Figure 10. Lung-derived gMDSCs induce metastatic growth of disseminated tumour cells.

(a,b) We developed a mouse model that shows no metastatic growth when primary tumours were resected at 1 week post implantation (c) despite the existence of disseminated tumour cells in regional lymph nodes and lungs. (d,e) All mice develop metastasis when primary tumours were resected at 2 weeks post implantation. (f) Illustration of the experimental design. (g) Primary 4T1-Luci tumours were resected after 1 week post implantation and mice were followed up for metastatic growth by bioluminescence imaging (BLI). There was no metastatic growth up to week 11. (h) After resection of primary tumours, mice were injected (via tail vein) with tumour-derived mMDSCs as indicated and followed up by BLI without any metastatic growth. (i,j) Mice injected with lung-derived gMDSCs showed metastatic growth in three out of four mice. (k) Our findings suggest a spatiotemporal regulation of tumour plasticity by MDSC subsets in primary site and in distant organs as illustrated. Results are presented as mean±s.d. (five mice in each group). Scale bar, 50 μm.