Mapping of binding domains of four clinically tested anti-EpCAM monoclonal antibodies by use of CHO cells expressing cynomolgus monkey/human and murine/human chimera of EpCAM. a Structure and exon boundaries of EpCAM. Open and shaded areas depict the subdomains used for making monkey/human chimera. b Binding of four clinically tested anti-EpCAM monoclonal antibodies to CHO cells expressing the indicated EpCAM proteins. c Structure of human/murine EpCAM chimera and results of FACS binding analysis (right side). Open areas show human sequences and shaded areas murine sequences. d Example of FACS binding analysis for ING-1 binding to transfected CHO cells. FACS histograms are shown with eight CHO cell transfectants. The bold line shows binding of detection antibodies in the presence of ING-1, the faint line binding in the absence of ING-1. MFI, mean fluorescence intensity. e Comparison of exon 2 sequences from human, cynomolgus and murine EpCAM. The line marks the sequence stretch of highest diversity.