CCR5 and breast carcinoma: Finally, to functionally evaluate the role of CCR1 and CCR5 on human MDSC differentiation, we stimulated UCB-HSPCs with TCMs from human breast cancer cell lines (MDA231, 1833, or 4175) or recombinant cytokines (GM-CSF +G CSF or GM-CSF +IL6) for 4 days with B×471 and maraviroc (figure 7C) or with vehicle as control.