Investigating effects of AMPK activation on breast cancer cell signaling and survival, we found that breast cancer cell lines with amplification and over-expression of HER2 or EGFR are 2- to 5-fold more sensitive to cytotoxic effects of AICAR, a canonical pharmacological activator of AMPK, than breast cancer cell lines lacking HER2 or EGFR overexpression. The gene discussed is ERBB2; the disease is breast cancer.