In addition to breast cancer12, the PAK4 gene was shown to be amplified in a number of different cancer types, including pancreatic cancer17, 24, 25, squamous cell carcinomas26, esophageal squamous cell carcinoma (ESCC)31, endometrioid tumors, ovarian tumors and cell lines20, as well as prostate cancer28. Here, PAK4 is linked to esophageal squamous cell carcinoma.