A1 Refereed original research article in a scientific journal
Hypoxia-inducible factor (HIF)-prolyl hydroxylase 3 (PHD3) maintains high HIF2A mRNA levels in clear cell renal cell carcinoma
Authors: Miikkulainen Petra, Högel Heidi, Seyednasrollah Fatemeh, Rantanen Krista, Elo Laura L., Jaakkola Panu M.
Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Publication year: 2019
Journal: Journal of Biological Chemistry
Journal name in source: JOURNAL OF BIOLOGICAL CHEMISTRY
Journal acronym: J BIOL CHEM
Volume: 294
Issue: 10
First page : 3760
Last page: 3771
Number of pages: 12
ISSN: 0021-9258
eISSN: 1083-351X
DOI: https://doi.org/10.1074/jbc.RA118.004902
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/39919058
Most clear cell renal cell carcinomas (ccRCCs) have inactivation of the von Hippel-Lindau tumor suppressor protein (pVHL), resulting in the accumulation of hypoxia-inducible factor -subunits (HIF-) and their downstream targets. HIF-2 expression is particularly high in ccRCC and is associated with increased ccRCC growth and aggressiveness. In the canonical HIF signaling pathway, HIF-prolyl hydroxylase 3 (PHD3) suppresses HIF-2 protein by post-translational hydroxylation under sufficient oxygen availability. Here, using immunoblotting and immunofluorescence staining, qRT-PCR, and siRNA-mediated gene silencing, we show that unlike in the canonical pathway, PHD3 silencing in ccRCC cells leads to down-regulation of HIF-2 protein and mRNA. Depletion of other PHD family members had no effect on HIF-2 expression, and PHD3 knockdown in non-RCC cells resulted in the expected increase in HIF-2 protein expression. Accordingly, PHD3 knockdown decreased HIF-2 target gene expression in ccRCC cells and expression was restored upon forced HIF-2 expression. The effect of PHD3 depletion was pinpointed to HIF2A mRNA stability. In line with these in vitro results, a strong positive correlation of PHD3 and HIF2A mRNA expression in ccRCC tumors was detected. Our results suggest that in contrast to the known negative regulation of HIF-2 in most cell types, high PHD3 expression in ccRCC cells maintains elevated HIF-2 expression and that of its target genes, which may enhance kidney cancer aggressiveness.
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