A. CCL2 ELISA of conditioned medium from Parental (Par), control wildtype (WT) or CCL2 knockout (CCL2KO#7, CCL2KO#22) hCAF-1 cell lines. B-C. MCF10CA1d breast cancer cells were co-grafted with WT or CCL2KO fibroblasts for up to 6 weeks and measured for changes in tumor volume over time (B) or endpoint tumor mass (C). D-G. Breast tumor xenografts were immunostained for GFP (D), arginase I (E), Ly6G (F), or Von Willebrand Factor 8 (VWF8) (G). -GFP control is MCF10CA1d co-grafted with hCAF-1 parental fibroblasts.. Expression was quantified by Image J. Statistical analysis was performed using One Way ANOVA with Bonferroni post-hoc comparison. Statistical significance was determined by p<0.05. *p<0.05, ***p<0.001., n.s = not significant. Mean±SEM are shown.