Identification and Validation of ATF3 Serving as a Potential Biomarker and Correlating With Pharmacotherapy Response and Immune Infiltration Characteristics in Rheumatoid Arthritis

Background: Although disease-modifying antirheumatic drugs (DMARDs) have significantly improved the prognosis of patients with rheumatoid arthritis (RA), approximately 40% of RA patients have limited response. Therefore, it was essential to explore new biomarkers to improve the therapeutic effects on RA. This study aimed to develop a new biomarker and validate it by an in vitro study.Methods: The RNA-seq and the clinicopathologic data of RA patients were downloaded from Gene Expression Omnibus (GEO) databases. Differentially expressed genes were screened in the GPL96 and GPL570 databases. Then, weighted gene co-expression network analysis (WGCNA) was used to explore the most correlated gene modules to normal and RA synovium in the GPL96 and GPL570 databases. After that, the differentially expressed genes were intersected with the correlated gene modules to find the potential biomarkers. The CIBERSORT tool was applied to investigate the relationship between activated transcription factor 3 (ATF3) expression and the immune cell infiltration, and Gene Set Enrichment Analysis (GSEA) was used to investigate the related signaling pathways of differentially expressed genes in the high and low ATF3 groups. Furthermore, the relationships between ATF3 expression and clinical parameters were also explored in the GEO database. Finally, the role of ATF3 was verified by in vitro cell experiments.Results: We intersected the differentially expressed genes and the most correlated gene modules in the GPL570 and GPL96 databases and identified that ATF3 is a significant potential biomarker and correlates with some clinical–pharmacological variables. Immune infiltration analysis showed that activated mast cells had a significant infiltration in the high ATF3 group in the two databases. GSEA showed that metabolism-associated pathways belonged to the high ATF3 groups and that inflammation and immunoregulation pathways were enriched in the low ATF3 group. Finally, we validated that ATF3 could promote the proliferation, migration, and invasion of RA fibroblast-like synoviocyte (FLS) and MH7A. Flow cytometry showed that ATF3 expression could decrease the proportion of apoptotic cells and increase the proportion of S and G2/M phase cells.Conclusion: We successfully identified and validated that ATF3 could serve as a novel biomarker in RA, which correlated with pharmacotherapy response and immune cell infiltration.

Forkhead Box Protein P3 (FOXP3) Represses ATF3 Transcriptional Activity

Activating transcription factor 3 (ATF3), a transcription factor and acute stress sensor, is rapidly induced by a variety of pathophysiological signals and is essential in the complex processes in cellular stress response. FOXP3, a well-known breast and prostate tumor suppressor from the X chromosome, is a novel transcriptional repressor for several oncogenes. However, it remains unknown whether ATF3 is the target protein of FOXP3. Herein, we demonstrate that ATF3 expression is regulated by FOXP3. Firstly, we observed that overexpression of FOXP3 reduced ATF3 protein level. Moreover, knockdown FOXP3 by siRNA increased ATF3 expression. Secondly, FOXP3 dose-dependently reduced ATF3 promoter activity in the luciferase reporter assay. Since FOXP3 is regulated by post-translational modifications (PTMs), we next investigated whether PTMs affect FOXP3-mediated ATF3 expression. Interestingly, we observed that phosphorylation mutation on FOXP3 (Y342F) significantly abolished FOXP3-mediated ATF3 expression. However, other PTM mutations on FOXP3, including S418 phosphorylation, K263 acetylation and ubiquitination, and K268 acetylation and ubiquitination, did not alter FOXP3-mediated ATF3 expression. Finally, the FOXP3 binding site was found on ATF3 promoter region by deletion and mutagenesis analysis. Taken together, our results suggest that FOXP3 functions as a novel regulator of ATF3 and that this novel event may be involved in tumor development and progression.

Induction of ferroptosis by ATF3 elevation alleviates cisplatin resistance in gastric cancer by restraining Nrf2/Keap1/xCT signaling

Background Currently, resistance against cisplatin (DDP) is a frequent problem for the success of advanced gastric carcinoma (GC) chemotherapy. Here, we sought to investigate the function of activating transcription factor 3 (ATF3) n GC chemoresistance. Methods Expression of ATF3 was determined in GC cell lines (MNK45, SGC7901, and BGC823) and cisplatin (DDP)-resistant cells (SGC7901/DDP and BGC823/DDP). Biological informatics was performed to analyze ATF3 expression and prognosis in GC patients. Cisplatin resistance was evaluated. Ferroptosis was detected after ATF3 transfection of cells. The underlying molecular mechanism was also investigated. Results Transcripts of ATF3 were decreased in GC cells and GC tissues. Kaplan–Meier plotter analysis revealed that ATF3 expression was positively related to the overall survival of GC patients. In particular, lower levels of ATF3 were observed in cisplatin-resistant SGC7901/DDP and BGC823/DDP relative to their parental cells. Notably, ATF3 elevation sensitized cisplatin-resistant cells to cisplatin. Mechanically, compared with parental cells, SGC7901/DDP and BGC823/DDP cells exhibited lower ferroptosis evident by lower ROS, MDA and lipid peroxidation and higher intracellular GSH levels. However, ATF3 elevated ferroptosis in SGC7901/DDP and BGC823/DDP cells. Intriguingly, ATF3 overexpression together with ferroptosis activator erastin or RSL3 treatment further enhanced ferroptosis and cisplatin resistance; however, the ferroptosis suppressor liproxstatin-1 reversed the function of ATF3 in ferroptosis and cisplatin resistance. Additionally, cisplatin-resistant cells exhibited stronger activation of Nrf2/Keap1/xCT signaling relative to parental cells, which was restrained by ATF3 up-regulation. Importantly, restoring Nrf2 signaling overturned ATF3-mediated ferroptosis and cisplatin resistance. Conclusion ATF3 may sensitize GC cells to cisplatin by induction of ferroptosis via blocking Nrf2/Keap1/xCT signaling, supporting a promising therapeutic approach for overcoming chemoresistance in GC.

ATF3 deficiency impairs the proliferative–secretory phase transition and decidualization in RIF patients

Decidualization is a complex process involving cellular proliferation and differentiation of the endometrial stroma and is required to establish and support pregnancy. Dysregulated decidualization has been reported to be a critical cause of recurrent implantation failure (RIF). In this study, we found that Activating transcription factor 3 (ATF3) expression was significantly downregulated in the endometrium of RIF patients. Knockdown of ATF3 in human endometrium stromal cells (hESCs) hampers decidualization, while overexpression could trigger the expression of decidual marker genes, and ameliorate the decidualization of hESCs from RIF patients. Mechanistically, ATF3 promotes decidualization by upregulating FOXO1 via suppressing miR-135b expression. In addition, the endometrium of RIF patients was hyperproliferative, while overexpression of ATF3 inhibited the proliferation of hESCs through CDKN1A. These data demonstrate the critical roles of endometrial ATF3 in regulating decidualization and proliferation, and dysregulation of ATF3 in the endometrium may be a novel cause of RIF and therefore represent a potential therapeutic target for RIF.

ATF3 Suppresses Growth and Metastasis of Clear Cell Renal Cell Carcinoma by Deactivating EGFR/AKT/GSK3β/β-Catenin Signaling Pathway

BackgroundClear cell renal cell carcinoma (ccRCC) is one of the most common malignant cancers in East Asia, with high incidence and mortality. Accumulating evidence has shown that ATF3 is associated with tumor progression.MethodsUsing qPCR, the expression of ATF3 was detected in 93 patients with ccRCC, including 24 paired normal and tumor tissues, which were used to further compare ATF3 expression through western blotting and immunohistochemistry. Lentivirus was used for the overexpression or knockdown of ATF3, and the consequent alteration in function was analyzed through CCK8 assay, colony formation assay, wound healing assay, invasion assay, and flow cytometry. The potential mechanism affected by ATF3 was analyzed through gene set enrichment analysis (GSEA) and verified using western blotting, invasion assay, or immunofluorescence staining. Furthermore, a xenograft mouse model was used to assess the function of ATF3 in vivo.ResultsATF3 expression was significantly decreased in ccRCC compared to that in adjacent normal tissues. Through gain- and loss-of-function experiments performed in an in vitro assay, we found that ATF3 could regulate ccRCC cell proliferation, cycle progression, migration, and invasion. In the in vivo study, the xenograft mouse model revealed that ATF3 overexpression can inhibit the growth of ccRCC. Moreover, the mechanism analysis showed that suppression of ATF3 could lead to an increase the expression of β-catenin and promote β-catenin transfer to the nucleus, and might be affected by EGFR/AKT/GSK3β signaling.ConclusionATF3 could be utilized as an independent protective factor to inhibit the progression of ccRCC. Potential treatment strategies for ccRCC include targeting the ATF3/EGFR/AKT/GSK3β/β−catenin signaling pathway.

Abstract P795: Activating Transcription Factor 3 Improves Stroke Recovery Through Reduction of Neuronal Damage and Neuroinflammation

Background and Purpose: Activating transcription factor 3 (ATF3), a member of the ATF/CREB family, is upregulated in the early phase of various stresses including ischemic stroke. The role of ATF3 in ischemic stroke injury has not been fully elucidated. Hypothesis: ATF3 improves stroke outcomes through reduction of neuronal damage and neuroinflammation. Methods: Permanent distal middle cerebral artery occlusion (pMCAO) was performed in 8-week-old male and female C57BL/6J (WT) and ATF3 knockout (ATF3 -/- ) mice. The sensorimotor functions were analyzed 3 days after pMCAO through adhesive removal and corner tests. Infarct volumes and injured neurons were quantified on Nissl stained and Fluoro-Jade C (FJC) stained sections. The cell-specific expression of ATF3 was analyzed by co-staining ATF3 antibody with antibodies specific to NeuN (Neuron), CD68 (microglia/macrophage) and GFAP (astrocyte). The expression of ATF3 in injured neurons was analyzed by ATF3 and FJC double labeling. Results: ATF3 expression was detected exclusively in neurons in the infarct area 1 day after pMCAO. There were a few ATF3 + CD68 + microglia/macrophages at the peri-infarct regions 2 and 3 days after pMCAO. Almost all FJC + neurons were ATF3 positive. No ATF3 expression was detected in astrocytes. Compared to WT mice, ATF3 -/- mice took longer time to remove the adhesive from their right paws (p<0.001) in adhesive removal test and more left turns in corner test (p<0.001) 3 days after pMCAO. ATF3 -/- mice also had a larger infarct volume (p = 0.014), more FJC + neurons (p=0.002) and CD68 + microglia/macrophages (p=0.003) in the peri-infarct regions than WT mice. Conclusions: Deletion of ATF3 exacerbates neuronal injury, neuroinflammation, and sensorimotor dysfunction in stroke mice, suggesting that upregulation of ATF3 at early stage of stroke improves ischemic stroke recovery through reduction of neuronal damage and neuroinflammation.

Role of ATF3 as a prognostic biomarker and correlation of ATF3 expression with macrophage infiltration in hepatocellular carcinoma

Background The abnormal expression of activating transcription factor 3 (ATF3), a member of the basic leucine zipper (bZIP) family of transcription factors, is associated with carcinogenesis. However, the expression pattern and exact role of ATF3 in the development and progression of hepatocellular carcinoma (HCC) remain unclear. Methods We used UALCAN, ONCOMINE, Kaplan–Meier plotter, and cBioPortal databases to investigate the prognostic value of ATF3 expression in HCC. Results ATF3 was found to be expressed at low levels in multiple HCC tumor tissues. Moreover, low ATF3 expression was significantly associated with clinical cancer stage and pathological tumor grade in patients with HCC. Therefore, low expression of ATF3 was significantly associated with poor overall survival in patients with HCC. Functional network analysis showed that ATF3 regulates cytokine receptors and signaling pathways via various cancer-related kinases, miRNAs, and transcription factors. ATF3 expression was found to be correlated with macrophage infiltration levels and with macrophage immune marker sets in HCC patients. Conclusions Using data mining methods, we clarified the role of ATF3 expression and related regulatory networks in HCC, laying a foundation for further functional research. Future research will validate our findings and establish clinical applications of ATF3 in the diagnosis and treatment of HCC.

ASC-J9® suppresses prostate cancer cell proliferation and invasion via altering the ATF3-PTK2 signaling

Background Early studies indicated that ASC-J9®, an androgen receptor (AR) degradation enhancer, could suppress the prostate cancer (PCa) progression. Here we found ASC-J9® could also suppress the PCa progression via an AR-independent mechanism, which might involve modulating the tumor suppressor ATF3 expression. Methods The lentiviral system was used to modify gene expression in C4–2, CWR22Rv1 and PC-3 cells. Western blot and Immunohistochemistry were used to detect protein expression. MTT and Transwell assays were used to test the proliferation and invasion ability. Results ASC-J9® can suppress PCa cell proliferation and invasion in both PCa C4–2 and CWR22Rv1 cells via altering the ATF3 expression. Further mechanistic studies reveal that ASC-J9® can increase the ATF3 expression via decreasing Glutamate-cysteine ligase catalytic (GCLC) subunit expression, which can then lead to decrease the PTK2 expression. Human clinical studies further linked the ATF3 expression to the PCa progression. Preclinical studies using in vivo mouse model also proved ASC-J9® could suppress AR-independent PCa cell invasion, which could be reversed after suppressing ATF3. Conclusions ASC-J9® can function via altering ATF3/PTK2 signaling to suppress the PCa progression in an AR-independent manner.

Role of ATF3 as a prognostic biomarker and correlation of ATF3 expression with macrophage infiltration in hepatocellular carcinoma

Background: The abnormal expression of activating transcription factor 3 (ATF3), a member of the basic leucine zipper (bZIP) family of transcription factors, is associated with carcinogenesis. However, the expression pattern and exact role of ATF3 in the development and progression of hepatocellular carcinoma (HCC) remain unclear. Methods: We used UALCAN, ONCOMINE, Kaplan-Meier plotter, and cBioPortal databases to investigate the prognostic value of ATF3 expression in HCC. Results: ATF3 was found to be expressed at low levels in multiple HCC tumor tissues. Moreover, low ATF3 expression was significantly associated with clinical cancer stage and pathological tumor grade in patients with HCC. Therefore, low expression of ATF3 was significantly associated with poor overall survival in patients with HCC. Functional network analysis showed that ATF3 regulates cytokine receptors and signaling pathways via various cancer-related kinases, miRNAs, and transcription factors. ATF3 expression was found to be correlated with macrophage infiltration levels and with macrophage immune marker sets in HCC patients. Conclusions: Using data mining methods, we clarified the role of ATF3 expression and related regulatory networks in HCC, laying a foundation for further functional research. Future research will validate our findings and establish clinical applications of ATF3 in the diagnosis and treatment of HCC.