DNA Damage Response Inhibitor Combinations Exert Synergistic Antitumor Activity in Aggressive B-Cell Lymphomas

Valentina Restelli,Filippo Spriano,Rosaria Chilà,Laura Carrassa,Micaela Vagni,Francesco Bertoni,Monica Lupi,Chiara Tarantelli,Eugenio Gaudio,Giovanna Damia

doi:10.1158/1535-7163.mct-18-0919

Abstract

The DNA damage response (DDR) kinases ATR, Chk1, and Wee1 play vital roles in the response to replication stress and in maintaining cancer genomic stability. Inhibitors of these kinases are currently under clinical investigation. Mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL) are aggressive lymphomas whose clinical outcome is still largely unsatisfactory. These cell lymphoma subtypes are highly dependent on both Chk1 and Wee1 for survival. We investigated the activity of the ATR inhibitor AZD6738 as single agent and in combination with either Chk1 (AZD6738) or Wee1 (AZD1775) inhibitors in several preclinical models of MCL and DLBCL. This study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination, and validation experiments on in vivo models. Cellular and molecular mechanisms of the observed synergistic effect as well as pharmacodynamic analysis of in vivo samples were studied. AZD6738 exerted a strong synergistic cytotoxic effect in combination with both AZD7762 and AZD1775 in the 2 lymphoma subtypes regardless of their TP53, MYC, and ATM mutational status. These DDR inhibitor combinations, similarly to the Chk1/Wee1 inhibitor combination, caused a marked S-phase delay, with an increase in cyclin-dependent kinases (CDK) activity, increased DNA damage, and decreases in Wee1, MYC, and RRM2 protein levels. The synergistic in vitro activity translated to striking in vivo antitumor activity. DDR-DDR inhibitor combinations could potentially offer promising novel therapeutic strategies for patients with B-cell lymphoma.

Highlights

The DNA damage response (DDR) kinases ATR, Chk1, and Wee1 are required during normal S phase to avoid deleterious DNA breakage, and to maintain cancer cell survival under replication stress (RS; ref. 1)
As our recent data showed a dependence of Mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL) on Chk1 and Wee1 for survival [9, 11] and ATR inhibitors are strongly active in experimental systems with high oncogenic replicative stress [18, 19], we investigated the cytotoxic effect of the ATR inhibitor AZD6738 as single agent and in combination with the Chk1 inhibitor AZD7762 and the Wee1 inhibitor AZD1775
We investigated the cytotoxic effect of AZD6738 in a large panel of lymphoma cell lines: 36 mature B-cell lymphoma cell lines comprising 10 MCL and 26 DLBCL cell lines [7 activated B-cell (ABC)-DLBCL and 19 germinal center B (GCB)-DLBCL], treating them with increasing doses of the ATR inhibitor AZD6738, for 72 hours

Summary

Introduction

The DNA damage response (DDR) kinases ATR, Chk, and Wee are required during normal S phase to avoid deleterious DNA breakage, and to maintain cancer cell survival under replication stress (RS; ref. 1). The DNA damage response (DDR) kinases ATR, Chk, and Wee are required during normal S phase to avoid deleterious DNA breakage, and to maintain cancer cell survival under replication stress RS may be caused by improper control of replication initiation, associated with molecular features very common in cancer The ATR kinase is activated by the ssDNA generated during RS, phosphorylates CHK1, and activates the S-phase checkpoint, preventing the collapse of the replication. Note: Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

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