title: DNA repair foci and late apoptosis/necrosis in peripheral blood lymphocytes of breast cancer patients undergoing radiotherapy.
abstract: OBJECTIVE
  Double-strand breaks (DSB) repair and apoptosis are assumed to be key factors in the determination of individual variability in response to radiation treatment. In this study we investigated tumor protein p53 (TP53) binding protein 1 (53BP1) and phosphorylated histone 2A family member X (γH2AX) foci, γH2AX pan-staining and late apoptosis/necrosis (LAN) in lymphocytes from breast cancer (BC) patients undergoing radiotherapy.
  
  
  METHODS
  BC patients were subjected to local radiotherapy with fractionated doses using linear accelerator. Adverse reactions of patients were classified according to the Radiation Therapy Oncology Group (RTOG)/European Organization for Research and Treatment of Cancer (EORTC) criteria. Blood samples were collected before treatment, at various time-points during and after radiotherapy. Residual 53BP1 and γH2AX foci, γH2AX pan-staining were analyzed in peripheral blood lymphocytes (PBL) using the Metafer system and confocal laser scanning microscopy. LAN cells were counted by the trypan blue (TB) exclusion assay. Statistical analysis was performed using Mann-Whitney test, Spearman rank correlation test and analysis of covariance (ANCOVA).
  
  
  RESULTS
  No statistically significant changes were observed in the levels of γH2AX foci during radiotherapy. In contrast, radiation-induced residual 53BP1 were detected already after the first fraction. Increased individual variability in the 53BP1 focus formation was observed during treatment. The background level of DNA repair foci and its individual variability in response to radiotherapy decreased after the end of radiotherapy indicating successful removal of DNA-damaging effects. A correlation between stage of cancer and 53BP1 focus formation was established which suggests the prognostic value of this test. We show that the fraction of LAN cells negatively correlates with the level of 53BP1 and positively correlates with individual radiosensitivity. Only weak correlation was observed between γH2AX pan-staining and LAN cells. Due to large interindividual variability, both in vivo assays, LAN and focus formation, have shown relatively low predictive power at the individual level.
  
  
  CONCLUSIONS
  It is likely that radiosensitive patients have less efficient mechanisms of elimination of apoptotic cells with DNA damage resulting in accumulation of LAN cells and facilitating adverse reactions. Our data suggested that the grade of adverse reaction may positively correlate with LAN cells in PBL before and during radiotherapy.
authors.affiliation: a Laboratory of Radiobiology , Cancer Research Institute, Slovak Academy of Sciences , Bratislava , Slovakia.
authors.forename: Eva
authors.initials: E
authors.lastname: Marková
authors.affiliation: a Laboratory of Radiobiology , Cancer Research Institute, Slovak Academy of Sciences , Bratislava , Slovakia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Somsedíková
authors.affiliation: a Laboratory of Radiobiology , Cancer Research Institute, Slovak Academy of Sciences , Bratislava , Slovakia.|c Laboratory of Cytogenetics , Institute of Medical Genetics , Tomsk , Russia.
authors.forename: Stanislav
authors.initials: S
authors.lastname: Vasilyev
authors.affiliation: b Department of Radiation Oncology , Radiological Centrum, National Cancer Institute , Bratislava , Slovakia.
authors.forename: Margita
authors.initials: M
authors.lastname: Pobijaková
authors.affiliation: b Department of Radiation Oncology , Radiological Centrum, National Cancer Institute , Bratislava , Slovakia.
authors.forename: Alica
authors.initials: A
authors.lastname: Lacková
authors.affiliation: b Department of Radiation Oncology , Radiological Centrum, National Cancer Institute , Bratislava , Slovakia.
authors.forename: Pavol
authors.initials: P
authors.lastname: Lukačko
authors.affiliation: a Laboratory of Radiobiology , Cancer Research Institute, Slovak Academy of Sciences , Bratislava , Slovakia.
authors.forename: Igor
authors.initials: I
authors.lastname: Belyaev
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000528:radiation effects*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy*; D004260:DNA Repair / Q000528:radiation effects*; D005260:Female; D006657:Histones / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008214:Lymphocytes / Q000473:pathology* / Q000528:radiation effects*; D008875:Middle Aged; D009336:Necrosis; D009367:Neoplasm Staging; D010766:Phosphorylation / Q000528:radiation effects; D000071857:Tumor Suppressor p53-Binding Protein 1
chemical_list: C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1
keywords: 53BP1; apoptosis; breast cancer; individual radiosensitivity; necrosis; radiotherapy; side-effects; γH2AX