ERBB2 and ovarian carcinoma: incorporated CD137 (4-1BB) in chA21 CAR-T cells to create second generation chA21-4-1BBz CAR-T cells highly specific for cells overexpressing human epidermal growth factor receptor 2 (HER2) (i.e., SKOV3—human ovarian cancer, and NCI-N87—human gastric cancer).