Having determined that CCR2+/CX3CR1+ cells are bone marrow-derived, whole bone marrow was harvested and cells were cultured in the presence of KR158B glioma-derived factors (conditioned media) containing soluble GM-CSF and IL-6 to enrich and expand the population of dual-expressing chemokine receptor cells. This evidence concerns the gene CX3CR1 and central nervous system cancer.