Effect of I3C in the presence or absence of putrescine on progression of SW480 cells through the cell cycle. A) Cells were treated for 96 hours as indicated, and stained with propidium iodide before analysis by flow cytometry as described in Materials and Methods. Control = DMSO treated cells, C+P = DMSO plus putrescine (50 μM), I3C = I3C (175 μM) and I+P = I3C (175 μM) plus putrescine, DFMO = DFMO (50 μM). * indicates a significant difference from control levels (P < 0.05; n = 8; pooled SD = 3.54). B) Cells were synchronised with nocodazole for 24 hr (Noc (24 hr)) and then released into control (Con +32 hr), I3C (I3C +32 hr) or I+P (I+P +32 hr) treated medium and analysed as described in Materials and Methods. Data from the +32 hr time point is shown. Control = DMSO treated, non-synchronised cells. * indicates a significant difference from the Con +32 hr value for each phase of the cell cycle (P < 0.05; n = 4; pooled SD = 2.61).