Background: The anti-gyasileganglioside (GD2) antibody has been clinically shown to mediate tumor killing via conplement-derived cellular toxicity (CDC) and antibody-dependent cellular toxicity (ADCC). Although the combination of anti-GD2 antibody and cytokines has become a novel therapy to prevent recurrence in patients with advanced neuroblastoma, the therapeutic outcome has been insufficient. On the other hand, clinical studies to treat advanced malignancies using NK cells are emerging worldwide; however, overall purity and numbers of NK cells and their antitumor potencies are unsatisfactory as to obtain clinical outcome. Therefore, we established a simple method to generate purified and highly activated NK cells (Zenithal NK=Z-NK) from peripheral blood mononuclear cells (PBMCs). However, it has yet to be shown whether adoptive transfer of Z-NK cells combined with tumor-specific antibody has more therapeutic potential than Z-NK alone.
Purpose: To confirm the synergic efficacy of Z-NK cells and anti-GD2 antibody to human neuroblastoma cells.
Methods: In vitro: IMR32 cells are incubated for 1 hour at 4℃ with or without anti-GD2 antibodies (1μg/ml). Cells are co-cultured with ZNK in Effector/Target (E:T) = 1:10 for 3 hours at 37℃. Then, percent specific lysis is calculated. In vivo: Dermal tumor composed of IMR32 on NOD/SCID mouse is treated with ZNK alone, GD2 antibody alone or ZNK combined with GD2 antibody via tail vein. The growth of tumor is monitored.
Results: A dose-dependent response was apparent, 3hr of co-culture with ZNK cells was sufficient to kill nearly 100% of IMR32. The %lysis values against IMR32 (E:T=1:10) were found to be approximately 〜30% (without GD2 antibody), and 〜50% (with GD2 antibody) at 3 hr.
Conclusion:These findings indicate that the ZNK cells may be under a near optimally activated state that has never been achieved by preexisting techniques and have an excellent antitumor activity especially with tumor-specific antibody. Thus the combination therapy may contribute to the advance of adoptive immunotherapy against neuroblastoma in a clinical setting.