Construction of phosphorylatable monoclonal antibody to a tumor-associated antigen.

A phosphorylation site was introduced into chimeric monoclonal antibody B72.3 (MAb-chB72.3) by site-specific mutation of the coding sequence. The phosphorylation site for the cAMP-dependent protein kinase was positioned at the carboxyl terminus of the heavy-chain constant region of MAb-chB72.3. The resultant modified MAb-chB72.3-P was expressed in 293 cells and purified. The MAb-chB72.3-P protein was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase with [gamma-32P]ATP to high radiospecific activity. The 32P-labeled MAb-chB72.3-P protein bound to cells expressing the tumor-associated glycoprotein 72 antigen. The introduction of phosphorylation sites into MAbs provides a new type of MAb for the diagnosis and treatment of cancers.