H2AX phosphorylation screen of cells from radiosensitive cancer patients reveals a novel DNA double-strand break repair cellular phenotype

• Published in: British journal of cancer 2010-05, Vol.102 (10), p.1511-1518
• Main Authors: Vasireddy, R S, Sprung, C N, Cempaka, N L, Chao, M, McKay, M J
• Format: Article
• Language: English
• Subjects: 631/208/721; 631/337/1427/2122; 692/699/67; 692/699/67/1059/485; Adult; Aged; Aged, 80 and over; Biological and medical sciences; Biomarkers, Tumor - genetics; Biomedicine; Cancer Research; Cancer therapies; Cell cycle; Cell death; Cell Line, Tumor; DNA - metabolism; DNA Breaks, Double-Stranded - radiation effects; DNA damage; DNA Repair; Drug Resistance; Epidemiology; Female; Fluorescent Antibody Technique; Genetic Techniques; Histones - metabolism; Histones - radiation effects; Humans; Kinases; Male; Medical research; Medical sciences; Middle Aged; Molecular Diagnostics; Molecular Medicine; Mutation; Neoplasms - genetics; Neoplasms - radiotherapy; Oncology; Patients; Phenotype; Phosphorylation; Proteins; Radiation therapy; Radiation Tolerance - genetics; Tumors; Yeast
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/sj.bjc.6605666

Background: About 1–5% of cancer patients suffer from significant normal tissue reactions as a result of radiotherapy (RT). It is not possible at this time to predict how most patients’ normal tissues will respond to RT. DNA repair dysfunction is implicated in sensitivity to RT particularly in genes that mediate the repair of DNA double-strand breaks (DSBs). Phosphorylation of histone H2AX (phosphorylated molecules are known as γ H2AX) occurs rapidly in response to DNA DSBs, and, among its other roles, contributes to repair protein recruitment to these damaged sites. Mammalian cell lines have also been crucial in facilitating the successful cloning of many DNA DSB repair genes; yet, very few mutant cell lines exist for non-syndromic clinical radiosensitivity (RS). Methods: Here, we survey DNA DSB induction and repair in whole cells from RS patients, as revealed by γ H2AX foci assays, as potential predictive markers of clinical radiation response. Results: With one exception, both DNA focus induction and repair in cell lines from RS patients were comparable with controls. Using γ H2AX foci assays, we identified a RS cancer patient cell line with a novel ionising radiation-induced DNA DSB repair defect; these data were confirmed by an independent DNA DSB repair assay. Conclusion: γ H2AX focus measurement has limited scope as a pre-RT predictive assay in lymphoblast cell lines from RT patients; however, the assay can successfully identify novel DNA DSB repair-defective patient cell lines, thus potentially facilitating the discovery of novel constitutional contributions to clinical RS.