Expression, function, and glycosylation of anti-colorectal cancer large single-chain antibody (LSC) in plant

In this study, transgenic tobacco plants were generated to express anti-colorectal cancer large single chain (LSC) antibody CO17-1A (LSC CO) and LSC CO tagged with the endoplasmic reticulum (ER) retention signal KDEL (LSC COK). The LSC antibodies were constructed by linking the C-terminus of variable region (VL) of the light chain (LC) to the N-terminus of the heavy chain (HC) of mAb CO17-1A with a linker peptide. Reverse-transcription PCR (RT) and immunoblot analyses showed that the LSC CO17-1AK expression level was higher than LSC CO17-1A in plant. In glycosylation analysis, oligomannose type glycan form was observed in LSC COK and plant-specific α(1,3)-fucose was observed in LSC CO. Binding activity of both LSC CO17-1A and LSC CO17-1AK to human colorectal cancer cell lines SW480 and SW620 were confirmed using indirect cell enzyme-linked immunosorbent assay (ELISA). In indirect cell ELISA, the LSC antibodies had a higher binding activity than full-size mAb CO17-1AK. In surface plasmon resonance (SPR) assay using epidermal cell adhesion molecule (EpCAM) highly expressed on the human colorectal cancer cells, both LSC antibodies showed a similar binding activity to the full-size mAb CO17-1A. These results indicated that LSC antibodies with functional binding activities to human colorectal cancer cells and EpCAM protein were successfully expressed in the transgenic tobacco plant.