Macrophage Colony-Stimulating Factor (MCSF, also known as colony-stimulating factor 1 or CSF1) and Transforming Growth Factor-β (TGF-β) have both been reported to be expressed by GBMs in the past and both have been associated with MDSC accumulation in cancer.[2, 16, 35–37] However, neither was present above background in our glioma-conditioned media. Here, CSF1 is linked to central nervous system cancer.