Fig. 2

Cytotoxicity and TK mutant frequency in WT TK+/- and KO TK+/- cells treated with MMC. a Relative survival and (b) TK mutant frequency. Open and closed circles indicate the results in WT TK+/- and KO TK+/- cells, respectively. Each data point is the mean value of four independent experiments, and error bars indicate standard error. * denotes the statistical significance compared to WT TK+/- cells treated the same concentration (P < 0.05)