GPA33 and colonic neoplasm: KLF4 is a nodal player in the network of PPARγ-regulated genes, and treatment of colon cancer cells with PPARγ agonists influences KLF4 target genes, whose expression is decreased (cyclin D1) or increased (GPA33, encoding the glycoprotein A33 that is a colon cancer antigen, p21WAF1/Cip1, and keratin 19), respectively [38].