NTRK1 and cancer: Although association between the alteration of the NTRK genes and the development of malignant tumors has not been elucidated, it has been reported that if a tumor has the alteration of the NTRK genes (such as solvent front mutation, gatekeeper mutation, and glycine mutation of Asp-Phe-Gly (DFG) at the beginning of the activation loop), it becomes resistant to TRK inhibitors, larotrectinib, and entrectinib (Table 3).