Adolescent bone sarcomas have distinct immune signatures and intercellular communication networks

Ewing and osteosarcoma are bone sarcomas that occur predominantly in adolescents. In the setting of metastatic or recurrent disease, overall prognosis is poor. While immunotherapy is effective for some adult soft tissue sarcoma, limited success has been achieved with immunotherapy for pediatric bone sarcomas. To better understand antitumor immunity in Ewing and osteosarcoma patients, we performed single-cell RNAseq on peripheral blood and tumor infiltrating immune populations using 10X Genomics droplet-based approach. We also included peripheral blood from healthy adolescent blood donors as a comparator. Utilizing these transcriptional profiles, we characterized tumor infiltrating CD8+ T cells and myeloid cells and identified intercellular communication networks in both primary and recurrent disease. In total, we generated single-cell transcriptional profiles from sorted live CD45+ immune cells from paired blood and tumor samples from 4 patients with Ewing sarcoma and 4 patients with osteosarcoma. Among these, 2 patients had primary disease and 2 patients had recurrent disease from both Ewing and osteosarcoma. We also generated single-cell transcriptional profiles from PBMC obtained from 4 healthy adolescent blood donors.