Fra-1 Expression Research Articles

Fra-1 affects chemotherapy sensitivity by inhibiting ferroptosis in gastric cancer cells.

Aim: Gastric cancer (GC) is one of the common malignant tumors, and most patients with advanced GC often develop chemotherapy resistance, resulting in poor chemotherapy efficacy. Therefore, it is crucial to clarify the specific mechanisms of their chemotherapy resistance. Methods: In this study, we analyzed the correlation between fos-related antigen-1 (Fra-1) and chemotherapy resistance in GC using bioinformatics, cell counting kit-8 (CCK8), and 5-ethynyl-2'-deoxyuridine (EDU) combined with flow cytometry; furthermore, we used energy metabolomics sequencing, combined with ChIP-qPCR technology, to elucidate the specific role of Fra-1 in chemotherapy resistance of GC cells and its related mechanisms. Results: We found that high Fra-1 expression was closely related to chemotherapeutic drugs in GC cells, as demonstrated by bioinformatics analysis combined with EDU and CCK8 experiments. Energy metabolomics combined with in vitro cellular experimental analysis revealed that the pentose phosphate pathway (PPP) was activated in GC cells with high Fra-1 expression, along with an increase in the synthesis of metabolites such as nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH), a decrease in the level of reactive oxygen species (ROS), and the inhibition of their ferroptosis. In addition, ChIP-qPCR experiments confirmed that Fra-1 binds to the promoter of glucose-6-phosphate dehydrogenase (G6PD), a key rate-limiting enzyme of the PPP, and transcriptionally regulates its expression, which in turn activates the PPP and promotes chemotherapy resistance in GC cells. Conclusion: Our research findings suggest that Fra-1 activates the PPP by upregulating G6PD transcriptional activity and inhibiting its ubiquitination level, inhibiting ferroptosis in GC cells and inducing chemoresistance. This provides an experimental basis for screening potential molecular targets for chemotherapy resistance in GC patients.

Expression of Wnt signaling proteins in rare congenital bladder disorders

Introduction and AimsCongenital bladder anomalies are rare and are a leading cause of end stage renal failure in children. The Wnt signaling pathway, important during embryonic development, has been implicated in the pathogenesis of these conditions through regulation of gene expression, including essential transcription factors. We investigated the expression of four Wnt transcriptional targets, namely, Pygopus 1 (Pygo1), FRA1, TCF7L1 and Connexin 43 (Cx43) in three rare congenital bladder disorders: bladder exstrophy (BE), neurogenic bladder (NGB) and posterior urethral valves (PUV). MethodsBladder tissue samples were collected from patients at the Great Ormond Street Hospital for Sick Children, London, UK, with control (normally-functioning bladder, N=9), BE (N=15), NGB (N=6) and PUV (N=5). Histological analysis was performed using the van Gieson stain to differentiate smooth muscle (SM) and connective tissue (CT) compartments. An unbiased, automated, semi-quantitative immunofluorescence analysis was performed to measure the labelling intensity of four Wnt-related proteins in tissue from these four groups. Results and DiscussionThere was a significant (p<0.05) increase in the expression of Pygo1 in the smooth muscle of all anomalies examined and also in the connective tissue in PUV compared to control. Cx43 also showed overexpression in the smooth muscle across all conditions; however, there was a reduced expression in NGB and an increase in PUV in connective tissue. TCF7L1 showed a significant decrease in both tissue compartments for NGB, whereas FRA1 expression remained unchanged across all anomalies. We also measured colocalization of Wnt-related proteins. TCF7L1 exhibited increased colocalization with Pygo1 and FRA1 in exstrophy compared to control. These results suggest a complex dysregulation of the Wnt pathway in congenital bladder disorders. ConclusionWnt signaling-related proteins show dysregulation in congenital bladder disorders compared to control tissue. Understanding these mechanisms should help towards non-invasive early diagnosis, drug target discovery and development of treatment strategies for these conditions.Summary tableSummary of Wnt-related protein expression and colocalization in bladder exstrophy (BE), neurogenic bladder (NGB) and posterior urethral valves (PUV) disorder compared to normally-functioning control bladder. The table shows the levels of expression as significantly up (↑) down (↓) or no change (-) of Pygopus 1 (Pygo1), Connexin 43 (Cx43), FRA1 and TCF7L1 expression in smooth muscle and connective tissue compartments in BE, NGB and PUV relative to control bladder tissue samples. The table also shows colocalization of six protein pairs of Pygo1 and FRA1; Pygo1 and Cx43; Pygo1 and TCF7L1; FRA1 and Cx43; FRA1 and TCF7L1 and Cx43 and TCF7L1 in bladder disorders compared to control.Summary tableProtein Expression (Smooth muscle)Pygo1Cx43FRA1TCF7L1BE↑↑--NGB↑↑-↓PUV↑↑--Protein Expression (Connective tissue)BE----NGB-↓-↓PUV↑↑--ColocalizationPygo1/FRA1Pygo1/Cx43Pygo1/TCF7L1FRA1/Cx43FRA1/TCF7L1Cx43/TCF7L1Exstrophy--↑-↑-NGB------PUV------

Saikosaponin A Recovers Impaired Filaggrin Levels in Inflamed Skin by Downregulating the Expression of FRA1 and c-Jun.

Filaggrin (FLG) is an essential structural protein expressed in differentiated keratinocytes. Insufficient FLG expression contributes to the pathogenesis of chronic inflammatory skin diseases. Saikosaponin A (SSA), a bioactive oleanane-type triterpenoid, exerts anti-inflammatory activity. However, the effects of topically applied SSA on FLG expression in inflamed skin remain unclear. This study aimed to evaluate the biological activity of SSA in restoring reduced FLG expression. The effect of SSA on FLG expression in HaCaT cells was assessed through various biological methods, including reverse transcription PCR, quantitative real-time PCR, immunoblotting, and immunofluorescence staining. TNFα and IFNγ decreased FLG mRNA, cytoplasmic FLG protein levels, and FLG gene promoter-reporter activity compared to the control groups. However, the presence of SSA restored these effects. A series of FLG promoter-reporter constructs were generated to investigate the underlying mechanism of the effect of SSA on FLG expression. Mutation of the AP1-binding site (mtAP1) in the -343/+25 FLG promoter-reporter abrogated the decrease in reporter activities caused by TNFα + IFNγ, suggesting the importance of the AP1-binding site in reducing FLG expression. The SSA treatment restored FLG expression by inhibiting the expression and nuclear localization of FRA1 and c-Jun, components of AP1, triggered by TNFα + IFNγ stimulation. The ERK1/2 mitogen-activated protein kinase signaling pathway upregulates FRA1 and c-Jun expression, thereby reducing FLG levels. The SSA treatment inhibited ERK1/2 activation caused by TNFα + IFNγ stimulation and reduced the levels of FRA1 and c-Jun proteins in the nucleus, leading to a decrease in the binding of FRA1, c-Jun, p-STAT1, and HDAC1 to the AP1-binding site in the FLG promoter. The effect of SSA was evaluated in an animal study using a BALB/c mouse model, which induces human atopic-dermatitis-like skin lesions via the topical application of dinitrochlorobenzene. Topically applied SSA significantly reduced skin thickening, immune cell infiltration, and the expression of FRA1, c-Jun, and p-ERK1/2 compared to the vehicle-treated group. These results suggest that SSA can effectively recover impaired FLG levels in inflamed skin by preventing the formation of the repressor complex consisting of FRA1, c-Jun, HDAC1, and STAT1.

Progress in the Study of Fra-2 in Respiratory Diseases.

Fos-related antigen-2 (Fra-2) is a member of the activating protein-1 (AP-1) family of transcription factors. It is involved in controlling cell growth and differentiation by regulating the production of the extracellular matrix (ECM) and coordinating the balance of signals within and outside the cell. Fra-2 is not only closely related to bone development, metabolism, and immune system and eye development but also in the progression of respiratory conditions like lung tumors, asthma, pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD). The increased expression and activation of Fra-2 in various lung diseases has been shown in several studies. However, the specific molecular mechanisms through which Fra-2 affects the development of respiratory diseases are not yet understood. The purpose of this research is to summarize and delineate advancements in the study of the involvement of transcription factor Fra-2 in disorders related to the respiratory system.

The IL-33-ST2 axis plays a vital role in endometriosis via promoting epithelial–mesenchymal transition by phosphorylating β-catenin

ObjectivesInterleukin 33 (IL-33) is a crucial inflammatory factor that functions as an alarm signal in endometriosis (EMs). Epithelial-mesenchymal transition (EMT), a process related to inflammatory signals, intracellular reactive oxygen species (ROS) production, and lipid peroxidation, have been proposed as potential mechanisms that contribute to the development and progression of EMs. IL-33 is highly upregulated in the ectopic milieu. Moreover, ectopic endometrial cells constitutively express interleukin-33 receptor ST2 (IL-33R). However, the role of IL-33/ST2 in the EMT of EMs remains largely unknown. In this study, we aimed to mechanistically determine the role of IL-33/ST2 in EMs-associated fibrosis.Materials and methodsWe established a non-lethal oxidative stress model to explore the conditions that trigger IL-33 induction. We performed α-smooth muscle actin (α-SMA) protein detection, cell counting kit-8 (CCK-8) assays, and scratch assays to analyze the impact of IL-33 on primary endometrial stromal cells (ESCs) proliferation and invasion. Clinical samples from patients with or without EMs were subjected to immunohistochemical (IHC) and and immunofluorescence(IF) staining to assess the clinical relevance of IL-33 receptor ST2 and EMT-related proteins. Furthermore, we used the ectopic human endometrial epithelial cell line 12Z and normal human epithelial cell line EEC to evaluate the effects of IL-33 on Wnt/β-catenin signaling. The effect of IL-33 on EMT-associated fibrosis was validated in vivo by intraperitoneal injections of IL-33 and antiST2.ResultsWe observed that ectopic milieu, characterized by ROS, TGF-β1, and high level of estrogen, triggers the secretion of IL-33 from ectopic ESCs. Ectopic endometrial lesions exhibited higher level of fibrotic characteristics and ST2 expression than that in the normal endometrium. Exogenous recombinant human (rhIL-33) enhanced ESC migration and survival. Similarly, 12Z cells displayed a higher degree of EMT characteristics with elevated expression of CCN4 and Fra-1, downstream target genes of the WNT/β-catenin pathway, than that observed in EECs. Conversely, blocking IL-33 with neutralizing antibodies, knocking down ST2 or β-catenin with siRNA, and β-catenin dephosphorylation abolished its effects on EMT promotion. In vivo validation demonstrated that IL-33 significantly promotes EMs-related fibrosis through the activation of Wnt/β-catenin signaling.ConclusionOur data strongly support the vital role of the IL-33/ST2 pathway in EMs-associated fibrosis and emphasize the importance of the EMT in the pathophysiology of fibrosis. Targeting the IL-33/ST2/Wnt/β-catenin axis may hold promise as a feasible therapeutic approach for controlling fibrosis in EMs.

AP-1/C-FOS and AP-1/FRA2 differentially regulate early and late adipogenic differentiation of mesenchymal stem cells.

Obesity is defined as an abnormal accumulation of adipose tissue in the body and is a major global health problem due to increased morbidity and mortality. Adipose tissue is made up of adipocytes, which are fat-storing cells, and the differentiation of these fat cells is known as adipogenesis. Several transcription factors (TFs)such as CEBPβ, CEBPα, PPARγ, GATA, and KLFhave been reported to play a key role in adipogenesis. In this study, we report one more TFAP-1, which is found to be involved in adipogenesis. Human mesenchymal stem cells were differentiated into adipocytes, and the expression pattern of different subunits of AP-1 was examined during adipogenesis. It was observed that C-FOS was predominantly expressed at an early stage (Day 2), whereas FRA2 expression peaked at later stages (Days 6 and 8) of adipogenesis. Chromatin immunoprecipitation-sequencing analysis revealed that C-FOS binds mainly to the promoters of WNT1, miR-30a, and ANAPC7and regulates their expression during mitotic clonal expansion. In contrast, FRA2 binds to the promoters of CIDEA, NOTCH1, ARAF, and MYLK, regulating their expression and lipid metabolism. Data obtained clearly indicatethat the differential expression of C-FOS and FRA2 is crucial for different stages of adipogenesis. This also raises the possibility of considering AP-1 as a therapeutic target for treating obesity and related disorders.

1281P Effect of Fra-2 expression on tumour immunogenicity and prognosis in KRAS-mutant lung adenocarcinoma

1281P Effect of Fra-2 expression on tumour immunogenicity and prognosis in KRAS-mutant lung adenocarcinoma

CHRONIC DYSREGULATION OF GLUTAMATERGIC TRANSMISSION IN THE HIPPOCAMPUS OF KRUSHINSKY–MOLODKINA RATS INDUCED BY REPEATED EPILEPTIFORM SEIZURES

Temporal lobe epilepsy is characterised by the development of associated neurological and psychiatric disorders. One of the possible causes is obviously a disturbance in the balance of the excitatory and inhibitory neurotransmitter systems of the hippocampus. Chronic abnormalities in the molecular mechanisms of regulation of hippocampal glutamatergic system activity in temporal lobe epilepsy are currently poorly understood. In the present study, we used Krushinsky–Molodkina (KM) rats subjected to repeated audiogenic seizures to simulate temporal lobe epilepsy. Molecular mechanisms of regulation of glutamate production by hippocampal neurons were analysed one week after the end of short-term (14 seizures) and long-term (21 seizures) kindling. In the hippocampus of КM rats, kindling results in activation of ERK1/2 kinases as well as activation of the transcription factor CREB and increased expression of the transcription factor Fra1, glutaminase and the vesicular glutamate transporters VGLUT1 and 2, that is proteins responsible for glutamate production. These data indicate increased activity of glutamatergic hippocampal neurons persisting for a week at rest after the completion of the last audiogenic stimulation. Enhanced expression of mGluR1 glutamate receptors, whose activation is known to result in Ca2+ release and increased excitotoxicity, is also shown. Long-term enhancement of glutamatergic transmission induced by repeated epileptiform seizures is not only responsible for further epileptogenesis, but may also underlie the development of neurodegenerative complications.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis.

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

DAGLβ is the principal synthesizing enzyme of 2-AG and promotes aggressive phenotype of intrahepatic cholangiocarcinoma via AP-1/DAGLβ/miR4516 feedforward circuitry.

The endocannabinoid system (ECS) is dysregulated in various liver diseases. Previously, we had shown that the major endocannabinoid 2-arachidonoyl glycerol (2-AG) promoted tumorigenesis of intrahepatic cholangiocarcinoma (ICC). However, biosynthesis regulation and clinical significance of 2-AG remain elusive. In the present study, we quantified 2-AG by gas chromatography/mass spectrometry (GC/MS) and showed that 2-AG was enriched in patients with ICC samples as well as in thioacetamide-induced orthotopic rat ICC model. Moreover, we found that diacylglycerol lipase β (DAGLβ) was the principal synthesizing enzyme of 2-AG that significantly upregulated in ICC. DAGLβ promoted tumorigenesis and metastasis of ICC in vitro and in vivo and positively correlated with clinical stage and poor survival in patients with ICC. Functional studies showed that activator protein-1 (AP-1; heterodimers of c-Jun and FRA1) directly bound to the promoter and regulated transcription of DAGLβ, which can be enhanced by lipopolysaccharide (LPS). miR-4516 was identified as the tumor-suppressing miRNA of ICC that can be significantly suppressed by LPS, 2-AG, or ectopic DAGLβ overexpression. FRA1 and STAT3 were targets of miR-4516 and overexpression of miRNA-4516 significantly suppressed expression of FRA1, SATA3, and DAGLβ. Expression of miRNA-4516 was negatively correlated with FRA1, SATA3, and DAGLβ in patients with ICC samples. Our findings identify DAGLβ as the principal synthesizing enzyme of 2-AG in ICC. DAGLβ promotes oncogenesis and metastasis of ICC and is transcriptionally regulated by a novel AP-1/DAGLβ/miR4516 feedforward circuitry.NEW & NOTEWORTHY Dysregulated endocannabinoid system (ECS) had been confirmed in various liver diseases. However, regulation and function of 2-arachidonoyl glycerol (2-AG) and diacylglycerol lipase β (DAGLβ) in intrahepatic cholangiocarcinoma (ICC) remain to be elucidated. Here, we demonstrated that 2-AG was enriched in ICC, and DAGLβ was the principal synthesizing enzyme of 2-AG in ICC. DAGLβ promotes tumorigenesis and metastasis in ICC via a novel activator protein-1 (AP-1)/DAGLβ/miR4516 feedforward circuitry.

UBAP2 plays a role in bone homeostasis through the regulation of osteoblastogenesis and osteoclastogenesis

Osteoporosis is a condition characterized by decreased bone mineral density (BMD) and reduced bone strength, leading to an increased risk of fractures. Here, to identify novel risk variants for susceptibility to osteoporosis-related traits, an exome-wide association study is performed with 6,485 exonic single nucleotide polymorphisms (SNPs) in 2,666 women of two Korean study cohorts. The rs2781 SNP in UBAP2 gene is suggestively associated with osteoporosis and BMD with p-values of 6.1 × 10−7 (odds ratio = 1.72) and 1.1 × 10−7 in the case-control and quantitative analyzes, respectively. Knockdown of Ubap2 in mouse cells decreases osteoblastogenesis and increases osteoclastogenesis, and knockdown of ubap2 in zebrafish reveals abnormal bone formation. Ubap2 expression is associated with E-cadherin (Cdh1) and Fra1 (Fosl1) expression in the osteclastogenesis-induced monocytes. UBAP2 mRNA levels are significantly reduced in bone marrow, but increased in peripheral blood, from women with osteoporosis compared to controls. UBAP2 protein level is correlated with the blood plasma level of the representative osteoporosis biomarker osteocalcin. These results suggest that UBAP2 has a critical role in bone homeostasis through the regulation of bone remodeling.

Cytosolic EpCAM cooperates with H-Ras to regulate epithelial to mesenchymal transition through ZEB1.

Next generation sequencing of human cancer mutations has identified novel therapeutic targets. Activating Ras oncogene mutations play a central role in oncogenesis, and Ras-driven tumorigenesis upregulates an array of genes and signaling cascades that can transform normal cells into tumor cells. In this study, we investigated the role of altered localization of epithelial cell adhesion molecule (EpCAM) in Ras-expressing cells. Analysis of microarray data demonstrated that Ras expression induced EpCAM expression in normal breast epithelial cells. Fluorescent and confocal microscopy showed that H-Ras mediated transformation also promoted epithelial-to-mesenchymal transition (EMT) together with EpCAM. To consistently localize EpCAM in the cytosol, we generated a cancer-associated EpCAM mutant (EpCAM-L240A) that is retained in the cytosol compartment. Normal MCF-10A cells were transduced with H-Ras together with EpCAM wild-type (WT) or EpCAM-L240A. WT-EpCAM marginally effected invasion, proliferation, and soft agar growth. EpCAM-L240A, however, markedly altered cells and transformed to mesenchymal phenotype. Ras-EpCAM-L240A expression also promoted expression of EMT factors FRA1, ZEB1 with inflammatory cytokines IL-6, IL-8, and IL1. This altered morphology was reversed using MEK-specific inhibitors and to some extent JNK inhibition. Furthermore, these transformed cells were sensitized to apoptosis using paclitaxel and quercetin, but not other therapies. For the first time, we have demonstrated that EpCAM mutations can cooperate with H-Ras and promote EMT. Collectively, our results highlight future therapeutic opportunities in EpCAM and Ras mutated cancers.

Abstract 4823: The novel miR-15a/Fra-2/IGF1R axis drives response to starvation-induced cell stress in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a relatively uncommon malignancy; however, its incidence is rising worldwide, and it is expected to become the second-leading cause of cancer-related death by 2030. From a histological point of view, PDAC is characterized by a prominent desmoplastic reaction that compresses blood vessels, limiting oxygen and nutrient availability in the tumor microenvironment. Despite that, PDAC cells are capable to adapt dynamically to these stress conditions, adopting different strategies that includes the strict regulation of the autophagic flux. Thus, studying these adaptive mechanisms is crucial to understand PDAC progression and to establish new therapeutic modalities to tackle it. Here, we explore the role of the tumor suppressor miR-15a in the regulation of its putative target Fra-2, a transcription factor, commonly activated by cell stress. By employing IPA on PDAC tumors from TCGA dataset, we found that both miR-15a and its target Fra-2 are predicted to regulate the IGF-1 signaling pathway. In an independent cohort of 44 PDAC samples, miR-15a levels inversely correlated with both Fra-2 and IGF1R expression; conversely, Fra-2 significantly correlated with IGF1R. By chromatin immunoprecipitation and luciferase assay, we assessed that miR-15a directly targeted Fra-2 and IGF1R that, in turn, is transcriptionally regulated by Fra-2 activity. Then, we investigated the role of miR-15a/Fra-2 regulation of IGF1R in the response to starvation-induced cell stress. In starved PDAC cell lines, Fra-2 transcriptional activity triggered IGF1R promoter, causing IGF1R overexpression in control cells but not in miR-15a-overexpressing cells. Consistently, the IGF1 release after starvation induced phosphorylation of IGF1R and activation of the downstream mTOR pathway in control cells but not in miR-15a-overexpressing cells. Therefore, TEM and western blot analysis demonstrated that activation of mTOR via IGF1 release reduced the autophagic flux of PDAC control cell lines compared to miR-15a overexpressing cells under starvation. To assess our results in vivo, we injected PDAC cells wild type or Fra-2 knockout into the flank of nude mice. At tumor onset, mice were randomly divided in two groups and fed with control or hypoproteic diet for three weeks. Hypoproteic diet did not interfere with the growth of wild-type tumors, by contrast, significantly impaired Fra-2KO tumors growth rate. Tumor analysis revealed that hypoproteic diet potently induced IGF1R overexpression and mTOR pathway activation in wild-type tumors but not in Fra-2KO tumors. Our findings demonstrate that IGF1R expression is regulated by miR-15a directly and indirectly via Fra-2 in PDAC. This novel miR-15a/Fra-2/IGF1R axis, triggered by starvation, regulates the autophagic flux and growth of PDAC cells in stress condition, and could be targeted by specific small inhibitors. Citation Format: Gian Luca Rampioni Vinciguerra, Marina Capece, Luca Reggiani Bonetti, Paolo Magistri, Federica Calore, Giovanni Nigita, Rosario Distefano, Roberto Ballarin, Fabrizio Di Benedetto, Andrea Vecchione, Barbara Belletti, Gustavo Baldassarre, Francesca Lovat, Carlo M. Croce. The novel miR-15a/Fra-2/IGF1R axis drives response to starvation-induced cell stress in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4823.

Abstract 3903: Role of the miR-301a/Fra-2/GLIPR1 axis in lung cancer cisplatin resistance

Abstract Lung cancer is the leading cause of cancer-related mortality in both men and women worldwide. Despite the administration of platinum compounds represents the main treatment, the majority of tumors remains intrinsically resistant. In lung cancer, miR-301a exerts a main role by modulating the activity of transcription factors like NF-kB and Stat3. Here, we dissected the contribution of miR-301a in the regulation of its new identified target Fos-related antigen-2 (Fra-2), a transcription factor that belongs to the Fos/AP-1 family. By microarray analysis, we discovered that Fra-2 overexpression increased glioma pathogenesis-related protein 1 (GLIPR1) levels, a mediator of cisplatin resistance in lung cancer. Its mechanism of regulation is still unclear. We demonstrated that GLIPR1 is also a miR-301a target. In vitro, modulation of miR-301a reduced Fra-2 and GLIPR1 levels; conversely, Fra-2 overexpression significantly increased GLIPR1 and miR-301a. Then, by chromatin immunoprecipitation assay, we confirmed that Fra-2 interacts with the promoter regions of both GLIPR1 and MIR301A genes, supporting that miR-301a/Fra-2/GLIPR1 axis could be autoregulated by feedback loop in which Fra-2 promotes the transcription of MIR301A gene. Investigating the effect of this new axis on the response to cisplatin, we observed that both Fra-2/GLIPR1 overexpression and miR-301a silencing induced cisplatin resistance in lung cancer cells. By contrast, silencing of GLIPR1 and combined administration of low doses of Fos/AP-1 inhibitor restored the cisplatin sensitivity in Fra-2 overexpressing cells. In the lung adenocarcinoma samples from the TCGA dataset, miR-301a overexpression inversely correlated with Fra-2 and GLIPR1 expression. Consistently, the overexpression of miR-301a identified a fraction of tumors with low expression of Fra-2 and GLIPR1 in an internal cohort of lung cancer samples. Altogether, our findings identify the miR-301a/Fra-2/GLIPR1 axis that contributes to cisplatin resistance in lung cancer cells and could serve as biomarker to stratify patients who may benefit from cisplatin administration, alone or in combination with Fos/AP-1 inhibitors. Citation Format: Francesca Lovat, Gian Luca Rampioni Vinciguerra, Marina Capece, Rosario Distefano, Giovanni Nigita, Andrea Vecchione, Carlo M. Croce. Role of the miR-301a/Fra-2/GLIPR1 axis in lung cancer cisplatin resistance. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3903.

Abstract PD10-03: PD10-03 Super-enhancer-oriented integrative bioinformatics identifies aberrant KLF4 signaling in endocrine-resistant breast cancer (BC)

Abstract Background: Recent studies suggest that enhancer reprogramming underlies heterogeneity and disease progression in estrogen receptor-positive (ER+) BC. Cell-type/state specific transcription is governed by high-order assemblies of master transcription factors (TFs) and epigenetically defined regulatory regions including super-enhancers (SEs). We previously showed that aberrant activation of the pioneer TF FOXA1 promotes enhancer and transcriptional reprogramming in endocrine-resistant BC, involving the ER and the AP-1 FRA1 and c-JUN TFs. As SEs maintain a robust cell-type/state specific core transcriptional regulatory circuitry (CRC) in developmental and tumorigenic processes, we sought to identify key additional TFs in SE/FOXA1-driven CRCs in endocrine resistance, which could serve as attractive therapeutic targets. Methods: TF binding motif at the shared SEs (mapped by H3K27ac ChIP-seq) between MCF7-parental (P) cells with ectopic FOXA1 overexpression (OE) and the endogenous FOXA1-amplifed tamoxifen-resistant (TamR) cells was analyzed by HOMER. ER-bound SEs distinguishing TamR vs. P cells were defined by integrating the SEs with our prior ER ChIP-seq data (PMID 28507152). KLF4 motif within these ER-bound SEs was scanned using FIMO and linked to nearby genes by intersection with the previously defined promoter-tethered regions (PTRs) (PMID 24141950). Differential gene expression in MCF7-TamR cells upon KLF4 knockdown (KD) by 3 unique siRNAs was analyzed using limma from edgeR. The biological and clinical significance of the KLF4-dependent genes was analyzed using Gene Ontology and survival modeling with METABRIC and the ER+ metastatic BC cohort (SABCS19-GS2-02). Cell migration was assessed by the wound-healing assay. Results: We identified KLF4 among the top enriched TF binding motifs at the shared SEs in FOXA1-overexpressing MCF7-P cells and the FOXA1-amplified TamR cells. Analysis of our prior RNA-seq data of MCF7-P and TamR cells upon OE or siRNA KD of FOXA1, FRA1, or c-JUN (PMIDs 27791031, 31826955, 32424275, SABCS21-PD1-05) revealed KLF4, the Yamanaka factor for induced pluripotent stem cells, as a common target activated by the FOXA1/FRA1/c-JUN axis. We next identified 44 genes commonly down-regulated upon KLF4 KD in the MCF7-TamR cells. This KLF4-dependent 44-gene set was enriched in biological processes of embryonic development and tumor progression, preferentially dependent on ER in MCF7-TamR vs. P cells, highly elevated in ER+ metastases vs. primary tumors, and associated with poor outcome in ER+ BC treated with endocrine therapy. KLF4 KD, using the 2 siRNAs that generated similar pathway perturbations in MCF7-TamR cells, reduced TamR cell migration. Notably, among the genes co-dependent on KLF4 and ER in TamR cells, PYGB was the only gene with a PTR residing in an ER-bound SE established in TamR but not P cells. Glycogen phosphorylase B, encoded by PYGB, is the rate-limiting enzyme in glycogen degradation and plays a role in the progression of various tumors. Expression of KLF4, FOXA1, and FRA1 are commonly activated during the differentiation of human embryonic stem cells into foregut endoderm and in the inner core of fibroblasts of first-trimester human placenta villi, suggesting a unique role of KLF4 in mediating lineage-specific CRC, possibly by engaging PYGB and the glycogen metabolic pathway in advanced ER+ disease. Conclusions: Using SE-oriented integrative bioinformatics, we identified KLF4 as a potential novel target in the FOXA1/AP-1 transcriptional axis. As KLF4 binding motif resides in the unique ER-bound SEs of TamR cells, KLF4 likely forms an auto-regulated loop amplifying CRC in transcriptional reprogramming, among which the PYGB/glycogen metabolic pathway merits further investigation in endocrine-resistant ER+ disease. Citation Format: Chia Chia Liu, Lanfang Qin, Shanunak Sathe, Sarmistha Nanda, Jamunarani Veeraraghavan, Ofir Cohen, Nikhil Wagle, Mothaffar Rimawi, C. Kent Osborne, Xiaoyong Fu, Rachel Schiff. PD10-03 Super-enhancer-oriented integrative bioinformatics identifies aberrant KLF4 signaling in endocrine-resistant breast cancer (BC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD10-03.

ABCA1-Mediated EMT Promotes Papillary Thyroid Cancer Malignancy through the ERK/Fra-1/ZEB1 Pathway.

Papillary thyroid cancer (PTC) is the most prevalent histological type of thyroid cancer (TC) worldwide. Although tumor metastasis occurs in regional lymph nodes, distant metastasis (DM) may also occur. Radioactive iodine (RAI) therapy is an effective treatment for TC; however, resistance to RAI occurs in patients with DM. Therefore, in this study, we investigated the efficacy of DM-related biomarkers as therapeutic targets for PTC therapy. ABCA1 expression was higher in aggressive BCPAP cells than in other PTC cells in terms of migration and invasion capacity. The knockdown of ABCA1 substantially decreased the expression of the epithelial-mesenchymal transition (EMT) marker, N-cadherin, and EMT regulator (ZEB1), resulting in suppressed migration and invasion of BCPAP cells. ABCA1 knockdown also reduced ERK activity and Fra-1 expression, which correlated with the effects of an ERK inhibitor or siRNA-mediated inhibition of ERK or Fra-1 expression. Furthermore, ABCA1-knocked-down BCPAP cells suppressed cell migration and invasion by reducing Fra-1 recruitment to Zeb1 promoter; lung metastasis was not observed in mice injected with ABCA1-knocked-down cells. Overall, our findings suggest that ABCA1 regulates lung metastasis in TC cells.

Temporal pattern of Fos and Jun families expression after mitogenic stimulation with FGF-2 in rat neural stem cells and fibroblasts.

Intense stimulation of most living cells triggers the activation of immediate early genes, such as Fos and Jun families. These genes are important in cellular and biochemical processes, such as mitosis and cell death. The present study focused on determining the temporal expression pattern of Fos and Jun families in fibroblasts and neural stem cells of cerebellum, hippocampus, and subventricular zone (SVZ) of rats of different ages at 0, 0.5, 1, 3, and 6 h after stimulation with fibroblast growth factor (FGF)-2. In neonates, a similar expression pattern was observed in all cells analyzed, with lower expression in basal condition, peak expression at 0.5 h after stimulation, returning to baseline values between 1 and 3 h after stimulation. On the other hand, cells from adult animals only showed Fra1 and JunD expression after stimulation. In fibroblasts and hippocampus, Fra1 reached peak expression at 0.5 h after stimulation, while in the SVZ, peak level was observed at 6 h after stimulation. JunD in fibroblasts presented two peak expressions, at 0.5 and 6 h after stimulation. Between these periods, the expression observed was at a basal level. Nevertheless, JunD expression in SVZ and hippocampus was low and without significant changes after stimulation. Differences in mRNA expression in neonate and adult animals characterize the significant differences in neurogenesis and cell response to stimulation at different stages of development. Characterizing these differences might be important for the development of cell cultures, replacement therapy, and the understanding of the physiological response profile of different cell types.

UCP2 Upregulation Increases Fra-1 Expression and S-phase Cell Population without Decreasing Apoptosis during Skin Cell Transformation

Upregulation of uncoupling protein 2 (UCP2) is considered a prosurvival mechanism for cancer cells. This prosurvival function is thought to be mediated by UCP2’s uncoupling activity which reduces the production of superoxide in the mitochondria. However, exactly how highly expressed UCP2 regulates cell proliferation, cell cycle, and cell death during the early stage of tumorigenesis has not been studied thoroughly. For this purpose, we generated UCP2 stably overexpressed JB6 Cl-41 cells (a skin cell transformation model) and performed studies to answer the above questions. Our results demonstrated that UCP2 overexpression enhanced cell proliferation, activation of the oncoprotein Fra-1, anchorage-independent growth, 3D spheroids growth, and glucose uptake during skin cell transformation. Next, our results demonstrated that UCP2 overexpression resulted in marked decreases in the proportion of the cells in the G1 phase and an increase of cells in the S phase of the cell cycle, which was accompanied by increased expression of Cyclin E and Cdk2. Lastly, UCP2 overexpression did not enhance or suppress apoptosis during skin cell transformation, as indicated by Annexin V and active caspase 3/7 staining. Taken together, these data suggest that UCP2 upregulation mainly enhances the Fra-1 oncogenic pathway which drives cell proliferation, without inhibiting apoptosis during skin cell transformation.

FRA1:c-JUN:HDAC1 complex down-regulates filaggrin expression upon TNFα and IFNγ stimulation in keratinocytes

Filaggrin (FLG), an essential structural protein for skin barrier function, is down-regulated under chronic inflammatory conditions, leading to disruption of the skin barrier. However, the detailed molecular mechanisms of how FLG changes in the context of chronic inflammation are poorly understood. Here, we identified the molecular mechanisms by which inflammatory cytokines inhibit FLG expression in the skin. We found that the AP1 response element within the -343/+25 of the FLG promoter was necessary for TNFα + IFNγ-induced down-regulation of FLG promoter activity. Using DNA affinity precipitation assay, we observed that AP1 subunit composition binding to the FLG promoter was altered from c-FOS:c-JUN (at the early time) to FRA1:c-JUN (at the late time) in response to TNFα + IFNγ stimulation. Knockdown of FRA1 or c-JUN abrogated TNFα + IFNγ-induced FLG suppression. Histone deacetylase (HDAC) 1 interacted with FRA1:c-JUN under TNFα + IFNγ stimulation. Knockdown of HDAC1 abrogated the inhibitory effect of TNFα + IFNγ on FLG expression. The altered expression of FLG, FRA1, c-JUN, and HDAC1 was confirmed in mouse models of 2,4-dinitrochlorobenzene-induced atopic dermatitis and imiquimod-induced psoriasis. Thus, the current study demonstrates that TNFα + IFNγ stimulation suppresses FLG expression by promoting the FRA1:c-JUN:HDAC1 complex. This study provides insight into future therapeutic strategies targeting the FRA1:c-JUN:HDAC1 complex to restore impaired FLG expression in chronic skin inflammation.

Fra-1 induces apoptosis and neuroinflammation by targeting S100A8 to modulate TLR4 pathways in spinal cord ischemia/reperfusion injury.

Spinal cord ischemia/reperfusion injury (SCII) is a severe complication driven by apoptosis and neuroinflammation. An increase in the expression of c-Fos, a member of the AP-1 family, is known as a neuronal activation marker in SCII. The AP-1 family is composed of Jun, Fos, and is associated with the regulation of cytokines expression and apoptosis. Fra-1 is a member of the Fos family, however, the contribution of Fra-1 to SCII is still unclear. In our study, Fra-1 was highly upregulated especially in neurons and microglia and promoted apoptosis by changing the expression of Bax/Bcl-2 after SCII. Furthermore, we found that Fra-1 directly regulated the transcription expression of S100A8. We demonstrated that knockdown of Fra-1 alleviated S100A8 mediated neuronal apoptosis and inflammatory factor release, thus improved motor function after SCII. Interestingly, we showed that administration of TAK-242, the TLR4 inhibitor, to the ischemia/reperfusion (I/R) injury induced rats suppressed the activation of the ERK and NF-κB pathways, and further reduced Fra-1 expression. In conclusion, we found that Fra-1-targeted S100A8 was expressed the upstream of Fra-1, and the Fra-1/S100A8 interaction formed a feedback loop in the signaling pathways activated by SCII.