Silencing of epidermal growth factor receptor suppresses hypoxia-inducible factor-2-driven VHL-/- renal cancer.
Inactivating mutations in the von Hippel-Lindau (VHL) tumor suppressor gene are associated with clear cell renal cell carcinoma (VHL-/- RCC), the most frequent malignancy of the human kidney. The VHL protein targets the alpha subunits of hypoxia-inducible factor (HIF) transcription factor for ubiquitination and degradation. VHL-/- RCC cells fail to degrade HIF resulting in the constitutive activation of its target genes, a process that is required for tumorigenesis. We recently reported that HIF activates the transforming growth factor-alpha/epidermal growth factor receptor (TGF-alpha/EGFR) pathway in VHL-defective RCC cells. Here, we show that short hairpin RNA (shRNA)-mediated inhibition of EGFR is sufficient to abolish HIF-dependent tumorigenesis in multiple VHL-/- RCC cell lines. The 2alpha form of HIF (HIF-2alpha), but not HIF-1alpha, drives in vitro and in vivo tumorigenesis of VHL-/- RCC cells by specifically activating the TGF-alpha/EGFR pathway. Transient incubation of VHL-/- RCC cell lines with small interfering RNA directed against EGFR prevents autonomous growth in two-dimensional culture as well as the ability of these cells to form dense spheroids in a three-dimensional in vitro tumor assay. Stable expression of shRNA against EGFR does not alter characteristics associated with VHL loss including constitutive production of HIF targets and defects in fibronectin deposition. In spite of this, silencing of EGFR efficiently abolishes in vivo tumor growth of VHL loss RCC cells. These data identify EGFR as a critical determinant of HIF-2alpha-dependent tumorigenesis and show at the molecular level that EGFR remains a credible target for therapeutic strategies against VHL-/- renal carcinoma.
Smith
Karlene
K
Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
Gunaratnam
Lakshman
L
Morley
Melissa
M
Franovic
Aleksandra
A
Mekhail
Karim
K
Lee
Stephen
S
D051792:Basic Helix-Loop-Helix Proteins; D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000517:prevention & control; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics* / Q000517:prevention & control; D034741:RNA, Small Interfering / Q000235:genetics; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000235:genetics; D016211:Transforming Growth Factor alpha / Q000096:biosynthesis / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000172:deficiency* / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency* / Q000235:genetics; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D066246:ErbB Receptors; D034741:RNA, Small Interfering; D014157:Transcription Factors; D016211:Transforming Growth Factor alpha; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C497446:VHL protein, human