Fig. 1.

Chronic pulmonary P. aeruginosa infection promotes breast cancer lung metastasis. a Upper panel: Schematic diagram of spontaneous metastasis. Mouse mammary carcinoma 4T1 cells (2 × 10⁵) were orthotopically implanted into mouse MFPs followed by tracheal injection of PBS or PAO1-Beads on day 7 after tumor bearing. Lower panel: Kaplan–Meier analysis of lung metastasis survival in PBS (n = 17) or PAO1-bead-treated (n = 14) mice [log-rank (Mantel–Cox test). PAO1-Beads agar bead-embedded PAO1, MFP mammary fat pad. b A mouse model was constructed as described above, and the mice were sacrificed at the endpoint. Weight of lungs excised from mice in different treatment groups at day 21 (n = 12–13 mice/group). c, d Lung images (c) and numbers of lung metastasis nodules (d) from CTRL (control) group and CI (chronic infection) group mice (n = 14–15 mice/group). e, f Representative images of ex vivo metastatic lungs (e) and ex vivo quantification of lung metastasis (f) from 4T1-luci-bearing mice with or without chronic pulmonary PAO1 infection (n = 5 mice/group). g, h Representative H&E pictures (g) and corresponding quantification (h) of lung tissues are shown to determine the tumor burden (n = 6 mice/group). Scale bar, 25 μm I, j Bright-field imaging (i) and number of metastatic nodules (j) in the lungs of MMTV-PyMT mice from the CTRL group (n = 7) and CI group at the endpoint (14 weeks of age) (n = 11). Scale bar, 50 μm. All data are presented as the mean ± SEM. Statistical significance was calculated using an unpaired t test. ****P < 0.0001; ***P < 0.001; **P < 0.01; *P < 0.05