Effects of gelonin immunoconjugate of monoclonal antibody MSN-1 to endometrial adenocarcinoma on antigen-producing tumor cells in vitro.

Missile therapy, which destroys cancer cells specifically, has been considered to be an effective modality for treatment of carcinoma. We have developed a monoclonal antibody MSN-1 (immunoglobulin class: IgM), of which the immunogen is the endometrial adenocarcinoma cell line SNG-II, which strongly reacts with endometrial adenocarcinomas. We describe an immunoconjugate consisting of the MSN-1 and a plant hemitoxin named gelonin which has revealed to assume selective cytotoxicity against the SNG-II in a colony formation assay in vitro. The results of our study suggest that the 'inhibitory concentration' or IC50, of the MSN-1-gelonin immunoconjugate against the SNG-II was 188 fold that of gelonin alone. These results indicated that the MSN-1-gelonin immunoconjugate exhibited highly selective cytotoxicity to endometrial adenocarcinoma, which expressed an epitope against the MSN-1, and it is suggested that the MSN-1-gelonin immunoconjugate has possibility of clinical application to treatment of endometrial adenocarcinomas.