The significance of applying different reference genes for the estimation of the relative quantities of gene expression, was demonstrated here by the analysis of 12 target genes, candidates of being over expressed in GBM, following three normalization approaches: i) with geNorm normalization factors calculated for TBP+HPRT1; ii) with GUSB, which is ~4.7 times increased in tumors; and iii) with 18S rRNA, which is ~13% decreased in GBM samples. Here, GUSB is linked to glioblastoma.