ERBB2 and breast cancer: Given the observed association between ITGB3 expression and TGF-β activity (Figure 2B,C), we investigated the therapeutic potential of the ITGβ3 inhibitor, cilengitide, and its effect on TGF-β signalling in Trastuzumab-resistant HER2-positive breast cancer cell lines, SKBR3-R and HCC1954-R.