Figure 1. Cetuximab induces CD137 upregulation on human NK cells following incubation with EGFR-positive tumor cells.

Peripheral blood from healthy donors was analyzed for CD137 expression on CD3^–CD56⁺ NK cells after 24-hour culture with EGFR-positive tumor cell lines SCC6, PC1, and SCC4, and cetuximab or rituximab. (A) Percentage of NK cells divided by quadrant to delineate subsets of CD3^–CD56^bright and CD3^–CD56^dim expressing CD137 from a representative healthy donor after 24-hour culture with the EGFR-positive tumor cell line PC1 and cetuximab. (B) Percentage of CD137 expression on NK cells from 3 healthy donors after 24-hour culture with the EGFR-positive tumor cell line SCC6, PC1, or SCC4, and cetuximab or rituximab. (C) CD16 expression on NK cells from a 3 healthy donors after 24-hour culture with the EGFR-positive tumor cell line SCC6, PC1, or SCC4, and cetuximab or rituximab. *P < 0.001.