NTRK1 and cancer: These include receptor tyrosine kinase (RTK) family receptors, where exosomes shed by cancer cells can internalize into distant cancer cells in a paracrine fashion through binding with RTKs (Li et al., 2010; Koumakpayi et al., 2011; Nakase et al., 2015), cell-surface proteoglycans which macropinocytose ligands containing closely spaced, basic amino acids such as lysine, arginine, and histidine (Magzoub et al., 2006), and G-protein coupled receptors (GPCRs).