Effect of nocodazole treatment on cell cycle profile in human colorectal cell lines. Log phase culture of wild-type (p21+/+) or p21 null (p21−/−) cells were treated with the indicated amount of nocodazole for 24 hours and then cell cycle analysis was performed. 2N(G0/G1), 4N(G2/M), and 8N(polyploid) DNA contents are shown (data are representative of 3 separate experiments).