Inhibition of hypoxia-inducible factor is sufficient for growth suppression of VHL-/- tumors.
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 alpha-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.
Hematology-Oncology Unit, Department of Medicine, Massachusetts General Hospital and the Massachusetts General Hospital Cancer Center, Boston, MA 02114, USA.
Michael
M
Zimmer
Darrell
D
Doucette
Naila
N
Siddiqui
Othon
O
Iliopoulos
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002292:Carcinoma, Renal Cell / Q000098:blood supply / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division; D045744:Cell Line, Tumor; D042783:Endothelial Cells; D017353:Gene Deletion; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology; D007680:Kidney Neoplasms / Q000098:blood supply / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D009389:Neovascularization, Pathologic; D010641:Phenotype; D034622:RNA Interference; D015534:Trans-Activators / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D014471:Umbilical Veins; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis / Q000096:biosynthesis; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D042461:Vascular Endothelial Growth Factor A; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C467484:VEGFA protein, human; C497446:VHL protein, human