Here, we describe the preclinical characterization of the in vitro and in vivo properties of a novel TAT, HER2-TTC, as well as its antitumor efficacy in various HER2-positive human xenograft models, including the s.c. KPL-4 breast cancer and Calu-3 lung cancer mouse models and the intratibial BT-474 mouse model mimicking bone-metastasized breast cancer. The gene discussed is ERBB2; the disease is lung carcinoma.