Moreover, when encountering antigens, the infused CAR T cells can be activated and expanded by over one hundred- to thousand-fold to cause more severe toxicities, such as what has already been reported for the high-affinity HER2/neu (ErbB2) CAR derived from the humanized monoclonal antibody trastuzumab to treat a colon cancer patient (Morgan et al., 2010). The gene discussed is ERBB2; the disease is malignant colon neoplasm.