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Complete loss of ATM function augments replication catastrophe induced by ATR inhibition and gemcitabine in pancreatic cancer models.

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Wallez, Yann 
Johnson, Timothy Isaac 
Bernaldo de Quirós Fernández, Sandra 
Durant, Stephen T 


BACKGROUND: Personalised medicine strategies may improve outcomes in pancreatic ductal adenocarcinoma (PDAC), but validation of predictive biomarkers is required. Having developed a clinical trial to assess the ATR inhibitor, AZD6738, in combination with gemcitabine (ATRi/gem), we investigated ATM loss as a predictive biomarker of response to ATRi/gem in PDAC. METHODS: Through kinase inhibition, siRNA depletion and CRISPR knockout of ATM, we assessed how ATM targeting affected the sensitivity of PDAC cells to ATRi/gem. Using flow cytometry, immunofluorescence and immunoblotting, we investigated how ATRi/gem synergise in ATM-proficient and ATM-deficient cells, before assessing the impact of ATM loss on ATRi/gem sensitivity in vivo. RESULTS: Complete loss of ATM function (through pharmacological inhibition or CRISPR knockout), but not siRNA depletion, sensitised to ATRi/gem. In ATM-deficient cells, ATRi/gem-induced replication catastrophe was augmented, while phospho-Chk2-T68 and phospho-KAP1-S824 persisted via DNA-PK activity. ATRi/gem caused growth delay in ATM-WT xenografts in NSG mice and induced regression in ATM-KO xenografts. CONCLUSIONS: ATM loss augments replication catastrophe-mediated cell death induced by ATRi/gem and may predict clinical responsiveness to this combination. ATM status should be carefully assessed in tumours from patients with PDAC, since distinction between ATM-low and ATM-null could be critical in maximising the success of clinical trials using ATM expression as a predictive biomarker.



Animals, Antineoplastic Combined Chemotherapy Protocols, Ataxia Telangiectasia Mutated Proteins, Carcinoma, Pancreatic Ductal, Cell Line, Tumor, Cell Proliferation, Deoxycytidine, Drug Synergism, Female, Gene Knockout Techniques, Humans, Indoles, Mice, Mice, 129 Strain, Mice, Inbred C57BL, Morpholines, Pancreatic Neoplasms, Pyridines, Pyrimidines, Quinolines, RNA, Small Interfering, Sulfonamides, Sulfoxides, Xenograft Model Antitumor Assays, Gemcitabine

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Br J Cancer

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Springer Science and Business Media LLC


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Pancreatic Cancer UK (FutureLeaders)
Cancer Research UK (C14303/A17197)
Cancer Research UK (C9545/A29580_do not transfer)
Cancer Research UK (A25238)
Cancer Research UK (15678)
Pancreatic Cancer UK (FLF2015_03_Cambridge)
As well as CRUK grants, Pancreatic Cancer UK provided funding, grant RG81962.