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  • Title: Activation of inositol phospholipid signaling and Ca2+ efflux in human breast cancer cells by bombesin.
    Author: Patel KV, Schrey MP.
    Journal: Cancer Res; 1990 Jan 15; 50(2):235-9. PubMed ID: 2153048.
    Abstract:
    Members of the bombesin-related family of peptides (BRPs) are mitogenic for a variety of cell types; however, a role for these peptides has not been previously described in human breast cancer. Early membrane receptor signal transduction mechanisms associated with bombesin action include phospholipase C-mediated inositol phospholipid hydrolysis and the elevation of cytosolic Ca2+ levels. We have investigated a potential role for BRPs in breast cancer by studying their effect on phospholipid hydrolysis, 45Ca2+ efflux, and cell growth in the human breast cancer cell line MCF-7. Bombesin stimulated a dose-dependent increase in the hydrolysis product inositol monophosphate during 1 h with a half-maximal effect around 1 nM. A transient increase in inositol trisphosphate in response to bombesin was also apparent at 2 min. Two distinct bombesin receptor antagonists inhibited this bombesin-induced phospholipid hydrolysis. Both bombesin- and gastrin-releasing peptide also stimulated a dose-related increase in inositol phosphate production in T47D cells, a different human breast cancer cell line. The efflux of 45Ca2+ from prelabeled MCF-7 cells was also stimulated by bombesin. This apparent cellular Ca2+ mobilization was partly dependent on extracellular Ca2+ and was inhibited by Ni2+. Despite this activation of putative mitogenic signaling pathways, bombesin had no effect on either proliferation or DNA synthesis in MCF-7 cells. These data implicate a functional role for BRPs in human breast cancer.
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