Spatial profiling identifies tumor-associated stroma enrichment and MIF as potential immunotherapy targets in primary Ewing sarcomas.

PURPOSE The Tumor Microenvironment (TME) has a vital role in cancer survival and progression, and may play roles in drug resistance and immune escape. To date, few studies have detailed the TME of Ewing sarcoma (EwS). EXPERIMENTAL DESIGN We performed spatially resolved transcriptomics of primary treatment-naïve EwS tumor biopsies from patients with or without clinical metastasis, complemented by high-plex spatial proteomic analysis. RESULTS We discovered greater stromal enrichment in localized EwS primary tumors compared to metastasis-associated EwS primary tumors. Through spatial ligand-receptor analysis, we show that the stromal enriched regions harbor unique extracellular matrix related cytokines, immune recruitment and proinflammatory microenvironmental signals, implying EwS stroma may play an anti-tumor role by acting as an immune recruitment center. All EwS tumors expressed pro-tumorigenic MIF-CD74 immune signaling connectivity, suggesting a potential immune-evasive mechanism. CONCLUSIONS In addition to the immune recruitment role of tumor-associated stroma, our findings provide spatial insight into the TME of EwS and provide a rationale for the preclinical investigation of MIF as a potential target for Ewing sarcoma immunotherapy.