PCNA and neoplasm: Previous studies have shown that KLTi promoted tumor cell apoptosis by upregulating the expression of the p53 and FAS genes, as well as Caspase-3, proliferating-cell nuclear antigen (PCNA), and p21WAFI/CIPI, and by downregulating the expression of the cyclin A, cyclin E1, and cyclin F coding genes [27].