Our results support that OA co-treatment with trastuzumab synergistically enhanced apoptotic cell death by promoting DNA fragmentation through caspase-3-dependent PARP cleavage; both the expression and nuclear accumulation of p27Kip1 and the inhibition of the AKT and MAPK signaling pathway play a key role in the onset and progression of HER2-related breast cancer in BT-474 and SKBR3 cells [30]. This evidence concerns the gene CASP3 and breast cancer.