Identification of novel hypoxia dependent and independent target genes of the von Hippel-Lindau (VHL) tumour suppressor by mRNA differential expression profiling

Abstract

The von Hippel-Lindau tumour suppressor gene (VHL) targets hypoxia inducible factor (HIF)-a subunits for ubiquitin dependent proteolysis. To better understand the role of this and other putative pathways of gene regulation in VHL function we subjected mRNA from VHL defective renal carcinoma cells and transfectants re-expressing a wild type VHL allele to di erential expression pro®ling, and analysed VHL target genes for oxygen regulated expression. Among a group of newly identi®ed VHL target genes the majority but not all were regulated by oxygen, indicating that whilst dysregulation of the HIF system makes a dominant contribution to alterations in transcription, VHL has other in¯uences on patterns of gene expression. Genes newly de®ned as targets of the VHL/hypoxia pathway (conditionally downregulated by VHL in normoxic cells) include aminopeptidase A, collagen type V, alpha 1, cyclin G2, DEC1/Stra13, endothelin 1, low density lipoprotein receptor-related protein 1, MIC2/CD99, and transglutaminase 2. These genes have a variety of functions relevant to tumour biology. However, not all are connected with the promotion of tumour growth, some being pro-apoptotic or growth inhibitory. We postulate that co-ordinate regulation as part of the HIF pathway may explain this paradox, and that evolution of antiapoptotic pathways may be required for tumour growth under VHL-dysregulation. Our results indicate that it will be necessary to consider the e ects of abnormal activity in integral regulatory pathways, as well as the e ects of individual genes to understand the role of abnormal patterns of gene expression in cancer. Oncogene (2000) 19, 6297 ± 6305.

Gene array of VHL mutation and hypoxia shows novel hypoxia-induced genes and that cyclin D1 is a VHL target gene

“…For details of riboprobe templates employed to examine the expression of previously described VHL-responsive genes, see Wykoff et al (2000). Quantification of the protected species from 30 mg was performed using a phosphoimager (Molecular Dynamics), and related to an internal control assay for the constitutively expressed U6 small nuclear RNA (LC), performed for each assay as described (Maxwell et al, 1999).…”

“…In particular, the mechanisms for tissue specificity of the effects of VHL mutation are unknown. Recently, we and others have identified a number of new pVHL target genes and demonstrated that many of these were hypoxia-responsive in wild-type pVHL cell lines (Koong et al, 2000;Wykoff et al, 2000;Lal et al, 2001). Whether there are other hypoxia non-VHL regulated pathways in renal cell lines is unknown.…”

“…There were no genes regulated by hypoxia independently of VHL, but there were genes regulated by VHL that were not hypoxia regulated in the renal cell line used for the study. The unexpectedly high concordance prompted us to analyse hypoxia regulation of genes in the latter class in other cell types, and also genes from our previous study of VHL regulated genes in a different renal cell type (Wykoff et al, 2000), which were VHL but not hypoxia responsive. These genes were clearly regulated by hypoxia in other nonrenal cell types.…”

Angiogenesis and hypoxia in lymph node metastases is predicted by the angiogenesis and hypoxia in the primary tumour in patients with breast cancer

“…Under hypoxic conditions, hypoxia-inducible factor-1a (Hif-1a) is stabilized and serves to propagate a cascade of pathways which include angiogenesis, glycolysis, proliferation and alterations in microenvironmental pH (carbonic anhydrase 9 (CA9)) (Semenza, 1999). Differentiated embryo-chondrocyte-expressed gene 1 (DEC-1) or STRA13 is one of the transcription factors involved in cell differentiation, proliferation and apoptosis that has been shown to be Hif-1a regulated (Wykoff et al, 2000). The expression patterns of CA9, Hif-1a and DEC-1 have been shown to correlate with each other, with angiogenesis and with the expression of angiogenic factors Chakrabarti et al, 2004;Currie et al, 2004;Bos et al, 2005;Vleugel et al, 2005).…”

Interplay between receptor tyrosine kinases and hypoxia signaling in cancer

“…Numerous genes, including those encoding for RTKs and their ligands and whose expression is regulated under hypoxic conditions, either directly by HIF-1α and HIF-2α transcriptional activation or by distinct hypoxia-driven mechanisms, have been identified and described using expression profiling studies [19][20][21][22]. In this chapter, we will focus on RTK systems that are transcriptionally activated by HIF-1α and HIF-2α and we will also describe HIF-1α-and HIF-2α-independent mechanisms that were shown to stimulate RTKs signaling under hypoxic conditions ( Figure 1).…”