Figure 2

Bivariate distributions (DNA content vs. γH2AX) of CCC cell lines, OVISE and RMG-I, treated with CDDP (Upper, OVISE; Lower, RMG-I). The dotted lines indicate the upper level of γH2AX immunofluorescence for 95% of cells in the untreated (control) culture. Arrow heads indicate elevation of γH2AX that means DNA damage. Arrows indicate apoptotic cell populations with marked increase in γH2AX and gradual decrease in DNA. (A) Both cell lines treated with various concentrations of CDDP for 24 h. OVISE and RMG-1 cell lines exhibited DNA damage in S-phase cells at minimum concentrations of 100 ng/ml and 1 μg/ml, respectively. Both cell lines were subjected to DNA damage concentration-dependently at every cell cycle, and apoptosis was induced at concentrations of 5 μg/ml or higher. More cells in RMG-1 remained free of DNA damage as compared to OVISE. (B) Both cell lines were treated with 100 ng/ml, the minimum concentration inducing DNA damage in either cell line, for various reaction times. S-phase cells of OVISE showing DNA damage progressed to apoptosis after 48 h. In addition, S-phase arrest was observed. DNA damage was induced in S-phase cells of RMG-I after 48 h. Cells with DNA damage progressed to apoptosis after 72 h. Furthermore, cell-cycle arrest occurred in all cells.