Anti-hepatoma human single-chain Fv antibody and adriamycin conjugates with potent antitumor activity

To construct an improved biological missile, an immunoconjugate ADM–Dex–ScFv-SA3 was synthesized, which was composed of a hepatocellular carcinoma-specific, single-chain Fv antibody (ScFv-SA3) and a highly potent cytotoxic drug, adriamycin (ADM), as the warhead. Oxidized Dextran T10 (Dex-T10) was used as a linker to connect these two moieties. The 40 KD soluble anti-hepatoma human Trx-ScFv-SA3 protein was expressed in E. coli BL21 (DE3), using a prokaryotic expression vector, pET21a (+)-Trx-ScFv-SA3-His. It was purified using a His-Tag Ni-Agarose column and identified by western blot. The activity of Trx-ScFv-SA3 was verified by enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry to confirm that it specifically binds to the hepatocellular carcinoma cell line HepG2. To prepare ADM–Dex–ScFv-SA3, ADM was conjugated to the antibody at a molar ratio of 14.21:1. The antitumor effect of the conjugate was tested by MTT assay, plate colony formation assay and xenografts in a nude mice experimental model. In vitro experiments revealed that ADM–Dex–ScFv-SA3 could bind to tumor cells selectively and inhibit the proliferation and the colony formation ability of HepG2 cells. In vivo experiments showed that ADM–Dex–ScFv-SA3 suppressed the tumor growth and prolonged the median survival time in tumor-bearing mice. Tumor histology slides indicated a significantly slower tumor tissue proliferation in the ADM–Dex–ScFv-SA3 group. These data indicate that the targeted drug, ADM–Dex–ScFv-SA3, may be a highly potent and selective therapy for the treatment of hepatoma.