Expression of Fra-1 in human hepatocellular carcinoma and its prognostic significance

m6A demethylation of FOSL1 mRNA protects hepatoma cells against necrosis under glucose deprivation

Stress-adaptive mechanisms enabling cancer cells to survive under glucose deprivation remain elusive. N6-methyladenosine (m6A) modification plays important roles in determining cancer cell fate and cellular stress response to nutrient deficiency. However, whether m6A modification functions in the regulation of cancer cell survival under glucose deprivation is unknown. Here, we found that glucose deprivation reduced m6A modification levels. Increasing m6A modification resulted in increased hepatoma cell necrosis under glucose deprivation, whereas decreasing m6A modification had an opposite effect. Integrated m6A-seq and RNA-seq revealed potential targets of m6A modification under glucose deprivation, including the transcription factor FOSL1; further, glucose deprivation upregulated FOSL1 by inhibiting FOSL1 mRNA decay in an m6A-YTHDF2-dependent manner through reducing m6A modification in its exon1 and 5'-UTR regions. Functionally, FOSL1 protected hepatoma cells against glucose deprivation-induced necrosis in vitro and in vivo. Mechanistically, FOSL1 transcriptionally repressed ATF3 by binding to its promoter. Meanwhile, ATF3 and MAFF interacted via their leucine zipper domains to form a heterodimer, which competed with NRF2 for binding to antioxidant response elements in the promoters of NRF2 target genes, thereby inhibiting their transcription. Consequently, FOSL1 reduced the formation of the ATF3-MAFF heterodimer, thereby enhancing NRF2 transcriptional activity and the antioxidant capacity of glucose-deprived-hepatoma cells. Thus, FOSL1 alleviated the necrosis-inducing effect of glucose deprivation-induced reactive oxygen species accumulation. Collectively, our study uncovers the protective role of m6A-FOSL1-ATF3 axis in hepatoma cell necrosis under glucose deprivation, and may provide new targets for cancer therapy.

Overexpression of FRA1 (FOSL1) Leads to Global Transcriptional Perturbations, Reduced Cellular Adhesion and Altered Cell Cycle Progression

FRA1 (FOSL1) is a transcription factor and a member of the activator protein-1 superfamily. FRA1 is expressed in most tissues at low levels, and its expression is robustly induced in response to extracellular signals, leading to downstream cellular processes. However, abnormal FRA1 overexpression has been reported in various pathological states, including tumor progression and inflammation. To date, the molecular effects of FRA1 overexpression are still not understood. Therefore, the aim of this study was to investigate the transcriptional and functional effects of FRA1 overexpression using the CGL1 human hybrid cell line. FRA1-overexpressing CGL1 cells were generated using stably integrated CRISPR-mediated transcriptional activation, resulting in a 2-3 fold increase in FRA1 mRNA and protein levels. RNA-sequencing identified 298 differentially expressed genes with FRA1 overexpression. Gene ontology analysis showed numerous molecular networks enriched with FRA1 overexpression, including transcription-factor binding, regulation of the extracellular matrix and adhesion, and a variety of signaling processes, including protein kinase activity and chemokine signaling. In addition, cell functional assays demonstrated reduced cell adherence to fibronectin and collagen with FRA1 overexpression and altered cell cycle progression. Taken together, this study unravels the transcriptional response mediated by FRA1 overexpression and establishes the role of FRA1 in adhesion and cell cycle progression.

FOS-Like Antigen 1 Expression Was Associated With Survival of Hepatocellular Carcinoma Patients

BACKGROUND

Early diagnosis and proper management of hepatocellular carcinoma (HCC) improve patient prognosis. Several studies attempted to discover new genes to understand the pathogenesis and identify the prognostic and predictive factors in HCC patients, to improve patient's overall survival (OS) and maintain their physical and social activity. The transcription factor FOS-like antigen 1 (FOSL1) acts as one of the important prognostic factors in different tumors, and its overexpression correlates with tumors' progression and worse patient survival. However, its expression and molecular mechanisms underlying its dysregulation in human HCC remain poorly understood. Our study was conducted to evaluate the expression of FOSL1 in HCC tissues and its relationship with various clinicopathological parameters besides OS.

METHODS

This study is a retrospective cohort study conducted among 113 patients with a proven diagnosis of HCC, who underwent tumor resection and received treatment at South Egypt Cancer Institute. Immunohistochemistry for FOSL1 expression and survival curves were conducted followed by statistical analysis.

RESULTS

HCC occurred at older age group and affected males more than females. There was a statistically significant correlation between combined cytoplasmic and nuclear expression of FOSL1 and worse prognosis in HCC patients. There was a statistically significant correlation of FOSL1 expression with histological grade, lymphovascular embolization, and tumor budding where high expression indicated potential deterioration of HCC patients. There was statistically significant correlation between tumor size, tumor grade and FOSL1 expression with the cumulative OS.

CONCLUSIONS

Combined cytoplasmic and nuclear FOSL1 expression has significant prognostic association with HCC and diagnostic importance, as it can identify cirrhosis and premalignant lesions that can progress to HCC. Furthermore, Kaplan-Meier survival analysis found that overexpressed FOSL1 was correlated with poor OS.

MiR-33a targets FOSL1 and EN2 as a clinical prognostic marker for sarcopenia by glioma

To determine the relationship between glioma and muscle aging and to predict prognosis by screening for co-expressed genes, this study examined the relationship between glioma and sarcopenia. The study identified eight co-downregulated miRNAs, three co-upregulated miRNAs, and seven genes associated with overall glioma survival, namely, KRAS, IFNB1, ALCAM, ERBB2, STAT3, FOSL1, and EN2. With a multi-factor Cox regression model incorporating FOSL1 and EN2, we obtained ROC curves of 0.702 and 0.709, respectively, suggesting that glioma prognosis can be predicted by FOSL1 and EN2, which are differentially expressed in both cancer and aged muscle. FOSL1 and EN2 were analyzed using Gene Set Enrichment Analysis to identify possible functional pathways. RT-qPCR and a dual-luciferase reporter gene system verified that hsa-miR-33a targets FOSL1 and EN2. We found that hsa-mir-33a co-targeting FOSL1 and EN2 has a good predictive value for glioblastoma and skeletal muscle reduction.

FRA-1: A key factor regulating signal transduction of tumor cells and a potential target molecule for tumor therapy

Fos-related antigen-1 (FRA-1) is a member of activator protein-1 (AP-1) transcription factor superfamily, and FRA-1 is highly expressed in colon cancer, breast cancer, gastric cancer, lung cancer, bladder cancer, and other tumors. The expression level of FRA-1 is closely related to the processes of tumor cell proliferation, apoptosis, transformation, migration, and invasion, which is a potential therapeutic target and prognostic factor for many tumors. Clarifying the detailed mechanism of action of FRA-1 could provide the theoretical basis for tumor diagnosis, treatment, and prognosis, and is of great significance for the study of tumor etiology and pathogenesis. In this paper, the expression levels and influencing factors of FRA-1 in various tumor tissues and cells are summarized, as well as the effect of FRA-1 expression level on the biological behavior of tumor cells and the signal transduction mechanism. At the same time, the signal transduction mechanism of FRA-1 in inflammation was expounded. In addition, the related metabolites, drugs and non-coding RNA that affect the expression and function of FRA-1 were summarized. Finally, it illustrates that FRA-1 may be taken as a key factor for tumor prognosis and a potential therapeutic target. This review provides a theoretical basis for the systematic understanding of the relationship between FRA-1 and tumors, its function, and possible mechanism.

NF1 regulates mesenchymal glioblastoma plasticity and aggressiveness through the AP-1 transcription factor FOSL1

The molecular basis underlying glioblastoma (GBM) heterogeneity and plasticity is not fully understood. Using transcriptomic data of human patient-derived brain tumor stem cell lines (BTSCs), classified based on GBM-intrinsic signatures, we identify the AP-1 transcription factor FOSL1 as a key regulator of the mesenchymal (MES) subtype. We provide a mechanistic basis to the role of the neurofibromatosis type 1 gene (NF1), a negative regulator of the RAS/MAPK pathway, in GBM mesenchymal transformation through the modulation of FOSL1 expression. Depletion of FOSL1 in NF1-mutant human BTSCs and Kras-mutant mouse neural stem cells results in loss of the mesenchymal gene signature and reduction in stem cell properties and in vivo tumorigenic potential. Our data demonstrate that FOSL1 controls GBM plasticity and aggressiveness in response to NF1 alterations.

A Review of the Pharmacological Properties of Psoralen

Psoralen is the principal bioactive component in the dried fruits of Cullen corylifolium (L.) Medik (syn. Psoralea corylifolia L), termed "Buguzhi" in traditional Chinese medicine (TCM). Recent studies have demonstrated that psoralen displays multiple bioactive properties, beneficial for the treatment of osteoporosis, tumors, viruses, bacteria, and inflammation. The present review focuses on the research evidence relating to the properties of psoralen gathered over recent years. Firstly, multiple studies have demonstrated that psoralen exerts strong anti-osteoporotic effects via regulation of osteoblast/osteoclast/chondrocyte differentiation or activation due to the participation in multiple molecular mechanisms of the wnt/β-catenin, bone morphogenetic protein (BMP), inositol-requiring enzyme 1 (IRE1)/apoptosis signaling kinase 1 (ASK1)/c-jun N-terminal kinase (JNK) and the Protein Kinase B(AKT)/activator protein-1 (AP-1) axis, and the expression of miR-488, peroxisome proliferators-activated receptor-gamma (PPARγ), and matrix metalloproteinases (MMPs). In addition, the antitumor properties of psoralen are associated with the induction of ER stress-related cell death via enhancement of PERK: Pancreatic Endoplasmic Reticulum Kinase (PERK)/activating transcription factor (ATF), 78kD glucose-regulated protein (GRP78)/C/EBP homologous protein (CHOP), and 94kD glucose-regulated protein (GRP94)/CHOP signaling, and inhibition of P-glycoprotein (P-gp) or ATPase that overcomes multidrug resistance. Furthermore, multiple articles have shown that the antibacterial, anti-inflammatory and neuroprotective effects of psoralen are a result of its interaction with viral polymerase (Pol), destroying the formation of biofilm, and regulating the activation of tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), interleukin 4/5/6/8/12/13 (IL-4/5/6/8/12/13), GATA-3, acetylcholinesterase (AChE), and the hypothalamic-pituitary-adrenal (HPA) axis. Finally, the toxic effects and mechanisms of action of psoralen have also been reviewed.

Expression and function of FRA1 protein in tumors

AP-1 is a dimeric complex that is composed of JUN, FOS, ATF and MAF protein families. FOS-related antigen 1 (FRA1) which encoded by FOSL1 gene, belongs to the FOS protein family, and mainly forms an AP-1 complex with the protein of the JUN family to exert an effect. Regulation of FRA1 occurs at levels of transcription and post-translational modification, and phosphorylation is the major post-translational modification. FRA1 is mainly regulated by the mitogen-activated protein kinases signaling pathway and is degraded by ubiquitin-independent proteasomes. FRA1 can affect biological functions, such as tumor proliferation, differentiation, invasion and apoptosis. Studies have demonstrated that FRA1 is abnormally expressed in many tumors and plays a relevant role, but the specific condition varies from the target organs. FRA1 is overexpressed in breast cancer, lung cancer, colorectal cancer, prostate cancer, nasopharyngeal cancer, thyroid cancer and other tumors. However, the expression of FRA1 is decreased in cervical cancer, and the expression of FRA1 in ovarian cancer and oral squamous cell carcinoma is still controversial. In this review, we present a detailed description of the regulatory factors and functions of FRA1, also, the expression of FRA1 in various tumors and its function in relative tumor.

Fra-1 and c-Fos N-Terminal Deletion Mutants Impair Breast Tumor Cell Proliferation by Blocking Lipid Synthesis Activation

Tumor cells require high rates of lipid synthesis to support membrane biogenesis for their exacerbated growth. The only two proteins known that activate phospholipid synthesis are Fra-1 and c-Fos, two members of the AP-1 family of transcription factors. These proteins that are overexpressed in human breast malignant tumors increase the rate of phospholipid synthesis at the endoplasmic reticulum through a mechanism independent of their nuclear function. The aim of this study was to inhibit breast tumor cell proliferation by modulating c-Fos and Fra-1 and regulate membrane biogenesis by controlling lipid synthesis rates. The molecular mechanism by which Fra-1 and c-Fos activate phospholipid synthesis was examined. Both proteins physically associate with the rate limiting enzyme CDP-DAG synthase through their N-terminus domain and activate it through their basic domain; neither protein associates to or activates the enzyme phosphatidylinositol synthase as determined through in vitro enzymatic reactions and FRET experiments. The N-terminus domain of both proteins act as negative dominant peptides that physically associate with CDP-DAG synthase but do not activate it. Proliferation of MDA-MB231 and 4T1 cells was impaired in vitro after inducing them to proliferate in the presence of the negative dominant peptides derived from Fra-1 and c-Fos. When tumors generated in Balb/c mice with the breast tumor cell line 4T1 were treated with these negative dominant peptides, a significant reduction in tumor growth was observed. Consequently, these Fra-1 and c-Fos negative dominant peptides can be exploited as a new therapeutic strategy to impair breast tumor cell proliferation.

Psoralen induced cell cycle arrest by modulating Wnt/β-catenin pathway in breast cancer cells

Psoralen could inhibit the proliferation of human breast cancer cells, however, the molecular mechanism was unclear. We evaluated the anti-proliferative effects of psoralen by MTT, plate colony formation assay and cell cycle analysis in MCF-7 and MDA-MB-231 cells. The effects of psoralen on activation of Wnt/β-catenin and the related target genes were examined by quantitative real-time PCR, western blotting and cell immunofluorescence. The tumor growth was conducted in BALB/c nude mice and the pathological changes of heart, liver and kidney were also observed. Our results demonstrate that psoralen significantly inhibited cell proliferation by inducing G0/G1 phase arrest in MCF-7 cells and G2/M phase arrest in MDA-MB-231 cells. The expression of Fra-1 was reduced and Axin2 was promoted both in MCF-7 and MDA-MB-231 cells after psoralen treatment. The cytoplasmic accumulation and nuclear translocation of β-catenin were significantly reduced by psoralen. Psoralen increased the levels of phospho-(Y142) β-catenin, while decreased the expression of total β-catenin and its downstream target Fra-1 in vitro and vivo. Moreover, psoralen didn’t cause any significant toxicity at the effective concentration. Overall, our results might provide theoretical basis for clinical application of psoralen in breast cancer.

FOSL1 Promotes Kras-induced Lung Cancer through Amphiregulin and Cell Survival Gene Regulation

The FOSL1/AP-1 transcription factor regulates gene expression, thereby controlling various pathophysiological processes. It is a major effector of RAS-ERK1/2 signaling and is activated in human lung epithelia by tumorigenic stimuli. Recent evidence shows an inverse correlation between FOSL1 expression and the survival of patients with lung cancer and adenocarcinomas; however, its role in lung tumorigenesis remains elusive. In this work, we sought to determine the role of FOSL1 in Kras-induced lung adenocarcinoma in vivo and its downstream effector mechanisms. We used mice expressing the Kras oncogene in the lung with concomitant Fosl1 deletion, Kras-activated murine alveolar epithelial cells (mAECs) with Fosl1 deletion, and KRAS mutant human lung adenocarcinoma (HLAC) cells with FOSL1 deficiency, and performed cell proliferation and gene expression analyses. Mutant Kras induced Fosl1 expression in vitro (mAECs) and in vivo (lung tissue), and mice with Fosl1 deletion showed reduced levels of mutant Kras-induced lung tumorigenesis and survived longer than Fosl1-sufficient mice. Studies with mutant Kras-activated mAECs and KRAS-mutant HLAC cells revealed that FOSL1 regulates mutant KRAS-induced gene expression, thereby controlling cell proliferation and survival. In contrast, FOSL1 depletion in non-KRAS-mutant HLAC cells and nonmalignant human lung epithelia had no effect. Our data support the notion that FOSL1-mediated expression of amphiregulin and apoptotic and antioxidative genes plays a role in regulating HLAC cell proliferation and survival. FOSL1 is a determinant of lung cancer in vivo and regulates HLAC cell proliferation and survival, largely in the context of KRAS mutations. Activation of FOSL1 in adenocarcinomas may be a prognostic marker and potential target for human lung cancer with KRAS mutations.