Natural Killer cells armed with engineered anti-Her2 antibody show enhanced cytotoxicity against Her2-overexpressing breast cancer
Natural killer (NK)-based immunotherapy has emerged as a novel treatment modality for solid cancers, but immunosuppressive factors within the tumor microenvironment (TME) may hamper NK cell cytotoxicity and clinical efficacy. Previously, we have demonstrated that antibody-dependent cellular cytotoxicity (ADCC)-inducing antibody trastuzumab enhances NK cell activation and cytotoxicity against Her2-overexpressing breast cancer. However, trastuzumab can cause unwanted side effects and the efficacy of combination therapy depends on the ability of both the antibody and NK cells to distribute to the tumor and find their targets.
Here we show an alternative strategy to enhance NK cell cytotoxicity against Her2-overexpressing breast cancer, by pre-arming expanded NK cells with a modified Her2-targeting antibody: Pin-Her2 (CYTEA BIO). Amino-acid substitutions in the Fc region render stable and persistent binding to CD16 on NK cells, ensuring precise target-specific action of Pin-Her2-armed NK cells.
Clinical grade expanded NK cells from peripheral blood of healthy donors were armed with the Pin-Her2 antibody. NK cell degranulation (CD107a) was measured by flow cytometry after 4-hour coculture with breast cancer target cells. Cytotoxicity was measured using a Live-Cell-Imaging system (IncuCyte S3) and fluorescently labelled breast cancer cell lines were cocultured with NK cells with or without the ADCC-inducing antibody trastuzumab. Caspase-3/7 fluorescent dye served as a quantitative read-out for cell death.
Expanded NK cells were efficiently armed with the Pin-Her2-antibody (48,4% ±24,5% of CD16+ NK cells). Similarly to unarmed NK cells combined with trastuzumab, Pin-Her2-armed NK cells show enhanced degranulation against Her2-overexpressing cell line SKBR3 (44,1 and 38,6% CD107a+ NK cells, respectively), compared to unarmed NK cells (12,0%). Moreover, Pin-Her2-armed NK cells induced a more rapid elimination of SKBR3 cells compared to unarmed NK cells, while this effect is not seen in Her2low MCF7 cells. Enhanced killing kinetics of Pin-Her2-armed NK cells allows execution of effector functions before exposure to the immunosuppressive TME. This effect was consistent across NK cell donors and was also observed against additional Her2-expressing cancer cell lines tested by collaborators. Preliminary in vivo data further suggest enhanced anti-tumor activity of Pin-Her2-armed NK cells compared to unarmed NK cells.
These results demonstrate the potential of Pin-Her2-armed NK cells as a single therapy for Her2-overexpressing breast cancers. Future in vivo studies should illustrate the superior cytotoxicity of armed NK cells compared to ADCC-inducing antibodies.