This demonstrates that the caspase-8 activity was due to activation of the CD95 pathway by NK cells, and it also reveals that caspase-8 is not, or not efficiently, activated by granzyme B. When using activated primary human NK cells as effectors, we saw a similar cleavage of the NES-VGPD-mCherry granzyme B reporter and of the NES-ELQTD-mGFP caspase-8 reporter in HeLa cells and in MDA-MB-468 breast carcinoma cells (Figure S1 in Supplementary Material). Here, GZMB is linked to breast carcinoma.