PRF1 and neoplasm: Cytotoxic granules containing Granzyme B and perforin are crucial for the cytotoxic activity of NK cells in killing cancer cells.[27] To investigate the modulation of ALO on the cytotoxic activity of NK cells in vivo, flow cytometry was used to analyze the phenotypes of NK cells in LLC‐derived subcutaneous tumor mouse models from each group (Figure 2A).