Regression of solid tumors by engineered overexpression of von Hippel-Lindau tumor suppressor protein and antisense hypoxia-inducible factor-1alpha.
The von Hippel-Lindau tumor suppressor protein (pVHL) suppresses tumor formation by binding the alpha subunits of hypoxia-inducible factors (HIFs) responsible for stimulating tumor angiogenesis and glycolysis, targeting them for ubiquitination and proteasomal destruction. Loss of pVHL leads to the development of sporadic renal cell carcinomas (RCCs). In the present study, we sought to determine whether engineered overexpression of pVHL in tumors other than RCC can inhibit tumor growth, either as a monotherapy, or in combination with antisense HIF-1alpha therapy. Intratumoral injection of subcutaneous EL-4 thymic lymphomas with an expression plasmid encoding pVHL resulted in the downregulation of HIF-1alpha and vascular endothelial growth factor (VEGF). There was a concomitant reduction in tumor angiogenesis and increased tumor cell apoptosis due in part to downregulation of Bcl-2 expression. VHL therapy resulted in the complete regression of small (0.1 cm diameter) tumors whereas, in contrast, large (0.4 cm diameter) EL-4 tumors were only slowed in their growth. Nevertheless, large tumors completely regressed in response to intratumoral injection of a combination of antisense HIF-1alpha and VHL plasmids. Combination therapy resulted in increased losses of HIF-1alpha, VEGF, and tumor blood vessels, and increased tumor cell apoptosis. These novel results suggest that synergistic therapies that simultaneously block the expression or function of HIF-1alpha, and enhance the expression or function of VHL may be beneficial in the treatment of cancer.
Department of Molecular Medicine and Pathology, Faculty of Medicine and Health Science, University of Auckland, Auckland, New Zealand.
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X
Sun
J R
JR
Kanwar
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Leung
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Vale
G W
GW
Krissansen
D020533:Angiogenesis Inhibitors / Q000032:analysis / Q000235:genetics*; D000818:Animals; D017209:Apoptosis; D004247:DNA / Q000008:administration & dosage*; D005786:Gene Expression Regulation; D015316:Genetic Therapy / Q000379:methods*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D015552:Injections, Intralesional; D008223:Lymphoma / Q000473:pathology / Q000628:therapy*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental; D016376:Oligonucleotides, Antisense / Q000627:therapeutic use; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000032:analysis / Q000235:genetics*; D044767:Ubiquitin-Protein Ligases / Q000032:analysis / Q000235:genetics*; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis / Q000235:genetics; D051794:Von Hippel-Lindau Tumor Suppressor Protein
D020533:Angiogenesis Inhibitors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D016376:Oligonucleotides, Antisense; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D004247:DNA; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein