Specific binding of plant-expressed anti-PD-L1 monoclonal antibody to multiple myeloma cell line RPMI8226

Abstract

Multiple myeloma (MM) is an incurable disease characterized by malignant plasma cells within the bone marrow, and its increasing occurrence has highlighted the need for innovative strategies to address relapse and treatment resistance. Given the substantial expression of programmed death ligand 1 (PD-L1) in the human multiple myeloma cell line RPMI8226, we propose PD-L1 as a promising target for multiple myeloma therapy. Here, we successfully engineered an anti-PD-L1 monoclonal antibody (mAb) within a plant-based system. Building upon our previous findings, we germinated seeds derived from transgenic plants under in vitro conditions. Afterward, we screened the resulting seedlings for expression of the anti-PD-L1 mAb using polymerase chain reaction (PCR) and western blot analyses. Anti-PD-L1 mAbs were successfully purified from plant leaves and characterized through SDS-PAGE analysis. Our findings, which were confirmed via indirect enzyme-linked immunosorbent assay (ELISA), validate the binding affinity of the anti-PD-L1 mAb to recombinant PD-L1 protein. Furthermore, we investigated the interaction between the plant-derived anti-PD-L1 mAb and Fc gamma receptor I (Fc gamma RI) as well as Fc gamma receptor IIIa (Fc gamma RIIIa) molecules, confirming robust affinity. Additionally, the antibody's binding affinity to the human multiple myeloma cancer cell line RPMI8226 was confirmed via cell ELISA. Our findings demonstrated that, unlike existing therapeutics, the plant-derived anti-PD-L1 antibody not only effectively binds to human recombinant PD-L1 protein but also to Fc gamma RI and Fc gamma RIIIa. These findings suggest the potential of plant-derived anti-PD-L1 mAb for the development of innovative therapies against multiple myeloma, emphasizing the need for further research and preclinical evaluation.