To investigate FOLR1-CAR T cell activation and KB cell death signaling, mock or FOLR1-CAR T cells were co-cultured with KB cells at an E/T ratio of 10:1 for 4 h. (A) ZAP70, AKT, JNK, p38, and ERK associated with TCR signaling were measured by western blot analysis in mock or FOLR1-CAR T cells when incubated alone or with KB cells. The graphs presented ratio of phosphorylation by quantification of the western blot bands from three independent experiments. The data are represented as the mean ratio of densitometry values ± SD. Statistical analysis was performed using the two-sided unpaired t-test (*P<0.05, *P<0.01, and ***P<0.001). (B) Pro-apoptotic proteins PARP, cleaved caspase 8, caspase 9, caspase 3, and tBid were measured in KB cells by western blot analysis. Experiments were repeated three times with similar results.