CSF1 and central nervous system cancer: Having determined that glioma-derived M-CSF and IL-34 drive M-MDSC differentiation (Figure 4) and GM-CSF and IL-6 are present in the glioma microenvironment (Figure 2A), whole bone marrow was harvested, and cells were cultured in the presence of glioma-conditioned media and exogenous GM-CSF and IL-6.