CCL2 and neoplasm: To determine whether IM-derived Ccl2 specifically drives tumor progression, we first created bone marrow (BM) chimeras by lethally irradiating CD45.1 wild-type hosts and reconstituting them with either CD45.2 WT or Ccl2−/− BM, thereby preserving non-hematopoietic CCL2 (e.g., from endothelial cells)36.