Childhood Cancer Data Initiative Annual Symposium (Abstract Registration): Submission #66

Abstract: Pulmonary metastasis is the leading cause of mortality in human and canine osteosarcoma (OS) patients, yet the contribution of lung-resident type II pneumocytes (TIIPs) to metastatic progression is under-defined. This study characterizes the distribution of pneumocytes in the OS lung metastasis microenvironment, defines the consequences of TIIP-OS crosstalk, and identifies a therapeutic strategy to limit pulmonary metastatic progression. Spatial transcriptomics and complementary IHC staining of human, canine, and murine OS lung metastases showed increased TIIP accumulation at the tumor:non-tumor interface compared to distal lung parenchyma. Indirect co-culture of human primary TIIPs with MG63.2 OS cells significantly increased tumor cell proliferation, an effect reproduced with TIIP-conditioned media, suggesting that soluble TIIP-derived factors are pro-tumorigenic. RNA sequencing of co-cultured TIIPs showed enrichment of the p53 pathway, consistent with an injury/stress response resembling idiopathic pulmonary fibrosis. Cytokine profiling and Enrichr pathway analysis identified a pro-fibrotic secretome as a dominant feature of TIIP-OS crosstalk. Targeting TGF-β-mediated fibrosis with a dual integrin inhibitor reduced K7M2 OS proliferation in TIIP co-culture but not in monoculture, suggesting that the anti-proliferative effect is mediated through disruption of TIIP-OS crosstalk. A K7M2-pEGFP experimental metastasis model treated with 5 mg/kg or 25 mg/kg inhibitor showed significant dose-dependent reductions in metastases versus vehicle control. These findings provide the first cross-species characterization of TIIP spatial distribution within the OS pulmonary metastatic niche, demonstrating that TIIPs establish a growth-permissive, pro-fibrotic crosstalk with tumor cells. Disrupting this crosstalk represents a promising therapeutic strategy to limit metastatic progression and improve survival outcomes for OS patients.