MTOR and central nervous system cancer: The reason why N‐acetylgalactosaminyltransferase 2 (GALNT2) was closely associated with the migration and invasion of glioma cells is that GALNT2 facilitated the malignant features of gliomas by affecting the O‐glycosylation, EGFR phosphorylation, and subsequently the downstream PI3K/Akt/mTOR axis.25