title: Untangling the ATR-CHEK1 network for prognostication, prediction and therapeutic target validation in breast cancer.
abstract: ATR-CHEK1 signalling is critical for genomic stability. ATR-CHEK1 signalling may be deregulated in breast cancer and have prognostic, predictive and therapeutic significance. We investigated ATR, CHEK1 and phosphorylated CHEK1 (Ser345) protein (pCHEK1) levels in 1712 breast cancers. ATR and CHEK1 mRNA expression was evaluated in 1950 breast cancers. Pre-clinically, biological consequences of ATR gene knock down or ATR inhibition by the small molecule inhibitor (VE-821) were investigated in MCF7 and MDA-MB-231 breast cancer cell lines and in non-tumorigenic breast epithelial cells (MCF10A). High ATR and high cytoplasmic pCHEK1 levels were significantly associated with higher tumour stage, higher mitotic index, pleomorphism and lymphovascular invasion. In univariate analyses, high ATR and high cytoplasmic pCHEK1 levels were associated with poor breast cancer specific survival (BCSS). In multivariate analysis, high ATR level remains an independent predictor of adverse outcome. At the mRNA level, high CHEK1 remains associated with aggressive phenotypes including lymph node positivity, high grade, Her-2 overexpression, triple negative, aggressive molecular phenotypes and adverse BCSS. Pre-clinically, CHEK1 phosphorylation at serine(345) following replication stress was impaired in ATR knock down and in VE-821 treated breast cancer cells. Doxycycline inducible knockdown of ATR suppressed growth, which was restored when ATR was re-expressed. Similarly, VE-821 treatment resulted in a dose dependent suppression of cancer cell growth and survival (MCF7 and MDA-MB-231) but was less toxic in non-tumorigenic breast epithelial cells (MCF10A). We provide evidence that ATR and CHEK1 are promising biomarkers and rational drug targets for personalized therapy in breast cancer.
authors.affiliation: Department of Oncology, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Tarek M A
authors.initials: TM
authors.lastname: Abdel-Fatah
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors.forename: Fiona K
authors.initials: FK
authors.lastname: Middleton
authors.affiliation: Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Arvind
authors.initials: A
authors.lastname: Arora
authors.affiliation: School of Science and Technology, Nottingham Trent University, Clifton Campus, Nottingham NG11 8NS, UK.
authors.forename: Devika
authors.initials: D
authors.lastname: Agarwal
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.affiliation: Department of Oncology, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Moseley
authors.affiliation: Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Christina
authors.initials: C
authors.lastname: Perry
authors.affiliation: Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Doherty
authors.affiliation: Department of Oncology, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Chan
authors.affiliation: Department of Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Green
authors.affiliation: Department of Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Emad
authors.initials: E
authors.lastname: Rakha
authors.affiliation: School of Science and Technology, Nottingham Trent University, Clifton Campus, Nottingham NG11 8NS, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Ball
authors.affiliation: Department of Pathology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK.
authors.forename: Ian O
authors.initials: IO
authors.lastname: Ellis
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Curtin
authors.affiliation: Department of Oncology, Nottingham University Hospitals, Nottingham NG5 1PB, UK; Academic Unit of Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham NG5 1PB, UK. Electronic address: srinivasan.madhusudan@nottingham.ac.uk.
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Madhusudan
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000071877:Checkpoint Kinase 1; D015331:Cohort Studies; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D053208:Kaplan-Meier Estimate; D058990:Molecular Targeted Therapy; D015999:Multivariate Analysis; D009361:Neoplasm Invasiveness; D010641:Phenotype; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011379:Prognosis; D011494:Protein Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D013312:Stress, Physiological
chemical_list: D012333:RNA, Messenger; D010768:Phosphoserine; D011494:Protein Kinases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1
keywords: ATR; Biomarker; Breast cancer; CHEK1