DNA double-strand break repair and induction of apoptosis in ex vivo irradiated blood lymphocytes in relation to late normal tissue reactions following breast radiotherapy
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DNA double-strand break repair and induction of apoptosis in ex vivo irradiated blood lymphocytes in relation to late normal tissue reactions following breast radiotherapy. / Chua, Melvin Lee Kiang; Horn, Simon; Somaiah, Navita; Davies, Sue; Gothard, Lone; A'Hern, Roger; Yarnold, John; Rothkamm, Kai.
in: RADIAT ENVIRON BIOPH, Jahrgang 53, Nr. 2, 05.2014, S. 355-64.Publikationen: SCORING: Beitrag in Fachzeitschrift/Zeitung › SCORING: Zeitschriftenaufsatz › Forschung › Begutachtung
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TY - JOUR
T1 - DNA double-strand break repair and induction of apoptosis in ex vivo irradiated blood lymphocytes in relation to late normal tissue reactions following breast radiotherapy
AU - Chua, Melvin Lee Kiang
AU - Horn, Simon
AU - Somaiah, Navita
AU - Davies, Sue
AU - Gothard, Lone
AU - A'Hern, Roger
AU - Yarnold, John
AU - Rothkamm, Kai
PY - 2014/5
Y1 - 2014/5
N2 - This study aimed to test whether induction of apoptosis following ex vivo X-irradiation of unstimulated blood lymphocytes correlated with clinical radiosensitivity and DNA double-strand break (DSB) repair in breast radiotherapy patients and healthy volunteers. Using small molecule inhibitors, the relationship between DSB repair and radiation-induced apoptosis was examined. Sixteen breast cancer patients with minimal (controls, n = 8) or extremely marked late radiation-induced change (cases, n = 8) and eight healthy volunteers were selected. DSBs were quantified by γH2AX/53BP1 immunofluorescence, and apoptosis was measured using a fluorogenic inhibitor of caspases assay. Mean γH2AX/53BP1 focus levels 24 h after exposure to 4 Gy were higher in cases (12.7 foci per cell) than in controls (10.3 foci per cell, p = 0.002). In contrast, the mean apoptotic fraction 48 h after 8 Gy was comparable, 37.2 % in cases and 34.7 % in controls (p = 0.442). Residual focus and apoptosis levels were not correlated within individuals (Spearman's R = -0.0059, p = 0.785). However, cells treated with DNA-PK inhibitor Nu7441 had higher focus and apoptosis levels 48 h after 1 Gy compared to mock-treated cells, suggesting that apoptosis induction following irradiation is modulated by DSB repair. This effect required functional ATM since cells treated simultaneously with Nu7441 and the ATM inhibitor Ku55933 were resistant to apoptosis despite high levels of residual foci. One clinical case displayed an impaired DNA-PK-dependent end-joining cellular phenotype. In summary, clinical radiosensitivity may be associated with impaired DSB repair in some patients. Although pharmaceutical inhibition of ATM and DNA-PK affected apoptosis induction and DSB repair, no association was observed between apoptosis and residual focus levels in patients and volunteers.
AB - This study aimed to test whether induction of apoptosis following ex vivo X-irradiation of unstimulated blood lymphocytes correlated with clinical radiosensitivity and DNA double-strand break (DSB) repair in breast radiotherapy patients and healthy volunteers. Using small molecule inhibitors, the relationship between DSB repair and radiation-induced apoptosis was examined. Sixteen breast cancer patients with minimal (controls, n = 8) or extremely marked late radiation-induced change (cases, n = 8) and eight healthy volunteers were selected. DSBs were quantified by γH2AX/53BP1 immunofluorescence, and apoptosis was measured using a fluorogenic inhibitor of caspases assay. Mean γH2AX/53BP1 focus levels 24 h after exposure to 4 Gy were higher in cases (12.7 foci per cell) than in controls (10.3 foci per cell, p = 0.002). In contrast, the mean apoptotic fraction 48 h after 8 Gy was comparable, 37.2 % in cases and 34.7 % in controls (p = 0.442). Residual focus and apoptosis levels were not correlated within individuals (Spearman's R = -0.0059, p = 0.785). However, cells treated with DNA-PK inhibitor Nu7441 had higher focus and apoptosis levels 48 h after 1 Gy compared to mock-treated cells, suggesting that apoptosis induction following irradiation is modulated by DSB repair. This effect required functional ATM since cells treated simultaneously with Nu7441 and the ATM inhibitor Ku55933 were resistant to apoptosis despite high levels of residual foci. One clinical case displayed an impaired DNA-PK-dependent end-joining cellular phenotype. In summary, clinical radiosensitivity may be associated with impaired DSB repair in some patients. Although pharmaceutical inhibition of ATM and DNA-PK affected apoptosis induction and DSB repair, no association was observed between apoptosis and residual focus levels in patients and volunteers.
KW - Adult
KW - Aged
KW - Apoptosis/drug effects
KW - Ataxia Telangiectasia Mutated Proteins/antagonists & inhibitors
KW - Breast Neoplasms/radiotherapy
KW - Case-Control Studies
KW - Chromones/pharmacology
KW - DNA Breaks, Double-Stranded/drug effects
KW - DNA Repair/drug effects
KW - DNA-Activated Protein Kinase/antagonists & inhibitors
KW - Enzyme Activation/drug effects
KW - Female
KW - Histones/metabolism
KW - Humans
KW - Intracellular Signaling Peptides and Proteins/metabolism
KW - Lymphocytes/cytology
KW - Middle Aged
KW - Morpholines/pharmacology
KW - Nuclear Proteins/antagonists & inhibitors
KW - Organs at Risk/radiation effects
KW - Protein Kinase Inhibitors/pharmacology
KW - Pyrones/pharmacology
KW - Radiation Injuries/genetics
KW - Radiation Tolerance/drug effects
KW - Time Factors
KW - Tumor Suppressor p53-Binding Protein 1
U2 - 10.1007/s00411-014-0531-z
DO - 10.1007/s00411-014-0531-z
M3 - SCORING: Journal article
C2 - 24622963
VL - 53
SP - 355
EP - 364
JO - RADIAT ENVIRON BIOPH
JF - RADIAT ENVIRON BIOPH
SN - 0301-634X
IS - 2
ER -