TY  - JOUR
A1  - Eberlein, Uta
A1  - Peper, Michel
A1  - Fernández, Maria
A1  - Lassmann, Michael
A1  - Scherthan, Harry
T1  - Calibration of the \(\gamma\)-H2AX DNA double strand break focus assay for internal radiation exposure of blood lymphocytes
JF  - PLoS ONE
N2  - DNA double strand break (DSB) formation induced by ionizing radiation exposure is indicated by the DSB biomarkers \(\gamma\)-H2AX and 53BP1. Knowledge about DSB foci formation in-vitro after internal irradiation of whole blood samples with radionuclides in solution will help us to gain detailed insights about dose-response relationships in patients after molecular radiotherapy (MRT). Therefore, we studied the induction of radiation-induced co-localizing \(\gamma\)-H2AX and 53BP1 foci as surrogate markers for DSBs in-vitro, and correlated the obtained foci per cell values with the in-vitro absorbed doses to the blood for the two most frequently used radionuclides in MRT (I-131 and Lu-177). This approach led to an in-vitro calibration curve. Overall, 55 blood samples of three healthy volunteers were analyzed. For each experiment several vials containing a mixture of whole blood and radioactive solutions with different concentrations of isotonic NaCl-diluted radionuclides with known activities were prepared. Leukocytes were recovered by density centrifugation after incubation and constant blending for 1 h at 37°C. After ethanol fixation they were subjected to two-color immunofluorescence staining and the average frequencies of the co-localizing \(\gamma\)-H2AX and 53BP1 foci/nucleus were determined using a fluorescence microscope equipped with a red/green double band pass filter. The exact activity was determined in parallel in each blood sample by calibrated germanium detector measurements. The absorbed dose rates to the blood per nuclear disintegrations occurring in 1 ml of blood were calculated for both isotopes by a Monte Carlo simulation. The measured blood doses in our samples ranged from 6 to 95 mGy. A linear relationship was found between the number of DSB-marking foci/nucleus and the absorbed dose to the blood for both radionuclides studied. There were only minor nuclide-specific intra-and inter-subject deviations.
KW  - in vivo formation
KW  - chromatin mobility
KW  - phosphorylation
KW  - repair
KW  - 53BP1
KW  - damage
KW  - radioiodine therapy
KW  - thyroid cancer
KW  - histone H2AX
KW  - dose response
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148697
VL  - 10
IS  - 4
ER  - 
TY  - JOUR
A1  - Kroeber, Jana
A1  - Wenger, Barbara
A1  - Schwegler, Manuela
A1  - Daniel, Christoph
A1  - Schmidt, Manfred
A1  - Djuzenova, Cholpon S
A1  - Polat, Bülent
A1  - Flentje, Michael
A1  - Fietkau, Rainer
A1  - Distel, Luitpold V.
T1  - Distinct increased outliers among 136 rectal cancer patients assessed by \(\gamma\)H2AX
JF  - Radiation Oncology
N2  - Background: 
In recent years attention has focused on \(\gamma\)H2AX as a very sensitive double strand break indicator. It has been suggested that \(\gamma\)H2AX might be able to predict individual radiosensitivity. Our aim was to study the induction and repair of DNA double strand breaks labelled by \(\gamma\)H2AX in a large cohort. 

Methods: 
In a prospective study lymphocytes of 136 rectal cancer (RC) patients and 59 healthy individuals were ex vivo irradiated (IR) and initial DNA damage was compared to remaining DNA damage after 2 Gy and 24 hours repair time and preexisting DNA damage in unirradiated lymphocytes. Lymphocytes were immunostained with anti-\(\gamma\)H2AX antibodies and microscopic images with an extended depth of field were acquired. \(\gamma\)H2AX foci counting was performed using a semi-automatic image analysis software. 

Results: 
Distinct increased values of preexisting and remaining \(\gamma\)H2AX foci in the group of RC patients were found compared to the healthy individuals. Additionally there are clear differences within the groups and there are outliers in about 12% of the RC patients after ex vivo IR. 

Conclusions: 
The \(\gamma\)H2AX assay has the capability to identify a group of outliers which are most probably patients with increased radiosensitivity having the highest risk of suffering radiotherapy-related late sequelae.
KW  - histone H2AX
KW  - blood lymphocytes
KW  - in vivo
KW  - foci
KW  - individual radiosensitivity
KW  - rectal cancer
KW  - radiotherapy
KW  - DNA double strand breaks
KW  - phosphorylation
KW  - neck cancer
KW  - oral mucositis
KW  - DNA damage
KW  - radiosensitivity
KW  - repair
KW  - \(\gamma\)h2ax
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-144085
VL  - 10
IS  - 36
ER  -