CSF2 (granulocyte macrophage colony stimulating factor) stimulates survival, proliferation and differentiation of hematopoietic myeloid cells.19,20 Several in vitro studies implicated CSF2 produced by cancer cells in the autocrine regulation of growth of human melanoma, prostate, bladder, gastric colon, skin and non-small-cell lung cancer cells.21–25CSF2 and its receptor CSF2R are co-expressed in human glioma cell lines and GBMs.26–30 Secreted CSF2 stimulates glioma cell growth and invasion26 but its influence on GBM microenvironment has not been thoroughly explored. Here, CSF2 is linked to cancer.