Humanization Of Mab SM5-1 And The Anti-tumor Effects In Vitro And Vivo

p230 is highly expressed on the surface of tumor cells, and is rarely expressed on the normal tissues, so it is a ideal target for tumor immunotherapy. SM5-1 is a marine monoclonal antibody that specifically binds to p230 with high affinity, and it has potent therapy effect for tumors. To reduce the immunogenicity of murine monoclonal antibody in human, we planned to humanize SM5-1.The variable region cDNAs of the SM5-l's light chain and heavy chain were cloned from the hybridoma cells by 5 'RACE. And it was confirmed to be a new gene by genebank search. By connected the variable region cDNAs with human Ig constant domain, we constructed a chimeric antibody of SM5-1. Then, we produced a humanized antibody by overlapping PCR to graft the three CDRs of SM5-1 into human antibody frameworks of light chain and heavy chain. By mutation of amino acid residues of the frameworks region, we have obtained a humanized antibody with high affinity and specificity. The humanized antibody has the backmutation residue 23, 24. 27. 28, 30, 48. 49. 71. 76 . 88 on the heavy chain and residue 1. 3, 71 on the light chain. In vitro, the chimeric and the humanized antibody remain the high affinity and specificity to p230. Both antibodies were able to inhibit the proliferation of tumor cells highly expressed p230 on the cell surface. They may induce tumor cells apoptosis by the caspase signalings. The killing activity of tumor cells may be associated with ADCC and CDC too. In vivo, the chimeric antibody strikingly inhibit tumor growth.Based on this study, we have successfully developed humanized SM5-1. We constructed and expressed chimeric and the humanized SM5-1 with high affinity. specificity and bioactivity. The development of chimeric and humanized SM5-1 monoclonal antibody may provide a- novel useful immunological regiment for treatment of cancer.