1. Hypoxia-inducible factor (HIF)-prolyl hydroxylase 3 (PHD3) maintains high HIF2A mRNA levels in clear cell renal cell carcinoma
- Author
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Heidi Högel, Krista Rantanen, Panu Jaakkola, Fatemeh Seyednasrollah, Petra Miikkulainen, Laura L. Elo, Department of Oncology, Clinicum, University of Helsinki, and HUS Comprehensive Cancer Center
- Subjects
0301 basic medicine ,PROTEIN ,Biochemistry ,mRNA decay ,Gene expression ,Basic Helix-Loop-Helix Transcription Factors ,TRANSCRIPTION ,PROTEASOME ,cancer biology ,GENE-EXPRESSION ,Glucose Transporter Type 1 ,Gene knockdown ,Egl-9 family hypoxia-inducible factor 3 (EGLN3) ,Protein Stability ,Chemistry ,CANCER ,Kidney Neoplasms ,Gene Expression Regulation, Neoplastic ,Hypoxia-inducible factors ,Gene Knockdown Techniques ,Signal transduction ,renal cell carcinoma ,prolyl hydroxylase PHD3 ,3122 Cancers ,PROLYL HYDROXYLASES ,Down-Regulation ,HIF-1-ALPHA ,ta3111 ,Hypoxia-Inducible Factor-Proline Dioxygenases ,03 medical and health sciences ,Cell Line, Tumor ,medicine ,Humans ,Gene silencing ,Gene Silencing ,RNA, Messenger ,Carcinoma, Renal Cell ,Molecular Biology ,Post-transcriptional regulation ,STABILITY ,030102 biochemistry & molecular biology ,hypoxia ,ccRCC ,HIF-1 ,ta1182 ,Cell Biology ,ta3122 ,medicine.disease ,hypoxia-inducible factor (HIF) ,Clear cell renal cell carcinoma ,030104 developmental biology ,HIF1A ,Cancer research ,1182 Biochemistry, cell and molecular biology ,TRANSLATION ,post-transcriptional regulation - Abstract
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.
- Published
- 2019