Induction of DNA double-strand breaks and cellular migration through bystander effects in cells irradiated with the slit-type microplanar beam of the spring-8 synchrotron.
OBJECTIVE
To determine whether glioma cells irradiated with a microplanar X-ray beam exert bystander effects.


METHODS
Microplanar beam irradiation of glioma cells in vitro was done using the SPring-8 synchrotron radiation facility. The amount of DNA double-strand breaks (dsbs) was measured by the fluorescence intensity of phosphorylated H2AX or the number of 53BP1 foci. The dose distribution in a cell population exposed to a single microplanar beam was determined by the amount of phosphorylated H2AX-positive cells. Bystander effects were determined by counting the number of 53BP1 foci in nonirradiated cells treated with conditioned medium from cultures of irradiated cells.


RESULTS
More DNA dsbs were detected in cells adjacent to an area irradiated by the single beam than in cells in distant, nonirradiated areas as a result of bystander effects caused by scattered X-rays and DNA dsbs. In support of this, more 53BP1 foci were observed in nonirradiated, conditioned medium-treated cells than in control cells (i.e., cells not treated with irradiation or conditioned medium). These results suggest that DNA dsbs were induced in nonirradiated cells by soluble factors in the culture medium. In addition, we observed cellular migration into areas irradiated with peak doses, suggesting that irradiated cells send signals that cause nonirradiated cells to migrate toward damaged cells.


CONCLUSIONS
Bystander effects are produced by factors secreted as a result of slit-type microplanar X-ray beam irradiation.
Research Reactor Institute, Kyoto University, Osaka, Japan.
Genro
G
Kashino
Takeshi
T
Kondoh
Nobuteru
N
Nariyama
Keiji
K
Umetani
Takuji
T
Ohigashi
Kunio
K
Shinohara
Ai
A
Kurihara
Manabu
M
Fukumoto
Hiroki
H
Tanaka
Akira
A
Maruhashi
Minoru
M
Suzuki
Yuko
Y
Kinashi
Yong
Y
Liu
Shin-Ichiro
S
Masunaga
Masami
M
Watanabe
Koji
K
Ono
D000818:Animals; D024201:Bystander Effect; D002465:Cell Movement; D017077:Culture Media, Conditioned; D053903:DNA Breaks, Double-Stranded; D005910:Glioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D006657:Histones / Q000032:analysis / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis / Q000378:metabolism; D009363:Neoplasm Proteins / Q000032:analysis* / Q000378:metabolism; D011879:Radiotherapy Dosage; D051381:Rats; D017356:Synchrotrons; D014407:Tumor Cells, Cultured; D000071857:Tumor Suppressor p53-Binding Protein 1
D017077:Culture Media, Conditioned; C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1