Proliferation of SW620 cells treated with GTA+ve and GTA-ve extracts. (A) SW620 cells were incubated with increasing concentrations of GTA+ve and GTA-ve extracts for 24 hours and proliferation assayed by MTT. (B) The 80 ug/ml concentration of GTA+ve and GTA-ve extracts was then used to treat cells for up to 48 hours and the effect on cell proliferation assayed by MTT. Data are expressed as percent of vehicle or 0 hrs ± 1S.D. (C) Representative Western blot analysis of caspase-mediated PARP cleavage fragments resulting from treatment with GTA+ve and -ve extracts. Experiments were repeated at least three times.