Figure 4.

PD-L1 t-haNK cells preferentially targeted PD-L1^high versus PD-L1^low human breast cancer cell line in vitro. Carboxyfluorescein succinimidyl ester (CFSE)-labeled PD-L1^high MDA-MB-231 was cocultured with CellTrace Violet-labeled PD-L1^low breast cancer cell lines BT549 (A, B), MCF7 (C, D), and T47D (E, F). CellTrace Violet-labeled IFN-γ-treated MDA-MB-231 was cocultured with CFSE-labeled untreated cells (G, H). Flow-sorted PD-L1^high and PD-L1^low MDA-MB-231 cell populations were labeled with CFSE and CellTrace Violet, respectively (I, J). Irradiated PD-L1 t-haNK cells were incubated with the cocultures at different E:T(PD-L1^high):T(PD-L1^low) overnight prior to flow cytometric analysis to determine cell lysis. The flow cytometric plots shown have been stratified to live cells and have been downsampled, such that all the plots for each coculture have the same cell count in every E:T:T ratio. The numbers indicate the cell count for each population in the downsampled plots. Data are representative of two independent experiments for each cell line for panels A–F. E:T, effector to target; IFN, interferon; PD-L1, programmed death-ligand 1; t-haNK, targeting high-affinity natural killer.