PCNA and malignant colon neoplasm: In colon cancer, human colon cancer HCT-15 cells treated various concentrations of Timo AIII for 12 or 24 h appeared different degree of G0/G1 and G2/M phase cell cycle arrest, and the cell cycle regulation effect of Timo AIII was associated with the down-regulation of cyclin A, cyclin B1, CDK2, CDK4, pRb, proliferating cell nuclear antigen (PCNA) and c-Myc (Kang et al., 2011).