Fig. 7: CSF1R inhibitor abrogates M2-TAMs-mediated CRC metastasis in vivo.

A A schematic diagram of the in vivo mouse peritoneal metastasis experiment. BALB/c-nu nude mice were intraperitoneally injected with 5 × 10⁵ MC38sh (n = 4) or CT26-OPN cells (n = 5). Peritoneal metastasis was assessed via IVIS 4 days after injection. Mice were grouped based on bioluminescence values and orally treated with 30 mg/kg PLX3397 or control solvent for 5 days. Post-treatment, metastasis was re-evaluated via IVIS, and tumors were collected for analysis (e.g., D–F). B Bioluminescence imaging of peritoneal metastatic tumors pre- and post-PLX3397 treatment. C Quantitative analysis of bioluminescence imaging post-treatment. D Representative staining of tumor sections: H&E (top), Ki-67 (middle), and TUNEL (bottom). Scale bar: 100 μm. E mIHC analysis of M2-TAMs (F4/80⁺CD206⁺) in tumors. F Proportion of M2-TAMs (F4/80⁺CD206⁺) in each group. G Mechanistic insights are summarized: Tumor-derived OPN activates PI3K/AKT signaling in macrophages, inducing CSF1 secretion and polarization of macrophages to the M2 phenotype dependent on CSF1R. This crosstalk facilitates reciprocal migration between CRC cells and TAMs, promoting metastatic progression. PLX3397 disrupts this loop by blocking CSF1R, thereby reducing M2 polarization and CRC tumor metastasis. IVIS, in vivo imaging system. All data are shown as mean ± SD; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001; ns, not significant.