Among the other eight cell lines with high CD137L mRNA expression, two cell lines (HCC‐827 and NCI‐H2170) did not exhibit significant changes in the CD137L expression following stimulation with IFN‐γ, whereas the other six cell lines displayed various levels of enhanced CD137L expression (Fig 4(d)). This evidence concerns the gene TNFSF9 and hepatocellular carcinoma.