Although trastuzumab provides clinical benefits to certain subpopulation of patients with HER2-positive breast cancer, initial response rate is only about 30% and over 70% initial responders acquire resistance within 1 year of initial treatment [7] which necessitate the study of resistance mechanism and development of novel combination therapies to enhance the anti-tumor efficacy of trastuzumab or prevent the development of acquired resistance. The gene discussed is ERBB2; the disease is neoplasm.