Thus, a number of IgG1 mAbs, such as Trastuzumab, Cetuximab and Rituximab, directed against the HER-2/neu, EGF-R, or the B cell-restricted antigen CD20, have been developed and were used for the treatment of different tumor types, such as colorectal cancer (CRC), head and neck squamous cell carcinoma (HNSCC), Non-Hogkin lymphoma and chronic lymphatic leukemia (CLL), respectively. The gene discussed is ERBB2; the disease is B-cell chronic lymphocytic leukemia.