In GIST, positive expression of Stem Cell Growth Factor (SCGF) has been associated with response to the tyrosine kinase inhibitor imatinib (86), and exosomal expression of proteins Sprouty homolog 4 (SPRY4) and tyrosine protein kinase KIT have been associated with increased risk of tumor progression (83). The gene discussed is SPRY4; the disease is gastrointestinal stromal tumor.