Antitumor effect of MAb EMD 55900 depends on EGF-R expression and histopathology.

The proliferative stimulus of the epidermal growth factor (EGF) in human epithelial cells is mediated by its binding to the external domain of the EGF receptor (EGF-R). The purpose of this study was to investigate whether growth arrest of tumors treated with anti-EGF-R MAb (EMD 55900) was dependent on EGF-R expression and distinct histopathologic criteria of those neoplasms. Nine different adenocarcinomas, squamous cell carcinomas and two neoplastic epithelial cell lines (A431 and Detroit 562), which were characterized by high EGF-R expression, were xenotransplanted onto NMRI-nu/nu mice and treated with an anti-EGF-R antibody (EMD 55900). Results revealed that EGF-R expression and distinct histopathologic growth patterns play an important role for the therapeutic effect of the EGF-R antibody treatment. Tumors with high epithelial cellularity and little connective tissue responded to EMD 55900 treatment to a greater degree of growth reduction than tumors with lower cellularity. These results will be helpful for evaluation of patients who would benefit from tumor therapy with anti-EGF-R antibody.