IL-34 induced myeloid differentiation and displayed anti-AML activity, independent of CSF1R, PTPRZ1, and SDC1. (A) Western blot analysis showing CSF1R, PTPRZ1, and SDC1 KO efficiency in C1498 cells. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was the loading control. (B) Growth curves of C1498 cells transfected with CSF1R, PTPRZ1, or SDC1 KO lentiviruses with or without IL-34 treatment (n = 3). (C) Colony-forming ability of C1498 cells after CSF1R, PTPRZ1, and SDC1 KO, with or without IL-34 treatment (n = 5). (D) Percentage of CD11b in C1498 cells after indicated KO, with or without IL-34 treatment in grafts (n = 3). (E) Flow cytometry analysis of CD11b expression in panel D. (F) Representative Giemsa staining images showing morphology of C1498 cells after CSF1R, PTPRZ1, and SDC1 KO, with or without IL-34 treatment. (G) Schematic of generation of mouse models of AML by engrafting C57BL/6J mice with GFP-labeled C1498 cells infected with indicated KO lentiviruses (5 × 10⁶ cells per mouse), followed by in vivo treatment with vehicle vs IL-34 (100 μg/kg, intraperitoneally every 2 days). (H) Kaplan-Meier survival curves of mice that underwent engraftment with C1498-KO cells and dosed with IL-34 as indicated (n = 10). Statistical analysis using the log-rank (Mantel-Cox) test. (I) Spleen weights from mice with AML dosed as described in panel G (n = 6). (J) Percentage of GFP⁺ leukemia blasts in the BM, liver, PB, and spleen from mice with AML treated with IL-34 or vehicle (n = 6). (K-L) Representative images of hematoxylin and eosin–stained liver (K) and spleen (L) sections from mice with AML treated with IL-34 or vehicle. Scale bars, 20 μm. (M) Wright-Giemsa–stained BM in mice that underwent engraftment with indicated C1498-KO cells and dosed with IL-34. Scale bars, 10 μm. (N) Flow cytometry plots depicting the percentage of CD11b⁺Gr-1⁺ cells in the BM of mice from panel M. Statistical significance was calculated using one-way ANOVA with Tukey multiple comparison test. Data are representative of at least 3 independent experiments, with cohorts of the indicated number of mice per group.