protein widely generated in mammals, which has two biological characteristics that bind the cAMP response element (CRE). The mechanism of ATF4 as a transcription factor in gastric cancer affecting the Hedgehog pathway remains unclear. Here, we observed that ATF4 was markedly upregulated in gastric cancer (GC) using immunohistochemistry and Western blotting assays in 80 paraffin-embedded GC samples and 4 fresh samples and para-cancerous tissues. ATF4 knockdown using lentiviral vectors strongly inhibited the proliferation and invasion of GC cells. ATF4 upregulation using lentiviral vectors promoted the proliferation and invasion of GC cells. We predicted that the transcription factor ATF4 is bound to the SHH promoter via the JASPA database. Transcription factor ATF4 is bound to the promoter region of SHH to activate the Sonic Hedgehog pathway. Mechanistically, rescue assays showed that ATF4 regulated gastric cancer cells' proliferation and invasive ability through SHH. Similarly, ATF4 enhanced the tumor formation of GC cells in a xenograft model.

A stay of execution: ATF4 regulation and potential outcomes for the integrated stress response

ATF4 is a cellular stress induced bZIP transcription factor that is a hallmark effector of the integrated stress response. The integrated stress response is triggered by phosphorylation of the alpha subunit of the eukaryotic initiation factor 2 complex that can be carried out by the cellular stress responsive kinases; GCN2, PERK, PKR, and HRI. eIF2α phosphorylation downregulates mRNA translation initiation en masse, however ATF4 translation is upregulated. The integrated stress response can output two contradicting outcomes in cells; pro-survival or apoptosis. The mechanism for choice between these outcomes is unknown, however combinations of ATF4 heterodimerisation partners and post-translational modifications have been linked to this regulation. This semi-systematic review article covers ATF4 target genes, heterodimerisation partners and post-translational modifications. Together, this review aims to be a useful resource to elucidate the mechanisms controlling the effects of the integrated stress response. Additional putative roles of the ATF4 protein in cell division and synaptic plasticity are outlined.

Morusin Protected Ruminal Epithelial Cells against Lipopolysaccharide-Induced Inflammation through Inhibiting EGFR-AKT/NF-κB Signaling and Improving Barrier Functions

Using phytogenic extracts for preventing or treating rumen epithelial inflammatory injury is a potential alternative to antibiotic use due to their residue-free characteristics. In this study, the efficacy of Morus root bark extract Morusin on ruminal epithelial cells (RECs) against pathogenic stimulus was investigated for the first time. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and quantitative real-time polymerase chain reaction (qPCR) results showed that the Morusin did not affect the cell viability of RECs and exerted anti-inflammatory effects in a concentration-dependent manner. Transcriptome analysis further revealed that the Morusin significantly downregulated the inflammatory-response-related cell signaling, while it upregulated the cell-proliferation-inhibition- and barrier-function-related processes in RECs upon lipopolysaccharide (LPS) stimulation. The epidermal growth factor receptor (EGFR) blocking and immunoblotting analysis further confirmed that the Morusin suppressed LPS-induced inflammation in RECs by downregulating the phosphorylation of protein kinase B (AKT) and nuclear factor-kappaB (NF-κB) p65 protein via inhibiting the EGFR signaling. These findings demonstrate the protective roles of Morusin in LPS-induced inflammation in RECs.

Identification and Validation of Ferroptosis-Related Genes in Sevoflurane-Induced Hippocampal Neurotoxicity

Background

Sevoflurane is one of the most popular inhalational anesthetics during perioperative period but presenting neurotoxicity among pediatric and aged populations. Recent experiments in vivo and in vitro have indicated that ferroptosis may contribute to the neurotoxicity of sevoflurane anesthesia. However, the exact mechanism is still unclear.

Methods

In current study, we explored the differential expressed genes (DEGs) in HT-22 mouse hippocampal neuronal cells after sevoflurane anesthesia using RNA-seq. Differential expressed ferroptosis-related genes (DEFRGs) were screened and analyzed by Gene Ontology (GO) and pathway enrichment analysis. Protein-to-protein interaction (PPI) network was constructed by the Search Tool for the Retrieval of Interacting Genes (STRING). Significant modules and the hub genes were identified by using Cytoscape. The Connectivity Map (cMAP) was used for screening drug candidates targeting the identified DEFRGs. Potential TF-gene network and drug-gene pairs were established towards the hub genes. In final, we validated these results in experiments.

Results

A total of 37 ferroptosis-related genes (18 upregulated and 19 downregulated) after sevoflurane exposure in hippocampal neuronal cells were finally identified. These differentially expressed genes were mainly involved into the biological processes of cellular response to oxidative stress. Pathway analysis indicated that these genes were involved in ferroptosis, mTOR signaling pathway, and longevity-regulating pathway. PPI network was constructed. 10 hub genes including Prkaa2, Chac1, Arntl, Tfrc, Slc7a11, Atf4, Mgst1, Lpin1, Atf3, and Sesn2 were found. Top 10 drug candidates, gene-drug networks, and TFs targeting these genes were finally identified. These results were validated in experiments.

Conclusion

Our results suggested that ferroptosis-related genes play roles in sevoflurane anesthesia-related hippocampal neuron injury and offered the hub genes and potential therapeutic agents for investigating and treatment of this neurotoxicity after sevoflurane exposure. Finally, therapeutic effect of these drug candidates and function of potential ferroptosis targets should be further investigated for treatment and clarifying mechanisms of sevoflurane anesthesia-induced neuron injury in future research.

Identification of benzamides derivatives of norfloxacin as promising microRNA-21 inhibitors via repressing its transcription

MicroRNA-21 is a carcinogenic microRNA, whose overexpression arises in a variety of tumor tissues. Hence, microRNA-21 a prospective target for cancer treatment, and regulation of microRNA-21 by small molecule inhibitors is deemed as a promising approach for tumor therapy. In this work, to discover potent microRNA-21 inhibitor, series of 4-(N-norfloxacin-acyl)aminobenzamides were designed and synthesized, and their inhibitory effects were appraised by utilizing dual luciferase reporter assays. The results indicated that compound A7 was the most efficient microRNA-21 small molecule inhibitor. What's more, A7 suppressed the migration of Hela cells and the colony formation of Hela and HCT-116 cells as well as promoted apoptosis of Hela cells. In the mechanism study, results of RT-qPCR certified that A7 could reduce the level of mature microRNA-21 via disrupting its expression at the transcriptional level of its primary form "pri-miR-21", which was distinct from most previous inhibitors directly binding with pre-miR-21. Noticeably, Western blotting and RT-qPCR uncovered A7 could upregulate the expression PTEN, EGR1 and SLIT2, which are the downstream functional targets of microRNA-21. These findings demonstrated that A7 was a promising microRNA-21 small molecule inhibitor and 4-(N-norfloxacin-acyl) aminobenzamide can serve as a new scaffold for discovery of potent microRNA-21 inhibitor.

Downregulation of HULC Induces Ferroptosis in Hepatocellular Carcinoma via Targeting of the miR-3200-5p/ATF4 Axis

Hepatocellular carcinoma is a malignant tumor that poses a serious threat to human health. Ferroptosis, which represents an identified type of regulated iron-dependent cell death, may play an important role in hepatocellular carcinoma. However, it is unclear as to whether ferroptosis is involved with the mechanisms of lncRNA HULC in liver cancer cells. Here, we show that knockdown of HULC increases ferroptosis and oxidative stress in liver cancer cells. We also found changes in some related miRNAs in cells treated with HULC siRNA. Differential miRNA expression levels were determined with the use of high-throughput sequencing and prediction target genes identified using bioinformatics analysis. HULC was found to function as a ceRNA of miR-3200-5p, and miR-3200-5p regulates ferroptosis by targeting ATF4, resulting in the inhibition of proliferation and metastasis within HCC cells. In summary, these findings illuminate some of the molecular mechanisms through which downregulation of HULC induces liver cancer cell ferroptosis by targeting the miR-3200-5p/ATF4 axis to modulate the development of hepatocellular carcinoma.

CCDC106 promotes the proliferation and invasion of ovarian cancer cells by suppressing p21 transcription through a p53-independent pathway

Ovarian cancers are the major cause of mortality for women worldwide. This study was aimed to elucidate the biological activities of CCDC106 in the proliferation and invasion of mutant p53 and of wild-type p53 ovarian cancer cells. CAOV3 (mutant p53) cells showed high expression levels of CCDC106, but it was expressed at low levels in SKOV3 (mutant p53) and in A2780 (wild-type p53) cells. The overexpression of CCDC106 promoted the expression of proliferation markers (cyclin family members), invasion and Epithelial-to-mesenchymal transition (EMT) markers (claudin-1, claudin-4, N-cadherin, snail, slug) while the knockdown of CCDC106 inhibited their expression in mutant p53 cells but not in wild-type p53 cells. Treatment with a CK2 inhibitor blocked the translocation of CCDC106 into the nuclei of mutant p53 cells. Immunoprecipitation assays confirmed that ATF4 is a potential binding partner of CCDC106. The overexpression of CCDC106 reduced p21 and p27 protein expression levels while treatment with an ATF4 siRNA rescued their expression. The overexpression of CCDC106 promoted colony formation and invasion of mutant p53 cells, which was suppressed by treatment with an ATF4 siRNA. Immunohistochemistry results showed that CCDC106 and ATF4 are expressed at high levels but p21 is expressed at low levels in FIGO III-IV stage and in mutant p53 ovarian cancer samples. A significant association between poor overall survival and high CCDC106 and ATF4 expression levels was observed in human ovarian cancer samples. In conclusion, CCDC106 promotes proliferation, invasion and EMT of mutant p53 ovarian cancer cells via the ATF4 mediated inhibition of p21.

High ATF4 Expression Is Associated With Poor Prognosis, Amino Acid Metabolism, and Autophagy in Gastric Cancer

Background

The role of activating transcription factor 4 (ATF4) underlying gastric cancer (GC) remains unclear. The purpose of this study was to investigate the expression levels and biological functions of ATF4 in GC.

Methods

Expression of ATF4 was detected by quantitative PCR (qPCR), Western blotting, and immunohistochemistry. Cox regression was used for survival analysis and the construction of the nomogram. Immunofluorescence was used to identify the intracellular localization of ATF4. Knockdown and overexpression of ATF4 in GC cells followed by wound healing and Transwell assays, EdU and Calcein-AM/propidium iodide (PI) staining, and cell cycle detection were performed to examine its function in vitro. Transmission electron microscopy was performed to assess the autophagy levels upon ATF4 silencing. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and gene set enrichment analysis (GSEA) were used to determine gene enrichment. SPSS 22.0 software, GraphPad Prism 7.0, and R version 3.6.1 were used for statistical analysis.

Results

ATF4 expression was upregulated in GC cells and tissues compared with corresponding normal tissues. Survival analysis suggested that a high ATF4 expression was strongly associated with worse overall survival (OS) of GC patients (p < 0.001). The nomogram and the receiver operating characteristic (ROC) curves demonstrated that ATF4 was a highly sensitive and specific prognostic marker of GC [C-index = 0.797, area under the ROC curve (AUC) of 3-year OS = 0.855, and AUC of 5-year OS = 0.863]. In addition, ATF4 knockdown inhibited the cell proliferation, migration, invasion, and cell cycle progression of GC cells in vitro, while overexpression of ATF4 exerted the opposite effects. Bioinformatics analysis showed that ATF4 could promote GC progression possibly by regulating asparagine (Asn) metabolism and autophagy pathways. Further experiments indicated that ATF4 expression was significantly positively correlated with ASNS expression. The inhibition of cell clone formation in Asn-deprived conditions was more significant in the shATF4 group. Finally, we found that ATF4 promoted autophagy through regulating the mTORC1 pathway in GC cells.

Conclusion

These findings suggested that ATF4 can significantly promote GC development and serve as an independent prognostic factor for GC.

Mutual regulation between chicken telomerase reverse transcriptase and the Wnt/β-catenin signalling pathway inhibits apoptosis and promotes the replication of ALV-J in LMH cells

This study aimed to explore the mutual regulation between chicken telomerase reverse transcriptase (chTERT) and the Wnt/β-catenin signalling pathway and its effects on cell growth and avian leukosis virus subgroup J (ALV-J) replication in LMH cells. First, LMH cells stably overexpressing the chTERT gene (LMH-chTERT cells) and corresponding control cells (LMH-NC cells) were successfully constructed with a lentiviral vector expression system. The results showed that chTERT upregulated the expression of β-catenin, Cyclin D1, TCF4 and c-Myc. chTERT expression level and telomerase activity were increased when cells were treated with LiCl. When the cells were treated with ICG001 or IWP-2, the activity of the Wnt/β-catenin signalling pathway was significantly inhibited, and chTERT expression and telomerase activity were also inhibited. However, when the β-catenin gene was knocked down by small interfering RNA (siRNA), the changes in chTERT expression and telomerase activity were consistent with those in cells treated with ICG001 or IWP-2. These results indicated that chTERT and the Wnt/β-catenin signalling pathway can be mutually regulated. Subsequently, we found that chTERT not only shortened the cell cycle to promote proliferation but also inhibited apoptosis by downregulating the expression of Caspase 3, Caspase 9 and BAX; upregulating BCL-2 and BCL-X expression; and promoting autophagy. Moreover, chTERT significantly enhanced the migration ability of LMH cells, upregulated the protein and mRNA expression of ALV-J and increased the virus titre. ALV-J replication promoted chTERT expression and telomerase activity.