cDNA sequence analysis of monoclonal antibody FU-MK-1 specific for a transmembrane carcinoma-associated antigen, and construction of a mouse human chimeric antibody

Mouse monoclonal antibody (MAb) FU-MK-1, raised against a human gastric ade nocarcinoma, recognizes a transmembrane antigen, GA733-2, present on most a denocarcinomas and seems to be of potential utility for immunodiagnosis and immunotherapy of those cancers, However, an inherent problem in their in v ivo application is the human anti-mouse antibody response. In this study, w e cloned and sequenced the variable region genes of the heavy and light cha ins (V-H and V-kappa) of FU-MK-1 using the reverse transcription-polymerase chain reaction method. Then, we constructed a mouse/human chimeric antibod y, designated as Ch FU-MK-1, by fusing the FU-MK-1 V-H and V-kappa genes to the human C-gamma 1 and C-kappa genes, respectively, and by ligating the c himeric H and L chain genes to each other in a mammalian cell expression ve ctor. The final gene construct was transfected into mouse non-Ig-producing hybridoma cells by electroporation. The Ch FU-MK-1 antibody thus prepared b ound to human adenocarcinoma cells and competitively inhibited the binding of the parental FU-MK-1 to the adenocarcinoma cells. Ch FU-MK-1 also showed a potent antibody-dependent cell-mediated cytotoxicity (ADCC) with human p eripheral blood mononuclear cells as effecters against the adenocarcinoma c ells, indicating that this chimeric antibody seems to be suitable for in vi vo therapeutic approaches.