The accumulating evidence demonstrated that certain cancer-derived mutant forms of p53 transactivate various target genes such as the multiple drug resistance gene 1 (MDR1), c-myc, proliferating cell nuclear antigen (PCNA), interleukin-6 (IL-6), insulin-like growth factor 1 (IGF-1), fibroblast growth factor (FGF) and epidermal growth factor receptor (EGFR) [39-45]. Here, PCNA is linked to cancer.