A high-throughput approach to identify BRCA1-downregulating compounds to enhance PARP inhibitor sensitivity
Erin Sellars,
Margarita Savguira,
Jie Wu,
Sabrina Cancelliere,
Mark Jen,
Rehna Krishnan,
Anne Hakem,
Dalia Barsyte-Lovejoy,
Razqallah Hakem,
Steven A. Narod,
Joanne Kotsopoulos,
Leonardo Salmena
Affiliations
Erin Sellars
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada; Women’s College Research Institute, Women’s College Hospital, Toronto, ON M5S 1B2, Canada
Margarita Savguira
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada
Jie Wu
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada
Sabrina Cancelliere
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada
Mark Jen
Lunenfeld-Tanenbaum Research Institute, Network Biology Collaborative Centre, High-Throughput Screening, Mt. Sinai Hospital, Sinai Health System, Toronto, ON M5G 1X5, Canada
Rehna Krishnan
Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 1L7, Canada
Anne Hakem
Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 1L7, Canada
Dalia Barsyte-Lovejoy
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada; Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada
Razqallah Hakem
Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 1L7, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada
Steven A. Narod
Women’s College Research Institute, Women’s College Hospital, Toronto, ON M5S 1B2, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, ON M5T 3M7, Canada
Joanne Kotsopoulos
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada; Women’s College Research Institute, Women’s College Hospital, Toronto, ON M5S 1B2, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, ON M5T 3M7, Canada
Leonardo Salmena
Department of Pharmacology & Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada; Women’s College Research Institute, Women’s College Hospital, Toronto, ON M5S 1B2, Canada; Corresponding author
Summary: PARP inhibitors (PARPi) are efficacious in BRCA1-null tumors; however, their utility is limited in tumors with functional BRCA1. We hypothesized that pharmacologically reducing BRCA1 protein levels could enhance PARPi effectiveness in BRCA1 wild-type tumors. To identify BRCA1 downregulating agents, we generated reporter cell lines using CRISPR-mediated editing to tag endogenous BRCA1 protein with HiBiT. These reporter lines enable the sensitive measurement of BRCA1 protein levels by luminescence. Validated reporter cells were used in a pilot screen of epigenetic-modifying probes and a larger screen of more than 6,000 compounds. We identified 7 compounds that could downregulate BRCA1-HiBiT expression and synergize with olaparib. Three compounds, N-acetyl-N-acetoxy chlorobenzenesulfonamide (NANAC), A-443654, and CHIR-124, were validated to reduce BRCA1 protein levels and sensitize breast cancer cells to the toxic effects of olaparib. These results suggest that BRCA1-HiBiT reporter cells hold promise in developing agents to improve the clinical utility of PARPi.
