Fig. 6

Astrocytic scar limiting human brain tumor growth via glutamate–MAO-B activity. a Presence of astrocytic scar formation in human GBM brain tissue assessed by immunostaining. GFAP⁺ cells adjacent to GBM tumor (PT region) transformed to elongated shape and highly expressed CSPGs, while GFAP⁺ cells far away from GBM tumor (AT region) maintained their star shape with no significant CSPGs expression. b A clinical case showing astrocytic scar limiting human brain tumor growth assessed by MRI and ¹¹C–Acetate PET. ¹¹C–Acetate PET image showed high ¹¹C–Acetate uptake in the right (R) axis and low ¹¹C–Acetate uptake in the left (L) axis (yellow arrowhead), representing regions with high and low density of reactive astrocytes, respectively. MRI images at 3, 6, and 8 months showed ring-enhancing lesions with higher contrast in the left axis (red arrowhead), suggesting the tumor was outgrowing towards left side which had low density of reactive astrocytes. c Inhibition of glutamate–MAO-B attenuating astrocytic scar while promoting tumor growth in GBM patient-derived assembloids. White arrowheads indicates the invasion of GBM cells to region with low density of astrocytes. d Quantitative data for the number of scar-forming astrocytes in the GBM patient-derived assembloid. e Quantitative data for GBM area in the GBM patient-derived assembloid. *, p < 0.05; **, p < 0.01. p values were calculated by one-way ANOVA for multiple comparison. Scale bars represent 100 μm. PT, peri-tumor; AT, away from tumor; MRI, magnetic resonance imaging; PET, positron emission tomography