ERBB2 and cancer: Specific cytotoxicity mediated by HER2 hCART41BBζ, hCARTICOSζ or hCARTICOS-27ζ compared to hCART transduced with GFP (hCARTGFP) or ζ (hCARTζ), untransduced HER2 COATC and HER2 BATs was measured by using RTCA against low HER2 expressing MB231 cancer cells.