Parallel functional genetic and compound screens identify WEE1 inhibition as a therapeutic strategy for cancers with defects in Fanconi Anaemia and HR pathways


Year:

Session type:

Marieke Aarts1, Ilirjana Bajrami1, Richard Elliott1, Christopher Lord1, Alan Ashworth1, Nicholas Turner1,2
1Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK, 2Breast Unit, Royal Marsden Hospital, London, UK

Background

WEE1 kinase is a critical regulator of mitotic entry through inhibitory phosphorylation of CDK1. We have previously shown that WEE1 inhibitors synergized with DNA damaging agents that arrested cells in S-phase, triggering direct mitotic entry without completing DNA synthesis, resulting in catastrophic chromosome fragmentation and apoptosis.

The aim of this study was to understand how forced mitotic entry could be best exploited for cancer therapy, and to identify novel determinants of sensitivity to WEE1 inhibition.

Method

We performed a functional genetic screen with an siRNA library targeting the kinome, phosphatome, DNA repair and tumour suppressor genes to identify genes and pathways whose inhibition synergized with WEE1 inhibitor MK-1775. In parallel, a library of drugs and kinase inhibitors was screened. The underlying mechanism of sensitivity or resistance was studied for selected hits.

Results

Drug and siRNA screening identified synergy between WEE1 and CHK1 inhibition, and WEE1 inhibition and MYT1 depletion, with the combinations forcing S-phase cells directly into mitosis. Silencing of multiple DNA helicases and components of the Fanconi anaemia (FA) and homologous recombination (HR) pathways sensitised to MK-1775, which was accompanied by increased gamma H2AX induction in S-phase and premature mitotic entry.

Conclusion

Through parallel compound and functional genetic screens we have identified novel combinations that induce mitotic entry of S-phase cells in the absence of chemotherapy. Our results suggest that cancers with defects in FA and HR pathways may be targeted by WEE1 inhibition, providing a basis for a novel synthetic lethal strategy for cancers harbouring FA/HR defects.