MONOVALENT CARCINOEMBRYONIC-ANTIGEN-79 ANTIBODY CONJUGATED WITH RECOMBINANT HUMAN ANGIOGENIN (CEA-79 ANGIOGENIN) SHOWS A CYTOTOXIC EFFECT AGAINST SNUC4 EXPRESSING CEA ON ITS SURFACE

Carcinoembryonic antigen (CEA) is a tumor-associated antigen which is expressed largely in gastrointestinal tract tumors. Some monoclonal an tibodies to CEA have already been produced by us and the immunological characteristics of the antibodies characterizes. CEA 79 antibody show ed the highest affinity for CEA (1.93 x 10(9) M(-1)). In this study CE A 79 antibody was reduced to the monovalent form and was conjugated wi th recombinant human angiogenin using the two-step maleimide chemical cross-linking method. Then its cytotoxic effect on SNUC4, which is a h uman adenocarcinoma cell line established from gastrointestinal tract tumor by the Korean Cell Line Bank (KCLB) and which expresses CEA on i ts surface, was examined. The resulting monovalent CEA 79 antibody con jugated with recombinant human angiogenin (CEA 79/angiogenin) showed c ytotoxic effect at concentrations of 5 x 10(-9) M or higher, while bot h unconjugated human angiogenin and CEA 79 antibody did not show a cor responding cytotoxic effect, indicating that CEA 79/angiogenin can be used as an immunotoxin toward tumor cells expressing CEA on their surf ace.