Abstract 3886: Decoding pediatric adrenocortical tumor heterogeneity through multimodal molecular profiling - pathways to improved risk stratification and therapy

Abstract Pediatric adrenocortical tumors (pACTs) are rare neoplasms with significant mortality, presenting diagnostic challenges in distinguishing benign from malignant tumors. Here, we employed a comprehensive multimodal molecular profiling approach to delineate and characterize molecular subgroups and investigated their potential for risk stratification. We profiled 109 pediatric adrenocortical tumors using Illumina methylation arrays and analyzed them together with 105 published samples. For 29 of the 109 tumors, fresh-frozen samples were analyzed with single-nucleus RNA sequencing and seven of these also with single-nucleus ATAC sequencing. Our analysis revealed four molecularly distinct subgroups with differences in clinical presentation, cellular composition and molecular signatures. Importantly, the herein identified high-risk subgroup demonstrated substantially reduced overall survival, with a 5-year survival rate of merely 27% compared to 81-95% in other subgroups. Notably, these tumors showed increased CpG island methylation and aberrant activation of the canonical WNT signaling pathway in gene expression profiling. Additionally, through integration of scRNA-Seq and scATAC-Seq, we uncovered complex transcriptional networks driving tumor biology. Tumor cells resembling the physiological adrenocortical zones exhibited unique gene expression patterns, with the high-risk subgroup characterized by an increased proportion of zona glomerulosa-like cells. These zona glomerulosa-like cells showed dysregulated WNT/CTNNB1 signaling and a proliferative and cell cycle activation signature, which emerge as a critical driver of malignancy. In particular, the glomerulosa-like tumor cells seem to fuel tumor proliferation by a crosstalk with fasciculata/reticularis-like tumor cells, which is unique for the high risk pACT subgroup. Further key molecular alterations include upregulation of cancer associated genes like PVT1 and MDM2, suggesting potential therapeutic vulnerabilities. Moreover, our analysis uncovered transmembrane glycoprotein BAMBI to be specifically upregulated in the high-risk tumors, highlighting its potential as a prognostic indicator. This comprehensive characterization provides a robust framework for risk stratification in pACTs. Specifically, we have unraveled a previously undescribed molecular hub using canonical WNT signaling to drive proliferation in high risk tumors. These changes may open an avenue towards integrating WNT-directed therapies in the clinical setting. Citation Format: Victoria E. Fincke, Maurice Loßner, Marina Kunstreich, Irmengard Sax, Marlena Mucha, Felix Dorn, Maria D. Hernandez Ramirez, Stefan Wudy, Christian Vokuhl, Christoph Slavetinsky, Jörg Fuchs, Michael C. Frühwald, Matthias Schlesner, Antje Redlich, Rainer Claus, Michaela Kuhlen, Pascal D. Johann. Decoding pediatric adrenocortical tumor heterogeneity through multimodal molecular profiling - pathways to improved risk stratification and therapy [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 3886.