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posted on 2023-12-21, 14:20 authored by Siobhan O'Brien, Tajinder Ubhi, Lucie Wolf, Krishna Gandhi, Sichun Lin, Naz Chaudary, Neesha C. Dhani, Michael Milosevic, Grant W. Brown, Stephane Angers Isogenic genome-wide screen identifies DNA repair genes essential following FBXW7-loss. A, Schematic of genome-wide CRISPR screens in FBXW7−/− and wild-type cells. B, Rank order plot summarizing the results of genome-wide screens highlighting the identification of various DNA damage response genes as selectively essential in FBXW7−/− HPAF-II cells. BF = Bayes factor, a measure of gene fitness defects upon perturbation. C, Western blot analysis of pCHK1 (S345) identifies increased levels of replication stress in FBXW7−/− compared with parental wild-type HPAF-II cells. Representative images of three independent replicate experiments. D, Quantification of pCHK1 (S345)/CHK1 in HPAF-II wild-type and FBXW7−/− cells from C, n = 3, Students t test. E, Dot plots of two-dimensional cell-cycle flow cytometry assessing DNA content and EdU in wild-type and FBXW7−/− HPAF-II cells. Representative images of three replicate experiments. F, Quantification of percent of cells EdU+ cells in D, n = 3, Students t test. G, Quantification of mean fluorescent intensity (MFI) of EdU+ cells from D, n = 3, Students t test.
Funding
Gouvernement du Canada | Canadian Institutes of Health Research (IRSC)
CCS | Canadian Cancer Society Research Institute (CCSRI)
History
ARTICLE ABSTRACT
FBXW7 is a commonly mutated tumor suppressor gene that functions to regulate numerous oncogenes involved in cell-cycle regulation. Genome-wide CRISPR fitness screens identified a signature of DNA repair and DNA damage response genes as required for the growth of FBXW7-knockout cells. Guided by these findings, we show that FBXW7-mutant cells have high levels of replication stress, which results in a genotype-specific vulnerability to inhibition of the ATR signaling pathway, as these mutant cells become heavily reliant on a robust S–G2 checkpoint. ATR inhibition induces an accelerated S-phase, leading to mitotic catastrophe and cell death caused by the high replication stress present in FBXW7−/− cells. In addition, we provide evidence in cell and organoid studies, and mining of publicly available high-throughput drug screening efforts, that this genotype-specific vulnerability extends to multiple types of cancer, providing a rational means of identifying responsive patients for targeted therapy.
We have elucidated the synthetic lethal interactions between FBXW7 mutation and DNA damage response genes, and highlighted the potential of ATR inhibitors as targeted therapies for cancers harboring FBXW7 alterations.
