Therefore, VPA may synergize with drugs used in the therapy of HER2-overexpressed BC, like anti-HER2 monoclonal antibodies (e.g., trastuzumab, bevacizumab, lapatinib) or anthracycline and taxane-based neoadjuvant chemotherapy to inhibit HER2-overexpressing BC cell proliferation more effectively. This evidence concerns the gene ERBB2 and breast cancer.