ERBB2 and leukemia: For example, over-expression of ErbB2 (v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2) in breast cancer is treated with trastuzumab [43], the BCR/ABL fusion protein is highly sensitive to imatinib in the case of leukemia [41] and activating mutations of epidermal growth factor receptor (EGFR) seem to correlate with the responsiveness to gefitinib [42].