Trogocytosis of GD2 by natural killer cells reduces NK cell-mediated cytotoxicity against human neuroblastoma cells

Combination immunotherapy of natural killer (NK) cells with anti-GD2 monoclonal antibody (dinutuximab) improves murine survival in neuroblastoma and is under clinical trial. Trogocytosis, the transfer of surface molecules between immune cells, may negatively affect immunotherapy but has not been described for neuroblastoma. Human NK cells were incubated with neuroblastoma cells (CHLA-255-Fluc, SMS-KCNR-Fluc) +/-dinutuximab, analyzed by flow cytometry, and visualized by live-cell microscopy. Transwell assays determined the role of contact between cells. NK cell population cytotoxicity was compared. Immunodeficient mice were orthotopically implanted with neuroblastoma cells and treated with NK cells and dinutuximab. Xenograft tumors were analyzed by flow cytometry. In vitro, neuroblastoma cells (CD45-GD2+) incubated with NK cells (CD45 + GD2-) revealed a CD45 + GD2+ population by flow cytometry, which significantly increased with dinutuximab. Live-cell microscopy demonstrated acquisition of neuroblastoma GD2 on NK cell surfaces (GD2 + NK cells). Transwell assays demonstrated that trogocytosis requires direct cell-to-cell contact. GD2 + NK cells were less cytotoxic than GD2-NK cells against neuroblastoma. In vivo, neuroblastoma xenografts treated with NK cells and dinutuximab resulted in GD2 + NK cells. We demonstrate trogocytosis in neuroblastoma treated with NK cells, which was augmented by dinutuximab. GD2 + NK cells are less cytotoxic than GD2-NK cells against neuroblastoma. Trogocytosis may diminish the effect of NK cell based anti-GD2 immunotherapy in neuroblastoma.