Fig. 4

Osteosarcoma-induced PMN formation promotes and accelerates the formation of lung metastasis. A Schematic diagram of the experimental model of lung metastasis. Mice were treated with 143B cells-derived secretome (SCR) for 1 week, followed by i.v. administration of 143B Luc⁺ cells into the tail vein (SCR + i.v. group). B Schematic diagram of the experimental model of lung metastasis. Mice received only the i.v. injection of 143B Luc + cells without pre-treatment with the SCR (i.v. group). C Representative bioluminescence images of lung metastasis formation in pre-treated (SCR + i.v. group) and untreated (i.v. group) mice with secretome before the i.v. injection of 143B cells. D Exponential fitting of the bioluminescence signals (photons/second) of metastatic lesions over time in the i.v. group (∇ n = 6) and the SCR + i.v. group (• n = 13 mice), and corresponding kinetic parameters. E Schematic diagram of the spontaneous metastatic mouse model. Animals were injected subcutaneously with the 143B cells. After reaching a volume of 60–100 mm³, the tumour was excised, and the animals were monitored by BLI for lung metastasis formation. F Images of the surgical resection of a primary tumour with a volume of 60 mm³ and bioluminescence images before and after the excision of the tumour. G Representative bioluminescence images at 4, 7 and 14 days after surgical resection of the primary tumour. H Histological H&E images at x100 magnification (Scale bar: 30 μm) and immunostaining for vimentin at x100 magnification (Scale bar: 30 μm) of the resected tumour. I Histological H&E images at x40 magnification (Scale bar: 20 μm) and IHC staining for reticulin (arrowed), fibronectin, α-SMA, and vimentin at x100 magnification (Scale bar: 30 μm) of lung metastatic lesions in both experimental and spontaneous mouse models. Data are presented as mean ± SEM