Inhibition of Hypoxia-Inducible Factor Is Sufficient for Growth Suppression of VHL−/− Tumors

Abstract

The von Hippel-Lindau tumor suppressor protein (pVHL) is a substrate receptor for the mammalian SCF-2 E3 ubiquitin ligase complex that targets several substrates for ubiquitination and proteasomal degradation. Among these targets are the α-regulatory subunits of the hypoxia-inducible factor (HIF). VHL−/− cells constitutively overexpress hypoxia-inducible genes through both transcriptional and posttranscriptional mechanisms and form tumors when injected into nude mice. Reintroduction of pVHL into VHL−/− cell lines restores normal oxygen-dependent regulation of these genes and suppresses tumor formation in the mouse xenograft assay. We report here that short hairpin RNA-mediated inactivation of HIF phenocopies the effects of pVHL reintroduction with respect to decreased expression of hypoxia-inducible genes, decreased ability to promote vascular endothelial cell proliferation in vitro, and tumor growth suppression in vivo. In addition, HIF inactivation abrogated the cellular response to hypoxia, indicating that HIF is the only pVHL target required for this response. These data suggest that deregulation of hypoxia-inducible genes in VHL−/− cells can be attributed mainly to deregulation of HIF and validate HIF as a therapeutic anticancer drug target.

MIIP inhibits clear cell renal cell carcinoma proliferation and angiogenesis via negative modulation of the HIF-2α-CYR61 axis

“…Although HIF-1α and HIF-2α share significant homology, a tripartite structure, and a degradation pathway, HIF-2α, but not HIF-1α, has been clearly established as the dominant isoform that plays a crucial role in ccRCC initiation and progression 8 , 10 , 12 , 47 , 48 . Importantly, eliminating HIF-2α is sufficient to suppress VHL-defective tumor growth 49 , 50 . These findings highlight targeting HIF-2α as a promising potential strategy for ccRCC treatment.…”

Design and Activity of Specific Hypoxia-Inducible Factor-2α (HIF-2α) Inhibitors for the Treatment of Clear Cell Renal Cell Carcinoma: Discovery of Clinical Candidate (S)-3-((2,2-Difluoro-1-hydroxy-7-(methylsulfonyl)-2,3-dihydro-1H-inden-4-yl)oxy)-5-fluorobenzonitrile (PT2385)

“…Step D: Preparation of S-(3-Bromo-2-cyano-4-fluorophenyl) Ethanethioate. To a mixture of 2-bromo-3-fluoro-6-iodobenzonitrile (14) (1.00 g, 3.07 mmol), Pd 2 (dba) 3 (140 mg, 0.150 mmol), potassium ethanethiolate (350 mg, 3.07 mmol), and Xantphos (178 mg, 0.310 mmol) under argon was added degassed toluene (8 mL) and acetone (4 mL). The mixture was flushed with nitrogen, sealed, and heated at 72 °C overnight.…”

“…Several studies support the pathophysiological role of HIF-2α in ccRCC. Knockdown of HIF-2α expression in VHL defective ccRCC xenografts impedes tumor formation comparable to reintroduction of VHL, and overexpression of a stabilized variant of HIF-2α alone is adequate to overcome pVHL’s tumor suppressive effect. , Significantly, the status of HIF-1α appears inconsequential in the course of ccRCC: HIF-1α is often deleted or mutated, and a stabilized variant of HIF-1α does not inhibit tumor suppression by pVHL. − This evidence implicates HIF-2α as the tumorigenic driver in ccRCC and suggests that HIF-2α antagonists could provide novel therapeutic intervention for its treatment.…”

3-[(1S,2S,3R)-2,3-Difluoro-1-hydroxy-7-methylsulfonylindan-4-yl]oxy-5-fluorobenzonitrile (PT2977), a Hypoxia-Inducible Factor 2α (HIF-2α) Inhibitor for the Treatment of Clear Cell Renal Cell Carcinoma

“…In the majority of patients, ccRCC is characterized by inactivation of the tumor suppressor von Hippel–Lindau (VHL) due to genetic predisposition, somatic mutations, or methylation. , The VHL protein (pVHL) is a component of an E3 ubiquitin ligase complex that mediates protein degradation by the proteasome. A principal role of pVHL is the regulation of the hypoxia-inducible factor (HIF) family of transcription factors consisting of HIF-1α, HIF-2α, and the less well characterized HIF-3α. − Unlike HIF-1α, in adults the expression of HIF-2α is limited to endothelial cells, kidney fibroblasts, hepatocytes, intestinal lumen epithelial cells, pancreatic interstitial cells, heart myocytes, interstitial cells, and lung type II pneumocytes. , Importantly, HIF-2α activity has been demonstrated to be a key oncogenic driver in ccRCC. − In mouse ccRCC tumor models, knockdown of HIF-2α expression in pVHL defective cell lines blocked tumor growth comparable to reintroduction of pVHL. In addition, expression of a stabilized variant of HIF-2α was able to overcome the tumor suppressive role of pVHL.…”