{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"TRK (tropomyosin receptor kinase) A, B, and C are encoded by NTRK1, NTRK2, and NTRK3 genes respectively. Each protein is activated by a different neurotrophin: TRKA is activated by nerve growth factor (NGF), TRKB by brain-derived neurotrophic factor (BDNF), and TRKC by neurotrphin-3 (NT-3). The TRK receptors are a family of tyrosine kinases that regulate synaptic strength and plasticity in the mammalian nervous system. The activation of TRK receptors by ligand binding leads to dimerization, autophosphorylation, and activation of signaling pathways that promote survival and other functional regulation of cells.\nNRTK rearrangements have been identified in a wide range of adult and pediatric tumors. The most common NTRK gene fusions involve NTRK1, NTRK2, or NTRK3 genes and various partner genes, such as ETV6, TPM3, and LMNA. These fusion proteins are constitutively activated, driving oncogenic signaling pathways and promoting tumor growth and survival. Pan-TRK IHC is useful in identifying TRK fusion proteins in cancers."}]}]}