Induction of apoptosis or necrosis in SW480 cells by I3C in the presence or absence of putrescine. Cells were treated for 96 hours and then harvested and stained for phosphatidylserine externalisation and propidium iodide incorporation before analysis by flow cytometry as described in Materials and Methods. Control = DMSO treated cells, C+P = DMSO plus putrescine (50 μM), I175, I250, I500 = I3C (at the given concentration) and I+P = I3C (175 μM) plus putrescine. Significant difference from control is indicated by a, and between the I3C 175 μM and I3C + putrescine treatment by b (P < 0.05). Results are displayed as means (n = 12), pooled SD = 6.08.