Co-culturing with High-Charge and Energy Particle Irradiated Cells Increases Mutagenic Joining of Enzymatically Induced DNA Double-Strand Breaks in Nonirradiated Cells.
Cell populations that have been exposed to high-charge and energy (HZE) particle radiation, and then challenged by expression of a rare-cutting nuclease, show an increased frequency of deletions and translocations originating at the enzyme cut sites. Here, we examine whether this effect also occurs in nonirradiated cells that have been co-cultured with irradiated cells. Human cells were irradiated with 0.3-1.0 Gy of either 600 MeV/u (56)Fe or 1,000 MeV/u (48)Ti ions or with 0.3-3.0 Gy of 320 kV X rays. These were co-cultured with I-SceI-expressing reporter cells at intervals up to 21 days postirradiation. Co-culture with HZE-irradiated cells led to an increase in the frequency of I-SceI-stimulated translocations and deletions in the nonirradiated cells. The effect size was similar to that seen previously in directly irradiated populations (maximum effect in bystander cells of 1.7- to 4-fold depending on ion and end point). The effect was not observed when X-ray-irradiated cells were co-cultured with nonirradiated cells, but was correlated with an increase in γ-H2AX foci-positive cells in the nonirradiated population, suggesting the presence of genomic stress. Transcriptional profiling of a directly irradiated cell population showed that many genes for cytokines and other secretory proteins were persistently upregulated, but their induction was not well correlated with functional effects on repair in co-cultured cells, suggesting that this transcriptional response alone is not sufficient to evoke the effect. The finding that HZE-irradiated cells influence the DNA double-strand break repair fidelity in their nonirradiated neighbors has implications for risk in the space radiation environment.
a  Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia.|d  The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, P. R. China.|f  Department of Neuroscience and Regenerative Medicine, Georgia Regents University, Augusta, Georgia.
Zhentian
Z
Li
b  Department of Emory Integrated Genomics Core, Emory University, Atlanta, Georgia.
Gregory
G
Doho
e  Zhongnan Hospital, Wuhan University, Wuhan, P. R. China.
Xuan
X
Zheng
a  Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia.
Kishore Kumar
KK
Jella
a  Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia.|c  Department of Biochemistry, Emory University, Atlanta, Georgia.
Shuyi
S
Li
a  Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia.
Ya
Y
Wang
a  Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia.|c  Department of Biochemistry, Emory University, Atlanta, Georgia.
William S
WS
Dynan
D024201:Bystander Effect; D045744:Cell Line, Tumor; D018920:Coculture Techniques; D003359:Cosmic Radiation; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004260:DNA Repair; D020869:Gene Expression Profiling; D006801:Humans; D009154:Mutation