To evaluate whether CD137L expressed on tumor cells was functionally active, CD137L‐expressing HCC‐827 cells were cocultured with T cells in the presence or absence of soluble antihuman CD3 mAb or antihuman CD137 mAb, and the supernatant IFN‐γ concentration was then measured. Here, TNFSF9 is linked to hepatocellular carcinoma.