Mechanistic studies of KLT showed that KLT could inhibit cell growth and induce apoptosis by upregulating the expressions of p53, Fas, caspase-3, proliferating cell nuclear antigen (PCNA), and P21WAFI/CIPI, while downregulating the expressions of cyclins A, E1, and F in cancer cells (Wang et al., 1999; Guo et al., 2001; Li and Shi, 2002; Bao et al., 2004; Yuan et al., 2004). Here, PCNA is linked to cancer.