Immunosuppressive tumor microenvironment of osteosarcoma [scRNA-seq]

Osteosarcoma is the most common malignant bone tumor in children, characterized by a high degree of genomic instability, resulting in copy-number alterations and genomic rearrangements without disease-defining recurrent mutations. Clinical trials based on molecular characterization have failed to find new effective therapies or improve outcomes over the last 40 years. To better understand the immune microenvironment of osteosarcoma, we performed single-cell RNA sequencing on six tumor biopsy samples, combined with a previously-published cohort of six samples. Additional osteosarcoma samples were profiled using spatial transcriptomics for validation of discovered subtypes and to add spatial context. Analysis revealed immunosuppressive cells, including myeloid-derived suppressor cells (MDSCs), regulatory and exhausted T-cells, and LAMP3+ dendritic cells. Using cell-cell communication modeling, we identified robust interactions between MDSCs and other cells, leading to NF-?B upregulation and an immunosuppressive microenvironment, as well as interactions involving regulatory T-cells and osteosarcoma cells that promoted tumor progression and a proangiogenic niche. Overall design: Primary, treatment-naïve pediatric osteosarcoma biopsies were gathered from six patients at Connecticut Children's Medical Center or Children's Hospital Colorado. Tissues were dissociated into individual cells for single-cell RNA sequencing. Data was combined with single-cell RNA sequencing of six additional treatment-naïve pediatric osteosarcoma biopsy samples previously described in Liu et al. (Front Oncol, 2021) downloaded from the Gene Expression Omnibus (GSE162454).