Fig. 4: Cancer-educated BMSCs attract cancer cells through CXCL5/CXCR2.

GFP-BMSCs were co-cultured with LLC for 3 days and then were intravenously injected into C57BL/6 mice. 3 days later, RFP-LLC cells were subcutaneously injected. a The ratio of GFP-positive BMSCs in lung and bone marrow measured by flow cytometry. b The ratio of RFP-positive LLC cells in lung and bone marrow measured by flow cytometry. c Chemokines produced by BMSCs cells. Human BMSCs were co-cultured with A549 lung cancer cells. Three days after co-culture, the media was changed and BMSCs were cultured for additional 3 days. The conditioned media was then collected for Human chemokine proteome profiler antibody array analysis. d Expression of CXCL5 and CCL5 quantified by RNA-Seq. FPKM for selected gene transcripts obtained by RNA-Seq. Data were presented as the mean ± SD and analyzed with Student’s t-test. *p < 0.05; **p < 0.01; ***p < 0.001. e Chemotaxis assay was performed by transwell. A549 were co-cultured with human BMSCs and were seeded into transwell insert. Anti-CXCL5 neutralizing antibody or CXCR2 antagonist were added to the underneath reservoir plate. f Kaplan–Meier survival curve for overall survival of mice with co-injection of BMSCs and LLC or injection of LLC alone. The mice with co-injection received anti-CXCL5 neutralizing antibody or blockage of its receptor CXCR2 on LLCs before injection. Data were analyzed with Student’s t-test, ns: no significance, *p < 0.05; **p < 0.01. g The ratio of RFP-positive LLC cells in circulation measured by flow cytometry. RFP-LLCs were injected subcutaneously with or without BMSCs. The flow cytometry assay was used to measure the RFP-positive LLCs in circulation. Mice were treated with anti-CXCL5 neutralizing antibody. LLCs were treated with CXCR2 antagonist before its inoculation in the mice. CE-BMSCs: cancer-educated BMSCs.