CCL2 and breast cancer: We observed a significant increase in collagen measured using picrosirius red and Masson’s trichrome staining in the SVF/CCL2 tumors of mice compared to SVF/EV tumors (p = 0.002, Figure 1F, Figure S1E), suggesting that early inflammation promotes a more fibrous mammary tumor microenvironment, similar to what is observed clinically in breast tumors of obese women [5].