GRM2 and glioma: Opposite association was observed when expression of GluR2 was analyzed, which proved to be present in slow-growing GBM-derived tumor stem cells (GBM TSCs) and low-grade tumor samples but not in fast-growing gliomas or high-grade tumor specimens, indicating that GluR2 expression is associated with a low degree of malignancy (Beretta et al. 2009).