This makes the understanding of their individual contribution to myeloid cells in tumor host function difficult.19 Additionally, CCR 1, 2, 3, and 5 occupy a discrete and tight (165 kb) chromosomal locus (Chr9: 123962126–124127183 bp) and are expressed by most leukocyte subsets, making the in vivo study of their signal integration or redundancy difficult using the available mouse knock-out approaches. Here, CCR1 is linked to neoplasm.