ABSTRACT
Remarkable heterogeneity in the expression of different antigens has been observed within and between different carcinomas that arise from breast and ovarian epithelium. Heterogeneity has also been observed within breast cancers using individual monoclonal reagents. Using a combination of five murine monoclonal antibodies, however, more than 95% of tumor cells could be stained intensely in more than 90% of tumors. Consequently, it is possible that more than one murine monoclonal antibody may need to be utilized if serotherapy is to be effective. Ricin A chain has been conjugated with different murine monoclonal antibodies to examine the utility of different antigens as targets for the cytotoxicity of immunotoxins. Immunotoxins are being prepared with each of the murine monoclonal antibodies that react with the extracellular domain of p185. For immunoconjugates that contain ricin A chain to be active, the immunotoxin must be taken up by endosomes and the ricin A chain translocated to the cytoplasmic compartment.
