Fig. 2.

Dose-dependent effects of 1-benzyl-I3C and I3C on the DNA synthesis of human MCF-7 breast cancer cells. (A) Triplicate samples of asynchronously growing human MCF-7 breast cancer cells were treated with increasing concentrations of 1-benzyl-I3C, I3C or the vehicle control (DMSO) for 72 hours. During the last three hours, cells were pulsed with 3 μCi [³H]thymidine (84 Ci/mmol), and the incorporation into DNA was determined by acid precipitation as described in the Materials and Methods section. Triplicates were averaged and expressed as counts per minute per well. (B) To determine the IC₅₀ values of the I3C and 1-benzyl-I3C inhibition of DNA synthesis of MCF-7 cells, the results of the [³H]thymidine incorporation data are plotted as the percentage of vehicle control treated cells for each indole. Data are the mean of three experiments; bars, +/-SE.