Inhibitory effects of I3C and genistein on cell viability in human colon cancer HT-29 cells. A, Viability of HT-29 cells 48 h after exposure to increasing doses of I3C or genistein as indicated. B, Time-dependent viability of HT-29 cells not treated (black circle) or treated with DMSO (black triangle), I3C (300 μmol/L) (black square), genistein (40 μmol/L) (black triangle), or a combination of I3C (300 μmol/L) and genistein (40 μmol/L) (white circle) for up to 2 days. The cell viability assay was performed as described in Materials and Methods. Columns and points, mean (n = 3); bars, SD. *, P < 0.05, significantly different compared with the DMSO-treated control. GEN, genistein. C, HT-29 cells were exposed to increasing concentrations of I3C and genistein, either alone or in a fixed ratio of 7.5:1, for 48 h, as described in Materials and Methods. The Fa-CI plot was constructed using experimental data points (dark circles) and by simulating CI values over the entire range of Fa values (line) using CalcuSyn software. Synergy, additivity, and antagonism are defined as CI<1, CI = 1, and CI>1, respectively.