On the other hand, our unpublished data, as well as the results published by the others [21,52], have shown that 1 h of trastuzumab treatment in trastuzumab-sensitive BC cell lines does not have any inhibitory effects on HER3 phosphorylation and PI3K activity; however, it drastically reduces the AKT phosphorylation. This evidence concerns the gene ERBB3 and breast cancer.