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ATR, CHK1 and WEE1 inhibitors cause homologous recombination repair deficiency to induce synthetic lethality with PARP inhibitors

Lookup NU author(s): Hannah Smith, Dr Elaine WillmoreORCiD, Dr Lisa PrendergastORCiD, Professor Nicola CurtinORCiD

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Abstract

© The Author(s) 2024.Purpose: PARP inhibitors (PARPi) are effective in homologous recombination repair (HRR) defective (HRD) cancers. To (re)sensitise HRR proficient (HRP) tumours to PARPi combinations with other drugs are being explored. Our aim was to determine the mechanism underpinning the sensitisation to PARPi by inhibitors of cell cycle checkpoint kinases ATR, CHK1 and WEE1. Experimental design: A panel of HRD and HRP cells (including matched BRCA1 or 2 mutant and corrected pairs) and ovarian cancer ascites cells were used. Rucaparib (PARPi) induced replication stress (RS) and HRR (immunofluorescence microscopy for γH2AX and RAD51 foci, respectively), cell cycle changes (flow cytometry), activation of ATR, CHK1 and WEE1 (Western Blot for pCHK1S345, pCHK1S296 and pCDK1Y15, respectively) and cytotoxicity (colony formation assay) was determined, followed by investigations of the impact on all of these parameters by inhibitors of ATR (VE-821, 1 µM), CHK1 (PF-477736, 50 nM) and WEE1 (MK-1775, 100 nM). Results: Rucaparib induced RS (3 to10-fold), S-phase accumulation (2-fold) and ATR, CHK1 and WEE1 activation (up to 3-fold), and VE-821, PF-477736 and MK-1775 inhibited their targets and abrogated these rucaparib-induced cell cycle changes in HRP and HRD cells. Rucaparib activated HRR in HRP cells only and was (60-1,000x) more cytotoxic to HRD cells. VE-821, PF-477736 and MK-1775 blocked HRR and sensitised HRP but not HRD cells and primary ovarian ascites to rucaparib. Conclusions: Our data indicate that, rather than acting via abrogation of cell cycle checkpoints, ATR, CHK1 and WEE1 inhibitors cause an HRD phenotype and hence “induced synthetic lethality” with PARPi.

Publication metadata

Author(s): Smith HL, Willmore E, Prendergast L, Curtin NJ

Publication type: Article

Publication status: Published

Journal: British Journal of Cancer

Year: 2024

Pages: epub ahead of print

Online publication date: 04/07/2024

Acceptance date: 31/05/2024

Date deposited: 15/07/2024

ISSN (print): 0007-0920

ISSN (electronic): 1532-1827

Publisher: Springer Nature

URL: https://doi.org/10.1038/s41416-024-02745-0

DOI: 10.1038/s41416-024-02745-0

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