Direct inhibitory effects of somatostatin (analogues) on the growth of human breast cancer cells.

Various hormones and growth factors are involved in the growth regulation of breast (tumor) cells. In this report we show for the first time that an analogue of the neuropeptide somatostatin (Sandostatin) can also influence the proliferation of human breast cancer cells (MCF-7), namely, in an inhibitory fashion. With respect to dose-response relationship a bell-shaped curve was observed with the maximal inhibition of tumor cell growth at a sharply defined amount of Sandostatin (10 nM). The same effects were found with the natural hormone somatostatin-14 and another analogue (CGP 15-425). These results, together with the observation that high affinity binding sites for an iodinated derivative of Sandostatin are present in MCF-7 cells, support the conclusion that somatostatin and analogues act directly on breast cancer cells.