KLF4 and breast cancer: One such drug is lapatinib, a HER2/epidermal growth factor receptor (EGFR) inhibitor that has activity not only in the HER2+ cancers of patients, but also shows efficacy in combination with other agents in basal-like breast cancer models.36, 37 We observed that lapatinib treatment of HER2-amplified tumor cells resulted in the rapid induction of KLF4/5.