Detection of squamous cell carcinoma xenografts in nude mice by radiolabeled monoclonal antibody E48.

We recently produced the monoclonal antibody E48 as a specific reagent for squamous cell carcinomas. In our ongoing investigations to use E48 for clinical tumor detection and therapy, fundamental aspects of the antigen have to be elucidated and practical applications of the antibody have to be tested in a preclinical model. Immunoelectron-microscopic studies localized the E48 antigen along the cell surface and in between desmosomes, suggesting that the antigen serves as an adhesion molecule. To evaluate the usefulness of E48 for radioimmunodetection of neck node metastases, nodes from 20 neck dissection specimens were tested. A strong reactivity was observed. Furthermore, F(ab')2 fragments of E48 were compared with the complete IgG E48 for selective tumor detection in an animal model. It was demonstrated that E48 F(ab')2 fragments localize faster and reach higher tumor-nontumor ratios than the whole molecule.