To determine the specific cytotoxicity of HER2 hCART41BBζ and EGFR hCART41BBζ  against HER2 and EGFR expressing breast cancer (low HER2 expressing BT20 and MB231 and high HER2 expressing SKBR3 cell lines), pancreatic cancer, prostate cancer and glioblastoma cell lines, the effectors were tested in 51Cr release assays at E:T of 10:1 (Figure 4A). The gene discussed is ERBB2; the disease is breast cancer.