Figure 1. Oncogenic KRAS mutations render lung cancer cells insensitive to macrophage phagocytosis.

(A) Tumor cells were isolated from 12 KRAS^WT and 6 KRAS^MUT lung adenocarcinoma patients, labeled with the fluorescent dye CFSE, incubated with human peripheral blood monocyte–derived macrophages for 2 hours, stained with F4/80, and analyzed by flow cytometry. Phagocytosis rate was calculated as the percentage of CFSE⁺F4/80⁺ cells among CFSE⁺ cells. Representative FACS results and quantification for all patients are shown. (B) KRAS^G12C H358 cells were transfected with plasmids expressing KRAS^WT or KRAS^G12C or with 3 KRAS siRNAs. After 48 hours, the cells were subjected to a phagocytosis assay similar to that in A. Quantitative analysis (n = 5) is shown. NSCLC, non–small cell lung cancer. (C and D) Macrophage phagocytosis of H358 cells gradually decreased with tumor progression in vivo. An animal model of lung cancer was established by tail-vein injection of EGFP-labeled H358 cells into nude mice. (C) Representative images of H&E-stained lung sections at different time points are shown. Scale bar: 2 mm. (D) Macrophage infiltration into lung tumor tissue was assessed by CD11b (red) and iNOS (purple) staining. Representative images and quantification results (n = 5) are shown. Arrows indicate GFP⁺iNOS⁺CD11b⁺ cells. Scale bar: 50 μm. Original magnification, ×40 (enlarged insets). (E and F) Macrophage phagocytosis of tumor cells gradually decreased with tumor progression in genetic models of lung cancer. Kras^LSL-G12D/+ p53^fl/fl mice were intratracheally administered adeno-Cre to trigger pulmonary adenocarcinoma formation. Tumor growth was monitored by micro-CT at different time points. (E) Representative 3D reconstructions of mouse lungs. Tumors are shown in red. (F) Macrophage infiltration was assessed by staining for CD11b (red), iNOS (purple), and KRAS^G12D (green). Representative images and quantification results (n = 5) are shown. Arrows indicate KRAS^G12D+iNOS⁺CD11b⁺ cells. Scale bar: 50 μm. Original magnification, ×40 (enlarged insets). Data are shown as the mean ± SEM. **P < 0.01 and ****P < 0.0001, by unpaired t test (A) or 1-way ANOVA (B, D, and F).