DRD1 and glioblastoma: Our results showed that while no difference was observed between the expression of DRD1 in the high grade GBM and LGG, the GBM group had higher expression level of DRD2, DRD3, and DRD4 mRNA compared to the LGG group, and this expression profile positively correlated with that of GSC markers, Nestin, and CD133 (Figure 2A).