On the other hand, oxidative protein folding (disulfide bond formation) in the ER, results in the release of ROS as a by-product, which can then be used to activate a variety of transcription factors including NF-κB, AP-1, p53, HIF-1α, PPAR-γ, β-catenin/Wnt, and Nrf2 to help cancer cells maintain their high proliferation rate [17,18]. This evidence concerns the gene TP53 and cancer.