Metastasis-initiating osteosarcoma subpopulations establish paracrine interactions with both lung and tumor cells to create a metastatic niche
Osteosarcoma is an aggressive and deadly bone tumor, primarily afflicting children, adolescents, and young adults. Poor outcomes for osteosarcoma patients are intricately linked with the development of lung metastasis. While lung metastasis is responsible for nearly all deaths caused by osteosarcoma, identification of biologically defined, metastasis-targeting therapies remains elusive because the underlying cellular and molecular mechanisms that govern metastatic colonization of circulating tumor cells to the lung remains poorly understood. While thousands of tumor cells are released into circulation each day, very few can colonize the lung. Herein, using a combination of a novel organotypic metastasis in vitro model, single-cell RNA sequencing, human xenograft, and murine immunocompetent osteosarcoma models, we find that metastasis is initiated by a subpopulation of hypo-proliferative cells with the unique capacity to sustain production of metastasis promoting cytokines such as IL6 and CXCL8 in response to lung-epithelial derived IL1a. Critically, genomic and pharmacologic disruption of IL1 signaling in osteosarcoma cells significantly reduces metastatic progression. Collectively, our study supports that tumor-stromal interactions are important for metastasis, and suggests that metastatic competency is driven, in part, by the tumor cell's ability to respond to the metastatic niche. Our findings support that disruption of tumor-stromal signaling is a promising therapeutic approach to disrupt metastasis progression. Overall design: Single cell RNAseq was performed on osteosarcoma patient derived xenografts (PDX) and cell culture models. The pdx models are OS-17 lines and either represent primary tibial tumors or lung metastses.