We found that endogenous kinase activity of JNK is significantly increased in the tumor samples of both adult- and juvenile-type GCT as well as GCT cell lines COV434 and KGN in comparison to other types of non-neoplastic granulosa cells (HGrC1, HLGC and SIGCs) (Fig. 6a, b and Supplementary Figure-6). This evidence concerns the gene MAPK8 and granular cell tumor.