A laser-plasma-produced soft X-ray laser at 89 eV generates DNA double-strand breaks in human cancer cells

While it has been expected that x-ray laser will be widely applied to biomedical studies,this has not been achieved to date and its biological effects such as dna damage have not been evaluated. as a first step for its biological application,we developed a culture cell irradiation system,particularly designed for a plasma-driven soft x-ray laser pulse,to investigate whether the soft x-ray laser is able to induce dna double strand breaks (dsbs) in living cells or not. the human adenocarcimona cell line a549 was irradiated with the soft x-ray laser at a photon energy of 89 ev and the repair focus formation of the dsbs was assessed by immunofluorescence staining with antiphosphorylated dna-pkcs (p-dna-pkcs),atm (p-atm) and γ-h2ax antibody. the p-dna-pkcs,atm,and γ-h2ax foci were clearly identified after soft x-ray laser irradiation. furthermore,the increase in the x-ray laser shot number,even from a single shot,results in the increase in p-dna-pkcs foci. these results are the first evidence that the 89 ev soft x-ray laser is able to induce dsb in living cells. our study demonstrated that this irradiation system is a useful tool for investigating the radiobiological effect of soft x-ray laser. © the author 2015.