Novel PROTAC probes targeting FOSL1 degradation to eliminate head and neck squamous cell carcinoma cancer stem cells.

Previously, we identified that AP-1 transcription factor FOSL1 is required to maintain cancer stem cells (CSCs) in HNSCC, and an AP-1 inhibitor, T-5224, can eliminate HNSCC CSCs. However, its potency is relatively low, and furthermore, whether T-5224 eradicates CSCs through targeting FOSL1 and whether FOSL1 serves as an effective target for eliminating CSCs in HNSCC, require further validation. We first found that T-5224 can bind to FOSL1 directly. As a proof-of-principle, several cereblon (CRBN)-recruiting PROTACs were designed and synthesized using T-5224 as a warhead for more effective of targeting FOSL1. The top compound can potently degrade FOSL1 in HNSCC, thereby effectively eliminating CSCs to suppress HNSCC tumorigenesis, with around 30 to 100-fold improved potency over T-5224. In summary, our study further validates FOSL1 as an effective target for eliminating CSCs in HNSCC and suggests that PROTACs may provide a unique molecular tool for the development of novel molecules for targeting FOSL1.

Epigenomic signatures of sarcomatoid differentiation to guide the treatment of renal cell carcinoma.

Renal cell carcinoma with sarcomatoid differentiation (sRCC) is associated with poor survival and a heightened response to immune checkpoint inhibitors (ICIs). Two major barriers to improving outcomes for sRCC are the limited understanding of its gene regulatory programs and the low diagnostic yield of tumor biopsies due to spatial heterogeneity. Herein, we characterized the epigenomic landscape of sRCC by profiling 107 epigenomic libraries from tissue and plasma samples from 50 patients with RCC and healthy volunteers. By profiling histone modifications and DNA methylation, we identified highly recurrent epigenomic reprogramming enriched in sRCC. Furthermore, CRISPRa experiments implicated the transcription factor FOSL1 in activating sRCC-associated gene regulatory programs, and FOSL1 expression was associated with the response to ICIs in RCC in two randomized clinical trials. Finally, we established a blood-based diagnostic approach using detectable sRCC epigenomic signatures in patient plasma, providing a framework for discovering epigenomic correlates of tumor histology via liquid biopsy.

Interaction of NF-κB and FOSL1 drives glioma stemness.

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor; GBM's inevitable recurrence suggests that glioblastoma stem cells (GSC) allow these tumors to persist. Our previous work showed that FOSL1, transactivated by the STAT3 gene, functions as a tumorigenic gene in glioma pathogenesis and acts as a diagnostic marker and potential drug target in glioma patients. Accumulating evidence shows that STAT3 and NF-κB cooperate to promote the development and progression of various cancers. The link between STAT3 and NF-κB suggests that NF-κB can also transcriptionally regulate FOSL1 and contribute to gliomagenesis. To investigate downstream molecules of FOSL1, we analyzed the transcriptome after overexpressing FOSL1 in a PDX-L14 line characterized by deficient FOSL1 expression. We then conducted immunohistochemical staining for FOSL1 and NF-κB p65 using rabbit polyclonal anti-FOSL1 and NF-κB p65 in glioma tissue microarrays (TMA) derived from 141 glioma patients and 15 healthy individuals. Next, mutants of the human FOSL1 promoter, featuring mutations in essential binding sites for NF-κB were generated using a Q5 site-directed mutagenesis kit. Subsequently, we examined luciferase activity in glioma cells and compared it to the wild-type FOSL1 promoter. Then, we explored the mutual regulation between NF-κB signaling and FOSL1 by modulating the expression of NF-κB or FOSL1. Subsequently, we assessed the activity of FOSL1 and NF-κB. To understand the role of FOSL1 in cell growth and stemness, we conducted a CCK-8 assay and cell cycle analysis, assessing apoptosis and GSC markers, ALDH1, and CD133 under varying FOSL1 expression conditions. Transcriptome analyses of downstream molecules of FOSL1 show that NF-κB signaling pathway is regulated by FOSL1. NF-κB p65 protein expression correlates to the expression of FOSL1 in glioma patients, and both are associated with glioma grades. NF-κB is a crucial transcription factor activating the FOSL1 promoter in glioma cells. Mutual regulation between NF-κB and FOSL1 contributes to glioma tumorigenesis and stemness through promoting G1/S transition and inhibiting apoptosis. Therefore, the FOSL1 molecular pathway is functionally connected to NF-κB activation, enhances stemness, and is indicative that FOSL1 may potentially be a novel GBM drug target.

FOSL1's Oncogene Roles in Glioma/Glioma Stem Cells and Tumorigenesis: A Comprehensive Review.

This review specifically examines the important function of the oncoprotein FOSL1 in the dimeric AP-1 transcription factor, which consists of FOS-related components. FOSL1 is identified as a crucial controller of invasion and metastatic dissemination, making it a potential target for therapeutic treatment in cancer patients. The review offers a thorough examination of the regulatory systems that govern the influence exerted on FOSL1. These include a range of changes that occur throughout the process of transcription and after the translation of proteins. We have discovered that several non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), play a significant role in regulating FOSL1 expression by directly interacting with its mRNA transcripts. Moreover, an investigation into the functional aspects of FOSL1 reveals its involvement in apoptosis, proliferation, and migration. This work involves a comprehensive analysis of the complex signaling pathways that support these diverse activities. Furthermore, particular importance is given to the function of FOSL1 in coordinating the activation of several cytokines, such as TGF-beta, and the commencement of IL-6 and VEGF production in tumor-associated macrophages (TAMs) that migrate into the tumor microenvironment. There is a specific emphasis on evaluating the predictive consequences linked to FOSL1. Insights are now emerging on the developing roles of FOSL1 in relation to the processes that drive resistance and reliance on specific treatment methods. Targeting FOSL1 has a strong inhibitory effect on the formation and spread of specific types of cancers. Despite extensive endeavors, no drugs targeting AP-1 or FOSL1 for cancer treatment have been approved for clinical use. Hence, it is imperative to implement innovative approaches and conduct additional verifications.

Melatonin inhibits the stemness of head and neck squamous cell carcinoma by modulating HA synthesis via the FOSL1/HAS3 axis.

Hyaluronic acid (HA) is a glycosaminoglycan and the main component of the extracellular matrix (ECM), which has been reported to interact with its receptor CD44 to play critical roles in the self-renewal and maintenance of cancer stem cells (CSCs) of multiple malignancies. Melatonin is a neuroendocrine hormone with pleiotropic antitumor properties. However, whether melatonin could regulate HA accumulation in the ECM to modulate the stemness of head and neck squamous cell carcinoma (HNSCC) remains unknown. In this study, we found that melatonin suppressed CSC-related markers, such as CD44, of HNSCC cells and decreased the tumor-initiating frequency of CSCs in vivo. In addition, melatonin modulated HA synthesis of HNSCC cells by downregulating the expression of hyaluronan synthase 3 (HAS3). Further study showed that the Fos-like 1 (FOSL1)/HAS3 axis mediated the inhibitory effects of melatonin on HA accumulation and stemness of HNSCC in a receptor-independent manner. Taken together, melatonin modulated HA synthesis through the FOSL1/HAS3 axis to inhibit the stemness of HNSCC cells, which elucidates the effect of melatonin on the ECM and provides a novel perspective on melatonin in HNSCC treatment.

FOSL1 regulates hyperproliferation and NLRP3-mediated inflammation of psoriatic keratinocytes through the NF-kB signaling via transcriptionally activating TRAF3.

Psoriasis is a common and immune-mediated skin disease related to keratinocytes hyperproliferation and inflammation. Fos-like antigen-1 (FOSL1) is an important transcription factor involved in various diseases. FOSL1 has been reported to be differentially expressed in psoriasis. However, the roles and mechanism of FOSL1 in psoriasis progression remain largely unknown. FOSL1 is an upregulated transcription factor in psoriasis and increased in M5-treated HaCaT cells. FOSL1 had a diagnostic value in psoriasis, and positively associated with PASI score, TNF-α and IL-6 levels in psoriasis patients. FOSL1 silencing attenuated M5-induced HaCaT cell hyperproliferation through decreasing cell viability and proliferative ability and increasing cell apoptosis. FOSL1 knockdown mitigated M5-induced NLRP3 inflammasome activation and it-mediated inflammatory cytokine (IL-6, IL-8 and CCL17) expression. TRAF3 expression was increased in psoriasis patients and M5-treated HaCaT cells. FOSL1 transcriptionally activating TRAF3 in HaCaT cells. TRAF3 overexpression reversed the suppressive effects of FOSL1 silencing on M5-induced hyperproliferation and NLRP3-mediated inflammation. FOSL1 knockdown attenuated M5-induced NF-κB signaling activation by reducing TRAF3. Activation of NF-κB signaling reversed the effects of FOSL1 knockdown on hyperproliferation and inflammation in M5-treated cells. FOSL1 silencing prevented M5-induced hyperproliferation and NLRP3-mediated inflammation of keratinocytes by inhibiting TRAF3-mediated NF-κB activity, indicating FOSL1 might act as a therapeutic target of psoriasis.

CYTOR Facilitates Formation of FOSL1 Phase Separation and Super Enhancers to Drive Metastasis of Tumor Budding Cells in Head and Neck Squamous Cell Carcinoma.

Tumor budding (TB) is a small tumor cell cluster with highly aggressive behavior located ahead of the invasive tumor front. However, the molecular and biological characteristics of TB and the regulatory mechanisms governing TB phenotypes remain unclear. This study reveals that TB exhibits a particular dynamic gene signature with stemness and partial epithelial-mesenchymal transition (p-EMT). Importantly, nuclear expression of CYTOR is identified to be the key regulator governing stemness and the p-EMT phenotype of TB cells, and targeting CYTOR significantly inhibits TB formation, tumor growth and lymph node metastasis in head and neck squamous cell carcinoma (HNSCC). Mechanistically, CYTOR promotes tumorigenicity and metastasis of TB cells by facilitating the formation of FOSL1 phase-separated condensates to establish FOSL1-dependent super enhancers (SEs). Depletion of CYTOR leads to the disruption of FOSL1-dependent SEs, which results in the inactivation of cancer stemness and pro-metastatic genes. In turn, activation of FOSL1 promotes the transcription of CYTOR. These findings indicate that CYTOR is a super-lncRNA that controls the stemness and metastasis of TB cells through facilitating the formation of FOSL1 phase separation and SEs, which may be an attractive target for therapeutic interventions in HNSCC.

Molecular mechanisms of pelvic organ prolapse influenced by FBLN5 via FOSL1/miR-222/MEIS1/COL3A1 axis.

This study delves into the role of FBLN5 in pelvic organ prolapse (POP) and its molecular mechanisms, focusing on the FOSL1/miR-222/MEIS1/COL3A1 axis. Gene relationships linked to POP were confirmed using bioinformatics databases like GEO and StarBase. Primary human uterosacral ligament fibroblasts (hUSLF) were extracted and subjected to mechanical stretching. Cellular cytoskeletal changes were examined via phalloidin staining, intracellular ROS levels with a ROS kit, cell apoptosis through flow cytometry, and cell senescence using ß-galactosidase staining. FBLN5's downstream targets were identified, and the interaction between FOSL1 and miR-222 and miR-222 and MEIS1 were validated using assays. In rat models, the role of FBLN5 in POP was assessed using bladder pressure tests. Results indicated diminished FBLN5 expression in uterine prolapse. Enhanced FBLN5 countered mechanical damage in hUSLF cells by downregulating FOSL1. FOSL1 augmented miR-222, inhibiting MEIS1, which subsequently fostered COL3A1 transcription. In rat models, the absence of FBLN5 exacerbated POP by influencing the FOSL1/miR-222/MEIS1/COL3A1 pathway. FBLN5's protective role likely involves regulating the above axis and boosting COL3A1 expression. Further research is needed to validate the effectiveness and safety of this mechanism in human patients and to propose potential new treatment options.

Exosome-transmitted FOSL1 from cancer-associated fibroblasts drives colorectal cancer stemness and chemo-resistance through transcriptionally activating ITGB4.

Cancer-associated fibroblasts (CAFs) have been proved to facilitate colorectal cancer (CRC) development, either with boosting chemo-resistance by communicating with CRC cells in the tumor microenvironment. However, the underlying molecular mechanisms remain largely unclear. Relative expressions of FOSL1 and ITGB4, either with their correlations in CRC tissues, were assessed using qRT-PCR analysis. Also, Kaplan-Meier survival analysis was employed for evaluating the prognosis. Identification of CAFs was determined by the detection of specific makers (α-SMA, FAP, and FSP1) using western blot and immunofluorescence staining. Cell proliferation, self-renewal capacity, and cell apoptosis were estimated by CCK-8, sphere-formation, and flow cytometry assays. Transcriptional regulation of FOSL1 on integrin ß4 (ITGB4) was confirmed using ChIP and dual-luciferase reporter assays. Increased FOSL1 and ITGB4 in CRC tissues were both positively correlated with the poor prognosis of CRC patients. Interestingly, FOSL1 was enriched in the CAFs isolated from CRC stroma, instead of ITGB4. CRC cells under a co-culture system with CAFs-conditioned medium (CAFs-CM) exhibited increased FOSL1, promotive cell proliferation, and reduced apoptosis, while these effects could be blocked by exosome inhibitor (GW4869). Moreover, CAFs-derived exosomal FOSL1 was validated to enhance proliferative ability and oxaliplatin resistance of CRC cells. Our results uncovered that CAFs-derived exosomes could transfer FOSL1 to CRC cells, thereby promoting CRC cell proliferation, stemness, and oxaliplatin resistance by transcriptionally activating ITGB4.

Superficial desmoplastic fibroblastoma (collagenous fibroma): Clinicopathologic study of 11 cases.

BACKGROUND: Desmoplastic fibroblastoma (collagenous fibroma) is a rare soft tissue tumor that usually arises in the subcutis or skeletal muscle. Cases superficial to fascia are unusual and can cause diagnostic difficulty. We present 11 cases of superficial desmoplastic fibroblastoma involving a wide anatomic distribution. METHODS: Archives were searched using the term "desmoplastic fibroblastoma" over a 10-year period (2012-2022). Cases superficial to fascia were retrieved, and available clinicopathologic features were recorded. Only cases involving the dermis were included. RESULTS: Eleven cases were identified, all of which were received in consultation. Tumors involved the head and neck (2), lower extremity (2), back (2), foot (1), shoulder (1), axilla (1), hand (1), and breast (1). Each consisted of a hypocellular proliferation of bland stellate to spindled fibroblasts set in a collagenous to focally myxoid stroma. The immunohistochemical stains available for review demonstrated SMA positivity (4/7) and negative immunoreactivity for CD34 (0/6), EMA (0/3), desmin (0/3), and S100 (0/7). CONCLUSIONS: Desmoplastic fibroblastoma may present superficially in the dermis to subcutis, posing a potential source of diagnostic difficulty. Recognition of the characteristic histopathologic features of desmoplastic fibroblastoma with judicial use of immunohistochemical stains should allow for accurate diagnosis.

Transcription Factor FOSL1 Promotes Angiogenesis of Colon Carcinoma by Regulating the VEGF Pathway Through Activating TIMP1.

Angiogenesis is the critical media for tumor growth and migration. Tissue Inhibitor Matrix Metalloproteinase-1 (TIMP1) acts as an oncogene in colon carcinoma (CC), but the biological effects of TIMP1 on angiogenesis remain an open issue. This study sought to explore the exact function and mechanism of TIMP1 in the angiogenesis of CC. Bioinformatics methods were utilized to analyze the expression of TIMP1 and its upstream transcription factor FOS-like antigen 1 (FOSL1) in the tumor tissue of CC. Meanwhile, in CC cell lines, real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and Western blot were utilized to verify the expression of TIMP1 and FOSL1. Cell counting kit-8 and tube formation assays were utilized to analyze the proliferation and angiogenesis abilities of human umbilical vein endothelial cells (HUVECs). Western blot was used to detect the protein expression of VEGFA, VEGFR-2, and VEGFR-3. Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were carried out to explore the specific interaction between FOSL1 and TIMP1. The present study discovered that TIMP1 and FOSL1 were evidently up-regulated in CC tissue and cells. Meanwhile, TIMP1 was found to participate in regulating the signaling pathway of vascular endothelial growth factor (VEGF). Silenced TIMP1 conspicuously suppressed the proliferation and angiogenesis of HUVECs and reduced the protein expression of VEGFA, VEGFR-2, and VEGFR-3. Moreover, FOSL1 could promote TIMP1 transcription by binding with its promoter and the inhibition of TIMP1 expression obviously reversed the promotion effects of FOSL1 overexpression on the proliferation and angiogenesis of HUVECs. FOSL1 activated VEGF pathway by up-regulating TIMP1 expression, thereby advancing CC angiogenesis. We provided theoretical basis that the FOSL1/TIMP1/VEGF pathway might be a novel option for anti-angiogenesis therapy of CC.

FOSL1 modulates Schwann cell responses in the wound microenvironment and regulates peripheral nerve regeneration.

Peripheral glial Schwann cells switch to a repair state after nerve injury, proliferate to supply lost cell population, migrate to form regeneration tracks, and contribute to the generation of a permissive microenvironment for nerve regeneration. Exploring essential regulators of the repair responses of Schwann cells may benefit the clinical treatment for peripheral nerve injury. In the present study, we find that FOSL1, a AP-1 member that encodes transcription factor FOS Like 1, is highly expressed at the injured sites following peripheral nerve crush. Interfering FOSL1 decreases the proliferation rate and migration ability of Schwann cells, leading to impaired nerve regeneration. Mechanism investigations demonstrate that FOSL1 regulates Schwann cell proliferation and migration by directly binding to the promoter of EPH Receptor B2 (EPHB2) and promoting EPHB2 transcription. Collectively, our findings reveal the essential roles of FOSL1 in regulating the activation of Schwann cells and indicate that FOSL1 can be targeted as a novel therapeutic approach to orchestrate the regeneration and functional recovery of injured peripheral nerves.

Silencing AHNAK promotes nasopharyngeal carcinoma progression by upregulating the ANXA2 protein.

PURPOSE: Nasopharyngeal carcinoma (NPC) is an aggressive head and neck disease with a high incidence of distant metastases. Enlargeosomes are cytoplasmic organelles marked by, desmoyokin/AHNAK. This study aimed to evaluate the expression of AHNAK in NPC and its effect on enlargeosomes and to investigate the correlation between AHNAK expression levels and clinical NPC patient characteristics. METHODS: Primary nasopharyngeal carcinoma (NPC) and NPC specimens were evaluated by analyzing public data, and immunohistochemistry. Systematic in vitro and in vivo experiments were performed using different NPC-derived cell lines and mouse models. RESULTS: In this study, we detected AHNAK and Annexin A2(ANXA2), a protein coating the surface of enlargeosomes, in NPC samples. We found that AHNAK was down-regulated. Down-regulation of AHNAK was associated with poor overall survival in NPC patients. Moreover, transcription factor FOSL1-mediated transcriptional repression was responsible for the low expression of AHNAK by recruiting EZH2. Whereas Annexin A2 was upregulated in human NPC tissues. Upregulation of Annexin A2 was associated with lymph node metastasis and distant metastasis in NPC patients. Functional studies confirmed that silencing of AHNAK enhanced the growth, invasion, and metastatic properties of NPC cells both in vitro and in vivo. In terms of mechanism, loss of AHNAK led to an increase of annexin A2 protein level in NPC cells. Silencing ANXA2 restored NPC cells' migrative and invasive ability upon loss of AHNAK. CONCLUSION: Here, we report AHNAK as a tumor suppressor in NPC, which may act through annexin A2 oncogenic signaling in enlargeosome, with potential implications for novel approaches to NPC treatment.

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.

Super-enhancer-associated SNHG15 cooperating with FOSL1 contributes to bladder cancer progression through the WNT pathway.

Small nucleolar RNA host gene 15 (SNHG15) plays an oncogenic role in many cancers. However, the role of SNHG15 in bladder cancer (BLCA) remains unclear. In this study, the regulation of SNHG15 on the activities of BLCA cells (T24 and RT112) was investigated. In detail, super-enhancers (SEs), differentially expressed genes, and functional enrichment were detected by bioinformatic analyses. Mutant cell lines lacking SNHG15-SEs were established using CRISPR-Cas9. Relative gene expression was detected by quantitative polymerase chain reaction (qPCR), western blot, in situ hybridization, and immunohistochemistry assays. Cell senescence, apoptosis, viability, and proliferation were measured. Chromatin immunoprecipitation (ChIP)-qPCR and luciferase reporter gene assays were conducted to analyze the interactions between genes. A novel super-enhancer of SNHG15 (SNHG15-SEs) was discovered in several BLCA datasets. The deletion of SNHG15-SEs resulted in a significant downregulation of SNHG15. Mechanistically, the core active region of SNHG15-SEs recruited the transcription factor FOSL1 to facilitate the SNHG15 transcription, thereby inducing the proliferation and metastasis of BLCA cells. Deletion of SNHG15-SEs inhibited the growth and metastasis of T24 and RT112 cells by inactivating the WNT/CTNNB1 pathway activation. Overexpression of FOSL1 in SNHG15-SEs restored the cell proliferation and metastasis. Next, a xenograft mouse model showed that SNHG15-SEs deletion inhibited the proliferation and metastasis of BLCA cells in vivo. Collectively, our data indicate that SNHG15-SEs recruit FOSL1 to promote the expression of SNHG15 which interacts with CTNNB1 in the nucleus to activate the transcription of ADAM12, leading to the malignance of BLCA cells.

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.

TRPM7 transactivates the FOSL1 gene through STAT3 and enhances glioma stemness.

INTRODUCTION: We previously reported that TRPM7 regulates glioma cells' stemness through STAT3. In addition, we demonstrated that FOSL1 is a response gene for TRPM7, and the FOSL1 gene serves as an oncogene to promote glioma proliferation and invasion. METHODS: In the present study, we determined the effects of FOSL1 on glioma stem cell (GSC) markers CD133 and ALDH1 by flow cytometry, and the maintenance of stem cell activity by extreme limiting dilution assays (ELDA). To further gain insight into the mechanism by which TRPM7 activates transcription of the FOSL1 gene to contribute to glioma stemness, we constructed a FOSL1 promoter and its GAS mutants followed by luciferase reporter assays and ChIP-qPCR in a glioma cell line and glioma patient-derived xenoline. We further examined GSC markers ALDH1 and TRPM7 as well as FOSL1 by immunohistochemistry staining (IHC) in brain tissue microarray (TMA) of glioma patients. RESULTS: We revealed that FOSL1 knockdown reduces the expression of GSC markers CD133 and ALDH1, and FOSL1 is required to maintain stem cell activity in glioma cells. The experiments also showed that mutations of - 328 to - 336 and - 378 to - 386 GAS elements markedly reduced FOSL1 promoter activity. Constitutively active STAT3 increased while dominant-negative STAT3 decreased FOSL1 promoter activity. Furthermore, overexpression of TRPM7 enhanced while silencing of TRPM7 reduced FOSL1 promoter activity. ChIP-qPCR assays revealed that STAT3, present in nuclear lysates of glioma cells stimulated by constitutively activated STAT3, can bind to two GAS elements, respectively. We demonstrated that deacetylation of FOSL1 at the Lys-116 residue located within its DNA binding domain led to an increase in FOSL1 transcriptional activity. We found that the expression of TRPM7, ALDH1, and FOSL1 protein is associated with grades of malignant glioma, and TRPM7 protein expression correlates to the expression of ALDH1 and FOSL1 in glioma patients. CONCLUSIONS: These combined results demonstrated that TRPM7 induced FOSL1 transcriptional activation, which is mediated by the action of STAT3, a mechanism shown to be important in glioma stemness. These results indicated that FOSL1, similar to GSC markers ALDH1 and TRPM7, is a diagnostic marker and potential drug target for glioma patients.

Multiple Fra-1-bound enhancers showing different molecular and functional features can cooperate to repress gene transcription.

BACKGROUND: How transcription factors (TFs) down-regulate gene expression remains ill-understood, especially when they bind to multiple enhancers contacting the same gene promoter. In particular, it is not known whether they exert similar or significantly different molecular effects at these enhancers. RESULTS: To address this issue, we used a particularly well-suited study model consisting of the down-regulation of the TGFB2 gene by the TF Fra-1 in Fra-1-overexpressing cancer cells, as Fra-1 binds to multiple enhancers interacting with the TGFB2 promoter. We show that Fra-1 does not repress TGFB2 transcription via reducing RNA Pol II recruitment at the gene promoter but by decreasing the formation of its transcription-initiating form. This is associated with complex long-range chromatin interactions implicating multiple molecularly and functionally heterogeneous Fra-1-bound transcriptional enhancers distal to the TGFB2 transcriptional start site. In particular, the latter display differential requirements upon the presence and the activity of the lysine acetyltransferase p300/CBP. Furthermore, the final transcriptional output of the TGFB2 gene seems to depend on a balance between the positive and negative effects of Fra-1 at these enhancers. CONCLUSION: Our work unveils complex molecular mechanisms underlying the repressive actions of Fra-1 on TGFB2 gene expression. This has consequences for our general understanding of the functioning of the ubiquitous transcriptional complex AP-1, of which Fra-1 is the most documented component for prooncogenic activities. In addition, it raises the general question of the heterogeneity of the molecular functions of TFs binding to different enhancers regulating the same gene.

FRA-1 as a Regulator of EMT and Metastasis in Breast Cancer.

Among FOS-related components of the dimeric AP-1 transcription factor, the oncoprotein FRA-1 (encoded by FOSL1) is a key regulator of invasion and metastasis. The well-established FRA-1 pro-invasive activity in breast cancer, in which FOSL1 is overexpressed in the TNBC (Triple Negative Breast Cancer)/basal subtypes, correlates with the FRA-1-dependent transcriptional regulation of EMT (Epithelial-to-Mesenchymal Transition). After summarizing the major findings on FRA-1 in breast cancer invasiveness, we discuss the FRA-1 mechanistic links with EMT and cancer cell stemness, mediated by transcriptional and posttranscriptional interactions between FOSL1/FRA-1 and EMT-regulating transcription factors, miRNAs, RNA binding proteins and cytokines, along with other target genes involved in EMT. In addition to the FRA-1/AP-1 effects on the architecture of target promoters, we discuss the diagnostic and prognostic significance of the EMT-related FRA-1 transcriptome, along with therapeutic implications. Finally, we consider several novel perspectives regarding the less explored roles of FRA-1 in the tumor microenvironment and in control of the recently characterized hybrid EMT correlated with cancer cell plasticity, stemness, and metastatic potential. We will also examine the application of emerging technologies, such as single-cell analyses, along with animal models of TNBC and tumor-derived CTCs and PDXs (Circulating Tumor Cells and Patient-Derived Xenografts) for studying the FRA-1-mediated mechanisms in in vivo systems of EMT and metastasis.

FOSL1 transcriptionally regulates PHLDA2 to promote 5-FU resistance in colon cancer cells.

BACKGROUND: Tumor drug resistance is a leading cause of tumor treatment failure. To date, the association between FOS-Like antigen-1 (FOSL1) and chemotherapy sensitivity in colon cancer is unclear. The present study investigated the molecular mechanism of FOSL1 regulating 5-Fluorouracil (5-FU) resistance in colon cancer. METHODS: FOSL1 expression in colon cancer was analyzed by bioinformatics methods, and its downstream regulatory factors were predicted. Pearson correlation analyzed the expression of FOSL1 and downstream regulatory gene. Meanwhile, the expression of FOSL1 and its downstream factor Pleckstrin Homology-Like Domain Family A Member 2 (PHLDA2) in colon cancer cell lines was measured by qRT-PCR and western blot. The regulatory relationship between FOSL1 and PHLDA2 was verified by chromatin immunoprecipitation (ChIP) assay and dual-luciferase reporter assay. The effects of the FOSL1/PHLDA2 axis on the resistance in colon cancer cells to 5-FU were analyzed by cell experiments. RESULTS: FOSL1 expression was evidently up-regulated in colon cancer and 5-FU resistant cells. FOSL1 was positively correlated with PHLDA2 in colon cancer. In vitro cell assays showed that low expression of FOSL1 significantly enhanced 5-FU sensitivity in colon cancer cells, significantly suppressed the proliferation of cancer cells, and induced apoptosis. Overexpression of FOSL1 presented the opposite regulatory trend. Mechanistically, FOSL1 activated PHLDA2 and up-regulated its expression. Moreover, by activating glycolysis, PHLDA2 promoted 5-Fu resistance and cell proliferation, and reduced cell apoptosis in colon cancer. CONCLUSION: Down-regulated FOSL1 expression could enhance the 5-FU sensitivity of colon cancer cells, and FOSL1/PHLDA2 axis may be an effective target for overcoming chemotherapy resistance in colon cancer.