It is reported that PAK4 acts as upstream regulators of p53, and significantly reduces camptothecin-induced phospho-S474-PAK4 and p53 levels.14 However, downregulation of PAK4 causes S phase arrest and is associated with the upregulation of p53 in Hep-2 laryngeal carcinoma cells.28 Thus, further definition and mapping of the link between PAK4 and p53 signaling may have important implications in the treatment of PAK4-related cancers. This evidence concerns the gene TP53 and cancer.