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HIF2a regulates ccRCC tumorigenesis through activation of cell cycle regulators



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Vojtasova, Erika 


Clear cell renal cell carcinoma (ccRCC) is the most frequent type of kidney cancer, with 50% 5-year survival. Genetically, ccRCCs are characterised by inactivation of VHL which is lost in 90% of cases. Inactivating mutations of VHL lead to stabilisation of HIF2α which in turn drives the expression of multiple target genes involved in ccRCC initiation. However, it is unclear whether HIF2α activation is necessary for tumour maintenance. This is of particular interest because current ccRCC therapies are not sufficient and a significant fraction of patients develop resistance. The need for new therapeutic strategies led to development of inhibitors of HIF2α which showed great efficacy in vitro, however, patient clinical studies showed high variability in outcome. This further highlights the importance of understanding the role of HIF2α and its downstream regulated pathways in ccRCC. In order to study the role of HIF2α in ccRCC maintenance, a tetracycline-controlled HIF2α system was developed and introduced into HIF2α depleted cell lines. Tumour growth upon HIF2α reintroduction confirmed the importance of HIF2α for tumour initiation in vivo. Subsequent loss of HIF2α led to significant tumour regression and no relapse was observed for 6 weeks. Using the genetic model described above, the molecular mechanisms underlying HIF2α- mediated tumour maintenance were studied. RNA-seq analysis comparing HIF2α activated versus HIF2α inactivated tumours revealed significant downregulation of genes involved in cell cycle progression such as MYC, CCND1 and TGFa. Furthermore, enhancer profiling performed through H3K27ac ChIP-seq demonstrated the activation of enhancer elements in the close vicinity of these genes. Moreover, HIF2α ChIP-seq showed that it bound the same enhancers suggesting that HIF2α interaction with these elements contributes to the activation of cell cycle progression genes. Understanding the mechanisms behind HIF2α-regulated pathways will contribute to understand the variability in patient outcome and may offer new therapeutic targets to improve patient survival in ccRCC.





Vanharanta, Sakari


tumour maintenance, cell cycle regulators, enhancer, ccRCC


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
MRC Funding, MRC Flexible supplement