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Combined Targeting of G9a and Checkpoint Kinase 1 Synergistically Inhibits Pancreatic Cancer Cell Growth by Replication Fork Collapse. Mol Cancer Res 2020 03;18(3):448-462

Date

12/12/2019

Pubmed ID

31822519

Pubmed Central ID

PMC7056528

DOI

10.1158/1541-7786.MCR-19-0490

Scopus ID

2-s2.0-85081130002   8 Citations

Abstract

Because of its dismal outcome, pancreatic ductal adenocarcinoma (PDAC) remains a therapeutic challenge making the testing of new pharmacologic tools a goal of paramount importance. Here, we developed a rational approach for inhibiting PDAC growth based on leveraging cell-cycle arrest of malignant cells at a phase that shows increased sensitivity to distinct epigenomic inhibitors. Specifically, we simultaneously inhibited checkpoint kinase 1 (Chk1) by prexasertib and the G9a histone methyltransferase with BRD4770, thereby targeting two key pathways for replication fork stability. Methodologically, the antitumor effects and molecular mechanisms of the combination were assessed by an extensive battery of assays, utilizing cell lines and patient-derived cells as well as 3D spheroids and xenografts. We find that the prexasertib-BRD4770 combination displays a synergistic effect on replication-associated phenomena, including cell growth, DNA synthesis, cell-cycle progression at S phase, and DNA damage signaling, ultimately leading to a highly efficient induction of cell death. Moreover, cellular and molecular data reveal that the synergistic effect of these pathways can be explained, at least in large part, by the convergence of both Chk1 and G9a functions at the level of the ATR-RPA-checkpoint pathway, which is operational during replication stress. Thus, targeting the epigenetic regulator G9a, which is necessary for replication fork stability, combined with inhibition of the DNA damage checkpoint, offers a novel approach for controlling PDAC growth through replication catastrophe. IMPLICATIONS: This study offers an improved, context-dependent, paradigm for the use of epigenomic inhibitors and provides mechanistic insight into their potential therapeutic use against PDAC.

Author List

Urrutia G, Salmonson A, Toro-Zapata J, de Assuncao TM, Mathison A, Dusetti N, Iovanna J, Urrutia R, Lomberk G

Authors

Gwen Lomberk PhD Professor in the Surgery department at Medical College of Wisconsin
Angela Mathison PhD Assistant Professor in the Surgery department at Medical College of Wisconsin
Raul A. Urrutia MD Center Director, Professor in the Surgery department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Antineoplastic Combined Chemotherapy Protocols
Benzamides
Benzimidazoles
Carcinoma, Pancreatic Ductal
Checkpoint Kinase 1
DNA Replication
Drug Synergism
Enzyme Inhibitors
Female
Histocompatibility Antigens
Histone-Lysine N-Methyltransferase
Humans
Mice
Mice, Nude
Molecular Targeted Therapy
Pancreatic Neoplasms
Pyrazines
Pyrazoles
Random Allocation
Xenograft Model Antitumor Assays