Mechanistically, substance P (SP) (after binding to the NK-1R) promotes mitogenesis in tumor cells, while Aprepitant (after binding to the same receptor) counteracts the SP-mediated mitogenesis and induces apoptotic mechanisms in these cells (Muñoz and Coveñas, 2013; Munoz et al., 2015). This evidence concerns the gene TAC1 and neoplasm.