RTX increases the dUTP:dTTP ratio in HT29 cells. (A) HT29 cells were pulse treated with RTX for 6 h. dUTP and dTTP levels were determined using an SNE assay (n = 3). (B) Pulse treatment with RTX has a time-dependent increase in the dUTP:dTTP ratio. After pulse treatment with 50 nM RTX, HT29 cells were incubated for 0, 4, 10, 28, or 52 h after a washout with PBS. dUTP and dTTP levels were determined at each time point, and the dUTP:dTTP ratio was calculated (n = 3; Materials and Methods).