Fig. 1.

Immunohistochemical (IHC) staining of pediatric high-grade astrocytomas (HGA) using the anti-H3K27M antibody correlates with tumor genotype and decreased H3K27Me3 in tumors. Representative IHC of pediatric HGA using anti-H3K27M (a, c, e, g) or anti-H3K27me3 (b, d, f, h) antibodies and counterstained with hematoxylin. H3K27M shows strong nuclear positivity in tumor cells, but no staining in the nuclei of endothelial and smooth muscle cells in blood vessels in K27M mutant tumors (a, c). Tumors wild type for H3K27 show no nuclear staining with the anti-H3K27M antibody (e, g). Corresponding H3K27me3 staining on the same samples shows global decrease of the expression of this histone mark in H3K27M mutant tumors (b, d) compared to tumors wild type for this mutation (f, h). Notably, positivity for H3K27me3 was mainly seen in tumor vessels (b, d) even though a degree of intra-tumor staining was also seen in H3K27M mutant samples (d)