CXCR2 and cancer: Considerable evidence showed that CXCL2 overexpression was poor prognosis in patients with ovarian cancer, cervical cancer, etc.53,54 The upregulated CXCL2 expression in cancer cells was proposed to promote invasion and migration.55 Here, we demonstrated CXCL2 secreted by PMN-MDSCs in TME cooperated with its receptor CXCR2 which was highly expressed on BCSCs, indicating a cross-talk between PMN-MDSCs and BCSCs was achieved by CXCL2-CXCR2 axis.