Activation Of Natural Killer Cells By Soypeptide Lunasin and Cytokine: Implication In Cancer Immunotherapy For Lymphoma

Immunostimulatory cytokines can enhance anti-tumor immunity and are part of the therapeutic armamentarium for cancer treatment. We have previously reported that chemotherapy-treated lymphoma patients have acquired deficiency of Signal Transducer and Activator of Transcription 4 (STAT4), which results in defective IFNg production during clinical immunotherapy. With the goal of further improvement in cytokine-based immunotherapy, we examined the effects of a soybean peptide called lunasin that exhibits immunostimulatory effects on natural killer (NK) cells.

PBMCs of healthy donors and chemotherapy-treated lymphoma patients were stimulated with or without lunasin in the presence of IL-12 or IL-2. NK activation was evaluated, and its tumoricidal activity was assessed using in vitro and in vivo tumor models. Chromatin immunoprecipitation (ChIP) assay was performed to evaluate the histone modification of gene loci that are regulated by lunasin and cytokine.

Adding lunasin to IL-12- or IL-2-cultuted NK cells demonstrated synergistic effects in the induction of IFNG and genes involved in cytotoxicity. The expression level of CD16 and granzyme B was increased in CD56-bright population of NK cells following stimulation with lunasin and cytokine. The combination of lunasin and cytokines (IL-12 plus IL-2) was capable of restoring IFNg production by NK cells from post-transplant lymphoma patients. In addition, NK cells stimulated with lunasin plus cytokines had higher tumoricidal activity than those stimulated with cytokines alone using in vitro and in vivo tumor models. Moreover, lunasin augmented antibody-dependent cellular cytotoxicity (ADCC) of NK cells against anti-CD20 coated human B-lymphoma cell line. The underlying mechanism responsible for the effects of lunasin on NK cells is likely due to epigenetic modulation on target gene loci.

We have discovered a novel use of lunasin that exerts synergistic effects together with IL-12 or IL-2. This synergism leads to stronger NK-mediated anti-tumor activity, suggesting the potential clinical use of lunasin to augment the therapeutic responses in cytokine-based immunotherapy.

No relevant conflicts of interest to declare.