CD274 and head and neck squamous cell carcinoma: Cell surface PD-L1 expression was measured by flow cytometry in the presence or absence of IFNγ (20 ng/mL for 24 hr, left panels) and killing of control or IFNγ pre-treated tumor cells (20 ng/mL for 24 hr) by haNKs or PD-L1 CAR haNKs was measured by impedance analysis for human UMSCC-1 (A), UMSCC-11A (B), UMSCC-74B (C), UMSCC-109 (D) and UMSCC-47 (E) HNSCC cells. Representative impedance curves are shown in the central panels, and plots of quantification of effector cell killing (% loss of cell index) at 12 hr are shown in the right panels.