Mechanism of growth inhibition by calpain inhibitor in MCF-7 cells

Background: A calpain inhibitor, calpeptin, inhibited the cell growth of ER (estrogen receptor) positive breast cancer cells, such as MCF-7, T-47D, and ZR-75-1 in the presence of E-2. The mechanism of this inhibition has not been clarified yet. Materials and Methods: MCF-7 cells were employed to investigate the mechanism of the inhibition. We studied the effect of calpeptin on the secretion of insulin-like growth factor-I (IGF-I) and transforming growth factor (TGF-alpha). Results. The secretion of IGF-I or TGF-alpha was not changed by calpeptin either in the presence or absence of E-2. Moreover, the binding of IGF-I or TGF-alpha to MCF-7 cells augmented by the addition of E-2 was not affected by calpeptin. Conclusions: These results indicated that the inhibition of cell growth in MCF-7 by calpeptin was not due to the modulation of autocrine growth factors and their receptors.