P67
GENOME-WIDE IDENTIFICATION OF HYPOXIA INDUCIBLE FACTOR
TRANSCRIPTIONAL TARGETS IN RENAL CANCER (HIF PATHWAYS IN RENAL
CANCER)
Schödel, J¹, Blancher, C¹, Baban, D¹, Ragoussis,I¹, Pugh, C¹ ², Ratcliffe, P¹, Mole, D¹ ²
¹The Wellcome Trust Centre For Human Genetics, Centre For Cellular And Molecular
Physiology, University of Oxford, Oxford, ²The Oxford Kidney Unit, Churchill Hospital,
Oxford
Genetic activation of hypoxia pathways in renal cancer is essential to the formation of tumours
and has provided novel therapeutic targets. Mechanisms include tumour suppressor inactivation
(e.g. VHL or fumarate hydratase) and/or activation of (PI3K)/Akt/mTOR, which all lead to
upregulation of the hypoxia inducible factor (HIF) transcriptional pathway. All known RCCassociated VHL mutations affect HIF degradation and genetic manipulation of the HIF pathway
in RCC cells affects tumourigenicity, independently of VHL itself indicating that the HIF plays a
causal role in clear cell RCC. Furthermore, the hereditary cancer syndrome, HLRCC, caused by
inactivating mutations in fumarate hydratase (FH) is associated with aggressive papillary renal
cancers, and constitutive activation of the HIF pathway, implicating HIF in the pathogenesis of
both papillary and clear cell renal cancer. Indeed, manipulation of the HIF pathway through the
use of mTOR inhibitors, antiangiogenic therapy and VEGF receptor kinase inhibitors provides
the basis for exciting new therapeutic strategies in RCC.
Whilst HIF-activation is necessary for the development of renal cancer, it is insufficient on its
own, with the balance between pro- and anti-tumourigenic HIF-activated pathways needing to be
distorted before tumours can form. Indeed the HIF-transcriptional cascade is highly abnormal in
renal cancer, both in the balance between the HIF-1 and HIF-2 isoforms and in terms of the range
of target genes activated. For instance, cyclin D1, normally unresponsive to HIF is activated by
HIF-2, but not by HIF-1 in RCC cells. These differences and the mechanisms underlying them
provide potential novel therapeutic targets for the treatment of RCC as well as possible
biomarkers for disease activity.
Using a combination of genome-wide expression profiling and chromatin immunoprecipitation
linked to high throughput next generation sequencing on the Illumina platform we define the
entire network of direct transcriptional targets of the HIF cascade in renal cancer cells. We
identify the HIF DNA-binding site at each regulated gene locus and confirm the widely held
consensus-binding motif. Functional analysis of these HIF target genes demonstrates known HIFregulated pathways and identifies novel HIF-dependent pathways. In particular we identify
regulatory histone modifying enzymes amongst direct transcriptional targets of the VHL-HIF
pathway. Activating mutations in some of these enzymes have recently been identified in renal
cancer by the Wellcome Trust Sanger Institute Catalogue of Somatic Mutations in Cancer
(COSMIC), implicating them causally in the pathogenesis of renal cancer. These constitute
attractive therapeutic targets to compliment existing anti-angiogenic therapies and mTOR
inhibitors.