Enhanced CD107a expression (degranulation) in NK‐92MI cocultured with cancer cells (first‐round cytotoxic assay) was observed compared to that in naïve NK cells (Fig. S3A–C), and these degranulated NK‐92MI cells showed impaired killing activity in the second‐round cytotoxic assay (Fig. 2J). Here, LAMP1 is linked to cancer.