Monovalent carcinoembryonic antigen 79 antibody conjugated with recombinant human angiogenin (CEA 79/angiogenin) shows a cytotoxic effect against SNUC4 expressing CEA on its surface

Abstract

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