ERBB2 and breast cancer: Considering that trastuzumab-induced inhibition of HER2 ECD cleavage precedes trastuzumab-induced down-regulation of cell surface-associated HER2 [46,47], we speculated that concurrent supplementation with oleuropein aglycone may sensitize breast cancer cells to the well-known down-regulatory actions of trastuzumab on HER2 [50,51].