Genome-Protective Topoisomerase 2a-Dependent G2 Arrest Requires p53 in hTERT-Positive Cancer Cells

Author:

Lockwood Nicola1,Martini Silvia1,Lopez-Pardo Ainara1ORCID,Deiss Katharina1,Segeren Hendrika A.1ORCID,Semple Robert K.2,Collins Ian3ORCID,Repana Dimitra45,Cobbaut Mathias1ORCID,Soliman Tanya6ORCID,Ciccarelli Francesca45,Parker Peter J.15ORCID

Affiliation:

1. Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK.

2. Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK.

3. Division of Cancer Therapeutics, The Institute of Cancer Research, London, UK.

4. Cancer Systems Biology Laboratory, The Francis Crick Institute, London, UK.

5. School of Cancer and Pharmaceutical Sciences King's College London, New Hunt's House, Guy's Campus, London, UK.

6. Barts Cancer Institute, Queen Mary University London, Charterhouse Square, London, UK.

Abstract

Abstract Topoisomerase 2a (Topo2a)-dependent G2 arrest engenders faithful segregation of sister chromatids, yet in certain tumor cell lines where this arrest is dysfunctional, a PKCε-dependent failsafe pathway can be triggered. Here we elaborate on recent advances in understanding the underlying mechanisms associated with this G2 arrest by determining that p53–p21 signaling is essential for efficient arrest in cell lines, in patient-derived cells, and in colorectal cancer organoids. Regulation of this p53 axis required the SMC5/6 complex, which is distinct from the p53 pathways observed in the DNA damage response. Topo2a inhibition specifically during S phase did not trigger G2 arrest despite affecting completion of DNA replication. Moreover, in cancer cells reliant upon the alternative lengthening of telomeres (ALT) mechanism, a distinct form of Topo2a-dependent, p53-independent G2 arrest was found to be mediated by BLM and Chk1. Importantly, the previously described PKCε-dependent mitotic failsafe was engaged in hTERT-positive cells when Topo2a-dependent G2 arrest was dysfunctional and where p53 was absent, but not in cells dependent on the ALT mechanism. In PKCε knockout mice, p53 deletion elicited tumors were less aggressive than in PKCε-replete animals and exhibited a distinct pattern of chromosomal rearrangements. This evidence suggests the potential of exploiting synthetic lethality in arrest-defective hTERT-positive tumors through PKCε-directed therapeutic intervention. Significance: The identification of a requirement for p53 in stringent Topo2a-dependent G2 arrest and engagement of PKCε failsafe pathways in arrest-defective hTERT-positive cells provides a therapeutic opportunity to induce selective synthetic lethality.

Funder

Cancer Research UK

UK Medical Research Council

Wellcome Trust

Publisher

American Association for Cancer Research (AACR)

Subject

Cancer Research,Oncology

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