GRK2 and glioblastoma: Based on the information from our RRBS methylome, here we selected four catecholamine markers differentially methylated at the cohort level (alpha 1D adrenergic receptor—ADRA1D; adrenergic beta receptor kinase 1 or G protein-coupled receptor kinase 2—ADRBK1/GRK2; dopamine receptor D2—DRD2; and synaptic vesicle monoamine transporter—SLC18A2; Supplementary Table S1a) [2], and analyzed further their involvement in GBM.