[Background] Invariant natural killer T (iNKT) cells play a central role in activating innate and acquired anti-tumor immunity. Activated iNKT cells enhance the antibody-dependent cell-mediated cytotoxicity (ADCC) of NK cells mediated by anti-GD2 monoclonal antibody (mAb) against neuroblastoma. While iNKT cells are competent effector cells against neuroblastoma, their scarcity in the peripheral blood and lack of ADCC capability are significant limitation. To circumvent the limited number of iNKT cells, we developed induced pluripotent stem cell-derived NKT (iPS-NKT) cells capable of generation and proliferation ex vivo. iPS-NKT cells exhibit NK-like cytotoxicity; however, their ability to mediate ADCC remains unclear.
[Aim] To investigate the ADCC of iPS-NKT cells and the therapeutic efficacy of combining anti-GD2 mAb and iPS-NKT cells against neuroblastoma.
[Methods] iNKT and iPS-NKT cells were generated using established protocols. The ADCC was evaluated through cytotoxicity assays, degranulation (CD107a) assays, and cytokine secretion measurements, including tumor necrosis factor, granzyme B, and interferon-γ. The role of Fcγ receptors and different anti-GD2 mAbs (14.G2a or ch14.18) in ADCC was also examined. In vivo, the efficacy of intratumoral administration of iPS-NKT cells and anti-GD2 mAb (ch14.18) was tested using a subcutaneous NB mouse model. Four groups were compared: untreated, ch14.18 alone, iPS-NKT cells alone, and the combination therapy group.
[Results] Unlike iNKT cells, iPS-NKT cells expressed CD16 and exhibited potent degranulation and cytokine production upon anti-GD2 mAb stimulation. Although iPS-NKT cells also expressed other Fcγ receptors, CD32 and CD64, ADCC was observed only when stimulated with CD16. Chimeric anti-GD2 mAb ch14.18 enhanced ADCC and degranulation responses more efficiently than murine 14.G2a. In vivo, combining iPS-NKT cells and ch14.18 significantly suppressed tumor growth compared to monotherapies or untreated controls.
[Conclusions] iPS-NKT cells demonstrate robust CD16-mediated ADCC. The combination of iPS-NKT cells and anti-GD2 mAb is a promising immunotherapeutic approach for neuroblastoma.