Bombesin stimulates intracellular Ca²⁺ mobilization but not proliferation on human colon cancer cells

Increases in intracellular Ca²⁺ ([Ca²⁺]_i) levels mediated by bombesin (BBS) are believed to be important signals leading to stimulation of DNA synthesis and an increase in cellular proliferative rate. Since the role of BBS on growth of normal or malignant cells in the GI tract is still unclear, we examined whether BBS affects in vitro growth of human colon cancer cells (COLO 320, HCT116 and LoVo). We also examined the effect of BBS on intracellular Ca²⁺ levels to determine if the growth-regulatory effect of BBS is mediated through increases in [Ca²⁺]_i. Levels of [Ca²⁺]_i in response to BBS were measured by single cell fluorescence after loading with fura-2. BBS stimulated the mobilization of [Ca²⁺]_i in COLO 320, LoVo, and HCT116 cells in a dose-dependent fashion, but did not affect in vitro growth. These findings suggest that the BBS-mediated increase in [Ca²⁺]_i does not always correlate with the growth-regulatory effect of BBS.