The recruitment of neutrophils in TME is mainly regulated by chemokine receptor CXCR2 and it has been reported that TNFa-activated mesenchymal stem cells (MSCs) releasing CXCL1, CXCL2 and CXCL5 efficiently recruited CXCR2 positive neutrophils into the tumor, promoting BC metastasis [121]. This evidence concerns the gene CXCR2 and breast cancer.