Abstract 1304: A novel organoid-based model to study pediatric tumor metastasis to the lung

Abstract Metastasis is the primary cause of mortality in pediatric cancer, with the lung being a common site for secondary tumor growth. A major challenge in treatment is the lack of models that accurately replicate the interactions between tumors and the lung metastatic niche observed in patients. This limitation hinders the investigation of the molecular mechanisms driving lung metastasis in pediatric solid tumors. Furthermore, it impedes the development and testing of potential inhibitors to prevent or treat lung metastases, ultimately delaying progress in improving patient outcomes. We have developed an advanced in vitro lung metastasis model using tumor-lung organoid co-cultures. To this end, we first established lung organoids from healthy pediatric lung tissue and characterized them based on the presence of airway, alveolar, and other rare lung epithelial subtypes. Next, we analyzed primary and PDX-derived cells from two types of tumors that frequently metastasize to the lungs: Ewing sarcoma (ES) and osteosarcoma (OS). Our co-culture system revealed two groups of tumor cells with distinct behaviors: The first group of tumor cells actively infiltrated the lung organoids, while the second remained closely associated without invasion. We hypothesized that this behavior in vitro corresponds to differences in metastatic potential in vivo. In line with this hypothesis, scRNA-seq analysis confirmed a high expression of EMP1, a key driver of metastatic behavior, in infiltrative cells. In contrast, non-infiltrative cells showed no change in EMP1 expression between co- and mono-culture conditions, highlighting EMP1’s specific association with tumor cell infiltration. Furthermore, we noticed phenotypic changes in lung organoids in response to specific tumor co-cultures, suggesting a reactive response to infiltrating tumor cells. Using scRNA-seq, we are currently exploring the underlying molecular mechanisms driving these changes, characterizing overall gene expression changes and signaling pathways. Experiments with conditioned media revealed that lung-organoid secreted factors attract ES and OS cells. Further analysis of the lung organoid secretome identified paracrine signals that direct tumor cell homing, making our model a powerful tool for studying and targeting lung-specific tumor attraction. To further assess the model’s relevance to lung metastases in patients, we performed spatial transcriptomics analysis (10x Visium platform) on paired primary tumors and lung metastases from ES and OS patients. This analysis will both inform the refinement of our organoid model and enhance our understanding of lung metastatic niche spatial organization.In conclusion, our study provides a framework for understanding pediatric tumor lung metastasis and establishes a versatile platform for testing pathway-specific anti-metastatic therapies targeting tumor-lung interactions. Citation Format: Martha Magdalena Zylka, Christoph Hafemeister, Lukas Watzke, Ulrike Mann, Didier Surdez, E. Alejandro Sweet-Cordero, Bernadette Liegl-Atzwanger, Matthias Dettmer, Femke Ringnalda, Marc van de Wetering, Karin Sanders, Matthias Farlik, Florian Halbritter, Martin Metzelder, Heinrich Kovar, Branka Radic Sarikas: A novel organoid-based model to study pediatric tumor metastasis to the lung [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 1304.