Isogenic FBXW7-knockout cervical tumor organoids recapitulate AZD6738 sensitivity. A, Schematic of generation of patient-derived cervical tumor organoid cultures. B, Imaging of M45 cervical tumor organoid isolation over 7 days, scale bar 200 µm, arrows indicate actively expanding organoids. C, Representative Z-stack images of a single organoid stained with DNA stain (DAPI) and marker of proliferation (Ki67), 50 µm scale bar. D, Schematic of infection and selection of isogenic cervical tumor organoids. E, Representative Western blot analysis of FBXW7 knockout in isogenic organoids. F, Western blot analysis of pCHK1 (S345) in indicated organoids, representative of three independent replicates. G, Dose–response assay in organoids treated with AZD6738, over 7 days, scale bars 200 µm. Data are representative of three independent replicates. H, Quantification of cell viability relative to untreated cells in three independent replicates of organoid dose–response assay, mean ± SD, two-way ANOVA.
Funding
Gouvernement du Canada | Canadian Institutes of Health Research (IRSC)
CCS | Canadian Cancer Society Research Institute (CCSRI)
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.
