Neural stem cells adopt tumorigenic properties by constitutively activated NF-kappaB and subsequent VEGF up-regulation.
One of the challenges in stem cell research is to avoid transformation during cultivation. We studied high passage subventricular zone derived neural stem cells (NSCs) cultures of adult rats in the absence of growth factors epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). We termed this culture exogenous growth factor independent neural stem cells (GiNSCs). GiNSCs expressed stemness markers, displayed a high constitutive NF-kappaB activity and an increased, aberrant, polyploid DNA content. GiNSCs showed a tumorigenic phenotype and formed colonies in a soft agar assay. Microarray analysis showed the up-regulation of the NF-kappaB target gene vascular endothelial growth factor (VEGF). In contrast, proneuronal genes were down-regulated. Under neuronal differentiation conditions GiNSCs adopted a glioma-like phenotype, with nuclear p53, preserving high amounts of Nestin positive cells and prolonged proliferation. Neutralization of VEGF strongly inhibited proliferation and induced differentiation. In a gain of function approach, the transfection of NSCs with constitutively active upstream kinase IKK-2 led to constitutively activated NF-kappaB, proliferation in absence of growth factors and augmented VEGF secretion. In a rescue experiment a reduction of NF-kappaB activity by overexpression of IkappaB-AA1 was able to shift the morphology toward an elongated cell form, increased cell death, and decreased proliferation. Thus GiNSCs may provide a potent tool in cancer research, as their exogenous cytokine independent proliferation and their constitutively high NF-kappaB expression presumes cancerous properties observed in gliomas. In addition, this study might add a novel mechanism for detecting oncogenic transformation in therapeutic stem cell cultures.
Kaus
Aljoscha
A
Department of Molecular Cellular and Developmental Biology, Yale University , New Haven, Connecticut, USA.
Widera
Darius
D
Kassmer
Susannah
S
Peter
Jan
J
Zaenker
Kurt
K
Kaltschmidt
Christian
C
Kaltschmidt
Barbara
B
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D046228:Microarray Analysis; D016328:NF-kappa B / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010641:Phenotype; D051381:Rats; D017208:Rats, Wistar; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D015415:Biomarkers; D016328:NF-kappa B; D016159:Tumor Suppressor Protein p53; D042461:Vascular Endothelial Growth Factor A