HO-1 gene expression is regulated by different transcription factors such as Nrf2, AP-1, HSF1, and NF-κB. These transcription factors are activated by a variety of MAPKs, in response to different stimuli. As a result, HO-1 is expressed, and its overexpression may result in a variety of malignancies as indicated. [Adapted from Alam and Cook (2)]. MAPKs, mitogen-activated protein kinases. Color images are available online.