In-vivo protein expression of human housekeeping genes GAPDH, β-actin and γ-tubulin in biopsies of normal brain (NB), low-grade astrocytoma and glioblastoma. (A) Western-blot analysis of tissue lysates. GAPDH, β-actin and γ-tubulin are homogenously expressed by all analysed samples. (B) Expression intensities of the bands in the Western blot were densitometrically evaluated. The bar graphs show GAPDH expression after normalization to the corresponding expression of β-actin. No GAPDH upregulation in the more hypoxic glioblastoma samples in comparison to low-grade astrocytoma was detectable. (C) Densitometric evaluation of γ-tubulin expression in the human brain tumor tissues. Band intensities are shown as bar graphs. No regulatory effect of hypoxic conditions in vivo on housekeeping gene expression could be detected.