Oxytocin does not induce a rise in intracellular free calcium in human breast cancer cells

Research suggests that oxytocin acts as a growth modulating agent for breas t cancer cells. However, the signaling mechanisms responsible for these mod ulatory effects have not been fully elucidated. In the physiological settin g oxytocin is known to stimulate contraction of myometrial cells in the ute rus and myoepithelial cells in the breast by increasing intracellular free calcium ([Ca2+](i)). The expression of oxytocin receptor mRNA in T-47D brea st cancer cells, and four additional breast cancer cell lines (BT-549, MCF- 7, MDA-MB- 231, ZR-75-1), was confirmed by RT-PCR analysis. Oxytocin-induce d changes in [Ca2+](i) in indo-1 AM loaded T-47D breast cancer cells were m onitored using flow cytometric analysis. In this cell line, oxytocin (0, 1, 10, 100, and 1,000 nM) did not induce a dose-dependent increase in the mea n 405nm/485nm emission ratio. These results indicate that oxytocin signalin g in T-47D breast cancer cells does not appear to involve an increase in [C a2+](i).