AKT1 and breast carcinoma: In SK-BR-3 breast cancer cells transiently exposed to HER2-VIA, phosphorylation of HER2 on sites 877, 1,221, 1,222, and 1,248 as well as phosphorylation of the downstream HER2 signaling molecules AKT and ERK was detected (Figure 3, lanes 1 to 5).