We have previously reported an increase of both Spry4 mRNA and SPRY4 immunoreactivity (-ir) in KitK641E homozygous (KitK641E/K641E) mice [19], a mouse model of human GIST harboring a K-to-E substitution of the KIT receptor at amino acid 642 [20–22]. Here, SPRY4 is linked to gastrointestinal stromal tumor.