Construction of scFv derived from a tumor-associated monoclonal antibody having tumoricidal activity on human hepatocellular carcinoma

A mouse monoclonal antibody (Mab-HepTAA43), classified as an anti-tumor-associated antigen, was raised by immunizing BALB/c mice with the Thai human hepatocellular carcinoma S102 (HCC-S102) cell line cells using hybridoma techniques. The Mab-HepTAA43 reacted with and markedly inhibited the growth of human hepatocellular carcinoma cell lines as well as a tumor mass in an animal model. Human hepatoma transplanted into nude mice did not show metastasis after 20 injections amounting to a total of about 4 mg of the Mab over 1-month period. A single-chain variable fragment (scFv) molecule derived from the Mab was constructed by phage display method. DNA sequence analysis of the active variable regions of both heavy- and light-chains of the cDNA clone was subsequently performed. The scFv43 molecule contains a VL kappa type and a unique VH sequence having 88% amino acid homology to that of Mab-MAK B raised against tumor-associated antigen. Immunohistochemical staining on frozen sections of paired hepatoma (NCI-I) and normal liver tissue from the same individual showed that both scFv43 and Mab-HepTAA43 antibodies reacted with hepatoma but not with normal liver tissue. The results suggest that scFv43 may be useful in the immunotherapy of hepatocellular carcinoma.