Identification of small molecule inhibitors of ERCC1-XPF that inhibit DNA repair and potentiate cisplatin efficacy in cancer cells
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Sanjeevani Arora1, Joshua Heyza2, Hao Zhang2, Vivian Kalman-Maltese1, Kristin Tillison1, Ashley M. Floyd2, Elaine M. Chalfin1, Gerold Bepler2, Steve M. Patrick2
1Department of Biochemistry & Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, USA
2Department of Oncology, Karmanos Cancer Institute, Wayne State University, Detroit, MI, USA
Steve M. Patrick, email: [email protected]
Keywords: ERCC1-XPF, cisplatin, chemoresistance, DNA repair inhibitor, high-throughput screen
Received: April 28, 2016 Accepted: September 02, 2016 Published: September 16, 2016
ERCC1-XPF heterodimer is a 5′-3′ structure-specific endonuclease which is essential in multiple DNA repair pathways in mammalian cells. ERCC1-XPF (ERCC1-ERCC4) repairs cisplatin-DNA intrastrand adducts and interstrand crosslinks and its specific inhibition has been shown to enhance cisplatin cytotoxicity in cancer cells. In this study, we describe a high throughput screen (HTS) used to identify small molecules that inhibit the endonuclease activity of ERCC1-XPF. Primary screens identified two compounds that inhibit ERCC1-XPF activity in the nanomolar range. These compounds were validated in secondary screens against two other non-related endonucleases to ensure specificity. Results from these screens were validated using an in vitro gel-based nuclease assay. Electrophoretic mobility shift assays (EMSAs) further show that these compounds do not inhibit the binding of purified ERCC1-XPF to DNA. Next, in lung cancer cells these compounds potentiated cisplatin cytotoxicity and inhibited DNA repair. Structure activity relationship (SAR) studies identified related compounds for one of the original Hits, which also potentiated cisplatin cytotoxicity in cancer cells. Excitingly, dosing with NSC16168 compound potentiated cisplatin antitumor activity in a lung cancer xenograft model. Further development of ERCC1-XPF DNA repair inhibitors is expected to sensitize cancer cells to DNA damage-based chemotherapy.
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