Induction and rejoining of DNA double strand breaks assessed by H2AX phosphorylation in melanoma cells irradiated with proton and lithium beams.
OBJECTIVE
The aim of this study was to evaluate the induction and rejoining of DNA double strand breaks (DSBs) in melanoma cells exposed to low and high linear energy transfer (LET) radiation.


METHODS
DSBs and survival were determined as a function of dose in melanoma cells (B16-F0) irradiated with monoenergetic proton and lithium beams and with a gamma source. Survival curves were obtained by clonogenic assay and fitted to the linear-quadratic model. DSBs were evaluated by the detection of phosphorylated histone H2AX (gammaH2AX) foci at 30 min and 6 h post-irradiation.


RESULTS
Survival curves showed the increasing effectiveness of radiation as a function of LET. gammaH2AX labeling showed an increase in the number of foci vs. dose for all the radiations evaluated. A decrease in the number of foci was found at 6 h post-irradiation for low LET radiation, revealing the repair capacity of DSBs. An increase in the size of gammaH2AX foci in cells irradiated with lithium beams was found, as compared with gamma and proton irradiations, which could be attributed to the clusters of DSBs induced by high LET radiation. Foci size increased at 6 h post-irradiation for lithium and proton irradiations in relation with persistent DSBs, showing a correlation with surviving fraction.


CONCLUSIONS
Our results showed the response of B16-F0 cells to charged particle beams evaluated by the detection of gammaH2AX foci. We conclude that gammaH2AX foci size is an accurate parameter to correlate the rejoining of DSBs induced by different LET radiations and radiosensitivity.
Ibañez
Irene L
IL
Comisión Nacional de Energía Atómica, San Martín, Argentina.
Bracalente
Candelaria
C
Molinari
Beatriz L
BL
Palmieri
Mónica A
MA
Policastro
Lucía
L
Kreiner
Andrés J
AJ
Burlón
Alejandro A
AA
Valda
Alejandro
A
Navalesi
Daniela
D
Davidson
Jorge
J
Davidson
Miguel
M
Vázquez
Mónica
M
Ozafrán
Mabel
M
Durán
Hebe
H
D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D002470:Cell Survival; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D006657:Histones / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D018499:Linear Energy Transfer; D008094:Lithium / Q000627:therapeutic use; D008546:Melanoma, Experimental / Q000235:genetics / Q000378:metabolism / Q000532:radiotherapy*; D010766:Phosphorylation; D061766:Proton Therapy; D011836:Radiation Tolerance; D011868:Radioisotopes / Q000627:therapeutic use
D015415:Biomarkers; C468783:H2AX protein, human; D006657:Histones; D011868:Radioisotopes; D008094:Lithium