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Loss of VHL and hypoxia provokes PAX2 up-regulation in clear cell renal cell carcinoma


Luu, V D; Boysen, G; Struckmann, K; Casagrande, S; von Teichman, A; Wild, P J; Sulser, T; Schraml, P; Moch, H (2009). Loss of VHL and hypoxia provokes PAX2 up-regulation in clear cell renal cell carcinoma. Clinical Cancer Research, 15(10):3297-3304.

Abstract

PURPOSE: The paired box gene 2, PAX2, encodes for a transcription factor that is up-regulated during nephrogenesis and becomes silenced in mature epithelium of the glomeruli, the proximal, and distal tubules. Reactivation of PAX2 has been frequently observed in clear cell renal cell carcinoma (ccRCC), a tumor type characterized by loss of von Hippel-Lindau (VHL) tumor suppressor function. The regulation of PAX2 expression in ccRCC is unknown. EXPERIMENTAL DESIGN: We applied reporter gene assays to investigate PAX2 promoter regulation. Furthermore, PAX2 expression was determined in ccRCC cell lines under normoxic and hypoxic condition in a VHL wild-type and mutated background. PAX2 expression was also assessed in 831 human ccRCC and correlated with hypoxia-inducible factor alpha (HIFalpha) and clinical parameters. RESULTS: Here, we show that both loss of VHL protein (pVHL) function and hypoxia leads to strong PAX2 reexpression. Using luciferase reporter gene assays, no induction was obtained in spite of six hypoxia response element motifs identified in the promoter of PAX2. Comprehensive immunohistochemical analyses showed significant correlations between PAX2, HIF1alpha, and HIF2alpha-target CCND1 expression patterns in ccRCC patients. Notably, PAX2 expression was highly associated with early-stage, well-differentiated ccRCC and, consequently, better clinical outcome (P < 0.0001 each). Additional analyses indicated that PAX2 repressor WT1 and cancer-linked hypomethylation are not important for transcriptional regulation of PAX2 in ccRCC. CONCLUSION: We conclude that in ccRCC, PAX2 reactivation is driven by HIF-dependent mechanisms following pVHL loss.

Abstract

PURPOSE: The paired box gene 2, PAX2, encodes for a transcription factor that is up-regulated during nephrogenesis and becomes silenced in mature epithelium of the glomeruli, the proximal, and distal tubules. Reactivation of PAX2 has been frequently observed in clear cell renal cell carcinoma (ccRCC), a tumor type characterized by loss of von Hippel-Lindau (VHL) tumor suppressor function. The regulation of PAX2 expression in ccRCC is unknown. EXPERIMENTAL DESIGN: We applied reporter gene assays to investigate PAX2 promoter regulation. Furthermore, PAX2 expression was determined in ccRCC cell lines under normoxic and hypoxic condition in a VHL wild-type and mutated background. PAX2 expression was also assessed in 831 human ccRCC and correlated with hypoxia-inducible factor alpha (HIFalpha) and clinical parameters. RESULTS: Here, we show that both loss of VHL protein (pVHL) function and hypoxia leads to strong PAX2 reexpression. Using luciferase reporter gene assays, no induction was obtained in spite of six hypoxia response element motifs identified in the promoter of PAX2. Comprehensive immunohistochemical analyses showed significant correlations between PAX2, HIF1alpha, and HIF2alpha-target CCND1 expression patterns in ccRCC patients. Notably, PAX2 expression was highly associated with early-stage, well-differentiated ccRCC and, consequently, better clinical outcome (P < 0.0001 each). Additional analyses indicated that PAX2 repressor WT1 and cancer-linked hypomethylation are not important for transcriptional regulation of PAX2 in ccRCC. CONCLUSION: We conclude that in ccRCC, PAX2 reactivation is driven by HIF-dependent mechanisms following pVHL loss.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Urological Clinic
04 Faculty of Medicine > University Hospital Zurich > Institute of Pathology and Molecular Pathology
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:2009
Deposited On:03 Jun 2009 08:28
Last Modified:05 Apr 2016 13:14
Publisher:American Association for Cancer Research
ISSN:1078-0432
Publisher DOI:https://doi.org/10.1158/1078-0432.CCR-08-2779
PubMed ID:19401348

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