Abstract

Introduction: Screening for synthetic lethality markers has demonstrated that the inhibition of the cell cycle checkpoint kinases WEE1 together with CHK1 drastically affects stability of the cell cycle and induces cell death in rapidly proliferating cells. Exploiting this finding for a possible therapeutic approach has showed efficacy in various solid and hematologic tumors, though not specifically tested in acute lymphoblastic leukemia. Methods: The efficacy of the combination between WEE1 and CHK1 inhibitors in B and T cell precursor acute lymphoblastic leukemia (B/T-ALL) was evaluated in vitro and ex vivo studies. The efficacy of the therapeutic strategy was tested in terms of cytotoxicity, induction of apoptosis, and changes in cell cycle profile and protein expression using B/T-ALL cell lines. In addition, the efficacy of the drug combination was studied in primary B-ALL blasts using clonogenic assays. Results: This study reports, for the first time, the efficacy of the concomitant inhibition of CHK1/CHK2 and WEE1 in ALL cell lines and primary leukemic B-ALL cells using two selective inhibitors: PF-0047736 (CHK1/CHK2 inhibitor) and AZD-1775 (WEE1 inhibitor). We showed strong synergism in the reduction of cell viability, proliferation and induction of apoptosis. The efficacy of the combination was related to the induction of early S-phase arrest and to the induction of DNA damage, ultimately triggering cell death. We reported evidence that the efficacy of the combination treatment is independent from the activation of the p53-p21 pathway. Moreover, gene expression analysis on B-ALL primary samples showed that Chek1 and Wee1 are significantly co-expressed in samples at diagnosis (Pearson r = 0.5770, p = 0.0001) and relapse (Pearson r= 0.8919; p = 0.0001). Finally, the efficacy of the combination was confirmed by the reduction in clonogenic survival of primary leukemic B-ALL cells. Conclusion: Our findings suggest that the combination of CHK1 and WEE1 inhibitors may be a promising therapeutic strategy to be tested in clinical trials for adult ALL.

Highlights

  • Screening for synthetic lethality markers has demonstrated that the inhibition of the cell cycle checkpoint kinases WEE1 together with CHK1 drastically affects stability of the cell cycle and induces cell death in rapidly proliferating cells

  • Damage and compromise DNA repair mechanisms is currently being evaluated in clinical trials in solid tumors (NCT03330847). In this trial cancer patients will be evaluated for the response to AZD1775 in combination with the PARP-1 inhibitor, olaparib

  • The idea of using targeted drug combinations to concurrently induce DNA damage and compromise DNA repair mechanisms is currently being evaluated in clinical trials in solid tumors (NCT03330847)

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Summary

Introduction

Screening for synthetic lethality markers has demonstrated that the inhibition of the cell cycle checkpoint kinases WEE1 together with CHK1 drastically affects stability of the cell cycle and induces cell death in rapidly proliferating cells Exploiting this finding for a possible therapeutic approach has showed efficacy in various solid and hematologic tumors, though not tested in acute lymphoblastic leukemia. For several years different research groups have focused on the biological pathways underlying cancer cell response to DNA damaging therapeutics [2,3]. The inhibition of cell cycle checkpoint regulators, such as CHK1, CHK2 and WEE1 kinases, has become a promising strategy to kill cancer cells mostly by enhancing the toxicity of DNA-damaging agents [4,5,6,7]. It has been reported that the inhibition of CHK1, CHK2 or WEE1, as monotherapy or in combination with DNA damaging agents, reduces cell viability and induces apoptosis in preclinical models of ALL [15,16,17,18,19,20]

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