Murine monoclonal antibodies to colon-specific antigen p

A previous report described the production of monoclonal antibodies Mu-1, -2, -3, and -4 against colon-specific antigen p. We now report the tissue distribution of the reactive epitopes. Each of the monoclonal antibodies was reactive with epitopes shared by the entire length of the intestine, with Mu-2 and Mu-3 determinants being present in the stomach as well. Mu-1 and Mu-4 appeared to have a more restricted distribution than did Mu-2 and Mu-3, which were present in several nongastrointestinal tissues. Unfortunately, these MAbs were not ideal for in vivo use against colorectal carcinoma. Mu-1 was not present in neoplastic colon tissue, Mu-2 and Mu-4 were reactive with granulocytes, and Mu-3 was reactive with kidney tubules and connective tissue. An additional fusion was performed from which Mu-9 was selected for further study. Among normal adult tissues this monoclonal antibody gave reactivity restricted to the intestines. The stomach and all nonintestinal tissues were negative by immunoperoxidase. Among colon tumors 60% were positive for the Mu-9 epitope. The data suggest Mu-9 may be a good candidate for in vivo targeting of diagnostic and therapeutic agents to colon cancer.