TNFSF9 and squamous cell carcinoma: Two adenocarcinoma cell lines (CALU‐1 and A2), one squamous cell carcinoma cell line (NCI‐H1703), and two large cell carcinoma cell lines (NCI‐H661 and PLA‐801D) had no or weak CD137L mRNA expression, whereas CD137L mRNA was highly expressed by the other tested cell lines (Fig 4(a)).