Fig. 2

GPNMB is upregulated in the murine TME and is predominantly expressed by TAMs. A Representative FACS analysis of GPNMB⁺ populations in MG/TAMs (I), MonoLy6c^low (II), MonoLy6c^high (III), neutrophils (IV) and lymphocytes (V) in naïve brain and spleen tissue (top row) and tumor-bearing brain tissue (bottom row). B Quantification of GPNMB expression in non-immune cells (CD45⁻CD11b⁻). Comparison of naïve brain (n = 4) against tumor-bearing (n = 5) brain tissue. GPNMB expression in microglia (MG)/macrophages (MPH)/TAMs (I; CD45⁺CD11b⁺Ly6G⁻Ly6c⁻). Comparison between naïve brain (n = 4), naïve spleen (n = 4) and tumor brain (n = 5). GPNMB expression in monocytes with low Ly6c (II; CD45⁺CD11b⁺Ly6G⁻Ly6c^low), monocytes with high Ly6c (III; CD45⁺CD11b⁺Ly6G⁻Ly6c^high), neutrophils (IV; CD45⁺CD11b⁺Ly6G⁺Ly6c⁺) and lymphocytes (V; CD45⁺CD11b⁻). Comparison of naïve spleen (n = 4) against tumor-bearing (n = 5) brain tissue. Error bars represent SD. Statistical analysis in 3 groups was performed using Ordinary one-way ANOVA with Tukey’s multiple comparisons test and in 2 groups using unpaired t-test. *p < 0.05, **p  < 0.01, ***p < 0.001, ns, not significant. C Representative brain slices from tumor-bearing WT mice stained for IBA1 (top row), GPNMB (middle row) and merge with DAPI (bottom row; IBA1 = green, GPNMB = red, DAPI = blue). Left column: Lower magnifications of the invasive edge (white dotted line = invasive edge; left: brain tissue; right: tumor tissue). Scale bar represents 200 µm. Middle column: Higher magnifications of the invasive edge. Scale bar represents 50 µm. Right column: Representative GPNMB⁺/IBA1⁺ cells in the tumor core. Scale bar represents 20 µm