CXCL1 and breast cancer: To evaluate the clinical relevance of CXCL1, we determined its plasma levels in healthy controls (n = 22) and breast cancer patients (n = 122) using ELISA (Supplementary Fig. 1) We found that CXCL1 levels were similar between healthy individuals and patients (Supplementary Fig. 1A), and showed no correlation with age or tumor size (Supplementary Fig. 1B and C).