ABSTRACT
Patients with a germline mutation in von Hippel-Lindau (VHL) develop renal cell cancers and hypervascular tumors of the brain, adrenal glands, and pancreas as well as erythrocytosis. These phenotypes are driven by aberrant expression of HIF2α, which induces expression of genes involved in cell proliferation, angiogenesis, and red blood cell production. Currently, there are no effective treatments available for VHL disease. Here, using an animal model of VHL, we report a marked improvement of VHL-associated phenotypes following treatment with HIF2α inhibitors. Inactivation of vhl in zebrafish led to constitutive activation of HIF2α orthologs and modeled several aspects of the human disease, including erythrocytosis, pathologic angiogenesis in the brain and retina, and aberrant kidney and liver proliferation. Treatment of vhl(-/-) mutant embryos with HIF2α-specific inhibitors downregulated Hif target gene expression in a dose-dependent manner, improved abnormal hematopoiesis, and substantially suppressed erythrocytosis and angiogenic sprouting. Moreover, pharmacologic inhibition of HIF2α reversed the compromised cardiac contractility of vhl(-/-) embryos and partially rescued early lethality. This study demonstrates that small-molecule targeting of HIF2α improves VHL-related phenotypes in a vertebrate animal model and supports further exploration of this strategy for treating VHL disease.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors/antagonists & inhibitors , Hydrazones/therapeutic use , Sulfones/therapeutic use , von Hippel-Lindau Disease/drug therapy , 5' Untranslated Regions , Amino Acids, Dicarboxylic/toxicity , Animals , Basic Helix-Loop-Helix Transcription Factors/deficiency , Basic Helix-Loop-Helix Transcription Factors/genetics , Brain/blood supply , Disease Models, Animal , Drug Evaluation, Preclinical , Embryo, Nonmammalian , Gene Expression Regulation/drug effects , Humans , Hydrazones/pharmacology , Hypoxia-Inducible Factor 1, alpha Subunit/deficiency , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Kidney/pathology , Liver/pathology , Myocardial Contraction/drug effects , Neovascularization, Pathologic/drug therapy , Neovascularization, Pathologic/genetics , Phenotype , Polycythemia/drug therapy , Polycythemia/genetics , Retinal Vessels/pathology , Sulfones/pharmacology , Tumor Suppressor Proteins/deficiency , Tumor Suppressor Proteins/genetics , Zebrafish/embryology , Zebrafish/genetics , Zebrafish Proteins/deficiency , Zebrafish Proteins/genetics , von Hippel-Lindau Disease/genetics , von Hippel-Lindau Disease/pathology , von Hippel-Lindau Disease/physiopathologyABSTRACT
Hypoxic and VHL-deficient cells use glutamine to generate citrate and lipids through reductive carboxylation (RC) of α-ketoglutarate. To gain insights into the role of HIF and the molecular mechanisms underlying RC, we took advantage of a panel of disease-associated VHL mutants and showed that HIF expression is necessary and sufficient for the induction of RC in human renal cell carcinoma (RCC) cells. HIF expression drastically reduced intracellular citrate levels. Feeding VHL-deficient RCC cells with acetate or citrate or knocking down PDK-1 and ACLY restored citrate levels and suppressed RC. These data suggest that HIF-induced low intracellular citrate levels promote the reductive flux by mass action to maintain lipogenesis. Using [(1-13)C]glutamine, we demonstrated in vivo RC activity in VHL-deficient tumors growing as xenografts in mice. Lastly, HIF rendered VHL-deficient cells sensitive to glutamine deprivation in vitro, and systemic administration of glutaminase inhibitors suppressed the growth of RCC cells as mice xenografts.
