TGF-ALPHA AND IGF-I EFFECTS ON CALCIUM-ION TRANSIENTS IN HUMAN BREAST-CANCER CELLS

In order to evaluate the potential role of calcium as an intracellular messenger for IGF-I and TGF-alpha action on breast cancer cell proliferation, we determined whether these growth factors induce any change in [Ca2+]i using fura-2 loaded cells. The hormone independent BT-20 and MDA-MB-231 cells were refractory to the mitogenic actions of exogenously added IGF-I and TGF-alpha. TGF-alpha administration, however, stimulated [Ca2+]i transients in the BT-20 cells. IGF-I and TGF-alpha stimulated DNA synthesis in the MCF-7 and T47D cells. These growth factors did not, however, stimulate any changes in [Ca2+]i in these cells. These data support the idea that receptor-mediated phospholipid hydrolysis does not serve a major signalling function for driving human breast cancer cells into DNA synthesis.