Unveiling the role of osteosarcoma-derived secretome in premetastatic lung remodelling

Lung metastasis represents the leading cause of osteosarcoma-related death. Progress in preventing lung metastasis is pretty modest due to the inherent complexity of the metastatic process and the lack of suitable models. Herein, we provide mechanistic insights into how osteosarcoma systemically reprograms the lung microenvironment for metastatic outgrowth using metastatic mouse models and a multi-omics approach. We found that osteosarcoma-bearing mice or those preconditioned with cell-secretome harbour profound lung structural alteration with airways damage, inflammation, neutrophil infiltration, and remodelling of the extracellular matrix with deposition of fibronectin and collagen by stromal activated fibroblasts for tumour cell adhesion. These changes, supported by transcriptomic and histological data, promoted and accelerated the development of lung metastasis. Comparative proteome profiling of the cell secretome and mouse plasma identified a large number of proteins engaged in the extracellular-matrix organization, cell-matrix adhesion, neutrophil degranulation, and cytokine-mediated signalling, which were consistent with the observed lung microenvironmental changes. Moreover, we identified EFEMP1, a secreted extracellular matrix glycoprotein, as a potential risk factor for lung metastasis and a poor prognosis factor in osteosarcoma patients.