Activating transcription factor 3 is overexpressed in human glioma and its knockdown in glioblastoma cells causes growth inhibition both in vitro and in vivo

Dual targeting of histone deacetylases and MYC as potential treatment strategy for H3-K27M pediatric gliomas

Diffuse midline gliomas (DMGs) are aggressive and fatal pediatric tumors of the central nervous system that are highly resistant to treatments. Lysine to methionine substitution of residue 27 on histone H3 (H3-K27M) is a driver mutation in DMGs, reshaping the epigenetic landscape of these cells to promote tumorigenesis. H3-K27M gliomas are characterized by deregulation of histone acetylation and methylation pathways, as well as the oncogenic MYC pathway. In search of effective treatment, we examined the therapeutic potential of dual targeting of histone deacetylases (HDACs) and MYC in these tumors. Treatment of H3-K27M patient-derived cells with Sulfopin, an inhibitor shown to block MYC-driven tumors in vivo, in combination with the HDAC inhibitor Vorinostat, resulted in substantial decrease in cell viability. Moreover, transcriptome and epigenome profiling revealed synergistic effect of this drug combination in downregulation of prominent oncogenic pathways such as mTOR. Finally, in vivo studies of patient-derived orthotopic xenograft models showed significant tumor growth reduction in mice treated with the drug combination. These results highlight the combined treatment with PIN1 and HDAC inhibitors as a promising therapeutic approach for these aggressive tumors.

Changing paradigms in oncology: Toward noncytotoxic treatments for advanced gliomas

Glial-lineage malignancies (gliomas) recurrently mutate and/or delete the master regulators of apoptosis p53 and/or p16/CDKN2A, undermining apoptosis-intending (cytotoxic) treatments. By contrast to disrupted p53/p16, glioma cells are live-wired with the master transcription factor circuits that specify and drive glial lineage fates: these transcription factors activate early-glial and replication programs as expected, but fail in their other usual function of forcing onward glial lineage-maturation-late-glial genes have constitutively "closed" chromatin requiring chromatin-remodeling for activation-glioma-genesis disrupts several epigenetic components needed to perform this work, and simultaneously amplifies repressing epigenetic machinery instead. Pharmacologic inhibition of repressing epigenetic enzymes thus allows activation of late-glial genes and terminates glioma self-replication (self-replication = replication without lineage-maturation), independent of p53/p16/apoptosis. Lineage-specifying master transcription factors therefore contrast with p53/p16 in being enriched in self-replicating glioma cells, reveal a cause-effect relationship between aberrant epigenetic repression of late-lineage programs and malignant self-replication, and point to specific epigenetic targets for noncytotoxic glioma-therapy.

UPF1/circRPPH1/ATF3 feedback loop promotes the malignant phenotype and stemness of GSCs

Glioblastoma multiforme (GBM) is the most lethal type of craniocerebral gliomas. Glioma stem cells (GSCs) are fundamental reasons for the malignancy and recurrence of GBM. Revealing the critical mechanism within GSCs' self-renewal ability is essential. Our study found a novel circular RNA (circRPPH1) that was up-regulated in GSCs and correlated with poor survival. The effect of circRPPH1 on the malignant phenotype and self-renewal of GSCs was detected in vitro and in vivo. Mechanistically, UPF1 can bind to circRPPH1 and maintain its stability. Therefore, more existing circRPPH1 can interact with transcription factor ATF3 to further transcribe UPF1 and Nestin expression. It formed a feedback loop to keep a stable stream for stemness biomarker Nestin to strengthen tumorigenesis of GSCs continually. Besides, ATF3 can activate the TGF-β signaling to drive GSCs for tumorigenesis. Knocking down the expression of circRPPH1 significantly inhibited the proliferation and clonogenicity of GSCs both in vitro and in vivo. The overexpression of circRPPH1 enhanced the self-renewal of GSCs. Our findings suggest that UPF1/circRPPH1/ATF3 maintains the potential self-renewal of GSCs through interacting with RNA-binding protein and activating the TGF-β signal pathway. Breaking the feedback loop against self-renewing GSCs may represent a novel therapeutic target in GBM treatment.

Expression, Regulation, and Functions of the Galectin-16 Gene in Human Cells and Tissues

Galectins comprise a family of soluble β-galactoside-binding proteins, which regulate a variety of key biological processes including cell growth, differentiation, survival, and death. This paper aims to address the current knowledge on the unique properties, regulation, and expression of the galectin-16 gene (LGALS16) in human cells and tissues. To date, there are limited studies on this galectin, with most focusing on its tissue specificity to the placenta. Here, we report the expression and 8-Br-cAMP-induced upregulation of LGALS16 in two placental cell lines (BeWo and JEG-3) in the context of trophoblastic differentiation. In addition, we provide the results of a bioinformatics search for LGALS16 using datasets available at GEO, Human Protein Atlas, and prediction tools for relevant transcription factors and miRNAs. Our findings indicate that LGALS16 is detected by microarrays in diverse human cells/tissues and alters expression in association with cancer, diabetes, and brain diseases. Molecular mechanisms of the transcriptional and post-transcriptional regulation of LGALS16 are also discussed based on the available bioinformatics resources.

ATF3 contributes to brucine-triggered glioma cell ferroptosis via promotion of hydrogen peroxide and iron

Ferroptotic cell death is characterized by iron-dependent lipid peroxidation that is initiated by ferrous iron and H2O2 via Fenton reaction, in which the role of activating transcription factor 3 (ATF3) remains elusive. Brucine is a weak alkaline indole alkaloid extracted from the seeds of Strychnos nux-vomica, which has shown potent antitumor activity against various tumors, including glioma. In this study, we showed that brucine inhibited glioma cell growth in vitro and in vivo, which was paralleled by nuclear translocation of ATF3, lipid peroxidation, and increases of iron and H2O2. Furthermore, brucine-induced lipid peroxidation was inhibited or exacerbated when intracellular iron was chelated by deferoxamine (500 μM) or improved by ferric ammonium citrate (500 μM). Suppression of lipid peroxidation with lipophilic antioxidants ferrostatin-1 (50 μM) or liproxstatin-1 (30 μM) rescued brucine-induced glioma cell death. Moreover, knockdown of ATF3 prevented brucine-induced accumulation of iron and H2O2 and glioma cell death. We revealed that brucine induced ATF3 upregulation and translocation into nuclei via activation of ER stress. ATF3 promoted brucine-induced H2O2 accumulation via upregulating NOX4 and SOD1 to generate H2O2 on one hand, and downregulating catalase and xCT to prevent H2O2 degradation on the other hand. H2O2 then contributed to brucine-triggered iron increase and transferrin receptor upregulation, as well as lipid peroxidation. This was further verified by treating glioma cells with exogenous H2O2 alone. Moreover, H2O2 reversely exacerbated brucine-induced ER stress. Taken together, ATF3 contributes to brucine-induced glioma cell ferroptosis via increasing H2O2 and iron.

Scouting for common genes in the heterogenous hypoxic tumor microenvironment and their validation in glioblastoma

Investigating the therapeutic and prognostic potential of genes in the heterogeneous hypoxic niche of glioblastoma. We have analyzed RNA expression of U87MG cells cultured in hypoxia compared to normoxia. Common differentially expressed genes (DEGs) from GSE45301 and GSE18494 and their functional enrichment was performed using MetaScape and PANTHER. Hub genes and their ontology were identified using MCode cytoHubba and ClueGO and validated with GlioVis, Oncomine, HPA and PrognoScan. Using the GEO2R analysis of GSE45301 and GSE18494 datasets, we have found a total of 246 common DEGs (180 upregulated and 66 downregulated) and identified 2 significant modules involved in ribosome biogenesis and TNF signaling. Meta-analysis of key genes of each module in cytoHubba identified 17 hub genes (ATF3, BYSL, DUSP1, EGFR, JUN, ETS1, LYAR, NIP7, NOLC1, NOP2, NOP56, PNO1, RRS1, TNFAIP3, TNFRSF1B, UTP15, VEGFA). Of the 17 hub genes, ATF3, BYSL, EGFR, JUN, NIP7, NOLC1, PNO1, RRS1, TNFAIP3 and VEGFA were identified as hypoxia signatures associated with poor prognosis in Glioma. Ribosome biogenesis emerged as a vital contender of possible therapeutic potential with BYSL, NIP7, NOLC1, PNO1 and RRS1 showing prognostic value.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02987-2.

Apocynin ameliorates NADPH oxidase 4 (NOX4) induced oxidative damage in the hypoxic human retinal Müller cells and diabetic rat retina

NADPH oxidase (NOX) is a main producers of reactive oxygen species (ROS) that may contribute to the early pathogenesis of diabetic retinopathy (DR). ROS has harmful effects on endogenous neuro-survival factors brain-derived neurotrophic factor (BDNF) and sirtuin 1 (SIRT1) are necessary for the growth and survival of the retina. The role of NOX isoforms NOX4 in triggering ROS in DR is not clear. Here we determine the protective effects of a plant-derived NOX inhibitor apocynin (APO) on NOX4-induced ROS production which may contribute to the depletion of survival factors BDNF/SIRT1 or cell death in the diabetic retinas. Human retinal Müller glial cells (MGCs) were treated with hypoxia mimetic agent cobalt chloride (CoCl₂) in the absence or presence of APO. Molecular analysis demonstrates that NOX4 is upregulated in CoCl₂-treated MGCs and in the diabetic retinas. Increased NOX4 was accompanied by the downregulation of BDNF/SIRT1 expression or in the activation of apoptotic marker caspase-3. Whereas, APO treatment downregulates NOX4 and subsequently upregulates BDNF/SIRT1 or alleviate caspase-3 expression. Accordingly, in the diabetic retina we found a positive correlation in NOX4 vs ROS (p = 0.025; R² = 0.488) and caspase-3 vs ROS (p = 0.04; R² = 0.428); whereas a negative correlation in BDNF vs ROS (p = 0.009; R² = 0.596) and SIRT1 vs ROS (p = 0.0003; R² = 0.817) respectively. Taken together, NOX4-derived ROS could be a main contributor in downregulating BDNF/SIRT1 expression or in the activation of caspase-3. Whereas, APO treatment may minimize the deleterious effects occurring due to hyperglycemia and/or diabetic mimic hypoxic condition in early pathogenesis of DR.

Time-Resolved Profiling Reveals ATF3 as a Novel Mediator of Endocrine Resistance in Breast Cancer

Breast cancer is one of the leading causes of death for women worldwide. Patients whose tumors express Estrogen Receptor α account for around 70% of cases and are mostly treated with targeted endocrine therapy. However, depending on the degree of severity of the disease at diagnosis, 10 to 40% of these tumors eventually relapse due to resistance development. Even though recent novel approaches as the combination with CDK4/6 inhibitors increased the overall survival of relapsing patients, this remains relatively short and there is a urgent need to find alternative targetable pathways. In this study we profiled the early phases of the resistance development process to uncover drivers of this phenomenon. Time-resolved analysis revealed that ATF3, a member of the ATF/CREB family of transcription factors, acts as a novel regulator of the response to therapy via rewiring of central signaling processes towards the adaptation to endocrine treatment. ATF3 was found to be essential in controlling crucial processes such as proliferation, cell cycle, and apoptosis during the early response to treatment through the regulation of MAPK/AKT signaling pathways. Its essential role was confirmed in vivo in a mouse model, and elevated expression of ATF3 was verified in patient datasets, adding clinical relevance to our findings. This study proposes ATF3 as a novel mediator of endocrine resistance development in breast cancer and elucidates its role in the regulation of downstream pathways activities.

Expression, association with clinicopathological features and prognostic potential of CEP55, p-Akt, FoxM1 and MMP-2 in astrocytoma

Centrosomal protein 55 (CEP55) is a member of the centrosomal-associated protein family and participates in the regulation of cytokinesis during cell mitosis. However, aberrant CEP55 protein expression has been observed in human tumors. In addition, CEP55 regulates the biological functions of tumors by inducing the Akt pathway and upregulating forkhead box protein M1 (FoxM1) and matrix metalloproteinase-2 (MMP-2). In the present study, the levels, clinicopathological features and prognostic potential of CEP55, phosphorylated Akt (p-Akt), FoxM1 and MMP-2 in astrocytoma were evaluated. CEP55, p-Akt, FoxM1 and MMP-2 levels were examined in 27 normal brain tissues and 262 astrocytoma tissues by using immunohistochemistry. Furthermore, Kaplan-Meier analysis and Cox proportional hazards models were applied to predict the prognosis of patients with astrocytoma. The results indicated that expression levels of CEP55 and other proteins were elevated in human astrocytoma compared with those in normal brain tissue. The levels of the selected proteins were increased as the tumor grade increased. Furthermore, CEP55 expression was positively correlated with p-Akt, FoxM1 and MMP-2 levels in astrocytoma. Overall survival analysis revealed that patient prognosis was associated with CEP55, p-Akt, FoxM1 and MMP-2 levels, as well as with the tumor grade and patient age. Furthermore, CEP55, FoxM1, tumor grade and patient age were independent prognostic factors in astrocytoma according to multivariate analysis. Taken together, the present results suggested that CEP55, p-Akt, FoxM1 and MMP-2 have crucial roles in the progression and prognosis of human astrocytoma and that CEP55 and FoxM1 may be potential therapeutic targets.

Subcellular expression of maspin – from normal tissue to tumor cells

Maspin or SerpinB5, a member of the serine protease inhibitor family, was shown to function as a tumor suppressor, especially in carcinomas. It seems to inhibit invasion, tumor cells motility and angiogenesis, and promotes apoptosis. Maspin can also induce epigenetic changes such as cytosine methylation, de-acetylation, chromatin condensation, and histone modulation. In this review, a comprehensive synthesis of the literature was done to present maspin function from normal tissues to pathologic conditions. Data was sourced from MEDLINE and PubMed. Study eligibility criteria included: Published in English, between 1994 and 2019, specific to humans, and with full-text availability. Most of the 118 studies included in the present review focused on maspin immunostaining and mRNA levels. It was shown that maspin function is organ-related and depends on its subcellular localization. In malignant tumors, it might be downregulated or negative (e.g., carcinoma of prostate, stomach, and breast) or upregulated (e.g., colorectal and pancreatic tumors). Its subcellular localization (nuclear vs cytoplasm), which can be proved using immunohistochemical methods, was shown to influence both tumor behavior and response to chemotherapy. Although the number of maspin-related papers increased, the exact role of this protein remains unknown, and its interpretation should be done with extremely high caution.

Overexpression of activating transcription factor 3 exerts suppressive effects in HepG2 cells

The present study observed and compared the biological behaviour of HepG2 cells prior and subsequent to the overexpression of activating transcription factor 3 (ATF3). Experiments investigating the cytological function by which ATF3 affects liver cancer cells were also performed. MTT, Transwell and flow cytometry assays were used to observe and detect the biological behaviour of HepG2 cells with and without lentivirus (LV)-ATF3-enhanced green fluorescent protein (EGFP) infection. The effects of ATF3 overexpression on cell proliferation, migration, apoptosis and cell cycle progression were evaluated. The LV-ATF3-EGFP overexpression vector was successfully constructed, and the HepG2 cells were successfully infected with the vector. Following ATF3 overexpression, cell proliferation was decreased, the rate of cell apoptosis was accelerated and cell cycle progression was slowed (P<0.05). There were no marked changes in cell migration (P>0.05), although there was a trend towards a gradual decrease. In conclusion, ATF3 exerted suppressive effects in HepG2 cells, potentially by inhibiting cancer cell growth, accelerating cell apoptosis, and blocking cell cycle progression. Intervention targeting ATF3 expression may represent a novel approach for the prevention and treatment of human liver cancer.

Bioinformatics analysis of gene expression profiles to diagnose crucial and novel genes in glioblastoma multiform

Therefore, the current study aimed to diagnose the genes associated in the pathogenesis of GBM. The differentially expressed genes (DEGs) were diagnosed using the limma software package. The ToppFun was used to perform pathway and Gene Ontology (GO) enrichment analysis of the DEGs. Protein-protein interaction (PPI) networks, extracted modules, miRNA-target genes regulatory network and miRNA-target genes regulatory network were used to obtain insight into the actions of DEGs. Survival analysis for DEGs carried out. A total of 701 DEGs, including 413 upregulated and 288 downregulated genes, were diagnosed between U1118MG cell line (PK 11195 treated with 1 h exposure) and U1118MG cell line (PK 11195 treated with 24 h exposure). The up-regulated genes were enriched in superpathway of pyrimidine deoxyribonucleotides de novo biosynthesis, cell cycle, cell cycle process and chromosome. The down-regulated genes were enriched in folate transformations I, biosynthesis of amino acids, cellular amino acid metabolic process and vacuolar membrane. The current study screened the genes in PPI network, extracted modules, miRNA-target genes regulatory network and miRNA-target genes regulatory network with higher degrees as hub genes, which included MYC, TERF2IP, CDK1, EEF1G, TXNIP, SLC1A5, RGS4 and IER5L Survival suggested that low expressed NR4A2, SLC7 A5, CYR61 and ID1 in patients with GBM was linked with a positive prognosis for overall survival. In conclusion, the current study could improve our understanding of the molecular mechanisms in the progression of GBM, and these crucial as well as new molecular markers might be used as therapeutic targets for GBM.

Activating transcription factor 3 promotes malignance of lung cancer cells in vitro

BACKGROUND

Lung cancer remains the most common cause of cancer-related death, with high rates of recurrence and poor outcomes. An abnormally high expression of activating transcription factor 3 (ATF3) in various cancers suggests an oncogenic role; however, its function in lung cancer is largely unknown.

METHODS

Sixty-four pairs of lung cancer tissues were collected for ATF3 expression analysis by quantitative real-time PCR, immunoblotting, and immunohistochemistry staining. Correlations between ATF3 expression with clinicopathological features and overall survival were analyzed. ATF3 expression in a panel of lung cancer cell lines together with normal bronchial epithelial Beas-2B cells was also determined. Human H1299 and A549 cells were used for ATF3 knockdown and/or overexpression assays. Alterations in cell proliferation, cell cycle attribution, migration, and invasion were all assessed in vitro.

RESULTS

Increased ATF3 messenger RNA and protein expression were observed in lung cancer tissues/cells compared with normal tissues/cells. High tumorous ATF3 expression was significantly correlated with positive advanced tumor grade, lymph node metastasis, and shorter overall survival. Experimentally, we found that RNA interference mediated knockdown of ATF3 significantly inhibited the cell proliferation, cell cycle progression, migration, and invasion capacities of lung cancer cells in vitro, whereas forced expression of ATF3 did the opposite.

CONCLUSION

Upregulation of ATF3 in lung cancer promotes cell proliferation, migration, and invasion, and may represent a novel therapeutic target for lung cancer.

Cigarette smoke extract profoundly suppresses TNFα-mediated proinflammatory gene expression through upregulation of ATF3 in human coronary artery endothelial cells

Endothelial dysfunction caused by the combined action of disturbed flow, inflammatory mediators and oxidants derived from cigarette smoke is known to promote coronary atherosclerosis and increase the likelihood of myocardial infarctions and strokes. Conversely, laminar flow protects against endothelial dysfunction, at least in the initial phases of atherogenesis. We studied the effects of TNFα and cigarette smoke extract on human coronary artery endothelial cells under oscillatory, normal laminar and elevated laminar shear stress for a period of 72 hours. We found, firstly, that laminar flow fails to overcome the inflammatory effects of TNFα under these conditions but that cigarette smoke induces an anti-oxidant response that appears to reduce endothelial inflammation. Elevated laminar flow, TNFα and cigarette smoke extract synergise to induce expression of the transcriptional regulator activating transcription factor 3 (ATF3), which we show by adenovirus driven overexpression, decreases inflammatory gene expression independently of activation of nuclear factor-κB. Our results illustrate the importance of studying endothelial dysfunction in vitro over prolonged periods. They also identify ATF3 as an important protective factor against endothelial dysfunction. Modulation of ATF3 expression may represent a novel approach to modulate proinflammatory gene expression and open new therapeutic avenues to treat proinflammatory diseases.