STAT5A and liver cancer: Further research in liver cancer cells has identified STAT5 target genes, which include Nox4, a reactive oxygen species (ROS) enzyme, and pro-apoptotic proteins p53 up-regulated modulator of apoptosis (PUMA) and Bcl-2-interacting mediator of cell death (Bim), and STAT5 up-regulates the genes encoding these proteins [18].