Epidermal growth factor receptor inhibitors are effective in blocking HER2 mediated signalling in HER2 overexpressing breast cancer cell lines that co-express the EGFR, and combinations of EGFR and HER2 targeted agents have been shown to have additive or synergistic effects on growth inhibition (Moasser et al, 2001; Moulder et al, 2001; Normanno et al, 2002; Anido et al, 2003). Here, ERBB2 is linked to breast cancer.