SLC18A2 and glioblastoma: Since our previous epigenomic analysis did not specifically focus on individual catecholamine markers in individual tumor samples and had no expression assessments, in the present study, we aimed to analyze further the involvement of the four selected markers (ADRA1D, ADRBK1/GRK2, DRD2 and SLC18A2) in GBM, by zooming into their promoter and gene CpG methylation data in comparison with their protein expression levels in sections dissected from the same blocks of sequential GBM specimens.