Human monoclonal antibody reactive to stomach cancer produced by mouse-human hybridoma technique

Production of human monoclonal antibodies reactive to stomach cancer was attempted by the hybridoma technique using splenic lymphocytes from stomach cancer patients. The parental cells used were NS-1 mouse myeloma line and three human lines including RPMI-1788 6TGR, which was established in our laboratories. Ten mouse-human and two human-human (from the fusion with RPMI-1788 6TGR) hybridomas have been producing IgM antibody for over 18 months, and all the heterohybridomas yielded ascites when transplanted into nude mice. Four antibodies produced by the heterohybridomas were selected and analyzed. These 4 antibodies, 3F6, 4A10, 3H5 and 1F9, reacted predominantly to cytoplasmic antigens of stomach and other epithelial cancer lines. The reactivity against human tumors transplantable in nude mice showed that all antibodies but 3F6 were reactive with stomach and lung cancers. Smears prepared from normal and cancer tissues were also tested, and these 4 antibodies showed positive reactions not only to stomach cancer, but also to normal stomach and colon. The reactivity against fetal tissues demonstrated that 3H5 antibody was reactive with epithelium of the stomach, and 1F9 antibody was positive with epithelium of the respiratory tract and bile duct, but the other two were negative. Thus, the serological analysis showed that the antigens detected are not tumor-specific, but are differentiation antigens. Chromosome analysis of these 4 mouse-human hybridomas and another one, which seems to produce an antibody against keratin, showed that three retained human chromosome 14 on which immunoglobulin heavy chain (Ig H) gene is located, but two did not. Southern blot analysis, however, revealed that all 5 hybridomas had a human Ig H gene.