NTRK1 and cancer: Sprouty homolog 2 (Spry2), a member of the sprouty family, contains a carboxyl-terminal cysteine-rich domain essential for the inhibition of receptor tyrosine kinase signaling (10) Spry2 can function as a regulator of mitogen-activated protein kinase signaling, which plays a crucial role in the regulation of cancer cell invasion (11,12).