Mevalonate pathway activation in Ewing sarcoma reveals a 3D-specific synergy between statins and BCL-xL inhibition

Bone sarcomas are rare and aggressive pediatric cancers with limited progress in targeted therapy development, partly due to the poor physiological relevance of conventional two-dimensional (2D) culture systems used for preclinical testing. To address this gap, we developed a standardized three-dimensional (3D) culture and drug-testing platform for Ewing sarcoma (ES) and osteosarcoma (OS) that more accurately recapitulates in vivo tumor biology. Notably, gene-expression analyses demonstrated that ES and OS spheroids transcriptionally converge toward patient tumor cell states, underscoring their physiological relevance for preclinical testing. Across 3D spheroids, bioprinted constructs, and patient-derived xenograft (PDX) cultures, we observed a consistent activation and dependency on the mevalonate pathway in ES. Leveraging this platform, we identified a selective therapeutic synergy between statins, which inhibit mevalonate pathway flux, and BCL-xL inhibitors—a vulnerability not detectable in 2D cultures. Importantly, this synergistic interaction was tumor-specific and absent in non-malignant fibroblasts, indicating a favorable therapeutic window. Together, these findings highlight the mevalonate pathway as a targetable metabolic dependency in ES and demonstrate how physiologically grounded 3D models can uncover clinically actionable treatment strategies that remain hidden in traditional 2D systems.