Abstract 196: In vitro modeling of pediatric solid tumor lung metastases
Authors: Zylka Martha , Hafemeister Christoph , Watzke Lukas , Mann Ulrike , Surdez Didier , Sweet-Cordero E. Alejandro , Liegl-Atzwanger Bernadette , Dettmer Matthias , Farlik Matthias , Halbritter Florian , Metzelder Martin , Kovar Heinrich , Radic-Sarikas Branka 
Published: March 2024

Abstract
Metastasis remains the main cause of death in pediatric cancer patients with the lung being one of the most common affected organs. Our inability to cure these patients is largely due to insufficient knowledge about tumor and metastatic niche plasticity, while existing models are not fully effective in mirroring the response seen in clinical setting. Our goal is to overcome these limitations by establishing in vitro lung metastasis models using tumor/lung organoid co-cultures to study lung infiltration of pediatric solid tumors. We successfully established patient-derived lung organoids from pediatric lung tissue and characterized them according to the presence and the localization of the respective lung epithelial cell types. Co-culture conditions of lung organoids with PDX-derived Ewing sarcoma and osteosarcoma cells were optimized and models established, while the establishment of models for other pediatric solid tumor entities is ongoing. We have observed infiltration of the lung organoids by tumor cells, and our preliminary findings suggest distinct patterns of infiltration among different tumor entities. Furthermore, we have performed single-cell RNA sequencing analysis on these co-cultures in comparison to the parental lung organoids and tumor cells, aiming to uncover the specific signaling pathways activated in the lung metastatic niche in response to tumor cell invasion. Additionally, experiments using conditioned medium suggest that the lung organoid secretome is sufficient to induce homing of osteosarcoma and Ewing sarcoma cells to the organoids, with the CXCL12/CXCR4 signaling axis as a prime candidate driver. To ascertain the extent to which our in vitro model recapitulates the in vivo lung metastatic niche, we performed spatial transcriptomics (using VISIUM/10X Genomics) on formalin-fixed paraffin-embedded (FFPE) tissue blocks of paired primary tumors and lung metastasis samples for Ewing sarcoma and osteosarcoma. Comprehensive data analysis is currently ongoing, which will instruct a stepwise incorporation of additional factors into our modular organoid co-culture model, resulting in a better representation of the lung metastatic niche. Further, the analysis of patient-derived material will elucidate the spatial organization of solid tumor lung metastases and contribute to the identification of signaling pathways implicated in lung infiltration. In conclusion, our study not only unravels the complexities of pediatric solid tumor metastasis, but also lays the foundation for exploring the anti-metastatic potential of pathway-specific compounds targeting tumor/lung interactions using the established in vitro lung metastasis models. This study is supported by grant 35353-B of the Austrian Science Fund.
Citation Format: Martha Zylka, Christoph Hafemeister, Lukas Watzke, Ulrike Mann, Didier Surdez, E. Alejandro Sweet-Cordero, Bernadette Liegl-Atzwanger, Matthias Dettmer, Matthias Farlik, Florian Halbritter, Martin Metzelder, Heinrich Kovar, Branka Radic-Sarikas. In vitro modeling of pediatric solid tumor lung metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 196.