ERBB3 and breast cancer: The interactions between gefitinib and NO discussed above are also relevant in the context of HER3 as gefitinib induces the formation of inactive EGFR/HER2 and EGFR/HER3 dimers, along with inhibiting the formation of active HER2/HER3 dimers in HER2-amplified breast cancer (Anido et al., 2003).