Normoxic accumulation of HIF1 alpha is associated with glutaminolysis
Kappler M, Pabst U, Rot S, Taubert H, Wichmann H, Schubert J, Bache M, Weinholdt C, Immel UD, Grosse I, Vordermark D, Eckert AW (2017)
Publication Type: Journal article
Publication year: 2017
Journal
Book Volume: 21
Pages Range: 211-224
Journal Issue: 1
DOI: 10.1007/s00784-016-1780-9
Abstract
The stabilization of the transcription factor and prognostic tumor marker hypoxia-inducible factor 1 alpha (HIF1 alpha) is considered to be crucial for cellular metabolic adaptations to hypoxia. However, HIF1 alpha has also been shown to accumulate under normoxic conditions, although this phenomenon is poorly understood. We investigated the conditions for normoxic HIF1 alpha stabilization in different tumor cell lines (e.g., two mammary carcinoma cell lines and three oral squamous cell carcinoma cell lines) via Western blot analysis or immunohistochemical staining. The transcriptional activity of HIF1 was demonstrated by analyzing the messenger RNA (mRNA) expression of the HIF1 target carbonic anhydrase 9 (CA9) via PCR. Our data demonstrate that the combined incubation of tumor cells with glutamine and growth factors (e.g., EGF, insulin, and serum) mediates the normoxic accumulation of HIF1 alpha in vitro. Consequently, the inhibition of glutaminolysis by a glutaminase inhibitor blocked the normoxic accumulation of HIF1 alpha. Additionally, the normoxic HIF1 alpha protein displayed nuclear translocation and transcriptional activity, which was confirmed by the induction of CA9 mRNA expression. Furthermore, the normoxic accumulation of HIF1 alpha was associated with impaired proliferation of tumor cells. Finally, ammonia, the toxic waste product of glutaminolysis, induced a normoxic accumulation of HIF1 alpha to the same extent as glutamine. Our study suggests that HIF1 alpha is involved in the regulation of glutamine metabolism and the cellular levels of the toxic metabolic waste product ammonia under normoxia. Hence, our results, together with data presented in the literature, support the hypothesis that HIF1 alpha and its target genes play a crucial role in metabolic pathways, such as glutaminolysis and glycolysis, under both hypoxic and normoxic conditions. Therefore, the inhibition of HIF1 alpha (and/or HIF1 alpha target genes) could emerge as a promising therapeutic approach that would result in the accumulation of toxic metabolic waste products in tumor cells as well as the reduction of their nutrition and energy supply.
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Germany (DE)How to cite
APA:
Kappler, M., Pabst, U., Rot, S., Taubert, H., Wichmann, H., Schubert, J.,... Eckert, A.W. (2017). Normoxic accumulation of HIF1 alpha is associated with glutaminolysis. Clinical Oral Investigations, 21(1), 211-224. https://dx.doi.org/10.1007/s00784-016-1780-9
MLA:
Kappler, Matthias, et al. "Normoxic accumulation of HIF1 alpha is associated with glutaminolysis." Clinical Oral Investigations 21.1 (2017): 211-224.
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