Abstract: Objective To investigate the effects of estrogen（E2）on the gene expression of calpain1 and calpain activity, and a possible role of calpain in the E2-enhanced survival in breast cancer cells. Methods Human breast cancer cell line MCF-7 was employed as a model system. RT-PCR was used to analyze the levels of mRNA expression and western blotting was employed to access proteolysis of FAK. Serum starvation was used to induce cell death, and Trypan blue staining and cell counting were used to evaluate cell viability. Results Stimulation of MCF-7 cells with E2 led to increased mRNA expression of calpain1 and calpain activity. E2 also increased cell viability by 14.29 % (P<0.05) during serum starvation, while calpain inhibitors significantly suppressed the E2-increased expression of calpain1 mRNA, calpain activity , and cell viability by 19.17% (P<0.05). Conclusion E2 causes increased expression of calpain1 mRNA and calpain activity, and this may contribute to the E2-stimulated survival during serum starvation in MCF-7 cells.

Key words: estrogen, calpain, gene expression, cell survival, breast cancer cells