Neuropeptides are chemoattractants for human tumor cells and monocytes: a possible mechanism for metastasis.

Bombesin (BN), a tetradecapeptide neuropeptide growth factor, is shown to be a potent (ED50 of 5 X 10(-12) M) chemoattractant for human monocytes and small cell lung carcinoma cells (SCCL). These effects are BN receptor-mediated since potencies of several BN analogs to induce chemotaxis and to inhibit [125I-tyr4] BN binding activity correlate well (P less than 0.001). As has been demonstrated for other BN receptor-mediated effects, carboxy-terminal amino acids are required for optimum biological activity. BN is not an exclusive chemoattractant for SCCL cells but was also active in promoting migration of other, but not all, lung tumor cells. Other neuropeptides, such as beta-endorphin, substance P, and arg-vasopressin, are also shown to be chemoattractants for SCCL cells, with EC50's also in the 10(-12) M range. The ability of these ligands to effect monocyte and some tumor cell migration suggest a role for neuropeptides in inflammation and metastasis. In the latter case, tumor cells, in response to neuropeptide chemical gradients, may become localized at specific body sites. Neuropeptide release, in response to cognitive or other stimuli, may thereby modify cell migratory patterns. Additionally, such hormones may influence early developmental events such as tissue organization and histogenesis.