...we assessed the activity of cetuximab in five gastric cancer cell lines (AGS, AZ521, Hs746T, LMSU and MKN1). The viability of two of these cell lines, AZ521 and MKN1, was significantly reduced by cetuximab treatment. High expression and secretion levels of the EGFR-binding ligand, amphiregulin (AREG), were associated with cetuximab responsiveness....In the present study, we detected high levels of secreted AREG in the MKN28 cells and used the model to classify this cell line as cetuximab-responsive. AREG secretion was not detectable in the cetuximab-resistant cell line MKN45, which falls into the non-responder category due to the elevated MET activation status.