TACR1 and metastatic neoplasm: It is also known that the expression of the full-length isoform of the NK-1R reduced metastasis, whereas the activation of the truncated form increased it [57]; that SP promoted the migration of cancer cells by modulating the level of intracellular Ca++ [58]; and that in metastatic tumors, an increase in SP/NK-1R staining occurred [30].