Ruthenium complexes increased the radiosensitivity of pancreatic cancer cells. (A) PANC 1 cells were treated with 500 nmol Ru-SR1# or Ru-SR3# for 24 h and then were exposed to 2, 4 or 6 Gy of X-ray. The cells were cultured at 37 °C for additional 10 d, and the number of colonies consisting of 50 or more cells was counted under a microscopy. (B) Clonogenic survival curve of PANC 1 cells treatment with Ru-SR1# or Ru-SR3# and X-ray irradiation were plotted and the values of D0, Dq, and SER were calculated using GraphPad Prism software (Table 2). (C) PANC 1 cells were treated with 500 nmol Ru-SR3#, 4 Gy X-ray, or Ru-SR3# plus X-ray. After 24 h, the cells were collected for DNA double strand breaks (DSBs) analysis using neutral single cell gel electrophoresis (SCGE). For each treatment, 100 cells were randomly chosen and photographed under a confocal microscopy. (D) The extent of DSBs in each treatment group was analyzed using Comet Assay Software Project (CASP), which was presented as the Tail DNA%, Tail Moment, and Olive Tail Moment. *, compared to control group, P<0.05. (E) After 0.5 h exposure to 2Gy X-Ray, the foci number of γ-H2AX in PANC 1 cells pretreated with 500 nmol Ru-SR3# was significantly more than that of the control group. All experiments mentioned above were performed at least three times.