Effect of trastuzumab interchain disulfide bond cleavage on Fc? receptor binding and antibody-dependent tumour cell phagocytosis.

ABSTRACT: The Fc domain of human IgG1 binds to Fc? receptors (Fc?Rs) to induce effector functions such as phagocytosis. There are four interchain disulfide bonds between the H and L chains. In this study, the disulfide bonds within the IgG1 trastuzumab (TRA), which is specific for HER2, were cleaved by mild S-sulfonation or by mild reduction followed by S-alkylation with three different reagents. The cleavage did not change the binding activities of TRA to HER2-bearing SK-BR-3 cells. The binding activities of TRA to Fc?RIIA and Fc?RIIB were greatly enhanced by modification with mild reduction and S-alkylation with ICH2CONH2 or N-(4-aminophenyl) maleimide, while the binding activities of TRA to Fc?RI and Fc?RIIIA were decreased by any of the four modifications. However, the interchain disulfide bond cleavage by the different modifications did not change the antibody-dependent cell-mediated phagocytosis (ADCP) of SK-BR-3 cells by activated THP-1 cells. The order of Fc?R expression levels on the THP-1 cells was Fc?RII > Fc?RI > Fc?RIII and ADCP was inhibited by blocking antibodies against Fc?RI and Fc?RII. These results imply that the effect of the interchain disulfide bond cleavage on Fc?Rs binding and ADCP is dependent on modifications of the cysteine residues and the Fc?R isotypes.

SUBMITTER: Suzuki M 

PROVIDER: S-EPMC4882641 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature