The IC50 value was less than 8 μM in MCF-7 cells and less than 20 μM in MX-1 cells.Peptide exhibited relatively higher cytotoxicity against breast cancer cells than against normal cells (IC50 > 60 μM).In MCF-7 cells, significant apoptotic activity was detected by annexin V translocation, DAPI staining, and the activation of caspase-9 and cleavage of PARP. This evidence concerns the gene CASP9 and breast carcinoma.