The single greatest challenge in the treatment of cancer has always been to uncover therapeutic agents that eliminate only tumor cells while sparing normal cells. The concept of """"""""synthetic lethality"""""""" has much to offer here. Given the complexity of cellular networks, the best approach to uncovering novel synthetic lethal partners is from genetic screens. We recently identified the DEXH helicase, DHX9, as a synthetic lethal target from an RNA Interference screen. DHX9 is a multifunctional protein with roles in transcriptional regulation, mRNA translation, and miRNA processing. Our previous work with the RNA helicase, eIF4A, has demonstrated that selective pharmacological targeting of this class of proteins is achievable. The goal of this project is to develop HTS assays that will allow discovery of small molecule inhibitors of DHX9, which in turn, can be used in cell and animal models to examine the consequences of inhibition of this protein on cancer cell survival. We will develop a fluorescence-based, quantitative high-throughput assay to monitor the helicase activity of DHX9. In addition, an orthogonal counterscreen and secondary assay will be developed to allow triage of initial primary hits. Biochemical assays that probe the RNA helicase, RNA binding, and NTPase activities of DHX9 will be used to classify compounds based on mode of action, to provide an appropriate benchmark for specificity, and to obtain preliminary structure-activity relationships (SAR) insight. A set of cell-based assays will be developed to evaluate the effects of small molecule inhibitors on DHX9- dependent translation and on synthetic lethal relationships for triggering cancer cell death.

Public Health Relevance

Cancer cells often become resistant to chemotherapy by activating programs that block cell death. We have recently found that inhibition of the RNA helicase DHX9 can reverse this situation in certain cases. This project aims to develop high throughput screening assays that can be used to identify chemical inhibitors of DHX9 that will have the potential to overcome, and provide insight into, drug resistance in certain cancer settings.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Drug Discovery and Molecular Pharmacology Study Section (DMP)
Program Officer
Fu, Yali
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Mcgill University
Zip Code
H3 0-G4
Lee, Teresa; Pelletier, Jerry (2017) Dependence of p53-deficient cells on the DHX9 DExH-box helicase. Oncotarget 8:30908-30921
Lee, T; Paquet, M; Larsson, O et al. (2016) Tumor cell survival dependence on the DHX9 DExH-box helicase. Oncogene 35:5093-105
Cencic, Regina; Senechal, Patrick; Pelletier, Jerry (2015) Establishment of a Primary Screening Assay for the DHX9 Helicase. Comb Chem High Throughput Screen 18:855-61
Chu, Jennifer; Pelletier, Jerry (2015) Targeting the eIF4A RNA helicase as an anti-neoplastic approach. Biochim Biophys Acta 1849:781-91
Lee, Teresa; Di Paola, Domenic; Malina, Abba et al. (2014) Suppression of the DHX9 helicase induces premature senescence in human diploid fibroblasts in a p53-dependent manner. J Biol Chem 289:22798-814
Cencic, Regina; Pelletier, Jerry (2013) Throwing a monkey wrench in the motor: targeting DExH/D box proteins with small molecule inhibitors. Biochim Biophys Acta 1829:894-903