gms | German Medical Science

Objective: Oxygen tension plays a major role in the pathogenesis of malignancies. Numerous studies have shown that low oxygen concentrations (hypoxia) affect stem cell behavior and inhibit the ability to differentiate. Especially in glioblastoma stem cells the hypoxic niche seems to play an essential role for therapeutic resistance.

Method: Three well-characterized glioblastoma stem cell lines were grown under serum-free normoxic (20%) and hypoxic (1.0%) culture conditions. mRNA was harvested after 72 hrs. Gene expression analyses was performed on a two-color Agilent^® Gene Expression Microarray. Differentially expressed genes were defined by upregulation / downregulation by over two fold. Possible survival associations of candidate genes were analyzed by using i) expression data of 480 glioblastoma cases from the “The Cancer Genome Atlas” (TCGA) and ii) an independent study sample consisting of 161 glioblastoma tissues resected in our institution via qPCR.

Results: The differential gene expression analyses comparing mRNA expression of normoxic vs. hypoxic tumor stem cells revealed a significant upregulation of 105 and a downregulation of 72 candidate genes (p≤0.01). Among these genes overexpression of ENO1, ICAM5, LDHA and VGF as well as downregulation of FHOD3 and SAE1 were significantly related with poorer survival of glioblastoma patients in the TCGA data set. Validation in an independent study sample via qPCR confirmed the observed survival association for SAE1 especially for glioblastoma patients who received a combined radiochemotherapy.

Conclusions: The present study identifies a number of hypoxia-regulated candidate genes in glioblastoma stem cells impacting survival of glioblastoma patients and thus suggesting an important contribution to tumor stem cell biology. Further experiments are necessary to clarify and validate the functional role of these genes in gliomagenesis and therapy resistance.