Treatment of a human AML mouse model with off-the-shelf cord blood FLT3 CAR_sIL-15 NK cells. (A) The scheme for treating NSG mice, which received engraftment with the FLT3⁺ MOLM-13 AML cells, with off-the-shelf sIL-15 NK cells or FLT3 CAR_sIL-15 NK cells. MOLM-13 AML cells expressing luciferase (1 × 10⁴ MOLM-13_luc_GFP cells) were injected into 12-week-old NSG mice on day 1, followed by an infusion of a corresponding treatment (1 × 10⁷ NK cells per dose) on day 5 and day 12, via tail vein injection. (B) Survival analysis was estimated using the Kaplan-Meier method of the mice treated with vehicle (freezing buffer), sIL-15 NK cells, or FLT3 CAR_sIL-15 NK cells; n = 5 mice per group; P value was calculated using log-rank test. (C-D) Fluorescence-activated cell sorting analysis of the cells collected from the BM (C) or the PB (D) of the mice treated with vehicle (freezing buffer), sIL-15 NK cells, or FLT3 CAR_sIL-15 NK cells. The populations of tumor cells and NK cells were gated on GFP and EGFR, respectively; n = 4 mice per group. (E) Tumor-engrafted mice were treated with FLT3 CAR_s15 NK cells (1 × 10⁷ cells per mouse) or vehicle on days 21 and 28. The survival was estimated using the Kaplan-Meier method (n = 9 per group). P value was calculated using log-rank test. The figure was generated with BioRender.com.