We then assessed the levels of macrophages in mammary tumors from MMTV-PyMT Ccr6WT and Ccr6−/− mice, and found that the proportion and overall numbers of TAMs were significantly reduced in MMTV-PyMT Ccr6−/− mammary tumors relative to Ccr6WT (Fig. 5b). Here, CCR6 is linked to breast cancer.