CX3CR1 and central nervous system cancer: Since in vivo glioma-associated myeloid cell subtypes do not directly correspond to in vitro-defined M0, M1, or M2-like macrophages, we defined microglia based on the expression levels of CX3CR1, TMEM119, ADORA3, BHLHE41, and BIN1 [25, 26], mast cells based on MS4A2, CPA3, KIT, and TPSAB1 [27], and other tumor-associated monocytes/macrophages based on HLA-DRB5, S100A11, and MS4A6A [25].