CSF1 and central nervous system cancer: Glioma cell lines U271 (2.5 × 105) was subcutaneously injected with the same cell number of THP-1 (2.5 × 105) treated with M-CSF alone or in combination with equal number of M2 macrophages induced (2.5 × 105 U271 mingled with 5.5 × 105 M2 macrophages).