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Oncotarget. 2015 Nov 3;6(34):35755-69. doi: 10.18632/oncotarget.5928.

Chemogenetic profiling identifies RAD17 as synthetically lethal with checkpoint kinase inhibition.

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Department of Medicine, University of California San Diego, La Jolla, CA, USA.
Moores Cancer Center, University of California San Diego, La Jolla, CA, USA.
Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA.
Bioinformatics and Systems Biology Program, University of California San Diego, La Jolla, CA, USA.
Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA, USA.
University of South Alabama Mitchell Cancer Institute, Mobile, AL, USA.
Ludwig Institute for Cancer Research, University of California San Diego, La Jolla, CA, USA.
Department of Toxicogenetics, Leiden University Medical Center, Einthovenweg, Leiden, The Netherlands.


Chemical inhibitors of the checkpoint kinases have shown promise in the treatment of cancer, yet their clinical utility may be limited by a lack of molecular biomarkers to identify specific patients most likely to respond to therapy. To this end, we screened 112 known tumor suppressor genes for synthetic lethal interactions with inhibitors of the CHEK1 and CHEK2 checkpoint kinases. We identified eight interactions, including the Replication Factor C (RFC)-related protein RAD17. Clonogenic assays in RAD17 knockdown cell lines identified a substantial shift in sensitivity to checkpoint kinase inhibition (3.5-fold) as compared to RAD17 wild-type. Additional evidence for this interaction was found in a large-scale functional shRNA screen of over 100 genotyped cancer cell lines, in which CHEK1/2 mutant cell lines were unexpectedly sensitive to RAD17 knockdown. This interaction was widely conserved, as we found that RAD17 interacts strongly with checkpoint kinases in the budding yeast Saccharomyces cerevisiae. In the setting of RAD17 knockdown, CHEK1/2 inhibition was found to be synergistic with inhibition of WEE1, another pharmacologically relevant checkpoint kinase. Accumulation of the DNA damage marker γH2AX following chemical inhibition or transient knockdown of CHEK1, CHEK2 or WEE1 was magnified by knockdown of RAD17. Taken together, our data suggest that CHEK1 or WEE1 inhibitors are likely to have greater clinical efficacy in tumors with RAD17 loss-of-function.


DNA damage; RAD17; biomarker; checkpoint kinase inhibitor; synthetic lethal

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