Expression of Anti Colorectal Cancer Immunotherapeutic Monoclonal Antibody in Transgenic Plant

The mAb CO17-1A recognizes the colorectal antigen GA733-2E, which highly is expressed on the surface membrane of human colorectal carcinoma cells. We have successfully developed plant system for production of anti-colorectal cancer monoclonal antibody, mAb CO17-1A. Plant expression system for mAb production has several advantages in terms of the lack of animal pathogenic contaminants, low cost, ease of scale-up for agricultural production, and efficient post-translational glycosylation modifications compared to the conventional fermentation methods. KDEL (Lys-Asp-Glu-Leu), ER retention signal attached to C-terminus of protein might induce high protein expression and the glycoprotein carrying oligomannose glycans. In this study, the expression level of mAb CO17-1A was compared between mAbs fused with and without KDEL in plant. PCR analysis showed stable gene insertion of heavy and light chain genes of mAb CO17-1A with or without KDEL. We validated the expression of mAb CO17-1A by western blot and its subcellular localization under the confocal microscopy. Western blot showed the significantly increased expression level of mAb CO17-1A with KDEL compared to without KDEL. Cell ELISA with human colorectal carcinoma cell line confirmed that expression of the mAb with KDEL was significantly higher than that of mAb without KDEL. The glycosylation analysis revealed that mAb CO17-1A without KDEL had plant specific glycans structure while mAb CO17-1A with KDEL had mainly oligomannose type glycans. Taken together, these studies suggest that KDEL affects expression of mAb and its glycan structures.