Another example of neutrophil–tumor cell crosstalk is the finding that GM-CSF secreted by human breast cancer cells increases CD11b/CD18 (Mac-1) expression on neutrophils, which interacts with ICAM-1 expressed on the tumor cells, resulting in subsequent neutrophil-mediated transendothelial migration of the tumor cells [257,258]. This evidence concerns the gene CSF2 and breast cancer.