Whether targeting Grm3 should be confined to proneural glioblastoma remains elusive, because Grm3-positive GSCs may as well reside in other subtype glioblastomas at lower frequencies and may likewise drive the malignant phenotype of these tumors,21 and associations of the expression of single genes with survival need to be interpreted with caution. Here, GRM3 is linked to glioblastoma.