To address this question we have generated an adoptive transfer system in which purified BM GFP+ cells from CCR2+ mice harboring a targeted replacement of the CX3CR1gene by EGFP reporter gene (cx3cr1gfp), together with the CD45.1 congene, were transplanted into CCR2−/− mice bearing a CCR2+ tumor. This evidence concerns the gene CCR2 and neoplasm.