This suggests that NK-1 receptor antagonists block the NK-1 receptors expressed by tumor cells and that the structurally very different molecules piperidine (L-733,060), L-tryptophan (L-732,138) and morpholine (aprepitant) exert the same antitumor action (these molecules only have their specificity for the NK-1 receptor in common). The gene discussed is TACR1; the disease is neoplasm.