In most cancers, ROS activates pro-tumorigenic signaling pathways, such as PI3K/AKT, MAPK/ERK, and HIF-1α, and this is often associated with the inactivation of negative regulators for these pathways, such as PTEN, MAPK phosphatase, and PHD-2, which also promote proliferation, survival, and metastasis. Here, HIF1A is linked to cancer.