Suppression of homology-dependent DNA double-strand break repair induces PARP inhibitor sensitivity in VHL-deficient human renal cell carcinoma
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Susan E. Scanlon1,2, Denise C. Hegan1,3, Parker L. Sulkowski1,3 and Peter M. Glazer1,3
1Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, USA
2Department of Experimental Pathology, Yale University School of Medicine, New Haven, CT, USA
3Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
Peter M. Glazer, email: firstname.lastname@example.org
Keywords: DNA repair; homologous recombination; von Hippel-Lindau (VHL); hypoxia; PARP inhibitor
Received: October 30, 2017 Accepted: November 28, 2017 Published: December 19, 2017
The von Hippel-Lindau (VHL) tumor suppressor gene is inactivated in the vast majority of human clear cell renal carcinomas. The pathogenesis of VHL loss is currently best understood to occur through stabilization of the hypoxia-inducible factors, activation of hypoxia-induced signaling pathways, and transcriptional reprogramming towards a pro-angiogenic and pro-growth state. However, hypoxia also drives other pro-tumorigenic processes, including the development of genomic instability via down-regulation of DNA repair gene expression. Here, we find that DNA repair genes involved in double-strand break repair by homologous recombination (HR) and in mismatch repair, which are down-regulated by hypoxic stress, are decreased in VHL-deficient renal cancer cells relative to wild type VHL-complemented cells. Functionally, this gene repression is associated with impaired DNA double-strand break repair in VHL-deficient cells, as determined by the persistence of ionizing radiation-induced DNA double-strand breaks and reduced repair activity in a homology-dependent plasmid reactivation assay. Furthermore, VHL deficiency conferred increased sensitivity to PARP inhibitors, analogous to the synthetic lethality observed between hypoxia and these agents. Finally, we discovered a correlation between VHL inactivation and reduced HR gene expression in a large panel of human renal carcinoma samples. Together, our data elucidate a novel connection between VHL-deficient renal carcinoma and hypoxia-induced down-regulation of DNA repair, and identify potential opportunities for targeting DNA repair defects in human renal cell carcinoma.
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