Therapeutic

potential of epidermal growth factor receptor–related protein In Response: We respectfully disagree with some of the issues raised by Reiter et al. that imply that epidermal growth factor receptor–related protein (ERRP) lacks therapeutic value. Our studies show the pan-erbB inhibitory nature of ERRP, which inhibits the growth of human colon- and pancreatic cell-derived tumors (1, 2). Although the genetic identity of human ERRP is not known, reverse transcription-PCR analyses indicate that the rat ERRP transcript is a ‘chimera ’ formed with EGFR and peptidase D mRNAs (2). The region of ERRP mRNA corresponding to EGFR encodes a polypeptide containing three of the four ectodomains of EGFR. The peptidase