Thus, the role of the SP/NK-1R pathway in osteosarcoma can be summarized as follows: (a) SP plasma levels are higher in cancer patients; (b) SP stimulates osteosarcoma cell proliferation in a concentration-dependent manner; (c) osteosarcoma cells overexpress NK-1R and NK-1R antagonists in a concentration-dependent manner, inhibiting proliferation and inducing apoptosis of osteosarcoma cells [13]. This evidence concerns the gene TACR1 and osteosarcoma.