CASP3 and neoplasm: To explore the mechanism underlying NK-Exo-induced cytotoxicity against tumor cells, we performed ELISA and western blotting, which showed that NK-Exo treatment increased the levels of cleaved caspase-3 and cleaved PARP (Figure 5B) and indicated that NK-Exo induced apoptosis-signaling pathways in tumor cells and initiated cell death.