Objective: To observe the effect of calcium-activated neutral proteases 2( calpain-2) on proteolysis of integrin β4 in breast cancer cell line,MCF7. Methods: Plasmids of GIPZ lentiviral shRNAmir combined with shRNA and microRNA( miRNA) technology were transfected into MCF7 cells to silence the expression of calpain-2. The puromycin was used to screen MCF7 with 4 passages to acquire the stable calpain-2-silenced cell lines. The transfected rates were evaluated with immunofluorecence method under microscope,a...