[Comparison of the characteristics of NK cells after two different methods of expansion and observation of the clinical efficacy in patients who relapsed post allogeneic hematopoietic stem cell transplantation]

Objective: To explore the differences in the biological effects of different expansion systems on natural killer (NK) cells, as well as the safety and preliminary clinical efficacy in the treatment of patients with recurrence after allogeneic hematopoietic stem cell transplantation (allo-HSCT) . Methods: Peripheral blood cells from healthy donors were stimulated with either CD3 combined with CD52 or K562 feeder cells loaded with IL-21/4-1BB to induce NK cell expansion. Changes in the NK cell phenotype, cytokine secretion, and cytotoxicity before and after expansion were detected. We also evaluated the safety and clinical efficacy of two different expansion strategies for patients received NK infusion. Results: Compared with the CD3/CD52 monoclonal antibody amplification system, the feeder cell expansion group had a higher purity of NK cells and higher expression ratios of NK cell surface activation receptors such as DNAM-1 and NKp30, while inhibitory receptor CTLA-4 expression was low and NKG2D/CD25/CD69/ Trail/PD-1/TIM-3/TIGIT had no statistically significant differences between the groups. Further functional results showed that the expression level of KI67 in NK cells after expansion in the two groups increased significantly, especially in the feeder cell expansion group. Simultaneously, the perforin and granzyme B levels of NK cells in the feeder cell expansion group were significantly higher than in the CD3/CD52 expansion group. A retrospective analysis of eight patients who received monoclonal antibody-expanded NK cell reinfusion and nine patients with trophoblast cell-expanded NK cell reinfusion was done. The disease characteristics of the two groups were comparable, NK cell reinfusion was safe, and there were no obvious adverse reactions. Clinical prognostic results showed that in the CD3/CD52 monoclonal antibody amplification group, the MRD conversion rate was 50% (2/4) , and the feeder cell expansion group was 50% (3/6) . After 5 years of follow-up from allo-HSCT, three patients in the monoclonal antibody expansion group had long-term survival without leukemia, and the remaining five patients had died; two patients died in the feeder cell expansion group, and the other six patients had long-term survival. Six cases had GVHD before NK cell reinfusion, and GVHD did not aggravate or even relieved after NK cell reinfusion. Conclusions: Preliminary results show that the biological characteristics of NK cells with diverse expansion strategies are significantly different, which may affect the clinical prognosis of patients with recurrence or persistent minimal residual disease after HSCT. The two groups of patients treated with NK cells from different expansion strategies had no obvious adverse reactions after NK cell infusion, but efficacy still needs to be further confirmed.