CD155 axis modulation promotes natural killer cell-mediated graft-versus-tumor effects against osteosarcoma

Abstract

Abstract Patients with relapsed/refractory osteosarcoma (OSA) have a poor prognosis with few treatment options. Immunotherapy with allogeneic natural killer (NK) cells after allogeneic bone marrow transplant (BMT) is an attractive approach to employ a graft-versus-tumor (GVT) effect against OSA. However, NK cells have had limited success against solid tumors in vivo. CD155 is overexpressed on OSA and interacts with DNAM-1, an activating ligand, and TIGIT, an inhibitory ligand, on NK cells. The impact of blocking CD155 after allogeneic BMT is unknown. IL-15-expanded C57BL/6 (B6, H-2b) and BALB/c (H-2d) murine NK cells were co-cultured with K7M2 murine OSA (H-2d) after CD155 and CD155 ligand blockade, and analyzed by flow cytometry and cytotoxicity assays. BALB/c mice were also transplanted with T cell depleted allogeneic B6 or syngeneic BALB/c bone marrow, challenged with K7M2 and treated with IL-15-expanded NK cells and CD155 blockade. Allogeneic NK cells showed increased degranulation, interferon-gamma production and cytotoxicity against K7M2 OSA in vitro compared to syngeneic NK cells. NK cell activation and cytotoxicity were further enhanced by CD155 and TIGIT blockade, but decreased with DNAM-1 blockade. In vivo, allogeneic NK cell infusion and anti-CD155 treatment decreased tumor growth and increased survival compared to syngeneic NK cell treatment, without induction of graft-versus-host-disease. CD155 blockade augments NK cell activation, cytotoxicity and GVT effects against OSA without toxicity, suggesting TIGIT is the dominant CD155 checkpoint during allogeneic BMT. CD155 blockade with allogeneic NK cell therapy after BMT may be an effective combination immunotherapy platform for treating relapsed/refractory OSA. Supported by NIH grants (T32 CA009135, R01 CA215461)