Anti-PD-1 elicits regression of undifferentiated pleomorphic sarcomas with UV-mutation signatures.

Undifferentiated pleomorphic sarcoma (UPS), an aggressive soft-tissue sarcoma of adults, has been characterized by low tumor mutational burden (TMB) and high copy number alterations. Clinical trials of programmed death-1 (PD-1) blockade in UPS have reported widely varying efficacy. We describe two patients with recurrent scalp UPS that experienced clinical benefit from PD-1 blockade. These tumors had high TMB with a UV-induced mutational pattern. Analysis of additional head and neck UPS cases identified five out of seven tumors with high TMB and an ultraviolet (UV) mutational signature. Head and neck UPS tumors also had increased programmed death-ligand 1 (PD-L1) expression and CD8+ T cell infiltration as compared with UPS tumors arising from other sites. In summary, we found that UPS tumors of the head and neck, but not elsewhere, have a PD-L1+, T-cell-inflamed tumor microenvironment and high TMB, suggesting that these tumors represent a distinct genetic subgroup of UPS for which immune checkpoint inhibitor therapy might be effective.

Pathways of immune exclusion in metastatic osteosarcoma are associated with inferior patient outcomes.

BACKGROUND: Current therapy for osteosarcoma pulmonary metastases (PMs) is ineffective. The mechanisms that prevent successful immunotherapy in osteosarcoma are incompletely understood. We investigated the tumor microenvironment of metastatic osteosarcoma with the goal of harnessing the immune system as a therapeutic strategy. METHODS: 66 osteosarcoma tissue specimens were analyzed by immunohistochemistry (IHC) and immune markers were digitally quantified. Tumor-infiltrating lymphocytes (TILs) from 25 specimens were profiled by functional cytometry. Comparative transcriptomic studies of distinct tumor-normal lung 'PM interface' and 'PM interior' regions from 16 PMs were performed. Clinical follow-up (median 24 months) was available from resection. RESULTS: IHC revealed a statistically significantly higher concentration of TILs expressing immune checkpoint and immunoregulatory molecules in PMs compared with primary bone tumors (including programmed cell death 1 (PD-1), programmed death ligand 1 (PD-L1), lymphocyte-activation gene 3 (LAG-3), T-cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), and indoleamine 2,3-dioxygenase (IDO1). Remarkably, these lymphocytes are excluded at the PM interface compared with PM interior. TILs from PMs exhibited significantly higher amounts of PD-1 and LAG-3 and functional cytokines including interferon-γ (IFNγ) by flow cytometry. Gene expression profiling further confirmed the presence of CD8 and CD4 lymphocytes concentrated at the PM interface, along with upregulation of immunoregulatory molecules and IFNγ-driven genes in the same region. We further discovered a strong alternatively activated macrophage signature throughout the entire PMs along with a polymorphonuclear myeloid-derived suppressor cell signature focused at the PM interface. Expression of PD-L1, LAG-3, and colony-stimulating factor 1 receptor (CSF1R) at the PM interface was associated with significantly worse progression-free survival (PFS), while gene sets indicative of productive T cell immune responses (CD8 T cells, T cell survival, and major histocompatibility complex class 1 expression) were associated with significantly improved PFS. CONCLUSIONS: Osteosarcoma PMs exhibit immune exclusion characterized by the accumulation of TILs at the PM interface. These TILs produce effector cytokines, suggesting their capability of activation and recognition of tumor antigens. Our findings suggest cooperative immunosuppressive mechanisms in osteosarcoma PMs including immune checkpoint molecule expression and the presence of immunosuppressive myeloid cells. We identify cellular and molecular signatures that are associated with patient outcomes, which could be exploited for successful immunotherapy.