ve-821 and Glioblastoma

ATR is an attractive target in cancer therapy because it signals replication stress and DNA lesions for repair and to S/G2 checkpoints. Cancer-specific defects in the DNA damage response (DDR) may render cancer cells vulnerable to ATR inhibition alone. We determined the cytotoxicity of the ATR inhibitor VE-821 in isogenically matched cells with DDR imbalance. Cell cycle arrest, DNA damage accumulation and repair were determined following VE-821 exposure.Defects in homologous recombination repair (HRR: ATM, BRCA2 and XRCC3) and base excision repair (BER: XRCC1) conferred sensitivity to VE-821. Surprisingly, the loss of different components of the trimeric non-homologous end-joining (NHEJ) protein DNA-PK had opposing effects. Loss of the DNA-binding component, Ku80, caused hypersensitivity to VE-821, but loss of its partner catalytic subunit, DNA-PKcs, did not. Unexpectedly, VE-821 was particularly cytotoxic to human and hamster cells expressing high levels of DNA-PKcs. High DNA-PKcs was associated with replicative stress and activation of the DDR. VE-821 suppressed HRR, determined by RAD51 focus formation, to a greater extent in cells with high DNA-PKcs.Defects in HRR and BER and high DNA-PKcs expression, that are common in cancer, confer sensitivity to ATR inhibitor monotherapy and may be developed as predictive biomarkers for personalised medicine.

Topics: Animals; Antineoplastic Agents; Ataxia Telangiectasia Mutated Proteins; Brain Neoplasms; Cell Line, Tumor; CHO Cells; Computational Biology; Cricetinae; Cricetulus; Databases, Genetic; DNA Damage; DNA Repair; DNA Repair Enzymes; DNA-Activated Protein Kinase; Dose-Response Relationship, Drug; G2 Phase Cell Cycle Checkpoints; Gene Expression Profiling; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; Molecular Targeted Therapy; Nuclear Proteins; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-myc; Pyrazines; Signal Transduction; Sulfones; Time Factors; Transfection