Preparation, Phototoxicity And Mechanism Studies Of Anticarcinoembryonic Antigen Monoclonal Antibody-HPD Conjugates

Immunophototherapy of cancer combines the specificity of a monoclonal antibody (mAb) to an overexpressed tumor marker with the phototoxic properties of a conjugated dye. Hematoporphyrin derivative (HPD) was covalently coupled to a C50 mAb directed against carcinoembryonic antigen (CEA) via [1-ethy1-3-(3-dimethyl-aminopropyl) carbodiimide hydrochloride] (EDCI) to yield conjugates with a molar ratio ranging from 55 to 100 mol of HPD per mol of C50 mAb. The physical and chemical characters of the immunoconjugates were identified. It was proved that the conjugate remained similar immunoactivity as the free mAb. Antibody-directed cytotoxicity was demonstrated with the MTT assay using combinations of antigen-positive and antigen-negative cell lines. 1) The four conjugates with different molar ratio were compared. then got the most effective one, 66:1. 2) The cytotoxicity to SW1116 between the conjugate and HPD were compared. The conjugate showed a significant increase in killing the tumor cells.3) The cytotoxicity to Hep-2 between the conjugate and HPD were compared. The conjugate showed a significant decrease during killing the tumor cells. Then an apoptosis kit was used to study the mechanism and found that the more HPD concentration were, the more and sooner apoptosis happened in the tumor cells. It was concluded that these conjugates demonstrate clear in vitro tumor-targeting capacity and photocytotoxic properties. Such conjugates could thus be promising candidate drugs for clinical photodynamic therapy of cancers expressing CEA.