Immunofluorescence co-staining confirmed that a low number of CXCR4+ MDSCs were present in U251-BATF2 tumours (Fig. S7C), and very few CXCR7+ MDSCs were observed in both U251-Ctrl and U251-BATF2 tumours (Fig. S7D). Here, ACKR3 is linked to neoplasm.