Epitope-dependent differential immunoreactivities of anti-MUC1 monoclonal antibodies in human carcinomas

According to studies on a variety of malignant tumors from different organs MUC1 mucin antigen presents as a valuable marker of cancer progression and prognosis. During recent years, a great number of monoclonal antibodies (m abs) directed to MUC1 was generated. Their epitopes can be classified accor ding to their position within the tandem repeat domain of the mucin and wit h respect to effects exerted by site-specific glycosylation. In this study, eight mabs from different clusters were selected to correlate their epitop e specificity with their binding pattern in human cancer specimens. By appl ying an immunohistochemical ABC-peroxidase method, ten carcinomas derived f rom breast, pancreas, stomach and colon were characterized. A positive reac tion of all mabs could be observed in the majority of the carcinomas, howev er, the extent of the stained tumor area varied significantly. In general, mabs M38, VA1 and BC3 exhibited the strongest staining reaction. Mab BW835 showed a similar binding intensity, especially in pancreatic and gastric ca rcinomas. It is tempting to speculate that the different binding patterns m ay reflect differences in epitope specificity. In conclusion, future immuno histochemical, immunoserological and therapeutic studies involving MUC1 ant igen should prefer well-characterized and highly reactive mabs detecting de fined peptide epitopes.