Abstract A023: Zebrafish personalized medicine models of fusion-driven rhabdomyosarcoma

Abstract Clinical sequencing efforts have revolutionized our approaches to categorizing pediatric cancers in real time. This has dramatically improved our ability to profile pediatric tumors and in some circumstances to identify actionable vulnerabilities and personalize clinical care. Unfortunately, many of the fusion positive pediatric sarcomas are driven by oncogenic fusions that have unclear mechanisms of transformation and lack therapeutic targets. Many of these fusion-oncogenes have no cell, patient derived xenograft (PDX), or animal model to understand the biology of the human disease. This makes identifying potential new targeted therapies challenging. Our group has developed a strategy to model novel rhabdomyosarcoma fusion-oncogenes in vertebrate zebrafish systems. We have shown success with this precision functional genomics approach for alveolar and infantile rhabdomyosarcoma, including the PAX3::FOXO1 and VGLL2::NCOA2 oncogenic fusions. We found that human fusion-oncogenes generated tumors in zebrafish that histologically and transcriptionally recapitulate the human disease. We are now collaborating with the NCI-COG-NCH Molecular Characterization Initiative to identify novel rhabdomyosarcoma fusion-oncogenes, with no existing animal models, to incorporate into this precision medicine approach. This model uses a Tol2 transposon-based system to integrate the human fusion-oncogene coding sequence into the zebrafish genome. We track tumor formation in the fish by linking the fusion-oncogene to a viral 2A GFP sequence, which functions as a visual proxy for expression in vivo. Here, we present SRF::NCOA2, a fusion of transcriptional coactivators found in human spindle-cell rhabdomyosarcoma, that is transforming in multiple promoter contexts. The SRF::NCOA2 injected zebrafish in our model develop tumors before six months of age. We are now validating fidelity with the human disease using histology and bulk RNA sequencing to identify shared transcriptional signatures. Broadly, we see this as a high throughput strategy in vertebrate models to mechanistically study novel fusion oncogenes. We anticipate our modeling strategies will support targeted therapy development to improve patient treatment and outcomes. Citation Format: Lisa Hall, Madison Kouche, Emma Harrison, Kareesma Parbhoo, Elaine Mardis, Genevieve Kendall. Zebrafish personalized medicine models of fusion-driven rhabdomyosarcoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Functional and Genomic Precision Medicine in Cancer: Different Perspectives, Common Goals; 2025 Mar 11-13; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(5 Suppl):Abstract nr A023.