Abstract 5388: FOSL1 promotes glioma tumorigenesis and stemness through NF-κB and STAT3 pathways

Abstract

Abstract Background: Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor, GBM’s inevitable recurrence suggests that glioblastoma stem cells (GSC) render these tumors persistent. Our previous work showed that FOSL1, which is transactivated by the STAT3 gene, functions as a tumorigenic gene in glioma pathogenesis and is a diagnostic marker and potential drug target for 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. Methods: 1). To investigate downstream molecules of FOSL1, we analyzed the transcriptome after overexpression of FOSL1 in a PDX-L14 line, characterized by very low FOSL1 expression 2). We conducted immunohistochemical staining for FOSL1 and p65 using rabbit polyclonal anti-FOSL1 and p65 in glioma tissue microarrays (TMA) derived from 76 glioma patients and 10 normal individuals. 3). Mutants of the human FOSL1 promoter, featuring mutations in essential binding sites for NF-κB and STAT3, 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. 4). We explore 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. 5) To understand the role of FOSL1 in cell growth and stemness, we conducted a CCK-8 assay, cell cycle analysis, assessing apoptosis and GSC markers, ALDH1 and CD133 under varying FOSL1 expression conditions. Results: 1) Transcriptome analyses of downstream molecules of FOSL1 show that NF-κB signaling pathways are regulated by FOSL1. 2) p65 protein expression correlates to the expression of FOSL1 in glioma patients. 3) NF-κB is a crucial transcription factor activating the FOSL1 promoter in glioma cells. 4) Mutual regulation between NF-κB and FOSL1 contributes to glioma tumorigenesis and stemness through promoting G1/S transition and inhibition of apoptosis. Conclusion: The FOSL1 molecular pathway is functionally connected to NF-κB and STAT3 activation, enhances stemness, and FOSL1 is a novel GBM drug target. Citation Format: Mingli Liu, Vanajothi Ramar, Azam Khedri, BreAnna Hudson, Shanchun Guo. FOSL1 promotes glioma tumorigenesis and stemness through NF-κB and STAT3 pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5388.