Refining the data to all breast cancer cell lines and using a previously published signature of Ras/MAPK activation (43) because of the low preponderance of activating KRAS mutations in breast cancer, we found strong positive associations of transcriptional activation of the Ras/MAPK pathway with MDSC-recruiting CXCR2 ligands (CXCL1/2/8) but not T cell–recruiting CXCR3 ligands (CXCL9/10/11) (Figure 6A). Here, CXCR2 is linked to breast cancer.