Selective cytotoxicity against human tumor cells by an anti-gastric cancer monoclonal antibody-mitomycin C conjugate.

An anti-gastric cancer monoclonal antibody, MGb2, was chosen to prepare MGb2-mitomycin C (MMC) conjugate. Four to five molecules of MMC were introduced into each molecule of antibody with the antibody activity well retained. The conjugate showed a highly selective cytotoxicity upon human gastric cancer cells KATO-III. In the 48-h exposure test, the cytotoxic effect of MGb2-MMC upon target cells was similar to that of free MMC, but much greater than that of normal mouse immunoglobulin-MMC conjugate. Instead, the MGb2-MMC showed a statistically less cytotoxic effect upon non-target cells. Imaging and biodistribution studies indicated that the MGb2 was still well localized in tumor tissue after its conjugation with MMC.