This has been successfully demonstrated for a number of therapeutics targeting the protein products of specific genes that are altered in human cancer, including the use of imatinib in chronic myeloid leukemias carrying the BCR-ABL fusion, trastuzumab in ERBB2 (HER2/neu) amplified breast cancer, and vemurafenib in BRAF-mutated melanoma. This evidence concerns the gene ERBB2 and breast cancer.