TACR1 and cancer: Moreover, for tumor diagnosis, a biopsy is required, and this procedure also induces, albeit on a smaller scale than surgical resection, neurogenic inflammation and pain (in both mechanisms, SP is involved), which could promote the growth and metastatic spread of cancer cells (by mechanisms mediated by the SP/NK-1R system, since the latter cells overexpress the NK-1R, and in addition, the level of SP is increased in cancer patients) [64,73].