Since it is reported that a natural plant product curcumin can induce a similar G2/M arrest in human colorectal cancer lines HCT-116 (p53+/+), HCT-116 (p53−/−), and HCT-116 (p21−/−) by regulating cdc2/cyclin B1 kinase activity [32], we investigated the expression of cyclin B1 and phosphorylated-cdc2 (Tyr15) in A549 cells treated with C1. The gene discussed is TP53; the disease is colorectal cancer.