MMB-FOXM1-driven premature mitosis is required for CHK1 inhibitor sensitivity

Abstract

SUMMARY To identify genes whose loss confers resistance to CHK1 inhibitors, we perform genome-wide CRISPR-Cas9 screens in non-small-cell lung cancer (NSCLC) cell lines treated with the CHK1 inhibitor prexasertib (CHK1i). Five of the top six hits of the screens, MYBL2 (B-MYB), LIN54, FOXM1, cyclin A2 (CCNA2), and CDC25B, are cell-cycle-regulated genes that contribute to entry into mitosis. Knockout of MMB-FOXM1 complex components LIN54 and FOXM1 reduce CHK1i-induced DNA replication stress markers and premature mitosis during Late S phase. Activation of a feedback loop between the MMB-FOXM1 complex and CDK1 is required for CHK1i-induced premature mitosis in Late S phase and subsequent replication catastrophe, indicating that dysregulation of the S to M transition is necessary for CHK1 inhibitor sensitivity. These findings provide mechanistic insights into small molecule inhibitors currently studied in clinical trials and provide rationale for combination therapies.

DNMT3A harboring leukemia-associated mutations directs sensitivity to DNA damage at replication forks

“…Similarly, our studies demonstrate whereas the presence of DNMT3A(R882) decreases the sensitivity to DNA torsional stress induced by anthracyclines and possibly other DNA intercalators 13 , it renders the cells more susceptible to the deleterious effects of replication fork stalling. Accentuated replication stress in cells expressing mutant DNMT3A is further supported by previous findings of negatively enriched E2F target and CHEK1-regulated G2/M checkpoint gene sets reported in independent AML cohorts as well as in mice 13,28 , which reflect G1/S cell cycle phase transition rate 29,30,63 and G2/M checkpoint adaptation 64,65 . Accordingly, after low-dose cytarabine exposure (approx.…”

“…Hence, we and others performed DNA methylation analyses 13,[24][25][26][27] and gene expression profiling 13,28 in primary AML samples and in animal models carrying DNMT3A mutations. These studies uncovered gene signatures of altered cell cycle control such as negative enrichment of the CHK1-regulated G2/M checkpoint 29,30 , which may indicate persistent replication stress, in cells expressing mutant DNMT3A 13,28 . Importantly, DNMT3A protein has been detected in direct association with stalled replication forks in cells treated with hydroxyurea 31 .…”

FOXM1: A Multifunctional Oncoprotein and Emerging Therapeutic Target in Ovarian Cancer

“…Extensive in vitro data support a role for FOXM1 in ovarian cancer chemotherapy resistance, including platinum-based drugs, taxanes, and PARPi, all of which are currently used to treat ovarian cancer. Conversely, FOXM1 expression was recently reported to be a predictor of increased efficacy for Chk1 and WEE1 inhibitors, which are in clinical testing for ovarian cancer [ 367 , 368 , 369 ]. It is thus highly relevant to assess FOXM1 as a biomarker for responsiveness to chemotherapeutic agents in current use as well as in clinical trials for ovarian cancer patients.…”

Dual Inhibition of PARP and the Intra-S/G2 Cell Cycle Checkpoints Results in Highly Effective Radiosensitization of HPV-Positive HNSCC Cells

“…Reduction of the radiationinduced G2 arrest can be achieved by inhibition of the ATR/Chk1/ Wee1 axis, as the inhibition of any of these kinases finally counteracts Wee1-mediated inhibitory phosphorylation of cyclin dependent kinase 1 (CDK1), which, in its active state will continue to drive G2-M transition (16,17). Premature mitotic entry and induction of severe replication stress are further therapeutic effects resulting from enhanced CDK1 and CDK2 activity upon inhibition of the ATR/Chk1/Wee1 axis also without irradiation (18)(19)(20).…”