[D-Arg1,D-Trp5,7,9,Leu11]substance P: a novel potent inhibitor of signal transduction and growth in vitro and in vivo in small cell lung cancer cells.

[D-Arg1,D-Trp5,7,9,Leu11]Substance P (SP) was identified out of a panel of novel SP analogues as the most potent inhibitor of small cell lung cancer (SCLC) cell growth. This analogue inhibited proliferation of H-510 and H-69 SCLC cells in liquid culture and in semisolid media (IC50, 5 microM). Colony formation stimulated by multiple neuropeptides, including vasopressin and bradykinin, was also blocked by [D-Arg1,D-Trp5,7,9,Leu11]SP. This new SP analogue inhibited vasopressin- or bradykinin-induced Ca2+ mobilization and mitogen-activated protein kinase activation. Administration of [D-Arg1,D-Trp5,7,9,Leu11]SP inhibited the growth of an H-69 xenograft in nude mice. Our results support the hypothesis that SP analogue broad-spectrum neuropeptide antagonists could be of therapeutic value in SCLC.