Abstract 6444: PP2A activation targets PAI-1/CCL2 to suppress therapy-induced senescence in neuroblastoma

Abstract Background: Neuroblastoma (NBL) is the most common extracranial childhood solid tumor, and it is responsible for 15% of pediatric cancer deaths. Refractory and relapsed disease are exceedingly difficult to treat and the survival for these children is less than 50%. One hypothesis to explain this poor therapeutic response and tendency for disease recurrence is therapy-induced senescence (TIS) which is a temporary state of growth arrest following treatment. Protein phosphatase 2A (PP2A), a known tumor suppressor, is downregulated in NBL. Preliminary studies indicate that PP2A reactivation reduces TIS in NBL, therefore, we investigated the effects of a novel PP2A activator as a senotherapeutic in NBL. Methods: We employed the human NBL cell line, SK-N-AS. Topotecan, a common NBL chemotherapeutic, known and confirmed to induce senescence, and ATUX-1215, a novel small molecule PP2A activator were utilized. NBL cells were treated with topotecan and ATUX-1215 alone, as well as in combination. TIS was detected by senescence associated SA-β-galactosidase (SA-β-gal) assay. Colony forming assay detected cell proliferation while immunoblotting identified senescence associated proteins including γ-H2AX, plasminogen activator inhibitor-1 (PAI-1) and C-C motif chemokine ligand 2 (CCL2). R2 Genomics Analysis and Visualization Platform was used for mRNA expression data from human neuroblastoma samples to evaluate the association of PAI-1 and CCL2 gene expression with relapse free survival. Results: PP2A activator reduced SA-β-gal staining and protein expression of γ-H2AX, two markers of senescence, that were induced by topotecan treatment. Further, activation of PP2A in combination with topotecan significantly reduced colony forming potential in NBL cells. Immunoblotting demonstrated the reduction of two mediators and markers of senescence-associated secretory phenotype, PAI-1 and CCL2 with PP2A activation. Clinically, neuroblastoma patients with low PAI-1 as well as CCL2 expression have significantly higher (p=0.054, p=3.74e-03, respectively) relapse free survival. Conclusions: PP2A activator, ATUX-1215, holds potential as novel senotherapeutic adjunct by targeting PAI-1 and CCL2. Further investigations into the mechanisms responsible for these findings will be required with goals to advance this therapy to the clinical arena to prevent disease relapse. Citation Format: Nazia Nazam, Maryam Ghufran, Morgan L. Brown, Sorina Shirley, Jerry E. Stewart, Michael Ohlmeyer, Taylor Schanel, Elizabeth A. Beierle. PP2A activation targets PAI-1/CCL2 to suppress therapy-induced senescence in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6444.