Fig. 2: Subcutaneous scaffold implants and lungs in BALB/c mice with 4T1 metastatic breast cancer employ S100A8/A9 cytokines to recruit tumor cells with lung metastasis gene signature from the circulation.

a Neutralizing S100A8/A9 in the conditioned media with antibodies decreased in vitro extravasation of 4T1 tumor cells to the conditioned media. Ab antibody, D-sca diseased scaffold. b, c Administration of anti-Gr1 antibodies to BALB/c mice bearing 4T1 tumor depleted the Gr1⁺CD11b⁺ myeloid cells (b), decreased the abundance of S100A8/A9 cytokines (b), and decreased the in vivo extravasation of intracardially injected 4T1-Luc2-tdTomato cells to diseased scaffolds and lungs (c). Antibodies were administrated at the intermediate cancer stage (marked red in the timeline). The abundance of 4T1-Luc2-tdTomato tumor cells in the tissues was measured by flow cytometry and IVIS the second day after fluorescent 4T1 tumor cells were administrated to BALB/c mice bearing non-fluorescent 4T1 tumor through intracardiac injection. d Expression of signature genes mediating breast cancer metastasis to lungs²⁸ or bones³⁰ in tumor cells transmigrating towards different cancer cell chemoattractants and conditioned media in vitro, and those colonizing diseased scaffolds and lungs in vivo. Gene signature names are to the left. Red text is overexpressed in the signature while blue text is under-expressed in the signature. 231BR MDA-MB-231BR, BM bone marrow. e Schematic illustration of how scaffolds and lungs recruit the same subpopulation of tumor cells from the circulation in mouse models with 4T1 metastatic breast cancer. Data are shown as Mean ± SEM and p values are from student’s two-tailed t test. n = 3 for (a), (b), and n = 6 for (c). Source data are provided as a Source Data file.