Suppression of Homology-dependent DNA Double-strand Break Repair Induces PARP Inhibitor Sensitivity in -deficient Human Renal Cell Carcinoma

The von Hippel-Lindau () tumor suppressor gene is inactivated in the vast majority of human clear cell renal carcinomas. The pathogenesis of 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 -deficient renal cancer cells relative to wild type -complemented cells. Functionally, this gene repression is associated with impaired DNA double-strand break repair in -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, deficiency conferred increased sensitivity to PARP inhibitors, analogous to the synthetic lethality observed between hypoxia and these agents. Finally, we discovered a correlation between inactivation and reduced HR gene expression in a large panel of human renal carcinoma samples. Together, our data elucidate a novel connection between -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.