Abstract: Objective To investigate the sensibility of 17βestradiol(E2)-transformed MCF-10A mammary epithelial cells in response to E2 stimulation and the role of calpain (CANP) in the E2-induced effect, so as to understand the mechanism underlying the E2 signaling. Methods E2-transformed MCF-10A mammary epithelial cells were prepared and used as a model system. Western blotting was employed to observe proteolysis of focal adhesion kinase (FAK), a sensitive calpain substrate, to access calpain activity, and wound healing assay was performed to investigate cell migration. Calpain inhibitor was used to understand a possible role of calpain in the E2-induced effect. Results In non-transformed MCF-10A cells, focal adhesion kinase (FAK) was expressed primarily in the form of wild type, while in E2(50 nmol/L)- transformed cells FAK was significantly proteolyzed, indicating increased activity of calpain. Furthermore, transformed cells showed increased migration as compared with control (P<0.01). Treatment of transformed cells with E2 (10 nmol/L) triggered further truncation of FAK and enhancement of migration (P<0.01), while non-transformed cells were not sensitive to E2 stimulation. Additionally, pre-treatment of transformed cells with calpain inhibitor-1 (ALLN, 10 μmol/L) abrogated E2-enhanced FAK processing and migration (P<0.01). Conclusion Transformed MCF10-A mammary epithelial cells displays increased responsiveness to E2 stimulation, and this effect may be mediated through activation of calpain, indicating an active E2-CANP-FAK signaling in the transformed cells.

Key words: 17β-estradiol, transformation, sensibility, calpain, mammary epithelial cell