Rat mammary adenocarcinoma CXCL12 cells show increased invasion to epidermal growth factor and recruitment of macrophages. (A) The in vivo invasion assay was performed with MTLn3 empty vector and CXCL12-overexpressing cell line tumors, allowing tumor cells to invade over 4 hours into microneedles containing 25 nM EGF or buffer. Data shown are means and SEM. *P < 0.05 and ***P < 0.0005 by t-test. (B) F4/80 staining was quantified by using a 40× lens objective and counting the number of F4/80-stained macrophages per field (n = 5 tumors per cell line and 10 random fields per tumor). Data shown are means and SEM. **P < 0.005 by t-test. (C) Representative images of F4/80 staining for macrophages in MTLn3 pQCXIP and MTLn3 pQCXIP-CXCL12 tumors. Images were taken using a 40× lens objective. Scale bar = 25 μm.