Differential Effects of Combined ATR/WEE1 Inhibition in Cancer Cells.

Gro Elise Rødland,Randi G. Syljuåsen,Tine T. H. Raabe,Grete Hasvold,Mrinal Joel,Sissel Hauge,Lilli T. E. Bay

doi:10.3390/cancers13153790

Abstract

Simple SummaryCancer cells often show elevated replication stress and loss of cell cycle checkpoints. The ataxia telangiectasia and Rad3-related (ATR) and WEE1 kinases play roles in protecting cancer cells from high replication stress and in regulating the remaining cell cycle checkpoints. Inhibitors of ATR or WEE1 therefore have the potential to selectively kill cancer cells and are currently being tested in clinical trials. However, more studies are needed to understand how these inhibitors work in various types of cancer and to find the most effective ways of using them. Here, we have explored whether simultaneous treatment with ATR and WEE1 inhibitors is a promising approach. Effects were investigated in cell lines from osteosarcoma and lung cancer. We expect our results to be of importance for future treatment strategies with these inhibitors.Inhibitors of WEE1 and ATR kinases are considered promising for cancer treatment, either as monotherapy or in combination with chemo- or radiotherapy. Here, we addressed whether simultaneous inhibition of WEE1 and ATR might be advantageous. Effects of the WEE1 inhibitor MK1775 and ATR inhibitor VE822 were investigated in U2OS osteosarcoma cells and in four lung cancer cell lines, H460, A549, H1975, and SW900, with different sensitivities to the WEE1 inhibitor. Despite the differences in cytotoxic effects, the WEE1 inhibitor reduced the inhibitory phosphorylation of CDK, leading to increased CDK activity accompanied by ATR activation in all cell lines. However, combining ATR inhibition with WEE1 inhibition could not fully compensate for cell resistance to the WEE1 inhibitor and reduced cell viability to a variable extent. The decreased cell viability upon the combined treatment correlated with a synergistic induction of DNA damage in S-phase in U2OS cells but not in the lung cancer cells. Moreover, less synergy was found between ATR and WEE1 inhibitors upon co-treatment with radiation, suggesting that single inhibitors may be preferable together with radiotherapy. Altogether, our results support that combining WEE1 and ATR inhibitors may be beneficial for cancer treatment in some cases, but also highlight that the effects vary between cancer cell lines.

Highlights

The ataxia telangiectasia and Rad3-related (ATR) and WEE1 kinases are two key players in DNA damage and replication stress response, and both kinases are considered promising targets for cancer treatment [1]
In a previous screen identifying drugs that synergized with the WEE1 inhibitor MK1775 to cause DNA damage in S-phase, we found two CHK1 inhibitors (AZD7762 and LY2603618) to be among the top hits [12]
Since CHK1 is a downstream target of ATR, and ATR is the apical kinase in the replication stress response, we hypothesized that combining MK1775 with an inhibitor of ATR would give a response similar to, or even better than, the combined WEE1/CHK1 inhibition

Summary

Introduction

The ataxia telangiectasia and Rad3-related (ATR) and WEE1 kinases are two key players in DNA damage and replication stress response, and both kinases are considered promising targets for cancer treatment [1]. ATR leads to cell cycle checkpoint arrest in S- and G2-phases, DNA damage repair, replication fork protection, and reduced origin firing [2]. Cells with reduced ATR function will have compromised checkpoints and increased sensitivity to DNA damage and replication stress [3,4]. WEE1 inhibition causes premature mitotic entry and abrogation of the DNA-damage-induced G2 checkpoint, often resulting in mitotic catastrophe [9]. S-phase WEE1 inhibition causes unscheduled firing of replication origins and activates endonucleases such as MUS81, which can lead to massive DNA damage and replication catastrophe [5,10,11,12]

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Results

Conclusion