Abstract 648: PP2A reactivation upregulates <i>FGA</i> gene in neuroblastoma.

Abstract Background: High-risk neuroblastoma (NBL), driven by MYCN amplification, remains fatal for many children. Our previous work demonstrated that pharmacologic PP2A reactivation decreases NBL in vivo tumor growth through suppression of MYCN expression and stability by reducing MYCN phosphorylation and promoter acetylation, concurrent with BRD4 and RNA Pol II dephosphorylation. The current study is an extension of this previous work, in that we performed loss-of function tests validating the previous findings, and identified a downstream target regulated by MYCN within this PP2A-controlled network. Methods: The MYCN amplified human NBL cell line SK-N-BE(2) was treated with the PP2A activator, ATUX-1215, or the PP2A inhibitor, okadaic acid (OA). Immunoblotting quantified phospho-BRD4, BRD4, MYCN, PP2Aαβ-C subunit, acetylated histones (H3K27ac, H3ac), total H3, and GAPDH. PP2A activity was measured enzymatically. Bulk RNA sequencing identified transcriptional alterations, and qRT-PCR confirmed the findings. Public NBL datasets (TARGET and Capasso) were analyzed. Results: OA treatment increased phospho-BRD4, MYCN, H3K27ac, and H3ac while decreasing PP2A expression and activation. Densitometric analysis of immunoblots validated these transcriptional and epigenetic marker changes. Bulk RNA-seq revealed fibrinogen alpha chain (FGA) as a significantly upregulated gene following PP2A activation with ATUX-1215. Gene Set Enrichment Analysis (GSEA) identified enrichment of MYCN associated pathways, specifically the WEI_MYCN_TARGETS_WITH_E_BOX gene set, with FGA among upregulated targets. Increased FGA mRNA abundance was confirmed with qRT-PCR in ATUX-1215 treated NBL cells (24 h - 72 h). Public dataset analysis demonstrated that elevated FGA expression correlated with improved overall survival in MYCN amplified and stage 4 NBL patients. Conclusion: We have found that PP2A reactivation involves BRD4-mediated epigenetic regulation and histone acetylation, upregulates FGA gene, and that increased FGA is associated with improved NBL survival. These findings suggest that PP2A reactivation may restore beneficial MYCN-linked transcriptional programs, offering potential therapeutic strategy for high-risk NBL. Citation Format: Nazia Nazam, Shamza Manzoor, Maryam Ghufran, Morgan L. Brown, Ali M. Eakes, Pranava Nande, Joel C. Opara, Abdulraheem Kaimari, Michael Ohlmeyer, Elizabeth A. Beierle. PP2A reactivation upregulates FGA gene in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 648.