Abstract PO-123: Distinct subpopulations of osteosarcoma cells cooperate to establish lung metastases

Abstract

Abstract Four decades of intense multinational efforts to improve outcomes for children and teenagers with osteosarcoma have failed. Today, we still treat patients with a regimen first developed in 1982. The same 35-40% of young people diagnosed with osteosarcoma die from their disease, almost always from complications related to lung metastasis. Believing that therapies targeting lung metastasis could dramatically improve outcomes, we have sought to understand the mechanisms that drive lung colonization in this disease. We previously found that interactions with lung epithelium cause osteosarcoma cells to produce IL6 and CXCL8 and that this activity is necessary for metastasis. Inhibiting IL6 and CXCL8 signaling prevents metastasis entirely in 85% of mice with osteosarcoma. While conducting these studies, we learned that individual tumor cells react differently to signals from lung epithelium. Nearly all the IL6 and CXCL8 produced by osteosarcoma cells come from a small subset of cells. Interactions with pulmonary epithelium cause this discrete subset of tumor cells to produce large quantities of inflammatory cytokines, become strongly p21+, and stop proliferating. Early metastatic lesions consist almost entirely of cells with this phenotype, positioning them to orchestrate the development of the metastatic niche. Thus, we call these hypo-proliferative, cytokine-producing cells that survive early attrition "anchor cells." In the initial stages of metastasis, anchor cells alter the surrounding lung tissue in ways that facilitate subsequent colonization by tumor cells with proliferating phenotypes ("growth cells"). Growth cells then divide to create expanding, clinically-relevant metastasis. Importantly, one can leverage the biology of these anchor cells to develop rational targeting strategies. Anchor cells exhibit profound sensitivity to known senolytic agents. Combining these with conventional therapies (which effectively target growth cells) can eradicate established metastatic lesions and prevent new metastases from forming. These novel findings fundamentally alter our understanding of osteosarcoma and metastasis biology and have direct implications for approaches to treatment. Citation Format: James B. Reinecke, John M. Hinckley, Amy C. Gross, Maren Cam, Sanjana Rajan, Ryan D. Roberts. Distinct subpopulations of osteosarcoma cells cooperate to establish lung metastases [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-123.