Osteosarcoma cells secrete CXCL14 that activates integrin α11β1 on fibroblasts to form a lung metastatic niche.

Cooperation between primary malignant cells and stromal cells can mediate the establishment of lung metastatic niches. Here, we characterized the landscape of cell populations in the tumor microenvironment in treatment-naïve osteosarcoma using single cell RNA-sequencing and identified a stem cell-like cluster with tumor cell-initiating properties and pro-metastatic traits. CXCL14 was specifically enriched in the stem cell-like cluster and was also significantly upregulated in lung metastases compared to primary tumors. CXCL14 induced stromal reprogramming and evoked a malignant phenotype in fibroblasts to form a supportive lung metastatic niche. Binding of CXCL14 to heterodimeric integrin α11β1 on fibroblasts activated actomyosin contractility and matrix remodeling properties. CXCL14-stimulated fibroblasts produced TGFβ and increased osteosarcoma invasion and migration. Monoclonal antibodies targeting the CXCL14-integrin α11β1 axis inhibited fibroblast TGFβ production, enhanced CD8+ T-cell-mediated antitumor immunity, and suppressed osteosarcoma lung metastasis. Taken together, these findings identify crosstalk between osteosarcoma cells and fibroblasts that promotes metastasis and demonstrate that targeting the CXCL14-integrin α11β1 axis is a potential strategy to inhibit osteosarcoma lung metastasis.