GAPDH is not regulated in human glioblastoma under hypoxic conditions.
BACKGROUND
Gene expression studies related to cancer diagnosis and treatment are becoming more important. Housekeeping genes that are absolutely reliable are essential for these studies to normalize gene expression. An incorrect choice of housekeeping genes leads to interpretation errors of experimental results including evaluation and quantification of pathological gene expression. Here, we examined (a) the degree of regulation of GAPDH expression in human glioblastoma cells under hypoxic conditions in vitro in comparison to other housekeeping genes like beta-actin, serving as experimental loading controls, (b) the potential use of GAPDH as a target for tumor therapeutic approaches and (c) differences in GAPDH expression between low-grade astrocytomas and glioblastomas, for which modest and severe hypoxia, respectively, have been previously demonstrated. GAPDH and beta-actin expression was comparatively examined in vivo in human low-grade astrocytoma and glioblastoma on both protein and mRNA level, by Western blot and semiquantitative RT-PCR, respectively. Furthermore, the same proteins were determined in vitro in U373, U251 and GaMG human glioblastoma cells using the same methods. HIF-1alpha protein regulation under hypoxia was also determined on mRNA level in vitro in GaMG and on protein level in U251, U373 and GaMG cells.


RESULTS
We observed no hypoxia-induced regulatory effect on GAPDH expression in the three glioblastoma cell lines studied in vitro. In addition, GAPDH expression was similar in patient tumor samples of low-grade astrocytoma and glioblastoma, suggesting a lack of hypoxic regulation in vivo.


CONCLUSIONS
GAPDH represents an optimal choice of a housekeeping gene and/or loading control to determine the expression of hypoxia induced genes at least in glioblastoma. Because of the lack of GAPDH regulation under hypoxia, this gene is not an attractive target for tumor therapeutic approaches in human glioblastoma.
Said
Harun M
HM
University of Würzburg, Dept. of Radiation Oncology, Germany. Said_H@klinik.uni-wuerzburg.de
Hagemann
Carsten
C
Stojic
Jelena
J
Schoemig
Beate
B
Vince
Giles H
GH
Flentje
Michael
M
Roosen
Klaus
K
Vordermark
Dirk
D
D000199:Actins / Q000235:genetics; D001254:Astrocytoma / Q000235:genetics; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000235:genetics*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics*; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics
D000199:Actins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases